If you are REALLY tight on resources, one of the simplest tensioning techniques is to stick a big sprocket into the middle of the loose chain run - without actually attaching the sprocket to anything - it just floats in the middle of the chain run. The sprocket has to be big enough to take up all the slack, and is held in place by the chain run itself, with chain running above and below it holding it "securely" in place.
Don't know if this makes sense, but it does work decently well. Surprisingly the sprocket won't fall out unless directly disturbed...
This is a hack we used on 188 pretty effectively back in the early days.
__________________
In life, what you give, you keep. What you fail to give, you lose forever...