TromboneChat

What is the modern ideal material for rotor bumpers?

Replacements I see for sale on line looks suspiciously like the black plastic bumpers that came on the horn and were overly noisy from the outset.

I just replaced two of those with real cork I cut from a bottle stopper and they ARE quieter but seem very crumbly and not durable.

I see cork being sold for this purpose but it doesn't look any more sturdy than my bottle cork.

Black nitrile rubber on the actuated side - you need a certain hardness to ensure that the usual range of thumb/finger pressure doesn't significantly affect the valve alignment.

Clear silicone rubber on the open side - this only has to withstand spring pressure, which is constant, and the softer material gives quieter releases.

Obviously the colors don't mean anything, they're just the usually encountered form of those two materials.

Also, the fact that there's noise when the bumper is contacted doesn't necessarily mean the bumper is to blame - virtually any form of rotor or linkage play could also be responsible... even 'from the outset', depending on the manufacturer.

I had a bumper that was too "springy" - caused the valve to bounce and "double-clutch" when engaged. I blamed it on the valve, and was about to give up on the trombone - but the valve was faultless. John Sandhagen spotted the problem when he watched me play, and replaced the elastic (silicone?) bumper with a more rigid black (nitrile?) bumper. Took him 5 minutes to diagnose and cure. Problem solved. I kept the trombone! Thanks John.

Osmun has some fancy ones (neoprene?). I had them put them on my bass and they seem good. I think my newish edwards tenor came with something similar from the factory.

I got a bunch of cord from theoringstore.com. They have various materials and hardnesses (is that a word?) I use silicone 50 and buna 50, but you can get firmer stuff if you're afraid of bouncing. Neoprene tends to be a bit too hard and can be noisy. But as ithinknot pointed out, there is a general tendency for people to always blame the bumpers when they hear noise. There are quite a few things that can cause noisy valve action besides the bumpers.

Bumpers are for the weak. Just memorize exactly where the valve should be at rest and when actuated.

Burgerbob wrote: ↑Tue Nov 22, 2022 8:54 pm Bumpers are for the weak. Just memorize exactly where the valve should be at rest and when actuated.

Put in a couple of these to make it challenging.

Now we're talking!

These are the original mid-1970s bumpers. Not sure what these are... some sort of hard vinyl? The difference in sound between these and the cork tells me that these were 90% of the clank.

Neoprene sounds promising. I've got an old mouse pad I could slice up.

These bumpers are hard but I don't think they ever made the valves bounce.

robcat2075 wrote: ↑Tue Nov 22, 2022 10:37 pm These are the original mid-1970s bumpers. Not sure what these are... some sort of hard vinyl?

As I recall, most non-cork bumpers in the '70's were neoprene. I'm using Viton™ these days; it seems to hold up better than nitrile (buna n) or neoprene - but that's for the tiny little o-ring bumper in an Olds rotor. Slightly different application.

Robert, I think the mouse pad material is too soft!

The originals are probably the mentioned neoprene and have hardened over time.

What flavor horn?

Don't you have to shave cork to get the valve aligned just right? How do you do that with rubber?

Just curious. Of course if you have those adjustable bumper holders it doesn't matter.

timothy42b wrote: ↑Wed Nov 23, 2022 6:42 am Don't you have to shave cork to get the valve aligned just right? How do you do that with rubber?

Just curious. Of course if you have those adjustable bumper holders it doesn't matter.

You can trim rubber cord just like you trim cork. A good single edged razor blade is perfect for this.

Bonearzt wrote: ↑Wed Nov 23, 2022 6:39 am What flavor horn?

It's a Holton TR181

robcat2075 wrote: ↑Tue Nov 22, 2022 10:37 pm Neoprene sounds promising. I've got an old mouse pad I could slice up.

There's quite a difference between Neoprene foam, as used in a mouse pad or wet suit, and the relatively hard solid rubber-like materials that are molded or extruded (for O-rings, cord, valve bumpers, etc.) of a variety of chemical compounds in different hardnesses (Neoprene, Buna-N, Viton, EPDM, Silicone, ...). The choices are legion! Many are widely available at your local hardware store.

https://www.marcorubber.com/o-ring-mate ... erence.htm

Posaunus wrote: ↑Wed Nov 23, 2022 9:23 am

robcat2075 wrote: ↑Tue Nov 22, 2022 10:37 pm Neoprene sounds promising. I've got an old mouse pad I could slice up.

There's quite a difference between Neoprene foam, as used in a mouse pad or wet suit, and the relatively hard solid rubber-like materials ...

I think you all know... I'm going to try that neoprene foam.


Here is a comparison of new bottle cork and old plastic bumpers. The plastic bumpers on the second valve were even noisier than those on the first valve are.

robcat2075 wrote: ↑Wed Nov 23, 2022 3:14 pm Here is a comparison of new bottle cork and old plastic bumpers. The plastic bumpers on the second valve were even noisier than those on the first valve are.

Why would you use plastic bumpers? It's pretty obvious that rigid materials (such as plastic - or metal, or glass, or wood, or ...) will clunk and ring when hit.

You must use an elastic material that gives slightly (and softly) when struck. There are many readily available options.

Posaunus wrote: ↑Wed Nov 23, 2022 3:28 pm

robcat2075 wrote: ↑Wed Nov 23, 2022 3:14 pm Here is a comparison of new bottle cork and old plastic bumpers. The plastic bumpers on the second valve were even noisier than those on the first valve are.

Why would you use plastic bumpers?

That's what the horn came with. Original equipment. That is what the professional experts put there.

Just arc weld in a blob. Then file it down to align the valve.
Never wears out. Clanging sound will cover up wrong notes!

Posaunus wrote: ↑Wed Nov 23, 2022 3:28 pm

robcat2075 wrote: ↑Wed Nov 23, 2022 3:14 pm Here is a comparison of new bottle cork and old plastic bumpers. The plastic bumpers on the second valve were even noisier than those on the first valve are.

Why would you use plastic bumpers? It's pretty obvious that rigid materials (such as plastic - or metal, or glass, or wood, or ...) will clunk and ring when hit.

You must use an elastic material that gives slightly (and softly) when struck. There are many readily available options.

Don’t over parse the difference between the words plastic and rubber here. This is not a technical presentation.

If you feel like experimenting, get the right diameter cross section of Oring in a handful of materials and durometers (hardness). At a good hardware store you can probably get several lifetimes supply for $5. I looked this up a few months ago, Holton French horns were .280”, off the top of my head, but I might be completely wrong.

Cheers,
Andy

It turns out that artificial rubbers like Neoprene are plastic. Plastic is a very broad label for numerous artificial substances made from synthetic polymers of which synthetic "elastomers" are a subset.

I suppose the irony is that, over time, this plastic (a synthetic polymer) has become less plastic (flexible, malleable).

It is possible that when those bumpers were new they were fine but, judging from the serial number, the horn had been on the shelf for five years already when I bought it and time has not bettered them.

The bumper material is clearly making a bit of a difference in your video, but I'd be willing to be that there is "play" or excess freedom of movement in several axis that are contributing to the noisiness of those valves. Likely in the lever, which is easy to see if the lever twists or shifts at any of the joints before engaging the valve, and likely in the rotors themselves having excess end (vertical) play between bearings.

A properly fit lever (minimal play between posts on the saddle/bridge) and squared ends, a tight linkage joint like a miniball or well-tied string linkage, and a properly fit rotor/bearings should eliminate any "metallic" sounding action and you should have only a bit of dull thudding of the stoparm against the bumper material as the valve moves between positions.

It's not uncommon to see mediocre fitment of these parts even on brand new instruments, never mind horns that have been played regularly for years.

Blabberbucket wrote: ↑Thu Nov 24, 2022 1:15 pm The bumper material is clearly making a bit of a difference in your video, but I'd be willing to be that there is "play" or excess freedom of movement in several axis that are contributing to the noisiness of those valves. Likely in the lever, which is easy to see if the lever twists or shifts at any of the joints before engaging the valve, and likely in the rotors themselves having excess end (vertical) play between bearings.

A properly fit lever (minimal play between posts on the saddle/bridge) and squared ends, a tight linkage joint like a miniball or well-tied string linkage, and a properly fit rotor/bearings should eliminate any "metallic" sounding action and you should have only a bit of dull thudding of the stoparm against the bumper material as the valve moves between positions.

The levers are quite solid. I can't shake them. I think their tightly coiled springs may act to eliminate rattling. The valves themselves can be shaken a bit but it is slight.

However, the ball-and-socket linkage is an inherently flawed design, I think. If it's tight enough to eliminate rattle then it's not free enough for the motion it needs to do and vice-versa.

So I quite like my little red tube on the 2nd valve. It doesn't deter proper lever motion and yet it is always in firm contact at each end with no "play".

Burgerbob wrote: ↑Tue Nov 22, 2022 8:54 pm Bumpers are for the weak. Just memorize exactly where the valve should be at rest and when actuated.

hahaha - troll.

Hardware store. O rings. Many sizes. And often you can find fresh dense cork to be cut to size.