Slidemeister (Chromatic & related only - no Diatonic discussion) > Maintenance & Repair 101

Findings and Thoughts on Slide Bumpers (Buffers)

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brorat:
I've spent a good bit of time looking at how best to replace slide bumpers on my harmonicas.  As you might expect, there's not a great deal of standardization among manufacturers, but for the ones I looked at, the measurements are very close.

The instruments I looked at are:
EastTop 2.0
EastTop Performer EAP-16
Suzuki G-48
Suzuki Sirius S-56
Suzuki Chromatix SCX-64
Hohner Xpression
Kongsheng Lyra Gold

For the EastTop models I have, and for all the Suzuki models, there are some similarities.  They all have mouthpiece screws that are very close to 3/8" long x 1/16" diameter.  I don't know the threadcount on any of them, but that's not really important in bumper replacement.
The Hohner Xpression has a slightly longer MP screw ... approx. 1/2" long.  It, too, has a diameter of 1/16".
The Kongsheng is a totally different animal!  Let's leave that one out of this discussion.

The job of the bumpers is to cushion the slide as it hits against the MP screws, which keeps the movement of the slide from "clicking" against the screw and causing a distinct noise.  Over time, this movement of the slide against the bumpers cuts/wears the bumper material, and they need to be replaced.  The frequency of replacement varies by use of the slide, force applied to the button, and material used for the bumpers.  The wear and tear on bumpers is obvious when you take the mouthpiece apart for cleaning, and just look at the condition of the bumpers.

Let's look for a minute at the general construction of the area where the MP screws are seated.  Of course, there are two "holes" where the screws are inserted.  There's a through hole in each end of the mouthpiece itself, and a threaded hole in each end of the comb where the screws attach.  The slide sits on top of the comb and one end is attached to the spring.  The mouthpiece fits over the slide and connects to the comb using the two screws.  When properly installed, the slide moves smoothly and quietly, and the mouthpiece provides an air tight seal to the comb so air is directed to the area that makes music, and not leaking out the edges!

You'll also note that at the holes where the screws fit, there is also a "seating" area for the bumpers.  There is a "seating area" on both ends of the mouthpiece, and likewise at both screw holes in the comb.  Those "seating areas" are there to allow the bumpers to fit nicely around the screws without "pinching" and without interfering with the movement of the slide except to cushion it when it hits the screws.  On all the models I looked at, the diameter of that "seating area" is very close to 1/8".  The depth of those "seating areas" varies very slightly from model to model.  The bottom line is:  the diminsions of the bumper material should be such that it fits reasonably snuggly around the screws (diameter approx. 1/16"), fits reasonably snuggly into the "seating areas" (diameter approx. 1/8"), and is a length that allows it to fit into the area between the seating areas on the comb and in the mouthpiece.

For all the EastTop and Suzuki models I looked at, the proper diminsions of the bumpers should be very close to 1/8" OD x 1/16" ID x 5/32" long.  (I know!  How the heck do you cut the material to 5/32"?!)  I use either a sharp Exacto knife or a single edge razor blade to cut the material, and I start a bit long and trim until I get very close to 1/8" long plus a little bit.

How about the material to use?  Well, I haven't fully gotten there yet.  All of the models I looked at came with a clear plastic bumper installed.  EastTop provides a little "spare parts" box that has screws, a spring, and a small amount of bumper material enclosed.  I'm not certain what it's made of, but it works great.  Problem is ... I'm running out!  What to do?

My first attempt was to order some natural latex tubing with 1/8" OD x 1/16" ID.  I got it from Amazon.  First of all, it's VERY hard to cut and maintain the length I want.  Second, it was actually a bit too big in OD, and didn't seat well in the "seating areas".  For me, this type of tubing was not satisfactory.  I'm now awaiting a food grade silicone tubing that's 1/8" OD x 1/16" ID.  I'll let you know if that works better for me.  I'm certain that the actual dimensions will depend on the manufacturer, so it's going to take a little trial and error.  In a real pinch, things like coffee stirrers, ball point pen ink tubes, electrical wire insulation, etc., have been used.  However, they're not good fits and they don't provide the "quietness" of a better material.  I'd only use them in an emergency!

I'm attaching a few pictures that I took to help understand the "nomenclature" that I'm using in this post.
The first photo, labeled Photo 1, shows the screw hole and surrounding "seating area" in the mouthpiece itself.
The second, labeled Photo 2, shows the threaded receiving hole for the screw in the comb, and the surrounding "seating area".
The third, labeled Photo 2, shows the assembled mouthpiece, slide, screw and bumper.  Note the fit of the bumper material is snug around the screw and in the "seating area" of the mouthpiece.  Note also that the bumper material extends above the slide so that it will go into the "seating area" of the comb when installed.  The length of the bumper is critical here because you don't want it to be "squeezed" too much so it causes leakage and problems with slide movement.

I know this is a LOT of stuff!  Probably too much, but it follows my engineering, AR personality! :D

I'll let you know how the silicone material works when I get it and give it a try.  This isn't rocket science, but it does require some care to make your harmonica perform to its best ability.

Age:
I normally cut them "too long" on purpose, then use a razor to shave a "frog hair's" worth of material so that it's still "too long" but doesn't bind. That's the "holy grail" that even the manufacturers aren't fussy enough to pursue.  "Bumper Holy Grail": When that bumper compresses just enough to "get fat," as it can without binding the slide assembly.

This is a feature that the Kongsheng, (that Doug mentioned) seems to have a pretty good handle on, since they use o-rings that should both outlast and out perform the "bumpers" that all the others have been using since the flood. Bravo! (that was a quantum leap on their part, IMO.) I look forward to more solutions that are introduced by the newer, "upstart" manufacturers, since the others are all stuck in the past. Harrumph!

brorat:
OK!  In the "for what it's worth" department ...

I seem to have found a really good material for bumpers.  It works great in ALL of the East Top models I've tried, and in ALL the Suzuki models, too.

It's a pure silicone tubing measuring 1/8" OD x 1/16" ID.  I bought it from Amazon in approximately a 10' length for about $8.  Enough to last my lifetime for sure!   It is "spongy" enough to provide a quiet "bump", it's easy to cut to the right length (I've found that 5/32" is good for me), and it fits into the seating area nicely as well as fitting snugly around the MP screws.

Here's the link on Amazon for any who might want to give it a try:
https://www.amazon.com/dp/B093F6PS53?ref=ppx_yo2ov_dt_b_product_details&th=1

brorat:

--- Quote from: Age on March 18, 2024, 04:36:02 PM ---I normally cut them "too long" on purpose, then use a razor to shave a "frog hair's" worth of material so that it's still "too long" but doesn't bind. That's the "holy grail" that even the manufacturers aren't fussy enough to pursue.  "Bumper Holy Grail": When that bumper compresses just enough to "get fat," as it can without binding the slide assembly.

This is a feature that the Kongsheng, (that Doug mentioned) seems to have a pretty good handle on, since they use o-rings that should both outlast and out perform the "bumpers" that all the others have been using since the flood. Bravo! (that was a quantum leap on their part, IMO.) I look forward to more solutions that are introduced by the newer, "upstart" manufacturers, since the others are all stuck in the past. Harrumph!

--- End quote ---

I love colloquial sayings!  I have a collection of them written down and saved on my computer.  One day in the future, my great-grandkids will get a laugh out of things like:

"As fine as frog's hair"
"As scarce as hen's teeth"
"Happy as a clam"
"Narry a one"
"Fat as a billiken"

SlimHeilpern:

--- Quote from: brorat on March 18, 2024, 10:58:23 AM ---The Kongsheng is a totally different animal!  Let's leave that one out of this discussion.

--- End quote ---

Indeed, and will look forward to your analysis of those bumpers. One interesting thing is that Konsheng includes a little bag of extra rubber/silicone(?) bumper washers with each harmonica.

- Slim

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