07 Kit Wheel Bearings Dilemma

So we got our kit, put 2 of the 8 bearings in each supplied wheel, and found that none of the 3 aluminum rods fit inside of the bearings… Did we do something wrong? What did everyone else do?

we were tinkering with our kitbot today and we found the same problem.

of course, i read no assembly instructions so i might have done something wrong. even so, the other bearings in the KOP didn’t even fit into the wheels.

You’re not the only ones. We found the bearings didn’t fit standard 1/2" steel rod. Anyone have the bearing and a dial caliper handy?

those aluminum rods are (most likely) meant to be used with the IGUS parts, and as such may not be exactly 1/2". While the info on the AndyMark.biz sitesuggests that the ID of those bearings is 1/2", in past years the wheel bearings have been either 3/8" or 5/16".

<edit> according to the KOP checklist, the bearings a 3/8" ID </edit>

when we came accross that problem today, we simply put on the wheels from 2006… :smiley:

I had the kit bot together today in about half an hour, i went to grab the wheels and get those on and ran into this kinda problem…My solution: I took a piece of precision grounded 1/2" steel shaft, measured it, and then measured the ID of the bearings, they were exactly the same size…It takes some effort to get em in the bearing holes, but they do eventually get in there.

Another problem that comes up is that the bearing are 1/2" ID and the holes that you would run the shafts through on the frame are 3/8", so obviously you have to fix this problem…A. If you are planning using the kit bot as your robot, I would turn down the ends and then assemble each side and put the bot together or B. What we’re doing since were using this as a test bot, just drill out the holes to 1/2" and collar the shaft and wheels in place.

Let me know if anyone else comes up with solutions to these problems.

like finding a piece of 1/2" od, 3/8" id metal tubing and some 3/8" bolts?

The bearings are 1/2" ID, not 3/8". So no, they aren’t going to fit any rod in the kit. As far as “standard” 1/2" rod… The rod is almost certainly going to have a +/- .001 tolerance. Maybe a -.005 tolerance. At any rate, the inner race of the bearing is going to also be something like -.0003 tolerance. So, mostly, your shaft is too big and the hole is too small. Ideally, you sand your shaft until the bearing slides on smoothly.

If you have that laying around go for it, we didnt, drilling those holes bigger took about 2 minutes total

I came across this yesterday and tried to wrap my head around the problem. I thought our KOP was missing something, but after going through the checklist again, it wasn’t. Someone wasn’t thinking when they decided to switch to the AndyMark wheels with 1/2" bearings while keeping the 3/8" kit chassis. :rolleyes: I just made a quick trip to Home Depot and picked up some 3/8" ID x 1/2" OD aluminum tube (and bolts, wires, and the sort). It slips over the 3/8" bolts and works well with the bearings.

Same here, we just bought 1/2 inch rod to support the bearing size

Hmmm…I didnt even look at them yet. This is obviously going to be a problem with our chassis, seeing as it will have a 1/2" oblong hole for chain tension.

I also wasn’t going to be using 1/2" shaft, I was just gonna throw a 1/2" bolt through the oblong holes and wheels so the wheels can be quickly adjusted for chain tension. I’ll be making sure 1/2" bolts fit through first thing tomorrow…

Also if you are using shaft, you could always turn it down a bit on a lathe to make it a better fit.

We’ll be using 1/2 shoulder screws as axles, which have a -.002 to -.004 dia tolerance on the shoulder, with a 3/8-16 thread on the end.

If you’re interested in finding out more about these parts, you can go to www.McMaster.com and type “shoulder screw” into the search.

Hope that helps.