[JMay]

On the question of deviation/slop in the tyre carrier leading to uneven tyre truing I went through several print iterations to improve the design. I stiffened the axle/tyre carrier rails (brown) by increasing the side walls and pivot blocks plus shortening the distance from pivot to tyre axle. I also increased the rear pivot shaft from 3mm to 6mm and moved the pivot blocks (dark blue) out more to increase the tripod effect. The pivot shaft is a force fit into the supports and carrier to eliminate slop. The tyre/axle carrier has a top plate (held down by 4 corner bolts in brass inserts) which pushes directly on to the bearings so that the axle is held rigid, to stop the axle twisting in the carrier. The adjusting bolt end is M6 bolt which goes into the tower to a captive nut and again the bolt is a tight fit. A 5mm diameter spring sits internally to control the up/down movement.

   

   

In practice, the compact size and using PLA Tough for the carrier & supports is sufficiently rigid over the entire structure to true a pair of tyres evenly as the force applied is limited by the risk of tearing/chunking the tyres.

Currently only truing 1/32 tyres but I need to make up some bearings with a 3mm shaft hole so I can true my BRM tyres, as there is sufficient width on the sanding support plate to accommodate these.

Cheers John