Competition cycling...

system · August 25, 1995, 10:22am

Hi,

It is coming up to that time of year again, when people take out their running
shoes, service their bikes and plunge into the freezing winterish water (if the
water in Australia’s winter can be described that way:) to compete in the many
triathlons that frequent our sunny weekends.

Being an avid masochist myself, I sometimes take part in these fests of toil
and, along with a group of around 20 other keen drinkers with exercise problems,
we are going to take part in one of the major events during October - the Noosa
Triathlon.

Aside from subjecting myself to some hours of physical torment, I also commute
to uni on my uni - around 15km (just under 10 miles). I currently ride a 24"
SEM, but I am contemplating building a geared uni to speed things up a little.

After much deliberation on the matter, I am thinking of building a 20" wheel
with internal gears (seven speed) in the hub - I found a German manufacturer (*
Sachs??? *) which makes excellent quality internal gears for racing bikes. A
little over the top? Maybe…

Anyway, I would like to finish building this uni sometime in the next couple of
weeks and ride it in the triathlon! 40 km (25 miles). Has anyone tried this
before? I was wondering if there were any rules regarding the cycle leg and the
number of wheels etc. I know that they test the brakes of every bike that is
entered… Maybe I will have to get the geared hub with disk brakes

Cheers, jason

system · September 12, 1995, 7:14am

Re: Re: Competition cycling…

Mark Schecter wrote:
|> Jason Richards (jazz@cs.uq.oz.au) wrote:
|>
|> : After much deliberation on the matter, I am thinking of building a 20"
|> : wheel with internal gears (seven speed) in the hub - I found a German
|> : manufacturer (* Sachs??? *) which makes excellent quality internal gear

I’m late in responding to this discussion because I was away in the States, but
it seems to me that we already discussed this previously. There are many
questions that are repeated as if they have never been asked before, like about
kick-up mounts, which has been discussed in detail. Perhaps besides the FAQ we
need some kind of an index of topics. Even if a topic is not in the FAQ, the
index could point to a thread. So perhaps an index of threads?

Anyway, it’s a waste of everyone’s time to talk exactly about the same thing.
For beginners who keep asking about how to get started etc., getting a copy
of Jack Wiley’s book my Anyone Can Ride A Unicycle could no doubt help a
great deal.

Don’t misunderstand me – I am not against questions, even very basic ones. But
we should classify our materials better and make them easily accessible.

Oh, concerning geared unicycles. Some years ago there was a diagram of a
nonfreewheeling hub in an old issue of OOW. There were also discussions on the
topic. I suppose eventually OOW will be scanned and be made available
electronically.

Stay on top, Jack Halpern, IUF Vice President

system · August 25, 1995, 5:59pm

Re: Competition cycling…

Jason <jazz@cs.uq.oz.au> wrote:

>After much deliberation on the matter, I am thinking of building a 20" wheel
>with internal gears (seven speed) in the hub - I found a German manufacturer (*
>Sachs??? *) which makes excellent quality internal gears for racing bikes. A
>little over the top? Maybe…

Jason, best of luck building your geared up uni! However, my experience with
geared up giraffes, quite different from the geared up standard Jason is
planning to build, suggests that a big wheel standard may be a better option.

Part of the difficulty of riding a geared up giraffe is the crankset can move
forward and backward of the wheel. A geared up standard does not suffer from
this problem, since the center of the crankset and wheel are exactly in the
same position.

A geared up giraffe also suffers from inherent looseness of the drive chain. A
geared up standard will suffer from inherent looseness of the gears. As the
gears wear down, the problem gets worse, unless the gears can be tightened
somehow or replaced.

I certainly hope that Jason succeeds in making a viable geared up unicycle,
especially one practical enough for commercial manufacturing, so everyone
willing to pay can get a reliable one. The big wheel may still out perform it,
but how many people can get a 40" or larger big wheel into their car’s trunk?

Sincerely,

Ken Fuchs <kfuchs@winternet.com

system · August 26, 1995, 3:12am

Re: Competition cycling…

Jason Richards (jazz@cs.uq.oz.au) wrote:

: After much deliberation on the matter, I am thinking of building a 20" wheel
: with internal gears (seven speed) in the hub - I found a German manufacturer
: (* Sachs??? *) which makes excellent quality internal gears for racing bikes.
: A little over the top? Maybe…

: Anyway, I would like to finish building this uni sometime in the next couple
: of weeks and ride it in the triathlon! 40 km (25 miles). Has anyone tried
: this before?

I haven’t tried it but I’ve thought about it quite a bit. I think the biggest
problem you face is figuring out how to lock out freewheeling. This “feature” is
inherent in all types of bicycle transmissions. (One exception is a special
Sturmey-Archer 3-speed, made for track racing bikes quite a few years ago. If
you find one, I’ll buy it from you!)

Having taken apart a Sturmey-Archer 3-speed to learn how it works, I concluded
(though I could be wrong) that it would be far from trivial to prevent
freewheeling. If someone can figure out a way, a world of unicyclists would
wobble a path to your door.

I’ve seen a picture of a uni with a derailleur and some kind of mechanism to
lock out freewheeling. It’s in On One Wheel from sometime in the 80’s. I’ll try
to locate it.

One solution might be to use a motorcycle gearbox, say from a Honda trail
scooter, but never having seen one, I have no idea how big or heavy or
adaptable that would be. But at least it bypasses the freewheeling problem from
the git-go.

Another solution, invented by Tom Miller, is to use an axle within the axle. The
inner axle (I think) carries a sprocket, call it the right side. The sprocket
drives a chain which drives a third axle that passes through the frame above the
wheel. The left end of the upper axle carries a sprocket that drives a secondary
chain. The secondary (driven) chain connects to a sprocket on the left end of
the outer axle on the wheel. There is only one gear available at any time, but
it can be any ratio.

Another solution I’ve thought of but not tried, is to use two sprockets and a
belt or chain, in a setup like that used to control the speed of the chuck in a
drill press, or two bicycle freewheels. To wit:

     ___________ ______
       |__________| __|_____|_ ______|===============|_________|__ ___|
       |belt/chain |______________|

       Driving sprockets Driven sprockets.

You would still have to stop to change gears (at least I would!), but they would
be available a lot more easily than changing wheels or unis. There is no gear
changing mechanism involved, you just move one end of the belt/chain from a
larger sprocket to a smaller one, then move the other end to the corresponding
sprocket at the other end. The gear sizes are stepped such that the length of
the belt/chain is the same for all combinations. I should say that this is
probably practical only on a uni that already is built for chain drive, i.e. a
giraffe. You might need a simple tensioner to keep the belt/chain tight.

Something to think about, anyway. Good luck and keep us posted.

–

system · August 26, 1995, 3:07am

Re: Competition cycling…& gears

In a message dated 95-08-24 22:30:44 EDT, you write:

>After much deliberation on the matter, I am thinking of building a 20" wheel
>with internal gears (seven speed) in the hub - I found a German manufacturer (*
>Sachs??? *) which makes excellent quality internal gears for racing bikes. A
>little over the top? Maybe…
>
>Anyway, I would like to finish building this uni sometime in the next couple of
>weeks and ride it in the triathlon! 40 km (25 miles). Has anyone tried this
>before? I was wondering if there were any rules regarding the cycle leg and the
>number of wheels etc. I know that they test the brakes of every bike that is
>entered… Maybe I will have to get the geared hub with disk brakes

I’m not familiar with the hub you describe, but if it’s like an old Sturmey
Archer 3-speed hub, you will have to deal with the freewheeling. If you remove
the power of the hub to freewheel, I imagine it will be difficult for it to
change gears.

I do have experience with geared up unicycles. In 1980, I put a large sprocket
on my Schwinn 6’ unicycle, nearly doubling the gear ratio. The cycle went
faster, but was a great deal harder to mount, very difficult to ride at low
speed, and dangerous if and when one fell at speed. My conclusion: Giraffes
don’t need to go fast.

Tom Miller built a geared up 20" unicycle in 1982, using a complex chain system
and a hub-within-a-hub. It was not a giraffe. The cycle was geared up to
approximately a 40" wheel. There were three basic weak points in this design:

Hard to make, therefore expensive (Tom hasn’t made another one).
Because of the higher gearing, the rider has less ‘torque’ or power to
control the wheel. Reactions will be slower and more sluggish, so
acceleration and braking cannot happen as quickly as they do with a regular
hub. This will cause you problems in demonstrating braking power (don’t use
the hub with the built in brake – if you actually use it you will tend to
be flung to the ground!).
A small wheel is bad on bumps. A bump that a 24" wheel will pass relatively
easily may knock you off your 20". A small wheel at higher speeds seems
more sensitive to bumps.

For best results in racing or distance riding, try for a larger wheel. The main
disadvantages in this area are using unusual parts (if it’s real big), and
fitting it into ‘the boot.’ (that’s ‘trunk’ for you americans and circus
performers).

I have a 45" big wheel. It rolls right over most bumps, as long as you’re paying
attention, and it’s stable enough to ride mile after mile (even more
kilometers!) without a dismount. I just wish I had a pneumatic tire, instead of
the solid rubber I’m using!

You can get air tires in 26" and 28", and these will probably serve you best
because they will be simpler, cheaper, and much easier to ride. You may also
find, in the long run, that they are almost as fast.

John Foss, the Uni-Cyclone unicycle@aol.com

system · August 28, 1995, 9:36am

Re: Competition cycling…& gears

> I’m not familiar with the hub you describe, but if it’s like an old Sturmey
> Archer 3-speed hub, you will have to deal with the freewheeling. If you remove
> the power of the hub to freewheel, I imagine it will be difficult for it to
> change gears.

Yeah, the hub is based on the same concept as an old Sturmy Archer 3-speed, and
freewheeling is the BIG problem. The hub I am looking at claims to be able to
change gears while moving forward, or while stationary. If I understand
correctly, this means that freewheeling is not part of the gear changing
mechanism, and consequently, the gears should be able to be fixed.

I will be talking to a guy from Sachs later on today to see if this is indeed
possible. I will keep you posted.

> I do have experience with geared up unicycles. In 1980, I put a large sprocket
> on my Schwinn 6’ unicycle, nearly doubling the gear ratio. The cycle went
> faster, but was a great deal harder to mount, very difficult to ride at low
> speed, and dangerous if and when one fell at speed. My conclusion: Giraffes
> don’t need to go fast.

My plan is to build a giraffe - dictated by the hub’s chain drive - but only 5’
high. Considering that my current SEM stands at just over 4’ it shouldn’t be to
much of a hassle comming down. Having gears means that mounting and riding slow
should be no problem as long as you are in the right gear. I think that coming
of at high speeds on any uni will be dangerous

> For best results in racing or distance riding, try for a larger wheel. The
> main disadvantages in this area are using unusual parts (if it’s real big),
> and fitting it into ‘the boot.’ (that’s ‘trunk’ for you americans and circus
> performers).

If I use a 24" wheel, and an internal gearing structure within the hub, I should
be able to retain the flexibility of riding with a 24", i.e. accelerating,
fitting it into the boot etc, as well as experiencing the same performance as a
large 40" wheel for speed and distance…

Well, that is the plan anyway.

Cheers, jason