Shopsmith Forums

JPG40504 wrote:This is one of those things not intuitively obvious'. It becomes apparent through much observation and gaining understanding of what happens as the drive belt(motor) is pulled down into the variator.

Two(three?) things happen. The obvious one is the motor belt rides between the sheaves at a reduced radius. The 'other' thing that happens is the variator shifts in/out along it's shaft to accommodate the belts moving up/down in the sheaves in opposing direction. As the 'inner' side of the motor belt lowers into the variator, in addition to causing the sliding center sheave to move 'outward', it causes the variator to slide inward. The motor belt tries to maintain a centered position between the sheaves. Inward/inner and outward are relative to the location within the power station. Inward is towards the motor, outwards is toward the end where the tink tink tink was occurring.

Now the belt going to the output shaft is changing as a result of the variator being raised(the motor belt is being pulled down into the variator by raising the shaft it is turning on), the output shaft belt is being 'loosened' by the reducing spacing between the variator shaft and the output shaft. Also the center sheave sliding outward puts pressure against the inner side of the output shaft belt. End result then is the output shaft belt rides at a greater radius than before.

The inverse occurs when the motor belt is slackened by lowering the variator shaft.


Now for the 'speed up caused by moving the motor pulley, and why it made the tink tink tink go away. When the motor pulley is moved 'in' on the motor shaft,(or moving the motor 'in') the motor belt continues to seek a centered position between the variator sheaves. Doing so causes the variator to shift inward, thus increasing the clearance to the frame(tink tink tink elimination). That inward shift causes a slight decrease of the belt radius since the belt is also being pulled further into the variator which causes the center sheave to move outward and the output shaft belt rides at a slightly greater radius. Pant Pant Pant!

This 'understanding' came with much pain(thinking too hard) and consternation as I ran into the same issue when I first got my power station 'used'. As I came to discover, it was assembled from parts that were acquired by an e-bay seller and assembled for sale. There were 'extra' parts and mis-assembled parts and I had little faith that the motor mount was as it should be(long screws and multiple nuts and washers). I have since come to realize that Rube Goldberg motor mount was OEM! Anyway, way too many hours was spent observing the effects of moving stuff relative to other stuff. I also spent some time thinking of a way to use an 'extra' variator(another e-bay purchase from Skip Campbell) as a speed 'alterer' on a mark 5. That is an ongoing thingey. Having that variator 'in hand' added greatly to my understanding of what what happens inside the power station.


FWIW, moving the output shaft pulley will also cause shifting the variator sliding positions. The thing to be avoided, is both belts trying to center themselves and preventing each other from being successful.(another elusive thing to understand:(). When all is well, both belts do not experience side forces when equilibrium is attained.

Sorry to be so verbose, but I have 'learned' that ss info is not always 'complete'.

reluctant43 wrote:Whew! but I think I get it. Maybe I should see if there is also a set screw on the output shaft pulley (I did not look for one before and I presume this is the pulley on the drive shaft?) and if so I could move it in a smidge to assure the belts are in balance now I have moved the motor pulley? Too late for me to do it now, but I might give a look in the AM if this seems a good idea...

dusty wrote:Do we all agree that the motor pulley and the spindle pulley are both firmly attached (by keys and set screws) to their respective shafts?

Do we also agree that they neither change position on their shafts nor change width?

Do we still further agree that the Power Station is most noisy when operating at high speed?

Are we all aware that the power station motor requires occasional lubrication? These bearings are not sealed. They need to be oiled.

By the manual (unless I have missed something) there is no other preventive/periodic maintenance to be performed.

So why is the Power Station so @#$%*& noisy?

JPG40504 wrote:The belts are 'stiff'.

The belts take a set(or never get rid of oem set).

The set causes varying belt tension.

That varying tensions on the two belts most of the time are not synchronous and create varying beat frequency sounds.

The tension(from the belts) on the variator is greatest at high speed.

The slide the variator shaft is attached to has a very sloppy fit.

That slop allows the slide and shaft and variator to wave back and forth creating a rattling noise in the process(as well as causing the variator center sheave to oscillate on the shaft.

The motor is mounted to a thin sheet metal deck(efficient mechanical motion to sound convertor).


May be more but that is off the top of me noggin!

dusty wrote:I assume you have experienced this and have, to some extent, reduced the noise level. If so, details would be appreciated.

I have eliminated the theory that the sheet metal vibrating is the cause of the noise I experience. I did so by introducing (temporarily) thicker materials into the mount. I gained nothing by doing so.

The variator slide I tried to shim even though I see no sloppy movement in that shaft except when changing speed.

Both of my Power Stations are as noisy as ever.

JPG40504 wrote:The belts are 'stiff'.

The belts take a set(or never get rid of oem set).

The set causes varying belt tension.

That varying tensions on the two belts most of the time are not synchronous and create varying beat frequency sounds.

The tension(from the belts) on the variator is greatest at high speed.

The slide the variator shaft is attached to has a very sloppy fit.

That slop allows the slide and shaft and variator to wave back and forth creating a rattling noise in the process(as well as causing the variator center sheave to oscillate on the shaft.

The motor is mounted to a thin sheet metal deck(efficient mechanical motion to sound convertor).


May be more but that is off the top of me noggin!

BuckeyeDennis wrote:I agree with most of that. But on mine, at least, the variator slide gets clamped down nice and tight when you lock down the speed adjustment lever. It sounds like Dusty's does too.

The thin sheet metal deck is the root cause of the problem. Not so much because it is a good sound transducer, but rather because it is an inadequate structural member between the motor and the variator housing.

When the belt tension varies, for the exact reasons you mention, the sheet metal flexes, allowing the motor and the variator housing to move just a bit. This turns the cyclic belt-tension fluctuations into mechanical vibration. The vibration, in turn, shakes everything on the Power Station. And at that point, if it can make noise, it will. Especially when the vibration hits a resonant frequency.

Now imagine that the variator housing and the motor were both bolted securely to a granite block. No matter how much cyclic belt tension variation you get, neither the motor nor the variator housing is going to move. The belt tension becomes an internal stress only, plain and simple. No movement, no vibration. No vibration, no buzzing or rattling.

Here's a link to a post showing the stiffeners that I installed in mine .. it's near the bottom of the first post. https://forum.shopsmith.com/viewtopic.php?t=12217 That Power Station was mighty noisy without the stiffeners, and now it purrs like a kitten.

JPG40504 wrote:Aha!!! You da one!!!!!:)