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MaciekA · January 3rd, 2013, 23:21

So we know that you either have an AoE problem or a PE problem. It doesn't matter which problem it is because you want to build your system to prevent both.

Either way, you want several things to be true when the sector gear pickup tooth comes back around for another whack at the bat:

The sector pickup tooth must meet your piston pickup tooth at a nice angle. You may think the angle is good but it can be deceiving depending on the shape of the tooth (rounding) and where the piston sits when the sorbothane or neoprene (or whatever padding) on your cylinder head "settles" under the pressure of the piston head and the spring.
Your piston pickup tooth must be strong enough to handle the stress at a high RoF. It is much greater than when at a low RoF, especially with a torque motor and especially with a LiPo.
Your piston must be returning home faster than your sector gear comes around again. Have you checked that your piston moves freely and is not experiencing any binding? Take the spring and spring guide and gears out and seal the system up and see if your piston can freely fall up and down the entire range of motion without any help from your hand. If not, you have a slow piston with some friction or binding.

For reference, my MP5K runs an M130 spring, a type 2-ish cylinder, 3/16" sorbothane pad, 13:1 gears, neo motor, SHS lightened 15 tooth piston, stock ~90mm barrel. High RoF and 380fps. No PE, no problems with the pickup.

My advice:

Try an M120 spring.
Review AoE and PE.
Check that your piston is as free of friction as possible. Make sure to seal your gearbox completely with screws when testing. Keep the cylinder in there too. Then do the same test WITH your gears in there just to make sure you're not getting piston/gear binding. Test everything you can logically think of possibly going wrong before destroying any more pistons, you'll be surprised what you can find.
Consider a piston with some balls - shs 15 tooth (nylon, all metal teeth rack), lonex red (glass-reinforced nylon, mostly metal teeth), etc. Don't install a fancy piston until you have worked out any other latent kinks in your system. After installing a fancy piston, re-test for binding and friction (without gear, then with gears) again to make sure you're not about to kill another piston.
If you are using Deans/XT60 and a MOSFET and LiPos, consider doing your tests with a small and weak LiPo rather than a strong one. I use a little 650mAh LiPo for initial gearbox tests so that I don't completely destroy a piston if there's any surprise binding or friction -- that way I simply get some lockup or heat and can keep reviewing until perfect.

BTW, the way I post my dropbox pics is to go to the dropbox UI and "copy public URL"

January 3rd, 2013, 23:21	#24
MaciekA Trader rating Join Date: Jun 2011 Location: Portland, Oregon, USA	So we know that you either have an AoE problem or a PE problem. It doesn't matter which problem it is because you want to build your system to prevent both. Either way, you want several things to be true when the sector gear pickup tooth comes back around for another whack at the bat: The sector pickup tooth must meet your piston pickup tooth at a nice angle. You may think the angle is good but it can be deceiving depending on the shape of the tooth (rounding) and where the piston sits when the sorbothane or neoprene (or whatever padding) on your cylinder head "settles" under the pressure of the piston head and the spring. Your piston pickup tooth must be strong enough to handle the stress at a high RoF. It is much greater than when at a low RoF, especially with a torque motor and especially with a LiPo. Your piston must be returning home faster than your sector gear comes around again. Have you checked that your piston moves freely and is not experiencing any binding? Take the spring and spring guide and gears out and seal the system up and see if your piston can freely fall up and down the entire range of motion without any help from your hand. If not, you have a slow piston with some friction or binding. For reference, my MP5K runs an M130 spring, a type 2-ish cylinder, 3/16" sorbothane pad, 13:1 gears, neo motor, SHS lightened 15 tooth piston, stock ~90mm barrel. High RoF and 380fps. No PE, no problems with the pickup. My advice: Try an M120 spring. Review AoE and PE. Check that your piston is as free of friction as possible. Make sure to seal your gearbox completely with screws when testing. Keep the cylinder in there too. Then do the same test WITH your gears in there just to make sure you're not getting piston/gear binding. Test everything you can logically think of possibly going wrong before destroying any more pistons, you'll be surprised what you can find. Consider a piston with some balls - shs 15 tooth (nylon, all metal teeth rack), lonex red (glass-reinforced nylon, mostly metal teeth), etc. Don't install a fancy piston until you have worked out any other latent kinks in your system. After installing a fancy piston, re-test for binding and friction (without gear, then with gears) again to make sure you're not about to kill another piston. If you are using Deans/XT60 and a MOSFET and LiPos, consider doing your tests with a small and weak LiPo rather than a strong one. I use a little 650mAh LiPo for initial gearbox tests so that I don't completely destroy a piston if there's any surprise binding or friction -- that way I simply get some lockup or heat and can keep reviewing until perfect. BTW, the way I post my dropbox pics is to go to the dropbox UI and "copy public URL" __________________ "Mah check" Now you know