Valve rebuild and/or opening valve ports

[WGWTR180]

Two part question here fellow trombonists and trombone techs.

1. How does one know if valves needed to be rebuilt? Most of my instruments are older and I know through time valves can wear out and need to be rebuilt. But sometimes its hard to tell if if happens slowly over time,

2. How does one know IF it's possible to open valve ports? Can you tell by just taking the valve apart and looking? If so what do you look at?

Many thanks!!!

[hornbuilder]

Hey Bill.
A couple of things.
If you pull the valve section tuning slides out, without activating the valve, then, near the end of the pull, activate the valve. How much of a "pop" does it make? That will give an idea as to how much seal the rotor has in casing.

If you hold the stop arm, and try and move the rotor along it's axis, is the discernable movement? If you move the stop arm for/aft, in the direction of activation, is the discernable movement? These will tell you if you have excess play any where.

Correcting excess play is a matter of swedging the bearings. Easy and pretty quick with the right tools. If the rotor doesn't seal well, that is a little more complicated, involving nickel plating and refitting the rotor to the casing.

The possibility of opening the ports depends on the size of the rotor core, and how it was machined.

[WGWTR180]

Thanks Matthew! I wish all valves worked as well as yours!!!

[hornbuilder]

PS. FWIW. I really don't think opening the ports is worth it with most traditional rotor valves. The reason is they're just too small in diameter, and there is not really enough material available to be removed to make a huge difference. Yes, it will make "some" but it is only small

The photo shows. .594" ball in a Bach 50 rotor. There is .107" protruding from the casing. That is a HUGE reduction in the bore!! There is no where near enough removable material to bring the rotor up to bore size.

Screenshot_20230703-130711.png

[tbonesullivan]

What do companies that advertise the port opening for Bach 42 valves do? Do they also make changes to the casing itself to give a bit more of a smooth air passage? The only "regular" rotor horns I have had for many years are Yamahas, so I haven't really had any need / desire to have the valve worked on. My 36 has a standard bach rotor, but I haven't heard of those really being undersized for the .525 bore.

[hornbuilder]

The ports of the rotor are machined out in some way. Generally it is with a hand held device like a Dremel, with a grinding bit. Really the only areas where you can remove material is near the ends of the port. It is possible to remove "some" from the middle, which is where it is most needed, but the amount is determine by the thickness of the web between the 2 ports.

[peteedwards]

I have bored out rotary cores on a 3 axis CNC with an undercutting ball mill, also known as a lollipop mill. There is plenty of material to be removed even in traditional rotaries to maintain cross-sectional bore area through the valve passage, although the cross section will not be round. It is very effective but not as good as valves that have been designed to be optimized. A big problem with traditional rotary valves are the tight corners leading into & out of the outer casing.

[WGWTR180]

I have bored out rotary cores on a 3 axis CNC with an undercutting ball mill, also known as a lollipop mill. There is plenty of material to be removed even in traditional rotaries to maintain cross-sectional bore area through the valve passage, although the cross section will not be round. It is very effective but not as good as valves that have been designed to be optimized. A big problem with traditional rotary valves are the tight corners leading into & out of the outer casing.

Are you an experienced tech or did you just do this??

[Crazy4Tbone86]

This thread is focusing on the impact of opening up the ports on a standard rotor. Some say it makes a difference. Some say it does not. Some people have actually ruined their valves because they have gone too far with this process! I believe the standard valve can be improved, but on a limited basis…….there is a finite amount of metal to work with, so the change is quite limited. I think Matthew’s ball bearing placed in the rotor core illustrates that very well.

One thing that was mentioned by Matthew that I believe is VERY important is the adjustment of a rotary valve so that it has no lateral movement. It can make or break the success of a rotor and the entire instrument. I have had players come to me and asking for an after-market valve and I tell them that we should try to adjust the bearings first so that the original rotor is working as it is designed to work. About half of those players are very pleased with that fine-tuning of the original rotor and stay with it. When the bearings are fitted perfectly and the rotor has no lateral play, the instrument definitely focuses better and has more core.

[WGWTR180]

This thread is focusing on the impact of opening up the ports on a standard rotor. Some say it makes a difference. Some say it does not. Some people have actually ruined their valves because they have gone too far with this process! I believe the standard valve can be improved, but on a limited basis…….there is a finite amount of metal to work with, so the change is quite limited. I think Matthew’s ball bearing placed in the rotor core illustrates that very well.

One thing that was mentioned by Matthew that I believe is VERY important is the adjustment of a rotary valve so that it has no lateral movement. It can make or break the success of a rotor and the entire instrument. I have had players come to me and asking for an after-market valve and I tell them that we should try to adjust the bearings first so that the original rotor is working as it is designed to work. About half of those players are very pleased with that fine-tuning of the original rotor and stay with it. When the bearings are fitted perfectly and the rotor has no lateral play, the instrument definitely focuses better and has more core.

Great points! My repair tech has made such adjustments with great success.

[trombonedemon]

I'm definitely pleased with the porting of my rotors. The valve caps help center the sound because of the extra room. When. I got the horn both valves were supposedly the same measurements, but the f attachment played way more open, my tech confirmed it, it was ported. I think it's worth it if you get a worthy tech, my tech plays bass bone and knew what I wanted out of the valve.

[BGuttman]

I'd like to point out that there are many rotors that really don't need opening up. I've played King 4B's, Conn 88H's, and my Yamaha 682 which had very open rotors. The idea about opening valves came from the Bach 42B, which was provided with an undersize rotor from the start.

[WGWTR180]

I'm definitely pleased with the porting of my rotors. The valve caps help center the sound because of the extra room. When. I got the horn both valves were supposedly the same measurements, but the f attachment played way more open, my tech confirmed it, it was ported. I think it's worth it if you get a worthy tech, my tech plays bass bone and knew what I wanted out of the valve.

Who is your tech?

[dbwhitaker]

In my limited experience with 3 old horns my 1970s Bach 50B2 has air tight rotors that strongly resist pushing in the tuning slides and can make a loud popping noise when pulling the slides out. None of the rotors on my Holton TR-180 or my TR-183/5 can pop. They offer only minimal resistance to pushing in the tuning slides while making a whooshing sound. I sent my TR-180 to one of our esteemed TC techs and he assured me the rotors were fine despite the lack of resistance. (My 50B may have tight rotors but I rarely play it because they are so stuffy.) I did have the tech open the ports a bit on the TR-180 mainly because someone else told me they'd done it to their TR-180 with a good result. I'm not sure if it made much difference.

[WGWTR180]

In my limited experience with 3 old horns my 1970s Bach 50B2 has air tight rotors that strongly resist pushing in the tuning slides and can make a loud popping noise when pulling the slides out. None of the rotors on my Holton TR-180 or my TR-183/5 can pop. They offer only minimal resistance to pushing in the tuning slides while making a whooshing sound. I sent my TR-180 to one of our esteemed TC techs and he assured me the rotors were fine despite the lack of resistance. (My 50B may have tight rotors but I rarely play it because they are so stuffy.) I did have the tech open the ports a bit on the TR-180 mainly because someone else told me they'd done it to their TR-180 with a good result. I'm not sure if it made much difference.

Are we related? wgwhitaker

[peteedwards]

I have bored out rotary cores on a 3 axis CNC with an undercutting ball mill, also known as a lollipop mill. There is plenty of material to be removed even in traditional rotaries to maintain cross-sectional bore area through the valve passage, although the cross section will not be round. It is very effective but not as good as valves that have been designed to be optimized. A big problem with traditional rotary valves are the tight corners leading into & out of the outer casing.

Are you an experienced tech or did you just do this??

I'm not a tech, I am an engineer & machinist. I only work on my own horns.

[WGWTR180]

Are you an experienced tech or did you just do this??

I'm not a tech, I am an engineer & machinist. I only work on my own horns.

[trombonedemon]

I'm definitely pleased with the porting of my rotors. The valve caps help center the sound because of the extra room. When. I got the horn both valves were supposedly the same measurements, but the f attachment played way more open, my tech confirmed it, it was ported. I think it's worth it if you get a worthy tech, my tech plays bass bone and knew what I wanted out of the valve.

Who is your tech?

Scott Sweeney.

[WGWTR180]

Who is your tech?

Scott Sweeney.

Gracias!

[imsevimse]

On my old horns I've done the test and listned for the popping-sound. If the valves leak you can try thicker oil. I have a few horns that needed thicker oil and they definitely played better after, and the valves weren't to slow with that oil either, they worked as expected.

/Tom