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Posted by Padu on February 14, 2007, 2:32 pm
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Hi,
I'm seeking for suggestions on how to automate the throttle cable of my ATV.
I tried using a small gearmotor I had home where the cable rolls around the
axis (on a pulley) of the motor. It was a total failure. The motor is too
weak to pull the cable. I've measured the force necessary to pull the cable
up to its limit and it is about 18 pounds (80N?)
For brakes I have already bought firgelly linear actuators and some cable
potentiometers (to close the loop), but that solution costs about $350. Do
you have any other idea?
Cheers
Padu
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Posted by Gordon McComb on February 14, 2007, 2:49 pm
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Padu wrote:
> I'm seeking for suggestions on how to automate the throttle cable of my ATV.
> I tried using a small gearmotor I had home where the cable rolls around the
> axis (on a pulley) of the motor. It was a total failure. The motor is too
> weak to pull the cable. I've measured the force necessary to pull the cable
> up to its limit and it is about 18 pounds (80N?)
>
> For brakes I have already bought firgelly linear actuators and some cable
> potentiometers (to close the loop), but that solution costs about $350. Do
> you have any other idea?
I would bet a great deal of the force required for the throttle is due
to a heavy spring on the carburetor or on the handlebar lever of the
ATV, which you'd want with a human rider. You don't need it if you are
using a motor in a push-pull situation.
I think you are better off removing the spring, or replacing it with one
that requires less force, and trying the motor again. This is going to
be your cheapest method.
OTOH, if the force is needed because of friction in the cable, remove
the cable, and attach the motor to the throttle plate lever on the
carburetor. With any luck, a cheap hobby servo ought to be able to move
that.
-- Gordon
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Posted by Padu on February 14, 2007, 3:01 pm
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"Gordon McComb"
>
> I would bet a great deal of the force required for the throttle is due
> to a heavy spring on the carburetor or on the handlebar lever of the
> ATV, which you'd want with a human rider. You don't need it if you are
> using a motor in a push-pull situation.
>
> I think you are better off removing the spring, or replacing it with one
> that requires less force, and trying the motor again. This is going to
> be your cheapest method.
>
That's a great idea, even more because I've already spent some time
designing and fabricating the bracket to mount the little motor.
> OTOH, if the force is needed because of friction in the cable, remove
> the cable, and attach the motor to the throttle plate lever on the
> carburetor. With any luck, a cheap hobby servo ought to be able to move
> that.
The carburator of this [kid's] ATV is a bit different from the ones I've
seen before. Well, I'm not even sure if what I've seen was the carburator,
but the cable goes inside a cylindric chamber where it lifts a small piece
of plastic (through a spring, that I will replace by a weaker one now) and
allowing gasoline to go through. It doesn't look like a venturi in any way.
I guess replacing the spring will solve my problem... I'll try. A million
thanks!!!
Cheers
Padu
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Posted by Gordon McComb on February 15, 2007, 3:25 pm
Please log in for more thread options Padu wrote:
> Well, I've extracted the spring from the carb today. It is 2" long, OD is
> 0.354" and the wire thickness is around 0.025". It is pretty strong.
> I've been looking at mcmaster and small parts inc website looking for a
> weaker spring, but so far for that type of spec (length and diameter) they
> only have ones that are as thick or thickier...
>
> do you know any place that sells weaker springs?
Take it into a motorcycle shop and see if they have something that will
about work. Or, wind your own.
-- Gordon
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Posted by Wayne Lundberg on February 14, 2007, 7:03 pm
Please log in for more thread options Try Muscle Wire for the throttle. You can control contraction and expansion
very nicely by adding or subtracting electrical energy. Stretch five inches
taught, give it a one volt shot and it will contract .X, and it's
proportional all the way. Double it up if you need more power. No motors
required. It's an ideal solution to throttle control.
Wayne
> Hi,
>
> I'm seeking for suggestions on how to automate the throttle cable of my
ATV.
> I tried using a small gearmotor I had home where the cable rolls around
the
> axis (on a pulley) of the motor. It was a total failure. The motor is too
> weak to pull the cable. I've measured the force necessary to pull the
cable
> up to its limit and it is about 18 pounds (80N?)
>
> For brakes I have already bought firgelly linear actuators and some cable
> potentiometers (to close the loop), but that solution costs about $350. Do
> you have any other idea?
>
> Cheers
>
> Padu
>
>
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> I tried using a small gearmotor I had home where the cable rolls around the
> axis (on a pulley) of the motor. It was a total failure. The motor is too
> weak to pull the cable. I've measured the force necessary to pull the cable
> up to its limit and it is about 18 pounds (80N?)
>
> For brakes I have already bought firgelly linear actuators and some cable
> potentiometers (to close the loop), but that solution costs about $350. Do
> you have any other idea?