The only way I see is that you need to make a frame that it would spin in, you would need end plates on the drum to hold each end centrally and a post at each end to support it and I would turn the drum by hand, the post needs bearings at each end for the spin, looking at the photo then it looks like the high point to the low point is over an inch but under two inches, that could have been reduced if there were more segments in each ring, either way that is too much to cut away in one pass, as the rotation would be slow then each pass could not have a deeper cut than a 1/4 inch and a 1/4 inch along the arch, that could be OK if the rotation was slow at the start the cut would be stop/start until it was round, I would make an arch that was attached to the top of each post and the arch would have to be the shape you want the router to cut the drum to and you need to be able to lower the arch at each end to get a deeper cut, the router would travel on a sled along the arch. one rotation at a time, do one full rotation before the router sled moved along the arch to do the next circular cut, I would use a planing cutter with a flat bottom and the bottom of the cutter will have to be held square with the cut, as the difference between the high and the low points is so much then you will have to do many rotations to get the drum finished, I would do the final pass as only an 1/8th of an inch, this can be done but you will need a big Router lathe, see my Router Lathe post for what the beam and posts needs to look like, I am making mine so well as I will keep it for years and years and use it for many items but you lathe does have to be strong to support the arch/sled but I would only make it as well as you need it to be so how many drums will you make? what you need to build is not that different to what I am making, my lathe has a flat top, yours will have a pair of arched top rails that the Router Sled will move along. best of luck. N http://www.routerforums.com/jigs-fix...ter-lathe.html
G'day Neville. You are the one who is entirely to blame for me joining this forum. When I did my searches on Mr. Google, your thread on your current lathe building project came up. Have you not received the metal parts yet that you are waiting for? Lots of us are awaiting the final completion of your lathe.
I'm surprised that a man of your considerable talent does not weld. It's actually pretty easy with oxy-acetylene, and you can even do stainless steel with gas. I know that most people think you need to use tig, but gas works especially if you have one of the Dillon Mk.111 welders.
Now, as far as the number of pieces in each segment goes, I do realize that more pieces in each layer would work much better. I will work out the lengths for 12 pieces per layer to see what the difference would be. It currently uses just eight per layer.
That would bump the glue-up to 540 pieces...not sure that I want to do that.
Now, as far as the actual shape of the router lathe goes, I already made up a laminated piece to the shape that I wanted. I would need to make up two wider pieces with exactly the same shape in order to let the router be guided to the proper profile.
I think I can solve the tipping problem by using arborite to keep the router on an even keel. Actually make a piece which would fit under the router base and on to the top of the two laminated sections and stick a narrow strip of arboreta under the ends.
I have built telescopes in the past, and we use a similar system to allow the 'scopes to pivot on. Almost no drag doing that, so it should make for an easy slide. I'll give that some more thought to improve upon the basic idea before I start on the actual construction.
I think it is entirely unfair that you have such gorgeous weather down your way while we are just now getting to be buried in our usual winter snow.
Thank you for your insight Neville, I'm sure we will be conversing much more in the future.