Sunday, March 18, 2012

What is a Throttle Lock

I have installed a throttle lock on the Vulcan, and I plan to install one on Mary Ann's Burgman too. They are simple devices that I have used before, and they have helped me with long distance trips.  The most important consideration about these things is about their safety, or lack thereof.  All motorcycle add-ons must be considered this way, not just throttle locks, but bungie cords, radios, gps systems, cell phones, water bottles, trailers, even chome doo-dads that you add just for show.

Before I consider the safety aspect of throttle locks, let me restate the basic principal that safety is a state of mind, not a device you can add to a bike.

The name "Throttle Lock" itself sounds dangerous, but they do not in fact "LOCK" the throttle, they simply increase the friction in the throttle to prevent it returning to idle when the hand leaves the throttle. The hand is still able to adjust speed, but the throttle feels a bit stiffer.

I want to review the historical types of throttle, starting with the one where you set the throttle with some  lever, that you do not actually keep holding.  When you want to change speed, you reach over and turn the lever up or down a bit, then resume holding whatever you were holding before (say a beer for example).  This type of throttle was used in boats, planes, model T Fords, railroad locomotives, and the same principle even applied to horse drawn stage coaches.  Wherever precise control of speed was not needed or even expected.

The next type of throttle came about when speedometers were invented and there was a need to control speed more precisely.  As more and more cars came on the roads, and speed limits were enforced, it got so that you had to monitor your speed constantly. Throttles were designed where you could keep part of your body on it at all times.  In the car, it was generally a foot pedal so as to not interfere with the usual smoking or drinking.  With a motorcycle, it was a handgrip, as your feet were sometimes occupied holding up the bike. A foot pedal must return by spring pressure alone because human feet cannot grip the pedal properly. But with the motorcycle throttle on a rotating hand grip, self return was not a physical necessity (because the hand rotates both ways) and many early grip throttles did not return to idle all by themselves. This was considered a benefit in some cases.

Then the concept of the "Deadman" throttle came about.  It was noticed that in the case of a heart attack or a driver falling off the bike, boat, or out of a car, that it would be safer for the throttle to return to idle or even shut off altogether.  Soon this became the universal standard for throttles of all self-propelled vehicles - and even for things like lawn mowers where taking your hand off the throttle sometimes meant that you were shortly going to stick it in the blades.

I have seen some motorcycles with a true deadman cut off - a wire attached to kill switch, so that if you leave your bike unexpectedly, the wire pulls out and kills the engine altogether.  Very useful if the bike lands on top of you drive wheel first.

And finally, we come full circle with automotive "cruise control" that varies the throttle to maintain a set speed until you step on the brake.

So now with the "throttle lock" I'm going back to the non-deadman throttle, but briefly and only when there is no traffic and a clear view.  The purpose of the throttle lock is not to maintain a set speed, just to prevent slowing down suddenly when the hand is removed from the throttle for a few seconds. Unlike cars, most motorcycle slow down very quickly if you remove your hand from the throttle, even if you try to get a new wrist position, or want to adjust the right hand mirror.

So what is the real danger of a throttle lock?  I can mention a few from personal experience.  One, the throttle lock gets loose, rotates, jams in an open position and simultaneously blocks the brake lever from being squeezed.  Segundo: You use the throttle lock to remove both hands from the handlebars, and you discover for the first time that your motorcycle has a "speed wobble" that happens only when both hands are off the handlebars.  If you are lucky, you can get your hands back on the bars before this becomes a "tank slapper".  Third comes a whole variety of unexpected little things like gusts of wind, deer jumping out of the bushes, etc. that require fast response and full time two-handed control.

Now let me address something that is not a problem with throttle locks.  If you put on the front brake, you should notice that your hand stays on the throttle, and for maximum force, your thumb must remain hooked around the throttle while squeezing the brake lever.  So it does not really matter whether the throttle is locked or not, you must always return the throttle to idle before squeezing the front brake lever hard.  For many people this is an unconscious action, but one that you really should be aware of.  Due to the way your hand grips the throttle and brake together, it is actually quite a difficult trick to get a good squeeze on the brake while simultaneously holding the throttle open, although I am also sure some people can do it. So in reality you do not have to worry about a well adjusted, properly installed, throttle lock preventing you from stopping, even if it is in the "locked" position at the time.

Picture: The illustration documents Mrs. F.S. Bliven driving a car, from a collection of pictures primarily to serve as an easy to access educational resource. Contact Image ID# 0400F226.  I do not know why I chose this picture, but I'm pretty sure she was using one of the types of throttles that I mentioned.

1 comment:

  1. Your discussion about 'cruise control' put me in mind of the warnings that were making the chain email rounds a couple of years ago.

    Essentially, the warning was not to engage cruise control on wet roads ... because: 'the policeman told her that if the cruise control is on and your car begins to hydroplane - when your tyres lose contact with the pavement, your car will accelerate to a higher rate of speed and you take off like an airplane.

    To my dismay, I discovered that this myth is still being posted on a number of sites (and, for all I know, still being passed around in chain emails).

    It is, of course, completely false that, if your tires lose traction, the cruise control will 'will accelerate to a higher rate of speed.' That suggests a complete misunderstanding of how cruise control works. Cruise control is, of course, based on wheel speed not vehicle speed.

    Curiously enough, Snopes rates this myth as True (albeit with some qualifications) while Hoax-Slayer sensibly rates it as Misleading and alarmist.