I have a read a bunch about belt tensioning and as I assembled my new machine the other day had an idea. I didn’t see this one in here already but someone else may have already thought of it and posted something like this. My thought was to swap out the buckle bolt for a longer one, allow a small gap between the rail end plate and the buckle, and add a precision spring to the outside of the end plate with a nut and washer to preload the spring. I mocked up some hardware and took a couple pictures to convey the idea. Assuming I can figure out how to post pictures I will add them to this. For the pictures I grabbed a bolt that I will need to find a slightly longer version of and used a piece of polycarbonate to represent the end plate(s). I figure if the springs are well matched in compression strength then you can balance belt tension by simply compressing them to the same lengths. Further you can adjust overall tension by adjusting pre-load or spring k factor. I have a handful of precision springs from Swagelok metering valves that I figured may work well. Any thoughts from you all are welcome…
I think one of the design features on the original clips is when it is tightened it forces the front of the clip down to the rail compressing the belt so it will not slip. Not sure how much down force this will apply to the belt?
Great design, lets find out if it works!
Agreed, that was one of my concerns too. I might try it to see how it works anyway and report back here.
The only way to get variable tension on the belt would be for a space between the frame and the clip on the clip side of the frame. The clip cannot rotate or the gantry runs into it. Many people when tightening up the stock belt tension guides twist them because they do not hold them with a pair of pliers when tightening. So if your belt tension clips twist you will have issues with homing.
I think it is a good idea but the spring would do nothing to tension the belt on the other side of the frame with no space to pull the belt tighter. Once the belt tensioner hit the frame that would be as tight as it would get. Then only making the belt shorter would increase tension which is how it works in the stock configuration.
Perhaps I just dont see the advantage of this setup. Please tell me how you are tightening the belt and would you use a torque wrench to tighten the bolt to a specific setting to balance both sides of the Y? The only thing I see that this does would give the belt some cushion, depending on the spring tension, in case of a crash.
You are right. I would need to leave a gap so the spring could pull the clip toward the end plate. I think in reality the designed process is more than adequate but you just need to take particular care during assembly to balance the belt tensions
Been meaning to update mine slightly, but they have been working without issue. Which machine, by the way?
I have a pro xxl. I just put it together and I tend to think the belts are likely just fine as designed but thought I would share my idea I case anyone else was looking for a self tensioning setup.
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