From: stxtnt@rs733.GSFC.NASA.Gov (Nigel Tzeng)
Subject: Re: ROLLER-BRAKE Survey Results & Continued...
Organization: Goddard Space Flight Center, Greenbelt, Md, USA
Distribution: rec
Date: Tue, 22 Dec 1992 15:29:34 GMT

In article <BzMnBE.1vy@csn.org> pae@teal.csn.org (Phil Earnhardt) writes:

>>Put simply, same stopping geometry as pads(rear pad) but with ABS - anti-lock
>>braking.

>Now, this is an interesting analogy! Did you know that ABS is *not* the
>most efficient means of stopping a car? Threshold braking -- applying braking
>force to the threshold of the surface's limit of traction -- is the most
>efficient means of stopping. On all surfaces.

>It does take great skill to perform threshold braking. Instructors at the Ford
>Ice Driving School in Steamboat Springs, CO, can do it, but they don't teach
>it in their intro courses. I'd guess after a couple of weeks' worth of driving
>on their ice'n'snow track that you could begin to learn how to do it.

>One other comment about ABS: I'd be happier of *everybody* took a half-day ice
>driving course than if *everybody* had ABS. We'd be better off if everyone
>knew the limits of their vehicles and drove accordingly -- if they drove in
>such a way that they didn't *need* to use the stopping power of an ABS. After
>all, it doesn't do you a whole heck of a lot of good if *you* can stop but the
>driver behind you can't. ABS won't help if you're not alert.

Maybe the example isn't that bad you know.  It should be easy to teach
anyone with ABS how to threshold brake on a vehicle equipped with ABS.
You apply brakes hard enough to activate the ABS system and then ease
off until it stops pulsing.  At that point you should be applying the
maximum braking force without locking wheels...ie threshold braking.

I do however agree with the last paragraph :).

>>Having ridden the prototypes myself, it really is similar to stopping with
>>ABS in a car to skidding in one without. Control is maintained since the
>>braking "wheel" does not skid. 

>...which implies that control is *not* maintained when using traditional
>brakes on in-lines. Woe unto your venture if you start emitting marketing
>statements which utters "facts" like this.

>Did you answer the question I asked before: is any of your team highly skilled
>in traditional braking? Have you seen the "triangle" method that we describe
>in the FAQ?  This method gives you stability when stopping; it's the
>breakthrough technique in braking technology.

Somehow I really doubt you can get as much braking power from braking
a single wheel (or two) as you can from heel brakes.  The amount of
pressure you can get from heel brakes can be tremendous.  He's been
rather vague on just how the system might work (understandably :) but
unless you can put the majority of your weight on the brake (or have a
much larger contact patch) it shouldn't work as well.  If it is much
easier to use (a la ABS) it may be useful though...assuming it has no
undesired failure modes :).

Either way...fast braking will require the user to have good fore-aft
balance (as you mentioned).  If you have that you can probably heel
brake...

>>Todd Stiers

>--phil
--
Nigel Tzeng
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