Speed Control replacement

magnaman · Post by **magnaman** » Mon Jan 30, 2012 9:14 am

I could not change the speed of my '77 finally so I took the speed control assembly out to find it was a basket case. I ordered a new assembly and installed it Friday after finding some Blaster Garage Door Lube (as mentioned on this forum) at the local Lowes home store. It came from the factory with a small blob of grease (which I removed) on one end of the pork chop threads. I also replaced the pin with a 2" #10 bolt as mentioned on here.

In figuring out how this thing works I discovered it takes a lot of force to adjust it to the slow speed. Going faster takes strain off the assembly. And running it as fast as possible takes off all the strain.
So from now on I will turn the speed control to the fastest position when I don't intend to use it for a while. If I plan to do something or have a tool connected like my bandsaw is now I will leave it where it is. Of course when connecting a tool after not being used I have to turn it on and crank it down to slow first but I put a label on the headstock as a reminder.

It doesn't seem logical to leave it set to the highest speed but I don't see anything to be gained by letting it sit for weeks with the max strain on the speed assembly and gears. Everything else on mine seems to be working correctly and now the speed control dial turns easily.

Has anyone else investigated the force needed to slow down the drive? Maybe if I don't have to replace the speed control assembly for another 35 years (for me that will be in heaven if I make the cut!) I should just crank it down to SLOW and let the assembly sit under strain.

pennview · Post by **pennview** » Mon Jan 30, 2012 10:02 am

It's best to park the machine on "SLOW." That way there is less strain on the motor when starting and there is zero chance of you or someone else turning on the machine with the bandsaw or jig saw attached, and damaging one of them or the operator. Thirty-five years is a long time between repairs on the speed control, so it doesn't seem like there's much value in leaving the machine on "fast."

dusty · Post by **dusty** » Mon Jan 30, 2012 10:07 am

magnaman wrote:I could not change the speed of my '77 finally so I took the speed control assembly out to find it was a basket case. I ordered a new assembly and installed it Friday after finding some Blaster Garage Door Lube (as mentioned on this forum) at the local Lowes home store. It came from the factory with a small blob of grease (which I removed) on one end of the pork chop threads. I also replaced the pin with a 2" #10 bolt as mentioned on here.

In figuring out how this thing works I discovered it takes a lot of force to adjust it to the slow speed. Going faster takes strain off the assembly. And running it as fast as possible takes off all the strain.
So from now on I will turn the speed control to the fastest position when I don't intend to use it for a while. If I plan to do something or have a tool connected like my bandsaw is now I will leave it where it is. Of course when connecting a tool after not being used I have to turn it on and crank it down to slow first but I put a label on the headstock as a reminder.

It doesn't seem logical to leave it set to the highest speed but I don't see anything to be gained by letting it sit for weeks with the max strain on the speed assembly and gears. Everything else on mine seems to be working correctly and now the speed control dial turns easily.

Has anyone else investigated the force needed to slow down the drive? Maybe if I don't have to replace the speed control assembly for another 35 years (for me that will be in heaven if I make the cut!) I should just crank it down to SLOW and let the assembly sit under strain.

FIRST and FOREMOST: I strongly disagree with your logic for leaving an idle Mark V set at high speed. If not left where you last used it, run it down to low speed for long term idle use. You do not want to accidently turn on at high speed with any SPT attached.

Setting idle while set at any speed does nothing undesirable to the Mark V that can be avoided by changing that idle speed setting.

The fact that it is easier to change speeds going one direction is easier than going the other is absolutely normal. If you would watch how the belt rides in the sheaves while changing speeds, you will understand this phenomena. Going one direction the belt is climbing up out of one sheave while dropping down into the other.

heathicus · Post by **heathicus** » Mon Jan 30, 2012 10:43 am

As Dusty said (or someone correct me if I'm wrong), there is no additional strain on the speed assembly and gears at any one speed setting compared to any other speed setting. The strain happens when changing speeds. But once the speed is set, there is no more strain with it set to slow than there would be with it set to high. So, for safety sake, and longevity of the motor, it's best to set it to slow when done.

mountainbreeze · Post by **mountainbreeze** » Mon Jan 30, 2012 4:44 pm

Here's a thought...

Lets assume for a moment that someone is going to infiltrate your shop and turn the speed control dial whithout the motor running

Would it be better if it were turned from high speed to low speed or vice versa? Or maybe both are equally bad.

billmayo · Post by **billmayo** » Mon Jan 30, 2012 6:05 pm

mountainbreeze wrote:Here's a thought...

Lets assume for a moment that someone is going to infiltrate your shop and turn the speed control dial whithout the motor running

Would it be better if it were turned from high speed to low speed or vice versa? Or maybe both are equally bad.

Trying to turn the speed control dial toward the SLOW position without the motor operating will damage the speed control assembly. Since I am going to disassemble any headstock I have mounted for repairs or rebuilding, I always turn the speed control dial to FAST without the motor operating or the quill being rotated. This is so I can remove the motor belt plus I do not want to cause any additional damage to any of the headstock operating parts. This has never caused me a problem. This leaves the belt loose so the motor should never be turned on while the belt is loose.

Always turn the quill a few times to redistribute the belt on the sheaves if the speed control dial has been moved without the motor operating.

JPG · Post by **JPG** » Mon Jan 30, 2012 7:47 pm

Not to contradict any one in particular, but rather to nail things down, the following are cold hard facts.

1) The sheaves are going to be under essentially equivalent stress regardless of the speed dial setting as long as they have been given an opportunity to stabilize. The only variability is the position of the motor(v) belt on the two pulleys.

2) Assuming proper maintenance and lubrication, the pork chop is under NO stress once those pulleys do stabilize.

3) As Bill has pointed out, increasing the speed setting is not when damage occurs. Doing so, opens up the control sheave, but without the pulleys rotating, the floating sheave on the motor shaft will NOT take up the belt slack, and under these circumstances the wire loop WILL pull the control sheave open when the pork chop moves away(towards fast).

4) Any time the speed control setting is changed it is best to rotate the pulleys so as to allow the floating sheave to balance the belt tension/positioning.

5) Adjusting the speed control towards slow without the pulleys rotating is when porkchop damage occurs. The porkchop is pushing the control sheave towards the idler shaft sheave and that results in putting a squeeze on the belt. This is why slowing down seems 'harder' and why allowing the sheaves time to shift will minimize porkchop wear. The floating sheave on the motor shaft will respond to the increased tension on the belt and move away from the fan sheave thus decreasing belt tension and that allows the control sheave to slip towards the idler sheave thus relieving the stress on the porkchop.

6) Storing with it set to fast may lead to a less familiar problem. When set to fast, the control sheave is 'wide open'. The belt is positioned near the bottom of the pulley. If the SS is jarred while being moved or stored, it is possible for the belt to drop further and get jammed. When attempting to start up later. the belt may jam tighter and prevent the belt from following the motor pulley with much screeching and creation of hot rubber scent. Not a pleasant experience especially when a 'hot' project gets delayed.

7) All those dire warnings regarding mounting SPT's without checking/setting the speed first are even more appropriate when it has been a long time since it was last run.

8) I would rather an intruder moved it toward fast.

9) The start up load on the motor is indeed much less and start up time greatly reduced when set to slow.

So! I must also disagree with the suggestion to store with it set at fast.

I have reiterated much of what has been said above, but also clarified a couple of details and put it all in one post.

robinson46176 · Post by **robinson46176** » Mon Jan 30, 2012 10:49 pm

Adding only that keeping the sheaves well lubricated will help a lot to ease strain on the pork-chop when slowing down by letting everything move along smoothly.

.

wannabewoodworker · Post by **wannabewoodworker** » Tue Jan 31, 2012 12:23 am

robinson46176 wrote:Adding only that keeping the sheaves well lubricated will help a lot to ease strain on the pork-chop when slowing down by letting everything move along smoothly.

You bring something to mind. What does everybody use to oil the innards once your machine is in good working order? I know Bill likes the Zoom Spout oiler but I have not been able to find it locally except at Graingers and they wouldn't sell to me. Is there another company that sells a long slender spout oiler that allows you to get to the oil holes easily from outside the headstock?

JPG · Post by **JPG** » Tue Jan 31, 2012 2:14 am

wannabewoodworker wrote:You bring something to mind. What does everybody use to oil the innards once your machine is in good working order? I know Bill likes the Zoom Spout oiler but I have not been able to find it locally except at Graingers and they wouldn't sell to me. Is there another company that sells a long slender spout oiler that allows you to get to the oil holes easily from outside the headstock?

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