Re: Ball screw reduction ratio

Padu, have you checked our fabulous
http://www.industrialliquidators.com/locations.html
here in San Diego?

"Padu" <padu@xxxxxxxxxxxx> wrote in message
news:rfKdnWeNL4pjG-7ZRVn-tQ@xxxxxxxxxxxxx
"Gordon McComb"
Since you're not looking for accuracy or smoothness in motion, a simpler
leadscrew may work better, and would probably last longer. It works on
the same basic principle as a ballscrew, but doesn't rely on the
reciprocating ball bearings. These aren't all that expensive new; Reid
Tool and others sell these in standard lengths, with various pitches and
diameters to suit your needs. You'll also need some bearings and blocks
to set the shaft into. These are actually more expensive than a 12" lead
and matching nut!

I've thought about lead screw, but I didn't like their efficiency. Since
the
solution goes on a mobile platform, I was thinking about the energy
savings.
Now you expose a new variable that I hadn't thought before (longevity).
I'll
have to rethink it, but since it will be used for breaking, I believe the
duty cycle is very forgiving.


My concern would be the "hammer effect" you'd get powering that motor to
3000 rpm for the under one second you need for full travel.


Yes, if no gear reduction is in place, I will have to carefully design the
acceleration curve in order to avoid jerking. The thing is that we are out
of [official] budget, and a new gearhead for this motor costs over $600
bucks. I'm monitoring ebay for something compatible with my motor, but so
far no luck.


Are you sure a 200-300 rpm 12 volt gearmotor, attached to a long enough
lever, wouldn't be enough to actuate the brakes? They're spring return
already, I'd imagine. You can test the torque needs with a fish scale.
Try it along different lengths of a 6-12 inch lever.

I have a 12V 190RPM laying around, but I need to perform a few tests to
check its torque (ebay stuff, no data***). If I had the linear motion
device (either a ball screw or a lead screw), then I could go one step
further and test how it performs actuating the brakes.

Another thing that I haven't decided yet is if I will actuate brakes
(front
and rear) individually or have only one actuator for both. The first has a
technical advantage for off-road riding, but increases the complexity of
the
system in all aspects (hardware, electronics and software)

Cheers

Padu

-- Gordon




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