Broken Power Coupler

[jsburger]

I don't see why not as long as you can get the two shafts close enough together to make it work. I have not checked but I think it may not be possible.

[JPG]

This is a bit off topic, but sort of related.

I just bought a used Mark V and am excited to get it up and running. Unfortunately, I can't seem to locate the shaft coupler, and while I found the correct item on the ss website.. the tinkerer within is wondering why I can't just use a jaw coupling, or some other flexible coupling.

Thoughts?

The SS coupler has a couple of design 'features' that are not apparent.

The ends are different so as to preclude using it 'backwards'.

The headstock end has that spring which will push the coupler off the headstock drive hub if the spacing increases due to not securing the headstock and it creeps away.

The coupler ribs and the hub grooves are shallow. That along with the plastic coupler being 'flexible' provides a torque limiter.

The fit is 'sloppy' enough to tolerate shaft misalignment(up to a point).

[greasemonkey2275]

[quote="richardrouse"]This is a bit off topic, but sort of related.

I just bought a used Mark V and am excited to get it up and running. Unfortunately, I can't seem to locate the shaft coupler, and while I found the correct item on the ss website.. the tinkerer within is wondering why I can't just use a jaw coupling, or some other flexible coupling. [quote]

Welcome and I know that I speak for everyone when I say that we would love to see pictures of your "new" SS.

As far as the coupler goes, JPG is exactly right but there is another feature that is very important about the coupler's design. Should something seize on one of the attachments the plastic coupler should snap to prevent further damage to either the machine or the attachment. I looked at all of the options that were out there when I first purchased mine and started restoring it. The more forums that I read throughout this site I began to understand how important that feature was and it was not something that I felt the others would do when the time came. You can find couplers on eBay if you do not want to purchase them from SS but try to stay away from the used because you may not be able to see any cracks in the photos.

[dusty]

This is a bit off topic, but sort of related.

I just bought a used Mark V and am excited to get it up and running. Unfortunately, I can't seem to locate the shaft coupler, and while I found the correct item on the ss website.. the tinkerer within is wondering why I can't just use a jaw coupling, or some other flexible coupling.

Welcome and I know that I speak for everyone when I say that we would love to see pictures of your "new" SS.

As far as the coupler goes, JPG is exactly right but there is another feature that is very important about the coupler's design. Should something seize on one of the attachments the plastic coupler should snap to prevent further damage to either the machine or the attachment. I looked at all of the options that were out there when I first purchased mine and started restoring it. The more forums that I read throughout this site I began to understand how important that feature was and it was not something that I felt the others would do when the time came. You can find couplers on eBay if you do not want to purchase them from SS but try to stay away from the used because you may not be able to see any cracks in the photos.

I don't mean to disagree with anything that has been said here about the power coupler but I do have one question.

Has anyone experienced an operating condition where damage was lessened or completely avoided by having their coupler break or disengage. In twenty five plus years using a Shopsmith, I have not. I have broken plastic power couplers but not as a result of any seizure

[reible]

This subject reminds me of my youth in northern WI where boating was a way of life as was fishing and all manor of water activities. We would get these people, often from IL where I now live who would stop in looking for a new shear pin. Mind you they would be looking for one not two or three. The cost of these were about buck if I remember right. They often had a story where they broke the pin and had to row back in or maybe had to be towed back in.

You got the impression that they thought the shear pin had let them down or better put, out on the water. So why would they want just one? I have no idea. A few would want a nail or other such object to replace the shear pin. We would try and explain that was a bad idea but the customer is always right....... Some time the next trip in was for a new propeller. If I recall at the time a propeller was about $35 and was always purchased with a new shear pin. The really unlucky ones bent a shaft and well the cost went up on that sort of issue.

Woodworking is not a cheap hobby. It costs to participate and if the cost is a few more dollars then you are willing to spend then you might want to rethink your hobby list. Hate to say it but that is especially true of shopsmith parts, but at least they are around and we still can buy there parts, if they weren't where would we turn?

Now having said all that and at the risk of breaking a coupler the next time I use one, I have yet to damage one. I've had a shopsmith since 1976 so that is a lot of time and I still have my original one in use. I do have a couple of extras just in case. If you are going through a bunch of these then I would worry that something is not right in your procedure or mechanically with your shopsmith or SPT.

Ed

[garys]

The headstock end has that spring which will push the coupler off the headstock drive hub if the spacing increases due to not securing the headstock and it creeps away.

As I see it, this spring is a critical part of the design. Should the coupler break or come apart in any way, the spring pushes it off the drive side preventing the motor from throwing it at the user and causing injury. If that spring would break or fall off on my couplers, I would throw away that coupler even if there is nothing else wrong with it and buy a new one from Shopsmith.
I would rather buy a new coupler than have a doctor try to remove one from my face or eyes.

[charlese]

Agreeing with Ed (reible) is the substance of why I bought two spare power couplers. It would be great if I never had to use them.

On Ed's story about boating, I used to motor through a lot of water lilies and weeds. Always kept pliers and an adjustable wrench aboard along with an extra shear pin. Didn't need the extra pin very often while in the water as sliding the broken pin to one side and then putting the small ends in worked to get us back to shore. The prop would turn using only one side of the pin.

[garys]

Agreeing with Ed (reible) is the substance of why I bought two spare power couplers. It would be great if I never had to use them.

I also have a spare coupler in my parts box. If one should break or show unusual wear, I can just pull out the spare and keep working. My Shopsmith came with 2 couplers when new, so even Shopsmith must think it is a good idea to have a spare on hand.

[JPG]

I am still using my original 'zytel' coupler obtained with my then new goldie.


1963

[wa2crk]

I have noticed an unusual circumstance with my couplers. When I installed the Power Pro headstock and got everything lined up I used the belt sander for a project and the coupler was difficult to remove from the belt sander.
A short time later I used my belt sander on the Shopsmith at our community shop and the coupler came off the sander easily.
I had to rock the coupler back and forth after using an SPT on the PP in order to remove it. Any of the SPT's would do this.
Just wondering if the rapid variations from the PP control system is causing the splines in the SPT's to bind up.
I rarely use the bandsaw on the PP because the bandsaw is on a power stand.
Bill V