We just received our CIM-sim from AndyMark and our RS-550s from Banebots.
The CIM-sim comes with two am-0928 pinions, plus we ordered a spare.
The problem we are having is the id of the pinions is .125" and the od of the RS-550 motor shaft is .125" as well. In fact, we can slide the pinions on and off the shaft by hand with very little force, if any.
This is by no means a shot at AndyMark, it just seems odd to me that the pinions sold with a transmission specifically sold for use with a 550 series motor won’t work with it. I placed a call to them this morning, a Saturday, and it has yet to be returned.
So, I’m asking here, how would you go about mounting these pinions to the motor shaft?
Drill and tap for a set screw? (Not my first choice.)
Loctite? (Red maybe.)
???
Possibly AndyMark is between a rock and a hard place with the bore size on that pinion, because the BaneBot RS-550 shaft seems to be ever so slightly smaller than the AndyMark 9015. One of our pinions was pretty hard to press on to the AndyMark 9015 motor, so a smaller pinion bore might not be desirable, either.
It’s great to know that there is a retaining compound that might work if we end up needing the faster flywheel speed from RS-550. Thanks for pointing that out.
All of the RS-500 series motors (Fisher-Price Motors, am-0912 motors) all have shafts of the correct size to fit this pinion. They have a 1/8" diameter motor shaft with a knurl that lets the 1/8" id bore of the pinion gear press on to the shaft nicely.
The BaneBots motors don’t have this nice feature. The above suggestions may work nicely, but if they don’t, adding a set screw will do the trick.
Thanks Andy!
Correct, the knurled shaft would have been nice, but hey, where’s the challenge and learning in that?
We’ll most likely do a combo of Loctite and set screw. There’s nothing wrong with a little insurance.
We squished the banebot motor shaft in a vise with the diamond pattern jaws to make a knurl like pattern, you have to be really careful you don’t smash it too much though, it doesn’t take much to deform the shaft. The proper lock-tite also is a good solution, as others have stated.
The banebot rs-550 shafts are smooth, and the FP shafts are slightly raised by a slight knurling done to the shaft(which is a nice feature to lock the gear on the shaft)
When we needed to use a fp motor in the past, with a BB gearbox, we used the BB gear and lightly filed the knurling on the FP motor.
To use the Rs-550 with a AM gearbox, you would need to ‘enlarge’ the shaft, or use some other method to attach the gear(locktite or setscrew?)
With the large selection of available motors, I’d try to match the motors to the gearboxes for reliability.
That also equals heat treatment, and probably not the good kind.
If the pinion is steel, if you get it red hot and then cool it slowly, you risk either annealing or normalizing it (from the heat), and inducing a soft microstructure (from the slow cooling). Cooling it faster will tend to harden (and thus strengthen) it, but the proper rate to achieve particular properties depends on the alloy composition. (Check the ASM Handbooks.) It’s most definitely possible to harden it too much if you quench it rapidly. You’ll also form an undesirable oxide layer on the surface, unless you’ve made preparations to carburize or nitride the steel instead. (Hardened steel gears are often finished by grinding to remove the oxide; carburizing and nitriding are not worth the trouble here.)
If the pinion is brass or bronze, you’ll probably soften it by getting it red hot. For those materials, you can’t restore the hardness and strength as above.
You might get better results by putting it in a household oven at its maximum temperature, which probably won’t be high enough to ruin a steel pinion, but which will induce some thermal expansion.
If it were me, though, I think I’d just find an undersized and a nominal reamer, then get an arbour press and install it more carefully that way.
While supporting the far end of the shaft, press the pinion on with an arbor press. This is the preferred method. Even with a 1/2 ton press the pinion will slide on easily enough. No need for heat, reamers, sandpaper, etc. Honest!
I think some people haven’t really read the original post well. The problem is not having difficulty pressing the pinion on, it’s that the pinion id is the same size as the od of the motor shaft. There is no interference fit. I can easily slide the pinons on and off with my fingers.
Today I acquired a bottle of Loctite 609. I carefully cross drilled and tapped the pinions. I then ground a flat on the motor shaft. Finally I applied the 609 to the shaft and pinions and assembled the two together. We’ll load test in a few days when the shooter is finished. I am confident we will be pleased with the results.