RcTek : Information & Resources for the Model Car Racer

Two Speed Adapter Wear & Alignment

This article is part of a section of the RcTek site that is devoted to informing the model car owner about the various different aspects of Transmissions.

This article covers two topics regarding the adapter used in the two speed transmissions of some model cars, both wear and alignment.

Two Speed Transmission Adapter Wear

After some considerable use, due to the amount of gear changes and the forces involved, the two speed adapter can develop indentations on the flat faces.
These indentations are made by the ball bearing that runs on its surface and can result in sticking gear changes or no gear changes at all.

Two Speed Transmissions

Two Speed Transmissions

The image on the left shows how the adapter should look, but the one on the right clearly shows the kind of problems that can occur.

Replacing the adapter is a relatively low cost cure for the problem, but regrinding the faces is possible should there be no alternative. If this option is taken, make sure the faces are ground both flat and true. Also, depending on the manufacturing process used, there may only be a thin ‘skin’ of hardness on the adapter and grinding will remove this.

A Better Adapter?

Although the adapter used on the Serpent cars is like the one above and the problem it suffers takes a long time to develop, there is an alternative design that does not suffer from this problem.

Two Speed Transmissions

Two Speed Transmissions

The image on the left shows how the ball contacts the flat on the adapter with the most common type used throughout this series of articles. The image on the right shows an alternative that was in widespread use at one time. The contact area between the ball and the adapter is greater and so the wear problems will not occur as easily.

There is a possibility with this design that the increased friction could lead to problems.

Adapter Alignment

I have seen a few cars where the adapter could be fitted easily but would be very difficult to remove.

This problem was caused by the slot in the adapter that is used to drive the transmission shaft being very slightly off centre. Thankfully the hole in the transmission shaft was also slightly off centre and if the adapter was turned through 180 degrees the removal problem disappeared.

Related Information

One Way Bearings

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© 2001, 2009 by Darren Burnhill