Mack 410, replacement stop

[huskerdooo]

worn_rotory_stop.jpg

Hi All,

Can anyone tell me where I can get a replacement stop for my Mack 410? The part seems to stop the linkage. Mine seems worn and lets the linkage slap the center of the valve. The stop I am speaking of is circled in red..

Thanks!

[UDELBR]

You mean the neoprene bumper? Any repair shop can do it for you, or sell you some. I've always used vacuum cleaner belts sliced up for these.

[Dan Schultz]

There's more involved here than simply putting in another bumper. The bumpers also control the rotor alignment. Take it to a repairman. From your description of the problem... you may have some things going on that just a new bumper might not take care of.

I've found that those opaque bumpers are too soft and will compress enough for the stop arm to strike the bumper plate.

[imperialbari]

image.jpg

Had to work a bit on the photo to see the details. Still I don't get the function of the circled part.

Do the Chinese use a stopping system totally different from the horseshoe-holding-bumpers?

Klaus

[Dan Schultz]

.... Do the Chinese use a stopping system totally different from the horseshoe-holding-bumpers? Klaus

Klaus.... same system except instead of clicking.... they make a 'crick' sound.

[huskerdooo]

image.jpg

Had to work a bit on the photo to see the details. Still I don't get the function of the circled part.

Do the Chinese use a stopping system totally different from the horseshoe-holding-bumpers?

Klaus

There is a horse shoe like thing that holds the round bumper. The bumper seems to be a stop for the linkage when the valve is pressed. It is not doing its job, so the side of the linkage hits the center stem if it is pressed hard or fast.

I am concerned about just placing anything in there to replace it.. my thinking that whatever I put in there will affect how much the valve can open. Maybe I am overthinking it. If it is pressed slowly, the bumper seems to work.. but if it is compressed a bit, it hits.

[huskerdooo]

There's more involved here than simply putting in another bumper. The bumpers also control the rotor alignment. Take it to a repairman. From your description of the problem... you may have some things going on that just a new bumper might not take care of.

I've found that those opaque bumpers are too soft and will compress enough for the stop arm to strike the bumper plate.

It actually seems worn when compared to the other valves where it is still round. It looks like it is nylon.

[Dan Schultz]

There's more involved here than simply putting in another bumper. The bumpers also control the rotor alignment. Take it to a repairman. From your description of the problem... you may have some things going on that just a new bumper might not take care of.

I've found that those opaque bumpers are too soft and will compress enough for the stop arm to strike the bumper plate.

It actually seems worn when compared to the other valves where it is still round. It looks like it is nylon.

The bumper in question does not appear to be worn but looks like it was trimmed to achieve proper rotor alignment. The reason why the linkage is striking the stop arm is because of that 'gummy' soft opaque rubber bumper. Like I said before.... if you don't know the dynamics of what's going on here you need to take your horn to a qualified repairman.

[huskerdooo]

There's more involved here than simply putting in another bumper. The bumpers also control the rotor alignment. Take it to a repairman. From your description of the problem... you may have some things going on that just a new bumper might not take care of.

The bumper in question does not appear to be worn but looks like it was trimmed to achieve proper rotor alignment. The reason why the linkage is striking the stop arm is because of that 'gummy' soft opaque rubber bumper. Like I said before.... if you don't know the dynamics of what's going on here you need to take your horn to a qualified repairman.

Thanks, I will take it in. I do have another post out there re: recommendations for a shop near me.

[Worth]

http://www.votawtool.com/supplies/rotar ... umper.html" target="_blank" target="_blank

Here are some material options if you want to do it yourself. They will require trimming for proper alignment but should hold up well. It's cheap so I bought some to replace my 410 bumpers but haven't got around to it yet

[MackBrass]

If I remember correctly the size is 3/16th and there is little to no trimming involved. Once the old is replaced the clank should disappear, any repair shop should have this ready to go. If you take it in stay and watch them so it if they allow so you can do it yourself in the future as this is pretty basic and nice to know how to do it yourself. If you have any questions just give me a call. In the past I have done what Alexander does on their new tubas and bend the stop arm at the end so even when the bumper wears out there wont be the clank. Bending the stop arm is not something I recommend unless you know how to do it without breaking it at the threaded area.

If you go with cork, I think old fashioned cork is the best, you can use 1/4 inch but this will have to be trimmed so the valve lines up properly.

[huskerdooo]

Thanks, if I buy the bumper cord there, is there anything else I should get for this tuba on the site?

[MackBrass]

Thanks, if I buy the bumper cord there, is there anything else I should get for this tuba on the site?

You should be good to go.

[imperialbari]

For now the cheapest solution is about removing the bumper and then putting it back with the shaved edge now sitting opposite the touch point of the stop arm.

This bumper being soft means that adjusting the rotation after doing a normal finger pressure may call for a shaving, whereas the faster and harder pressure on the shaved edge in real life playing will lead to the over-rotation causing the said noise.

The effect of the actual shaving will be minimal, if the shaved edge sits well inside the grip of the horse shoe.

Klaus

[huskerdooo]

Yes, I considered flipping it around, but I think I will wait until I get the new rubber in case I mess up the old stop. The instrument needs to be played daily in the mean time.

Thank you.