I fabricated this crude little device to keep the idler tensioned. (I'm very sorry but i forgot to keep a record of all the sizes of the fasteners if anyone decides to make a similar contraption....
but the screw used is about 4 inches long...) Henntec it ain't, you can only adjust track tension by removing or adding tracks. (If you do remove one track, at least on this tank - which i did as a first step when it started throwing the track - the tracks will be very tight, but will still work.)
This tensioner provides spring tension to allow the tracks to remain straight, keeps the track in place on the idler, and helps prevent a thrown track. After testing it seems to work well, so far. You can see how loose the tracks are - but they still stay on anyway even in tight turns.
It does need a little more refining. To describe the whole works, all it is made of, is a long screw that goes inside the metal wheel. (In my parts collection I found ONE bearing that fit exactly right inside the wheel- but only one- so I used it. And for sure a bearing in the wheel works much better, if you have one. But a sleeve would work too.) Then two washers between the wheel and the hull.
The washer inside, touching the hull, is the biggest that would fit, with a smaller washer over that for the spring to bear against. Then comes the spring, a strong one it was, had to cut it twice to get it right. Then more washers to bear against the nuts. I have two nuts on it, the big coupler nut, and one jam nut. The jam nut, of course, keeps the adjustment from changing. You could also just use two regular size nuts.
It works well with the metal tracks and the tension is adjustable. By changing the spring, or cutting the spring you can make it as stiff as you'd like.
If the spring is strong enough, the works should not turn with the idler wheel. But, to prevent the whole works from turning need to remove that large coupler and use a third nut, then fabricate a piece of metal that bears against the hull and keeps the screw from turning, drill a hole in it, then clamp in place with the third nut. Could also just fabricate a piece of metal, to replace the first inboard hull washer, that does the same thing.
