Torque Transmission Capacity of Car Air Con Pump Electromagnetic Clutch

Been asked to look into prototyping a retrofit device needing two electromagnetic clutches.

Proper industrial rated clutch units will make the device too expensive for its market but car air con pump clutch units look to be within budget. Trouble is that there doesn't seem to be any easily accessible hard data on how much torque they can transmit.

Somewhere between 10 and 20 ft lb at between 1,000 to 2,000 rpm ought to open up enough of a market for the device. Obviously the higher power that can be transmitted the bigger the potential market but anything past 20 ft lb won't make much difference.

The clutches will be engaged under light to no load conditions, unlike an air con pump which engages at full load, so odds are it will be fine to push the continuous loading somewhat above that normally needed to drive a running pump. Especially as the user will almost certainly never deliberately demand full motor rated power for any period of time.

My handwaving calculations suggest design continuous torque transmission of these units is likely to be something over 5 ft lb with significant overload capability before slipping. Which looks promising. But it would be nice to know before I commit to doing a lot of work.

Thanks

Clive

I discoverd from empirical evidence that a GM clutch will handle more than the belt that drives it. Had a compressor lock up, the clutch held the pulley at standstill and shredded the belt. Good belt, properly tensioned. Does that help? Maybe some sample testing would be sufficient? 20 fl/lb sounds low for them.

being the HP required to turn the pump, they can handle quite a bit of torque. usually 10-20% of the engine rated HP. limiting factor is always the belt slippage as they typically lock up quite solid when engaged like an auto transmission clutch.
it all depends on the brand/model used and surface area they have with clamping load, id suspect its much higher then you think.

Maybe a riding mower electromagnetic blade clutch is just as cheap and more adaptable.Edwin Dirnbeck

Our skag mower has a great clutch, it has floating type of mount so can be used o anything.

Google turfrunner to locate a service manual to see.

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John Deere makes/made some small diesel lawn/garden tractors with an elctric clutch for various PTO's running 20 horsepower or so. I have heard a car air conditioner is 5 horsepower or so.
Bil lD

Thanks for the input folks.

I'd heard of locked up aircon pumps shredding belts without slipping the clutches so I was pretty sure that the actual limiting torque was higher than might be expected from the size. I've got an industrial 1 nm rated one hanging about the place which isn't that much smaller than a car air con one. Which was about where I started worrying.

I'm going to assume that they are up to the job and start sketching (and pricing) concepts. Market is probably no more than 100 - 200 a year and needs a realistic selling price under £250, preferably under £200, so there isn't much wiggle room. I'm donating the engineering time 'cos its something I can use and I get to keep the prototype.

Garden machinery spares, at least here in UK, are going to be too expensive. Pattern car air con clutches can be found for £25 - £30 each which is in range of doable.

Thanks.

Clive

I have used them to run a belt drive hydro pump, about 5hp at 1800, worked for years...Phil

Phil in Montana said:

I have used them to run a belt drive hydro pump, about 5hp at 1800, worked for years...Phil

Click to expand...

Thanks for that endorsement Phil. Can't beat long term experience.

Clive

From my testing they will handle anything a 2.5 KW series wound 12V DC winch motor can throw at them. 2000-6000 RPM range.

No clutch in that size range is as cost effective since nothing else is produced at the same volume.