Vibration after adding ballast

[Jim Kountz]

So I thought Id add some weight to the lathe today and bought 6 60lb bags of concrete. I put a 2x12 across the leg set and piled the bags on three across, two high spaced evenly. I then checked the level of the lathe in every direction. ROCK SOLID! I thought this is going to be great.......Until I turned the lathe on. Im getting a $^#*&% vibration that was not there before. I had a small square on the ways and it started moving around. Didnt have a nickel in my pocket at the time so I used a washer. It would stand up but start walking. I never had any vibration at all before I did this, did I do something stupid here??

[Mike Lipke]

A phrase heard in the operating room, that may apply here:
"The enemy of good, is better"

In the shop:
"NEVER, never, make the last cut"

Or'
"Don't try to improve what is working pretty darn good"

[Gary Herrmann]

Jim, what kind of lathe? Are you using the factory feet?

First guess is that despite spacing the bags evenly, the weight isn't evenly distributed on the board. If its a 2x12 from the borg, I'll bet it isn't flat and square. Even a little bit of twist in the board would cause it to vibrate, if it isn't attached to the lathe. Is it?

Maybe think about bolting the board to the lathe, or making a ballast box. I made mine of 3/4 ply and filled it with 5 bags of sand. Concrete in the bag can get wet - so that side could be heavier.

Sorry to say, but I'm seeing a bit of flat work in your future.

[Steve Schlumpf]

Jim - I have to wonder about the 2x12 with all that weight on it. Would have to think that it sags a little and could possibly be vulnerable to vibration. Suggest using two 2x4s run under the 2x12 for support. Screw the 2x12 to the 2x4s to help firm everything up - then place the concrete bags on the platform.

The ballast box I have on my lathe was constructed to be rock solid even before any concrete was added. Can you say 'Over-Engineered'? But it does make a difference!

I am sure you made sure all the hardware was torqued down, headstock/tailstock secured, etc. Best of luck figuring out what is going on!

[Jeff Nicol]

Jim, With that much weight anything could have changed a little bit and could cause the vibration. Even if the ways are level, there could be another place that changed position and is causing the problem. Also when the weight is applied it changes the center of gravity on the lathe so the bottom is heavier than the top so any movement in the headstock is staying up in the ways and not transfering to the floor or the bags of concrete. The trouble with bags of concrete is that they basicly become solid with the potland cement in the bags, as sand will shift around and if it is all in one big box instead of 6 different bags, it will absorb the vibration better. I added 300lbs of sand to my 12x36 lathe and had to add some bracing back down from the bed to the bottom under the sand box to eliminate the vibration.

So check it all out maybe you will see where the problem is!

Have fun!
Jeff

[Jeff Nicol]

The box is good and more is better in this case! You are most likely on the right track Steve!

Jim I say by 2 or 3 in the morning you will be back in business !!

Jeff

[Bob Vallaster]

2x12 on flat, bearing 360# sounds like a loaded spring.

Rx: beam or torsion box.

BobV

[patricia stein]

hi jim i put 480pounds on a 2by 12 but i put 4by4 post under center for sag issue vibration back to normal

[Steve Schlumpf]

Patricia - Thanks, you reminded me that I did the same thing. Have a small section of 4x4 used as a column for support under the center of the ballast box. Forgot all about it until you mentioned it. Don't see it every day......

[Bill Bolen]

The unsecured 2X12 is the most likely candidate providing unwanted vibration. My 1442 has a ballast box that issecure to the lathe,,,no vibes unless it is a big out of balance piece...Bill..

[Jim Kountz]

Thanks everyone, tomorrow I will try all the suggestions and try to isolate the problem. Sounds like a ballast box is in my future.

[Gary Herrmann]

Forgot to mention. My ballast box is supported by a 2x4 mortise and tenon joined frame. The tenons are 2x4s on edge.

[Jim Koepke]

Resonance, the unanticipated fly in the mechanical ointment.

jim

[Richard Madison]

Jim,
You have created a spring-mass system whose resonant frequency is close to some frequency that the lathe generates. Suggest you remove the two center bags from your 2x12 and try that. Then if sufficient clearance available, you could restack the two bags at the ends so they would be 3 deep.

[Wilbur Pan]

Stiffening the 2x12 is definitely a good thing to do. I'd like to suggest another reason for the vibration -- by putting those bags of cement down, you've shifted the center of gravity of your lathe away from the lathe bed, which makes it easier to move the bed of the lathe. Here are some diagrams to show what I'm talking about.

The first picture is an end on view of your lathe before adding any ballast. The majority of the mass of the lathe is in the bed and the motor, so the center of gravity will be up near the bed of the lathe. Any vibration will need to move the center of gravity around, so it's going to take a fair amount of force to cause a vibration.

If you added 360 lbs. of ballast as you describe, and if the place for the board is low to the ground, which is the typical location that is provided on the legs for a board, you get the situation in the second picture. Putting 360 lbs. is going to move the center of gravity downward, away from the bed of the lathe. You didn't mention what kind of lathe you have, but a Jet 1642 is about 440 lbs., and the Powermatic 3520B is 680 lbs, so adding 360 lbs is adding a significant percentage of weight to your lathe. Since the center of gravity is now away from the lathe bed, vibration will be easier to induce.

A better location for ballast is as close to the lathe bed as possible, which is the third picture. This keeps the center of gravity up towards the lathe bed. One of the most stable lathes I have seen was a Nova 1624-44, which is not a lathe that is known for being rock solid in the same vein as a 3520B or a Robust. If you've seen a picture of one, you'll know that it has little spindly legs, and weighs just 250 lbs. This particular Nova had a board placed just under the lathe bed with some bags of sand on it, like in my third picture, and didn't vibrate even with a large out of round blank on it. I believe it was the location of the added weight that contributed to its stability.

[al basham]

Jim,
I've experienced vibration especially in odd shaped pieces. I heard about an idea that Jerry Glaser presented at the Davis, Ca. symposium. He was reported to have read this in an early Dutch turning book.
At the time I had a General lathe, and didn't want to bolt it to the floor. I took Jerry's idea and applied it to my lathe. The rules as I remember were the the weight skould be 10% of the lathe weight and should be suspended about 24" above the bed. I know this sounds strange but you'll understand when you see the photos.
If you have any questions please contact me.
Thanks .... AlBasham
I used 1 1/4" CRS for the support, 5,8" diameter alloy threaded stock and discarded lifting weights.

[Richard Madison]

So Jim, it is tomorrow. Can't wait to hear your results.

[Allen Neighbors]

Al Basham's solution is the best of the best. Above the lathe headstock is the best position for the stabilizer. A bucket of sand on a pipe will work, also, but Al's looks much better. :D

[Jim Kountz]

Well I got it figured out, Im a dummy thats what was wrong. When I got my Woodcut Bowl Saver and started using it it was really the first time I used the lower RPM range on the lathe. I hadnt had the belt over on those pulleys since I first got the lathe really. So when I inspected the belt and pulleys I noticed all kinds of gunk all over the pulleys on the low RPM side. I guess it was a combination of left over cosmoline and shavings/dust from all the turning Ive been doing on the other set of pulleys. So I just cleaned everything up and now its sounds like this....MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM

And I was able to keep my balast, I did move everything to the ends of the shelf and put a support under the middle. It made a huge difference today when I roughed out another 15" maple blank for coring.

Ahh Sweet success!!

Thanks to everyone who offered help with this I sure appreciate it!!

Jim

[Kim Ford]

I did some research on this when I was going to build a bowl lathe.

The vibration from a lathe transmits to the spindle which is directly connected to the out of balance wood blank which is creating the vibration, mass quiets vibration so the closer the mass can be directly connected to the spindle the less the vibration.

I know that sounds simple, and it is, but it works.

[Jim Kountz]

I did some research on this when I was going to build a bowl lathe.

The vibration from a lathe transmits to the spindle which is directly connected to the out of balance wood blank which is creating the vibration, mass quiets vibration so the closer the mass can be directly connected to the spindle the less the vibration.

I know that sounds simple, and it is, but it works.

Makes sense, Im just glad I lost the vibration. Oh yeah when I was getting the vibration that was with NOTHING on the lathe so it wouldnt have been from an out of round blank. Thats what was so upsetting about it, the fact that I was getting a vibration with no wood on at all. But its all taken care of now and Im off and running. Just cored two more blanks this afternoon!!

[Bill Bolen]

Just curious Jim...what was your final fix?..Bill..

[Bob Bergstrom]

Was in a guy's shop last Saturday. He showed me a vibration in his drill press table. I could visibly see it shake. He had a rod bolted on the back of the head stock with a weight attached. By sliding the weight backward or forward he could make the vibration appear or disappear. His occupation was an acoustical engineer for Caterpillar In Peoria Illinois. I don't know how he determined where it should be located, but I guess thats what they pay him for. It all about harmonics and imbalances