Caring for Plastic Valve Guides

[davewerden]

In this and other venues I've seen more instances of people experiencing 1) broken valve guides or 2) sticking valves because of distorted valve guides. So I did a little video showing the proper handling to prevent this:

https://youtu.be/WtED43XGCb0

[ghmerrill]

Great video that can save people (especially "beginners" or, often, "students") some heartache in not messing up these valve guides and either having to replace them or (worse) take them to a service tech to get them replaced. I also take the time to determine visually where the guide channel is in the cylinder so I don't have to do the "keep rotating it around the circumference until you find it" approach. I've found that -- if not abused -- these plastic guides last for a surprisingly long time. Some years ago I replaced the (original! -- and hideously worn and clanking) brass guides on my 1924 Buescher Eb tuba with guides made (under the direction of Dan Schultz) from plastic "cheese head" screws -- of which I now have about 95 still left over -- and they don't seem to have worn noticeably in several years of playing.

[cassb]

Dave, my Jinbao euphonium is about 7 years old. With the valves installed, I can turn each piston slightly in the casing, a few millimeters each way. What is the tolerance for the guides supposed to be? I'm wondering if replacing the guides will make any difference.

One note about these Jinbao copies of the Yamaha horns (mine is from Mack Brass), the ports in the piston do not align exactly with the tubing in the horizontal direction, at least on the ones I can see. I wonder if the brand name horns do align every port and tube exactly (if the felts are correct, of course).

[ghmerrill]

So ... a couple of things:

"A few millmeters", to me, is a huge amount. I fact, I'm having trouble seeing how it could move that far and not be able to be just twirled 360 degrees in its casing. Certainly if you've played it a lot in 7 years, they need replacing. Yamaha guides will fit it just fine. Simple to replace.

Alignment ...

If the valves don't align properly, then you should align them. You probably don't want to do this yourself since it's a bit tricky and will likely require making a fairly crude measurement tools One of the first things I did when I got my Mack Brass euph (maybe 10 years ago?) was immediately replace: All the crappy water valve corks (with Valentine synthetic ones), and all (really cheesy and mostly falling apart) corks and felts on the valves -- making sure I got the valves aligned correctly in the process.

At this point I don't recall where I got the supplies from. But valve guides are really easy to get on the web. Likewise the water key corks (but you've got to measure the diameter and make sure you match that, at least closely enough).

As I recall, I posted on here about all this several years ago. But I haven't looked for that. If you search for my ID in the postings, you should be able to find those postings -- which will give you a lot more detail, even if you want to take the horn in to a tech and have it done.

[cassb]

Thanks, Gary. Maybe I misspoke... 'a few millimeters' is what it feels like when I rotate the piston, not the distance between the guide and the channel. It just feels looser than I think it should be, is all. I would like the piston to be as snug as can be and still freely move up and down. I have already replaced the felts and lined up the holes as best I could.

The misalignment I do not think is correctable. Can you take off your compensating 1st valve tuning slide and press down the 1st valve? Do the two piston holes line up perfectly with both tubes? On mine, the bottom one lines up but the top one is not -- a little bit offset clockwise. I think it's just because it's a knock-off horn and cost only $1000 instead of $7000+ for the Yamaha. ;-)

[davewerden]

Thanks, Gary. Maybe I misspoke... 'a few millimeters' is what it feels like when I rotate the piston, not the distance between the guide and the channel. It just feels looser than I think it should be, is all. I would like the piston to be as snug as can be and still freely move up and down. I have already replaced the felts and lined up the holes as best I could.

The misalignment I do not think is correctable. Can you take off your compensating 1st valve tuning slide and press down the 1st valve? Do the two piston holes line up perfectly with both tubes? On mine, the bottom one lines up but the top one is not -- a little bit offset clockwise. I think it's just because it's a knock-off horn and cost only $1000 instead of $7000+ for the Yamaha. ;-)

FWIW, on my Adams, the ports align perfectly to my naked eye. A small error won't make a good horn feel awful, but it does make some difference in response, tone, and maybe intonation.

As far as the guides, when you look through the open compensating 1st slide and rotate the piston, do you actually see misalignment? If not, then it's not a playability issue. But extra play can cause more valve noise, even with plastic guides.

For the "feel" test, try it at 3 or 4 points along the vertical range of the piston. That would make sure the sides of the groove are parallel and that the width is uniform. If not, it complicates the idea of replacing a guide to tighten the play. ALSO, stuff does build up in the grooves. The tighter the fit, the more chance of a piston hanging up unexpectedly.

[ghmerrill]

I have already replaced the felts and lined up the holes as best I could.

Yeah, but "as best I could" may mean that things are not aligned correctly. Alignment requires rather precise (and explicit -- not eyeballing) measurement. And it's often surprising how well a horn will play when out of alignment.

The misalignment I do not think is correctable.

Possibly. But I'm skeptical, given how many of these things have been sold and are in use from a variety of sources (Tuba Exchange, Laabs Music, Mack Brass, ...).

Can you take off your compensating 1st valve tuning slide and press down the 1st valve?

Yes.

Do the two piston holes line up perfectly with both tubes?

Yes -- when the valve is pressed down, mine align perfectly.

On mine, the bottom one lines up but the top one is not -- a little bit offset clockwise. I think it's just because it's a knock-off horn and cost only $1000 instead of $7000+ for the Yamaha. ;-)

Well, when I got my horn, it was only $750. I'm playing it in a band now on a regular basis and it's great. The only speculation I might make -- but which seems very unlikely -- is that possibly at some point a couple of the pistons got switched to the wrong valve cylinders. I don't know if the horn would even be playable then -- although my old 1924 Buescher is playable if the "right" ones (1 and 3) are switched.

Otherwise, I'd suggest you contact Tom McGrady and tell him you've noticed this and ask him what he thinks. If it is a manufacturing defect that got past him, he might want to make good on it.

[cassb]

omg, guys, I am so embarrassed. I have had the 1st and 3rd valves reversed for years! I had no idea the horn would even play with them reversed like that, so I figured it was just a defective horn.

I take it completely apart and soak in the bathtub a couple times a year. Sometimes I lose track of which valves go where, but assumed it would only play if they were in the right place.

No wonder the upper register has been so unstable! I could not hit a high G dead-on for the life of me. Now with the valves in the right place, it's effortless. Funny too, now with them in the right cylinders, the valve guides are tighter... who knew.

So... never mind. :-)

[iMav]

Congrats on the “new horn”!!

[ghmerrill]

omg, guys, I am so embarrassed. I have had the 1st and 3rd valves reversed for years! I had no idea the horn would even play with them reversed like that, so I figured it was just a defective horn.

I think that's probably happened to all of us. I'm just glad I thought of the possibility -- remembering when I've done the same thing -- and more than once. Now I'm EXTREMELY careful to either deal with one valve at a time or to keep all piston/valve parts for each valve in its own little plastic box (or tray section -- see below) while I'm working on a horn. That's also important if you take out the pistons for longer term storage (which I do for my Wessex Eb "Champion" tuba -- or the valves will freeze up). Then I'm EXTREMELY careful about identifying which piston I'm putting into which cylinder (the piston is normally stamped somewhere on the top, but obscured under a felt/rubber washer).

Here's an equipment recommendation for those who mess with their valves or other parts (which most people do at one point or another, even if it's just part of the cleaning process ...

Years ago my son got me a set of Grypmat "tool box organizers," saying "Maybe you can use these." They've become a part of my life. The "small" one I have has four parallel sections, each of which can handle a valve piston and associated parts. Unfortunately, I can't find that one offered as a single product (not part of a set) online either at Amazon or the Grypmat site. But Amazon also lists several competing products that seem to be about the same. They're a soft (silicone?) material and won't mar anything -- but very sturdy and virtually indestructable.