Expand Quote
Expand Quote
Expand Quote
That durometer tester should still be accurate at the ends of its scale, to 99a. 101+ would all read as 100a
It's not gonna be like a cheap bathroom scale and read all wonky at the ends of its range.
"Hardnesses above 95 on the A scale should not be specified because the upper accuracy limit of the instrument is being approached. Accuracy at the lower end of the D scale is also limiting and values below 25D are questionable."
https://moldeddimensions.com/durometer-hardness.php
Tbh, I think we're gonna need a materials or chem engr or something to solve this. If only Big Cat would appear..
I know what you're saying and maybe it's back to using a spring for measuring?
Idk. Maybe something to do with bending/denting the urethane vs piercing it like the B scale does?
Seems like just the skin on new vs old wheels might affect things. Even leftover mold release with piercing.
And realistically, if they can't test that duro, then they'd have trouble labeling it for sale. I'm not talking about skate wheels, I mean industrial stuff.
If you're just saying it'd be better to test 99a wheels on a different scale then I agree with you.
I'd prefer C scale cuz it doesn't pierce. But since the load is crazy high it might not work for 70-80a stuff?
A third tier of middle load scales would be nice.
Piercing the material seems like it could be affected by how easily that material tears.
https://www.ptc1.com/Durometer-A-408
Check out specs and look at the force curve graph
To me that says if there's difficulty measuring the extreme ends of the range it's not because of the accuracy of the tester.
I'm thinking issues with the material or even that the math used makes the ends of the range less accurate.
https://www.ptc1.com/DurometerHardnessChart
But here they say to use B scale testers for above 90a, below 20d
https://www.ptc1.com/Durometer-Test-Stands
They can be used handheld.. just pointing out a possible source of error in that insta pic
https://urethaneusa.com/resources/what-is-durometer/
95a industrial urethane
**edit
I got a chance to try F4's and OJ elites?
Old, worn, super-wide conical full F4's felt a lil softer than my classic classics.. Slide was WAY better! Almost shot out on the first one, 2nd one I pushed harder and it got away from me. Was even able to eek out a slow speed bs powerslide. Setup was also super surf so that might have added to it..
Slippery but quiet compared to classic formula. I think it'd take me a few days to get used to them.
Only got to check out the OJ's for a sec. I think they were 101a hardline elite whatever.
Hard, harder than classics but not crazy jarring old F1 101a. Seemed pretty fast.
Slid nice.. Lil bit of a bark, more controlled than F4's above. Broke into a slide more easily than classics.
Classics..
Wow. Grippy compared to more modern formulas. I'm liking them again since the weather warmed up.
Below 50*f they start getting too grippy, 40*f they bark like a goose. But I'm over skating in weather that cold.
How do you guys with multiple setups deal with riding F4's and Classic formulas? Seems like it'd be tough to go back and forth.
For the scales, there are just different scales created to test different materials. A Rockwell hardness test is the usual one everybody mentions. This leaves a divit in the material and measures how far the instrument penetrates into it.
If your interested in the mathematics behind it, and how other scales compare to eachother check this:
https://web.calce.umd.edu/TSFA/Hardness_ad_.htm
Ooh! Does slap have a resident ME? Please say yes.. I'm a burnout so it'd be great to have your help with some of this geeky stuff. And maybe we can lure THE Big Cat over here!
The different durometer thing is cuz wheels went past 99-100a hardness. 101a, 103a, 104a, etc doesn't/shouldn't exist.
The A scale was great for 70's wheels, 70-85a duro? I can't remember the first 99a wheel I saw (maybe Gizmo's?) but I think 97a might have been the hardest duro for most of the 80's.
101a reads like 100a on the tester, no indentation of the wheel, so they moved to the next scale, B.
My gripe is B uses a point vs blunt indenter. Seems like you could be tearing the material but idk..
D scale seems to only be used for plastic cores? Did Darkstar (or other AEND companies) ever use this scale? Idr
I never really see the C scale used for anything. Maybe for composites?
I'm used to seeing Rockwell and Brinell hardness testing for metal but don't recall seeing it used for urethane. Thanks for that link, was interesting, but I didn't see math for durometers. I imagine it's just linear, and inverse? 0 indentation = 100a, full indentation = 0a. But how do you do that when you can only really measure 1a and 99a? I feel like I'm having a stoner moment..
Topic: Wheels Thread (Read 797148 times)