Thanks God it wasn’t worse. Glad you and the family are ok. Where are you moving to?
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Not sure if I should start a new thread or just continue here—but I thought I’d share some early results from preliminary traction tests I’ve been doing to optimize the test setup.
For now, I used some random 3D printer belts I had lying around. Judging by their construction, they appear to be Kevlar-reinforced. I’m still waiting on the steel-reinforced Maslow belt that Bar kindly sent me—I’ll test that as soon as it arrives.
Test Setup
The grips aren’t ideal for this kind of testing, but so far, the belts aren’t rupturing within the grips and there’s no noticeable slipping, so I consider the data usable. The extensiometer I used is also not the most suitable one for this setup—it introduces a bending moment that adds some error. To reduce this, I preload the belt with 50 N before attaching the extensiometer. The values between 0–50 N are extrapolated under the assumption of linear elastic behavior. From there, I stretch the belt at 2 mm/min until it breaks.
Results
The x-axis shows elongation in %, and the y-axis shows the load in Newtons. On the right are some key outputs:
- Fmax
- Slope of the linear part (E)
- Elongation at rupture (A)
At first glance, the behavior appears quite linear up to failure, and the three tests yielded very consistent results. The belts ruptured between 5.2% and 5.5% elongation, with a slope of approximately 170 N per 1% elongation—meaning the belt stretches by about 1% for every 170 N of applied force.
One small kink appears in the data at around 4% elongation. This is an artifact caused by the removal of the extensometer just before failure to avoid damaging it. As a result, the actual elongation at rupture is likely slightly lower than recorded. For calculating the elastic constant (E), only the data prior to this bend was used, so this artifact has no impact on the slope estimation.
Break Images
In every test, the Kevlar strands broke all at the same location.
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This is super cool!! @Lais I Created a new thread just for belt stretch, mind moving the post over there? X & Y Accuracy Analysis: Belt Stretch - #12 by kyleschoen
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Oh, I missed that thread. I will move it over, as soon as I figure out how to best do it on my phone… I’m away from my computer right now.
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Dano wrote:
OMG. 5lanes of LA traffic . Amazing no major injuries . Glad you are safe!
5 lanes of Phoenix traffic, in the middle of lunchtime. I somehow didn’t hit
anyone and nobody hit me.
David Lang
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Tim Seidlitz wrote:
Thanks God it wasn’t worse. Glad you and the family are ok. Where are you
moving to?
northern phoenix area (glendate, az, near the 101 and 17)
much bigger house, hopefully I can organize and eliminate storage, and have a 3
car garage I hope to setup as a show rather than haivng it tied up as storage.
a 14x22’ room to be a library (need to build rolling bookcases to hold enough,
two empty bedrooms (one for general electronics/computers, the other for 3d
printing/laswer/small cnc) and I should be able to put in anchors in the garage
for the maslow.
David Lang
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