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  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 two speed transmissions.

This article covers two topics regarding the adapter used in this type of model car transmission, wear and alignment.
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Section Contents
  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 Two Speed Transmissions 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.
Two Speed Transmissions
Two Speed Transmissions Two Speed Transmissions Two Speed Transmissions
Two Speed Transmissions
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 Two Speed Transmissions 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.
Two Speed Transmissions
Two Speed Transmissions Two Speed Transmissions Two Speed Transmissions
Two Speed Transmissions
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.
Summary
You will now hopefully be better informed as to what kind of wear problems occur with the two speed transmission systems used on remote controlled model cars, the effects of such wear and a possible cure for alignment problems.
Related Information
One Way Bearings
Further Information
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