Thanks for the update. Bummer to see the belt shredded itself like that but it was definitely being driven way outside of its design spec. I've shredded quite a few belts and pullies in my R&D process as well so at least you have company.

What are the marks on the shaft under the pulley that looks like heat discoloration? Almost looks to me like you might have binding going on under load which would make the belts job that much harder.

Also, are you sure you couldn't fit something like this?
https://www.ebay.com/itm/HTD-5M-30T-16W ... dAbDOJsUbA

5mm pitch HTD is super similar in size to XL

seanc56 wrote:What are the marks on the shaft under the pulley that looks like heat discoloration? Almost looks to me like you might have binding going on under load which would make the belts job that much harder.

Those caught my attention too. They line up with the sound insulation so it must be from contact with that. The smaller axles avoid this.

Regarding the 5mm pitch pulleys, they won't fit within the two inner layers of material and the bearings. [edit: They will fit. I didn't find hubless from my vendor, last time I looked.] However, they would be the next step if this gives me any trouble in the future. I would have to add another layer.

Ahhhh, so width is the issue, not diameter for fitment of the pullies. Makes more sense. You're decreasing the tension in the belt by almost 50% with the change so hopefully that helps in a big way. More teeth in mesh is good to stop it from ratcheting as well.

For reference, I am running 36T 15mm wide 5mm pitch HTD pullies with no issues.

Just an update in case anyone considers the JB Weld method I used for adapting the drive shaft to the the socket. It worked for a while, but finally crumbled, which was a possibility I had considered. So, I went with shimming the connection with two u-shaped metal pieces, which tightly filled the gap between the squared end of the shaft and the socket. I just happened to have something on hand that with a little Dremmeling fit perfectly. What I have now works fine, but is a little patched together to get me up and running quickly. I see that the recommended metric pulley is available with a 1/2" bore, so were I to do it again, I would use that.