Referring specifically to the internal moving cylindrical parts of the valve, how is the valve made generally?
I imagine that a brass blank is put on a lathe and the valve is then cut to shape before the channels are drilled into the sides. Even more specifically is the blank cut as a single piece (and a lot of brass is lost in the process) or is the wider valve body and the spindle cut separately in order to save material, and then somehow married and fused together?
Interesting question -- I've always believed it to be one piece, similar to how a one-piece mouthpiece is lathed from a single block of metal. Just my guess, since I've never hear of problems with the spindles coming off of the valves (or anything like that).
Also, I've always figured that any of the removed metal isn't really "waste" (like trash), because it can be recycled and melted down into usable metal again. I mean, you would certainly want to minimize it, but it's not a total loss.
Read the description (and see a picture) of the Kanstul lightweight rotor construction here - http://www.hornguys.com/basstbn1662.php
I think most other rotors I've seen look like a single piece of milled brass. Here's a good example pic (in a tubenet post) - viewtopic.php?f=2&t=49037#p423149. (I'm not sure how the cutaway happens like that if it's not a single piece.)
Last edited by NCSUSousa on Wed Nov 12, 2014 12:13 pm, edited 1 time in total.
BBb Tuba with 4 Rotors -
TE-2110 (2009) + TE Rose
Mack 210 (2011) + Bruno Tilz NEA 310 M0
G. Schneider (Made in GDR, 1981?) + Conn Helleberg 120S
I earn my living as an Electrical Engineer - Designing Power systems for buildings
BBb Tuba with 4 Rotors -
TE-2110 (2009) + TE Rose
Mack 210 (2011) + Bruno Tilz NEA 310 M0
G. Schneider (Made in GDR, 1981?) + Conn Helleberg 120S
I earn my living as an Electrical Engineer - Designing Power systems for buildings
bloke wrote:I remember some 1970's Czech-made hollow valves. Those were very lightweight and worked very well. I don't know why they were discontinued.
Hey, I wonder if you could take a rotor like that and fill the hollow portion with a lightweight plastic, to make a composite rotor???
(So what was supposed to be the advantage of a composite rotor over a hollow one?? Obviously didn't turn out so well.)
Most rotors are solid, but Mr. Oberloh's appear to be hollow, like the old Amatis.
That seems like a lot more work, which may by why the hollow rotors are not found in newer instruments. I wonder if it also explains why student-model rotary tubas are now less expensive than piston models. For schools it seems like a false economy.
Modern rotors are typically machined from solid rod material on a four axis cnc milling machine. Some manufacturers have custom made milling machines set up for just making rotors. I have seen old cast rotor blanks that were made to be finished thru the old mechanical milling process but thats probably not very economical in this day and age with the time saving technology available.
