Hey there! I’m working with an SDS mk4 swerve drive, and one of the turning motors (a NEO 1.1) has a slipping pinion gear. This is entirely my fault, due to pressing and taking off the pinion multiple times, but I’m now trying to find a solution. I attempted to use loctite, and it worked for about a week, until we did some full-power testing, which caused it to come loose. I’m now thinking about soldering it to the pinion as described in this video. Has anyone dealt with something like this, or have any tips? Thanks!
Which loctite did you use?
The “green” retaining compound (620 or 638) is possibly going to behave better. I would not attempt the soldering, I would get a new pinion instead. Trashing a motor shaft with a keyway (albeit not being used in this case) is not worth it.
Make sure you are press fitting with a press (or vice in a pinch (pun intended). No hammers.
You may need to let the loctite cure for a bit and be patient, from the SDS website (which you probably looked at) emphasis mine:
If the tolerances are not in your favor and the pinions slip on the shaft, or you feel that the press fit it too weak, an adhesive is required to transfer torque. The procedure is the same for all motors.
Apply a few rings of red Loctite 271 to the shaft, and the bore of the pinion, then slip the pinion onto the shaft down the the desired location.
Red Loctite 271 has been tested to a factor of safety of 4x the stall torque of a CIM when let to cure for 24 hours.
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It’s too bad that the Neo 1.1 shafts ended up undersized for press fits. If the loctite isn’t holding, we had success marring the shaft by dimpling it in a dozen or so places with a spring loaded center punch.
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Is there any reason you’re not just using the keyway on the shaft/pinion gear?
Press fitting pinions on an SDS module should be totally unnecessary.
This is also how slotted dowel pins work, so +1 to this solution if loctite fails.
The NEO 15t pinion is press fit only. No room for keyway with the tooth dedendum.
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Interesting. I’m used to the MK4i (which use all 20dp pinion gears), wasn’t aware there was that significant of a difference between them.
I used blue loctite (243) becuase that’s all my shop has.
I agree. red loctite would definitely work better, but I just don’t have access to that.
I’m working with NEOs, which have insane stall torque, but I guess I could lower the stall current in the code, to avoid any big torque.
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I think red loctite, getting everything clean (look up the various ways to clean blue loctite off) , and careful application followed by letting it cure for a day is you ticket for success here.
Sorry this is a fix that involves a purchase, but blue is simply not for this application.
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I don’t think that’s a good approach as it will affect your swerve drive performance. See if you can procure some loctite 609 as recommended in the SDS Mk4 assembly instructions, or use the shaft-marring technique I mentioned above.
[edit] This is my recommendation because I’ve never tried to solder a gear to a shaft. It might work, I just don’t have any OpEx to offer you on that approach.
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Yes 609 is the proper things to use. We have used it in the past to retain NEO pinions and have never had a failure.
Loctite 243 is a thread locker, not a retaining compound. The red stuff (262, 271, etc) are also thread lockers. You want one of their products intended to take up small gaps in press-fitted parts, like the 609 mentioned.
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I’m going to pile on a little and disagree with the marked solution.
Using one of the “red” Loctites (threadlocker) in general might be adequate strength. BUT if you are getting slipping, use the correct product, which is a retaining compound (not a threadlocker).
Usually “green” Loctite 609 is the best, but there are others w/ higher strength too (620, 680). Also, I highly recommend using the matching primer for best results. I think 7471 or 7649 is the right one here (also helps w/ red Loctite).
I don’t recall ever having slippage after using any of the Green Loctites. But keep it away from bearings and bushings!
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I do have some ancedotal experience doing similar things.
The short answer is, while it might work for tiny things like in the video above, soldering doesn’t scale.
In a soldering process, both the solder and the two parts being joined have to be heated high enough for the solder to wick onto them. Otherwise, at best, you get a ball of solder loosely sitting between the parts with little to no adhesion.
With tiny parts, you have the ability to heat them up
- With normal sized soldering irons
- Fast enough that other bad things don’t start happening.
Most motors don’t survive being entirely heated up anywhere near soldering temp. Same goes for most electronic components.
The key with soldering is to minimize the time in contact, which minimizes the energy transfer. You need localized heat to melt the solder, but not so much energy that when it distributes through the part, sensitive things have been raised to a “beyond-repair” temperature.
I’d be concerned that without a large enough soldering iron, by the time you got the NEO shaft and the gear hot enough for solder… there would be other issues. Wires melting, bearing parts deforming, etc. And even if you had a big enough soldering iron, it would heat things up so fast that it would be hard to control, and you might break things anyway.
So… totally possible that someone could do an experiment to prove my concerns wrong. But as a casual soldering enjoyer… the plan doesn’t pass my sniff test at scale.
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