Toronto throtttle counterforce spring; throttle ergonomics

[Ben Barkow <dr.ben@xxxxxxxxx>]

You want a throttle control that you can point where you want it and keep it
there with ease. Therefore, you don't want to overcome any more force or
friction than necessary, particularly on day-long rides. But for safety, the
butterflies and slides in carbs and throttle bodies must have under any
foreseeble condition of manifold vacuum and cable resistance sufficient
spring force to return the bike to idle.

The solution is to have a spring at the throttle control grip that pulls
back. That leaves the throttle spring untouched yet still meeting the safety
criterion for close-down. You want to neutralizes the force you need to
operate the control. The profoundly simple design described here, which I
have modestly called the "Toronto Spring," applies to most bikes and works
like a charm. For many bikes, it costs only a dollar, can be installed in
two minutes, the only tool needed is a scissors or sharp teeth, makes no
mark on the stock bike, can be removed instantly, and requires no on-road
testing for the initial intallation. But if you install it in the winter
when you can't go out and try it, it will only make your cabin fever flare
up worse.

To begin with, you need to have or to improvise something stable sticking
out of your throttle bar end. A bar-end weight, common on Oilheads, is ideal
or maybe a large cork or something made from an internally expanding fitting
on a bar-end mirror. You get the idea?

First, have a peek at the three pictures.

http://home.ica.net/~barkow/bikestuff/Toronto%20Spring%20for%20wrist%20ease/


Here's how in words: take a light spring, saybe 1/4 inch by 2 inches and tie
a light cord to each end (about a foot or 30.487231 cm long). Wrap one cord
around the rubber grip and secure with a turn of tape. Pull on the spring
till it is fighting the throttle spring to the degree you like (ANY small
amount of counterforce is beneficial, eh?). Wrap the other end around the
bar-end weight and secure with a piece of tape. Re-adjust to taste. (You
might want to wrap the bar end weight with tape first if you are concerned
about wear marks under the spring.)

Hint: if the throttle now seems twice as heavy, you may have done something
wrong.

I've been working on and riding with counterforce springs for five years.
Previously, I settled on a pre-loaded heavy spring stuffed inside the bars
in torsion mode. While that design has the advantage of being invisible,
this design works far better in functional respects and is a few hours
easier to fabricate and tune.

In addition to helping with fatigue and carpel-tunnel syndrome, you get far
better precision, control, and speed in handling the throttle. That lousy
feeling when the throttle closes too fast is gone too. Besides
taking up cable play, you'll be quite surprised at how great the throttle
feels as a control device... makes the bike much more drivable and faster
too. That's because, when you think about it, it is plain dumb to have any
controls which demand human force. Controls should just require mental
judgment, slight sensory acuity, and slight manual dexterity. But not force
and certainly not unremitting force all day long just to hold the setting
steady.

With the Toronto Spring set for neutral, you can take your hand off the
throttle to clean your ear (or ears, if you are flexible) and wave at bikers
with two hands. You may discover, for the first time, that your bike does
not track straight, a topic for another day.

How much spring counterforce? First it should be reconized that as the
throttle is advanced the butterfly spring gets tighter; at the same time,
the counterforce spring unwinds and gets lighter. That's something of a
safety benefit. Design-wise, you want enough pre-load and pre-stretch on the
spring so that force at the start and at the finish of throttle movement are
in the desired range. For most bikes, total throttle movement is about a
quarter turn or so. Therefore if the pre-load is, say, half a turn, you are
likely to be in the proper range at start and finish.


Given a bit of friction in the system, the counterforce spring can be set to
simply hold the throttle steady at any setting or, with enough friction, to
hold it steady at all settings, as with the /2. That is comfortable for
touring but some may reasonably feel it is unsafe to have a throttle that
remains open when there's no human or biker hand on it. In the trade, we
call this a "dead man's switch" although there's good reason to believe it
applies in principle to dead female bikers as well. But even the stock
situation merely returns the bike to idle and has no provision to kill the
ignition in the event of a mishap, outside of racing.

In light of this discussion, it should be clear that high-friction gizmos
like the ThrottleMeister sold to ease long-distance wrist effort make no
sense. They get in the way of good and easy setting and just cause you to
fight needless friction all the time. They make terrible cruise controls and
lead to lazy driving habits - control of a bike should always be active...
but not tiring.

Improvements to ergo-geometry make sense. My favourite easy fix is to wrap
bicyclce handlebar tape around the stock grips to enlarge the grip diameter,
offer a barrel shape to the palm, addresses impingements of temperature and
vibration, and in general, to provide a humanly-right feel, as least to my
hands. This tape is made of cork, elliptical in cross-section, and it is
easy to make two windings out-and-back that can be secured with a turn of
tape. In the winter, unwrap, lay a grip heater membrane over the grips, and
re-wrap. For additiona heat, some riders may wish to plug-in the heater to a
source of electricity.

In the same vein, plastic clip-on levers (ThrottleRocker} which you push
with your upper palm can be helpful sometimes if the fit is right. But it
fits right only at one point of throttle rotation.

Likewise, it makes sense for the serious biker to persevere in achieving an
ergonomically suitable adjustment of the bars and riding position regardless
of what seemingly unadjustable if fashionable crap may have been supplied by
the manufacturer, even if fraudulently labelled "Ergonomic" in the sales
literature. With care, you can always make the fit better. Think "horse" or
"bicycle" not "Easy Rider" or "Ape Hanger" and certainly not "Hog."

You are welcome to post this note to other Internet sites.

The first notion I got of a counterforce spring was from Bob Fleischer,
"Snowbum."

Ben
Toronto

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