I took my Coker (125mm cranks) on our recently refurbished local velodrome yesterday. Just wondering if anyone else has ridden their Unis on a velodrome?
The velodrome is a 333.33 metre circuit. I did a few sets of triple laps (1km) at about 2:20-2:25 (25km/h). I found that everytime I hit the banking it was like I was peddling uphill. It needed significantly more effort to spin the Coker. Some of that was probably the added effort required to keep balance on the bank, but after a while it wasn’t too difficult. The balance got better but it still felt like I was peddling uphill, despite the fact I stayed on a similar level along the velodrome circuit. So I’m just wondering if there is any reason that you would find require so much more effort on the banking? Has anyone else had experience riding in a velodrome?
I’ve ridden round a cycle velodrome (I think) on a 20" or 24". I’ve also ridden round the speedway track during the burnout competition. I only did a couple of laps on each, so I am not highly experienced. I think the effort in the banking is because it is designed for high speed bicycles, and 25km/h is relatively slow for a bicycle race. The faster you go, the more you can lean into a corner. Just stick to the inner track (if it bothers you) and you won’t have to climb too high up the bank. Good to hear you are finding time to practise distance riding for the upcoming Vietnam to Cambodia ride Ken!
That extra you feel is from the gee forces in the turns. My guess is that it’s compressing the tire more and increasing the tire drag.
Tire drag or “rolling resistance” comes from internal friction within the rubber as it is flexed and unflexed by the contact patch. The molecules rub against each other and heat up the tire. This loss is minimized by a) having less material in the casing, especially rubber; b) eliminating bumps and protrusions that cause localized tire squirm; c) increasing the pressure of the tire to make the casing flex less at the contact patch; and d) reducing overall weight to reduce the need for a flex at the contact patch.
Elite velodrome racing is done on track slicks, which are little more than a thin latex tube (think condom) with a very thin but high thread count casing stitched around it to hold the pressure. The “tread” on a track slick is a milimeter thick layer of sticky rubber that looks painted on. The whole thing, including valve stem, weighs 150 Grams. This “sew-up” tire is glued onto a special lightweight rim and pumped up to between 180 and 240 psi. They feel and bounce just like a superball. They are blast to ride!!
The opposite of a track slick is a mountain bike tire running at low pressure. The knobs squirm around, the casing deflects, and there’s a lot of rubber to bend. Coker tires are a very close second.
So how much extra “weight” do you pick up in the turns? It depends on the track. Most 333.3m tracks are banked about 25-35 degrees, which is not that extreme by velodrome standards. They get pretty steep - I think the 200 meter (?) track built for the Montreal olympics was banked over 45 degrees!! For comparison, 25 to 35 degrees is about as steep as a flight of stairs.
Track designers use an angle that makes the bikes stand at right angles to the track in a 40 mph sprint. The math is pretty simple - there is a one gee force pointed straight down from gravity, and another horizontal gee force that resists the centrifugal force of the turn. You can think of these two forces as the lengths of the sides of a rectangle. The net gee force is the length of the diagonal of that rectangle.
So at full speed on the 28 degree track that I used to ride I was pulling 1.13 gees. I could definately feel this compression, however since I was on track slicks I didn’t notice any additional drag. The Montreal guys were doing radical tactical maneuvers while pulling 1.4 gees in the turns!!
So, what does this translate to at 25kph on a nominal 30 degree track? Not much - about 1.05 gees. But you still might notice it as both extra weight on the seat and pedals and extra rolling resistance.
I find riding on a slant difficult. Riding along the sidewalk and coming to a driveway messes me up. I can ride it fine, but I feel like i have to lean sideways the whole time. So I ride in the street.
Cool, thanks cyberbellum. I’m going to turn up to next weeks track meet- apparently they were talking about us unicyclists- we should be track legal because of the fixed wheel and no brakes. Maybe I’ll join them for a time trial or two, and have a go at the hour record
One other thing, is the 333.33m circuit taken from the inner circumference of the track? If I ride on the inner rim right where the track starts bending upwards I find it significantly easier.
That part of the track is callled the transition. The flatish inner part is the apron, and the rest is the track. It’s easiest to enter the track on the straights. If you have some speed the world tilts and the turns seem flat.
The measurement line (333.3 m) is the black line at the bottom. The red line above that marks the top of the sprinter lane, and the blue line above that is the pacer line (slower riders stay above this line.)
Have fun with the trackies. They’ll really get a kick out of having you at the track, even if they don’t show it. Psyching out the other riders is part of the game, so most of them will seem cold and the rest will be making fun of things. Try a high speed spin on a track bike while you’re at it. Speed modulation on a fixed is very similar to balance on a unicycle.
>This loss is
>minimized by a) having less material in the casing, especially rubber;
>b) eliminating bumps and protrusions that cause localized tire squirm;
>c) increasing the pressure of the tire to make the casing flex less at
>the contact patch; and d) reducing overall weight to reduce the need for
>a flex at the contact patch.
And e) having a wider tyre, which deflects the contact patch less at a
given pressure and weight.
>So how much extra “weight” do you pick up in the turns? It depends on
>the track.
I think it does not depend on the track angle as you seem to suggest.
It does depend on track radius, and on the speed you move. If you
would turn the same radius at the same speed on a flat surface, the g
forces would be the same.
I would suggest that Ken maybe was troubled by a mismatch between the
small lean of his slow Coker (slow by bike standards) and the track
angle. Try riding a unicycle on a traverse slant in a straight line
(which is an exaggerated case of the same). The uni will probably tend
to veer of to the low side and you constantly need to fight that
tendency by forcing the uni uphill.
Klaas Bil - Newsgroup Addict
I have a feeling you might need two points of contact with the ground for such a thing to work? Or at least training wheels on the front and rear. - John Foss commenting on a picture of a one-wheeled vehicle he saw on RSU.
Velodromes are fun to ride in. I’ve only been on the Marymoor Velodrome in Redmond, WA with my road bike. Its really cool when you hit the curve at the right speed, you don’t even steer. Its like going straight but you’re taking the curve.
Marymoor is 28 degrees. Us Pacific Northwesties need to do a Coker/Blue Shift ride out there sometime. Blue Shift may be able to hit the right speed for that track angle.
Yes, this is very true; gee forces depend only on the speed and radius of the turn.
The reason I based my analysis on the bank angle is that tracks don’t generally publish the radii, but they do publish the maximum bank angle. Since velodromes are very synthetic environments it is reasonable to use either for the analysis.
Bikes roll just fine at low speed on the banks, but I can see your point about uncycling on a bank. I’ve noticed dificulty in the parking lot with even small bank angles. I can’t even imagine riding on a velodrome bank on a unicycle. Perhaps next year I’ll give it a try.
Actually, that seems to make more sense. I seem to lean/aim up the bank in order to keep a straight line- that might be why it felt like I was riding uphill all the time.
Anyhow, I really enjoyed flying up the banking and back down again- certainly something you have to try if you ever get the chance!
It was interesting reading all the background info about how velodromes work, but I think Cyberbellum was off the mark on why it was harder to ride on the bank.
You’re just going too slow.
If tracks are designed for a nominal 40 mph rider, and you’re going 25, The flat part will probably be the most efficient part for you to ride on. Riding on the bank, you have to keep adding effort to stay on it, as the cycle seems to want to head back downward. Only when you reach the speed the bank was designed for will your cycle tend to track “straight” on there.
Oh, and if you’re riding on the high part, watch out for those wet leaves!
Wish I could ride at that speed back in my biking days! I can’t think of anywhere except in a track sprint where you would hit that speed, and even then for short bursts. For that matter, sprinters seem to play a lot of low speed cat and mouse on the steep banking.
It was certainly more effort to ride the banking than on a bike, but it was by no means a struggle- the Coker seems to stick pretty well to the velodrome.
I was hoping to set an hour record mark for NZ Unicyclists. If I could keep up the 25km/h laps then I should at least achieve half the bicycle hour record (=half the wheels )
There was a race in 1967 where neither sprinter wanted the lead position going into the last lap. They still-standed for 22 minutes just staring each other down. Not sure who won, but that race caused a rule change.
On most 333.3 m tracks you can still-stand even in the turns, but the shorter tracks have steeper banks and the pedal clips if you go slow. Tire stickiness is not a factor. I think they coat the velodrome with some sort of urethane to help with traction.
John, your “wet leaves” comment sure brought back a bad memory for me. I did some track racing back in my college days. It was at East Point Velodrome, in the outskirts of Atlanta, GA.
Last lap of a 5000 meter race, I was leading (I really was leading the race:D) coming out of turn #4. This velodrome had a huge Tulip Popular tree that towered over the outside of turn four. Hundreds of blossoms had fell onto the track and slid to the edge of the apron.
Well, just as I was exiting turn four, in full out sprint, my front tire hit some tuplip bloom leaves, and the rest was history. The wreck collected 5 of us with me, of course, being on the ground first. I had massive track rash in my thigh and shin and a badly jammed wrist. I had way to much pride back then. After a minute or two of recover, I actually picked up my bike and drug it and me across the finish line. The spectators and other bikers gave me a standing ovation of approval, but now I realize it was just me being having PRIDEFUL STUPIDITY.
Even with this bad injury, track racing was incredibly awesome! Having said that, no part of me wants to ride my unicycle on those step banks, we just don’t carry the required speed for the steep banking. I would love to take a track bike for a few more lap, ah, the memories. --chirokid–
When i first read this i couldn’t believe it. Riding a unicycle on a track! but then when i saw that there are different grades of tracks i realized that maybe it was possible.
The only track i’ve ever seen was the one that was used for the salt lake olympics (1996?) it was dismantled, and shipped to Bromont, and re-assembled. Damn though, was this one steep track. the steepest part must have been over 60 degrees. I was no where near being able to make it up on my feet, and wouldn’t slide down it either (too damn steep). So i guess you can see my surprise when i saw this thread.
Anyways, i think i would like to try this out on a less steep track, maybe with darren’s super light-weight 700c unicycle, the one with the carbon wheel, and with some 90mm cranks. That sounds like alot of fun. Good luck to all pursuing the Velodrome with one wheel. You have my respect!
Sounds great fun. For the technical question, I’m with John Foss on this one, but with a bit of psychology thrown in.
Strikes me that if I went on a banked track, I would want to ride as high on the track as I could, whereas the track is actually designed to have one ‘level’ for each speed. At the ideal speed, the cycle will be perpendicular to the surface of the track - but who wants to stick to the low levels of the track on their first visit?
Now, if you try to go higher than your speed would dictate, you are basically trying to keep the unicycle up a hill. You are riding across the slope, and probably leaning ‘outwards’ relative to the track surface (although, of course, inwards relative to the track centre).
Riding across a slope is hard work on a unicycle - on a fat tyre, doubly so, because the contact patch is wide, and when you are at an angle to the surface, the rolling radius of your tyre varies across the width of the contact patch, causing the tyre to work against itself and squirm, Motorcyclists call it “white lining” because bikes do it on road markings sometimes.
This doesn’t change the fact that riding on a velodrome must be jolly good fun. I’m almost moved to use that sadly devalued expression, “awesome”.
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