Dog cluctch

I think I understand what you are talking about. A torque limiter so if something get stuck between the teeth of the mower, the " clutch " will slip. I think one could calculate the angle if one knew the spring rate of the spring and the torque it should slip at. But you probably do not know either of those things.

Do you think it would be good if it took 70 % more force before it ratchets? If so then use 30 degrees. If it were me, I would change the angle of the parts you made. Would not be as strong and would have a lot of backlash, but would give you another data point, and if if breaks then you can make another.

If you think 70 % more is not the right amount, let me know and I will make another back of an envelop calculation.

=20 Dan

I've seen one of those before and was told it was a torque limiting clutch. Googling gives a bunch of hits but I didn't see exactly what you are describing. Maybe you could update it with something more readily available? Art

Not sure if this will help you but on chip conveyors for CNC's, there is often a couple disks with steel balls held captive in less than 1/2 diameter deep holes forced together by a strong spring. If all goes well, torque is applied, we get a chip jam, the balls and spring cause the plates to move away from each other protecting the drive system. Too late for me to draw you a picture.

Night,

Wes

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller

I think I understand what you are talking about. A torque limiter so if something get stuck between the teeth of the mower, the " clutch " will slip. I think one could calculate the angle if one knew the spring rate of the spring and the torque it should slip at. But you probably do not know either of those things.

Do you think it would be good if it took 70 % more force before it ratchets? If so then use 30 degrees. If it were me, I would change the angle of the parts you made. Would not be as strong and would have a lot of backlash, but would give you another data point, and if if breaks then you can make another.

If you think 70 % more is not the right amount, let me know and I will make another back of an envelop calculation.

Dan

This part may be coming back in a day or two and if it does then I'll try 30 deg. Art is probably right that it is called a torque limiting clutch but the web is useless on finding details on it. New parts are out of the question, gotta stay cheap you know..;>)) It's good to hear your feedback so I can get on the right track here. Thanks. phil

Stronger spring?

You can't tell by inspecting the old part, or by sawing the old part apart to see?

I agree with the rest of the responders that this is probably a torque limiting clutch. It sounds like someone was being very aggressive with the mower to wear it out -- then to put a penny behind the mechanical fuse, as it were. I'd check the rest of the mower for subsequent breakage, or for worn parts that are absorbing way too much power.

I know what you're talking about here, Wes. The lead screw on my turnpro 13x40 is set up like that. Might be too light for this mower though. One thought comes to mind and that is maybe the owner was curious about what I did and took it apart and might have lost the anchor key behind the adjusting nut. He did say the nut came off twice! That would relieve the spring, eih? Something is not right here. I'll let you know what happens.... phil

This is usually called a slip clutch. most clutches like this have the same angle on the used side of the tooth as on the unused side, so can you tell the angle on the unused side. Is the spring setup so you can compress it more or add washers behind it?

Phil, is the wooden pitman arm still on the mower? This is the secondary safety point on old mowers. It will break if the slip clutch doesn't slip. On old mowers, the wooden arm is usually rotten after being outside in the weather for a few years. It may also have been replaced by a steel arm.

Probably someone was mowing brush with the mower and jammed the cycle bar one too many times and decided to fix it good and for ever!

I loved watching the cut grass fall behind the cycle bar until I ran through a phesant's nest and cut the legs off the hen. Cats also were a problem.

Paul

Sprag clutch?

In searching for the above, I also turned up this little gem! Automatic Transmission/Transaxle Flash Animations

I think I understand what you are talking about. A torque limiter so if something get stuck between the teeth of the mower, the " clutch " will slip. I think one could calculate the angle if one knew the spring rate of the spring and the torque it should slip at. But you probably do not know either of those things.

Do you think it would be good if it took 70 % more force before it ratchets? If so then use 30 degrees. If it were me, I would change the angle of the parts you made. Would not be as strong and would have a lot of backlash, but would give you another data point, and if if breaks then you can make another.

If you think 70 % more is not the right amount, let me know and I will make another back of an envelop calculation.

Dan

So far it looks like the 30 deg angle is the way to go. Don't know if that is the most efficient angle but but....I may not see another. The original angle appears to be 45 deg judging by what is left of the lugs and that may be the original problem. This mower does have a wooden pitman arm and a v-belt that could slip if bound up hard. Anyway, the guys mowing for the year is done and he's happy! phil

Yeah sickle bars are nice and quiet compared to most modern cutting methods. The quiet part is what caused a lot of the problems. The animals didn't hear you coming and didn't run. Of course I would rather not hit a 'chuck hole while on a horse drawn unit though. Not much in the way of suspension or comfort with steel wheels and a steel seat!!!

Sounds like an old McCormick-Deering type sickle. They used a ramp type limiter like that on a couple of the old horse drawn units. Basically two ramped sections held together by spring. Seem to remember that the angle was steeper than 45 degrees. The one we had was a LONG LONG time ago.

It sure would be nice to know this angle just for curiousity sake. I have a shipfitters wedge and it's angle is 11 deg. It will not slip out when driven in with a hammer. So this angle may be too steep for this application, eih? This angle seems to be a rare bit of info.... phil

I visited one of the local Amish earlier. His friend uses an OLD New Idea that had this style clutch on it so I drove over and took a closer look. His has some wear but it measured at just a touch under 32 degrees. I would say new they were probably 30 even and have worn in a bit.

My guess is that the original angle was 30 degrees. For any amount of torque , any angle will work as long as the spring rate is right for that angle. If you had two flat disks, that would work with enough force pushing them together. So the designer probably choose an easy angle to cut with tools that are easily bought.

=20 Dan

My guess is that the original angle was 30 degrees. For any amount of torque , any angle will work as long as the spring rate is right for that angle. If you had two flat disks, that would work with enough force pushing them together. So the designer probably choose an easy angle to cut with tools that are easily bought.

Dan

Great news guys! Thanks for looking into it, eih? So it is