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Self-made carbon ski pole

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elm.
Posts: 1492 - Karma: 13,497
Maybe some of you nerds out there might be interested in this and maybe not. Me and a group made a (single) carbon ski pole for an advanced composites class in college.

First we took an old ski pole from goodwill and stripped the paint on a lathe.



We polished it for easier demolding



Wrapped it in carbon (7 layers of prepreg. Can't remember the thickness of each layer, but it ended up being about 3x as thick as an aluminum one)



The autoclave was broken, so we had to use a vacuum oven. Bagged it and cured for 4 hours



Demolded. Added handle and basket. Total length was around 38". Descent park pole size. No pointy end, though, just a tube.



Did a 3 point bend test on it. It held up to 300lbs before plastic deformation, which was unsatisfying. Twice the strength to weight ratio as aluminum. We didn't fully break it so it's still usable.


Total cost of project was about $100, although all the materials at my college are donated so it was free. Maybe some NS'ers out there might be interested.
I graduate monday so if any ski companies out there want to hire me here's your chance. I'll take no less than $140K salary, and I expect 3 months of vacation time over the winter.
Dec 7 2019 3:06PM
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gravel
Posts: 5518 - Karma: 42,202
that’s sweet! how much harder would it be to make it tapered to a point? 300lb before deformation but what is the distance between the supports? technically aren’t you measuring a plastic deformation torque, not force?
Dec 8 2019 1:52AM
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Non_State_Actor
Posts: 4806 - Karma: 17,041
Cool project!

Any physicist out there care to calculate the force my 140lb hip applies laterally to a ski pole with a portion of the tip buried in relatively soft snow when I eat shit? My last pair of poles look like DH poles.
Dec 8 2019 2:40AM
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Youngm_IPCME
Posts: 1082 - Karma: 2,851
mystery3Cool project!

Any physicist out there care to calculate the force my 140lb hip applies laterally to a ski pole with a portion of the tip buried in relatively soft snow when I eat shit? My last pair of poles look like DH poles.


The most extreme case for that scenario is a 3-point bend, like the one above. If you can post the dimensions, I can try to estimate the force you applied.
Dec 8 2019 11:04AM
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elm.
Posts: 1492 - Karma: 13,497
toastthat’s sweet! how much harder would it be to make it tapered to a point? 300lb before deformation but what is the distance between the supports? technically aren’t you measuring a plastic deformation torque, not force?


It would be difficult to get the carbon to conform around a point. I think best way would be to add a metal insert at the end of the hollow pole.

If I remember correctly, the distance between the supports was 24", so not the entire length of the pole.

Torque usually has to do with twisting, but I see what you're getting at because if you change the distance between the supports the peak load would probably change. We were testing the modulus (stress/strain) and peak load. The modulus would not change as you move the supports closer or farther apart because it is a ratio.
Dec 8 2019 1:55PM
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elm.
Posts: 1492 - Karma: 13,497
mystery3Cool project!

Any physicist out there care to calculate the force my 140lb hip applies laterally to a ski pole with a portion of the tip buried in relatively soft snow when I eat shit? My last pair of poles look like DH poles.


I think you answered your own question, 140lb's of force. Unless I'm missing something, here are the dimensions of the pole, averaging the taper:

ID = 5/8"
OD = 13/16"
Length = 34" (without grip)

We actually did a 3-point bend test on an aluminum pole and the peak load was 108lb's before plastic deformation. Same test setup as the carbon one.
Dec 8 2019 2:19PM
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Youngm_IPCME
Posts: 1082 - Karma: 2,851
elm.I think you answered your own question, 140lb's of force. Unless I'm missing something, here are the dimensions of the pole, averaging the taper:

ID = 5/8"
OD = 13/16"
Length = 34" (without grip)

We actually did a 3-point bend test on an aluminum pole and the peak load was 108lb's before plastic deformation. Same test setup as the carbon one.

You’re neglecting the energy from him falling from some amount of height and moving forward. If you assume the pole is just yielding, you can back out the force. This isn’t the best approximation, but it’s simple.

**This post was edited on Dec 8th 2019 at 10:25:42pm
Dec 8 2019 10:23PM
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Non_State_Actor
Posts: 4806 - Karma: 17,041
elm.I think you answered your own question, 140lb's of force. Unless I'm missing something, here are the dimensions of the pole, averaging the taper:

ID = 5/8"
OD = 13/16"
Length = 34" (without grip)

We actually did a 3-point bend test on an aluminum pole and the peak load was 108lb's before plastic deformation. Same test setup as the carbon one.


Young_IPMCYou’re neglecting the energy from him falling from some amount of height and moving forward. If you assume the pole is just yielding, you can back out the force. This isn’t the best approximation, but it’s simple.

**This post was edited on Dec 8th 2019 at 10:25:42pm


This is what I thought, the velocity at which I'm traveling along with the leverage I'm imparting upon the shaft of the pole would make it a much more complicated calculation.
Dec 8 2019 11:48PM
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gravel
Posts: 5518 - Karma: 42,202
elm.It would be difficult to get the carbon to conform around a point. I think best way would be to add a metal insert at the end of the hollow pole.

If I remember correctly, the distance between the supports was 24", so not the entire length of the pole.

Torque usually has to do with twisting, but I see what you're getting at because if you change the distance between the supports the peak load would probably change. We were testing the modulus (stress/strain) and peak load. The modulus would not change as you move the supports closer or farther apart because it is a ratio.


Twisting would be torsion I think... But as far as torque v force, if you're applying a load in the center of a beam with two side supports then the only thing maintaining its structure is the resistance to the moment caused by that force. I'm on board with modulus though, which is a material property.

How is the carbon laid around the mold of the pole? Is it sheets of carbon fiber?
Dec 8 2019 11:59PM
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Non_State_Actor
Posts: 4806 - Karma: 17,041
Young_IPMCThe most extreme case for that scenario is a 3-point bend, like the one above. If you can post the dimensions, I can try to estimate the force you applied.


Yeah, I'm 5'7" 140lbs, poles are 120cm aluminum, skis are 180cm, the mid-point of the bend is roughly 50cm from the top. I'm not a super fast or terribly aggressive skier but I fall pretty hard sometimes. One bent when falling after dropping a ten foot cornice and rolling with the pole under my hip.
Dec 9 2019 12:28AM
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elm.
Posts: 1492 - Karma: 13,497
toastTwisting would be torsion I think... But as far as torque v force, if you're applying a load in the center of a beam with two side supports then the only thing maintaining its structure is the resistance to the moment caused by that force. I'm on board with modulus though, which is a material property.

How is the carbon laid around the mold of the pole? Is it sheets of carbon fiber?


We cut out 7 sheets and wrapped them around 1 by 1, offsetting the start so there would be no seam.

You could also take one sheet and roll it like a burrito, but we figured it would cause more wrinkles with the taper
Dec 9 2019 1:04AM
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Youngm_IPCME
Posts: 1082 - Karma: 2,851
mystery3Yeah, I'm 5'7" 140lbs, poles are 120cm aluminum, skis are 180cm, the mid-point of the bend is roughly 50cm from the top. I'm not a super fast or terribly aggressive skier but I fall pretty hard sometimes. One bent when falling after dropping a ten foot cornice and rolling with the pole under my hip.


This is unlikely, but do you also have the thickness of the aluminum tubing, the diameter at the top, and the diameter at the basket? That’s the key thing here aside from the length and point where it bent, I should have mentioned
Dec 9 2019 1:44AM
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Non_State_Actor
Posts: 4806 - Karma: 17,041
Young_IPMCThis is unlikely, but do you also have the thickness of the aluminum tubing, the diameter at the top, and the diameter at the basket? That’s the key thing here aside from the length and point where it bent, I should have mentioned


Ballpark...8-9mm at the narrowest point about the basket and 16-17mm below the handle.
Dec 9 2019 2:39AM
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xxACIDTRIPxx
Posts: 5980 - Karma: 8,175
Too much physics and biochemistry itt
Dec 9 2019 7:44AM
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meadows69
Posts: 104 - Karma: 151
I recognize that lab. Ahh the memories. cool to see people are still building ski shit. larson still teaching advanced composites off a damn overhead projector like it's1994?

* Also our ski basket mold from tooling class might still be around you could see if the baskets we made fit it. One of the dudes who made that tool works as a design engineer for k2 now. Dream big homie.

**This post was edited on Dec 9th 2019 at 11:36:46am
Dec 9 2019 11:34AM
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elm.
Posts: 1492 - Karma: 13,497
meadows69I recognize that lab. Ahh the memories. cool to see people are still building ski shit. larson still teaching advanced composites off a damn overhead projector like it's1994?

* Also our ski basket mold from tooling class might still be around you could see if the baskets we made fit it. One of the dudes who made that tool works as a design engineer for k2 now. Dream big homie.

**This post was edited on Dec 9th 2019 at 11:36:46am


She actually just uses a whiteboard and a note sheet now to teach. Small world

I just finished my last final ever, so i prlly wont go in that building ever again. I don't remember seeing it, though
Dec 9 2019 1:48PM
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