Author Topic: What is this called? Clutch?  (Read 1116 times)

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Offline davidhere40Topic starter

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What is this called? Clutch?
« on: March 10, 2012, 10:49:40 PM »
I came up with an idea for a sort of clutch. Basically it is a system with a single servo motor with multiple independent gears that can be selectively engaged to the servo motor or disengaged. When disengaged, they would be locked in place. Each independent gear could basically be used to control a separate degree of freedom of a robot or automation system.

I haven't been able to find any similar clutch mechanism design at all.

Anyone know what this sort of thing is called? Every heard of such a thing?

Offline newInRobotics

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Re: What is this called? Clutch?
« Reply #1 on: March 11, 2012, 06:27:30 AM »
Box full gears is normally callad a gearbox, or transmission  ;D

Mechanism You described must have been used at some point in time, probably when motors where expensive, but not any more I believe, as such a mechanism would be very bulky and not very adaptable; plus, motors are fairly cheap and are much more efficient to use than 1 motor driving different joints. Imagine it this way, nowadays people want separate joints to be actuated at the same time, that would not be possible with mechanism You have in mind.
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Offline davidhere40Topic starter

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Re: What is this called? Clutch?
« Reply #2 on: March 11, 2012, 10:18:04 AM »
Thanks :)
Yeah. but let me explain why. I need more than 60 brushless servos. Each one costs around $300 or more. That's $18,000 for 60. Using this mechanism, I could cut the cost down to around $7000 for 1/3rd the servos.

I could need another 60 more for small robotic arms. But, I haven't found brushless motors that act like hobby servos yet. They all seem to be designed big (like 4 pounds minimum?), which doesn't work for a small robotic arm. Not sure what to use because I can't used brushed motors, since they'll require maintenance and break down faster.

I spent several hours yesterday searching for this. I finally found out what I think it might be called. But no one seems to use it the way I'm thinking.

It seems to be called an electromagnetic toothed clutch.

Offline Soeren

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Re: What is this called? Clutch?
« Reply #3 on: March 11, 2012, 12:58:14 PM »
Hi,

I recently stripped down a "business size" color LASER printer that used a lot of electromagnetic clutches to divert motor power to different (parallel) axles. This was made as part of the printer - th only way to get it to fit in the limited space.

You can do the same, but you'll have to make the transmission from the ground up, as you won't find a standard transmission that fits your need.

When you do the numbers on what you'd save, you're missing one (expensive) clutch per servo saved, some gears to change direction and perhaps speed, the transmission encasing and the time you'd need to spend designing each of them (plus the likely failed attempts before you get it right).

I think you'll find it way more expensive than using separate motors/servos

Perhaps you're beginning to realize why industrial robots cost a lot. If they could be made much cheaper, they would be, as this would create a much wider customer segment, sweetening the bottom line for both seller and buyer.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline davidhere40Topic starter

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Re: What is this called? Clutch?
« Reply #4 on: March 11, 2012, 08:30:07 PM »
I did find this cool video of a toothed clutch:
toothed clutch


The clutch mechanism I'm designing is not so complicated that it would cost anywhere near the $600 would cost for two more high quality servos. Besides, for $350, I can get a servo motor rated at 126 lb-in with the controller (shared among other servos). That would allow the single motor system to be cheaper and still faster than a three motor system.

I plan to use a couple simple solenoids to engage and disengage the drive.
Besides that, it's basically a metal disk, and a pulley.
The pulley would be connected to a belt drive or whatever drive I end up using.
The metal disk would be permanently attached to the motor shaft.
When the solenoid is on, it would engage the pulley to the motor shaft. When off a simple spring (or maybe a second solenoid) would pull it back into a locked position.
Solenoids are dirt cheap. The rest is just a few simple metal parts.

The servo motor would be stopped whenever engaging or disengaging, and could be slowly started to make sure the clutch engages well before it starts moving.
The servo motor itself controls speed and direction. So, no need to worry about that. I think this solution is much better than spending 600 on additional motors.
Seems feasible to me.

 


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