Steve,
in case you are not familiar with my lathe. An Oliver 20C is designed to handle very large turnings and was designed by the Oliver woodworking machine company since 1902 for this specific reason. you are capable of turning with very high precision because it is designed as a pattern lathe with a 2 feed carriage system with a stamped measuring indicator on the carriage and the bed. An Oliver 20C has 24 inches over the bed-ways 22" over the carriage. The bed lengths varied depending on the customers selection and you could even order the lathe without the cast iron bed, for those that preferred a timber designed bed-way, but you lost the option of the carriage by doing so. In David's case, the carriage will not be underneath the material as it will be positioned on the end of the log face and will be fed into the face for a perfect circumference- that being mounted on a 20" face plate. This is the procedure that I would use in this case which is pretty straight forward. I can turn on the outboard side as well if need be, my only limitation is the floor the Oliver rests on ~ currently that is 64" in diameter, due to the floor. If I had a pit for the outside turning it is possible to do 96" but that is as far as I am willing to go. There is a separate bed-way that is used for the outside with a 2 step carriage , I have not yet found the need to even use it as the lathe can handle most of the turnings. In David's case there is a lot of drying time involved with this project more than anything else and you can't rush this job. I am not a big fan of creating a turning out of a solid piece of wood this large in diameter because of cracking in the vertical grain that could arise ~ . If he plans on doing this out of solid wood then the diameter of the material should be no less than 28" to start, then turned down. It is very possible to get all of his drum shells from just one log, depending on the diameters. I also would not want to turn the drum wall thickness less than a 1/2" in diameter on the 22" bass floor shell, the others could probably go a little less but no more than 3/8" to play it safe. this is a doable project in my mind and don't see any problem other than the wood curing and the wall thickness. This is just my opinion Steve, others may feel different about it ~ but keep in mind you can only do what the equipment you have will allow you to do ~ and it is not in the best interest of of your machinery or your safety to push the envelope beyond it's limitations. I know mine and respect my equipment and it's limitations.
Happy Turning
Regards,
Brian
Brian