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cuemaker
08-08-2011, 04:34 PM
http://i201.photobucket.com/albums/aa129/xringx/DSCF0031-1.jpg


I would like to keep the lathe in the pic on the bench you see. The issue is that I get bad vibrations that show up when turning at speed. I didnt have these issue on a much heavier bench, but dont want to use that bench as its my rolling work/welding bench. Plus its too high.

How to stiffen the table up? I will put good feet on the bench, but I was also considering welding up an exoskeleton and then bolting it on.

Other thoughts?

Hal
08-08-2011, 05:28 PM
You might try mounting the motor on rubber pads.

Hal

firbikrhd1
08-08-2011, 05:35 PM
From the look of your set up you could pretty easily have the motor remotely mounted and use an overhead belt drive. That would completely isolate the lathe from motor vibrations.

winchman
08-08-2011, 05:54 PM
A lot of the vibration in my lathe went away when I got a segmented drive belt.

Dr Stan
08-08-2011, 06:20 PM
I'd start by checking parallelism between the cones and the motor and for any loose connectors.. Then I'd check the feet of the bench to make sure they are all in contact with the floor.

topct
08-08-2011, 06:24 PM
The table looks stiff enough. I'd look for a way to increase it's mass.

rohart
08-08-2011, 08:06 PM
Your belt system is not very clear from the photo, but if you have a V-belt drive from the motor and a flat belt after that I would suspect the V-belt.

A V-belt is in tension, and the tension can vary as the different widths of a bad belt climb to different diameters in the V of the pulley. This can twist any motor mount and cause vibration. A flat belt just pulls on one side, with slack on the other. The best way to defeat a bad V-belt is to go to twin V-belts.

Alternatively, you may have genuine out of balance. Try moving a heavy workpiece to different positions in your 4-jaw and seeing what happens.

You may get away with just damping the vibration with some rubber here and there - under the table legs, for instance.

tornitore45
08-08-2011, 08:19 PM
Replace feet with wider pad, ideally 1 2x4 on one side and 2 wide adjustable on the other. Wide pads have more shear damping friction.
Make a false bottom box and put two bags of sand in it.
Tighten all screw or weld the seams.

cuemaker
08-08-2011, 08:19 PM
Tension system...

On the back of the up right is a steel plate on hinges. The weight of the motor provides the tension. I am using a adj that has some v to it (browning).

I will start with good feet and rubber between the motor and the steel plate as a start.

Robin R
08-08-2011, 08:45 PM
It looks like there is a void between the tops of the drawers and the top, turn the bench upside down and fill that with concrete. You could also box in most of the distance between the bottom shelf and the bottoms of the legs and fill that with concrete as well.

laddy
08-08-2011, 08:49 PM
Is that an old Sheldon Lathe??? Nice lathe! Fred

cuemaker
08-08-2011, 09:19 PM
Is that an old Sheldon Lathe??? Nice lathe! Fred

It is an old Sheldon.. I picked up for like $150 a few years ago.. She runs very well, bearing looked brand new.. but cosmetically she is a beast.. missing things. I have hodgepodged her back together some, but need to take time and do it right.

In fact, you can see the tail end of a pretty SB on the other bench.. I sold that one and kept the Sheldon....

RussZHC
08-08-2011, 09:35 PM
Try and isolate the motor as much as possible (rubber biscuits etc.), you may be "stuck" given the way the motor is attached (unless you want to go to the hassle of a quite different mounting).
Any time you can add cross bracing front to rear or side to side, if more stiffness is really what you are after.

Not sure what its worth, but I have heard it can be an issue if you rely on the weight of the motor to tension a belt. Just saying...though I have seen such a system on a table saw begin to vibrate and the more it did the larger the oscillations of the motor mount became...

For what it is worth, one early Sheldon owner to another ;) , I converted mine from a horizontal drive to a cross between what your overhead is and what SB did with some of their models. I simply was forced to do this because of room, so a fair bit of thought and aggravation went into the final version.

The motor is low, mounted to a plate with rubber mounts, and this plate pivots on it's mount which are fastened on an edge of a 2x4. These 2x4 on edge make up the wood part of my top. On one accessible corner of this plate I put an oblong hole so a bolt could pass through onto which I put a series of nuts and washers. This allows me to tension the "V" belt (running to the large outer countershaft pulley).

I used the stock "H" from the horizontal drive and mounted it on top of an inverted "L" (mirror and upside down actually) and another pivot point at the base of the "L" (separate from the shaft of the motor mount; the original plan had been to do it all in one, just did not work out that way). This pivot point allows me to adjust tension of the belt between countershaft and spindle pulley, but in practical terms it also slightly moves relative to the motor mount and so slightly changes the tension on that drive belt too.

All of the pivot points are isolated from the lathe proper in that the lathe is on a 5/8" plate on top of the on edge 2x4s. The only thing really connecting the countershaft to the lathe is the multi V belt, the only thing connecting the motor to the countershaft is segmented V belt (not link belt).

To give credit where its due, all I really have tried to do is take what Forrest Addy suggested in terms of isolation between pieces that could set up vibration...forget exactly where on here but it was a discussion of vibrations "telegraphing" to the surface of the work, and included discussion of rubber mounting, various belts (IIRC including what a seam/joint could do; FYI I installed both belts as one piece), motors of different phase requirements etc.
It is not to say similar issues will not crop up, its early days yet and I am working on a better finish to turnings but hey, I figure I have less than about 6 linear feet of turning under my belt...

Don't give up on it, Russ :D