Hey guys, I have this old Atlas Snowblower from the early 70's. Its single stage chain driven. I got it off craigslist last year and It runs great, but I think the clutch is going out. What happened was, I got to the end of the drive way and got to some ice chunks which jammed up the auger. The motor never stopped running so I'm thinking this is a slip clutch but then other folks tell me its centrifugal. When I disengage the auger it still spins. The clutch has a band that clamps down around it to stop the auger then when you pull on the engagement lever, the band opens up. Its similar to a chainsaw clutch set up. So you guys tell me, what kind of clutch is this? Thanks.

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I wont comment on the clutch but, FWIW you should have shear pins on the auger shaft for your impeller.

I would agree with the shear pins.If you hit ice chunks that shear pin should snap right off.

Believe it or not, this blower doesn't have any shear pins. I agree, it should have some installed. Thanks for the tip!

Some of the old snowblowers had a slip clutch instead of shear pins. The clutch thing is actually an 'auger brake' , it stops the auger by forcing the slip clutch to slip.

Kinda weird design, it saves 50 cent shear pins, but wears out a $50 clutch...

Looks like it was modified & welded.. is that part of the design?

It hasn't been welded or modified as far as I know. I think part of the spring broke off because it looks like it fastened over the hub. I would post a picture but my camera is junk and won't take good close ups. I J B welded the spring end where I think the end is supposed to be and see if that works. If it doesn't, I'll put in some shear pins on the auger and call it fixed.

Just remember that this snow blower is not a 2 stage type,,,,which means that the slushy stuff will not be "blown very far"!!!
Even dry snow won't go far.
That is why 2 stage blowers are so popular.

I believe that what you have is a wrap-spring clutch.  See, for example, http://www.google.com/patents/EP1499812B1?cl=en, which is a patent on one such.  This would make it a torque limiter, aka slip clutch, or safety clutch.  Some of these will last a VERY long time even when being slipped due to encountering more load than they are intended to transmit - and that's exactly what I'd expect a snow-blower auger clutch to do if ice, rocks, branches etc. get caught.
BTW, I destroyed a single-stage snow blower early last winter when one of the tire chains failed and got sucked into the auger: the "shear pins" failed to work, and the resulting sudden load broke part of the housing around the bearings.  I took the pins out, and they ARE the kind with two necked-down areas one shaft diameter apart... they just didn't break!
Due to corroded Allen sockets on set screws, I haven't been able to disassemble the auger drive shaft from the engine, and so far, haven't even been able to drill them out &  separate the parts!  But, I now have a good two-stage unit, so there's no hurry.

Good tip for removing rusted Allen socket (i.e. hardened steel) screws - use a carbide tipped stone drilling bit - you may need to tweak it a bit first on the grindstone to get it sharp, but it should drill out an Allen screw... I've used this method many times...

Yes...also a good way to drill out stripped phillips head stainless steel screws...
(Keep the bit wet or oil with WD40 or such, or the solder will melt and the carbide will fall out)