It's a grader, not a scraper
Thanks for your concerns.
The speed is very slow, already before the worm drive, so heat is not an issue.
The white gear is high quality PA. Sadly, the red worm is relatively low grade plastic. As the transmission is currently pretty exposed, dirt can enter the area and that together with the rather high surface pressure between gear teeth and worm will damage the worm over time. So far it has held up very well, though and as it is much cheaper and much smaller than any alternative worm I could find, I'll simply replace it once it wears out. I am currently still in the prototyping and testing phase and will look into doing a shield to keep dirt out.
Without a lathe or mill, I had to simplify the design, but this is not an area I am worried about.
Anyway, as this is Hemi's thread, I'd suggest that if you want to discuss this further, we do that in the thread I opened about my grader. I posted my picture for Hemi to see what I was comparing and I am fully aware that Hemi's grader is in a totally different ball park. But as sizes are comparable between our machines, so should the necessary power and that's why I posted a shot of my low-tech solution.
Cheers
Jens