Rotary valve modification

[roweenie]

I've got a rotary valve that has its stop plate opposite of where I need it to be:





Is it possible to remove the top plate and turn it 180°, or do I need to drill and tap new holes, and plug the old ones, or is there a more efficient method I'm not seeing?

Thanks!

[roweenie]

Drilling and tapping new holes is easy...I know it will be easy for you.
There is no need to seal up the old holes, unless you don't like seeing them.

If you just can't stand the holes, you could screw in some very short pieces of properly threaded material with very nicely filed-flat tops and (not even solder, but) epoxy them in place. Of course, you would still be able to easily see them...

Sounds good - are you familiar with what thread it might be? I'm certain it will be metric - it's a Meinlschmidt valve, if that helps.....

[roweenie]

most common is M3 x .5

drill bit diameter: 2.5mm ...3/32" will work, if you don't have any metric drill bits

Excellent - thanks!

[roweenie]

An M3 screw is actually too large - maybe it's M2.5?

I'm pretty certain that the top plate is hard soldered on, so I'm going to try to avoid messing with that, unless all else fails.

I'm hoping it's not a bastard thread...

[roweenie]

Yes, you are right - I'll braze on a piece of round brass, 180° across - that'll probably be the easiest fix....

[Aglenntuba]

I THINK that top plate may be removable. I have definitely removed one before (also from Meinl), all I had to do was twist that textured edge. Note that it was pretty old. I definitely may have just busted what little solder was on it. But it slid right back into place and worked fine. Just my singular experience.

[pjv]

This is how Larry Minnick solved it for me. I think this was the other solution Bloke mentioned.(?)

[Matt Walters]

OTHERWISE, you MIGHT be able to (simply) leave the cork plate where it is, and braze an additional connection point on to the stop arm.

Would be my choice. Screw up a stop arm and a replacement is cheaper than a new valve.

[roweenie]

Thanks to everyone for all the great ideas. I decided to braze another screw holder onto the stop arm - easiest way to go.

The screw size for the stop plate is actually M2.6 × 0.45, information directly from Meinlschmidt....

[cambrook]

Stop plate Bloke, not the miniball

[PaulMaybery]

I looked carefully at the 5th valve rotot assembly on Blokes CC Buescher Helicon. His design and intuition is uncanny in dealing with levers and vectors to get a rotor to turn in the right direction. His way of finding the simple solution is tantamount to genius. Sorry, I did not mean to cause any embarrassment.

[roweenie]

Speaking of levers; how would one devise a lever that when you press it down, it would cause a rotary valve stop arm to be pulled upward? I'm thinking of something along the lines of a see-saw, with the fulcrum between the thumb lever and the connecting linkage, but there are space limitations with this set-up.

Just curious if it were possible...

[Matt Walters]

Speaking of levers; how would one devise a lever that when you press it down, it would cause a rotary valve stop arm to be pulled upward? I'm thinking of something along the lines of a see-saw, with the fulcrum between the thumb lever and the connecting linkage, but there are space limitations with this set-up.

Just curious if it were possible...

String linkage system makes it go in the opposite direction.

[oedipoes]

Speaking of levers; how would one devise a lever that when you press it down, it would cause a rotary valve stop arm to be pulled upward? I'm thinking of something along the lines of a see-saw, with the fulcrum between the thumb lever and the connecting linkage, but there are space limitations with this set-up.

Just curious if it were possible...

Not sure if I understood your request correctly, but the linkage to the Norwegian Star 5th valve pulls the rotor up, if that is the way to describe the movement: the linkage turns the rotor counterclockwise with that action.
A picture is worth a thousand words...

Norwegian Star.png

[roweenie]

.

[roweenie]

Because of the pivot of the linkage, you would think that making the valve go up is an easier task than making it move down

Maybe so, but I'm having a darned time figuring out how to do it.....

If the wing rotated down to open the valve, it would be a simple matter of connecting a rod directly to the thumb lever - push down, and the rod would push down the wing....

(Physics was never one of my better subjects..... )

[Matt Walters]

"LAST THINGS FIRST" is a reminder phrase I coined for myself decades ago. If you don't first take into consideration the last thing you will do, you run into troubles like this. Without that downward 1st valve loop, you would have had more room for the thumb lever. Now you need a double hinge linkage system. Look at a rotor valve lever system with hinge joints. Imagine that instead of the paddle folded down parallel with the #2 slide tubing, it was perpendicular so that it was pointing up and away from the tubing. If you moved the paddle away from the bell, it would pull the stop arm back towards the bell. This is what you need because you left no room to attach the linkage on the other side of the stop arm. You have a soldered in valve so you need access to screw and un-screw the linkage at the stop arm.
So, is there enough room under that 1st valve tubing to fit the saddle for the hinge tube that the spring wraps around? Then do you have room to go up to a thumb paddle and room to go down to the double hinge attach point? Pipe cleaners are great to see what will work. Attaching a minbal to the stop arm is the easy part.

If there is not enough room then..............you have to make some decisions.

[roweenie]

.

[roweenie]

Update - I decided to go the "easy" route, and just braze on another pivot point on the stop arm, 180° away from the original one:






The rod now functions as a "direct drive". Now, I need to adjust the thumb lever to fit my hand (it's already very close).

Thanks for all the suggestions!

[roweenie]

That all looks really great... (super, actually...)

...but did you find that there were any issues with intonation or response with only one cork plate screw?

I would imagine it would critically affect the sympathetic vibrations of select overtone series.....

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Thanks for your kind words, both bloke and elephant, and also thank you to Matt Walters for his assistance, both past and present (and hopefully future, too ). In fact, I learned a lot from the elephant's very informative thread (and P.M.s as well) that illustrated all the work he did to install that valve pictured above. Thank you for your generosity of time and knowledge.

..even the friggin' tubing...I had to make a super-tight out-of-plane (i.e. "spiraling") S-shaped tube - that had to "land" PRECISELY at a certain spot (not even .005" wiggle room). 

Wow - I know (first hand) how frustrating this can be. There are challenges, and then there are challenges.....

I had no intention of putting a 5th rotor on to my Buescher helicon (C), but was goaded into by my friend/employee. 
Someone complimented it here, but it was completely unplanned (which is NOT characteristic of me) and VERY hard to do...

Yes, indeed. I have learned a lot about tuba design and construction in the last few years, and now, whenever I hear someone say "slap a 5th valve on it" (of whom, I was, at one time one of their number), I just have to chuckle to myself. Trying to "reverse engineer" something onto an existing thing that wasn't designed for it can be VERY difficult. For example, putting in that 5th valve entailed moving the 5th branch, which entailed moving a stationery 4th valve branch, repositioning the MTS, and all the brace-work involved with all those things, NOT including the routing and construction of the 5th valve circuit, the design of the lever system, etc. and all the brace-work involved with that, yada, yada, yada....

On a similar note, several years ago, I belonged to a Model T Ford club, and I was in the process of rebuilding my first Model T motor. I noticed that there was one place inside the block where one of the connecting rods, when rotating, came within about .050 of the inside wall. I told one of the old timers that I was concerned about that, and his reply was simple; ".050 inside an engine block might just as well be a mile". That motor is still running strong today.....