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Thread: Mack Brass euphonium: valve compression

  1. #11
    Join Date
    Dec 2011
    Location
    Central North Carolina
    Posts
    1,990
    I've never had a problem with getting an air-tight seal with the paper towel roll and garbage bag trick. But I may not have described it sufficiently clearly. The paper towel within the garbage bag must fit very tightly into the bell and be forced down very firmly. Of the instruments I've tried it on, I've found leaks in only two: an old 60s vintage Martin baritone that leaked severely through the valves; and my 1924 Buescher Eb tuba that surprisingly (original valves and plating) leaks only mildly through the third valve.

    It sounds to me as though your first valve is leaking. With the bell blocked, you shouldn't hear ANY hissing or detect ANY air coming out of the bottoms of the valves. I just tried the test on my Mack Brass euph and just about busted my gut before popping the roll (about a half-used roll in a plastic bag) out of the bell. Not a hint of a leak.

    You really need to talk to Tom about this. It's possible that one or more of the valves was poorly fabricated, is cracked, or was ground or polished too much. This should be covered by the standard warranty.
    Gary Merrill
    Wessex EEb Bass tuba (Denis Wick 3XL)
    Mack Brass Compensating Euph (DE N106, Euph J, J9 euph)
    Amati Oval Euph (DE N106, Euph J, J6 euph)
    1924 Buescher 3-valve Eb tuba, modified Kelly 25
    Schiller American Heritage 7B clone bass trombone (DE LB K/K9/112 Lexan, Brass Ark MV50R)
    1947 Olds "Standard" trombone (Olds #3)

  2. Hi Randy. When you mentioned leakage from the breather holes at the bottom of the valves, that got me thinking. I noticed on some of the Chinese valves that the fitting of the brass knuckles into the pistons is not always done with the best of workmanship. (one of the things they need to learn to do better) I would take a careful look at the seams between the stainless steel piston wall and those brass knuckles - or passage ways inside the piston. They should be soldered and trimmed smooth at the outside edge. It is possible that one of them missed the mark in the soldering process (or perhaps it was trimmed to closely) and you have a leak that lets air migrate through the piston, out the bottom and then out the breather hole on the bottom valve cap. There should be a breather hole at both the top and bottom of the piston. Without it, there would be serious compression built up when the piston returns to its upright position. The hole in the top of the piston lets that air escape. This is a bit of a mystery. Paul
    BMB F tuba 445s
    BMB CC (BAT) 865s
    Mack Euphonium 1150s
    Wessex F Cimbasso

  3. #13
    Paul, On the upstroke of the valve, doesn't the air simply exit the valve casing through the hole that the valve stem passes through? And yet it does seem that I recall seeing a small hole at the top of the valve, and of course the larger hole in the center of the bottom. Maybe these extra holes aid the airflow above and below the piston for the most rapid possible action? The brass knuckles possibility sounds intriguing. It seems that I could turn the valve piston upside down, cover the opening at the top of the valve, fill the valve with water through the bottom hole, and see whether it leaks out around any of the brass knuckles. I could also clean the valve off, plug the top hole, seal my lips around the bottom hole, and blow to see whether any air flows through a gap like you describe.

    Tomorrow. It's past bedtime now! Thanks for the thoughts.

    Randy

  4. #14
    Gary, from the sound of it, I probably didn't jam the paper towel down the horn quite as hard as you did. Even with the air leaking, I was able to pop it out without overstressing the old diaphragm. So perhaps a little more force could have given me a perfect seal. At any rate, I got a good enough seal to serve the purpose. By the way, the reason I thought some air was probably leaking around the paper towel is that even on my son's 842, I felt that a little air was going through the horn somewhere, and I figured that the wrinkles in the garbage bag were probably the best explanation. On my Mack Brass horn with its leak, I don't know how I could have determined whether I was losing any air around the bell plug.

  5. Randy. A simple leak test on the knuckles. Remove the piston. Cover the top vent hole with your finger and blow into the bottom hole. If there is indeed a leak around the knuckles it should be not too difficult to track down. Though I'm thinking it is a long shot. Water would certainly be a visual aid at this point as would smoke.
    BMB F tuba 445s
    BMB CC (BAT) 865s
    Mack Euphonium 1150s
    Wessex F Cimbasso

  6. #16
    Paul, I couldn't blow any air through the valve, nor did any water leak from any of those joints. So the valve has good mechanical integrity. I haven't had time to give Tom a call yet. I've learned that you shouldn't call Tom if you don't have a little time on your hands, and time has been tight the past few days as I've scrambled to finish a bedroom makeover before family guests arrived for Christmas. After 3 12-hours days on the project and part of a 4th, I finished and got the furniture moved back into the room about 5 minutes before everyone arrived. Phew! But no time to talk to Tom.

  7. #17
    I've let this issue slip over a few busy weeks here, with no further action on my part until today. I did drop an email to Tom at Mack Brass just now. I'll get back to the forum again when there's anything substantial to add. Thanks to all for the various kinds of help so far.

  8. Don't know if this might help. I play a King 2341 new style tuba (4 piston valves) as my primary horn which is made in an assembly line where I believe they just drop the valves in without lapping . I have read in some post on a different board that one of the complaints some folks had about the new style 2341 was that some of the horns, not all, were stuffy because of the air leakage around the valve. Some valve oils are just too thin for a particular horn and don't seal the valve properly. I took my horn to a repair guy to have the valve guides changed out to nylon ones and lighter springs put in and one of the recommendations I got when I picked the horn up was to use a thicker valve oil. When I switched to Hetman's #2 the problem went away. I have since switched to Holton Rotor oil which I like even better. With the Hetman's I would get this gunk build up which so far doesn't seem to be an issue with the Holton, although its not been that long since I changed oil. One thing I learned the hard way, some brands of oils don't play nice with other types and will gunk up if mixed so wash the horn or swab the valves well before changing brands or type of oil. If this sounds like it might fit your situation, you might try googling valve oil site:chisham.com as there have been extensive posts on that on that site over the years. Let me say, once I switched to the thicker oil I started hearing a big difference the sound the horn was making as well as getting compliments on how good the horn sounded. YMMV, but best of luck.
    Last edited by Sandlapper; 01-15-2015 at 03:30 PM.

  9. #19
    Thanks for the comment, Sandlapper. My oil (Fat Cat) seems pretty thick to me, but the only thing I have to compare it with is standard music-store oil and my son's Fast Al Cass. I'll see what Tom says; depending on the outcome of my communication with him, I may try that Hetman's #2, which I've also seen mentioned elsewhere as a thicker oil.

  10. #20
    Join Date
    Dec 2011
    Location
    Central North Carolina
    Posts
    1,990
    Quote Originally Posted by Sandlapper View Post
    I took my horn to a repair guy to have the valve guides changed out to nylon ones and lighter springs put in and one of the recommendations I got when I picked the horn up was to use a thicker valve oil. When I switched to Hetman's #2 the problem went away. I have since switched to Holton Rotor oil which I like even better.
    But rotor oil is typically much lighter than most piston oils, isn't it? It has to be in order to seep into the rotor bushing joints.
    Gary Merrill
    Wessex EEb Bass tuba (Denis Wick 3XL)
    Mack Brass Compensating Euph (DE N106, Euph J, J9 euph)
    Amati Oval Euph (DE N106, Euph J, J6 euph)
    1924 Buescher 3-valve Eb tuba, modified Kelly 25
    Schiller American Heritage 7B clone bass trombone (DE LB K/K9/112 Lexan, Brass Ark MV50R)
    1947 Olds "Standard" trombone (Olds #3)

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