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Discussion Starter · #1 · (Edited)
(I haven't found much info on this so I thought I'd start a build thread sorta thing, moved my post here). So I got an apache innovations tappetless cylinder head, probably will be a waste of money but should be interesting to try out. Supposedly this holds up to 75 rps while maintaining consistent fps. Here's what came:
View attachment 280739
And here's the cylinder head disassembled:
View attachment 280740
So apache included 2 springs and 2 (sorbo) pads of varying thickness for piston head shock absorption and AOE correction. They seem really thick, I feel like AOE might get thrown off as a result, but we'll see. The apach cylinder head works opposite the way a traditional tappet would work. Instead of pulling the tappet forward to bring the nozzle forward, the spring keeps the nozzle back in resting position and only goes forward when air is sent through.

The nozzle is adjustable and screws on and off the silver base. You're supposed to loctite it when you figure out optimal length but it's too loose to hold up to testing. I think I'll keep my upper off and manually press my hopup unit against the gearbox and eyeball/feel for optimal length.

Kind of hard to see here, but the thicker pad is a hair thinner than 2 stacked quarters, and the other pad is a little taller than 1 quarter.
View attachment 280741

When I pull the nozzle forward and release it, it's kinda slow going back, picture the handle on a wind up toy spinning after you let it go, that sorta speed. 75rps? Let's just say I'm very skeptical, but I'll get to installation later.

EDIT: pads are sorbo, not neoprene. They are rock hard compared to the thinner ones usually used for AOE adjustment or shock absorption, but are sure better than my piston head slamming into the back of the CNC aluminum cylinder head. They are 2 and 3 mm thick, respectively.
 

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Discussion Starter · #3 · (Edited)
I almost wanna order half a dozen more pistons, and replace my bearings with bushings, the potential damage here could be catastrophic. Here's the thing: I ordered the apache off of brillarmory and I don't know if the one currently being carried is the most updated one. Apache was having an issue with something, I forgot what, and updated the design recently. Also if this thing can function at 75 rps, where the heck is that video?
 

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I did a wee bit of research and found a Reddit post/decent video showing that the Apache nozzle would stay extended if your piston remains at the front of the cylinder instead of precocking a bit. This was two months ago

I did check mine (ordered direct from Apache this month), which has a different nozzle design, and it did not suffer this issue.
 

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So, the nozzle does cycle normally, and it in my test it actually cycled extremely fast. Fast enough that my iPhone camera doesn’t catch it.

However, this was just a “mechbox-N-motorgrip” test. I’ll have to reassemble before I know how it actually feeds.
 

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I got one of these tappetless cylinder heads the other day as well.
I installed it. To get the correct nozzle length, I measured the old air nozzle length while it was in the gearbox. So fully extended forward.
I then put in the Aztech Cylinder head, but I put its inner spring in behind the nozzle and so the air nozzle was fully forward. Then I installed the CH into the GB. From here I was able to adjust the air nozzle to the exact same length as the previous one and thread lock it in place. Once done, I pulled the Aztech CH apart and put the spring in front of the air nozzle so that the air nozzle would be pushed backwards (this is the correct way to install the spring).
My gun is a DSG and shot at 1.13 joules but with the Aztech CH, it was only shooting at 0.6j. So, a big loss. I did fiddle with the length of the air nozzle but the best I could get was 0.6j.
The Aztech CH does take some of the air in the cylinder to push the air nozzle forward and with my gun being a DSG, I feel it does not have enough air. DSG being that is only pulls the piston back halfway.
My feeling is that, to get high RPS and good fps, you would need something like 12:1 or 13:1 gears with a strong brushless motor and a cylinder that is 3/4 length ported. This will give you the cylinder volume needed and the motor power/speed to get up to the desired high RPS.
 

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My gun is a DSG and shot at 1.13 joules but with the Aztech CH, it was only shooting at 0.6j. So, a big loss. I did fiddle with the length of the air nozzle but the best I could get was 0.6j.
The Aztech CH does take some of the air in the cylinder to push the air nozzle forward and with my gun being a DSG, I feel it does not have enough air. DSG being that is only pulls the piston back halfway.
Yup they're pretty upfront about the FPS loss from what I've seen. Your other option is a stronger spring and/or 9tooth DSG, though an SSG is probably a lot easier.
 

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They are upfront about the FPS loss, but, and I might be crazy here, I want to say they have something out saying that the FPS loss ‘should’ only be around 15 FPS on a full stroke SSG.

The most extreme I’ll be testing in the very near future is 36-37 RPS on an SS’ed SSG, but if it turns out okay in any sort of way I’ll probably be able to test on a full cylinder/full stroke SSG to get some more data.

@1tonne any notes on the feeding or nozzle return time?
 

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Nozzle return time seemed fine.

The DSG will amplify the fps loss. This is because in a DSG, you need all the air to push the bb through the inner barrel (190mm long). In a SSG setup, you have excess cylinder volume and so the loss will not be as dramatic.
In 2 weeks, I will be doing some more testing and experimenting.
 

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An even shorter barrel than that might be necessary for a DSG with this head. It’s possible you had just enough volume, or just a tiny bit short with half the cylinder for the 190mm, and whatever you lost put you in the range of creating some negative pressure, and thus dramatically decreased FPS. I’m guessing you were running a 6.01?
 

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Yip. 6.01mm. But I don't think that AEG's do negative pressure because as soon as the piston is finished moving, the air nozzle is releasing, letting air in the rear (I could be wrong)
Bolties do cause negative pressure though.
 

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Ok y’all, first test results from my Aztech are in.

I ended up just putting together a quick DSG build, since I’ve been wanting to do at least one (to say I’ve built a functioning one :p), and I wanted to test out a 38 TPA motor I had lying around.

Here’s the cheese;

Since it’s a 16:1 DSG with a 10T bevel and 38 TPA 15K motor, the ROF isn’t really that high. It’s higher than you’d normally calculate for the components, since the motor runs so much closer to unloaded speed, but on a 4S it‘s below 35 RPS. Though the head did work as advertised with proper nozzle movements, ultimately, this wasn’t a great test of feeding at high speeds.

I did have to modify the hop unit, since the nozzle was catching on the top of the chamber and not returning. I suspect this is because the gearbox I’m using is not original, even though a regular tappet setup will still return fine. I’m using a Classic Army X9 with a modified E&C GB shell. Squad144, if you’re reading this, then yes, I DSGed your X9. :p

Here’s where it gets interesting. My spring is a Systema M140, which realistically is more like an M150-60 thanks to the way Systema makes/made their springs. However, I’m only getting about 150 FPS using .25g BBs, which is consistent with @1tonne ’s findings.

For reference, I’m using the stock 150mm barrel that’s been polished and had the front modified a bit, along with a mad bull red shark packing and a prometheus purple nub. Thanks to the barrel, the accuracy is mega crap. Like, really trash. (A different barrel fixes this completely)

Let me know if there’s anything else I should look at while I have this setup put together.
 

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I may be asking for my money back from Aztech, given that this head on DSG setups seems to reduce air volume by so dang much.

They give disclosure that FPS should drop by about 15, but it ‘should’ be no more than twice that on a DSG setup. Something about the pressure wave is causing DSGs to lose more than they should.

I’d also like to test on an SSG that’s setup for optimum air volume to see if I lose more than usual. I have a theory that the Apache head actually reduces usable cylinder volume by a great deal more than the small percentage suggested by “15-30 FPS”. However, since many AEGs are overvolumed, this isn’t standout until you get into a setup where how much air volume you have to work with affects everything to such a high degree.

Thus, we should see a big FPS loss in; DSGs, other guns running half cylinders, and guns on the edge of being undervolumed, such as; full cylinder, 380mm barrel, .38g BBs.
 
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