Chain Tensioners

[sanddrag]

I need to tension chains and cannot use the method of sliding one sprocket. The sprockets are fixed. I need to add an additional adjustable roller or something. The tensioning roller itself cannot be a sprocket though due to space and time constraints. The tensioner can only be supported on one side. Automatic (spring loaded) would be nice but not absolutely necessary. The chain is running between two sprockets only. Due to space constraints, I need to push/pull it apart to tension. To room to push/pull together. All parts must be fabricated or purchased locally due to time constraints.

Tonight, I tried a spring loaded pivoting rocker arm type setup and while it worked for the chain moving in one direction, it failed miserably for the chain moving in the other direction. If I had this pivoting arm such that it was not spring loaded but rather adjusted then held in place by friction, would that work? I'd really like an "automatic" spring loaded tensioner if possible, but I'll settle for anything that does the job well enough.

I remember seeing something on this site that was like a plastic sprocket but just the outside ring and it was very flexible and you put it between two strands of chain and it pushes them apart. However, now, I can't find it. I know I said parts must be purchased locally, but if this is an easy and effective solution, we might order them if we know where to get them.

So, basically, I'm desperate for ideas. Pictures are worth 1000 words.

Thanks so much.