Fork-travel problem - missing the forest for the trees?

OK - this is starting to look to me like it has the potential for
being a classic case of "missing the forest for the trees". In my
narrow-mindedness, I can hardly start to imagine what
"Intellicorp001" would want to do with all of the information that
some of the proposed solutions would generate. What end result
are you after? Why do you need to record the movement of you
motorcycle forks? Are you interested in tuning the damping, and
want to make sure you are utilizing their full stroke under
typical riding conditions? I'm just stepping back and looking at
what we're after here; it was, after all, claimed to be a "teensy"
problem.

Carlos Guillermo
VERVE Engineering & Design

-----Original Message-----
From: elson [mailto:elson]On Behalf Of Jon Elson
Sent: Wednesday, October 31, 2001 12:06 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Newbie-esque problem

Intellicorp001 wrote:

> Hi All,
>
> I've been lurking around here since July. I've been getting a

feel for

> whats available, what I might need & what I can afford. The

level of

> expertise on this board is just awesome & I'd like to thank all

those who

> generously contribute their time.
>
> I have a teensy problem at the moment & I wonder if I could get

some

> advice. I want to record the movement of my motorcycle front

forks. I have a

> recording device (pic microprocessor based) and I want to feed

it with

> positional information about what the forks are getting up to. I

had first

> thought about a slide potentiometer but pricey much? Wow, I'm

looking to

> spend $50 not $500. Resolution wise, analog would be overkill,

steps of 100

> would be great, steps of 20 would be sufficient.
>
> You guys measure position all the time, admittedly with way

more accuracy

> than I want, but can you think of a cheapy, rugged (waterproof

would be nice

> to have) way for me to 'read' the position of my forks ?
>
> Sorry this isn't on topic but you don't have a coffee_lounge for

off-topic

> posts.
>
> Time is money & money is beer so there's a case of 'the beer of

your choice'

> for the best answer.

Slide pots up to about 8" are pretty standard items, available in
various
catalogs. Check Marlin P Jones, Mendelson, Alltronics. These are
used
as gain pots on sound and light boards. The ones for sound gain
are
log taper, but pan pots and lighting board pots are linear. I
think, for
relatively short term testing, this would be the easiest way to
go.
Another way would be a low-cost shaft encoder and the 'string'
method. You attach the encoder to one part, and a rod to the part
that moves against it. You use a fine steel cable, or even
fishing
line, and run it from the moving part, wrap it around a drum on
the
encoder shaft, and then tie it to the end of the rod with a
spring.
The spring holds the 'string' taut on the drum, and rotates the
drum
when the forks move. this could be made pretty weatherproof if
you
intend to keep it on the bike for a long time.

Jon