Another left motor gear failure, need a solution

That is good to know. Since the figure is not a torque, I assume that rating
is with the 10 tooth #25 sprocket? Any other qualifications to the rating?

no, the rating is 30 kg/cm of torque, but it so happens that the 10 tooth #25
socket is just over 1 cm, so the 30 kg (66 pounds) per cm translates into almost
66 pounds of force (close enough that we just use that value)

Just to be clear, does that mean 66 pounds hanging on the chain will just stall the motor at 12v and no current limiting?
Or does it mean 66 pounds is the max that a motor will lift given Maslow driver/power supply?

Just trying to understand why it is different from the 50kg cm on the spec page.

If it’s really 50Kg/cm that it’s rated for, that would be 110 pounds/motor.

what spec page are you looking at?

but since we know we have trouble across the top of the machine, I have trouble
believing that it can actually apply that much force.

David Lang

The one copied into this thread. Another left motor gear failure, need a solution
same as
http://www.etonm.com/products_detail/productId=89.html

Its hard to be sure which line refers to our motors, but mine are marked ET-WGM58A-E
E is the 5th letter, so I looked at the 5th line down. Same line that @Gero highlighted.

I looked at the speed specs at git and highlighted the closest to the speed referenced on git. There could be a typo in the speed r/min 17.6 Etonm and 18.6 on git.

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it’s been noted before that our motors don’t quite match those specs. The gear
ratio is incorrect and those motors don’t have encoders. The motors we are using
were a custom order, and Bar has listed the specs as 30 Kg/cm.

that page also lists max current (at rated load) as < 1.5A, but we’ve seen
people burn out the 2A rated chips.

We don’t know what the actual motor performance is. It may be worth trying to
test some of the motors.

David Lang

That test sounds like a good idea, but the weakest link needs to survive in tact for it to be valid. That means lowest common denominator hardware. If the test bends thin motor mounts, its a fail.

As the problems have been left motor, It would be interesting to see if it helps to mount the motor in the same orientation as the right.
____O ____O
instead of
O ____O

Also, for completeness, since the sprocket radius is slightly larger than 1 cm, the rated load capacity is actually 2 lbs less than estimated for 30kg cm at 64lb. If @ManOfScience is correct in his 60lb estimate, that difference matters because we are right near the edge.

The table I copied was from alibaba and it’s mentioned ‘contact supplier’ and ‘custom build’ so the table could be seen as a rough reference. The gear ratio seemed to be an estimate as mentioned in this post Whats inside the gearbox/motor? so the max torque could be one too. I know it’s not an accurate approach, but the best I can do to get an estimate on the stall torque.
I will do it with both shields tonight.

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I had a conversation via skype and Etomn did confirm the Maslow motors are custom at 30kg and are not listed on their web site. Not sure why this motor was made custom when the 50kg version on their web site seems like it would work fine. see attached photo.

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one reason I don’t think it’s the ‘pull tight’ that’s ruining the gears is that the damage to the gear is spread across too many teeth

This example shows the wear pretty uniformly around the entire gear. Other pictures have shown 1/4 to 1/3 of the teeth damaged.

If this was happening at pull tight, the damage would be far more localized, as you only have a few teeth that mesh with the next gear

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I agree. I think that when we’re seeing all the teeth gone in one spot it’s because once it starts slipping one spot gets really worn down. I think that this gear simply needs to be made stronger from the factory to improve the life of the motor. It’s a weak spot right now.

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Is this gear the one that replacements are available for?

Yes it is

Edit: Do you want some for testing? I’m happy to send them to you

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Hannah mailed some just this week! Thanks for the offer, your support is very, very good :100:

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can you send a few to either me or @bee for testing?

David Lang

Don’t know how many @Bar has, but @Metalmaslow, if you post these for sale In the Market, I would guess that 200 is WAY too few to order
Personally - if I had a place to order some, and they were as cheap as you said, I would want 10 of them to have for repairs into the future. It only takes 20 jerks like me and you’re out of stock.

If anyone is getting ETONM to send more, I think they should ask for 1000 , or more (cash-flow permitting).

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Please tell me if this works … I have resin and silicone available and will make a huge batch haha

Also … Im really sorry for my delay … dog is finally out of the scary part and were on the mend. I’ll be back to work at some point this week and will post those 3d files… finally

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ummmm … do you think I could get a couple of the gears? My maslows been sitting here dead for almost 2 weeks because of the gear

I am far from an expert and have only been briefly following this, but if the motor plastic gears are wearing (to one degree or another), wont this effect our sled’s “actual” vs computer calculated positions (causing inaccurate/inconsistent cuts)?

It seams to me that if the gears are wearing (deforming), that the sled’s position “tracking” method is being compromised (almost akin to the chains having been stretched).

Are “metal” or other stronger plastic replacement gears available?

it’s not the plastic gear that is wearing out, typically it is a metal one. Gears tend to work pretty good until a complete failure. takes 1 minute to unscrew the 4 screws and check inside if you are really concerned

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If that be the case, maybe the gears needs to be made from a better strength steel (hardened?).

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Or maybe we need more stiff drive axles…

To me, the wear marks from @Red_Peter’s photo seem to indicate disengagement of the gears,
That could happen if the gear shaft were flexing from too much weight being far out from the support bushing/bearing causing the axle to flex the gears apart:


I don’t know how we would check for this though.

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