Rock Tumbler Model T Motor Drive Belt

prusaprinters

<p>My motor drive belt on an older Thulmer's (rock) Tumbler Model T broke after about a week of use. I didn't want to wait for a replacement or spend $12 for three so I looked into making myself a new one using 1.75mm Hatchbox TPA filament.</p> <p>After some research it seems the newer version of the Model T tumbler has a thicker belt (newer belts are around 1/4 inch thickness I gather) whereas the older Model T has a thinner belt (I measured the one it came with at just over 1/8"). I have an older Model T with the thinner belt.</p> <p>Initially I simply took a length of 1.75mm Hatchbox TPA and made my own 1.75mm thick belt by heating the two ends of the filament on a propane burner and pushing them together to make a loop and then clipping off the smooshed out part at the joint after pressing the ends together. I made a few belts this way which worked well for a little while. The first first broke after about a day (it didn't break at the joint surprisingly).</p> <p>The second belt I made out of a length of TPA filament was still running OK after a day but I expect it will break as well and so I wanted to try to print something thicker and stronger so I printed this toroid belt out of the same Hatchbox TPA and swapped it. So far, the durability has been worse with a printed ring than a length of TPU of the reel made into a loop.</p> <p>I haven't printed TPA before but I initially tried using the same settings as eSUN PLA+ (215C and 60C bed) and found it wasn't an issue with my bowden setup (which was good to see). This was not hot enough though because it had a few loose strands off the printer and after an hour or so of use on the Tumbler, the belt started to delaminate quite a lot (shredded apart).</p> <p>I then tried again printing it hotter (235C) to see if the layers would bond better, which they did, but it wasn't perfect so I ran the printed belt over my propane burner to make any loose strands adhere better and ran it on the tumbler. This belt delaminated less but broke after approximately 12 hours on the Tumbler. Another made the same way has lasted 24 hours.</p> <p>The belt I started with is a toroid that has a 100mm inner diameter and a 0.135" torus diameter. I have the motor pushed all the way over in the bracket on the tumbler to tighten a belt as much as possible and this seemed to work but seemed just a little looser than I would like so I made a 98mm inner diameter version which also worked but may be just a little bit tight so I am sticking with a 99mm inder diameter belt given that my motor adjustment is all the way over to max tightness. I included all 3 STL files.</p> <p>I would have liked to see these belts survive longer but at a minimum they allow the rocks to tumble when there are no other replacements belts available. It is interesting to me how a length of TPU cut off the reel that is made into a loop by heating the ends of the propane burner and pressing them together has lasted longer than a 3D printed ring of the same material with twice the diameter printed at 235C and 0.28 layer height... It seems like the belts need additional heat treatment to strengthen the layer bonds after printing to me.</p> <p>Enjoy!</p> Category: DIY