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Can someone point me in the right direction? I need to change the cork bumpers on my 186, and have no clue how to go about doing that. Can I do this myself, or should I have a music shop do it?

Thanks in advance,
Josh

It's a bit of an involved process to describe in words -- might be good to take it to a shop one time to teach you how to do it. You can do it at home, but there are several steps and details that you need to follow which are better described in person.

Having it done at a repair shop chould be pretty inexpensive... not more than $20.

Vacuum cleaner belt (the cylindrical kind) is a great material to use as bumpers. You'll need some of that and some razor blades.

Matt Walters told me something about using rubber O-rings. I couldn't find O-Rings large enough at the Lowe's in town. I could only find 1/8 inch width and I need something closer to 1/4 inch.

Is the windshield washer line hollow? If so, is that not a problem?

TubaTodd wrote:Matt Walters told me something about using rubber O-rings. I couldn't find O-Rings large enough at the Lowe's in town. I could only find 1/8 inch width and I need something closer to 1/4 inch.

Is the windshield washer line hollow? If so, is that not a problem?

I buy my rubber o'ring stock at a local industrial supply house. I usually just buy a couple of feet at a time. The stuff I use measured .280" diameter and I think it is sold as 5/16" stock. I've found the easiest way to install it is to take the bumper plate off... lock it in a vise... and use a screwdriver to force the rubber into the slot. Then... trim the rubber flush with the front and back of the plate with a razor blade. Of course, in order to get the stop plates off the horn, you first have to remove the stop arm from the rotor spindle. The new bumper might require trimming after you put things back together. This is determined by taking the cap off the back of the rotor and noting the position of the lines on the rear rotor bearing plate and the line on the center of the rotor spindle. You also need to insure that the rear bearing plate is aligned with the mark on the rotor housing. If there is anything about this that leaves you scratching your head, you probably need to watch a repairman perform this for the first time before attempting to do it yourself.

Dan, I find it easier to simply hold the stop plate in the vise, grab each end of the o-ring material, pull it taut, stretching it, and then insert it into the stop plate. No jamming with screwdrivers. When it's in, just cut it flush.

Chuck(G) wrote:Dan, I find it easier to simply hold the stop plate in the vise, grab each end of the o-ring material, pull it taut, stretching it, and then insert it into the stop plate. No jamming with screwdrivers. When it's in, just cut it flush.

That does sound like a great way to do it! I think I recall you mentioning it in a previous post but I keep forgetting to try it! .... And I just finished up a 186 yesterday using my old screwdriver method.... duh

harold wrote:I learned that as a juvenile deliquent when I was slashing tires.

TubaTinker wrote:I buy my rubber o'ring stock at a local industrial supply house. I usually just buy a couple of feet at a time. The stuff I use measured .280" diameter and I think it is sold as 5/16" stock. I've found the easiest way to install it is to take the bumper plate off... lock it in a vise... and use a screwdriver to force the rubber into the slot. Then... trim the rubber flush with the front and back of the plate with a razor blade. Of course, in order to get the stop plates off the horn, you first have to remove the stop arm from the rotor spindle. The new bumper might require trimming after you put things back together. This is determined by taking the cap off the back of the rotor and noting the position of the lines on the rear rotor bearing plate and the line on the center of the rotor spindle. You also need to insure that the rear bearing plate is aligned with the mark on the rotor housing. If there is anything about this that leaves you scratching your head, you probably need to watch a repairman perform this for the first time before attempting to do it yourself.

I have some hard rubber bumper stock that a music store gave me many moons ago. Unfortunately, the diameter is entirely too large. The last time I HAD to replace the bumper on my 56J I took a piece of that rubber stock and did my best to cut it to fit. That piece is still on my horn, but it's rather ugly. No, I don't think I could have used a screwdriver to wedge an uncut piece of the rubber material. In fact, I believe I may have tried that first. In any event, I will try acquiring some bumper material from one of the sources mentioned in this post.

TubaTodd wrote: I have some hard rubber bumper stock that a music store gave me many moons ago. Unfortunately, the diameter is entirely too large. The last time I HAD to replace the bumper on my 56J I took a piece of that rubber stock and did my best to cut it to fit. That piece is still on my horn, but it's rather ugly. No, I don't think I could have used a screwdriver to wedge an uncut piece of the rubber material. In fact, I believe I may have tried that first. In any event, I will try acquiring some bumper material from one of the sources mentioned in this post.

The space for the rubber is quite a lot smaller than the diameter of the o'ring stock. It's not going to go in under mild pressure. You are going to have to really push (or stretch in the case of Chuck's method) to get the rubber into place.

Here's another resource for o'ring stock:
http://www.mcmaster.com/
When you search the site, type in "O'ring cord stock". Then just select the size you need. Delivered to your door.

Tubafour,

since you asked to replace CORK bumpers, the method is slightly different, because cut cork will wear off faster than when it´s left intact:
instead of inserting the rubber bumper and trimming it with a blade to ensure valve position and swinging range, you do as follows:
- cut off a suitable length of cork rod
- use small and blunt screwdriver to gently jam the cork into its place. (Hold cork against the slot, use the FLANK of the screwdriver to compress the cork and shove it in. You don´t want to use the s.d.´s point).
To adjust the valve position, check the markings as mentioned in other posts and jam more or less of the cork into the slot as needed.

I believe what you're looking for is buna rubber. It doesn't have the bounce that neoprene does and lasts a long time. You can get it from a supply place that sells gaskets, etc. pretty cheaply by the foot in different diameters. Try a couple of different diameters(6mm-8mm?)to get a tight enough fit in the holder and the desired size to make the valve stop in the right place(check under the cap). Different valves may require different sizes. Take an old one with you to get the right size.

Ike

When buying O-ring material, it helps to know how to talk the talk.

The "hardness" of an o-ring material will give is denoted by the term "durometer". 20 durometer, for example, is very soft; where 50 durometer is quite hard. You might, for example, want to use a hard material on the "key depressed" stop and a soft material on the "key return" stop.

http://o-rings.globalspec.com/

Ashbory bass strings
viewtopic.php?t=11204&highlight=bumpers

Thanks for your help, guys!

I decided to take my horn to the local music shop (Music Doctors in Johnson City, TN). Teresa changed all 4 return bumpers in 15 minutes for only $1. She trimmed them all, and even confirmed that my valves were properly aligned afterwards. Wonderful!

If anyone is in my region, take your horn to her!!!

tubafour wrote:Teresa changed all 4 return bumpers in 15 minutes for only $1.

I'm going to start sending my stuff there!

tubafour wrote:Thanks for your help, guys!

Don't mention it! Our pleasure.

I decided to take my horn to the local music shop (Music Doctors in Johnson City, TN). Teresa changed all 4 return bumpers in 15 minutes for only $1. She trimmed them all, and even confirmed that my valves were properly aligned afterwards. Wonderful!

If anyone is in my region, take your horn to her!!!

The same job at the local music stores would likely run in excess of $50. (They charge a full hour labor for fractions thereof.)

bump . . . (no pun intended)
'Found this thread useful and cool.

.

Here's a web site that I recommend to anyone wanting to learn about rotary valve maintenance. It's Jeff Funderburk's web site at UNI and the videos are excellent.

http://www.uni.edu/drfun/repair_video/r ... index.html" target="_blank

Also I was lucky enough to find the exact size rubber rope for Miraphone rotary horns that requires no trimming once it's installed. Makes the job a lot easier.

Roger