speed reducer

[reible]

I have had the speed reducer for quite a while. I got it mostly for drilling with larger bits but I have also found other uses like for turning which makes a huge difference with out of balance items. The 700 rpm down to 100 rpm really makes a difference.

If I had a powerpro I would still keep the speed reducer for doing really slow turning and for my other machines when ever they might need it.

On the subject of the powerpro and the bandsaw, I have no experience here but one thing did occur to me.

I've been gone the last week + and stopped in my home town and thinking back to when I was 12 or so and my uncle thought it would be good for me to learn how to use a tractor. Now this was some years back and I have no idea how modern tractors work, but I would not expect too much has changed in this area.

The tractor has a governor, you have to let the tractor work but you also need to know when to give in and use the clutch. Once you are starting to dig in the governor knows it and provides more power, you simply let the tractor go do its work until it gives you a sign that its got no more push/pull left, digging in or stalling.

So my thought is, when I'm using a conventional bandsaw and I either feel or hear the motor straining I back off on the feed. This would be bad on the powerpro as it is just starting to add the power and attempting to keep the rpm at the set speed. If one could keep feeding at about the same rate then the powerpro would do what it should be doing. Does this make any since?

Don't mind me if this sounds to strange, I've been up since 4:30 this morning and drove for about 9-1/2 hours along with packing and unpacking associated with trips.

Ed

[JPG]

I have had the speed reducer for quite a while. I got it mostly for drilling with larger bits but I have also found other uses like for turning which makes a huge difference with out of balance items. The 700 rpm down to 100 rpm really makes a difference.

If I had a powerpro I would still keep the speed reducer for doing really slow turning and for my other machines when ever they might need it.

On the subject of the powerpro and the bandsaw, I have no experience here but one thing did occur to me.

I've been gone the last week + and stopped in my home town and thinking back to when I was 12 or so and my uncle thought it would be good for me to learn how to use a tractor. Now this was some years back and I have no idea how modern tractors work, but I would not expect too much has changed in this area.

The tractor has a governor, you have to let the tractor work but you also need to know when to give in and use the clutch. Once you are starting to dig in the governor knows it and provides more power, you simply let the tractor go do its work until it gives you a sign that its got no more push/pull left, digging in or stalling.

So my thought is, when I'm using a conventional bandsaw and I either feel or hear the motor straining I back off on the feed. This would be bad on the powerpro as it is just starting to add the power and attempting to keep the rpm at the set speed. If one could keep feeding at about the same rate then the powerpro would do what it should be doing. Does this make any since?

Don't mind me if this sounds to strange, I've been up since 4:30 this morning and drove for about 9-1/2 hours along with packing and unpacking associated with trips.

Ed

Makes sense to me, but Charlese's problem has to do with no load misbehavior.

[charlese]

...
I am under the impression that the undesirable activity stops when actually sawing something. Or, does it return when not feeding the workpiece. Or am I totally confused?

The PowerPro will run very smoothly and turn the bandsaw smoothly at 800 to 950 RPM under no sawing load. It will also saw really smooth in both re-sawing or curved sawing for a little bit. Then - all of a sudden with no change of sawing pressure the PP will buck and bang. The PP will actually jump on the way tubes and also the bandsaw case will jump. This jumping can be felt through the wood and bandsaw table. The jumping of the headstock can actually be seen.

When sawing out little cars with a 1/4" blade, the binding of the blade when sawing a 5/8" radius curve will set off some of those bangs. In a test, I have sawn several 1/2" half circles with a 1/4" blade (this is as tight as you can do)- then for an unknown reason the next test circle will produce banging. This can't be too good on the mechanical parts of both the PP and BS. One time when re-sawing the banging actually twisted the plastic coupler at the PP end. As said earlier, screws in the headstock have come loose.

To answer ED's post - I'm right with you on old tractors. The PowerPro is powerful enough that pushing hard on a piece does not change the speed or give any hint of bogging or straining. My thought is the PowerPro senses the needed torque immediately upon startup and and tries its darnedest to maintain that torque. It is the effect of self correcting (in milliseconds) that causes the banging.

I cannot figure why when ripping on the saw table there is no such banging action. It's got to be related to the spinning of the two 11" bandsaw wheels and the torque they signal to the PowerPro.

It is my hope that a speed reducer will offer another sequence of torque and while operating the PP at a higher speed will make any electronic corrections smaller.

[dusty]

The PowerPro will run very smoothly and turn the bandsaw smoothly at 800 to 950 RPM under no sawing load. It will also saw really smooth in both re-sawing or curved sawing for a little bit. Then - all of a sudden with no change of sawing pressure the PP will buck and bang. The PP will actually jump on the way tubes and also the bandsaw case will jump. This jumping can be felt through the wood and bandsaw table. The jumping of the headstock can actually be seen.

When sawing out little cars with a 1/4" blade, the binding of the blade when sawing a 5/8" radius curve will set off some of those bangs. In a test, I have sawn several 1/2" half circles with a 1/4" blade (this is as tight as you can do)- then for an unknown reason the next test circle will produce banging. This can't be too good on the mechanical parts of both the PP and BS. One time when re-sawing the banging actually twisted the plastic coupler at the PP end. As said earlier, screws in the headstock have come loose.

To answer ED's post - I'm right with you on old tractors. The PowerPro is powerful enough that pushing hard on a piece does not change the speed or give any hint of bogging or straining. My thought is the PowerPro senses the needed torque immediately upon startup and and tries its darnedest to maintain that torque. It is the effect of self correcting (in milliseconds) that causes the banging.

I cannot figure why when ripping on the saw table there is no such banging action. It's got to be related to the spinning of the two 11" bandsaw wheels and the torque they signal to the PowerPro.

It is my hope that a speed reducer will offer another sequence of torque and while operating the PP at a higher speed will make any electronic corrections smaller.

I trust that you have had more than one or two conversations with Shopsmith engineering about this. What seems strange to me is that are the only one reporting this problem. Can it be that no one else is using the band saw with the PowerPro.

I have my band saw on a Power Station so if I had the PP I would not likely experience your problem.

Maybe you should extend an invitation to Shopsmith to come to your shop for real live field testing. Then again, maybe they know exactly what the problem is but don't know what the fix is.

Hope you can get this fixed soon, Charlese. Your PP needs no more stress testing.

Do you know anything about the status of your first PP. Did Shopsmith ever experience the same symptoms with it after it was returned.

[nuhobby]

Charlese is reporting problems that at least 3 other members have described.

To me it's fairly obvious that the control algorithm as currently designed cannot guarantee bandsaw "stability margin" in the controls-engineering definition.

I kept a separate old-motor Shorty station where I run my bandsaw and overarm router. As a multi-purpose sander, tablesaw, jointer, driller, borer, and lathe, I love my PowerPro. But I'm not going to run my bandsaw on it without some substantial proof that a design fix is established. And I don't have the conflict-stamina outside my day-job to "dog" Shopsmith about judging whether or not it's unconditionally stable. I'm still a great Shopsmith "Fan" but no longer a Shopsmith "Fan Boy".

[JPG]

Thank You Chuck for the elucidation. That is a more elusive varmint.

There are times when too rapid response borders on instability with slow responding objects having 'slop' being controlled.

I think you can vouch for that!:(


Here's hoping Jim Mc can 'solve' it!:)