Unable to cycle with 8.4v Battery

[Styrak]

There could be a few issues, all or some of these:
- You spring is too strong
- Your shim job is bad
- Your battery is not powerful enough (you said a 9.6v stick works, but really an 8.4v should work as just as well with an M110)

[Off_kilter]

http://www.hobbyking.com/hobbyking/s...SOFT_Pack.html

These will fit in your ak btw

[Stealth]

I actually recommend this one:
http://www.hobbyking.com/hobbyking/s...SOFT_Pack.html

Fits under my front sight cubby hole...

[Anthology]

Originally Posted by Styrak

There could be a few issues, all or some of these:
- You spring is too strong
- Your shim job is bad
- Your battery is not powerful enough (you said a 9.6v stick works, but really an 8.4v should work as just as well with an M110)

If anything, the shim job is too loose, not enough to bind gears though; it's a work in progress but I've thoroughly tested this.

Judging from feedback today, I believe it's the batteries. 9.6v worked fine all day. The Ni-CAD 8.4v worked but did get hung up once on semi (it hung in the middle of pulling the spring, to had to switch to full auto)... this was on the DOWNGRADED spring as well (shooting ~320 on .2's).

I am investing in some lipos that people in this thread have listed.

[Styrak]

Originally Posted by Anthology

If anything, the shim job is too loose, not enough to bind gears though; it's a work in progress but I've thoroughly tested this.

How have you tested the shim job? Have you taken everything out except for the gears, screwed the mechbox back together, and tried to spin the gears? They should be fairly smooth and make at least 1 or 2 rotations.

[Anthology]

Originally Posted by Styrak

How have you tested the shim job? Have you taken everything out except for the gears, screwed the mechbox back together, and tried to spin the gears? They should be fairly smooth and make at least 1 or 2 rotations.

That's precisely what I did... I got around 1 1/4 turn on my rough job. I need to shim my bevel gear a little better, without it I was getting around or over 2 with no lubricant. I believe this is well within the boundaries of a functional shim job. I tested with the motor and no spring or piston and things seemed to work well albeit with the bevel gear being a tad noisy.

The gears show slight wear given they are rather old and exposed to sand but they still mesh well.

[Jimski]

Originally Posted by Anthology

As for your second suggestion, why do the 8.4's work when a lighter spring is installed? Is it simply a matter less resistance from the spring translates into less resistance on the possible binding sector gear?

it's a matter of battery cell size.
Smaller cell= smaller discharge rate = less torque

the battery could be 12v, if the cells are small it will not pull the spring.
Batteries with a bigger capacity have bigger cells; that means the battery will last longer on the same spring, or that the battery will pull stronger springs for the same overall duration.

[Anthology]

Originally Posted by Jimski

it's a matter of battery cell size.
Smaller cell= smaller discharge rate = less torque

the battery could be 12v, if the cells are small it will not pull the spring.
Batteries with a bigger capacity have bigger cells; that means the battery will last longer on the same spring, or that the battery will pull stronger springs for the same overall duration.

Makes sense. It's probably why the 1100 mah NiMH could pull much more consistently.

[Styrak]

Larger cells means PHYSICALLY larger, like sub-C cells instead of mini 2/3A cells. The capacity doesn't make a ton of difference.

[Jimski]

important precision from Styrak.

[Anthology]

Originally Posted by Styrak

Larger cells means PHYSICALLY larger, like sub-C cells instead of mini 2/3A cells. The capacity doesn't make a ton of difference.

Really? Stealth was telling me at yesterday's game that capacity does factor in enough to consider it part of the issue... maybe I misunderstood/misheard him though.

Regardless, I purchased the 7.4 LiPo's he recommended. I'll finish my shimming, R-Hop, and throw my M110 back in there within the coming weeks.

[Styrak]

It makes a difference yes, but changing cell type/size makes a HUGE difference because of how much more amperage large cells can push.

[Anthology]

Originally Posted by Styrak

It makes a difference yes, but changing cell type/size makes a HUGE difference because of how much more amperage large cells can push.

Ahh, that's where these videos of large pack batteries with 4000+ mAh "outperforming" LiPo's come from then?

[Styrak]

Originally Posted by Anthology

Ahh, that's where these videos of large pack batteries with 4000+ mAh "outperforming" LiPo's come from then?

Anything with 4000mAh will be a sub-C large battery. Mini 2/3A batteries only go up to 1600mAh max.

[MaciekA]

Originally Posted by Anthology

Ahh, that's where these videos of large pack batteries with 4000+ mAh "outperforming" LiPo's come from then?

Until someone who has a significant amount of experience with binding/friction/shimming/electrical/etc issues can take a look at your gearbox and give you a second opinion outside of your own, we're all sorta grasping at straws, however, I think the thread consensus is one of two: You've either got shimming/binding issues, or (more likely), your battery is no good.

You and I have talked about a range of gun tech topics and my gut feeling is that you've got a very good intuition of how to assess whether your gearbox is generally low-fiction and sounding healthy, so I'm personally gonna side on the "weak-ass pull" theory here.

If you were one of my teammates and handed your gun to me for a weekend I'd do the following:

1) Ensure that it has a high torque motor in it (with strong (neo) magnets -- i.e your motor can stick to the fridge and is reasonably tough to take off the fridge). All other things equal, a neo motor paired with a somewhat weak battery will pull stronger than a non-neo motor.

2) Give it more bandwidth and lower latency: Use either Deans or XT60 connectors, wire it with 18AWG or 16AWG wiring, and use a MOSFET.

3) Give it more juice: A LiPo battery with a high C value (25C and up). Stick to 7.4V, you can pull almost all game-appropriate loads with 7.4V.

4) Compensate for the (typically) lower rotational speed of the torque motor with slightly faster-ratio gears (16:1 or 13:1). 16:1 ratio is the safer choice for feeding.

These 4 pillars always lead to the same overall effect: Superb trigger response, longer-lasting periods of trigger-snappiness, far better (and often far more cost-effective) choices for batteries, and better tools relating to electrical power (LiPo voltage meters, better battery balancers, on-MOSFET computers that can monitor your battery health, etc...).

EDIT: this is just what I'd do. The other docs here might have other equally fine ideas