Just curious if anyone has experience with rims machined from Delrin? Aluminum works well but Delrin is easier to machine so I was thinking of making a set from Delrin. Seems like it will be strong enough for pneumatics… just curious if anyone has used or is using Delrin made rims. Thanks!
Most people refer to that material as POM. Maybe that can help widen your search results. IDK
Idk before I found esk8 I’d always known the stuff as delrin. I feel like POM is an esk8/engineering terminology for it.
Delrin’s name brand, kinda like Xerox or Kleenex.
aka Acetal (another term to expand the search)
Idk where any of them exist in the wild but yes
Delrin is a dream to machine. Two things to keep in mind when doing it.
If taking a “fairly” deep cut with an endmill, (1/2 the diameter or more) when the tool exits, the material can snap away, leaving a small chunk taken out.
Also, if you want the part to look “perfect” deburr all the edges in the program with the correct tool.
Hand deburring delrin is very hard to make look good.
(White is a little more expensive, but you could dye it any color)
The only thing I would be concerned with, is a VERY hard impact could crack it, without become visible right away. Aluminum would deform, and you’d probably notice it.
Interested to see what you come up with.
I’ll be sure to put a small chamfer on the edges. I don’t ride crazy enough to crack them (at least not on purpose!).
Saw a cool tip online about sneaking up on the tolerances for fitting the dowels when flipping parts. Feel stupid for never considering it myself, but my dowels were slightly loose when I flipped the aluminum wheels and it showed in the final alignment of the two pieces. I can probably mill the Delrin in 1/5th the time of aluminum. And most importantly can customize to fit my 16mm axles…
I’ll stick with black as that’s the deck color.
Thanks to everyone for the input.
Tires from Hoyt St arrived today
Got one wheel milled from the POM / Delrin. Fit seems pretty good. Still need to make the opening for the inner tube and get shorter 5mm bolts. Also need to redo my 44T pulley as the bolt pattern is different. But hopefully ride on them soon. Definitely stronger than I thought. I went with a 3 bolt pattern to keep the spoked areas as thick as possible - probably didn’t need to do that - hard to see this wheel cracking under my riding conditions. Sneaking up on all of the fittings was nice - no slop anywhere - nice tight fittings for the larger bearings. I like this tire profile more than my 8" ones…
personally, I’ve found that cutting a triangle with rounded corners is better than cutting relief into each corner of a hex as far as strength goes. (for the holes where it looks like you’re planning to put hex nuts in). Maybe when I have some time ill run some FEA to actually confirm that its stronger quantitatively.
I just looked at the smallest bit I have (0.078”) and used that to round the corners but still leaves enough flat edges that the nut won’t turn. But I also threaded the holes on the half with the nut so I’m thinking the lock nut may be overkill? But I don’t mind over designing things for ESK8… maybe I’ll sketch a triangle next time and see how that works out…
so youre saying the screw already threads into the hole before going into the nut? I dont think its considered a good practice to have two non rotating threaded features stacked like that. Unless youre relying on the deformation of the plastic, It’s unlikey the threads cut in the plastic align perfectly with the threads in the nut in the hex.
on a seperate note, I wouldnt advise using threadlocker with plastic, so probably a mechanical threadlocker is the way to go. I like locknuts.
Agreed. The threads don’t align which is a small problem, but with some force everything seems to tighten up alright. . I should probably pick one, either thread the receiving piece and no lock nut, or have a clearance all the way through and use a nylon lock nut. But in the end, threading and the nylon lock nut works and seems very secure. Certainly not a best practice and my ME friends will probably frown on this technique.
how heavy is the hub? that is super thick
594 grams or 1 lb 5 oz
I imagine that’s heavier than most but I weigh 230 lbs so I don’t think it makes a big impact overall
Every gram counts.
Can you skeletonize the structure any more?
The more rotational inertia the wheels have the smoother it will be and the better it will handle rough terrain at speed, for a heavy rider I think overkill hubs is the right move
You increase rotational inertia by the ratio of mass in the core to the mass on the rim. Even mass throughout the wheel actually lowers rotational inertia. You want most of the wheel mass to be towards the edge and as little in the middle as possible.
Per the same amount of mass, redistributing it to the edges will increase the rotational inertia because inertia is integral from 0 to R of r^2 dm, but having the mass vs not having the mass will increase inertia
I plan to ride them as is and hopefully get a smooth ride. Can always put them back on the CNC and remove material…