The Ultimate Travel Oleo? - A Custom-Sized Mirage 93

[Diving Gecko]

I am setting out to do another custom-sized Mirage. This time I want a gun no longer than my fins. The idea being to have the maximum length gun that I can easily chuck in my bag, jump on a bike/plane/etc, head to a beach and hunt the local reef.
Of course, if we were talking band guns this would be one measly gun but my Hunter 90 pneumatic has taken plenty of dinner sized fish and fits the above size requirements. It was my first gun and is still a real pleasure to use.
Here is an old pic of it in an earlier incarnation (under it is a Mirage 80):

As some of you know, the original Mirage came in two sizes: 80cm and 100cm (sometimes also labelled as 84 and 104). To confuse things even more, the Mirage model designations were quite "generous" as a Mirage 80/84 is about 15cm shorter than a Predathor 85 and 14cm shorter than a Seac Hunter 90. So, we can conclude that a Mirage 80 is quite a short gun, even in the world of pneumatics.

So, I thought: Why not make a Mirage version in the same size as the Hunter 90? This gun will be 13cm longer than the original Mirage 80 and thus 7cm shorter than their 100 model. It will be around 96cm total length and fire a spear very close to the same length. With the increase in power, I might even try to shoot 7.5-8mm spears to get a bit more mass into the projectile.

Additionally it will hopefully be the ideal companion to a longer one such as the Mirage 125 that I worked on in this thread.
Here is a pic of the Mirage 125 (with the first version of my custom handle), this time with the Hunter 90 in a newer disguise on the bottom:

Other goals in this build is to have the two Mirage handles be close in ergonomics so I can seamlessly switch from one gun to the other. And I am aiming to use the same muzzles, shock absorbers and pistons in both guns so I can minimize the amount of spares I need to travel with.

 

[Diving Gecko]

Shooting Barrel
A while back, I ordered three of the longest Predathor barrels that I could from http://www.edosub.it. I choose the Predathor barrels as they are 13mm barrels like the Mirage and are the longest and cheapest I could get. I used one for my Mirage 125 build and cut down a second one for this build.

I used my new Mini Lathe to do the needed mods such as cutting new o-ring grooves and trimming off 3mm at the back of the barrel. No pics of that, though.

Then on to the threads. But I do not yet feel 100% comfortable with cutting threads on the lathe with a cutting tool, so instead I made a die holder for an M14x1.25mm die for the muzzle thread on the barrel:

Here I am doing a test on a barrel cut-off:

I used my cheap Chinese bench drill with its even cheaper "milling attachment" to cut the notches in the rear of the barrel but I could have done it with a hacksaw and file:

 

[Diving Gecko]

Pumping Barrel O-Ring Groove and Rubber Valve
I ordered a length of 10x14mm alu tube from an online vendor in China and started the work to make it into a functional pumping barrel.
First of, I cut the front o-ring grooves for the pumping barrel (I modified the original design of the groove a little). My design is on top, original on the bottom:

The Mirage pumping barrel has a very simple one-way valve at the rear end. It's basically a piece of rubber hose covering four tiny holes in the barrel.
I didn't snap a pic when I cut the rear end on the lathe but here are two from when I drilled the four 1.4mm holes:

The hose itself has a very small wall thickness as there is not much room between the underside of the pumping barrel and the inside of the reservoir. I tried to get my hands on some hose with a thin wall and while I got some with 1mm thickness, I had a go at turning it down even thinner - it worked out a treat:

The outside is a little rough from the machining but the inside is fine. I tried a few different materials and cut it to length while it was on the mandrel - which is just a cut-off of the 10x14mm tube:

As a side note, looking at the original rubber hose (if it is indeed original) in my Mirage, it actually looks to have the same tiny ridges on the outside, so maybe Mares even had to turn their rubber valves down.

Here one of the rubber valves are mounted in place on the pumping barrel. As you can tell, I also turned down the rest of the pumping barrel to save some weight. I don't have a steady rest for the lathe yet, so had some issues with doing this as nicely as I would have wanted. But it's just a cosmetic problem, nothing more:

 

[Diving Gecko]

First Assembly
I just did the first assembly of the gun and... it leaks in three places. It leaks at the power regulator which I expect to be an easy fix, just change the o-rings and clean the seat well. Then it leaks at either the piston or the o-ring on the front of the barrel, I will sort that out later but I am not too worried yet. Finally, it leaks at the trigger once again.
This is the trigger I repaired by having a completely new bushing made and while it has worked most of the time, it is too prone to failures. I think it's because I ended up boring out the handle more than I thought I would when I drew up the bushing so the o-ring compression is a bit off and the gap between the bushing and the bore is too, as well.
Anyways, since I now have a lathe I think I will have a go at making a new one myself. More on that later.

Here are some snaps from a little while ago. The fins are beat up but the gun and fins are pretty much the same size which was the whole idea

BTW, I am using the reservoir (outer tank) from my Hunter 90 as I am out of carbon fiber tubes and this one had the right size. I am also, for now, using the latest handle from the Mirage 125. I like the active line release I made on that handle but I just need to get the trigger sealing to work properly.

 

[Diving Gecko]

Leaks
I am tackling the leak issues one by one these days.
For the power regulator, the stainless steel rod had mushroomed a bit at the end where the little thumb "handle" screws in. I think that might have increased the risk of pinching the o-rings on assembly.
To remedy this, I stuck the rod in the lathe and turned the offending "lip" down ever so slightly and while I had it in the lathe I polished the rod with some 2000 grit sandpaper. Now, I just need to clean out the seat properly and it should be good on reassembly. I might have a go at using quad rings instead of regular o-rings, too.

Trigger Bushing Design
As for the trigger bushing, I drew up another bushing with the updated measurements of the bore in the handle.
I have mentioned the free, browser-based CAD software Fusion360 a few times before and the recommendation still stands after Onshape severely restricted their free version:

And for help with o-ring design, I most often use Erik's O-ring Calculator (Trelleborg makes another good one):

I'll have a go at making the bushing in brass on the lathe in the next few days. Just need to wait for some precision drill bits to arrive.

 

[Diving Gecko]

Trigger Bushing Trial-Run
Today I made a trigger bushing in Delrin, mostly as a dry-run before I try to make one for real. Turned out pretty nice. The real one might actually have double o-rings on the inside, too. One inserting from the top, one from the bottom. Still undecided on that. The bushing is only 12mm long so not that much space but with a bit of care I think I can make it work.

Here are some snaps of the Delrin version. We start from the back, with the finalized bushing:

I didn't shoot much of the process, but basically, I just cut it on the lathe according to the design in the above post. For the internal thread, I was lacking a bottom tap so I cut one down (second pic) which actually worked a treat (I mounted the tap in a tool holder and a small cutting disk in the spindle):

Then, after cutting the top of the bushing down to final size, I needed to mill off a bit of the sides of the top flange. Once again, I had good use of one of the "guide rail holders". This time, as a fixture for the bushing. I used a 4mm end mill to mill the sides and I have to say, for plastic and soft metals, despite the lack of any kind of rigidity, this little setup has been worth the money:

 

[Diving Gecko]

Trimming The Nose Cone and Power Regulator Bulkhead
Forgot to mention that the nose cone and bulkhead has always been too tight a fit - or rather, the carbon reservoir is a tiny bit too tight on the inner diameter after the epoxy coat I added to deal with leaks. The tightness made it very difficult to disassemble the gun and even turning the reservoir to align the fiber optic sight or the nose cone was a huge task. Now, with the lathe, I could take off a little material in a jiffy and now all is good:

 

[zmajmr]

Hi, interesting to read what you doing and to look your pictures, I am curious which lathe did you buy

 

[Diving Gecko]

Hi, interesting to read what you doing and to look your pictures, I am curious which lathe did you buy

Hi Marko,
Good to hear from you.
I just got one of those small Chinese, unbranded so-called Mini Lathes. Same style as the smaller Sieg, Harbor Freight, Grizzly, Little Machine Shop, etc ones. Supposedly, they pretty much all come out of the same few (1-2?) factories. Mine is one size smaller than your first one, even. And kinda worse quality, as yours actually gets good reviews, especially the Germany-imported ones (I think your first one was an Optimum, right?).

Here's a vendor's pic of the one I got:

When it arrived, the run out of the chuck (and work piece in chuck) was 0.11mm but I got it down to 0.03mm now which I am more than happy with. The tailstock was 0.4mm out to the side and not parallel with the bed, either. It is better now, but could still get better.

In typical Chinese fashion the stickers on it refers to a high and low gear - though this one doesn't have that, haha. The lever and "transmission" are simply missing. It does have a tumbler gear, though to reverse the leadscrew direction which is not too shabby. The low gear hasn't been missed yet as I don't really take huge cuts. If it becomes a problem, I think upgrading to a more powerful brushless motor could be a solution.

Changing the gears for threading operations is a hassle but nothing I can do about it in this size and price of lathe.

I got some nice inserts for cutting alu and brass. I don't want to cut my own tools so these are great. I have a ridiculously cheap quick change tool post on the lathe now, which I might upgrade in the future but it is fine for now.
Most of my tooling (just a handful of different holders and inserts) are for alu but the one I used on the 17-4PH is from Mitsubishi and the series (or coating?) is called VP15TF. I know next to nothing about these things, but it came recommended from the shop and seemed to do a great job.

I also mounted a thread cutting dial and next up, I think I will mount a very cheap and "ghetto" DRO to the tailstock - just a cheap digital caliper cut down and attached to the quill and tailstock. It's a modification many have made on these lathes and today, making the bushing, I could really have used it to figure out exactly how deep into the piece I was drilling and threading.

Overall, I am super happy I got it and though I initially wanted the same as your first one, I realized I don't actually need the extra size and grunt. My lathe is inside my apartment, so smaller is better. Also, for USD 365 it has definitely been worth every cent

BTW, did you manage to restore your CNC lathe and get it running? I lost track of it a while back. Maybe you got too busy with your paid job;-)

 

[zmajmr]

Hi Marko,
Good to hear from you.
I just got one of those small Chinese, unbranded so-called Mini Lathes. Same style as the smaller Sieg, Harbor Freight, Grizzly, Little Machine Shop ones. They pretty much all come out of the same few (1-2?) factories. Mine is one size smaller than your first one, even. And kinda worse quality, as yours actually gets good reviews, especially the Germany-imported ones (I think your first one was an Optimum, right?).

Here's a vendor's pic of the one I got:

When it arrived, the run out of the chuck (and work piece in chuck) was 0.11mm but I got it down to 0.03mm now which I am more than happy with. The tailstock was 0.4mm out to the side and not parallel with the bed, either. It is better now, but could still get better.

In typical Chinese fashion the stickers on it refers to a high and low gear - though this one doesn't have that, haha. The lever and "transmission" are simply missing. It does have a tumbler gear, though to reverse the leadscrew direction which is not too shabby. The low gear hasn't been missed yet as I don't really take huge cuts. If it becomes a problem, I think upgrading to a more powerful brushless motor could be a solution.

Changing the gears for threading operations is a hassle, though. But nothing I can do about it in this size of lathe, though.

I did get some nice inserts for cutting alu and brass, I don't want to cut my own tools and these are just great. I got a ridiculously cheap quick change tool post, which I might upgrade in the future but it is fine for now.
Most of my tooling (just a handful of different holders and inserts) are for alu but the one I used on the 17-4PH is from Mitsubishi and the series (or coating?) is called VP15TF. I know next to nothing about these things, but it came recommended from the shop and seemed to do a great job.

I also mounted a thread cutting dial and next up, I think I will mount a very cheap and "ghetto" DRO to the tailstock - just a cheap digital caliper. It's a modification many have made on these lathes and today, making the bushing, I could really have used it to figure out exactly how deep into the piece I was drilling.

Overall, I am super happy I got it and though I initially wanted the same as your first one, I realized I don't actually need the extra size and grunt. My lathe is inside my apartment, so smaller is better. Also, for USD 365 it has definitely been worth every cent

BTW, did you manage to restore your CNC lathe and get it running? I lost track of it a while back. Maybe you got too busy with your paid job;-)

Hi, thx for replay, mine is Quantum but is basically same as Optimum and I still have lathe, it is good to have manual machine together with CNC machine, some things are easier and faster to do on manual machine. I saw your insert and now after reading I conclude how you mange to get it and you are newbie, definitely way to go for machining aluminum, sharper it is better surface finish. I noticed you machined some rubber hose, you can check buy submerge in it in oil which you gonna use in your gun will it swallow, if yes then maybe you will have leaking problems. Keep up with nice work.

 

[Diving Gecko]

Hi, thx for replay, mine is Quantum but is basically same as Optimum and I still have lathe, it is good to have manual machine together with CNC machine, some things are easier and faster to do on manual machine. I saw your insert and now after reading I conclude how you mange to get it and you are newbie, definitely way to go for machining aluminum, sharper it is better surface finish. I noticed you machined some rubber hose, you can check buy submerge in it in oil which you gonna use in your gun will it swallow, if yes then maybe you will have leaking problems. Keep up with nice work.

Yeah, I can imagine how sometimes CNC is a hassle for quick little jobs. But so good to hear you made it work.

Thanks for the advice on the rubber hose - will definitely do that test, would be a pity to have a leak because of swelling. I do have some silicone in the same size (which is already slightly undersized on the ID for for a stretch-fit) so that is likely more resistant. Will check them both.

 

[Diving Gecko]

Trigger Bushing O-ring Testing
Went on to do a very unscientific test to check the fit of the internal trigger o-ring with various diameters of groove. In an ideal world, I would incorporate a pressurized container to check for leaks and I did actually consider it. But instead I just cut these three simple bushing testers real quick.

Though it was all by feel, I did learn that the 3.6mm version is actually so tight that I can't even get an 1.5x1.5 (SW x ID) o-ring to sit properly. The 3.8mm is perfect in that regard and the only size of the three where the o-ring doesn't want to pop out by itself.
Come to think about it, this was a problem with the last bushing and I think the o-ring sitting skewed in the seat could def explain some of the leaking and pinching.
According to the online calculators, a 3.8mm groove should still give me 20% compression on a 1.4mm trigger pin and 23% on a 1.5mm pin.

[EDIT] I remembered I had a third party 1.5mm trigger set from Italy and I just measured it. It uses the same 1.5x1.5mm (SW x ID) o-ring but the o-ring seat diameter is just a smidge under 4.5mm. So, basically there is hardly any compression on the sides in that design. There might be a bit from the top where the second , smaller part of the two-part bushing inserts. For now, going with 3.8mm might provide a happy medium.
Once I receive some 3.8mm end mills I will set out to make the real bushing.

 

[Diving Gecko]

Trigger Bushing V3
Though this is my first "homemade" bushing, I am calling this one V3 as I have previously had two others made.

I decided to simplify things a bit and not do two separate o-ring grooves (top and bottom) on the inside as I had considered earlier. That design would need two screws and they are fiddly to get right. I did however stick to double o-rings on the inside though I am just stacking them in the same groove now.
Here's a screen shot from the design software (Fusion360) of V3 just to show exactly how the inside of the bushing looks:

Unlike V1 and V2 this latest version has the inner o-rings inserting from the bottom. So, if the outer o-rings don't need to be serviced, I can still get to the inner ones in the regular manner - from the underside of the handle. With V1 and V2, I had to take the whole gun apart to get the bushing out from inside the handle and then pop out the inner o-rings from the top of the bushing.

After I spent a few hours getting the tailstock on my Chinese hobby lathe in much better alignment I was ready to try my luck at making the bushing. If the tailstock is not properly aligned you'd risk snapping the tiny drill bits inside the part.

Even though it was pretty straight forward to cut this bushing I am still so new at this that I forget the picture taking while concentrating on the machining job;-) So, once again, not many pics from the turning itself, but here is one I took right after chamfering the edges and not long before I part off the bushing from the stock:

Here is the final result with some AA batteries for scale. The bushing is 12mm, or less than half an inch, tall:

The colors on these pics are a bit off so the brass doesn't really come out as well as in real life. In the following pic, you can see that the outer, lower o-ring is a so-called quad or X-ring. The idea is that you get an extra lip and extra seal on the same ring:

As mentioned the inner o-rings insert from the bottom this time which should be more serviceable. They are held in place by a modified M5 screw:

I didn't make that screw from scratch, instead I "cheated" and used a 304 stainless steel one that I already had. I cut off the head, drilled the 1.45mm bore, then cut a small step which protrudes into the o-ring seat and keeps the o-rings in place. Finally, I made a slot for a screwdriver and cut the screw to final length.
Just have one pic from when I chamfered the edge (though I got lazy and just used my alu tooling insert as I only have one left hand tool holder and didn't bother swapping out the insert):

Lastly, two pics of the bushing disassembled:

BTW, the trigger pin is only 1.3mm in diameter but since the busing is much taller than a regular trigger assembly and the bore holes at either end are less than 0.1mm oversize the pin is very well supported. I think the risk of it bending is negligible.

I could really have done with a digital readout on the tailstock for this job. Drilling the depth of the o-ring seat, threading the bushing and making the screw and its little step would have been a lot easier with some "live" and precise measuring help. There is a very cheap way to get this added to the lathe, so I will do that as my next mod/upgrade on the lathe.

 

[Diving Gecko]

Pumping Barrel Piston
The Mirage is a special design in that it has two internal barrels: The regular 13mm "shooting barrel" and a secondary, small 10mm "pumping or pre-loading barrel". Both need pistons but the smaller one is simpler as it doesn't need a metal mushroom tail for the trigger to latch onto.

I have previously drawn up one for Dima in Ukraine to make for me and that one has worked well. But there is one very small improvement that can be done and since it is such a simple part, I thought I might as well make a new one myself.

Here's some red POM (Delrin) stock in the lathe and the piston is almost done at this point. The double o-ring grooves have been cut and I am trial fitting one of Dima's special shaft tail ends. They have a much smaller diameter on the stub than regular tail ends (you can see the drill bit still sitting in the tailstock chuck):

Here's a closer look. The reason for the o-ring (actually, and "x-ring") is that I wanted to do a quick check on the fit so I slid the pumping barrel over the piston while it was still in the lathe.

Parting off the finished piston from the rest of the stock (didn't bother to take the o-ring off):

The white piston is Dima's original one and you can see how small the stub on the shaft tail end is:

My first muzzle set from him had tail end stubs that were slightly larger and the hole in the white piston reflects that. But on the second one, Dima had reduced the stub diameter. I think to keep more material at the very front of the piston in the shooting barrel which takes a beating as it rams into the shock absorber. I like the idea of that change as I have broke pistons in Mirages previously. My new pumping piston, the red one, has a reduced bore to better fit the newer version of the tail ends. This should keep the shaft end centered and reduce the risk of any scratching of the pumping barrel:

I went with double quad rings for seals on this piston as the final pic below shows.
That's about as safe as it gets with four sealing lips vs. the 1-2 I have had on previous pistons. Any increase in friction wont matter here:

I didn't chamfer the top of the piston on purpose. I want as much surface area on the front of the piston as possible as the flange (a stainless steel washer) it rests on in the nose cone is quite small. Being that the piston is made of plastic the sharp edge shouldn't really scratch the inside of the barrel either.

Next up: I am pretty much ready for a second attempt at putting this gun together, I am just waiting for some slightly bigger o-rings which I hope will take care of the leaking front. (That leak was either the front o-ring on the shooting barrel or the piston leaking and the new o-rings will hopefully deal with the first of those two scenarios).

 

[tromic]

Pumping Barrel Piston
The Mirage is a special design in that it has two internal barrels: The regular 13mm "shooting barrel" and a secondary, small 10mm "pumping or pre-loading barrel". Both need pistons but the smaller one is simpler as it doesn't need a metal mushroom tail for the trigger to latch onto.

I have previously drawn up one for Dima in Ukraine to make for me and that one has worked well. But there is one very small improvement that can be done and since it is such a simple part, I thought I might as well make a new one myself.

Here's some red POM (Delrin) stock in the lathe and the piston is almost done at this point. The double o-ring grooves have been cut and I am trial fitting one of Dima's special shaft tail ends. They have a much smaller diameter on the stub than regular tail ends (you can see the drill bit still sitting in the tailstock chuck):

I put an o-ring on it and slid the pumping barrel over the piston while it was still in the lathe, just as a quick check to see that I was on track. Here's a closer look:

Parting off the finished piston from the rest of the stock:

The white piston is Dima's original one and you can see how small the stub on the shaft tail end is:

My first muzzle set from him had tail end stubs that were slightly larger and the hole in the white piston reflects that. But on the second one, Dima had reduced the stub diameter. I think to keep more material at the very front of the piston in the shooting barrel which takes a beating as it rams into the shock absorber. I like the idea of that change as I have broke pistons in Mirages previously. My new pumping piston, the red one, has a reduced bore to better fit the newer version of the tail ends:

I went with double quad rings for seals on this piston as the final pic below shows.
That's about as safe as it gets with four sealing lips vs. the 1-2 I have had on previous pistons. Any increase in friction wont matter here:

I didn't chamfer the top of the piston on purpose. I want as much surface area on the front of the piston as possible as the flange (a stainless steel washer) it rests on in the nose cone is quite small. Being that the piston is made of plastic the sharp edge shouldn't really scratch the inside of the barrel either.

Next up: I am pretty much ready for a second attempt at putting this gun together, I am just waiting for some slightly bigger o-rings which I hope will take care of the leaking front. That leaks was either the front o-ring on the shooting barrel or the piston leaking and the new o-rings will hopefully deal with the first of those two scenarios.

Nice work and excellent images!

 

[Diving Gecko]

Nice work and excellent images!

Thanks Tomi!

As for the images, except for the two pics of the gun and fin on the floor all the images are from my phone. I think I have mentioned it before, but i just use a small video light and try to position it so that it shows the important features the best. These lights throw quite harsh shadows and since the dynamic range (the ability to "see" into shadows and highlights) is limited on these smartphone cameras I tend to hold up a white piece of paper opposite the video light. That throws back some of the light and softens the shadows so that more detail is visible in them.
And then I try to keep the "background noise" minimal - meaning I try to eliminate things in the picture that doesn't help add information. Often it is just a question of moving the part or camera (phone) slightly.

 

[Diving Gecko]

Second Assembly
It still leaks...:-(
At the first assembly, it leaked in three places: The trigger, the power regulator and the nose cone/piston. Now, it leaks a tiny bit at the trigger - even though it is a new bushing - and it still leaks at the power regulator, though much less. The nose cone doesn't leak any longer, so I reckon the slightly bigger o-ring took care of that and the piston was not to blame. Though I am disappointed, I guess I made progress.

Trigger Bushing Leak - The Handle Fixture
I'll battle the trigger leak first. This time, I identified the leak to be from the outside of the bushing and after inspecting the bore in the handle I think that's where the culprit is. The bore is actually pretty scratched up and the only thing I can do is to bore it to a slightly bigger diameter. To do that, I need to be able to hold the handle perfectly level so I set out to make a fixture that can achieve that.

I think the pics will do a better job at explaining it all, though I will add comments.

Once again, I found a good use for the cheap guide rail holders and ordered two of them in Ø20mm. Then I turned down some 22mm alu rod to fit the 20mm bore of the guide rail holders and down to 18mm to fit the inside of the handle:

I threaded each part of the rod. One part of the rod inserts from the front of the handle and it's a very tight fit. The other end, with the male thread, inserts from the rear, like a pump valve:

When the two parts of the rod screws tightly together, they keep the handle from rotating:

The brass rod is a tight fit for the existing bore and will serve as a "guide" for when aligning the handle with the bench drill:

The idea is to insert the guide rod in the drill chuck and fine tune the fixture angle until I can exchange the rod for a slightly bigger drill and enlarge the bore in a concentric manner:

Up next, of course, is to do the actually drilling. I am hoping I can get away with enlarging the hole by just a few 1/10mm. Then possibly, I can still use the bushing I made not long ago. Otherwise, I will just have to make a new bushing, too.

As for the power regulator rod, I am not 100% sure why that is still leaking though I am not too nervous about that yet.

 

[Jegwan]

Simply amazing work. Awesome!

 

[Diving Gecko]

Simply amazing work. Awesome!

Thanks my friend
It's slowly getting there and once it is, I'll go back to fine tuning the long one. Stay tuned...;-)

 

[Fibonacci]

Interesting project and some nice machining there Gecko
I've often wondered why there is not more cross-over between bow fishing gear and pneumatic spearguns... seems to me that there are several similar design requirements.
Some of the high performance solid 5/16" (~7.9mm) pulltruded fibreglass/carbon composite 32" bowfishing shafts could be adapted for a lightweight pneumatic travel gun... not sure how much performance you would lose with the lighter shaft mass vs stainless steel but increased velocity should enable a flatter trajectory as a trade-off?