Un-Rotaxing valves project

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bort
6 valves
6 valves
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Un-Rotaxing valves project

Post by bort »

After a lot of thought and research, I've decided to have some work done to the Rotax valves on my tuba. My rotax valves are currently at Martin Wilk's shop in Indiana, awaiting his magic.

As a bit of history, the general consensus about Rotax valves is that don't really do what they say -- instead of maintaining 100% geometric volume through the valves, they actually just constrict the airflow differently than normal rotary valves (or something close to that). I'm not exactly clear about this, and frankly this was never a problem with my tuba -- it's as open and free-blowing as any tuba I've played, piston or rotary. Frankly, it's not at all like most rotary tubas, and there is NO real adjustment needed by the player to compensate for additional resistance or stuffiness in the low range.

The problem, though, is the mass of the valves. They are heavy and not nearly as fast as I would like. Because of the way the Rotax valves are designed, they have more metal (mass) and more surface area (drag) than normal rotary valves. I'll post a few photos later, but essentially the Rotax valve is like a "full circle" of metal around its circumference, instead of the "open scoop" shape of normal rotors. I'm sure there's probably a bit more to it than that, but that's the main idea.

Martin (and others) have recommended doing some surgery to my valves, to carefully cut the "extra webs" from each of the Rotax ports in the valves, thereby making it essentially like a "normal" rotary valve, with the normal "scoop" shape. End result will physically have less mass to it, and will cover less surface area. Possibly even some benefits to response...with the cumulative effects of changing all 5 valves...?

I'm very curious to see how it turns out! I don't think it will end up WORSE, but I am curious how much of an impact there will be. Anything will help, and if this is only Round 1 of modifications... then hey, I had to start somewhere!

It'll be a few weeks until I get the valves back from Martin and can pop them back in, so it'll be a little while until I post an update. In the meantime, I have a tuba with no rotors. :tuba:
Last edited by bort on Wed Mar 28, 2018 5:26 pm, edited 1 time in total.
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bort
6 valves
6 valves
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Re: Un-Rotaxing project valves

Post by bort »

For everyone else, Joe means either "I told you do" or "I've been telling you so." Definitely appreciate your help, Joe... will send you a message...
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bort
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Re: Un-Rotaxing valves project

Post by bort »

Quick update -- valves are finished and are on their way back to me. Should be able to report some preliminary results in a few days. :tuba:
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bort
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Re: Un-Rotaxing valves project

Post by bort »

Disclaimer: I forgot to take before pictures... and also forgot to take after pictures. I also forgot to weigh the valves before/after, but they did seem a bit lighter.

Valves arrived this morning from Martin! The valves arrived shiny, clean, and the extra mass has been trimmed from around the ports. These now look just like regular rotary valves.

It didn't take long to re-install the valves, after a minor snafu of misaligning them by 90 degrees... (ascending valves are fun for about 4 seconds :roll:). But, that was a quick fix, and I was up and running very quickly afterwards.

A few initial impressions about the modified valves:
1) Valve action is greatly improved -- everything works much faster and lighter, a huge improvement. Wow.
2) Response seems to have improved, especially in the low range. This was NOT an issue before... but it got better. Everything REALLY cooks now. And it doesn't seem like it was just because the valves are snappier and they get out of the way faster... it actually seems like the airflow is better, and works to my advantage better.

With my Thein RCC, the low register is HUGE, and all around, the sound is fatter than I remember. With my New Geib, the response is really crisp and clear throughout the range (but the low end takes a little more finesse due to the smaller throat). Didn't get a chance to try the RT-88.

Seems like mission accomplished to me. It wasn't super expensive, and Martin turned these around in under 2 weeks -- many thanks to him for this work!

I'll post a follow-up in a few weeks after the placebo and honeymoon effects have worn off. :tuba:
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bort
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Re: Un-Rotaxing valves project

Post by bort »

bloke wrote:
1) Valve action is greatly improved -- everything works much faster and lighter, a huge improvement. Wow.
I'm shocked. :shock: :wink:
I know, right?

I actually wasn't expecting too much, but it's quite a noticeable difference. REALLY wish I had weighed these before/after, but I forgot.

Next up, fix the jacked-up (cobbled together) 5th valve linkage, and install a proper thumb lever. I already had something else fabricated instead of the small thumb rest (which was never in the correct position)... it gets the job done, but it's just a homemade piece of sheet metal, shaped like a paddle. :roll:
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binlove
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Re: Un-Rotaxing valves project

Post by binlove »

Bort, how's this coming? Still enjoying the modified valves?
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bort
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Re: Un-Rotaxing valves project

Post by bort »

binlove wrote:Bort, how's this coming? Still enjoying the modified valves?
Thanks for asking -- it's been a few weeks, and I haven't looked back. The valve action is faster and lighter (which was the primary goal), and as a side benefit, the airflow is more open and notes seem to slot/center a little better (especially in the lower range). I was actually considering some far more extreme measures for the tuba, but Martin talked me down and suggested we try this first. I'm glad we went this route, because it seems to be working out very well... and for a fraction of the price of the options. In my mind, it's made a great tuba just a little bit better. Maybe not to the audience's ears... but to me as a player, it's a bit easier to play.

It was kind of fun to fully disassemble my valves to take them out/replace them... the build quality of this tuba is outstanding. Also fun to see all of the shop markings (EVERY piece has "02" stamped on it, which is the last two digits of the serial number... as well as seeing a dot-pattern to identify which valve it is [1, 2, 3, 4, or 5 dots]).

This made me wonder as well, what kind of effect this might have on just the 5th valve of a piston Willson 3050? If I had one, I would certainly try it!

Mouthpieces... the RT-88 worked very well, but the rim was too large for me. The New Geib sounded great, but just didn't work out for me (too small). The Thein RCC has been my go-to ever since I bought it, and that hasn't changed. I may actually get a second RCC with a thinner rim... otherwise, I think I'm done with mouthpiece shopping for a good while.
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