Tech Advice

[Earpy69]

I’m looking for some advice on upgrades. They have already been fitted and seen firing but wounding if there could be any issues.

SHS 13:1 Gears.
SHS Anti reversal latch.
Rocket Red O ring nossle 21.4mm CNC.
Rocket Red ported piston head CNC.
Rocket Red Double O Ring Cylinder head CNC.
Rocket Swish Cheese light weight piston (Full steel teeth).
ASG 34K high torque motor.
SHS shims.
Sanded and polished the inside of the gearbox
Reshimmmed Relubed.
Perun ETU ++.
Teflon tape around bucking and barrel to eliminate any air loss.
Polished the inside of the stock cylinder 15mm port.
Material added to stock trigger to shorten trigger pull.
Carbon Wrapped gearbox.

 

[Colin Allen]

There shouldn't be anything there that would cause a problem; it is all pretty standard.

However, the aluminium cylinder head and piston head combination is not a great idea as it transmits a lot of impact to the gearbox, potentially leading to cracking.

Have the front corners of the gearbox, where the cylinder sits, been radiused to reduce the risk of cracking?

What is the purpose of the carbon wrapping on the gearbox?

I am not a huge fan of full steel toothed pistons; polymer toothed ones act as a "mechanical fuse", protecting the rest of the geartrain if something does go horribly wrong.

 

[Skara]

Echoing what Colin said, I'd drop the alu nozzle for a POM one (does much, much less damage to the hop/barrel assembly if not properly aligned).

Also depending on the spring, battery and achieved RPS you may want to knock off a teeth or two off the sector gear to avoid PME (sector gear engages the piston when it's still traveling forward).

Other than that, it's a pretty vague list since you didn't tell us what you wanted to achieve

 

[Earpy69]

Been offered it in a trade, as I’m not techy enough I just wanted so opinions. As for purpose it’s a arp9 that will be ran 90% semi

 

[Leo Greer]

That setup is a recipe for serious issues without good teching and modification to go along.

First off, unless short-stroking and a heavy spring is involved, that setup IS getting heavy PME on auto, as well as tappet PME being likely. If he can't explain the mods he did and show the RPS/consistent FPS on a chronograph, he's lying. Assuming the setup isn't horribly put together, that's a 35 RPS setup. That combo probably needs to be SS'ed 3 and run with an M120 for y'all's FPS limits, but even that is cutting it close with PME.

Most of those compression parts aren't really upgrades over stock G&G parts and introduce the chance that they'll introduce fitment issues. Yes, even between Rocket/SHS parts.

Aluminum piston head... no. Not suitable for high speed due to additional weight and rigidity--aluminum, being much harder and more rigid, puts more stress on your gearbox when smacked into the cylinder head repeatedly.

O-ring nozzle. Not horrible, but aside from the issues mentioned o-ring nozzles tend to be rather wiggly on nozzle tubes, leading to inconsistent shooting and the potential of compression jams if it's too wiggly. O-rings were originally added to nozzles in order to solve tolerance issues between manufacturers, and not to seal things better. By the laws of fluid dynamics pressure an o-ring on the nozzle is practically useless.

Where was the sanding and polishing done? Aside from the piston rack there is zero reason to polish anything in the gearbox, and if he didn't coat the box it'll likely tarnish over quickly.

I can get behind the polished cylinder. That's a good mod. But a new cylinder in the first place is useless.

For reference, I do a fair amount of work on guns with setups like this. One is even a 13:1 35K build with a 150mm barrel, so I'm experienced with the possible issues here.

Also, unless you're a great tech already and you just want the parts, I'd ask for a video of the build shooting in full auto into a chronograph for at least a 2-3 second burst to let you know if there's huge PME or the seller grenaded the gearbox.

I had a seller on another forum post a build just like this for 1000 beans... with a gearbox ruined from the PME.

If I were buying/trading for this I wouldn't pay more than the stock ARP-9 + that motor and ETU cost--all the compression parts are useless money.

 

[Rogerborg]

What is the purpose of the carbon wrapping on the gearbox?

[Skylar has entered the chat]

Are you having any issues?

 

[Colin Allen]

[Skylar has entered the chat]

Are you having any issues?

Not at the moment, Skylar; I resolved a feeding issue last night.

Oh, by the way, I burned your patch.