Old clear gearbox question

Got one of these I’m doing up for a friend. What kind of punishment can the clear shell handle? I’m not going overboard. Just my usual 300fps build using nylon gears. Just don’t know a lot about the stuff before nylon.

Aside from the vector 300fps + acrylic won’t last long. Be prepared to tell your mate “all care, no responsibility” when you hand it back.

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My original thought was to just get a full gen 8 nylon box and build it up from there. But nylon boxes atm are a bit rare or expensive. But if I can use the one it has it’d be nice cause he’s on a little bit of a budget. I’m more just chasing what kind of spring those old boxes can handle ect. I’d imagine it should at least handle an m90. Their not that fragile surely? (I’m replacing the internals for nylon to get rid of the abs plastic.)

(You also forgot the aug with your vector comment.)

I think its possible to get it to last a while if you build it right, good seals and VE ratio to prevent hammering.
I would not use an M rated spring, the gen8’s don’t like them and prefer the shorter springs especially ones that are gentle on the box such as the 1.18 Ausgel or the CHGBB .
Also don’t go overboard on rof .


I was thinking my usual setup of 1.18 spring. 7.3id barrel. And seals. It’s all I usually need for mine to hit about 300. He wants it set up for 11.1v which honesty was my concern.

What’s VE btw? I only came into the sport when nylon was starting to become metal boxes so I know very little about the tolerances of the early stuff.

Edit: this all might be moot now anyway. Just found a nylon box for $35 :grin:

Volumetric efficiency, cylinder to barrel volume ratio, if you keep it to around 1.6:1 or so it will be very gentle on the front of the gearbox .

11.1v shouldn’t be a problem as long as you don’t use a high speed motor


Nah most is staying stock (nylon stock anyway). Just tweaked to work better. As to the barrel it’ll be a full cylinder with a 330 7.3 of barrel. What I have for my acr and j9. Seems to be a sweet spot for me.

That’ll teach you to be helpful. :stuck_out_tongue_closed_eyes:
The clear boxes tend to age and discolour/crack faster. Just minimal elasticity in the material.

Don’t open up too often or overtighten or the screwholes will also chip/crumble.

If you’re making the box work harder, pistons with cushions, usually advertised as ‘quiet’ can help reduce the effects of repeated impacts.

Ok well your not looking for advice so I’m out !
Hundred of hours of repeatable testing shows 330 on a 7.3 barrel is 2.2:1 ratio and is a gearbox slapper, you may get good performance bit could get equal performance without hammering your gearbox, if you use that you can kiss the acrylic box goodbye in short order, good luck :+1:


Definitely second Rattler on that. :+1: The clear acrylic boxes don’t last long if you go to town on power. I wouldn’t use anything bigger than a 1.18 spring in it and a cushioned piston head. Your best option if you want to get it right is to keep it in the mid 200s and concentrate on your efficiency.

Then it’ll hit hard enough, be accurate and should last long enough to guarantee your mate’s not knocking on your door in a week or two with a broken box. :+1:

If you’re starting to do builds for other people, free or paid, mate or not, you’ve got to be able to give them reliability and some longevity. :+1:


I agree completely. It’s why I thought I’d ask here on their tolerances. The main issue really was that he’s got a pretty small budget and I was trying to fit it without going over.

@Rattler sorry and thanks :stuck_out_tongue_winking_eye:. 300 was the goal. But if I had to use the clear box I think I would’ve went down on fps. It’s already doing 220 but the main goal my mate wanted was to be able to use an 11.1 in it. (He’s trigger happy and it’s for a saw so decent mag size) which I think even at that fps would’ve broke the box pretty quick with the fire rate. (He wasn’t wanting anything supper fancy and metal is just out of his price range if getting a metal gen 8 is even possible? )

I found a nylon gearbox for $35 so I’m going to get that and build it up from there. It’s a damn side more reliable than that clear box that’s for sure.

Thanks guys :grin:

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Good decision… keep the clear box for another build. :blush:

@Rattler one thing I am a little confused on though. Might be a bit of a obvious answer though. I know about the volume ratio and how all that works. But how would it increase the stress on the front of the box. I thought it’d be how hard the plunger was hitting the front and the resulting shock. Not how much air is being pushed though?

That’s the thought. Though. It’ll probably sit in a box till I forget it’s there along with all my other bits and pieces. Starting to get quite a bit of a collection :joy:

I wanted to go the nylon box from the start but the cheapest I could find that was in stock was about $60. Which with the other little bits he wants would’ve been over his currently strained budget so atm kind of made it out of the question. He could’ve waited but he’s a little like me and impatient :joy: and he’s helped me out when I needed help pretty badly so I do owe him.


If you use too much volume the gel leaves the barrel before the piston is home, now the piston has no compression so speeds up and slams home just like a dry fire


Ok I didn’t really think about that :thinking:. That actually might explain a few curiosities I was having.

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You’d be suprised at how much quieter most blasters are when you get the VE right.

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Yeah it was never really a consideration for me tbh. Though it likely explains why my aug is so quiet with a 1.7:1 ratio. Add one of the mock suppressors giving it just a small baffle and you can’t even hear it on 7.4v. Switch to 11.1 and you can hear it from about 5m but that’s about it.


I like quiet. :sunglasses:

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