Systema Reinforced Gearbox Breakage!

[jagillham]

Just wanted to share this, and find out if anybody else has seen this happen!

 

Last Jan purchased the Systema reinforced V2 gearbox. It's been running with TM piston/head. Element M105 spring. Running at around 22 RPS, with MOSFET, 8.4v motor and standard reinforced gears.

 

The gearbox has served me well until now, but I took it apart today to fine hairline cracks.

 

Couple of variables here, last week I...

 

- Installed a sorbo pad

- Installed M100 spring

- Had mag (well Z1 .25g pellets refusing to feed!) issues, meaning 50% + shots were dry for a days skirmish.

 

Something has caused this though:

 

 

 

 

Anybody else managed to break one of these?!

 

[Silent_Assassin]

Oh *fruitcage* dont say that! I paid £50 for my GB 5 months ago for my HK416 High ROF project.

 

Josh

[bbondaloose]

So much for being reinforced.

 

I guess since GB are not made of titanium, they will break over time, but it's saddening to see such a famed gearbox for not breaking and quality is having cracks.

[jagillham]

Too right, just was thinking my options really. I was almost a year ago, but then again it was a £50 shell! Wondering if I should speak to the retailer?

[UrPeaceKeeper]

Too right, just was thinking my options really. I was almost a year ago, but then again it was a £50 shell! Wondering if I should speak to the retailer?

 

Round the cylinder windows... for the OP it's too late, the only hope of saving is to drill out the ends of the cracks and pray it holds. For everyone else, rounding the cylinder windows for low FPS set ups should solve this issue.

 

Needless to say this is not the first (closer to the 12th) I've heard of breaking. Systema gearboxes are not bullet proof, and their reinforcement is not enough.

 

The other MAJOR fix would be the use of Sorbo pads to reduce stress on the front of the gun as well as a Polycarb Cylinder head of some sort...

[bjorn]

Helps: Rounding the cylinder cornerts, installing a sorbo pad and using a lightweight plastic piston head, piston and cylinder head.

 

But yeah - defo not the first Systema Reinforced Gearbox breakage seen here as well.

 

Bjorn

[Abelius]

Just have to echo what has been said. Systema gearbox shells are nothing extraordinary, they are about as tough as G&P and CA shells that have identical reinforcement at the front. These break just as much as other reinforced brands, naturally they are stronger than non-reinforced shells like Maruis.

[fossilfuel]

Just have to echo what has been said. Systema gearbox shells are nothing extraordinary, they are about as tough as G&P and CA shells that have identical reinforcement at the front. These break just as much as other reinforced brands, naturally they are stronger than non-reinforced shells like Maruis.

 

 

 

Systema G&P et Al "re - enforced" gearboxes have a little more material in the front end over a TM one but that is all. they have buckets more at the back where it does nothing to strengthen the gearbox. I've had d-Boys and JG shells last as long if not longer than System, G&P or HurricanE aftermarket ones.

 

Rounding the front of the cylinder cutouts helps, as does running a light piston/piston head combo and using a TM style poly cylinder head (which will absorb some of the shock instead of passing it all on like a brass cylinder head.

 

However with high rof - high fps (or both) the repeated impact will cause the shell to fail - it will under normal loads as generally the material used is not generaly high quality. the only gearboxes i expect to last for a long, long time are Pro Win ones (and i'm not an uber fan of them) and the PCGv3 inspired M249/M60 gearboxes as they are massively over engineered.

[Abelius]

Systema, G&P, CA and other "Probox" -types have indeed more material at the front, especially at the upper frame. The "reinforcement" at the back is useless, that's true. I took a picture of my three spare shells I have laying around at the moment. As one can see, even the reinforced boxes are pretty thin at the critical parts, like you said. It just reflects how flawed the V2 design is.

 

The top one is a non-radiused Systema, the middle a radiused CA and the bottom one a black JG.

 

[Bane]

Again just to echo the same sentiment.. the Version 2 mechbox is flawed in its design, it doesent matter how strong your mech is it will break eventually.

 

The big problem you may be having is temperature fluctuations, from winter to summer, massive temperature increases & drops, and use during these periods would accellerate weakening, especially if your in an extremely harsh winter.

 

Radiusing the windows, etc, helps exponentially.

 

One technique i'm finding works quite well is instead of sorbo-padding inside the cylinder, shave some material off the front of the cylinder head, and using a rubber glue fix a peice of sorbo pad between the mechbox and hte cylinder head, and elongate the holes the mechbox lock into so they are more like slots. Doesent hinder any function of the mechbox yet it cusions the force of the blow at the actual transfer point, meaning the cylinder head absorbs some of the blow, then transfers whats left through another sorbo pad into the mech shell.

 

 

Another option, which i know works exeptionally well, is run a slightly heavier spring (Lost yet?) then use a properly tuned air-brake. The stronger spring is to give you the same FPS as before (If your worried about a 10-20 fps drop) and the air brake means the piston never slams hard against the cylinder head.

[jagillham]

Can somebody point me in the direction of how to round the corners correctly?

[Docv400]

One technique I'm finding works quite well is instead of sorbo-padding inside the cylinder, shave some material off the front of the cylinder head, and using a rubber glue fix a peice of sorbo pad between the mechbox and the cylinder head, and elongate the holes the mechbox lock into so they are more like slots. Doesn't hinder any function of the mechbox yet it cushions the force of the blow at the actual transfer point, meaning the cylinder head absorbs some of the blow, then transfers whats left through another sorbo pad into the mech shell.

That seems like a good idea Bane.

 

No matter how 'reinforced' you make a box, if it hasn't got properly radiused cylinder windows, it will most likely fail eventually.

Look at the CA (middle) shell in Abelius' post. The lower corner is radiused, but there is still a sharp corner below it, which acts as a 'stress raiser/riser' (Google it).

Also, the radius in the corners is cast-in, which leaves a rough surface with imperfections, any of which can act as a stress-raiser.

Corners should be filed with a smooth 'rat-tail' or needle file of around 3mm diameter, getting rid of any pits, scratches, casting imperfections and internal corners.

 

 

Here's an un-radiused box, you can see, arrowed, a crack (or a casting fault, or both), which needs to be removed.

As it's running along the internal corner of the casting, you need to extend the radiusing along that area, using a good quality round-nosed rotary Burr in a Dremel (or similar).

 

 

Partly done, you'll notice there is still cracking/casting faults in both corners, you'd need to keep going until you get rid of it all (whilst removing as little material as possible), until you're left with a smooth surface, use a magnifying glass if neccessary.

 

[Abelius]

Yes, definately don't do it like in my picture. I got the shell in the state it is in a trade and haven't used it because it's screw holes are misaligned.

[UrPeaceKeeper]

Again just to echo the same sentiment.. the Version 2 mechbox is flawed in its design, it doesent matter how strong your mech is it will break eventually.

 

I would put this more akin to the materials used in combination with the design. If companies would start moving to a different material than cast zinc/aluminum/iron alloys maybe their gearbox would have more strength in that part. I'd just like to say I've not heard of the MT Haynes gearbox breaking which leads me to believe that at least there are some V2 gearboxes that dont break The ICS Split gearbox (which is a V2 basically split in half and reinforced, alot) is much less prone to failure than a standard V2, so much so it's failure point is usually not at the cylinder window but at the very front of the gearbox (caused by metal cylinder heads transfering lots of energy forward).