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Something I didn't know about rotary valves
Posted: Sun Jan 19, 2020 6:43 am
by timothy42b
I have an old and crudely made Russian rotary valve trumpet. It's more of a wall hanger than a player. For no particularly good reason I decided to lube linkages and slides last night.
These valves have a lot of pivots in the linkages. Probably 6 each. If I tapped out the valves like on the trombone, disassembly would be a pain. The main connection is a knurled thumb screw though.
But then the weird part. Taking off the end cap, I noticed the bottom plate was loose. Sure enough, a fingernail gets it off and you can lube directly into the valve without disassembling. If that's on purpose it seems like a good idea.
Re: Something I didn't know about rotary valves
Posted: Sun Jan 19, 2020 7:16 am
by harrisonreed
Usually it takes more to get the plate off than just a finger nail, but that's the way to do semi or annual maintenance on them, yup.
Re: Something I didn't know about rotary valves
Posted: Sun Jan 19, 2020 1:19 pm
by brassmedic
timothy42b wrote: ↑Sun Jan 19, 2020 6:43 am
I have an old and crudely made Russian rotary valve trumpet. It's more of a wall hanger than a player. For no particularly good reason I decided to lube linkages and slides last night.
These valves have a lot of pivots in the linkages. Probably 6 each. If I tapped out the valves like on the trombone, disassembly would be a pain. The main connection is a knurled thumb screw though.
But then the weird part. Taking off the end cap, I noticed the bottom plate was loose. Sure enough, a fingernail gets it off and you can lube directlyer into the valve without disassembling. If that's on purpose it seems like a good idea.
Are you talking about the outer bearing? That definitely should not be loose. It needs to be repaired.
Re: Something I didn't know about rotary valves
Posted: Sun Jan 19, 2020 1:34 pm
by BGuttman
brassmedic wrote: ↑Sun Jan 19, 2020 1:19 pm
timothy42b wrote: ↑Sun Jan 19, 2020 6:43 am
I have an old and crudely made Russian rotary valve trumpet. It's more of a wall hanger than a player. For no particularly good reason I decided to lube linkages and slides last night.
These valves have a lot of pivots in the linkages. Probably 6 each. If I tapped out the valves like on the trombone, disassembly would be a pain. The main connection is a knurled thumb screw though.
But then the weird part. Taking off the end cap, I noticed the bottom plate was loose. Sure enough, a fingernail gets it off and you can lube directlyer into the valve without disassembling. If that's on purpose it seems like a good idea.
Are you talking about the outer bearing? That definitely should not be loose. It needs to be repaired.
Given that it's a Russian made rotary trumpet I'm not surprised that it is loose. You may be able to compensate for the sloppy fit with heavy oil, but don't expect miracles.
Generally you need a mallet to pop the bearing plate. Depending on the design of the valve getting it back on properly can sometimes be a challenge.
Re: Something I didn't know about rotary valves
Posted: Sun Jan 19, 2020 4:30 pm
by brassmedic
If you are talking about this part of the valve, it should require a rawhide mallet tapped on the opposite end of the spindle to pop it out. If it is loose fitting and can be pulled off with your fingers, then it needs to be repaired. If it's that loose, the bearing is probably moving around when the valve is operated. That is not a design feature; it is a malfunction. Heavy oil won't fix it.
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Re: Something I didn't know about rotary valves
Posted: Sun Jan 19, 2020 7:41 pm
by timothy42b
Yes, the outer bearing.
All three are like that.
I'm guessing they didn't have the precision to do an interference fit like on a trombone, and set up this tapered bearing seat instead. I should post some photos of some of the crude fit and finish on this thing.
Re: Something I didn't know about rotary valves
Posted: Sun Jan 19, 2020 7:55 pm
by JohnL
Loose bearings allow the valve core to wobble. You end up with wear to the valve core and casing, which eventually leads to low compression.
Of course, if the whole thing is already loose...
Re: Something I didn't know about rotary valves
Posted: Sun Jan 19, 2020 10:12 pm
by brassmedic
timothy42b wrote: ↑Sun Jan 19, 2020 7:41 pm
Yes, the outer bearing.
All three are like that.
I'm guessing they didn't have the precision to do an interference fit like on a trombone, and set up this tapered bearing seat instead. I should post some photos of some of the crude fit and finish on this thing.
Yeah, let's see a photo. I would assume it was originally a press fit and it just wore out, but I did see Eastern European valves once where the bearing was held in a different way, so maybe not.