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

Thanks so much for the words. I honestly don't feel like my work is at a level yet where others should have to pay. Also, the knurling on the caps is still a bit wonky. Sometimes it works out great, sometimes not. I think that will take a while to learn. If I do make a batch, I'll drop some in the mail for you and you can buy me a flat white if I'm ever in your city. No promises, though as some real work, holidays, travel, etc is coming up.

Great tip on the 8mm diamond ball cutters. I did watch a few stippling videos on youtube (the gun guys using soldering irons on their Glocks) and liked the pattern. But then I went with an epoxy handle and thought I couldn't stipple it and carbonium covered it instead. Stippling with a diamond cutter could have worked. The small ball "router bits" I sometimes use on the Dremel are hard to control. They can dig in pretty deep all of a sudden so it's great to have this option for finer work.

But perhaps for a standard plastic handle on a Predathor you can use either the ball cutters or a soldering iron.

A Study in Scarlet O-Rings - A Bit of Sherlockey Work
In preparation for fixing the internal leak I wanted to figure out what size rings these are, but trying to measure my old o-rings posed a challenge. Here are some from two guns from the bulkhead and pump inlet valve...:


For comparison, here is one of the funky seals with two regular o-rings:


Honestly, the first time I came across these seals I thought Mares might have used some proprietary flat-concave seals in the bulkhead and I feared I could never find replacements for these. But as most of you probably recognized, those pics are of what used to be a nice circular o-rings. They are just deformed like crazy now. When I realized that, of course, I was relieved as I could set about replacing them - just needed to find the sizes.
But nothing is supposed to be that easy...

I started looking at the old Mirage manuals and the exploded diagrams to look for clues on the sizes. Pete has covered this in the past but I had somehow forgotten about that (just found it again yesterday) and it is amazing how the Mirage has changed over the years. It's also quite confusing;-)

In the first version, an AMF-Mares gun, going by this scan of Pete's original manual, the trigger o-ring uses one type of o-ring (OR 1) while the o-rings in the one-way valve, the over pressure valve and the pump inlet valve uses another type (OR 101):


In the next version, also an AMF-Mares branded gun, the same separation between two types of o-rings is present. But while the trigger o-ring stays the same (OR 1), the o-rings for the one-way valve, the over pressure valve and the pump inlet valve change to another spec from OR101 to OR2012 (Pete says it is an increase in hardness change):


In what I think might be the latest version from a 1989 Mares-only branded manual (thanks Jegwan), the o-rings in the one-way valve, the over pressure valve, the pump inlet valve and the trigger are now the same spec - and they stick to the so-called 'OR 1' o-ring. Perhaps, Mares wanted to simplify the assembly:


Now, here's the thing. Mares never gave out the sizes of all these rings... They just gave these random parts numbers that I couldn't cross reference or relate to any real world sizes. At least I thought so until last night when, once again, I was roaming online. I don't know why I never thought of this but there's actually an Italian Standard for o-rings called UNI and... most of the Mares o-ring "part numbers" corresponds exactly to that standard!

Here's a screen shot of part of the list:


I was pretty chuffed when I came across that list, to say the least. For years, I have been pissed at Mares for not letting us know what their o-ring sizes were and then it turns out, they weren't really keeping secrets. Just sticking to a weird, old, illogical naming standard... haha
(I am making a spreadsheet with as many of these relevant sizes as I can - will share it in a new thread in a few days)

You would think this solved it, right? As e.g. the OR2012 ring is given as a 2.9 x 1.78mm (ID x W) according to the Italian UNI standard. That is a very regular AS568-006 o-ring that I have plenty of. But remember, Mares changed all those four seals to that strangely named 'OR 1' in the latest version (in some Mares manuals called OR R/1) and that is nowhere to be found in the Italian standard. Now, I actually speculate that that could refer to another standard, this time the French R O-ring Standard where there is an o-ring called R1 which is close enough in size that it makes sense (2.6 x 1.9mm):


So, I think I am getting there. It took a while and maybe I am taking a wild guess on the French R series but perhaps not.

Finally, there's also an important question of hardness as Mares have used different hardness of seals in different positions over time. But that is the next challenge.

Fibonacci said:

Some really good research there Gecko, Mares mystery solved and a very useful resource!

I had exactly the same problem when restoring a Nemrod Clipper... I removed a recessed donut seal from the inlet valve and was poring all over the internet trying to source them.
Closest I got was square edged o-rings till like you I reached the 'aha' moment and realised they were just standard o-rings that had distorted under load!

Regarding o-ring softness, when overhauling SCUBA gear the general rule of thumb is 70 DURO for low pressure (LP) dynamic o-rings (~120-160psi) and 90 DURO for high pressure (HP) static seals (~2250-3500+psi)

Click to expand...

I might just have re-found something that others already knew, but I don't think I had seen that Italian/French Standard connection before online so it was indeed a bit of a Eureka moment.

As for the hardness, good to know that rule of thumb. I think Mares specified 75 for their slightly harder seals. At least it says SH75, where I guess they mean Shore 75 hardness; Pete has pointed that out earlier. too.

It is easy for me to source most of these seals here in China cheaply but getting any specific non-standard hardness may not be.

Lathe Update - No Speargun Parts
It's been a bit quiet in the Home Machine Shop lately. Some real work came in, which is good, because something's gotta pay for this little hobby;-)
While I haven't been making parts, I have made a few improvements to the lathe. I mounted needle roller thrust bearings to the leadscrew, changed most of the screws to stainless and I gave it an overall CLA. I also made a very simple carriage lock which clamps the carriage down on the ways firmly for parting operations.

And I bit the bullet and got a new quick change tool post. The first one was in alu, it was soft, sloppy and barely OK for work on the softer alloys. The new one is hardened and ground steel (I think) and uses a wedge system instead of a piston. Just feeling the weight of it is assuring:


It's basically a down-sized AXA tool post (this baby size is actually called OXA):


I mounted it and did some test cuts and it's much sturdier:


The parting is better, and the grooving, too which is much needed - it is no fun doing an o-ring groove and getting chatter - and the resulting marks - just as you hit the right dimension. But I think the improvement for boring operations is even bigger. The old holder was a really sloppy fit on the tool post and would jump if I looked at it funny which meant I had to take really shallow cuts. With this one, I literally just took a 2.0mm cut in 6061 alu! That's a 4mm increase in inner diameter of the part in one cut. It might be some really soft Chinese alu but nevertheless I am impressed! There's no way I could even have done half of that on the old tool post.
Here are some fat chips (though I still can't get them to break):


You might have noticed the little caliper mounted to the left of the cross slide (it reads 0.99mm from a test cut before I gradually increased and stopped when I got away with 2.0mm cuts):

It is my poor man's DRO (Digital Read Out) and it is incredibly helpful and cheap as... chips. I made it a while ago after having stumbled upon the idea browsing machinists forums. It's made out of a short caliper used to measure tread depths in tires. Since all this stuff is made here in China, I can get these easily. I think I paid less than USD5 for one of these (I got two).
I whacked it together real quick and ghetto style: Glued some magnets onto the back side (the other caliper has larger magnets) and stuck a magnet to the compound, too which interfaces with the caliper rod at the front. The ones I took inspiration from are put together nicer but the idea is the same.



I also made one that attaches onto the ways to give me readings on the carriage movements (I guess the Y axis):


I wasn't sure how much I'd like these but the resulting precision is surprisingly good and they really help you work faster. In fact, I like them so much that I just ordered some more DIY goodies in the DRO department. Here's a teaser...:


P.S. I got stuck with the o-ring spreadsheet but will probably share what I've got sometime during the holidays when it is tidied up a bit more.

Happy Holidays to all of you!

More Lathe Stuff - TouchDRO App
Since the rest of the parts came in this morning, I might as well reveal what I was teasing yesterday;


It is a Digital Read Out made up by a cheap microcontroller with a Bluetooth module which beams data to an App running on an Android device to give you a very affordable and capable DRO setup.

All this is possible because of the amazing Yuriy Krushelnytskiy (read more here) who wrote the firmware residing on the controller chip and designed the beautiful App for the tablet. And... it's all free! He does offer his own pre-made controllers, so with those the only thing you have to do is to get the scales and find an Android device. They are very reasonably priced, too.

But I wanted to do it on the cheap and liked the challenge. The microcontroller is about USD 10 and is Texas Instruments' take on an Arduino (though not compatible). The Bluetooth module was about USD2. I had the tablet for flying my drone so the only real investment I had to make was in the scales. Yuriy's program accepts many sorts of scales from cheap Chinese calipers to expensive glass scales. I found some scales that are rebranded in the West and got them even cheaper here (though they are still not bad in e.g. the US). I paid USD 55 for a 500mm and 150mm one - more than sufficient for my carriage and cross-slide. Add another USD 2 for a hall sensor module so that you can hook up a tachometer. I spent a bit on a mounting system for the tablet, too.

I haven't attached the scales to the lathe yet. Need to think the mounting over so I don't mess it up. But making this work so far wasn't that tricky. Yuriy has good build instructions. Two things posed challenges, though. First of all, I suck at anything PC. I have been on Macs for too long so programming the chip on the controller was an adventure (no way to do it through a Mac it seems). A PC guy would probably have less issues. Secondly, I just couldn't get the Bluetooth to work. Turned out it was a faulty module. I got a new one, hooked it up to the board and connected the tablet to it right away. The scales work perfectly so far, but the tachometer has an issue. But I'll probably get that to work down the line.

BTW. His app does work with Arduino, too - but he hasn't upgraded the Arduino firmware in a long time - but another guy has taken that firmware up to date.

Yesterday, I wished you all Happy Holidays but I'll give a shout out to this amazing thing we call the Internet;-) Without it, I wouldn't have started cutting metal and making my own speargun parts and without it TouchDRO probably wouldn't have existed. It's just amazing how much knowledge is being shared and how it helps support the cottage industries like never before.

A Mod Out of Necessity
Holidays are over but the real island holidays are fast approaching so I need to finish up my guns.
Now, this is a tad complicated but I have two amazingly well made vac muzzle sets from UBL/Dima. One is what he calls The Universal set which can take shafts up to 8mm. The other one can only take 7mm and smaller. Normally, I would just use 7mm shafts on this 93 size gun but I want to test it with 7.5mm and 8mm shafts, too. Perhaps it has enough power for those.
Now, I could just mount the Universal muzzle but I want that to be on my 125 gun to shoot thicker shafts on that, too. And unfortunately, Dima is traveling these months so he can't make me a new muzzle.
I really like Dima's design and parts so I decided to modify a stock Salvimar Vuoto muzzle to work with his tail ends and tiny sliders. It does make me feel a bit weird, a bit like violating his work, but it's the only option and I will order a new muzzle from him as soon as I can. I don't feel half bad cutting up a Salvimar muzzle which I feel is a slightly compromised clone of his original design.

My mod ended up looking like this:


It was a simple matter of cutting an internal thread and making a screw-in bushing to suit Dima's sliders. I did shorten the Vuoto muzzle a bit as I cut my shafts really short and Dima's muzzles are slightly shorter than the Vuoto ones. His tolerances are tight and when the slider sits in the muzzle, there is no slop at all. This keeps the shaft centered and as a result he can also keep the surface area on the shock absorber up without having the tail end bang into it. Of course, his super slim tail ends help in this regard.


His work, to the left, is beautifully simple and functional. No bells and whistles but still optimized as much as possible, I think.


A fun/frustrating fact is that while the Vuoto is a close clone, I can bust the o-rings on their shock absorber, which has never happened to me using Dima's original design. (This is on the Mirage with higher pressures than in "normal" guns.)

To finish this mod, I need to make a new shock absorber, too with a bevelled flange to match Dima's pistons.

tromic said:

Nice work, David!
Here is for reference my modification too:
https://forums.deeperblue.com/threads/tomba-all-in-one-barrel-sealing.81791/page-47#post-968071

How would you explain this:
"A fun/frustrating fact is that while the Vuoto is a close clone, I can bust the o-rings on their shock absorber, which has never happened to me using Dima's original design."
I have never tried original Salvimar shock absorber...
What makes the difference?

Click to expand...

Thanks so much, Tomi!

I will try to explain it, but it may be hard to visualize. But I noticed that the flange/lip on the inside of the muzzle where the the first o-ring bangs into the muzzle is much narrower on the Salvi muzzle than on Dima's. Also, the gap between the shock absorber and muzzle at the same point seems bigger which may or may not increase the risk of pinching the o-rings.
I have to say that I never had issues on my Stens with Vuoto muzzles but I did break o-rings on the Mirage. So, I was quite hesitant about Dima's design which also uses o-rings. He told me he hadn't had issues on guns with high pressures so I gave it a chance and it has worked without problems.

Just two quick pics as I finished the titanium shock absorber with a bevelled mating flange for Dima's pistons:
Vuoto absorber on the left, my version on the right:


And here one that shows the bevelling and one of Dima's pistons:


Now, I will swap out the o-rings in the bulkhead to see if I can get rid of the internal leak which messed with the whole "Mirage effect". If I succeed in that, I think the gun is ready and I will move on to the longer one to see what can be done to that in the next week or so before I set off to Indonesia;-)

No More Internal Leaking
I managed to get the internal leaked plugged, so the Mirage 93 is now a proper Mirage;-).
I didn't snap any pics and wont have any time to do so for a while, but I will list what I did here and perhaps add images sometime in the future:

• Changed the o-ring in the over-pressure safety valve in the power regulator bulkhead (this should ideally be a harder shore)
• Changed the large, main o-ring on the OD of the power regulator bulkhead
  
• Changed out an X-ring on the shooting barrel where it interfaces with the bulkhead for a regular o-ring
• Changed the o-ring on the power regulator bushing
  
• Adjusted the power regulator brass bushing so it protrudes into the bulkhead slightly more than before
• Finally, for the plastic bushing which sits at the bottom of the handle and mates against the one-way valve for the pumping barrel I made a new and slightly longer Delrin bushing which protrudes about 0.7mm further towards the o-ring than before

Which of these changes stopped the leak, I don't know. To have an idea about that I would have had to do one change at a time and then reassemble, pump up and test for leaks and I simply did not have time for that;-)

I mentioned on the other Mirage thread I had done a rough mod to improve the airflow. Now, I just did the same mod on the 93 gun. It's very simple, just cut out a bit of side wall in the power regulator bulkhead next to the bushing on the power regulator itself. It's hard to explain and even harder to photograph but I tried.
First pic is before I took a knife to the plastic. The wall marked in blue is what I decided could be removed:


After the operation the area is much more open (marked in red):




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marco15499 said:

Hey Gecko! Following your threads!

Now, after all this work in your pneumatics, you're using wood guns?

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No way;-)! How come you think that?

I would love, at some point, though to put an Abellan up against an optimized airgun. I have a friend who has some nice woodies so it might happen at some point.


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marco15499 said:

I don't like Abellans though. They do have recoil. A lot!

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I shot the Albacore 130(?) and it sacred the living daylights out of me. It does have recoil but I think all band guns running three hot bands do and the Abellan is just widely regarded as one of the best optimized ones, so that's why I would love to compare directly against it. I think a long air gun against a Denton 120 would be fair match. But I have been saying for a while that I want to do this test, so let's see when I actually will get around to it. I would need to get all my gun parts back from Bali and then fly south to Shenzhen where my Abellan-owning friend lives. So, let's see...;-)