Stock gear ratio on G&G CM's?

[koppel]

As above, if anyone knows the stock gear ratio on G&G CM's off hand you'd save me a teardown. ?

 

Cheers

[Prisce]

Don’t quote me. But I’m pretty sure 13:1... wait for confirmation from someone who can confirm first!

 

@Sitting Duck @Iceni should be able to concour.

[Iceni]

I think it depends on model.

The early  models were certainly on 18:1, You were lucky to push <15rps on a 7.4 lipo with them. But they were sold with the intention of pulling an M130 on the USA market. On 11.1 you were looking at  <20rps when set for 350fps.

The newer models I have less idea about. I've actively avoided them.


What's your rounds per second and what batteries do you run?

Less than 15 rps on 7.4v it's 18:1 on an 18K motor.
Less than 20 rps on 11.1 it's 18:1 on a 18K motor.

The safe level of RPS I would use is 25rps. Any more than that requires a gearbox rebuild, with modifications made to stop the gearbox eating itself, Short stroking ect.

25rps on 7.4 and 18:1 is a 35K motor.
25rps on 11.1 and 18:1 is a 25K motor.

The other important question is why do you need to do the teardown in the first place? Is the gearbox non functional?

 

Because if the gearbox is functional I would almost certainly do the motor rather than the gears. A motor is easier to change, and doesn't require the time or the effort that is involved with a gearbox rebuild. And in pretty much all instances when you do open a gearbox up there is more cost than just the component you originally intended to replace. It's normally prudent to do a full service, Shims, Bushings, Airseal nozzle, Grease at the most basic level, but it adds a layer of cost. You may also run into issues like the COL getting jammed up on the sector cam, loosing parts, inability to get the box closed. It is never a simple job.

 

[koppel]

Cheers chaps, i know it has the grey can 18k motor in it and rof is not all that high, i'll run the rof on the chrono tomorrow & see. The missus doesn't appreciate gunfire at mignight?

[Iceni]

1 hour ago, koppel said:

grey can 18k motor in it and rof is not all that high

Sounds like 18:1 then.

Those 18K motors are pretty poor performers. A motor upgrade would probably be the way forwards for you. It's a 10 minute job, and only requires the bottom of the pistol grip removing.

Your batteries might also be suspect. If you are running the older NiMh type I would use this as an opportunity to upgrade.

If you are running lipo's make sure to take a note of them and post  it with the chrono results.

We will need to see:

Voltage
Capacity mAh
Discharge C rating. It's 2 values normally written like 30/60c or something similar.
 

[koppel]

Well i got round to measuring it and the ROF is 845rpm on a 3s 1300 mah Lipo with a 33amp continuous and 65 amp burst rating.

That's just over 14 a second so im guessing that confirms an 18:1

[Iceni]

Just over 14rps on a 3s battery? That's an 11.1v isn't it?

Those numbers seem off if it is 11.1v. Either your motor is totally shot or you meant it's a 2s battery (7.4v).

 

[koppel]

Yeah defo a 11.1v, also have 9.6v nimh and it does 13 on that!

[Iceni]

Make it harder to pick a motor for you then. Because either the gearbox is restive or the motor is absolutely pants. You may end up having to do more than just a motor change, It may need a service as well.

Same rules apply however, 11.1v your looking at about 25K rpm for 18:1 gears.

I would however wait for a second opinion. The motor been so weak has put me in the mind that there might be something I've missed.

So @Sitting Duck have a look at this one as well please.