56 inch big wheel with 4.5 inch cranks!?

I took my 56" big wheel with solid 7/8" grey wheelchair tire out for a
few rides (each about an hour long) this past Labor Day [1 Sept.]
weekend.

Gearing: Based on Mikefule’s wheel radius / crank length ratio, the
ratio of a 56" diameter wheel to 4.5" cranks is 28/4.5 = 6.22222…

This thing goes fast on the level and even faster down hills, but it
accelerates slowly and is a bit of a problem going uphill. Need a good
handle for the Schwinn seat on this beast; that may solve the minor
acceleration and uphill riding issues. A major problem is the down
hills can get this cycle going in excess of 30 mph; not fun when neither
maintaining speed nor slowing down is an option. Clearly the handle
would help with this problem, but the cycle clearly needs brakes as
well!

The cycle isn’t that easy to mount either. You have to roll it forward
about 5 mph, jump up on the pedals, and overcome the angular momentum
of the wheel to correct the balance once up, but not quite in control.
I broke one of the spokes coming down from a failed mount attempt and
built a new spoke and replaced the broken one the following day.

Should I put even shorter cranks on this cycle? I’d guess that 3 to 3.5
inch cranks would require nearly the full weight of the rider to
approach 20 mph on a level course. Since the cycle was built to be a
speedster, I’d say that the 4.5 inch cranks are the perfect length.
Any longer crank would be a waste of wheel diameter, in my opinion.

I laced the wheel of this cycle in October 1980 while watching, on TV,
Steve McPeak’s attempt at setting a new altitude record (101 feet 9
inches = 31.01 m) on one wheel for 114.6m in a circle.

Sincerely,

Ken Fuchs <kfuchs@winternet.com>

Since no one else repied, I will. I would like to get a Coker or something that I could go fast on sometime. Bikes are nice once in a while, but sometimes you need that one-wheeled speed. I’m saving for a new comp to replace my Pentium Pro 233, so a Coker isn’t too near… Keep up the good work! I don’t think I could build a replacement spoke for MY unicycle.

Re: 56 inch big wheel with 4.5 inch cranks!?

Ken,

I remember talking with JF at UNICON 2002 after the 10K race. John raced on his 43" wheel with the wheelchair tire. When I asked him about the ride, he told me that it’s quite the beater-upper. Without the pneumatic tire, there’s not much there to absorb shocks. Do you feel the bumps more at high speed? Must be quite a bronco ride.

Bruce

…oops, I was logged in as Brad after his post in Just Conversation.

We just put brakes on David Bagley’s 43"er. Check out a couple of pics at David’s website:

http://www.tux.org/~bagleyd/unicycling/bigwheel/index.html

We’re still fine-tuning them, but so far so good.

Re: 56 inch big wheel with 4.5 inch cranks!?

Crank to wheel radius ratio is how I normally do it.

e.g.
5 inch cranks on a 20 inch wheel
10 inch radius
5:10
5/10 = 0.5
0.5 = 50%
Which means the length of the cranks is 50% of the wheel radius.

So on your amazing machine of which I am most jealous:
4.5" cranks, 56 inch wheel
Radius = 28 inches
4.5:28
4.5/28 = 0.16
So the length of your cranks is approximately 1/6 the raius of the wheel. Your ratio is 16%.

That makes the machine about twice as high in gearing as the standard Coker (1:3).

The comparison would be 57mm cranks on a 28, or 40 mm cranks on a 20.

Sounds like an amazing machine. I once rode a penny farthing with a similar wheel diameter, and it was truly memorable.

Re: 56 inch big wheel with 4.5 inch cranks!?

Wow Ken what a machine! Now I can fully appreciate your point made in another thread about crank length influencing seat comfort - it isn’t hypothetical at all!

Klaas Bil

Re: Re: 56 inch big wheel with 4.5 inch cranks!?

You just hit 'em harder. One of the drawbacks of the hard tire is when you hit an unexpected or sharp bump that literally pops you off the seat. I’ve had it happen where there’s a little 3/4" diameter round rock in the middle of the bike path. It’s the only thing there but the unicycle manages to center itself right over it. If you’re not paying attention, and you hit it with your pedals vertical, your bottom foot can be jolted off the pedal and you can do an ugly dismount at speed. An air tire smooths out these sorts of things.

But the hard rubber tire handles a lot better than the Coker. It’s much easier to turn on, making my old big wheel much preferred for parades or the rare performance in which it might be included. You can do great spins on it, and swooping turns.

Ken’s speed on an hour ride on his 56" are probably similar to, or slower than the speed I would do in a 10k race. Somewhere between 12-16 mph? That’s a guess.

I’ve ridden that 56" wheel before, but it was a long time ago. I think the cranks were longer too. The original setup was at the limit of Ken’s leg length, probably with the standard 5.5" (cottered) Schwinn cranks of that era. I can’t imagine riding it with 4.5 inchers. My first ride on it, in Ames Iowa way back in '82, included a long, scary hill I had to go down!

Re: 56 inch big wheel with 4.5 inch cranks!?

unisteve <unisteve.t7i09@timelimit.unicyclist.com> wrote:

>Since no one else replied, I will. I would like to get a Coker or
>something that I could go fast on sometime. Bikes are nice once in a
>while, but sometimes you need that one-wheeled speed. I’m saving for a
>new comp to replace my Pentium Pro 233, so a Coker isn’t too near…
>Keep up the good work! I don’t think I could build a replacement spoke
>for MY unicycle.

Thanks for the reply!

Of course, if one wants speed I would recommend a Coker if you don’t
have one yet. Nothing can beat that air tire ride. (My 56 inch big
wheel has a 7/8" soft grey wheelchair rubber tire; its actually very
hard, but not as hard as the hard black? wheelchair rubber tire. Hard
[and so called soft] wheelchair rubber allows one to feel every bump and
stone on the road.)

If one already has a Coker, get a Deluxe Coker with the Airfoil rim,
brakes and air seat. If one already has a Deluxe Coker, get a 50 inch
or larger big wheel or add a Harper 2-speed hub to your Coker.

Unisteve, happy riding to you! Used 500MHz computers and a little
faster can be found for around $100 now, so you could start saving up
for a Coker sooner. (There really isn’t anything a 1-3 GHz computer can
do that a 500+ MHz can’t do; the 500+ MHz is plenty fast enough.)

Sincerely,

Ken Fuchs <kfuchs@winternet.com>

Re: 56 inch big wheel with 4.5 inch cranks!?

>Ken Fuchs wrote:
>> *I took my 56" big wheel with solid 7/8" grey wheelchair tire out for
>> a few rides *

Bruce AKA brad (brad.t7mem@timelimit.unicyclist.com) wrote:

>I remember talking with JF at UNICON 2002 after the 10K race. John
>raced on his 43" wheel with the wheelchair tire.

Trivial correction: John Foss has 46" wheel. I don’t think he has a

>When I asked him about the ride, he told me that it’s quite the
>beater-upper. Without the pneumatic tire, there’s not much there to
>absorb shocks.

Even though I use the soft solid wheelchair rubber as opposed to the
hard solid wheelchair rubber, all solid wheelchair rubber is very hard
indeed! However, the soft solid wheelchair rubber will compress on
impact perhaps 1/8 - 1/4 inch, providing a small measure of comfort from
shocks or bumps. Also, note the relative size of the wheel to a bump.
For example, a one inch bump is fairly trivial on a 56" wheel with its
huge angular moment, but it could easily cause an UPD on 16" or 20"
wheel.

>Do you feel the bumps more at high speed? Must be quite a bronco ride.

You do feel (as in notice) the bumps, but I ride the 56" big wheel on
paved roads only, so I only notice the pot holes, bad patches and uneven
concrete slabs. They really aren’t that much of a shock, but I may have
gotten used to a solid rubber ride via many years of experiencing it.

You don’t feel the bigger bumps so much as hear the twang of the shock
hitting the wheel with a slight reverberation!

Yes, the 56" wheel twangs louder at higher speed when hitting a large
bump, but I personally don’t consider it a bronco ride. I probably feel
it in the legs, but the 56" wheel’s unmodified Schwinn seat is very
comfy!

I’ve gone down 6 inch curbs with my 40" big wheel without ill effect,
but I wouldn’t do that with my 56" big wheel, because I don’t want to
risk rim damage. (40" rims are a lot easier to get than 56" rims.) I
wouldn’t want to try riding up (as opposed to jumping up) a curb with
any solid rubber big wheel, because the rubber may not provide the rim
enough cushion to avoid damage.

Hey Bruce! Nice to hear from you.

Sincerely,

Ken Fuchs <kfuchs@winternet.com>

Re: 56 inch big wheel with 4.5 inch cranks!?

>Ken Fuchs wrote:
>> *-
>> Gearing: Based on Mikefule’s wheel radius / crank length ratio, the
>> ratio of a 56" diameter wheel to 4.5" cranks is 28/4.5 = 6.22222…,
>> *

Mikefule <Mikefule.t7yg2@timelimit.unicyclist.com> wrote:

>Crank to wheel radius ratio is how I normally do it.

>e.g.
>5 inch cranks on a 20 inch wheel
>10 inch radius
>5:10
>5/10 = 0.5
>0.5 = 50%
>Which means the length of the cranks is 50% of the wheel radius.

>So on your amazing machine of which I am most jealous:
>4.5" cranks, 56 inch wheel
>Radius = 28 inches
>4.5:28
>4.5/28 = 0.16
>So the length of your cranks is approximately 1/6 the radius of the
>wheel. Your ratio is 16%.

Thank you very much for the correction.

>That makes the machine about twice as high in gearing as the standard
>Coker (1:3).

>The comparison would be 57mm cranks on a 28, or 40 mm cranks on a 20.

>Sounds like an amazing machine. I once rode a penny farthing with a
>similar wheel diameter, and it was truly memorable.

Thanks for your kind comments, Mikefule.

Sincerely,

Ken Fuchs <kfuchs@winternet.com>