broken gearbox

can anyone explain under what circumstances how this would occur?

_____________

I just took it outside to test with a new 9.6v battery. BBs would fall after 10ft. I was using a Systema M120 spring which was doing 384 fps a month earlier

-The mechbox shell is TM

took it apart and saw this







The piston head was also totalled

My only guess was the spring was too much for the gear box. Just a faulty shell possibly?

The pistonhead came loose in the gearbox and started getting all tore up, but the gearbox cracking is just something that sometimes happens, it shouldnt be tied with the piston head coming off but for whatever reason it seems like that is what happened.

piston head was still on the piston tigltly, it was just smashed

possibly due to cold weather?

Probably just age and use.

btw i wouldbt use systema springs they are realy long compared to other springs and tend to put constant stress on the gb.

he probably just learned his lesson

sniper2525 wrote:btw i wouldbt use systema springs they are realy long compared to other springs and tend to put constant stress on the gb.

+1

Any gearbox is susceptible to cracking due to repeated impact on low quality cast/pot metal castings. Some are better than others based on alloy composition and many are "reinforced" to prevent/reduce that risk. CNC gearboxes are MUCH better but to say they are cost prohibitive for the average airsoft gun is an understatement!

so dont get a TM mechbox shell?

that m120 spring was a little worn out when i put it in. I could tell because it was really easy to push in and close

For replacement boxes I have had good results with SRC gen III and G&P 8mm shells . . . YMMV

get a modify 8mm it is one of very few that actually address this issue. 99.99% of reinforced gear boxes do not address this issue.

Sometimes to advoid this problem checking the cylinder head helps alot of time. The cylinder head gets slammed forward and causes play in the holes that are located on each side of it over time.The mechbox has two nubs one on each side of the mechbox if there is to much play or slack in the holes that the nub sits in the cylinder head will shift causing the mechbox to break.Also changing the spacing on the piston head and body can also cause it by the piston head going to far forward in the cylinder and slamming into the back of the cylinder head and pushing forward on the nubs in the mechbox causing the front of the mechbox to break. Hope this helps out and remember to check the holes in the cylinder head for play especially if you are going for rof or using high fps springs.

Rhino wrote:get a modify 8mm it is one of very few that actually address this issue. 99.99% of reinforced gear boxes do not address this issue.

+1

I soon will be getting a modify also, and i know trent has one also, they are extremely reinforced.