Ballast?

[Bob Haverstock]

Hi folks,

Last month I purchased a Nova 1624, I really like the machine. Yesterday, I put a chunk of green hackberry between centers. It was about 8" x 9" x 14" long and fresh from the chain saw. I don't have a large band saw for trueing and squaring the ends of the blank, so I roughed the piece between centers. I started out with the belt on the second set of pulleys, that would be about 200 RPM. The lathe started to dance, so I stopped it and set the speed at the lowest range.

This got me to thinking about ballast. It was the out of balance condition combined with the spindle speed that caused the lathe to dance. There was a pretty hefty side load on the centers. It was the lathe's gyrations that caused me to lower the RPMs. Had that piece of hackberry been thrown out of the lathe, I might not be at the keyboard at this moment. If I had added a large amount of ballast to the lathe, I might not have been aware of just how out of balance the wood was and how close to injury I was.

Ideally, The hackberry should have been on a faceplate. The blank had no face that was perpendicular to the centerline of the turning to be, so it was put between centers to establish the centerline.

I will be a while before I add ballast to the Nova.

Bob Haverstock

[Mike Minto]

I will be a while before I add ballast to the Nova.

Bob Haverstock


Bob, why is that? You now have empirical evidence of what kind of blank will make the lathe wobble - wouldn't that prompt you to add ballast now, and pre-empt any further problem with your lathe walking? I had a 1624-44, and even with the cast iron leg set, found it needed ballasting - and even more so with the original legset, regardless of how 'stable' Teknatool says it is. :)

[Bob Haverstock]

Bob, why is that? You now have empirical evidence of what kind of blank will make the lathe wobble - wouldn't that prompt you to add ballast now, and pre-empt any further problem with your lathe walking? I had a 1624-44, and even with the cast iron leg set, found it needed ballasting - and even more so with the original legset, regardless of how 'stable' Teknatool says it is. :)

Mike,

Thank you for your response. If my blanks are rotating in a balanced condition, there is very little vibration. The balance condition is preferred for safety. Many times, I have to rough turn to achieve better balance.

I'm thinking out loud here. The lathe's vibration alerts me to potentially dangerous conditions. Most of my larger turnings start out as green blanks, they are prone to being out of balance (soft and heavy). I could add hundreds of pounds of ballast to the machine. If I did so, and didn't pick up on the vibration, what would alert me just before the big BANG?

I'm 60 years old and have most of my body parts, for the most part they still function. About 25 years ago, I was hit in the head by a 10 pound spinning gear blank that was thrown out of a metal lathe. That rally rang my chimes, it is an experience that I don't want to replicate. I have time to anything that I really want to, I do not want to take time to go to ER if I can avoid it. I'm thinking that risk could be proportional to RPM when dealing with larger blanks.
Bob

[Scott Lux]

The lathe's vibration alerts me to potentially dangerous conditions.

I've wondered the same thing. If I add more weight to fix an out of balance condition am I not treating the symptom instead of the cause?

I've also wondered about the effect on the bearings. If the piece is severely out of balance I think I'm causing excessive wear on the lathe, even if I have enough ballast to prevent it dancing.

[Frank Van Atta]

I've wondered the same thing. If I add more weight to fix an out of balance condition am I not treating the symptom instead of the cause?

I've also wondered about the effect on the bearings. If the piece is severely out of balance I think I'm causing excessive wear on the lathe, even if I have enough ballast to prevent it dancing.

Amen and double amen.

[Mike Minto]

i'd say that if you are eliminating the vibration, there is no vibration to be concerned about...hence treating symptom and cause. but by all means, each person should do what they are most comfortable with. ;)

[Roger Bullock]

IMHO if I needed to chuck up a piece of wood that does not have a flat surface for a face plate and no band saw, I would make a flat area using a hammer and standard wood chisel. Once a piece is mounted between centers, the heavier side will usually rotate to the downward side unless you have the tailstock turned too tight. The more quickly it rotates downward the more out of balance the piece is. Sometimes this can be corrected by changing the center of the tailstock towards the heavier out of balance side. If not, you can take it off and fire up the chainsaw. You cannot always get the piece completely balanced this way but you can get closer.
Adding ballast might cut back on the vibration but I don't think it will eliminate it completely nor personally do I think it is a bad idea. I have ballast under my lathe. I sometimes turn small pendants off center and even something this light and small has vibration that I can feel, hear, and defiantly see.

[Paul Atkins]

I noticed that the lathe rocks back and forth when off balance, not up and down. More weight might change this but the better solution is to get a larger footprint or brace it to an unyielding wall. And yes, a piece that is off balance will still be off balance in a 50 lb. lathe and a 1200 lb. lathe, but the heavy lathe won't move as much. Now the question is, would the solid lathe throw a piece as far as the light weight one? (Not a challenge here)

[Wally Dickerman]

If I'm reading you right you are saying that my 700 lb. lathe is too heavy for safety because it doesn't vibrate as much as a smaller lathe. I don't buy that. If I mount a blank on the lathe and have to wonder if it's safe to turn, then I need to re-mount it with a more secure fastening.

I suppose that in the far distant past I've had a blank fly off the lathe, but if so, I can't remember it.

Wally

[Bob Haverstock]

Hi Wally,

Hopefully everything on your 700# lathe is beefier and hearier built than any part of my lathe. Personnally, anything that causes me to feel vibration, I need to investigate. I haven't benefit of your many years of experience. The 700 pound lathe won't save me from my mistakes and it may not tell me about them. But, it will show them to me just like any lathe will.

I caused my own oopsies, the machine did what I actually told it to do, not what I thought I told it.

Bob


If I'm reading you right you are saying that my 700 lb. lathe is too heavy for safety because it doesn't vibrate as much as a smaller lathe. I don't buy that. If I mount a blank on the lathe and have to wonder if it's safe to turn, then I need to re-mount it with a more secure fastening.

I suppose that in the far distant past I've had a blank fly off the lathe, but if so, I can't remember it.

Wally

[Wally Dickerman]

Hi Wally,

Hopefully everything on your 700# lathe is beefier and hearier built than any part of my lathe. Personnally, anything that causes me to feel vibration, I need to investigate. I haven't benefit of your many years of experience. The 700 pound lathe won't save me from my mistakes and it may not tell me about them. But, it will show them to me just like any lathe will.

I caused my own oopsies, the machine did what I actually told it to do, not what I thought I told it.

Bob

I really do recommend that you use some ballast to weight down your lathe. Makes for more comfortable and safer turning. When you put an unbalanced piece on the lathe you know that there will be vibration. That doesn't mean that it's unsafe to turn if it's safely secured. My 700 lb. Oneway will vibrate if the speed is too high with an unbalanced blank. One huge advantage to variable speed is that I can slow it down until the vibration is manageable until I can turn the piece into balance. If you use belts to change speeds, put it on the lowest setting and go from there. If the lathe has a slowest speed that's 500 or 600 rpm, as some are, then the blank has to be balanced off the lathe.

On a lightweight lathe a blank that's turned round can still vibrate under certain conditions. A blank that's dense heartwood on one side and sapwood on the other for example. A heavier, or weighted lathe will help to eliminate that. (I've had lathes that wanted to walk out the door with an unbalanced blank)

I recommend sand instead of something solid for ballast. Takes care of vibration much better.

Wally

[Steve Harder]

Bob - I also try to always start with a well balanced blank. But I have found that adding ballast to my 1624 has cut down the number of times I have to remove, trim, and remount a piece that is just slightly out of balance. It usually doesn't take too long to trim off the most out of round portion of a blank and smooth things out. I have a ballast box suspended just below the upper attach point for the legs.

[Jake Helmboldt]

I think the point that Bob is trying to make is that just because you dampen the movement of the lathe, you haven't eliminated the stress and forces being applied by the out of balance blank. That inertia will be applied or transfered somewhere, and when pushed to extremes the weak link will fail.

So I think Bob's point is that by adding a lot of ballast may potentially hide how badly out of balance a blank is, potentially resulting in something else failing (spur drive, worm screw, face plate screws, etc) without being as aware of the potential for it to occur (until it hits you in the grill).

That said, Bob I think a modest amount of ballast is good to simply dampen vibration and keep a light lathe from walking around. I think the problem is when people try to make their middleweight lathe into a 3520 or a Oneway by loading it down with as much ballast as possible.

Erring on the side of caution never hurts when you have the potential to eat a bowl blank.

[Bob Borzelleri]

Interesting thoughts. My take is that there are out of balance conditions and there are out of balance conditions.

If the blank is really out of balance, ballast might not do much other than make it appear a bit more manageable and could give a false sense of security, perhaps.

Maybe the notion of added ballast (which I happen to think is not a bad idea), is a good idea for those times where a blank is out of balance but not waaayyyy out of balance.

I doubt that I would be interested in a 700 lb. lathe if the primary benefit was the ability to turn wobblers. I'd rather find alternative ways of reducing the out of balance issues with a blank.

Oh, Jake already said it.