Unicycle approach to MTBking?

I went for a couple of hard rides on my bike this weekend- having not been on it for months. After riding my YUni 29’er with 150mm cranks it was like going from a lightweight race-car to a tractor!

Of course I went faster on the bike but it felt very inefficient. I think on a unicycle close to 99.9% of your energy is transferred to the wheel whereas on a bike you have each link of the chain working against you, chain-slack, chainstay flex, suspension sag, twice the weight etc. etc.

I was thinking of perhaps setting up my bike more like my unicycle- ditching a few gears- not quite single speed but maybe three speed up front? Also to maximise pedalling efficiency by using 150mm cranks, and setting it up fully rigid. And ditching the SIDs in place of fat 2.6’ tyres. Maybe shortening my stem further and using riser bars.

So my question is: has anyone come across 150mm MTB cranks? Are they available or do I need to cut down some regular cranks? What are they like on a geared MTB? I think because most MTB cranks don’t come any shorter than 170mm I’ve always put up with it. But at 1.65m 5’5 I think I could get more efficiency with shorter cranks :slight_smile:

Thanks,

Ken

On the flat, a properly set up bicycle is THE most efficient way of converting muscular energy into movement. A bicyclist is more efficient than a swimming dolphin or a running cheetah.

Put the bicycle on bumps and hills and some of this efficiency is lost.

In some circumstances, the weight works against you.

Loss of energy through flexing of the frame etc. should be minimal.

The unicyclist uses energy maintaining balance.

I’m pretty sure that the bicycle is more efficient in almost all circumstances. The clue is in your reference to being sure that the bike is faster.

However, let’s face it, the uni is much much much more fun.

I agree with the move towards simplicity on a bicycle, though. One or two good low gears, simple brakes, no suspension, and a robust low maintenance bike which relies on the skill and stamina of the rider…

In my bicycling days, I assembled a custom tourer with 12 gears, very good spec. for its day. In the end, I stripped and rebuilt it as a six speed and preferred it.

Gizmo,

If you want a single chain ring and 140mm cranks, you could get http://www.bikepartsusa.com/product_info.phtml?p=01-98285. I bought a pair and labouriously hacksawed and filed off the spider to turn them into uni cranks. How ironic if another unicyclist bought them and used them as bike cranks! They are actually Doteks, not Bulletprood BMX as implied on the site.

Tony

I’m sure that the study you imply did not examine unicycling. I would bet a lot of … (whatever I have a lot of; mostly hot air) that a good unicyclist is more efficient than a good bicyclist on the flat. For the same reason that Tony cited: there is a lot of energy loss in the bicycle’s drive train. A good unicyclist on the flat uses very little energy to balance. On uphills, I’d say the same. On downhills, of course, the unicyclist can’t win because he can’t coast without using friction to balance.

Unless it’s a REAL good unicyclist. :slight_smile:

We still have aerodynamics working against us.

Morten

True, but Mikefule didn’t mention speed. Since drag increases as the square of the speed, there is probably a cross-over speed where bicycling with a position that is better aerodynamically becomes more efficient than unicycling. If the unicyclist could achieve the same aerodynamic characteristics, the unicyclist would (IMHO) continue to be more efficient.

Re: Unicycle approach to MTBking?

U-Turn wrote:
> Mikefule wrote:
>> *On the flat, a properly set up bicycle is THE most efficient way of
>> converting muscular energy into movement. A bicyclist is more
>> efficient than a swimming dolphin or a running cheetah.

How come cyclists are so much slower, then, than dolphins or cheetahs?

>> The unicyclist uses energy maintaining balance.

Sure, I use a lot. This amount decreases as skill increases, though.

> I’m sure that the study you imply did not examine unicycling. I would
> bet a lot of … (whatever I have a lot of; mostly hot air) that a
> good unicyclist is more efficient than a good bicyclist on the flat.
> For the same reason that Tony cited: there is a lot of energy loss in
> the bicycle’s drive train. A good unicyclist on the flat uses very
> little energy to balance. On uphills, I’d say the same. On
> downhills, of course, the unicyclist can’t win because he can’t coast
> without using friction to balance.

No gears. If your crank/wheel ratio is perfect for speed on the flat, it’s
way too hard for speed uphill.

And of course, THE unicyclist can coast without using friction to balance,
he’s done it in front of witnesses and cameras. The reason we can’t do it
is that, compared to him (I’m thinking here of Sem Abrahams) we suck.


“Quemadmodum gladius neminem occidit, occidentis telum est.”
– Seneca

Re: Unicycle approach to MTBking?

Borges wrote:
>> A good unicyclist on the flat uses very little energy to balance. On
>> uphills, I’d say the same. On downhills, of course, the unicyclist
>> can’t win because he can’t coast without using friction to balance.
>
>
> Unless it’s a REAL good unicyclist. :slight_smile:
>
> We still have aerodynamics working against us.

Once again, a REAL good unicyclist doesn’t have to sit up straight.
>
> Morten


“Quemadmodum gladius neminem occidit, occidentis telum est.”
– Seneca

Re: Unicycle approach to MTBking?

> Weep in the dojo… laugh in the battlefield.

That really irks the enemy. An evil laugh is bad enough, but an amused
giggle really disheartens them. :wink:


“Quemadmodum gladius neminem occidit, occidentis telum est.”
– Seneca

I don’t usually get into these physics discussions because I’m not that smart, but I think this one is pretty obvious. Of course the (multi-geared) bicycle is more effecient. With the same amount of work output by the rider, the bicycle goes around 2 or 3 times faster than the unicycle. If the bicycle is wasting energy (chain slack, frame flex, etc), that just means that it uses the remaining energy even more efficiently.

It seems to me there is probably a reason why almost all bikes(that I’v seen) have 170’s or there abouts. I think most need the extra leverage to push the higher gears they run. exceptions: flatland bikes, as short as 135 I’v seen. Mod Trials bikes: really low gears, but still about 160’s. little kids bikes, they still have lower gears though.

Actually, the reason most bikes have 170 mm cranks is because most people “do it the way my forebears(PC) did it, it’s good enough for me.” Moreover, they assume, as you have, that everybody else has a good reason for the way they do something, (everybody is smarter than me :thinking: ) which perpetuates the situation.

An opposing view can to the standard 170-mm crank and a formula for a (hopefully) correct one can be found at:

http://www.nettally.com/palmk/Crankset.html

oh, well I guess I dont ride bikes enough to care about crank size a whole heck of a lot…

Re: Unicycle approach to MTBking?

In article <U-Turn.mjqxb@timelimit.unicyclist.com>,
U-Turn <U-Turn.mjqxb@timelimit.unicyclist.com> wrote:
)
)I’m sure that the study you imply did not examine unicycling. I would
)bet a lot of … (whatever I have a lot of; mostly hot air) that a
)good unicyclist is more efficient than a good bicyclist on the flat. For
)the same reason that Tony cited: there is a lot of energy loss in the
)bicycle’s drive train. A good unicyclist on the flat uses very little
)energy to balance. On uphills, I’d say the same. On downhills, of
)course, the unicyclist can’t win because he can’t coast without using
)friction to balance.

There is no way a unicyclist on the flat can compare with a bicyclist in
terms of efficiency. First of all, the gearing is all wrong; a 36-inch
gear, or even a 43-inch blue shifted gear, is way too low for riding
efficiently on the flats. Your aerodynamics are terrible (even if you lean
over), and the wobble of the wheel is a force that must constantly be
overcome. A well-lubricated bike drive train is over 90% efficient, and
the bike is much more efficient than the unicycle at using its current
momentum to keep going in the direction you want to go.
-Tom

Ah, but crank size would have an effect on Unicycles as well. It should be a function of your leg length to give maximum efficiency, as in you’ll be less exhausted after a ride.:smiley:

Re: Unicycle approach to MTBking?

In article <vao0gkco6491a7@corp.supernews.com>,
Scott Kurland <skurland@juggler.net> wrote:
)U-Turn wrote:
)> Mikefule wrote:
)>> *On the flat, a properly set up bicycle is THE most efficient way of
)>> converting muscular energy into movement. A bicyclist is more
)>> efficient than a swimming dolphin or a running cheetah.
)
)How come cyclists are so much slower, then, than dolphins or cheetahs?

Because they’re putting in far less energy than dolphins or cheetas do
when they have a burst of speed. A fit bicyclist can ride at a good
fraction of his top speed for 8 hours or more; a cheetah uses so much
energy that it can only run quickly for short bursts.

)And of course, THE unicyclist can coast without using friction to balance,
)he’s done it in front of witnesses and cameras. The reason we can’t do it
)is that, compared to him (I’m thinking here of Sem Abrahams) we suck.

I am sure that Sem spends a lot of energy while coasting–far more than
a bicyclist does.
-Tom

Re: Unicycle approach to MTBking?

Tom Holub wrote:
> In article <vao0gkco6491a7@corp.supernews.com>,
> Scott Kurland <skurland@juggler.net> wrote:
> )U-Turn wrote:
> )> Mikefule wrote:
> )>> *On the flat, a properly set up bicycle is THE most efficient way
> of )>> converting muscular energy into movement. A bicyclist is more
> )>> efficient than a swimming dolphin or a running cheetah.
> )
> )How come cyclists are so much slower, then, than dolphins or
> cheetahs?
>
> Because they’re putting in far less energy than dolphins or cheetas do
> when they have a burst of speed. A fit bicyclist can ride at a good
> fraction of his top speed for 8 hours or more; a cheetah uses so much
> energy that it can only run quickly for short bursts.

That doesn’t address the question: why is the cyclist’s top speed so much
slower than the cheetah’s or dolphin’s if he’s so efficient? For that
matter, I doubt a cyclist could beat a dolphin over 8 hours, either.
>
> )And of course, THE unicyclist can coast without using friction to
> balance, )he’s done it in front of witnesses and cameras. The reason
> we can’t do it )is that, compared to him (I’m thinking here of Sem
> Abrahams) we suck.
>
> I am sure that Sem spends a lot of energy while coasting–far more
> than a bicyclist does.

Doing what?

> -Tom


“Quemadmodum gladius neminem occidit, occidentis telum est.”
– Seneca

Re: Unicycle approach to MTBking?

In article <vap6uoqf0dn742@corp.supernews.com>,
Scott Kurland <skurland@juggler.net> wrote:
)Tom Holub wrote:
)> In article <vao0gkco6491a7@corp.supernews.com>,
)> Scott Kurland <skurland@juggler.net> wrote:
)> )U-Turn wrote:
)> )> Mikefule wrote:
)> )>> *On the flat, a properly set up bicycle is THE most efficient way
)> of )>> converting muscular energy into movement. A bicyclist is more
)> )>> efficient than a swimming dolphin or a running cheetah.
)> )
)> )How come cyclists are so much slower, then, than dolphins or
)> cheetahs?
)>
)> Because they’re putting in far less energy than dolphins or cheetas do
)> when they have a burst of speed. A fit bicyclist can ride at a good
)> fraction of his top speed for 8 hours or more; a cheetah uses so much
)> energy that it can only run quickly for short bursts.
)
)That doesn’t address the question: why is the cyclist’s top speed so much
)slower than the cheetah’s or dolphin’s if he’s so efficient?

It does address the question. The cyclist’s top speed is slower because
he is putting in less energy. Surely you don’t believe an 18-wheeler is
more efficient than a bicycle because the 18-wheeler goes faster.

)> )And of course, THE unicyclist can coast without using friction to
)> balance, )he’s done it in front of witnesses and cameras. The reason
)> we can’t do it )is that, compared to him (I’m thinking here of Sem
)> Abrahams) we suck.
)>
)> I am sure that Sem spends a lot of energy while coasting–far more
)> than a bicyclist does.
)
)Doing what?

Adjusting the position of the unicycle frame to maintain balance. A
highly talented unicyclist will require less energy to do this, but
it’s absolutely a requirement for any kind of coasting, while a
bicyclist uses negligible energy to coast.
-Tom

Well I suppose it depends on your definition of efficiency. I wasn’t thinking of miles per hour per joule of input, but minimum expenditure of energy to go a given distance at a unicycle-friendly fixed speed over a given course. They are both equally valid things to measure.

Re: Re: Unicycle approach to MTBking?

Your statements, Tom, are of the form “No, it’s not!”. I haven’t heard anything that would speak to a unicycle being less efficient. A bicycle may have a nicely lubed chain, but a unicycle doesn’t have one to lube. The aerodynamics are worse on a unicycle, but at low speeds is probably not a factor. The wobble of the wheel, like non-circular pedaling on a bicycle, is a matter of less-skilled unicycling, not a “force to overcome.” In what way does a bicycle “use its momentum”? Finally, what does gearing have to do with efficiency? We have to define terms better.

I’m mostly talking myself about minimum wasted energy to accomplish something uni-friendly. Spinning at 60 mph down a winding mountain road is not uni-friendly, so I’m not talking about that. For doing a job in which the task is in the bike-uni overlap, I think the uni would waste less energy. Not faster, not less stressful, not prettier, just less wasteful.