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GeckoSub Mirage Evo - And Adventures in 3D Printing Speargun Parts
- Thread starter Diving Gecko
- Start date
It's Not All Black and White, well Black and Green... (Thoughts on O-ring Materials)
I do know the green FKM ones are mostly intended for use in higher temperature settings and have better chemical resistance. But honestly, most of my green ones were bought when it was the only type I could find in the size I needed at the time.
As for the good and bad of each kind, I've looked into but it's a frustrating because some sources say FKM has a bit more wear resistance than NBR and some say the opposite. As for friction, it's hard to find a clear answer, too. What seems certain is that FKM (green) have less elasticity which I think could explain your findings. I also think they are often a little harder.
I don't think I have used them on pistons - can't remember - but I have certainly used them on main, static seals like the nose cones and handles and no issues there.
So, if used on a valve, since FKM has less elasticity and supposedly less elastic recovery, it might wear out faster from the cycles of expansion and contraction.
On a piston, if FKM is a bit harder it may also be more brittle and wear out faster (which ChatGPT seems to think, but it can't point me to the direct source). And if it's harder/stiffer and if it has more friction I can see it how it could get twisted.
Either way, I trust your real world findings. And I think the general rule is to use NBR (especially dynamic) unless you really need higher temp or chemical resistance - which we don't
.I actually tried yesterday with some black rings, too. But the black ones I have in this size are actually a bit undersized and not to spec which is why I went for the green ones so that at least I could check that the geometry of the groove would work:
But I will order some better NBR rings in this size and not use the green rings for anything dynamic. Thanks.
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Making A New Pumping Barrel
I mentioned yesterday that I wanted to make a better jig for holding the pumping barrel when I had to use the CNC.
So, I did and I made it work for a few more things:
The hardware is linear guide rod clamps - I've used these before but this time I put three sets on a plastic block. The left set has a bore of 12mm which works for the new, smaller pumping barrels. The set in the middle is 8mm as I may make some slip tips in the future that would need a slot milled into them and the right set is 16mm but they will be enlarged later on to hold 18mm shooting barrels. I will need this when I modify the transfer bores and cut out for the trigger sear.
I've wanted a jig like this for years, so it's cool to finally have it. Will make setup time and modifications faster and easier in the future.
The new jig worked as intended - it made drilling the vent holes in the pumping barrel much easier:
Also, since I am not just hand holding the barrel as I was before, the drill bit survived just fine even though it's a tiny 0.8mm drill (down from 0.9mm in the last attempt). I drilled six holes and the blue marker shows their approximate location. And then I just turn the barrel to line up each mark and then drill.
This time, I drilled the holes before I made the groove on the lathe but I think both methods work equally well. No pics of the finished groove but it looks like in the post from yesterday.
The front part of the pumping barrel got two o-ring grooves but no pix of that, either. It was easy once I had made sure to tripple check how long the barrel needed to be.
Finally, I cut two new o-ring grooves at the front of the shooting barrel as the new reservoir is a bit longer so the nose cone sits further forward on the barrel:
Weight Savings Tally
As for the weight saving quest, we are saving ~42g on the new nose cone:
And about 122g by switching to the CF reservoir:
That's 164g saved in total but I am also gaining a bit of buoyancy as the new reservoir is 47mm longer than the old one.
(The highlighted green part shows the volume gained ):
That volume equals a ~38g weight saving so in total we have "saved" 202g which is quite substantial and will probably get me really close to neutral.
But since I'd like to add a reel, I may cut down the OD of the pumping barrel, too to save a bit more which is something I'd wanted to try for a long time.
I did a quick test on the "old" pumping barrel - the one I just replaced:
Original OD is 13mm, the reduced OD is 12mm which leaves me with a 1mm wall thickness. If I turn the whole pumping barrel down like this, apart from the very ends, I will save another 30-35g.
The only downside is cosmetic. I don't have a follower rest so I have to take these cuts a bit at a time. So, turn down maybe 50-70mm of tube, then open the chuck and pull the tube out another 50-70mm to cut some more and keep repeating until the whole tube is done. But every time I open the 3-jaw chuck, the tube will shift a little "sideways" so there will be a bit of a step in between all the cuts. But it's cosmetic only and will be hidden inside my personal gun, so I think I can survive that.
And I think the ~30g is worth the effort so will get that done tomorrow and then I can assemble the gun.
Any additional weight savings would have to come from also turning down the OD of the shooting barrel but I am not sure I am ready for that as it's the main structural part holding the whole gun together. Apart from that the only ways to save some weight would be to make a new version of the nose cone, but I can only save another 8g or so there and then perhaps the same for a new bulkhead which isn't really worth the work right now. I do have an idea for making the reel itself lighter but we will see I get around to that.
I mentioned yesterday that I wanted to make a better jig for holding the pumping barrel when I had to use the CNC.
So, I did and I made it work for a few more things:
The hardware is linear guide rod clamps - I've used these before but this time I put three sets on a plastic block. The left set has a bore of 12mm which works for the new, smaller pumping barrels. The set in the middle is 8mm as I may make some slip tips in the future that would need a slot milled into them and the right set is 16mm but they will be enlarged later on to hold 18mm shooting barrels. I will need this when I modify the transfer bores and cut out for the trigger sear.
I've wanted a jig like this for years, so it's cool to finally have it. Will make setup time and modifications faster and easier in the future.
The new jig worked as intended - it made drilling the vent holes in the pumping barrel much easier:
Also, since I am not just hand holding the barrel as I was before, the drill bit survived just fine even though it's a tiny 0.8mm drill (down from 0.9mm in the last attempt). I drilled six holes and the blue marker shows their approximate location. And then I just turn the barrel to line up each mark and then drill.
This time, I drilled the holes before I made the groove on the lathe but I think both methods work equally well. No pics of the finished groove but it looks like in the post from yesterday.
The front part of the pumping barrel got two o-ring grooves but no pix of that, either. It was easy once I had made sure to tripple check how long the barrel needed to be.
Finally, I cut two new o-ring grooves at the front of the shooting barrel as the new reservoir is a bit longer so the nose cone sits further forward on the barrel:
Weight Savings Tally
As for the weight saving quest, we are saving ~42g on the new nose cone:
And about 122g by switching to the CF reservoir:
That's 164g saved in total but I am also gaining a bit of buoyancy as the new reservoir is 47mm longer than the old one.
(The highlighted green part shows the volume gained ):
That volume equals a ~38g weight saving so in total we have "saved" 202g which is quite substantial and will probably get me really close to neutral.
But since I'd like to add a reel, I may cut down the OD of the pumping barrel, too to save a bit more which is something I'd wanted to try for a long time.
I did a quick test on the "old" pumping barrel - the one I just replaced:
Original OD is 13mm, the reduced OD is 12mm which leaves me with a 1mm wall thickness. If I turn the whole pumping barrel down like this, apart from the very ends, I will save another 30-35g.
The only downside is cosmetic. I don't have a follower rest so I have to take these cuts a bit at a time. So, turn down maybe 50-70mm of tube, then open the chuck and pull the tube out another 50-70mm to cut some more and keep repeating until the whole tube is done. But every time I open the 3-jaw chuck, the tube will shift a little "sideways" so there will be a bit of a step in between all the cuts. But it's cosmetic only and will be hidden inside my personal gun, so I think I can survive that.
And I think the ~30g is worth the effort so will get that done tomorrow and then I can assemble the gun.
Any additional weight savings would have to come from also turning down the OD of the shooting barrel but I am not sure I am ready for that as it's the main structural part holding the whole gun together. Apart from that the only ways to save some weight would be to make a new version of the nose cone, but I can only save another 8g or so there and then perhaps the same for a new bulkhead which isn't really worth the work right now. I do have an idea for making the reel itself lighter but we will see I get around to that.
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Almost There - But Alas A Leak... Part 1
I actually just assembled the gun a few hours back and it looks pretty nice:
It felt a lot lighter which was the goal but it leaked badly at the handle - between the reservoir and handle. So at the very least the culprit isn't one of my homemade parts. Still a bit annoying and it's been years since I had a leak like that. It's never easy, is it... haha
Anyhow, let me backtrack a bit. Actually, let's start with a leftover from yesterday:
That's a little stainless steel precision washer that sits in the nose cone right in front of the pumping barrel piston. Its job is to stop the piston and to do this as well as possible it needs to have the smallest possible ID - this will make the flange the piston rest on as wide as possible. I say precision since you are allowed to use that word whenever you use reamers - even cheap ones on a cheap Chinese mini lathe, haha:
The UBL tail end I am using on the 7mm shaft is exactly 8.0mm in diameter so I have about 0.025mm around it for clearance. Not much, but the real machinists and engineers have a saying I like: "Clearance is clearance". So, as long as it can get through, no more is needed.
OK, back to today's meanderings. I turned down the OD on the pumping barrel from 12mm to ~11mm. As mentioned I had to do it bit by bit:
I wasn't particularly careful about feeds & speeds or keeping it cool and lubricated as you can tell from the less than stellar cut quality. I mentioned I don't yet have a follower rest but I do have a steady rest and one of the first projects I made on the CNC was to cut some better "fingers" for it. Originally it came with these really rough brass ones. I made a set in alu instead and put ball bearings in them:
It looks like it has badly marred, or burnished (to be nicer) the barrel but it's just that it kinda polished the surface whereas the rest of the tube is dull from sanding:
Sanding it on the lathe running slow with first 400 and then 800 grit with some WD-40 worked pretty well though it's just to make it bit less rough looking, it has zero functional impact. But hey, my hands turned almost completely silver with the alu dust sludge, so that's nice...
Anyhow, I mentioned I would save 30-35g on turning down the OD of the pumping barrel but I did a little better than that - almost 39g saved:
This brings the total weight savings to 241g, almost a quarter of a kilo, pretty nice.
I also drilled two holes in the front of the trigger guard to mount the reel and bent the reel frame a bit plus turned a little Delrin spacer to mount the real better:
And then it was onto assembly. This went pretty smoothly - those shallow chamfers I have on the nose cone help a ton.
I need a little hack though when inserting the nose cone: I use two o-rings to space the pumping barrel away from the shooting barrel and keep it from flopping around - makes it easier to get both barrels lined up for their bores in the nose cone.
Looking at this pic and the two rear-most o-ring grooves I used with the old nose cone - I now remember that front one chattered right at the end od the cut. I have since given the lathe a bit of love - some gib adjustment, some shims here and there and overall tightening so all the o-ring grooves I cut this time around went smoothly with zero chatter.
As for making sure the two barrels are aligned properly during assembly, I have actually drawn up a little "double barrel sleeve" that can do this job:
The plan was to machine it out of alu or Delrin but haven't gotten around to that, so for now the two o-rings do the trick.
To be continued...
I actually just assembled the gun a few hours back and it looks pretty nice:
It felt a lot lighter which was the goal but it leaked badly at the handle - between the reservoir and handle. So at the very least the culprit isn't one of my homemade parts. Still a bit annoying and it's been years since I had a leak like that. It's never easy, is it... haha
Anyhow, let me backtrack a bit. Actually, let's start with a leftover from yesterday:
That's a little stainless steel precision washer that sits in the nose cone right in front of the pumping barrel piston. Its job is to stop the piston and to do this as well as possible it needs to have the smallest possible ID - this will make the flange the piston rest on as wide as possible. I say precision since you are allowed to use that word whenever you use reamers - even cheap ones on a cheap Chinese mini lathe, haha:
The UBL tail end I am using on the 7mm shaft is exactly 8.0mm in diameter so I have about 0.025mm around it for clearance. Not much, but the real machinists and engineers have a saying I like: "Clearance is clearance". So, as long as it can get through, no more is needed.
OK, back to today's meanderings. I turned down the OD on the pumping barrel from 12mm to ~11mm. As mentioned I had to do it bit by bit:
I wasn't particularly careful about feeds & speeds or keeping it cool and lubricated as you can tell from the less than stellar cut quality. I mentioned I don't yet have a follower rest but I do have a steady rest and one of the first projects I made on the CNC was to cut some better "fingers" for it. Originally it came with these really rough brass ones. I made a set in alu instead and put ball bearings in them:
It looks like it has badly marred, or burnished (to be nicer) the barrel but it's just that it kinda polished the surface whereas the rest of the tube is dull from sanding:
Sanding it on the lathe running slow with first 400 and then 800 grit with some WD-40 worked pretty well though it's just to make it bit less rough looking, it has zero functional impact. But hey, my hands turned almost completely silver with the alu dust sludge, so that's nice...
Anyhow, I mentioned I would save 30-35g on turning down the OD of the pumping barrel but I did a little better than that - almost 39g saved:
This brings the total weight savings to 241g, almost a quarter of a kilo, pretty nice.
I also drilled two holes in the front of the trigger guard to mount the reel and bent the reel frame a bit plus turned a little Delrin spacer to mount the real better:
And then it was onto assembly. This went pretty smoothly - those shallow chamfers I have on the nose cone help a ton.
I need a little hack though when inserting the nose cone: I use two o-rings to space the pumping barrel away from the shooting barrel and keep it from flopping around - makes it easier to get both barrels lined up for their bores in the nose cone.
Looking at this pic and the two rear-most o-ring grooves I used with the old nose cone - I now remember that front one chattered right at the end od the cut. I have since given the lathe a bit of love - some gib adjustment, some shims here and there and overall tightening so all the o-ring grooves I cut this time around went smoothly with zero chatter.
As for making sure the two barrels are aligned properly during assembly, I have actually drawn up a little "double barrel sleeve" that can do this job:
The plan was to machine it out of alu or Delrin but haven't gotten around to that, so for now the two o-rings do the trick.
To be continued...
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Almost There - But Alas A Leak... Part 2
Anyhow, as mentioned, the gun leaked at the handle - so, I took it apart again. The thing with these carbon reservoirs is that the inner layer is often quite rough. Here's an example on one of the worst ones I have (not the one I am using). It either shows a resin starved laminate and/or damage from when the manufacturer extracted the mandrel:
Either way, you can't seal against these surfaces. The tube I am using is not that bad but I always have to epoxy coat these inner surfaces at the ends and I did so on this one. And then sand it smooth - that's how I have always made these tubes seal (sometimes I add a very thin layer of fiberglass, too).
But the tube I am using this time is perfectly on spec, not the slightest bit over-sized and the Evo handle is right on spec too. It's really tight even in the stock Salvimar reservoir. So there wasn't actually room for much of a resin coat. And to make matters worse, only the outside layer of these tubes is a 0/90 degree weave like you can see on the outside surface. All the rest are unidirectional with fibers only running in one direction - and then changing 90 degrees at each layer - very strong along the fibers but can split pretty easily across them.
And that's what happened, a splinter pulled out of that first uni layer. I guess it happened during assembly as it looked fine prior to that. Maybe it happened from twisting the handle.
It looks worse in this pic as it was after I had pulled on the splinter. Still, it's not great.
The fix will be to fill this void back up. Maybe not a great idea but I will glue the broken piece back in:
And adding a bit of epoxy with micro spheres as a filler to hopefully fill any gaps. The filler makes the resin easier to sand afterwards, too:
Tomorrow, after a bit of sanding, I will know if the fix worked. If it does, I will be spearing in the afternoon.
If it doesn't, I probably have to cut down another CF tube and use that instead. I have one long one from when this very project was a blue water build but I don't need that tube/gun for at least another three months. It's too big for around here and I don't have any trips planned to places with big fish.
I will order more tubes pretty soon anyways and will ask the manufacturer if they can add a regular thin layer of fiberglass on the inside as the first layer and make sure it has plenty of resin. It would be great if I don't have to coat and sand these tubes in the future.
Anyhow, as mentioned, the gun leaked at the handle - so, I took it apart again. The thing with these carbon reservoirs is that the inner layer is often quite rough. Here's an example on one of the worst ones I have (not the one I am using). It either shows a resin starved laminate and/or damage from when the manufacturer extracted the mandrel:
Either way, you can't seal against these surfaces. The tube I am using is not that bad but I always have to epoxy coat these inner surfaces at the ends and I did so on this one. And then sand it smooth - that's how I have always made these tubes seal (sometimes I add a very thin layer of fiberglass, too).
But the tube I am using this time is perfectly on spec, not the slightest bit over-sized and the Evo handle is right on spec too. It's really tight even in the stock Salvimar reservoir. So there wasn't actually room for much of a resin coat. And to make matters worse, only the outside layer of these tubes is a 0/90 degree weave like you can see on the outside surface. All the rest are unidirectional with fibers only running in one direction - and then changing 90 degrees at each layer - very strong along the fibers but can split pretty easily across them.
And that's what happened, a splinter pulled out of that first uni layer. I guess it happened during assembly as it looked fine prior to that. Maybe it happened from twisting the handle.
It looks worse in this pic as it was after I had pulled on the splinter. Still, it's not great.
The fix will be to fill this void back up. Maybe not a great idea but I will glue the broken piece back in:
And adding a bit of epoxy with micro spheres as a filler to hopefully fill any gaps. The filler makes the resin easier to sand afterwards, too:
Tomorrow, after a bit of sanding, I will know if the fix worked. If it does, I will be spearing in the afternoon.
If it doesn't, I probably have to cut down another CF tube and use that instead. I have one long one from when this very project was a blue water build but I don't need that tube/gun for at least another three months. It's too big for around here and I don't have any trips planned to places with big fish.
I will order more tubes pretty soon anyways and will ask the manufacturer if they can add a regular thin layer of fiberglass on the inside as the first layer and make sure it has plenty of resin. It would be great if I don't have to coat and sand these tubes in the future.
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Thanks for that sketch - that's a pretty good idea for a "save", but a sleeve like that would have to be quite long as it's not only the handle boss it would need to cover - there's also a long bulkhead that it would need to span. So, it may not be worth the effort on this build, I think. Also, my alu parts are not anodized so if they start corroding, it may seep under the glue joint and break it. But I'll keep this idea in mind in case fixing the CF reservoir doesn't work or if the other tube is equally tight.
I have made the resin coating work on all my other CF reservoirs, this is the first that gave me trouble like this. And honestly, it's only because the Mares handle boss leaves less room than any other stock handle I have.
But here's the thing, the next big project will be a home made alu handle, made from scratch, in which case I can just leave a little bit more space for the CF reservoir. And if my homemade handle works, I will no longer use any Italian plastic handles, ever
.Designing and making my own handle is an old dream of mine and I have the design ready - it'sjust going to take some clever solutions to actually machine it on my "little machine". But I will get going on this in a few months, I think. I think I can even make one that's not going to end up any heavier than the Italian ones and it will have some nice improvements on the inside. But of course, I will share that project once I get to it
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Still Leaking....
So, in this pic it leaks at the front but that's because I tried my luck at just turning the reservoir around as the o-rings at the nose cone sits slightly less deep into the reservoir but didn't work.
That's the main news, haha. But we got here - well, we didn't really get anywhere - by way of sanding the repair from yesterday:
This is after the first round of sanding - it leaked after this, so it's been sanded even more now, just no pics and to no avail.
I mentioned I have a longer CF tube for when this gun was a long bluewater "dogtooth gun":
I think I will just cut that one down to size - and then go through the whole epoxy coating again. It worked fine on that tube, so hopefully it will again. It's also 0.5mm thicker so a bit stronger (I have had these tubes in 40, 40.5 and 41mm OD) - though of course there's a bit of a weight penalty for the thicker tube, but it's the only one I have left until I order some more.
In slightly more positive news - yesterday I also mentioned that I had drawn up an alignment sleeve to help the two barrels line up so they glide into the nose cone easily. Spurred on by commenting on LG's use of CNC'ed Delrin on a thread of Pete's, I thought I should put some action behind my words, haha. So, I whipped it out really fast on the CNC:
Single flute polished endmill - and plenty of air and coolant:
And then I parted it off on the lathe manually, just the fastest and easiest:
I am ok with a 1.75g part
And it works great:
So, in this pic it leaks at the front but that's because I tried my luck at just turning the reservoir around as the o-rings at the nose cone sits slightly less deep into the reservoir but didn't work.
That's the main news, haha. But we got here - well, we didn't really get anywhere - by way of sanding the repair from yesterday:
This is after the first round of sanding - it leaked after this, so it's been sanded even more now, just no pics and to no avail.
I mentioned I have a longer CF tube for when this gun was a long bluewater "dogtooth gun":
I think I will just cut that one down to size - and then go through the whole epoxy coating again. It worked fine on that tube, so hopefully it will again. It's also 0.5mm thicker so a bit stronger (I have had these tubes in 40, 40.5 and 41mm OD) - though of course there's a bit of a weight penalty for the thicker tube, but it's the only one I have left until I order some more.
In slightly more positive news - yesterday I also mentioned that I had drawn up an alignment sleeve to help the two barrels line up so they glide into the nose cone easily. Spurred on by commenting on LG's use of CNC'ed Delrin on a thread of Pete's, I thought I should put some action behind my words, haha. So, I whipped it out really fast on the CNC:
Single flute polished endmill - and plenty of air and coolant:
And then I parted it off on the lathe manually, just the fastest and easiest:
I am ok with a 1.75g part
And it works great:
On Spec...? Maybe? Nah...
OK, before I get back to cutting down the longer CF tube, I wanted to back up what I said yesterday about the Mares handle being a super tight fit. I said "on spec" but it's actually oversized:
Whilst the Predathor handle is about 0.1mm under:
Granted, I have only ever used this Mares handle in two different CF reservoirs and one stock Predathor reservoir - and it's a very, very tight fit in all of them, also in the stock Salvi tube. I don't know if this handle goes in better in Mares' own tubes. I guess this can happen as the molds get older and worn, but as far as I recall the handle looked pretty good when I got it, no huge flash lines or anything like that - and I got it pretty early on in the production run. Anyways, can't blame Mares for this, haha. It is what it is.
Now, onto cutting down that other CF tube. Will go about it in a different way than last time around. More on that in a day or two.
OK, before I get back to cutting down the longer CF tube, I wanted to back up what I said yesterday about the Mares handle being a super tight fit. I said "on spec" but it's actually oversized:
Whilst the Predathor handle is about 0.1mm under:
Granted, I have only ever used this Mares handle in two different CF reservoirs and one stock Predathor reservoir - and it's a very, very tight fit in all of them, also in the stock Salvi tube. I don't know if this handle goes in better in Mares' own tubes. I guess this can happen as the molds get older and worn, but as far as I recall the handle looked pretty good when I got it, no huge flash lines or anything like that - and I got it pretty early on in the production run. Anyways, can't blame Mares for this, haha. It is what it is.
Now, onto cutting down that other CF tube. Will go about it in a different way than last time around. More on that in a day or two.
Lost My Carbon Mojo...
The rest of the day went with cutting down the longer reservoir and yet another side project:
I used a diamond coated cutoff wheel on my small hand grinder and it cuts through the wall super easily. I prefer going all the way through and then chase the circumference - using the tape edge as a guide. But either I am losing my mojo or these tubes split a bit easier than others, because I also managed to pull a little but of the uni-directional inner layer on this one...:
I think it happened right when I was about to make it full circle, when the tube kinda "breaks apart". I don't recall having this problem before, though.
I think the only advise I can give is to not to free hand cutting tubes over your knees. If I had put the tube on the table and turned it bit by bit, I don't think I would have had that splinter as the tube wouldn't have been able to "bend" just at the very end of the cut - my bad...
The very best would be a chop saw with an abrasive cutoff wheel which would make a smooth, square cut but I don't have that.
Anyways, it's not as severe as the splinter on the other reservoir.
I have sanded and done the first epoxy coat now though no pics of that and while one coat is normally enough, I may need two on this one. Tomorrow will tell.
I also want to try a new way of squaring the cut up after the epoxy coating. I see three ways:
1). Use the CNC fixture from a few days back but I am not super happy about the floppy sanding tool I used on that and it's the only one with enough reach.
2). Make a jig that mounts on the end of the tube after the rough cut but which offers a perpendicular face to block sand down to - as a result, the tube edge will be nice and square. I have done that once with a 3D printed jig and I could make a new one in alu on the CNC easily.
3). Mount the CF tube on the lathe and use a tool post grinder but... since I didn't have a tool post grinder I had to make one. Didn't take too long though. But it's funny how do many small tasks results in side projects.
Actually, I have always wanted a tool post grinder. I will make a proper one some day, but for now, I just made an adapter for another hand grinder, I had lying around. It's not stiff enough to use for many things but for this, it should work.
Here I am doing a first test on a small CF tube:
It worked pretty well:
There's a ton of run-out on these little cheap wheels but then I remembered that when they dress the wheels on proper surface grinders they use a small diamond tool. I don't have that, but I did have a sanding plate which supposedly have some diamond dust on it. So, I pressed that against the chuck and then ran the wheel on it. It runs a whole lot more true now and will hopefully cut even more smoothly now:
(The pic is after the "dressing" which took a lot off of the wheel - and some off of the sanding plate - I mostly used the shorter edges on the top and bottom of the plate).
The challenge tomorrow will be that the CF reservoir tubes do not fit through the spindle of the lathe. So, I will have to make an arbor of sorts and hold the other end with the steady rest. At the very least, as the result of yet another side project, I now have a (not very stiff) tool post grinder.
The rest of the day went with cutting down the longer reservoir and yet another side project:
I used a diamond coated cutoff wheel on my small hand grinder and it cuts through the wall super easily. I prefer going all the way through and then chase the circumference - using the tape edge as a guide. But either I am losing my mojo or these tubes split a bit easier than others, because I also managed to pull a little but of the uni-directional inner layer on this one...:
I think it happened right when I was about to make it full circle, when the tube kinda "breaks apart". I don't recall having this problem before, though.
I think the only advise I can give is to not to free hand cutting tubes over your knees. If I had put the tube on the table and turned it bit by bit, I don't think I would have had that splinter as the tube wouldn't have been able to "bend" just at the very end of the cut - my bad...
The very best would be a chop saw with an abrasive cutoff wheel which would make a smooth, square cut but I don't have that.
Anyways, it's not as severe as the splinter on the other reservoir.
I have sanded and done the first epoxy coat now though no pics of that and while one coat is normally enough, I may need two on this one. Tomorrow will tell.
I also want to try a new way of squaring the cut up after the epoxy coating. I see three ways:
1). Use the CNC fixture from a few days back but I am not super happy about the floppy sanding tool I used on that and it's the only one with enough reach.
2). Make a jig that mounts on the end of the tube after the rough cut but which offers a perpendicular face to block sand down to - as a result, the tube edge will be nice and square. I have done that once with a 3D printed jig and I could make a new one in alu on the CNC easily.
3). Mount the CF tube on the lathe and use a tool post grinder but... since I didn't have a tool post grinder I had to make one. Didn't take too long though. But it's funny how do many small tasks results in side projects.
Actually, I have always wanted a tool post grinder. I will make a proper one some day, but for now, I just made an adapter for another hand grinder, I had lying around. It's not stiff enough to use for many things but for this, it should work.
Here I am doing a first test on a small CF tube:
It worked pretty well:
There's a ton of run-out on these little cheap wheels but then I remembered that when they dress the wheels on proper surface grinders they use a small diamond tool. I don't have that, but I did have a sanding plate which supposedly have some diamond dust on it. So, I pressed that against the chuck and then ran the wheel on it. It runs a whole lot more true now and will hopefully cut even more smoothly now:
(The pic is after the "dressing" which took a lot off of the wheel - and some off of the sanding plate - I mostly used the shorter edges on the top and bottom of the plate).
The challenge tomorrow will be that the CF reservoir tubes do not fit through the spindle of the lathe. So, I will have to make an arbor of sorts and hold the other end with the steady rest. At the very least, as the result of yet another side project, I now have a (not very stiff) tool post grinder.
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A New (to me) Way of Cutting Carbon Tubes
So, another day in the workshop working on carbon reservoirs.
Yesterday, I whipped up a tool holder to make a little electrical hand grinder into a "tool post grinder" for the lathe. The idea was to use it to square up the edges on the carbon reservoir tube. But since my lathe is tiny, I can't pass the tube through the chuck and spindle. So, I had to come up with an arbor to mount the tube onto:
First, I thought I had to split the arbor and use a countersunk screw to open the lobes and press against the ID of the tube, but then I realized I could probably get away with just the friction of an o-ring as there really isn't any force to speak off when grinding like this.
Next up was mounting the tube onto the arbor and through the steady rest at the rear and then indicate it so it runs fairly true. Actually, I don't think it has to run super true as the grinder is fixed along the Y and Z and only moves in and out and the part (tube) is spinning. (Difficult to explain, but I don't think it matters much how true it runs):
Then it was time to grind the edge and it was pretty uneventful, it just worked. I blued up the edge a few times and ones the bluing was gone, I knew the edge was all nice and square (just imagine both the grinder and tube spinning in the pic):
The edge came out as good as I hoped, no pulled fibers:
I chamfered the inside edge by hand and sanded the inner walls a bit more ending with 2000 grit and then assembled the gun but... it still leaked. A tiny leak, but a leak is a leak so another coat of epoxy is in order. There's likely still a low spot where the fiber pulled out yesterday that the first coat didn't fully fill up:
The above picture is of the thicker reservoir I cut down from the long gun, but I also gave the thinner one, the one with the bigger splinter, another rescue attempt. With some more sanding, at least we can see that the previous resin with microballons did a good job at filling in around the splinter:
Come to think about it, it's been years since I last had to prep one of these tubes and it's not impossible that I actually used to do 2-3 coats with sanding in between before I got a perfect seal - and that I just forgot, haha. What I do know is that on some of the later tubes I used a very, very thin layer of fiberglass. Something like 0.03-0.05mm - not for any strength but it does a wonderful job of "holding" the resin so it doesn't fisheye and I think it fills in lows better. So maybe when using that, I have have been able to get away with just one coat. But I don't have any of that cloth right now so perhaps that's why this is trickier than I remember it being.
Also, the resin I have on hand has a slow hardener whereas with a fast hardener I would have been able to do three coats in a day. But with this slow hardener it's pretty much only one coat per day. Doesn't help that this resin cures rock hard and takes forever to sand. Anyways, enough complaining. Time to tidy up this mess of workshop now...
P.S.
Found some pics from 2016 in another thread chronicling another Mirage build, haha. It shows me using the thin fiberglass - you can see it totally "disappears" once wetted out. I think I ordered the first CF tubes back in 2015 so that's why I can't recall how many layers of epoxy it took to seal them, haha:
So, another day in the workshop working on carbon reservoirs.
Yesterday, I whipped up a tool holder to make a little electrical hand grinder into a "tool post grinder" for the lathe. The idea was to use it to square up the edges on the carbon reservoir tube. But since my lathe is tiny, I can't pass the tube through the chuck and spindle. So, I had to come up with an arbor to mount the tube onto:
First, I thought I had to split the arbor and use a countersunk screw to open the lobes and press against the ID of the tube, but then I realized I could probably get away with just the friction of an o-ring as there really isn't any force to speak off when grinding like this.
Next up was mounting the tube onto the arbor and through the steady rest at the rear and then indicate it so it runs fairly true. Actually, I don't think it has to run super true as the grinder is fixed along the Y and Z and only moves in and out and the part (tube) is spinning. (Difficult to explain, but I don't think it matters much how true it runs):
Then it was time to grind the edge and it was pretty uneventful, it just worked. I blued up the edge a few times and ones the bluing was gone, I knew the edge was all nice and square (just imagine both the grinder and tube spinning in the pic):
The edge came out as good as I hoped, no pulled fibers:
I chamfered the inside edge by hand and sanded the inner walls a bit more ending with 2000 grit and then assembled the gun but... it still leaked. A tiny leak, but a leak is a leak so another coat of epoxy is in order. There's likely still a low spot where the fiber pulled out yesterday that the first coat didn't fully fill up:
The above picture is of the thicker reservoir I cut down from the long gun, but I also gave the thinner one, the one with the bigger splinter, another rescue attempt. With some more sanding, at least we can see that the previous resin with microballons did a good job at filling in around the splinter:
Come to think about it, it's been years since I last had to prep one of these tubes and it's not impossible that I actually used to do 2-3 coats with sanding in between before I got a perfect seal - and that I just forgot, haha. What I do know is that on some of the later tubes I used a very, very thin layer of fiberglass. Something like 0.03-0.05mm - not for any strength but it does a wonderful job of "holding" the resin so it doesn't fisheye and I think it fills in lows better. So maybe when using that, I have have been able to get away with just one coat. But I don't have any of that cloth right now so perhaps that's why this is trickier than I remember it being.
Also, the resin I have on hand has a slow hardener whereas with a fast hardener I would have been able to do three coats in a day. But with this slow hardener it's pretty much only one coat per day. Doesn't help that this resin cures rock hard and takes forever to sand. Anyways, enough complaining. Time to tidy up this mess of workshop now...
P.S.
Found some pics from 2016 in another thread chronicling another Mirage build, haha. It shows me using the thin fiberglass - you can see it totally "disappears" once wetted out. I think I ordered the first CF tubes back in 2015 so that's why I can't recall how many layers of epoxy it took to seal them, haha:
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Sanding Rotisserie...
More "fun in the workshop with sanding... And by fun, I mean that I pretty much loathe sanding. But after the latest round of resin coating, inspired by yesterday's trueing up of the edges on the lathe, I thought: "Why not sand on the lathe".
Here's a test piece, it's the cutoff from the longer, thicker tube:
In the lower, right side of the pic is a sanding mandrel (just a rod of POM). Pretty much as thick as the tube ID will let me have it. It makes sanding straight and flat - whatever the term is for flat inside a tube - a whole lot easier. Also, you sand with more surface area than when just using your finger. And having the lathe spin whilst sanding really speeds things up. So, more "precise" and more efficient. With the big sanding mandrel high spots are also much easier to take down evenly, whereas it's almost impossible just with a finger. Even I am almost OK with sanding like this.
You can see some obvious low spots here:
Almost gone here:
And very close to gone here:
But why even bother working on this offcut - it's way too short to use on a gun. Because I will finally blow some of these up. So, they need to seal too, of course. I will also prep an offcut of the thinner tube and blow that one up, too. But it will take a few weeks. I have a work trip starting tomorrow.
Anyhow, prepping this shorter piece of tube also was good practice for the full length for the gun:
Again, some early low spots:
But they cleaned up nicely (some Posca marker on this one to see where the handle still binds):
Leaving the surface a bit rough @ #220 grit for the next and maybe final resin coat...
A regular mini-lathe may or may not be able to do this, but one of the first mods I did to mine was to swap the weak 500w brushed motor with a 750w brushless and gear it a bit lower, too. So, it doesn't stall at slow speed and can run really slow - which makes cutting threads easier. The tachometer isn't mounted right now, but if I recall correctly the slow speed is something like 60-70rpm. For sanding, it's perfect but for spinning whilst curing the resin, I would like it even slower.
The (fishing) rod building guys have or make their own slow turning rotisserie rigs for when they epoxy coat their rods or baits.
If I had to do a lot more of these tubes, I think I'd build something like that.
More "fun in the workshop with sanding... And by fun, I mean that I pretty much loathe sanding. But after the latest round of resin coating, inspired by yesterday's trueing up of the edges on the lathe, I thought: "Why not sand on the lathe".
Here's a test piece, it's the cutoff from the longer, thicker tube:
In the lower, right side of the pic is a sanding mandrel (just a rod of POM). Pretty much as thick as the tube ID will let me have it. It makes sanding straight and flat - whatever the term is for flat inside a tube - a whole lot easier. Also, you sand with more surface area than when just using your finger. And having the lathe spin whilst sanding really speeds things up. So, more "precise" and more efficient. With the big sanding mandrel high spots are also much easier to take down evenly, whereas it's almost impossible just with a finger. Even I am almost OK with sanding like this
.You can see some obvious low spots here:
Almost gone here:
And very close to gone here:
But why even bother working on this offcut - it's way too short to use on a gun. Because I will finally blow some of these up
. So, they need to seal too, of course. I will also prep an offcut of the thinner tube and blow that one up, too. But it will take a few weeks. I have a work trip starting tomorrow.Anyhow, prepping this shorter piece of tube also was good practice for the full length for the gun:
Again, some early low spots:
But they cleaned up nicely (some Posca marker on this one to see where the handle still binds):
Leaving the surface a bit rough @ #220 grit for the next and maybe final resin coat...
A regular mini-lathe may or may not be able to do this, but one of the first mods I did to mine was to swap the weak 500w brushed motor with a 750w brushless and gear it a bit lower, too. So, it doesn't stall at slow speed and can run really slow - which makes cutting threads easier. The tachometer isn't mounted right now, but if I recall correctly the slow speed is something like 60-70rpm. For sanding, it's perfect but for spinning whilst curing the resin, I would like it even slower.
The (fishing) rod building guys have or make their own slow turning rotisserie rigs for when they epoxy coat their rods or baits.
If I had to do a lot more of these tubes, I think I'd build something like that.
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Is this carbon tube worth the effort and time? Carbon is a strong but brittle material! Lightening the gun can end with it falling on a rock and exploding! It is necessary to put rubber on top of the carbon to soften the brittle blows!
Worth The Work?
It's worth it to me, as I really want a lighter gun. But it may not be worth it to others, I agree.
But I am a bit strange. I don't mind all these challenges and side projects if I feel like I learn something that I can use down the road. Just today, I learned how to sand these tubes about three times faster
Is Carbon Dangerous in Spearguns?
I'll start by saying that I will finally blow up some cutoffs of these two tubes so at least I know the ultimate burst pressure - it's something I have wanted to test for many years.
As for carbon being brittle - that's true. I think the ideal tube would have a mix of kevlar and carbon in it, so if an accident does happen, the kevlar should keep carbon from flying everywhere. Kevlar has much better impact resistance and when it breaks, the strands don't snap like carbon - which is why it's used in bullet proof helmets and vests.
That said, the real world experience seem to show no explosions have happened, yet.
I think I got my first CF tube 10 years ago. I may have seen it in videos from a famous Corsican spearo and then ordered my own. Some for me, some for a friend. Some years later, Salvimar put out a production gun with CF reservoirs that they are still selling and there are other builders/tinkerers out there using these tubes, too.
I don't think any of us have rubber or neoprene sleeves on them - it would almost defeat the purpose.
On a related note, there are high pressure tanks (200-300 bar) being made out of CF and I think even firefighters use them - but the PCP airgun guys certainly do.
How To Test CF Tubes for Speargun Use
Apart from testing burst pressure, the real question is what happens after many years of use? What happens after 1000s of shots/pressure cycles?
I am sure after Oceangate everyone "knows" that CF doesn't like repeated cyclic, compressive over-pressurizing.
I did think of a way to test this - but not sure I will get around to it unless I start selling guns to other people. But the way to test it would be take a test tube up to, say 40 bar, and then have a fast acting solenoid relief valve drop the pressure to say 30 bar to simulate the pressure drop during a shot (which is already way more of a pressure differential than the gun tube will experience, even in a Mirage system, I think...). And then back up to 40 bar, then down to 30 bar - for 1000s of times. And then do a max burst test to see if it lost any strength.
Also, what would make sense is to have the tube either painted or top coated with a UV protective top coat as epoxy doesn't like UV. Finally dropping a hammer on a tube would be interesting, too.
All that said , I try not to drop a high pressure gun onto a sharp edge anywhere but I don't treat them like babies, either.
Correction
I was partly wrong on the pressure differential experienced by the tube during operation. During the shot, the pressure will only reduce by a few bar, but the pressure differential between the front and rear chambers on a Mirage (divided by the bulkhead) after pre-loading will be almost the max possible as you "move" almost all the air from the rear to the front. Also, on a classic gun after a low power shot, the pressure differential would be larger, I think.
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maybe one other way to make it lighter in the water : https://www.massysub.it/prodotti/ap...umatici/fusti-galleggianti/oli-floater-detail or https://speargun.shop/accessories/Spearfishing Spearguns Float Universal
Yes, I think the Corsican spearo I mentioned had a tube like this on his longest gun early on.
I think it's a valid approach - use the stock alu barrel but add some shaped foam and then carbon over it.
But my real goal, the dream, is to have a tube like this - but in pure CF and less tall at the front for easier "panning". It's on the list of things I want to try. Maybe for a one-off it could be done over a male 3D printed core or a wax core. Or even a CNC milled foam core - anything that can be dissolved, melted or pulled out afterwards. And then if it works, then make a female mold and use a bladder type mandrel. Anyways, that's in the future - first, DIY handles
!
A
They look great. Nice custom grip work, too but what muzzles are they? Duccio's?
I came across his work during the pandemic but wasn't in the mood to check out too much but now that I am back in the swing of things I had a deeper look. He makes some cool stuff.
I feel like we have "parallel ideas" but he has proper machines, haha. But I am slowly adding to my machining capabilites. I even got a nicle little, sturdy CNC lathe recently - I "just" need to refurbish it and put a controller on it but I think the bones are super solid.
On my wish list of DIY parts - besides the holy grail of a completely new handle and custom CF reservoir - are pistons and vacuum nozzles, too. And whilst I think I will stick to something close to UBL's (and thus Salvimar, Pelengas and his) design I think I will go in a slightly different direction on the pistons.
And then of course I'd like to make tail ends and sliders for the shafts, too. Tail ends are easy - the sliders a bit more complicated. I thought I needed to weld the lugs on, but I think I can machine the whole sliders and not have to weld (which I don't know how to).
Might have to get a little heat treat oven so I can get the most out of 17-4ph for the shaft parts but they are cheap on the used market.
Are these your guns Nico?
They look great. Nice custom grip work, too but what muzzles are they? Duccio's?
I came across his work during the pandemic but wasn't in the mood to check out too much but now that I am back in the swing of things I had a deeper look. He makes some cool stuff
.I feel like we have "parallel ideas" but he has proper machines, haha. But I am slowly adding to my machining capabilites. I even got a nicle little, sturdy CNC lathe recently - I "just" need to refurbish it and put a controller on it but I think the bones are super solid.
On my wish list of DIY parts - besides the holy grail of a completely new handle and custom CF reservoir - are pistons and vacuum nozzles, too. And whilst I think I will stick to something close to UBL's (and thus Salvimar, Pelengas and his) design I think I will go in a slightly different direction on the pistons.
And then of course I'd like to make tail ends and sliders for the shafts, too. Tail ends are easy - the sliders a bit more complicated. I thought I needed to weld the lugs on, but I think I can machine the whole sliders and not have to weld (which I don't know how to).
Might have to get a little heat treat oven so I can get the most out of 17-4ph for the shaft parts but they are cheap on the used market.
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Oleos On Hold...
Speargun building will be on hold for 10-14 days as I just landed in Korea for some work.
But since I have some hours to kill whilst waiting for the next flight I reached out to the vendor that made my latest tubes back in 2018 and... they are OK with both adding an inner layer of fiberglass and some kevlar somewhere in the layup
They can also add a regular plain 3K weave on the inside which should withstand fibers being pulled out better than the unidirectional that's normally used but I think I will opt for fiberglass because it should offer more protection against galvanic corrosion as CF and alu doesn't play well together - but actually, a resin coat should also offer enough isolation. But with some luck, they can make it so smooth I don't even need to coat them myself.
Anyways, I am excited for those custom tubes. Will order them if the cutoffs of the old ones don't blow up too easily in my upcoming destruction test...
Also, I have mentioned that I am forgetful. Case in point: I said I don't have a follower rest but only a steady rest for the lathe. Well...:
That's a follower rest right there, the one my memory insists I don't have. I must have had it for years, it's just missing some hardware but since I can misplace this little chunk of iron, I am not surprised the rest is gone, too. But it should be around the workshop somewhere.
It's good news, though. It means I can turn down the OD of pumping and shooting barrels easier and with less of those steps in the future.
Speargun building will be on hold for 10-14 days as I just landed in Korea for some work.
But since I have some hours to kill whilst waiting for the next flight I reached out to the vendor that made my latest tubes back in 2018 and... they are OK with both adding an inner layer of fiberglass and some kevlar somewhere in the layup
They can also add a regular plain 3K weave on the inside which should withstand fibers being pulled out better than the unidirectional that's normally used but I think I will opt for fiberglass because it should offer more protection against galvanic corrosion as CF and alu doesn't play well together - but actually, a resin coat should also offer enough isolation. But with some luck, they can make it so smooth I don't even need to coat them myself.
Anyways, I am excited for those custom tubes. Will order them if the cutoffs of the old ones don't blow up too easily in my upcoming destruction test...
Also, I have mentioned that I am forgetful. Case in point: I said I don't have a follower rest but only a steady rest for the lathe. Well...:
That's a follower rest right there, the one my memory insists I don't have. I must have had it for years, it's just missing some hardware but since I can misplace this little chunk of iron, I am not surprised the rest is gone, too. But it should be around the workshop somewhere.
It's good news, though. It means I can turn down the OD of pumping and shooting barrels easier and with less of those steps in the future.
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no: they are a budy's gun (he painted the barrel). I think the muzzle are duccio's and the grip is from "Carbozzi NC Design" who lives in the south of France (next to my place).A
Are these your guns Nico?
They look great. Nice custom grip work, too but what muzzles are they? Duccio's?
I came across his work during the pandemic but wasn't in the mood to check out too much but now that I am back in the swing of things I had a deeper look. He makes some cool stuff
I feel like we have "parallel ideas" but he has proper machines, haha. But I am slowly adding to my machining capabilites. I even got a nicle little, sturdy CNC lathe recently - I "just" need to refurbish it and put a controller on it but I think the bones are super solid.
On my wish list of DIY parts - besides the holy grail of a completely new handle and custom CF reservoir - are pistons and vacuum nozzles, too. And whilst I think I will stick to something close to UBL's (and thus Salvimar, Pelengas and his) design I think I will go in a slightly different direction on the pistons.
And then of course I'd like to make tail ends and sliders for the shafts, too. Tail ends are easy - the sliders a bit more complicated. I thought I needed to weld the lugs on, but I think I can machine the whole sliders and not have to weld (which I don't know how to).
Might have to get a little heat treat oven so I can get the most out of 17-4ph for the shaft parts but they are cheap on the used market.
when he had sten, he had Dima's muzzle on.
Yeah, Carbozzi was also the builder making the long guns of the Corsican (?) I mentioned but whose name escapes me. Maybe Fabrice/Fabricio? Dived out of a fancy RIB and took some very long shots. His videos helped plant my obession with making a bluewater oleo
He also had a fiber optic sight glued straight onto the reservoir and that was definitely the inspiration into my own early forays into sights.