Greenhoe Valve Disassembly

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Pgrimss
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Joined: Sun Jan 10, 2021 11:15 am

Greenhoe Valve Disassembly

Post by Pgrimss » Sun Jan 10, 2021 11:20 am

I just had my Geenhoe GB4-1Y trombone repaired the other day and when I got it back, I noticed the valve was scratchy and made an audible scratching sound. The valve was flawless before repair and so now I am wondering if maybe some junk got into the valve so I want to disassemble and clean it out. I started to take it apart but wasn’t entirely sure of myself and stopped where I was and put it back together. How should I go about disassembly the valve. I watched some tutorials and researched online but found that when I used the rubber mallet to hit the back side of the valve, nothing happened.

Thanks,

Patrick
ChadA
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Location: Dayton, OH
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Re: Greenhoe Valve Disassembly

Post by ChadA » Wed Jan 13, 2021 9:53 am

I asked a similar question in the Maintenance forum: https://trombonechat.com/viewtopic.php?f=15&t=14331

I haven't yet taken my Greenhoe valve apart. If you get yours apart, let me know what you learned. :)
Bonearzt
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Re: Greenhoe Valve Disassembly

Post by Bonearzt » Wed Jan 13, 2021 9:58 am

Pgrimss wrote:
Sun Jan 10, 2021 11:20 am
I just had my Geenhoe GB4-1Y trombone repaired the other day and when I got it back, I noticed the valve was scratchy and made an audible scratching sound. The valve was flawless before repair and so now I am wondering if maybe some junk got into the valve so I want to disassemble and clean it out. I started to take it apart but wasn’t entirely sure of myself and stopped where I was and put it back together. How should I go about disassembly the valve. I watched some tutorials and researched online but found that when I used the rubber mallet to hit the back side of the valve, nothing happened.
Thanks,
Patrick
Before you mess with it, I would return it to whomever serviced it!
Eric Edwards
Professional Instrument Repair
972.795.5784

"If you must choose between two evils, choose the one you haven't tried yet."
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paulyg
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Re: Greenhoe Valve Disassembly

Post by paulyg » Wed Jan 13, 2021 6:33 pm

Greenhoe valves have much tighter clearances between the rotor and the casing than most others. Another complication is that both bearing plates are separate from the casing, which reduces the rigidity.

If your valve is scratching, my first guess would be that your tech did not fully seat one or both of the bearing plates into the rotor casing. This will cause serious damage to the bearings and/or the casing if it is allowed to remain that way. You should take off the retaining rings and make sure that there is no space between the bearing plate and the rotor case (360 degrees around).

To get the valve core out (and push out the back bearing plate), you will actually need to remove the stop arm screw and the stop arm itself from the spindle first. This is probably different than the process you saw in the tutorial video. You can then gently tap the spindle to release the back bearing plate. I'd recommend leaving the spindle bearing plate in place, as it clocks the valve core when everything's fully installed, and will add some rigidity to the casing (preventing warping) if you clean the valve section.

The valve core can then come out. When I took my Greenhoe apart, I had to use liberal amounts of oil to get it out and then back into the casing. It would get stuck otherwise (with the oil, it dropped right in).

If ANY of the above does not make sense, take it to a tech! Preferably a better one than did the work in the first place...
Paul Gilles
Aerospace Engineer & Trombone Player
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