View Full Version : Anyone here know about hysteresis clutches?

02-17-2008, 02:36 PM
For the engine-powered winch I'm thinking about, I'd like to have a no-contact clutch.

Here's why: With an electric winch, the tension is controlled by turning the motor on and off as the plane climbs. With an engine-driven winch, the engine runs continuously, and the clutch will need to be engaged/disengaged. Most people using the winch will be used to "pulsing" the winch quickly, and that will put a huge strain on the contact surfaces of an automotive AC compressor clutch or a PTO clutch. Seems like asking for trouble.

Anyway, I'm thinking about using a hysteresis clutch. There's a primer here:

Looking at the diagram, you can see there are four gaps. One on each side of the field coil and one on each side of the hysteresis disk.

The moving flux passing through the disk drags it along with the rotor to transmit torque.

It makes sense that each gap lowers the efficiency of the clutch, so I'm thinking about eliminating one of the gaps by doing away with the disk. I'd have two rotating parts. Each would look like half of the rotor, and they wouldn't be connected. The inside part would be driven by the engine, and the outside part would be connected to the winch drum.

Each part of the rotor would have several poles, and I'm thinking the intense attraction between the poles would transmit torque just as well as dragging the flux through the disk.

I'm thinking the reason they use the disk is to eliminate cogging between the poles, not because it's more efficient. I'm not worried about the cogging, since I've got hundreds of feet of nylon line to smooth out the pulses.

Is my thinking all wrong on this?

Oh yeah, I need to transmit a maximum of 200 inch-pounds. Most of the time it's going to be a lot less.


02-17-2008, 06:40 PM
I don't know but maybe you would have better luck on a physicist froum? Its an interesting topic, but I think what you are asking, is in the engineering field/theoretical physics. Let me know what you find out about that.

02-17-2008, 08:59 PM
Offhand, we see your proposed clutch as using electrons/magnet flux twixt driving/driven discs in much the same way a hydraulic clutch connects, using liquid versus the mag flux. Oughta work========

How about the spinning disc/flywheel of an industrial grade sewing machine? Operates at constant rpms, imparting motion to a friction wheel, which is sporadically applied, and in some designs at various distances from the CL of the driving disc. Engage/disengage at will, switch the pitch and sample the sizzle, as Buick used to advertise?


02-17-2008, 09:04 PM
A Ferro-fluid clutch might be easier to make-


Here's the goop,other sources have it cheaper-

http://www.forcefieldmagnets.com/catalog/advanced_search_result.php?osCsid=991d95cb488df498 c2ccd8cd847942f1&keywords=FERROFLUID&osCsid=991d95cb488df498c2ccd8cd847942f1&x=8&y=5

Think of an electric torque converter type arrangement.

02-17-2008, 11:13 PM
Renault used a Ferlec clutch that had a fan shaped bronze disc that might work for your application.

02-18-2008, 01:12 AM
I can see making something using a planetary gearset- drive one member with the engine, the winch drum with another, and put an aluminum disc on the third. When the disc is turning, the output shaft isn't. When you slow or stop the disc, the output shaft turns.

A stationary electromagnetic assembly surrounds the disc. The more strongly it's energized, the more braking action is applied to the disc, and the more torque is applied to the winch drum.

If mechanical control is good enough, the electromagnet can be replaced by an array of permanent magnets. This array can be hinged over the disc, or swung away from it.

A.K. Boomer
02-18-2008, 01:42 AM
Dodge cummins diesel Fan clutch anyone? salvage yard?

Rip out the bi-metal temp spring in the center and build a little bearing and pressure actuated cam twist --- walla, you can control the viscous fluid inside the unit to grab or not grab, whats more they have a nice transition so you can have good variable control, Those fan units are massive and should handle some good torque --- although you know more what your up against.

Just a drunkin thought...