Combat Machine Motor

[ghillie24]

I have a G&G combat machine with stock internals. It is perfectly shimmed and adjusted, but I am still disappointed by the motor's performance. I put a Hummer 1300 motor in it, but it would cycle 1 and 1/2 times. I just want a suggestion for an overall better motor.

[ctres]

That is what happens when you have a good motor with plenty of power/speed and a weak spring. The momentum of the motor makes it keep spinning after the electricity is cut off and it has enough momentum to partially pull back the piston. This is known as overspin. The weaker the spring is and the faster the motor the more it will pull the piston back. A stronger spring will prevent overspin and you can short stroke the piston and gears to keep the fps down, or you can get an active breaking mosfet to stop the motor.

Overspin isn't really that big of an issue though except that there is a slight possibly that it could cause some wear on the piston teeth and that the spring is left partially compressed which will make it lose a bit of power over time. Almost all upgrade motors will have this issue especially when used with a Lipo. If you are happy with the performance of the motor then keep it and either don't stress about the overspin or just do one of the fixes I mentioned above.

[Squirrel]

Like CTRES said, a stronger spring will fix it. An m110 and some TRUE m100 springs will solve your problem. With all the spring companies now it is hard to tell what is what.

[Maverick]

What they said...or put in an even stiffer spring and short stroke the system to achieve your desired FPS.

To answer the motor question though, SHS High Torque, Lonex High Torque, or any ACM neo magnet High Torque motors are the go to nowadays.

[ctres]

For reference I've had overspin with even with slow motors like a JG blue when I've used an 11.1. Knowing more about your setup, particularly your battery and ROF will be helpful, but an m100 will rarely solve your problem in my experience. I would say either an m120, or an sp110 (sp's such as guarder are usually a little hotter IIRC) or something rated around 400 fps will probably do the trick.

The motors Maverick mentioned are great choices, and I'd add the JG blue to that list personally, but if you are happy with your performance other than the overspin then I don't see any reason to spend more money changing motors, since the motor itself really is not to blame.

FYI my current build has overspin with an m100. I use precocking on semi so I don't mind, and then I program my fet to active braking to make sure it is decocked for storage. Otherwise I prefer stopping overspin mechanically via stronger spring since running active breaking causes motor heat and brush wear.

[ghillie24]

If I want to keep my FPS, how many teeth should I remove from the gears, and will an m110 be strong enough?

[ctres]

It's hard to say if an m110 will do the trick. As I mentioned before, tell us what batteries and rof you are getting and we can give you a better idea.

Usually shortstroking takes about 20fps per tooth (give or take) but it will depend on your spring strength somewhat. With an m110 you shouldn't have to SS more than 2 teeth. With an m120 you may have to do three. Your fps with a given spring is always going to depend on your airseal, so once again it's hard to give you a definite answer. The more we know about the build, the more we can help.

[ghillie24]

Dec 25, 2013 10:16:54 GMT -5 ctres said:

It's hard to say if an m110 will do the trick. As I mentioned before, tell us what batteries and rof you are getting and we can give you a better idea.

Usually shortstroking takes about 20fps per tooth (give or take) but it will depend on your spring strength somewhat. With an m110 you shouldn't have to SS more than 2 teeth. With an m120 you may have to do three. Your fps with a given spring is always going to depend on your airseal, so once again it's hard to give you a definite answer. The more we know about the build, the more we can help.

Okay, In room temperature, with a 363 mm 6.03 brass inner barrel it shoots anywhere from 315 to 330 fps. It has all stock internals except for a bearing spring guide. It also barely any silicone oil in it. I am working on getting some soon. I want to use it as a field and CQB weapon, so I was thinking of getting it to 330 consistently with a max of 340. I realize that in order to get it to shoot consistently 330 fps, I need to get silicone oil. 

[ghillie24]

Also, I am using a 9.6v Nihm battery, and with it I am getting about 16 rounds a second.

[ctres]

Okay, so if you intend to keep using that battery and motor then maybe an m110 will work for you, but if you ever decide to change motors or move to lipos then you may have issues again. There are a few things that are important to remember when upgrading the spring though.

1. The more stress on the gearbox the more poor shimming will become apparent so a good job is important. I recommend the bevel to pinion method.
2. Shortstroking reqires either moving the metal tooth on a stock piston back, or getting a piston with a partial or full metal rack. This is because if the last tooth is plastic it will wear down very quickly. I recommend the lonex red or blue piston. If multiple teeth on the piston are metal then you don't necessarily need to modify it, only the sector is required in that case.
3. ALWAYS remove teeth from the pickup side of the sector. This is done so that you don't have any issues with the piston releasing before the tappet plate returns.
4. A stronger spring will magnify other issues so it important to get them ironed out. Use sorbo on the cylinder head to correct piston angle of engagement and protect the gearbox shell. This will require you to remove the second piston tooth and part of the third. If you are concerned about the gearbox cracking you can also radius the front cylinder windows.
5. Though it doesn't have anything to do with the short stroking a 15 fps variation is kind of a lot IMO and I'd say try to fix the air leak. Teflon tape the cylinder head if it needs it and replace the piston o ring with a #14 or 116 from McMaster. I have the exact part number if you need it. Also silicone oil can be used on o rings but grease is needed for the gears and other non airseal parts. I'd recommend super lube.

If you have any specific questions on anything let me know and I'll point you in the right direction. I can't cover everything in one post but if you want to get into teching more I'd recommend you check out the airsoftmechanics forum.