Fabricating the tongue that will hold your guide of choice should follow several basic principles, one of which is that travel or rotation should be limited either by the just the shape of the leading edges of your tongue or by adding stops. If you allow excessive rotation then you risk allowing your model to rotate well beyond the useful range of performance and either wedging it at a 90 degree angle which becomes a hazard to others or worse yet allowing it to travel in the reverse direction. Be sure to limit the rotation of your guide to just 45 degrees each way by shaping your tongue into a triangle or soldering stops in place depending on the style of guide. If your car is sliding more than 25 degrees from the direction of travel then it is already out of control and if it rotates well beyond that then a properly set up guide stop will at least force the guide (and your model) out of the slot, removing power and allowing it to slide to the gutter and usually out of harms way. In a recent race one car which allowed the guide to over rotate by at least 180 degrees repeatedly wedged itself sideways, blocking the track and creating a hazard for others at numerous locations around the track. Limiting the rotation of your guide will not only increase the life of your model but also the lives of the models of those who race with you.
The Happy Canadian Scale Modeler!
