Poly-V Belt Alignment

[dusty]

Watching Nick, in Sawdust Session 23/Shopsmith Reborn Part 3, he very clearly defines how the poly-v belt should be aligned on the Drive Shaft. He states that there should be 3 grooves open on one side (left) of the poly-v and only one groove on the other side (right). He is very emphatic about this.

I look at mine, which has never been apart, and I find 2 grooves on each side. My Mark V is almost twenty years old and I believe has been this way since day one.

Should I change it?

[heathicus]

Watching Nick, in Sawdust Session 23/Shopsmith Reborn Part 3, he very clearly defines how the poly-v belt should be aligned on the Drive Shaft. He states that there should be 3 grooves open on one side (left) of the poly-v and only one groove on the other side (right). He is very emphatic about this.

I look at mine, which has never been apart, and I find 2 grooves on each side. My Mark V is almost twenty years old and I believe has been this way since day one.

Should I change it?

When I took mine apart, it was the same as yours. Despite Nick's instructions, I put it back the way I found it.

[JPG]

This has been dis 'cussed' before! Maybe someone can find the thread!

As I recall, the facts are that they MAY vary! The important thing is proper alignment from the idler shaft pulley to the the main shaft pulley. I believe for some unknown(to me) reason, they have been created two ways.

This is the 'does the poly-v belt start in the 2nd/3rd/4th/?? groove from the main output shaft end(quill end) 'debate').

IMHO it belongs in the groove that puts the least lateral stress(misalignment) on the poly-v belt. It needs to be centered on the idler shaft pulley.

[dusty]

One half of this issue is alignment of the idler shaft with respect to the drive shaft. Since there are no adjustments, I assume that the parts are all machined so that if assembled properly, the groves just all line up perfectly.

However, if you go back and watch the Sawdust Session, you might not be real comfortable with that assumption. The idler shaft position within the eccentric does not seem to be a precision fit. The idler shaft position might be tweaked a "little" (if need be") to obtain the groove alignment.

Am I wrong??

[robinson46176]

I look at mine, which has never been apart, and I find 2 grooves on each side. My Mark V is almost twenty years old and I believe has been this way since day one.

Should I change it?

If it ain't fixed, don't broke it...
-
-

[JPG]

No, I think you are correct. There apparently are different versions of the eccentric(extra hex-headed screw and with/without set screw retainer/centerer). There may be other production variables.

[dusty]

If it ain't fixed, don't broke it...
-
-

Yes, farmer, very good advice. However, I am posturing for a rebuild and all of that stuff will come out and I want to be prepared to put it back so that it works.

If I don't study some - it will be broke.

[reible]

see:
https://forum.shopsmith.com/viewtopic.php?t=3635

[dusty]

Thank you-- all of you. I believe I have read all of those before (they seemed familiar) but the important parts sure did not sink in.

I even see where I reported having moved the belt but I sure don't remember that. I thought maybe it was during that time when I was so thoroughly drugged but, after checking dates, I know it wasn't.

Well, mine is centered 2 and 2 and that is the way I will put it back when I do the rebuild.

[billmayo]

I believe the removable Drive Sleeve pulley with the set screw has the Poly-V belt starting 2 grooves from the front and the later one piece Drive Sleeve pulley/shaft Poly-V belt placement starting 3 grooves from the front. This is where I start.

If you look straight down the side of the Poly-V belt from the top of the headstock and slowly turn the quill shaft toward the front (same as normal rotation), I can see if the belt budges out on either side (only on one side) as it approaches the idler sheave pulley. This is very noticable to me as I always look for this belt budge when installing a Poly-V belt. To start, I tighten the setscrew in the eccentric bushing with the eccentric bushing and idler shaft bearing are even with the back of the headstock housing and againest the washer and screw above the eccentric bushing. I do not tighten the bolt that secures the eccentric bushing. I turn the eccentric bushing enough only to take the loosness (approx. 3/8"-1/2" deflection) from the belt, not to set the belt tension. I move/tap (rubber hammer) the idler shaft inward until the budge goes away while turning the quill. If the end of the eccentric bushing/idler shaft bearing is more than one pulley groove wide into the headstock, I start over again with the Poly-V belt 3 grooves on the Drive Sleeve pulley from the front. If the budge increases doing the above, then I go the other way. This may only work with a new or a good used belt as I do this task automatically without thinking when repairing/rebuilding any headstock. Then set the belt tension and tighten the eccentric bushing bolt.