A video posted to Facebook under the title “The most fun you can have on three wheels” has been viewed nearly 3 million times – and once you watch it, we’re sure you’ll agree with the title.
Filmed at the fifth annual Cissal Hill Big Wheel Race in Larue County, Kentucky, the footage was taken on a GoPro camera by Blake Vittitow.
Last to first with Evan Douglas
Posted by Blake Vittitow on Monday, 30 November 2015
There’s no pedalling, with gravity doing the job of getting the riders downhill – which helps explain Vittitow managing to move through the field, since he had a weight advantage of another rider on his trike, Evan Douglas.
According to the Larue County Herald, it was one of two races that took place that day – this one was for rubber-wheeled trikes, the other for ones with plastic wheels.
The stability of the trikes is noticeable – there’s a few heavy bumps more reminiscent of fairground dodgem cars rather than a cycle race, but everyone seems to stay upright.
Big wheel trikes were a hugely popular toy in the United States in the 1970s, aimed at boys aged between eight and 10 years of age.
In 2000, Jon Brumit happened across a big wheel trike and decided to race it down San Francisco’s insanely steep Lombard Street, famous for its hairpin bends.
More riders joined him over the years until, as the Bring Your Own Big Wheel website puts it, “YouTube happened” after interest was sparked by a video posted there of the 2006 event.
Now, hundreds of competitors, many in fancy dress and on a huge variety of machines, take part each year and are cheered on by thousands of spectators.
Last year we reported on another madcap race format from the United States, the Marymoor Crawl.
Our story was picked up by the organisers of the Revolution Series, who introduced it into the track meet’s programme under the name the Longest Lap, since when it has become a huge favourite with spectators.
23 thoughts on “Video: Crazy three-wheel downhill racing from Kentucky – lots of fun!”
Box Hill on Boxing Day anyone
Box Hill on Boxing Day anyone?
So, what exactly is a “weight
So, what exactly is a “weight advantage” when falling solely due to gravity? I seem to remember that a chap named Galileo back in the 16th century demonstrated that gravity acts on all falling bodies independently of their mass. So why is it that so many people get this wrong? On an inclined plane (hill), factors affecting speed are friction and aerodynamics, but not weight! Please don’t persist with this erronious idea.
Oh, and it seems that they get going by pedalling and have brakes and/or feet on the ground, just might have something to do with differing speeds.
Apart from that, this looks like a hoot!
Deltavelo wrote:
You can get a weight advantage if the friction is significant in slowing the vehicles down but I’d be surprised if these trikes have high enough friction to make it worthwhile.
Deltavelo wrote:
Because the increased weight means wind resistance has less of an effect. Drop a sheet of paper, and a sheet of lead, the lead will hit the floor first unless there are some unusual factors at play. In a vacuum they’ll hit at the same time.
These people aren’t in a vacuum so I’m not sure what you’re stating is erronious.
danthomascyclist wrote:
They’re in Kentucky so a lot of people would disagree.
Deltavelo wrote:
As above, unfortunately it’s your idea that’s erroneous 🙂
Gravitational force is proportional to weight, but aerodynamic drag is independent of weight.
If you double the weight of the vehicle by welding one to the side of the other, so the two occupants are sitting side by side, the gravitational force will double and the aerodynamic drag will also (roughly) double, so you’ll gain no advantage: the acceleration will be broadly the same.
If you (nearly) double the weight by sitting one person behind the first, you’ll (nearly) double the gravitational foce but you’ll have only a modest effect on the aerodynamic drag. Result: a greater ratio of forcepulling the vehicle forwards on the slope to mass of the vehicle, ie greater acceleration, and a higher terminal velocity.
Definitely erroneous.
Definitely erroneous.
I’m beginning to see why it
I’m beginning to see why it is so often misunderstood, it is a bit counter-intuitive. If what you say were true Bez, then for example two steel balls of equal diameter but one solid and the other hollow would fall at different rates. This is not so, they fall at the same rate both in a vacuum and in the air. Gravity accelerates all bodies the same, independent of their size and here on this planet, it produces an acceleration of 9.81 m/s² at the surface. When not in a vacuum, air resistance slows the rate of acceleration to zero at which point it is at it’s terminal velocity. The other thing to be careful of is confusing weight and mass. Weight is a function of gravity, on earth something with a mass of 100kg would be said to weigh 100kg whereas on the moon it would weigh about 17kg but still have a mass of 100kg. (NB strictly, weight is a force so should be kgf, but for convenience we only say kg).
So the acceleration produced by the gravitational attraction between the earth and the object is a constant, it does not change by adding more to the object. Here is a thought experiment: imagine freewheeling down hill with a buddy and you link arms, do you suddenly start accelerating because you now weigh twice as much? I think not.
So my original point stands, aerodynamics, friction and pedalling/braking are the only factors, not the weight of the extra body.
It still looks a hoot!
Deltavelo wrote:
Nope, in air the solid ball will fall quicker, the only question is whether it is a noticable amount or a tiny fraction of a percent.
As a thought exercise, take it to the extreme. The hollow ball is made of steel so thin that it is as light as foil, the solid ball weighs as much as a bowling ball. The difference then should be obvious, and what becomes apparent then will remain true even if the hollow ball becomes heavier.
bikebot wrote:
If both balls weigh the same, think how large the hollow ball would need to be compared with the solid one and then ask yourself if it would still fall slower.
Beatnik69 wrote:
Of course it would fall slower it would weigh the same as the other ball, but would be the size of a house and so would have to displace a lot more air to move.
An easy test would be to get two balloons, inflate one and then drop both, the inflated one will fall slower, even though it weighs slightly more now (assume air inside the balloon is at a greater pressure than atmospheric pressure and that inflating also included some mositure content.) it definitley does not weigh less
Acceleration due to gravity is a function of mass, deceleration due to bearing and tyre friction is also a function of weight, but deceleration due to wind resistance is a function of surface area and shape and surface roughness, but unrelated to mass.
Beatnik69 wrote:
That isn’t what was proposed “two steel balls of equal diameter”. However, in your example, yes the larger hollow ball of equal mass would fall slower. If I remember correctly, the drag coefficient of a sphere simply increases as the square of the radius.
Deltavelo wrote:
No, they don’t. Let’s say your hollow ball has mass M and the solid ball has mass 2M. When you release them, the gravitational (downward) forces acting on them are gM and 2gM respectively. Obviously, dividing the foce by the mass gives acceleration, which is g in both cases.
Let’s brush over differential calculus for now and assume they accelerate at the same rate until they reach a certain velocity V. The downward forces on each remain the same, obviously: gM and 2GM respectively. But they both have a drag force which acts upwards and which is dependent only on their body profile and their velocity, not their mass. So both balls experience an upward force F.
Now your hollow ball has a net downward force of gM-F and your solid ball has a net downward force of 2gM-F.
To work out their acceleration, you need to divide force by mass in each case, giving you g-F/M for the hollow ball and g-F/2M for the solid ball.
Clearly, F/M > F/2M, therefore the solid ball accelerates more quickly for a velocity V. And notice that there is no constraint on V: the only time they both experience the same acceleration is the instant you release them. Once they are freefalling, the solid ball is always accelerating at a greater rate. (Until both have reached their terminal velocities, when the solid ball will be moving faster.)
Deltavelo wrote:
[Quote Deltavelo] Here is a thought experiment: imagine freewheeling down hill with a buddy and you link arms, do you suddenly start accelerating because you now weigh twice as much? I think not.
So my original point stands, aerodynamics, friction and pedalling/braking are the only factors, not the weight of the extra body.
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Your thought experiment is not relevant because neither your mass nor your air resistance changes. Put you and your friend on a tandem, (reduce air resistance compared to riding side by side) and I promise you you’ll go down the hill faster.
The error in your reasoning is explained here: http://physics.stackexchange.com/questions/75942/terminal-velocity-of-two-equally-shaped-sized-objects-with-different-weights
The relevance of this to cyclists is evident when you ride down a hill with a heavier rider. The heavier ride will be significantly faster down the hill than the lighter rider. I think this was also what started the discussion.
If you want a relevant thought experiment, that would be to have two parachutists at terminal velocity. One is weighs twice as much as the other. The heavier one descends faster.
It is really the same as the sheet of paper and the sheet of lead. Same shape, same aerodynamic drag, fall at very different speeds.
Terminal velocity on a bike is the speed you reach down a hill without pedalling or braking. It’s not that high on a moderate gradient.
Hold on a sec, is this road
Hold on a sec, is this road.cc or some physics forum?
Anyhow, although the gravitational acceleration is constant (I’m thinking of the two balls example), the force acting to accelerate is obviously different (F=MA) due to the different masses. So, if you have a relatively constant frictional/aerodynamic force acting on the two balls, but a different force (due to gravitational attraction) opposing that, then weight will make a difference which is why they will have different terminal velocities.
However, that difference will only be noticeable when the friction/aerodynamic forces are significantly big compared to the weights involved (e.g. think of a feather vs the same shape made from metal – the metal will fall noticeably faster). Of course, falling in a vaccuum (as per Gallileo) there won’t be any frictional forces and different masses will make no difference.
If you fancy doing an
If you fancy doing an experiment that’ll cost you a couple of quid*, get a block of Oasis flower arranging foam and cut it to the exact size and shape of a house brick. And then get a house brick. Go upstairs to your bedroom window and lob them both out, and see what happens.
* plus the cost of any third party injury claims if applicable
I stand corrected, better
I stand corrected, better stop riding in a vacuum! Thanks to all.
AAAARGH! I teach Physics.
AAAARGH! I teach Physics. The laws are simple to state and difficult to understand, hence the confusion shown in the above discusions, including some suspect maths!
Gravity creates weight, measured in Newtons; from mass, measured in Kilograms. The acceleration due to gravity is constant, in round figures 10 meters per second per second on the Earth. Easy practical check to do. Take two identical 500ml plastic bottles e.g Coke. Fill one with water the other leave empty. Hold them by the neck and drop them simultaneously, they land together, equally accelerated by Gravity even though their masses and therefore their weights are different. The air resistance that opposes movement is equal because the bottles are identical in shape, could put a little water in the empty one to ensure it stays upright. It works!
Check out Apollo 17 mission videos where a hammer and feather are dropped simultaneously on the moon, they land together. It is on You Tube.
To check this out for cyclists going down hill you will need two IDENTICAL cycles, with very different sized riders. The lighter rider should have less friction and go a little quicker. Difficult to control all the possible variables to get reproduceable results. It can be done with school lab stuff using ramps, trolleys and electronic data loggers that can measure speed and acceleration quite precisely.
ianrparsons wrote:
I weigh 20 stone. My 10 and 12 stone riding companions just cannot keep up, whatever bike, whatever clothing, whatever luggage, when we’re freewheeling downhill. They often can’t keep up pedalling flat out while I’m freewheeling. The heavier you are, the faster you go downhill. I can’t do the maths, but I know the effect is real.
If you do try it, do not do
If you do try it, do not do it out of a window! Any breeze will mess it up, as in the Oasis block experiment. The force of a breeze on the Oasis block will deflect it and spoil it. Still air is best. Keeps variables under control. BTW Yes I do have a Physics degree and more importantly over 20 years teaching the subject, but I only saw the two bottle demo last week! Much better than bags of fruit.
…and my point would be that
…and my point would be that at the top of the hill, the trike and rider have potential energy equal to E=mgh (combined mass x gravitational field strength x height of the hill) and this energy is converted to kinetic (movement energy) of the form E = half m vsquared (sorry I’m too lazy to find half and squared) All of the potential energy gets converted to kinetic energy (less frictional losses) therefore mgh=half mvsquared. Rearranging for v gives us v= square root 2gh. i.e. the final speed (elocity is independent of mass because it cancels out.
That said, I’m a Clydesdale and I go faster downhill cycling and skiing because my arms are strong and I’ve got a brain of jelly.
KnowThyInnerTube wrote:
The trick is with the frictional losses which you haven’t included in the equation. On a bike, the main frictional losses are rolling resistance and air resistance. Both of those aren’t related to mass and would be approximately equal at the same speed for light and heavy riders (the heavy ones might be a bit less aerodynamic) and would appear as a constant:
mgh – friction = ½mv².
thus,
v = √2(gh – friction/m)
and you’d get a weight advantage going downhill (not so much uphill). It’s a more noticeable effect on an incline as your terminal velocity is a lot less than freefalling – that’s why the bottle experiment would require very accurate equipment to spot the difference.
I’m not a physics teacher, so here’s NASA’s explanation of terminal velocity:
https://www.grc.nasa.gov/www/k-12/airplane/termv.html
and in red, it states “Objects do not fall at the same rate through the atmosphere”
Regardless of the physics I
Regardless of the physics I can give you some real world examples.
I was riding my tandem (complete with Stoker) along with a single rider when we came to a long downhill section. The poor single rider just watched us freewheel away at speeds they couldn’t match pedalling. And before you ask the tandem is much less aero than their bike. Big tyres, disc brakes, large pilot, etc.
And I know that if I freewheel my road bike down some of our local hills I never reach the speeds the tandem is capable of freewheeling to down the same slope in similar conditions.
The tandem has more weight and only about 1.5 times the air resistance. Hence the greater speed.