We recently purchased AndyMarks EVO slim 3cim gearbox to use for the season and we got them in today and in trying to assemble we found the shaft with the ket does not fit into the pinion gear included in the kit, we were wondering if other teams have experienced this or if we missed something?
Note about CIMs:
The EVO Shifter utilizes a 15 Tooth 32DP gear as the CIM gear which requires a press fit. Due to the intended interference fit (0.001 - 0.002") along the 0.750" long gear, a minimum 3 ton arbor press is required to install this gear onto the motor in conjunction with a provided aluminum spacer (am-3552) to help set the distance of which the pinion should be installed from the end of the motor shaft (approximately 0.40"). If you do not have access to this size arbor press, we have the option to add CIM motors to your order with the pinion gears pre-installed, available as am-0255_15T.
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That you. The pinion fits on the shaft easily and freely spins on the shaft. Seems like the fit needs to be much tighter. Is it possible they have the wrong pinion in the kits? We have lots of cims both new and old and they all seem to have the same issue. Maybe we are missing something obvious?
That is odd, it seems to be a good question for AM support.
Yes, AndyMark got in a batch of bad pinions; I got some with some TB3s a week or two ago.
You can contact them and they’ll make it right, or you can use red loctite to attach them. Here’s the procedure from Kevin Kolodziej at AndyMark. I followed these procedures and it seems to be working fine. I did not run at stall torque, but I did put one CIM in brake mode and the other in full 13V and they both took that much torque.
We’ve been doing some testing here and have found a solution that you may be interested in. We tested using Red Loctite to secure the pinion to the shaft. I wiped off the output shaft of the CIM but didn’t really do any surface prep to the pinion other than it had been on an off a shaft several times, removing some of the oil. I placed a ring of loctite around the inside of the pinion near one end and slid that end onto the shaft first which helped distribute the loctite along the shaft and pinion. After using the spacer tool to set the location of the pinion, I added just a little bit more loctite to the top edge of the pinion and allowed some of that to wick down between the pinion and shaft. We did our tests after 16 hours of cure time (recommended is 24 hours) and found a very similar holding strength to that of a proper press fit, approximately 4x the stall torque of a CIM (7.8 ft-lbs).
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The appropriate Loctite product for this purpose is Loctite 680 Green retaining compound. It is made for this very thing and we have used it successfully for years.
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Hi, thanks for the recommendation. I am not the OP, but we have same concern with CIM Sport gearbox.
Did you use the same procedure as described above for loctite 680 also, or is it a different procedure? In particular, did you use any primer or extra preparatory steps for the shaft or the pinion?
Yes, green retaining compound is the proper thing to use. Red should not be relied upon for shear and shock loads on an axle.
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We found minicims dont like press-on gears so we reamed out the gears a little instead and used the 680.
1st year we used primer, last year we just cleaned with acetone. Both years no gears had any trouble.
The extra step of adding additional to wick in was not necessary.
Thank you! Thought we were missing something.
That was our thought here as well, that the green 680 should be better for this kind of application. However, in our testing, we found the red 272 Loctite survived all of our shock and impact tests whereas the green did not. We then did some failure testing and confirmed that red failed at a higher torque (7.8 ft-lbs) than the green did (6.4 ft-lbs). All of these tests were done on new off-the-shelf CIM motors. A comparison was also done with an older CIM with a known press-fit which tested to 9.8 ft-lbs, however, the pinion was in contact with the nose of the motor and may have have provided some additional resistance. For comparison, CIM stall torque is 1.78 ft-lbs.
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