Still Trying to Fully Understand

[dusty]

I pulled the dimensions from my drawing because some were in error. It appears that I don't know how to do center/center measurements on shafts. I will add them back when I am confident that I have them right.

[dusty]

Nicely done sketchup work. I am curious what the eccentric positioning was when the shaft spacing was measured.

I didn't have an answer until I went out to reopen the headstock and take new measurements. While there I took a snap shot that I hope answers your question. I suppose you could call that 7:00 o'clock maybe 6:45 o'clock.

20190123_083704.jpg (1.31 MiB) Viewed 12598 times

[JPG]

Nicely done sketchup work. I am curious what the eccentric positioning was when the shaft spacing was measured.

I didn't have an answer until I went out to reopen the headstock and take new measurements. While there I took a snap shot that I hope answers your question. I suppose you could call that 7:00 o'clock maybe 6:45 o'clock.

20190123_083704.jpg

Thank You! I will mean more with updated dimensions.

[dusty]

If I understand how the eccentric works, its effect on shaft positioning is almost negligible. I can see how the shaft might be moved maybe as much as .020" by the adjustment that has been applied to my Shorty. It seems to me as though the maximum amount of shift is about .162" (understanding that the can be moved in any direction by rotating the eccentric).

My documented dimensions could very easily be off by those amounts.

[JPG]

The effect on shaft positioning is mostly vertical with some sideways positioning as well. The extreme vertical positions are 6 and 12 o'clock of the slot and 9 and 3 o'clock for the horizontal positioning.

The Mark 5/V uses the vertical movement to control Poly-v or Gilmer belt tension. The horizontal positioning is a byproduct and not intentional.

The Power Pro uses both, but is essentially a tension equalizer between the two poly-v belts.

[Hobbyman2]

Wondering if the amp draw on the motor was measured under load during these speed changes?

[dusty]

The effect on shaft positioning is mostly vertical with some sideways positioning as well. The extreme vertical positions are 6 and 12 o'clock of the slot and 9 and 3 o'clock for the horizontal positioning.

The Mark 5/V uses the vertical movement to control Poly-v or Gilmer belt tension. The horizontal positioning is a byproduct and not intentional.

The Power Pro uses both, but is essentially a tension equalizer between the two poly-v belts.

I concur with all you have said here BUT I don't believe I have ever adjusted the eccentric to an extreme at anything other than at near 6 o'clock (as shown in the photo). I really don't know because I have never paid attention to that detail until now. All that I specifically recall all adjusting the eccentric is "don't over tighten the bolt/nut for fear of cracking the the casting".

If I remember to do so, I will check this out the next time I adjust the eccentric; an event that may never happen again in my life time. That does not happen often. I am no longer the heavy (daily) user of my Shopsmith like I once was.

Hmmm, maybe I should open them both up just to clean, oil and adjust as required. Maybe I'll need to tweak the poly-v belt tension.

[algale]

Maybe I don't use my machine as much as the next guy, but I haven't had to adjust the eccentric ever and it seems fine. But I'm getting paranoid. How would I know if I needed to?

[dusty]

Maybe I don't use my machine as much as the next guy, but I haven't had to adjust the eccentric ever and it seems fine. But I'm getting paranoid. How would I know if I needed to?

The belt would likely slip on the pulleys and I suspect (repeat suspect) that you would feel a heat buildup on top of the headstock. Bet way - schedule a cleaning and lubrication session and then check the poly-v. Fifteen minutes to avoid a lot of frustration.

[JPG]

The only reason to adjust the eccentric that I have experienced was due to age that led to the belt slipping. That slipping was exacerbated by overloading which likely created wear. My Goldie is currently at about 10 o'clock with the original Poly-V belt.