Re: Minibot Motor Press Fit
 

I would like to introduce you to a wonderful site of utilities for the shop:
http://www.myvirtualnetwork.com/mklotz/#shop

Many, many programs that calculate whatever you need to do in the shop. Your answer should be found with the FITS program.

Go up one level and you will find a bunch of math programs as well.

I have also noticed that the KOP CAD models from PTC have incorrect diameters on the motor shafts.

Re: Minibot Motor Press Fit
 

McMaster has set screw collars that are as small as 2mm bore...

Those are not exactly what i was talking about though. I was thinking about something like a 2 piece clamp on shaft collar. Lets hypothetically say you were trying to attach a wheel onto the shaft, you could make the wheel 2 pieces and put it together like a 2 piece shaft collar.

Set screw collar with 2mm bore: http://www.mcmaster.com/#shaft-collars/=ba2mtj PN: 57485K61
The OD on this one is 6.4mm that seems like plenty for you to ream it out to 2.5mm ID if you wanted to

2 piece shaft collars: http://www.mcmaster.com/#shaft-collars/=ba2k88

~DK

Re: Minibot Motor Press Fit
 

Are these legal minibot materials? Do they fall under "S. Mechanical fasteners"?

Re: Minibot Motor Press Fit
 

We found that in aluminum a sharp 3/32" bit at the right feed rate produces a hole that is a nice press fit on the tetrix motor.

Re: Minibot Motor Press Fit
 

I would argue that the are indeed mechanical fasteners. However you could always just make them out of aluminium. McMaster provides drawings for their parts and sometimes even CAD which makes replicating them, whether it is to use a different material or to save some money, quite easy.

If you made them out of aluminium you could be totally sure that they were legal and you could modify the design a bit to mesh easily with the system you already want to work with. The nice thing about the "clamp on" is that you don't have to be as precise with your machining, press fits can be tricky, but with a clamp on collar you can be off by quite a bit more and make up for it by tightening the bolt a bit more.

You could easily adapt the idea of a clamp on collar to make a clamp on wheel...

~DK

Re: Minibot Motor Press Fit
 

We found the same thing. It actually help if your lathe drill chuck is .002" off center. ;)

Since the shafts are long, we used the drill press as the press fit device (moving the bed into the chuck).

Re: Minibot Motor Press Fit
 

A simple way to modify the Tetrix gear box is to machine a bushing out of aluminum. Drill a hole the same size as the shaft thru the bushing and bore a hole slightly smaller than the O.D of the 25 tooth gear on the 25/10 gear on the bottom and a hole the slightly smaller on the top than the OD of the 10 tooth gear on the 26/10 gear and press the gears into the bushing. Press the gear into the bushing. This eliminates soldering and you should be able make as many as you want fairly quickly. Toss the 30/15 gear and happy miniboting.(is that a word?) By the way I found some very scary metal shavings in the gearboxes when I took them apart.

Re: Minibot Motor Press Fit
 

We have no plans to use the minibot gearbox. Helical gears are efficiency robbers, and sub 50% efficiency is not something we can afford.