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Author Topic: Toboggan Plastics Comparison  (Read 429 times)

Offline DMarrone

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Toboggan Plastics Comparison
« on: October 04, 2018, 12:21:07 PM »
A few years back myself and a few other mused about the best way to test the sliding characteristics of High Density Polyethylene vs Ultra High PE.  We've compared these side-by-side on our winter trips for a number of years and kept going back and forth on whether we could notice the UHMW-PE sliding better or not.  I think Kielyn and I devised a pretty good, low-tech test and finally have the video edited to show the results.

You can find it here:
https://youtu.be/kOEQ_PNnN3A

SPOILER ALERT:

No difference in ease of pulling between the two!

Having said that the UHMW-PE is much more flexible and durable in cold weather, especially getting to -20C and below.  I've summarized my thoughts on the plastic differences as well as the applications for the different lengths of toboggan on a page here:

https://lureofthenorth.com/toboggan-selection-warranties/

If anyone else has any thoughts or comparisons between the two plastics I'd love to hear about it.
Lure of the North
http://lureofthenorth.com

Offline K.

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Re: Toboggan Plastics Comparison
« Reply #1 on: October 04, 2018, 03:36:04 PM »
Interesting results. I've long been of the opinion that the UHMW was better based on comparing non-identical sleds with merely similar weights, but have never seen any attempt made at such a side-by-side comparison with identical units. In addition, while textbooks imply a significant difference in coefficient of friction between the two, these do not cover the case where snow is the substrate, so there's certainly good reason to do this kind of experiment. You went to quite a bit of effort to do a controlled experiment, so at the risk of sounding like quibbling, my one thought would have been to do the same experiment, but on a gentle slope such that no pulling is required; just let them go and see how far they slide. That way the force applied to each sled is identical, instead of being merely similar, and you wouldn't need 1000 pounds either. Although, that amount of weight is quite amazing, and brings to mind another element which I've never been sure of. In skiing and skating, the glide that is achieved is due in part to a microscopic layer of liquid water that is formed by the pressure exerted. With a larger surface area, the pressure under a toboggan generally would be much lower than under a skate or a ski, and I don't really know the details of the phenomenon such as what minimum pressure it cuts out or how much the speed also matters, so I've generally assumed there is no pressure melt for a toboggan.  However, with your experiment here of increasing the weight one bin at a time, you could test that idea, by observing if there was a sudden increase in distance obtained at a certain number of bins. Last comment, at -20 most skiers will know it  is hard to get the pressure melt and glide, so if that effect does apply to toboggans, then temperature is a variable here too. Regardless of all that, great video and very entertaining.

Offline AunNordDuNord

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Re: Toboggan Plastics Comparison
« Reply #2 on: October 04, 2018, 10:15:21 PM »
My wife that run a grade 10 outdoor head program use our sled made of UHMW and the one I made for the school that are identical but made out of HDPE and she always come back saying that our sled is way easier to pull than the school sleds. I tried as well and I find the UHMW glide more easily than the HDPE sleds! Also I found that the UHMW is more scratch resistant than the HDPE version...

Offline DMarrone

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Re: Toboggan Plastics Comparison
« Reply #3 on: October 05, 2018, 07:44:33 AM »
do the same experiment, but on a gentle slope such that no pulling is required; just let them go and see how far they slide. That way the force applied to each sled is identical, instead of being merely similar, and you wouldn't need 1000 pounds either.

This was the first test we did, when we first started carrying UHMW.  Granted we didn't spend enough time setting up a proper course for the sleds to slide down.  We were still living in the city at the time, so sent them down a driveway.  They tended to swerve/ flip/ veer off course, so we abandoned that test without reaching a conclusion.


temperature is a variable here too

Our original intention was to do multiple tests across 4 temperature ranges.  -20 would be the cold test, we were hoping for an extremely cold, moderate and around freezing test, but winter tends to be a busy time  ::)  I think if we'd seen more variation we might have been more interested to continue comparing differences at different temperatures.

Lure of the North
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Offline DMarrone

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Re: Toboggan Plastics Comparison
« Reply #4 on: October 05, 2018, 07:46:25 AM »
My wife that run a grade 10 outdoor head program use our sled made of UHMW and the one I made for the school that are identical but made out of HDPE and she always come back saying that our sled is way easier to pull than the school sleds. I tried as well and I find the UHMW glide more easily than the HDPE sleds! Also I found that the UHMW is more scratch resistant than the HDPE version...

There have been times on trip where we've been sure we could tell a difference between the two plastics, and other times where we've been sure that there's no difference.  That might go back to K's note about temperature.  Maybe you just pack your personal sled much nicer than the student's pack the school's sleds  ;)
Lure of the North
http://lureofthenorth.com

Offline Snowbound

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Re: Toboggan Plastics Comparison
« Reply #5 on: October 05, 2018, 08:32:19 AM »
I've been making and testing laminated wood sided toboggans with plastic bottoms for years, See here  https://www.wintertrekking.com/community/index.php?topic=2862.15

I've noticed no substantial difference between the two plastics. 

If anything the main difference I've noticed is the older the plastic with more abuse and scratches, the harder it is to pull.

Offline DMarrone

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Re: Toboggan Plastics Comparison
« Reply #6 on: October 05, 2018, 11:16:14 AM »
I've enjoyed checking out your toboggans at the WCS in the past - beautiful craftsmanship that's for sure!
Lure of the North
http://lureofthenorth.com