Looking for servo with clutch

Anyone know where I can find a servo or stepper that has a clutch built into it? Neet to be able to disconnect the drive unit from the shaft.
Thx Scott Kelley
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wrote:

Look at the Vex products at (of all places) Radio Shack.
JM
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The website only shows one servo - no mention of a clutch. Do they have more stuff at the stores than is on the website?
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wrote:

Details are lacking, for sure. I've been told that there's a clutch in the motors & servos. Not electrically operated, though.
JM
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Scott Kelley wrote:

When you say "servo" do you mean an RC servo, or an industrial DC motor used in a servo application? If the later -- like a stepper -- there are clutch units you can buy from places like Small Parts. You can select the torque at which the clutch slips, as well as things like shaft diameter. They're not cheap.
If you mean an RC servo, there are "servo savers" that aren't true clutches, but they allow a certain amount of slip.
-- Gordon
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I was actually referring to RC servos. Preferable though would be a stepper motor. I need a fairly heavy duty unit (it will operate the throttle on an engine). It will have to have an actual electrically operated clutch to fully disconnect it. I can imagine that there may be some automotive cruise control units that would work, but I am not at all familiar with what is out there.

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automotive cruise control units:
most I've seen are vacuum actuated,
a vacuum line running from the intake manifold to the throttle actuator. throttle actuator is a diaphragm in a can. has 2 solenoids inside. one solenoid opens a valve that allows negative pressure (vacuum) to actuate the unit. The other solenoid is a "HOLD" valve. it keeps the actuator in whatever position you vacuumed it to.
Rich
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A cheap and easy way to overcome your problem would be to get rid of the mechanical throttle control altogether.
Servo controls the throttle all the time - when remote controlled the radio controls the servo, when manual control is wanted the accelorator pedal controls a pot which goes to the analog input of a PICAXE which uses its PWM output to drive the servo.
Cost? Maybe $10 plus the servo
David
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On Wed, 7 Sep 2005 04:26:19 -0700, "Scott Kelley"

You might need to give a little more info on just how you want ot control the throttle. A clutch like you describe might cause throttle positions problems if you want to reconnect to the throttle after disengagement. If the throttle is spring return, then the servo would have to go back to the initial position prior to reengagement. You could use two gear wheels, one on the throttle shaft, and the second on the throttle positioning servo, which is on a hinged mount. This would position the throttle. A second servo would push/pull the first servo so its gear would engage/disengage from the throttle shaft gear. Replacing the typical auto throttle return spring with a much weaker one would take a lot of load off of the servos. Lots of possibilitys depending on just what you want to accomplish.
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