[JMay]

This is on the bench currently, the umpteenth iteration of my tyre truer (details and files in the 3dp section), where as the original one was a simple hinged mechanism that could be lowered on to sandpaper, this one has the sanding medium moving and hence clearing the rubber detritus.

   

   

This iteration was to continuously move the sandpaper at 90 degrees to the tyre, which on other machines is done by reciprocating the sandpaper back and forth using cranks/cams etc. I wanted something different, and this design was a lightbulb moment from repairing my belt sander. By turning a belt sander upside down, and placing the axle carrier over, you get a moving sanding belt at 90 degrees to the tyres. I replicated this with a driven pulley system that runs the sanding belt around a plate over which is the original hinged mechanism. The sanding belts are 10mm wide rotary file belts available for pennies from the right sources and in various grit sizes to suit.

The unit has two motors a Mabuchi 365 to run the sanding belt pulleys at 16:1 via a gear train and a Boxer motor at 9:30 ratio to drive the axle holding the wheels and tyres to be sanded. This was for two reasons, firstly it keeps the motor drive simple and secondly I can vary the rpm of either motor by controlling the voltage supplied.

Still playing with the design as various ideas explored, i.e. a sanding belt tensioner, ball raced pulleys and gears, changeable axle (caters for different axle sizes) cut depth indicator/stop and dial gauge all in the process of being incorporated each time I get round to printing another set of parts.

The model shown has been used for sometime now with various upgrades, and will true pairs of tyres including soft grades, giving a smooth finish concentric to the axle without chunking the tyres.

Cheers
John.