So, I purchased one of these, and was assembling it. I seem to be running into a issue with mounting the Hex Hub to the shaft. When I use the provided hardware, it doesn’t seem to sit straight… it wobbles. I’m not sure what the best solution to fix it is. Did you have any similar problems? When I add a tire, it’s worse! 
Thanks,
Jesse
Can you go into a little more detail as to what is wrong? Do the parts look like the tutorial? I’m trying to help but I need more information.
In this tutorial…
lynxmotion.com/images/html/build122.htm
In step 7 it tells you to install the hub onto the motor shaft with the screw that holds the wheel onto the hub installed. You then push the hub on all the way, then tighten the set screw down. Then you remove the center screw and install the tire. Not sure what the problem is.
The issue seems to be the fit between the motor shaft and hub. When I tighten the set screw, it then seems to make the hub offset a bit, and make the tire wobble. It’s like the hub was drilled out just a little too much. I’ll keep playing with it. I’m not too concerned at this point, just wondering if other people had seen it. You are a great guy Jim, taking the time to answer questions! 
8)
Any time a hub is made to fit a shaft with a single set screw there is a potential for the hub to be offset a bit. But it should never be more than around 10 thousandths. That’s only like .25mm. I just checked the ones on the shelf and that’s where they are.
Funny… It’s not as easy as one might think. You can’t just say make me a hub that fits on a 6mm motor shaft. First off, the 6mm shaft can vary itself from 5.93mm to 6.03mm. As the parts are made the tool wears and things heat up, basically things change. If they make for 6mm you would have parts that do not fit onto the shaft. So they have a term called tolerance, so you say make the hole 6mm (+0.2mm -0.0mm). There will alway be some offset, it’s unavoidable. These are relatively low speed motor and wheel combinations, so the set screw method works ok.
Hope this helps. 
two words: cellophane tape.
Or if you work at a place like me: Kapton Tape 8)
You work at Kapton Tape?
Oh yeah, I had already thought of that… most of the wobble is gone, a little left but it’s workable. I’ll see how it handles once I start driving it, had just hooked up a single motor to battery. Thanks Guys!
I’ve shimmed shafts by wrapping regular printer paper around the shaft until a ~snug fit is achieved (keep trimming the thin strip of paper off until the desired fit is achieved). The regular paper makes a fairly hard mounting surface where as the tape maybe somewhat softer and gummy.
Or better, thin shim brass from a hobby store.
Alan KM6VV
kapton is probably a little thicker than cellophane and should compress less… of course I’m not sure this is a hardware store item.
anyway, if the gap is big enough use a beer can shim… and for the inevitable wise guys that is a shim made from strip of the aluminum cut from a beer can, or maybe a soda can I’m not sure if they are the same thickness.
I can use a lot of cellophane tape just for the cost in gas of driving to the hobby store.
Real machinists have the stuff on hand!
But the soda/beer can stock will work quite well.
Alan KM6VV
From a hobby shop???
No silly, I’m from the planet Kapton… 8)
I suspected, but now I know… Remember Mike, or whatever your name is, always use your powers for good!
