On my self sourced prusa I have been going back and forth on how best to tension the belts lately. I had a zip tie hack that actually worked out fairly well, but it had a fair bit of slop in it, and I think that helped set up some vibrations and Generally keep it from being the best it can be.
I love my local hardware store. I went there (twice) today and on the first walk there I remembered this piece of hardware that is generally used to tension screen doors to keep them square. I checked one out and I think it will be perfect for my y belt. I may even throw one on my x axis, but I’m not sure if I need it.
Here’s a pic
As you can see in the pic I have been experimenting with a very light y stage. It is perforated hardboard that they sell for hanging tools. The actual bed will go on top of there with 4, 5mm bolts and have the glass and hbp clipped to it.
I have also gone with a double wide skate bearing for the idler end of the x and y axis. If the two ends are aligned, then you don’t need anything else keeping the belt “on” the pulleys. Simple tension holds them there. This has made things much smoother and simpler compared to using fender washers.