Top speed on rollerskis?

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PortlandORXCER
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Top speed on rollerskis?

Postby PortlandORXCER » Fri Feb 04, 2011 3:02 pm

Here's a question that pops up in my mind once a year: how fast can one go downhill on rollerskis? (I'm not going to find out for myself)

In his book Momentum, Pete Vordenberg claims that he and two of his friends were descending a hill at 60 MPH (yes, MPH). At first I thought they were crazy but now I'm almost calling BS (with all due respect to Pete). I just don't think you could reach that speed on rollerskis. There have only been two hills that I've descended that were steep enough to reach that speed on a bicycle.

What say ye? Think you could reach 60 MPH?

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Postby UPrSKr » Thu Mar 24, 2011 1:56 pm

That sounds a little crazy. I do know that Pete, as an extraordinary athlete, is probably cabable of going 60mph on rollerskis. You would need a hill with a very steep, relatively long headwall. Shear steepness is more important than length, especially at the bottom of the hill where you will lose top end speed quickly if the slope lessens.

I don't roller ski, but I have been clocked at: 43mph on inline skates on a hill with a 140 foot drop in 1/4 mile (road down a drumlin near Phelps, WI); 55mph on a road bike on a hill with a 316 foot drop in 1/2 mile with a 220 foot drop 1/2 mile lead in that could be pedaled up to 46mph in the big ring (Gratiot Lake Rd., Keweenaw Co., MI); and 76mph on downhill skis on a hill with a 360 foot drop in 1/4 mile (Marquette Mountain radar run).

I figure it's within the realm of possibilities. If you knew the dimensions of the hill, you could determine pretty quickly if it was possible anyway. My experience has shown me that if the speed wasn't measured, it's almost certainly exaggerated.

Nowadays, I prefer to keep my speed on in-line skates well under 40mph by doing slalom turns or standing up down the steepest hills catching as much wind as possible. Have fun.

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Postby jt10000 » Thu Mar 24, 2011 8:00 pm

UPrSKr wrote:That sounds a little crazy. I do know that Pete, as an extraordinary athlete, is probably cabable of going 60mph on rollerskis. You would need a hill with a very steep, relatively long headwall. Shear steepness is more important than length, especially at the bottom of the hill where you will lose top end speed quickly if the slope lessens.


I think you'd need a ripping headwind and doubt that that speed is possible. 60mph is around the upper limit a bike can do dowhill w/o a huge wind or drafting cars, and bikes roll faster than roller skis.
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Postby kuan » Thu Mar 24, 2011 8:19 pm

Maybe with inline skate race wheels.
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Postby UPrSKr » Fri Mar 25, 2011 6:03 am

The reason bicycles, and almost certainly roller skis, rarely reach or exceed 60mph is that paved roads are seldom steep enough.

The world record bicycle speed on an alpine ski hill is Eric Barone (France), 222 km/h (138 mph); Les Arcs, France, April 21, 2000. On speed skis, the record holder is Simone Origone (Italy) 251.4 km/h (156.2 mph); Les Arcs, France, April 2006.

Now if a roller skier was cast out of an airplane a top speed of only 120mph (terminal velocity) would be likely, which makes the above records even more impressive.

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Postby UPrSKr » Fri Mar 25, 2011 6:26 am

...And if that ski diving roller skier got into an aerodynamic tuck position the terminal velocity could be increased to 200mph. The world record sky dive with altitude suit is 614mph. Now that's fast.

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Postby jt10000 » Fri Mar 25, 2011 6:47 pm

kuan wrote:Maybe with inline skate race wheels.


I still think they roll slower - larger is better.
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Postby Cloxxki » Mon Aug 29, 2011 2:17 pm

Remember that rolling resistance only ramps up proportionate to speed.

So what matters is aerodynamics. The poles are a bit cumbersome, but when held straight, are nothing more than a thin ferrule at the end of a resistanceless rod.
Rollerskis roll faster than xc skis glide. And XC skis glide way faster than alpine ones. A rollerski outfits, apart from the helmet, is about as aero as a speed skater's, who reaches over 55kph on it's own power, which can be held for a couple minutes (considering the turns cost extra energy on a 1m09 standing start 1000m). And that's with swinging arms.

I clocked 90kph or so on a regular hardtail MTB, with mtb tires on a slope of ~17%. It was long though, and straight. I didn't lower my seat for it, and I have a 39.2" inseam, so go figure my air drag. Triathlon bikes clock 110kph there.
As rolling resistance is less of an issue at ~60mph, and there is no bike taking up frontal surface, no tire knobs and spokes mowing around, and the skier in Hocker position, I guess on "my" hill, a suicide rollerskier would hit 100kph easily. I did pedal up to 60-70kph, but the 89-90kph was held for a significant time. A roller skier would go into tuck at 40kph, and go from 60-90kph faster than a mountainbiker.

For those who want to try, get 4-wheels roller skis for even lower resistance. Best might be custom ones, with 150mm central ones and 100m ones on the ends. Cover them with an aero hood, top and bottom. Put them in pairs on rockers, for rolling smoothness over bumps.
The tracking of longer 4-wheel skis might be good, might be bad.
A low foot position will help top speed a bit.


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