Emek/Gamma Core Pump - Proof of Concept

[nak81783]

Link to models in post #2.

It might be a while before I can get back on the machines.

[nak81783]

Quick update. Machined another spool housing. Fixed the random hissing and leaking, but it's still a little too snug to spring back forward under air pressure. I'll open up the bores a bit. Hopefully, I can hit the sweet spot where it slides freely, as intended, but doesn't leak.

[nak81783]

Small update. Opened up the bores in the spool. It now resets under air pressure as intended...most of the time. I need to get some new o-rings just to make sure the ones I'm using aren't swollen, causing the occasional sticking. If new o-rings still stick occasionally, I'll open up the spool bores some more.

Played around a bit with routing the hoses. It's going to be tough, but I think there's room.

PE is currently out of stock on Emek trigger frames/lowers. Anyone have one to sell or a boogered up one for testing? I don't plan on cutting into my Etha 3M lower or buying a full new marker to convert to pump.

[RPP]

Inception seems to have some in stock.

[nak81783]

Inception seems to have some in stock.

Thanks, but that's a full/loaded lower with regulator, ASA, etc. PE had some of the empty frames for <$30, but they're currently out of stock.

[RPP]

Thanks, but that's a full/loaded lower with regulator, ASA, etc. PE had some of the empty frames for <$30, but they're currently out of stock.

Ahh yes that makes WAY more sense.

[Bow]

Check out MWR paintball. Its not a 1/1 but his emf frame was the only way I could get an emf lower.

[JohnB]

Neat and I am following this thread. I have trouble calling this and an ion pump a pump in the traditional sense. I guess I look at it how a stock class player looks at open class. It just ain’t right! But they are neat. Good luck with build.

[nak81783]

Update video. Warning: it starts off very quiet and then gets very loud.

https://drive.google.com/file/d/1YCdaZMf1i0-GYTCMObwFdsLGr5MUiI3O/view?usp=sharing

1. I took too much out of the spool housing ID trying to get it to slide smoother. Now it leaks if I tilt the pump handle.

2. I'll need to machine another spool housing and get some tooling to improve the surface finish on the ID. It's not giving me the air spring back that I want.

3. I think I figured out what's causing the low velocity issue (270fps with reg maxed out), and unfortunately, I don't think I can get this design to improve that.

4. I came up with another design that may fix the velocity issue. The good: it reduces the spool to 3 orings, which should reduce static friction, so hopefully this will further help the air spring return. The bad: it will autotrigger on pump stroke return to forward position. I know some like this and some don't. The unknown: it relies on a check valve working as planned. I'm not sure how many cycles these things are rated for. Something like this - https://www.duraprohealth.com/shop/v...ApwxQCI7WyUgac


I also updated the link to the models in post #2. I didn't have it set up for sharing.

[nak81783]

Gosh, I suck at this. Please try it now.

[nak81783]

Edited link again. Hopefully, third time's a charm.

[Pogi Si David]

Very cool

[nak81783]

I’m scrapping the current design. It can’t address the low velocity issue, but I’ve learned a lot from it to carry into the next iteration(s). The two most important lessons learned are 1) the cause of the low velocity issue (The reg must be able to push air into the firing chamber until the switch and spool separate at the spring, which ultimately cuts off air supply to the firing chamber. This scrapped design doesn’t allow this.) and 2) the oring design guide I used was incomplete. This led me to make bad assumptions, which I now know is a large portion of what is causing the pump stroke resistance (air spring effect doesn’t push pump handle forward).

I’ve come up with two new designs. Both only need two hoses going from transfer block to pump spool, which makes internal hose routing much easier. The first utilizes the front air passage in the transfer block and a pressure differential floating piece in the pump spool. The good news is if this is successful, it can be applied to the smaller FL transfer block, not just the original, older, larger transfer block. The bad news is I won’t know if the floating piece will work until I try it, and related to that, I don’t know if it’ll keep the reg supply available to the firing chamber long enough to correct the low velocity issue with the scrapped design.

The second design utilizes the rear air passage in the transfer block, two check valves (like what I linked earlier), and a barbed T-connector. The good news is this will eliminate the low velocity issue in the scrapped design. The bad news is I don’t know if the check valves can handle the pressure or cycles/cycling rate. Also bad news is I haven’t figured out how to get this to work with the smaller FL transfer block.

I’ve got to get some parts machined.

Can anyone on here perform calculations on dynamic parts under pressure, how long to vent, how fast and with how much force the part will move, etc.? It’s been 20ish years since I (may have) had the classes to do that math.

Lastly, I see SSC had a Gamma Core pressure tester but is sold out. Does anyone have one for sale, or does any other company make one? If not, that’s another item I’ll need to make that’ll help with this project

[nak81783]

Here’s a small update.

I had to change oring fitment (stretch and squeeze) again, using a different section of the Parker design guide.

After getting parts machined to this design, the fit/slip feels much better, and it gives me an idea of the pump force and return.

The design using the front channel of the transfer block is no good. The 1/8 OD / 1/16 ID tubing can’t supply enough air during the shot/dwell to reach velocity.

For now, this project depends if the barbed check valves and tee can handle the pressure and cycles for the design which only uses the rear hole of the transfer block. This design will ensure the shot isn’t starved causing low velocity.

Machine time is at a premium. I’m not sure when I’ll get the next set of parts made.

[Jonnydread]

Thanks for the update, I keep forgetting about this then getting excited about it.

[nak81783]

I get excited when the parts get worked, but usually only a lathe or mill is available. Since some of the parts need both, the project can't move forward until machines are available.

I ordered the barbed check valves and tees today. I should have them next week. The parts likely won't be done by then, but I can test the barbed check valves and tees with the parts I do have to see if they'll withstand the pressure. Fingers crossed.

It also doesn't help that I have two other projects going - TiPX upgrades and a mechanical Spyder VS3. I'm trying not to let the newness of the excitement for the other projects make them take priority over this Gamma Core Pump project.

[nak81783]

Another small update. I had to cancel the order for the barbed check valves and tees. The company said they were in stock, but when they didn't ship for a week, I called. They said both parts were on back order. I waited a couple weeks, but ultimately cancelled the order and ordered elsewhere. The parts arrived today.

Good news: The check valves seem to handle the pressure just fine. I disassembled one, and I see no reason why it won't be able to withstand the constant cycling either. Worst case, I have to go to higher durometer seals and/or thread sealant.

Bad news: The check valves are bigger than I expected. This changes how I have to route the hoses. Not a deal breaker, but it will require extra parts and machining.

I'm hoping to have the parts required for a function test the end of this week, but again, I never know when machines will suddenly be tied up.

[nak81783]

Some updates.

1. I goofed on the latest design (I was p!$$ed), so it won't function as expected. However, the parts did let me do some testing; read on.

2. New transfer block design resolves velocity issue.

3. I was able to set up a test rig to cycle the check valves under pressure. They seem to be holding up fine to hundreds of cycles without breaking a sweat.

4. Test rig also let me get a feel for the pump resistance and reset. I don't know if 3-4 lbs is going to offer a fast enough reset. I'm hoping things will break in and smooth out with use. There are lots of oring options for pressure imbalances, but it requires new/modified parts every time.

5. I think I figured out an autotrigger design. It does tap into the front channel of the transfer block (but doesn't cut it off like a previous design), so I hope it doesn't cause low velocity.

Awaiting more parts to continue testing.

[nak81783]

You have my attention and turgidity

Turgidity is again the word of the day. I had some mock up parts resin printed. I got about 20-30 shots out of it before the front 3-56 barb stripped out of the plastic. Non-auto-trigger concept has been proven. Now I'm even more eager to get the machined parts. I may have to still play with oring sizes, oring squeeze/stretch, and hose routing, but it's a huge relief that the concept sealed up and behaved as expected.

I may get the auto-trigger concept parts printed while I wait for non-auto-trigger machined parts.

[Chuck E Ducky]

Did you see the results Brian got from aluminum 3D printing. Might make it a bit easier / quicker prototyping. I’m eagerly awaiting the testing results.