UAF Sled Study

The Winner is Kuzmin!sledsliding5

Test parameters were combinations of heavy/light loading and slow/fast speed.

Note that by the time the UAF Engineering students had instrumentation and equipment ready the snow season was almost over so the trials were in temperatures near zero C and many other variables were not explored. I am surprised that HDPE was not comparable to UHMW, not as fast. I do expect HDPE to be best in extreme cold. I think most knowledgeable mushers use UHMW over cheaper HDPE in warmer conditions because of the much better wear/abrasion resistance in case of exposed dirt, rocks etc.

I think that boundary layer lubrication theory fits the limited relevant data best for all conditions. According to that, with a thicker film/boundary layer of water and adsorbed vapor, in warm temps the primary variable factor for most materials is corresponding surface tension/contact angle of a water droplet. Years ago I made a little hinged table with different plastics and measured not contact angle directly but angle at which a drop of water began to roll off. That would be static friction/drag vs. dynamic.

The prelimary report from UAF study below:

Authors Danny Eagan, Ian McKee    5/1/18

Test Parameters

Test Samples

1: Prairie Bilt, Fast Trax™ Proprietary Blend, yellow, shiny (1.75” wide)

2: Prairie Bilt, Fast Trax™ Proprietary Blend “White Lightning”, contains lubricating additives, white, shiny (1.75” wide)

3: Tim White HDPE

4: Tim White UHMWPE

5: Tim White, HDPE “XH”, white, very waxy (1.375” wide)

Weight: Approximate loaded weight based on 50 lb sandbags

  • Light: 150 lb
  • Heavy: 250 lb

Speed: approximate speed throughout duration of test (0.5 miles for Test 1, 200m for Test 2)

  • Slow: ~5 mph = 8.04 km/h
  • Fast: ~ 12.4 mph = 20 km/h (Test 1)
  • Fast: ~9.3 mph = 15 km/h (Test 2)

Test 1 (3/29/18): Runner Samples 3 and 4

Raw Data:

Table 1: Test results for runner sets 3 and 4

Runner Set 3: Tim White HDPE

Load Weight

Speed

Average Pulling Force (lb)

Heavy

Slow

42.9

Heavy

Fast

47.2

Light

Slow

22.7

Light

Fast

32.9

Runner Set 4: Tim White UHMWPE

Load Weight

Speed

Average Pulling Force (lb)

Heavy

Slow

20.9

Heavy

Fast

22.6

Light

Slow

11.9

Light

Fast

16.5

Figure 1: Raw data collected during testing of runner samples 3 and 4

Processed Data:

Figure 2: Preliminary results for all testing configurations of samples 3 and 4

Test 2 (4/213/18): Runner Samples 1, 2 and 5

Raw Data:

Table 2: Test results for runner samples 1, 2, and 5

Runner Set 1: Prairie Bilt, Fast Trax™ Proprietary Blend

Load Weight

Speed

Average Pulling Force (lb)

Heavy

Slow

23.56

Heavy

Fast

44.96

Light

Slow

35.91

Light

Fast

35.44

Runner Set 2: Prairie Bilt, Fast Trax™ Proprietary Blend “White Lightning”

Load Weight

Speed

Average Pulling Force (lb)

Heavy

Slow

56.46

Heavy

Fast

64.81

Light

Slow

52.01

Light

Fast

44.07

Runner Set 5: Tim White, HDPE “XH”

Load Weight

Speed

Average Pulling Force (lb)

Heavy

Slow

22.29

Heavy

Fast

26.83

Light

Slow

29.55

Light

Fast

28.14

Figure 3: Raw data collected during testing of runner samples 1, 2, and 5

Processed Data:

sledsliding4

Figure 4: Preliminary results for all testing configurations of samples 1, 2, and 5

Combined Results (Both Tests)

sledsliding5

Figure 5: Preliminary results for all testing configurations of all runner samples

Lubrication in sliding is also the subject of research in medicine. For example:

>It is becoming clear that, whether the gliding is cartilage on cartilage or tendon on tendon sheath, the basic biologic strategies are very similar. Specifically, the gliding surface in both cases contains a fixed lubricating glycoprotein, called lubricin,8,9 in addition to the high-molecular-weight glycoprotein, aggrecan, which tends to disperse the collagen fibrils and makes the surface structure more resistant to compression10,11 This type of lubrication, called boundary lubrication, is fundamentally different from the lubrication provided by an intervening fluid film, which is called hydrodynamic lubrication9,12-14 Indeed, it may be that the synovial fluid, comprised chiefly of hyaluronan, is more of a high viscosity nutrient delivery vehicle than a lubricant.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1370263/

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