Flat belt pulley alignment?

sandiapaul · Dec 10, 2017

After many months of rebuilding I finally have everything together on my lathe and have a problem with my flat belt not aligning properly. The lathe is a Smart & Brown 1024. I added a new motor and made a new way to mount the motor. The original motor hung down from the plate the gearbox is mounted on. I mounted the motor on a plate that uses standoffs that mount to the late as seen in the pic. This is likely the source of my problems I realize. Perhaps the shafts are not parallel, or???

I can't get the belt to track in the middle of the pulleys. Worse it comes off at higher speeds. See the pic, motor is at the bottom, it drives a two speed gearbox at the top. I have lots of room on the motor shaft to move the pulley in and out, but that does not seem to help, best I can make it about what you see in the pic. About 3/16" of the belt is off the pulley.

If anyone can offer some advice on which way to move or shim my motor mount I sure would be grateful! Alternatively would another type of belt do better?(wishful thinking I know)

iwananew10K · Dec 10, 2017

motor shaft is pointing up in relation.
belt walks to side of least resistance.

Madis Reivik · Dec 10, 2017

Does at least one pulley have big radius profile ? Completely flat pulleys do not align flat belt properly.

sandiapaul · Dec 10, 2017

Both have quite a decent size crown, which I THOUGHT was going to work in my favor!

rj1939 · Dec 10, 2017

It needs to be shimmed, short belt is harder to keep tracking right, or so it seems

Ray Behner · Dec 10, 2017

I would assume your clutch box is nice and square to the world. That being said, use a straight edge from it's pulley to the motor pulley. It will speak volumes.
Hope you can get your head scrunched around in there.

Tyrone Shoelaces · Dec 10, 2017

Ray's right. First rule of lining up pulleys- straight edge off the pulley sides. That's assuming the pulleys have the same profile.

Regards Tyrone.

jhruska · Dec 10, 2017

Hmmm........
Mark the crowns with chalk and align to that.
John

billzweig · Dec 10, 2017

The pulleys must be parallel and in line - even a small tilt or misalignment will drive the belt to one side. Check by placing a straight edge on both pulley faces, centre-line. The straight edge must make a full contact with both. As well, it sometimes happens that the belt is faulty, for example stretched a bit on one side. Worth trying another belt.

IrbyJones · Dec 10, 2017

I agree withiwananew10K, the motor shaft is pointing up. You can almost see it in the motor plate relative to the plate below it. Just having 2 standoffs won't stabilize the motor shaft well. I'd suggest using 4 standoff/adjusting screws, or at least 2 on the outboard end of the motor plate (to right and left of the standoff in your photo). Then you can easily adjust the motor shaft to make the belt track.

Irby

sandiapaul · Dec 10, 2017

OK guys, thanks. One thing about this machine...whoever designed the motor and drive unit and its enclosure was a sadist, contortionist or both. There is almost no room to work in there so shimming will be an adventure. Madis was dead on, I was able to get a wedge under the plate my motor is mounted on and it tracks true now.

When I made the new motor mount I was careful to measure and locate everything so it was be in the right place. Obviously this didn't happen! I thought I would have more leeway with the crowned pulleys. I have helped belt up steam tractors to sawmills and they can be pretty far off from straight and parallel. But this is a different kettle of fish. As RJ1939 says the shortness is fighting me here. I did use a straight edge when setting it up before it went into the base and it looked good.

Again thanks, I'm on the right path now.

B-Mathews · Dec 10, 2017

iwananew10K said:
motor shaft is pointing up in relation.
belt walks to side of least resistance.

I see the same thing as well.

Tyrone Shoelaces · Dec 10, 2017

jhruska said:
Hmmm........
Mark the crowns with chalk and align to that.
John

The crowns can be in line when the faces of the pulleys aren't.

Regards Tyrone.

CarlBoyd · Dec 10, 2017

sandiapaul said:
Both have quite a decent size crown, which I THOUGHT was going to work in my favor!

You thought right. It is working in your favor.

CarlBoyd

sandiapaul · Dec 10, 2017

I DO have 4 standoffs, the others are out of the picture on the right and behind the one that is visible, and I can easily shim/adjust them, though frankly that was luck, not planned in really.

Thanks to you all I know what I need to do now. 18 months later and she is almost ready to go to work.

jhruska · Dec 10, 2017

Tyrone Shoelaces said:
The crowns can be in line when the faces of the pulleys aren't.

Regards Tyrone.

Yes.
The crown of each pulley wraps around the pulley diameter that is described within a plane. For such a short distance between pulleys the planes should be parallel and in line.
John

Mike C. · Dec 10, 2017

Can also use a string in place of a straight edge to line up the pulleys.

Tyrone Shoelaces · Dec 11, 2017

Mike C. said:
Can also use a string in place of a straight edge to line up the pulleys.

Yeah, a short length of string is ok, especially in a confined space were you may not be able to get a straight edge in.

Regards Tyrone.

sandiapaul · Dec 11, 2017

And indeed I can't get a straight edge in there, the string is a great idea!

TedinNorfolk · Dec 12, 2017

On my venerable Hind shaper,now rehomed with another member of PM,I put a 2hp motor about 10 ft above. About 3"pulley driving onto the large flywheel. With both machine and motor level,and a plumb line from cl pulley to cl f/w the belt rode perfectly. The rim of the f/w was straight so I put a crown on pulley.

Flat belt pulley alignment?

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