Fred Williamson's lathe

[iclark]

I guess I don't get it. Whenever I have turned something, my Shopsmith doesn't need weight added to it. I haven't experienced the machine moving around on it's own. Why is the added weight necessary?

I think that it was the guy doing the demo of turning square bowls (at the meeting a few months back) who told this anecdote:
he took a large piece of wood off his woodpile and carefully made it geometrically symmetric on his bandsaw. he then mounted on a heavy lathe between centers. when he turned it on (slow), the lathe immediately started swaying front and back so hard that he thought that it was going to fall over on him before he could turn it off. his post-incident analysis was that the wood had partially dried - but only on the upper side - the lower part of the log was laying down in the stack and was still very green. result was that geometric center and center of gravity were _very_ different. I suspect that he also happened to start at just the wrong slow speed and hit a resonance for the lathe oscillation.

in Fred's demo, he started with the crotch of a tree. he eye-balled it to decide where the bowl was hiding, sketched it out with chalk, then rough-trimmed it with a small electric chainsaw. he mounted it on a faceplate and roughed out the outer form at very slow speed. then he took it off the lathe, examined it, decided that there was a void that made it to dangerous to turn in a room full of people, and set it aside to take home to explore. he then repeated the process on a second hunk of wood that he had brought. the second one was solid and he did the full turning of that bark-edge bowl. neither hunk of wood was close to balanced but he used very slow speeds and paused several times to sharpen his tools. even so, the Oneway lathe tried to walk a bit early on when he was checking to see how fast he could turn it. basically, he dialed the speed up until he didn't like the vibration and then slowed it down until it quieted. he did this for the outside form and then again from the slow speed on the inside. one interesting thing that surprised me was that he finished turning the outside of the bowl before he started on the inside. on the inside, he did about an inch of depth at a time until he had that part of the bowl completely cut. only then did he move on to the next inch of depth. this really helped to reduce vibration and meant that he was always cutting on well-supported wood.

Woodcraft mounted an 8" grinder on the ways to the left of the head. it added weight and also made it easy to pause and sharpen the chisels.

Ivan

[iclark]

Short of making a lathe from concrete, how do you add weight to the shopsmith?
there is always the hanging storage cabinet.:) a pull-out shelf for a jointer would add some weight but might be hard on the back.

I think Bill Mayo mentioned that he had draped bags of concrete over the bench tubes when he was doing his large turnings.

Ivan

[JPG40504]

there is always the hanging storage cabinet.:) a pull-out shelf for a jointer would add some weight but might be hard on the back.

I think Bill Mayo mentioned that he had draped bags of concrete over the bench tubes when he was doing his large turnings.

Ivan

I did not know you could get concrete in bags. Concrete mix or cement perhaps?:D The cement bags are more dense.

[billmayo]

I did not know you could get concrete in bags. Concrete mix or cement perhaps?:D The cement bags are more dense.

We used 80 pd bags (sand, cement, concrete mix, etc.) (all that would fit on the bench tubes) that was available at the site. Since I did not put them on the bench tubes. I am not sure. The bags had some looseness in them so they were able to be somewhat thinner over each bench tube so the carriages would clear them. This was done a few years ago so my memory is not totally acountable for what we did. We winged it for solutions as we encounted problems. It took a couple days of testing before we were able to turn the 100+ posts. This was done on a bet as the home builder said that Shopsmith could not do 8' porch posts plus other bad comments and I was going to prove him wrong plus get some money. I used a Honda 2KW RV generator for power. I had already done some testing with my modified speed reducer headstock and 104" tubes before this so only had to solve the really bad vibration/flexing problems, extend the tubes to 122" and add a second carriage with a center support for all the tubes. It was a very fun project for me as "close counted".