High ROF - Short Stroking Advice?

[webbjay]

Right guys,

I am going for a high speed setup with the following components:
- Modify 16.32 High Speed gears
- Modify polycarbonate piston
- G&P M120 motor
- Systema high speed cylinder set (with polycarbonate piston head) matched to my barrel length (285mm)
- Sorbo pad
- 9.6v 2200 mah battery

Now, I do not know what spring to go for and how I should go about short stroking? I want it around 310 fps and I know that with high ROF setups, a stiffer spring with a short stroked piston are advisable to prevent premature engagement.

My dilemma is that apparently the Modify gear set is rated to an m120 spring, but I don't want to push them that hard. I was thinking of using an m100 spring and short stroking the sector gear and piston by 2 teeth. However, will this be enough to give me the desired fps?

Cheers!

[jagillham]

Re: High ROF - Short Stroking Advice?

The whole point of the bigger spring is to get the piston back in time. Fit it as is, see what the FPS is, then remove teeth to bring down to required.

Why the nihm....?

[webbjay]

Re: High ROF - Short Stroking Advice?

Yeah I get that. In an ideal world I would like to run a 1J spring without short stroking but not sure whether I would get pre engagement. For this I was thinking the M100 and short stroking. I just wanted to get peoples opinions on whether the former would likely be OK (to avoid having to mess about modding the piston) or whether, as you suggest, go for the stronger spring and short stroke to be sure.

As for the nimh, I am just getting back into airsoft after 4 years out and just using what I know atm. May change to lipo in the future though!

Cheers mate.

[jagillham]

Re: High ROF - Short Stroking Advice?

The short stroke is to keep FPS down, but with the piston speed still high.

M120 short stroked to 310fps is same strain on GB as M90...

[webbjay]

Re: High ROF - Short Stroking Advice?

Think I am going to go for a Guarder SP90 and see how it goes. Generally, with a good airseal, people seem to get about 330-340 with it and so short stroked by 2 teeth should be 310fps. Hopefully this should avoid any pre engagement and maintain piston speed. What do you reckon?

[RedHawk]

Re: High ROF - Short Stroking Advice?

Don't use a G&P M120, it's an alright motor but you can get much better motors for half the price with twice the power. A rule of thumb is that in any high speed setup, you want a high torque motor. X-HighTech's Turbo High Torque Motor works really well and costs £15 posted from China. It uses neodymium magnets which are exactly the thing you want in such a setup.

[webbjay]

Re: High ROF - Short Stroking Advice?

Thanks for the reply mate. Was looking at getting a high torque motor but just using the G&P M120 at the moment as its the only one I have and I'll see how I get on with it. I'll have a look into that motor though!

[jagillham]

Re: High ROF - Short Stroking Advice?

Might find the G&P M120 struggles a little.

You still want the higher rated spring.... as getting that wrong one means you'll potentially strip the gears and piston.

[webbjay]

Re: High ROF - Short Stroking Advice?

I see. Ill give it a crack and go from there.

Do you think an sp90 with 2 teeth off the piston and sector gear will be ok?

[Bachelarius]

Re: High ROF - Short Stroking Advice?

There's no harm in getting something heavier and using a combination of a small spacer and short stroking to fine-tune the FPS.

I honestly believe you will end up with lower FPS than that (sp90 is advertised as ~315, two teeth less and you'll be in the 280s!)

I'd personally start with an m110. Chrono. Take off 1 tooth. Chrono. Take off another tooth. Chrono.... and so on.

Having said that, you probably won't get the most amazing ROF with that setup anyway, mid 20s if you are lucky, so PE won't be a huge issue and you may well scrape through on the sp90. But why not just go for the sp100 or higher and save the risk and hassle?

[webbjay]

Re: High ROF - Short Stroking Advice?

I would be quite happy with mid 20's to be honest! Think I may go for the SP90 and short stroke by one tooth at a time as you said. May only need to do one tooth then. Would the SP90 help the G&P motor as well or will the motor only really struggle when compressing the spring fully?

It seems there is little consensus about the FPS of guarder springs as alot of people say they run quite hot and I've heard of alot of people hitting 340fps with an SP90. Even if it goes to 300 I won't be too miffed as I play CQB and will at some point install a tightbore.

Cheers for the inputs!

[jagillham]

Re: High ROF - Short Stroking Advice?

Guarder do come in hot, SP90 will give around 340fps as standard.

Still not sure why you refuse to use the higher rated spring? Makes much more sense!

Motor wise... the SHS high torque is a good option (I found the G&P M120 getting very hot). I'd drop the Systema cylinder set. Not needed, and I expect quite expensive?

[webbjay]

Re: High ROF - Short Stroking Advice?

I have no problem using the higher rated spring but if I am going to be getting around 25rps as Bachelarius says, PE shouldn't be too much of an issue and it'd be easier to short stroke by 1 or 2 teeth than it would be by 3 or 4 teeth, if i was to experience pre engagement. And it'd be easier on my current motor so to me, unless i'm missing something super crucial, it makes as much sense.

I have actually looked into the SHS motor as alot of people seem to use them. When funds are available I will assess that situation. The Systema cylinder set was actually reduced to $30 from WGC and it matches my barrel length exactly. It includes the very good black polycarbonate piston head too so I thought i'd go for it!

[jagillham]

Re: High ROF - Short Stroking Advice?

Short stroking just as easy to do 1 tooth or more. You need to decide before you run it really. You got a half metal rack piston?

25 bb/sec... might be able to get that. You'll need to be careful of angle of engagement etc though.

Up to you with the spring, but one pre engagement could cost £50+ damage. Getting a M120 or SP110 etc is £10.

[laurence]

Re: High ROF - Short Stroking Advice?

If your gonna get another motor, just get an Element, they're very good