Author Topic: Question for Vern - improving air-tightness (Read 1223 times)

Bluesy · « **on:** June 19, 2012, 07:58:38 PM »

Vern:
I have a tech. question on making a Toots MT or a 270 more air-tight. Somewhere, I think, you mentioned .002" clearance for the slide as the optimum clearance. Am I right in remembering that the slide sits in a sort of shallow u-channel "slide carriage" that has 4 tabs on it that fit into notches on the overlying MP plate making a sort of sandwich of 1) slide carriage, 2) slide, and 3) overlying plate?
And that to improve air-tightness we have to reduce the clearance between the top of the slide carriage flanges and the surface of the slide that lies within? In fact, reduce it to .002" with a feeler gauge slipped under the slide itself? (If not there, where? And how?)
And it goes without saying that we must be careful to not file down the tabs along with the top of the slide carriage flanges?
Did you make a tool to do this semi-automatically? Would draw-filing with a fine machine file accomplish the same thing, then finishing off the top of the flanges with crocus cloth?
Have I got the anatomy right? Do I understand your method of increasing air-tightness in 270s, 260's and Toots MTs?

Many thanks for responding!

Tom C/

Vern · « **Reply #1 on:** June 19, 2012, 08:53:33 PM »

You have the essentials right. I did make a tool that used a shim under the slide and a plane that you push along on top of the slide with blades sticking out the sides to shave the U-channel flanges. That way the slide was protected from the cutting operation. Both Schackner's and Tate's books describe how to do this with a file.

I corresponded with Timler about it and I know that he (using his own tools) performed the operation on at least some of the custom 270-like harps that he sold. Now that he is with Hohner, maybe he will include it in the manufacture of new harps.

To check this clearance, place the slide in the U-channel and bridge a depth micrometer across the flanges. I have found 270s with clearances of up to .007" ....waaay too much!

I made several of these tools and gave them to harmonica techs so that people like you would have a resource for this operation. I am not sure what the techs thought of the tool or whether or not they used it. I'm not going to give their names here but they are techs that you know and some post on Slidemeister. Ask around and maybe you can find someone to do it for you.

IMO, this, replacement of sticking-popping valves, and waxing the reedplates under the valves will greatly improve a 270. That said, I would never buy a new harmonica with reedplates nailed on a wooden comb.

Vern

Vern · « **Reply #2 on:** June 19, 2012, 09:48:44 PM »

I found some more information about the tool lurking in my computer. I was working on this about 2009.

Here is a picture of the scraper and instructions how to use it.

Vern

pyro_fire60099 · « **Reply #3 on:** June 20, 2012, 12:39:15 AM »

Nice tool, good concept Vern

Bluesy · « **Reply #4 on:** June 20, 2012, 05:34:07 AM »

Thank you, Vern. I can reduce the clearances myself. I spent part of my youth as a machinist's apprentice. Draw-filing will do the trick, and neatly.
I believe that I read in a previous post of yours about a "homemade" shim to place under the slide when it's in the slide-carriage that you said was about 0.002" thick. Remember what it was? Maybe some layers of aluminum foil?
I see in your photo that you screw the u-channel on to a block to stabilize it for filing.

Tom//

Vern · « **Reply #5 on:** June 20, 2012, 10:01:31 AM »

Providing that you avoid damaging the slide, filing should be OK. That is what Schackner and Tate describe.

The 0.002" shim that I used was SS shim stock from McMaster Carr. http://www.mcmaster.com/ Plastic shim stock or any film (or even paper) of the proper thickness ought to work.

Because scraping requires substantial force, screwing the U-channel and slide to a block is necessary. Screwing the block to the workbench or holding it in a vise is also helpful. In subsequent versions of the tool, the block was bigger.

Vern

A.J.Fedor · « **Reply #6 on:** June 25, 2012, 07:03:11 PM »

I have one of Vern's Stainless Steel 270s with the super tight slide assembly and Gardnerized reed plates. Wow! The only problem I have with it (which is really no problem when compared to the performance of the thing) is that when I pick it up after two just days of not playing, the slide is stuck. Just a few drops of water in the button end and it's ready to rock! It's the most powerful 270 I've ever played!

Gnarly He Man · « **Reply #7 on:** June 25, 2012, 09:28:11 PM »

Yup--a slide which is more airtight will do that.
Guess it's not watertight tho . . .

Bluesy · « **Reply #8 on:** June 26, 2012, 01:37:09 PM »

Note to Vern:
Did it Vern! Disassembled the MP assembly on my Mellow Tone, which was kind of leaky around the bottom, measured the thickness of kitchen aluminum foil with a digital calipers I have lying around the place (0.001"), cut 2 strips to fit inside the slide carrier, pressed the slide on top of them and took a look.
The top of the U-channel sides were both too high, one side worse than the other, and different in height end-to-end - strictly a machine-made harp with no handwork, I guess.
I draw-filed both flanges to the level of the slide. For those who don't know about draw-filing, it's a method of filing metal that produces very accurate results; you lay the file crossways on the work - picture a cross, the vertical member being the piece to be filed and the cross member being the file lying on top of it, then move the file back and forth along the long axis of the vertical member of the "cross". This allows very slow and predictable reduction of material. I worked as an aircraft die maker for a while in my mis-spent youth. We made rubber-press form dies for fighter plane and helicopter parts.
When I filed it down to the level of the slide (took some courage), I polished my work with crocus cloth. No Butcher's wax on hand and rather anxious to see what I'd ruined, so I washed everything under soapy water and re-assembled the Toots.
Worked perfectly! Now the harmonica is nice and tight! Maybe I'll go into business; "Air-tight Tommy!"
Anyway, thanks for your encouragement, Vern.
BTW, I didn't fasten the work down as you show in your photos. Draw filing exerts so little force on the piece that I just steadied the work with my left hand and filed with my right. Did the full length, minus the locating bosses of course.

Bluesy/

Grizzly · « **Reply #9 on:** June 26, 2012, 03:05:24 PM »

Right handed filing? I couldn't do that! (Then, I'm left handed.

)

Nice thing about draw filing is handedness doesn't really matter. I draw file silver to get a smooth surface, less now than when I started out making flutes. I got better with grinding wheels. NOT recommended for this operation, though!

Tom

smojoe · « **Reply #10 on:** June 26, 2012, 05:14:00 PM »

Draw filing a slide over bridger u-channel will never be as touchy as draw filing a cornea. Acqueous humor actually isn't funny.

s-j (Now I shout it from the tower of Pizza, even told the famous Mona Lisa..and now my hearts an open door, and my secret love's no secret any more.)

Sean · « **Reply #11 on:** June 26, 2012, 05:43:07 PM »

Bluesy,

How about a detailed how-to article in Harmonica Happenings? That would help the slow students such as me understand how to do what you are talking about. Include plenty of pictures, please.

Sean

Vern · « **Reply #12 on:** June 28, 2012, 09:06:36 AM »

Quote from: Bluesy on June 26, 2012, 01:37:09 PM

Note to Vern:
Did it Vern! ..........
........The top of the U-channel sides were both too high, one side worse than the other, and different in height end-to-end - strictly a machine-made harp with no handwork, I guess...................

Bluesy/

Congratulations. It can be done with careful hand work. The only real advantage of my special tool is that it could be a bit faster and it requires less skill to avoid damaging the slide.

Hohner's U-bending process doesn't produce consistent flange heights. They must allow enough clearance for the worst-case result to avoid binding. This often results in excessive slide clearance. They need another machine operation to set the correct flange height after bending the U-channel.

Vern

Grizzly · « **Reply #13 on:** June 28, 2012, 10:00:51 AM »

…or eliminate it altogether, as they have with the 280 and, apparently, with the Discovery. Suzuki went to a two-piece a couple of years ago.

Tom

Jimmy Halfnote · « **Reply #14 on:** June 28, 2012, 02:55:04 PM »

That 270 top plate with the flanges, is a problem for the mouthpiece assembly, but
it is not the flanges that i have had the biggest problem with, that is an easy enough fix , once done several times, and of course the slide tightened up makes a difference. My biggest headache has always been, the TOP of this plate, the surface that mates with the mouthpiece itself. On mostly all my 270's the top surface of the flanged plate is proud at both edges , along it's length ( where it is rolled down).
This is NOT an easy fix, and for me it is every bit as important as filing the flanges to prevent slide leakage. ( As is levelling the reedplates and comb ). In isolation , to tighten up the slide, will not cure every air loss, but it is a good start.

jh.

Bluesy · « **Reply #15 on:** June 28, 2012, 08:03:14 PM »

Quote from: Jimmy Halfnote on June 28, 2012, 02:55:04 PM

That 270 top plate with the flanges, is a problem for the mouthpiece assembly, but
it is not the flanges that i have had the biggest problem with, that is an easy enough fix , once done several times, and of course the slide tightened up makes a difference. My biggest headache has always been, the TOP of this plate, the surface that mates with the mouthpiece itself. On mostly all my 270's the top surface of the flanged plate is proud at both edges , along it's length ( where it is rolled down).
This is NOT an easy fix, and for me it is every bit as important as filing the flanges to prevent slide leakage. ( As is levelling the reedplates and comb ). In isolation , to tighten up the slide, will not cure every air loss, but it is a good start.

jh.

Jimmy, could you be a little more specific? I know that 'proud' means the part in question is higher than the surrounding parts, but what part of the U-channel slide carrier exactly are you talking about? Is it the side in which the slide lies, or is it the other side? And if so, where is it "proud"? Which is the "top surface"? In my Hohners, the U-channel lies with it's "cavity", so to speak, facing you as you play.

TomC/

Jimmy Halfnote · « **Reply #16 on:** June 28, 2012, 11:14:09 PM »

Like i said Tom, the surface that mates with the mouthpiece, what does the mouthpiece sit on ? Right , that is the one .

jh.

Jimmy Halfnote · « **Reply #17 on:** June 29, 2012, 06:42:04 AM »

Okay , since i am stuck with the weather again. Here are a couple of not too difficult improvements i have found to work.
Throw away the four spiked cover/ plate spacers, they are pretty useless anyway, use the holes for them in the plates as guides, then drill through the plates and comb, use a drill size of approx. 1.5 mil dia., now insert nuts and bolts of suitable dimensions, about the size of the ones used for the covers. Make two spacers ( wood will do ), slightly longer than the originals, you want to lever pressure on to the front of the covers that press on to the plates ( have these in place while the cover screws are loose, then tighten the cover screws).
With the two bolts at the bottom,plus the cover screws tight with the new spacers putting pressure from the covers on the plates near the mouthpiece, then the nails have far less of a burden. Also the two nuts and bolts make dismantling and assembling far, far easier, a dawdle in comparison.

jh.

Dean Taylor · « **Reply #18 on:** July 28, 2012, 05:12:00 PM »

hello players...

Regarding the slide mechanism, a venerable player has advised the use of a spray paint with teflon in it--used by gun enthusiasts.

As explained to me, the paint is applied in repeated layers (possibly twenty!) building up the slide to mate better to its carrier. This corrects the air leakage issue as well as addressing the possibility of binding/sticking. Is this protocol still in use? If it is, please clarify a bit more as to the proper technique--a bit hazy on that...

The draw filing method seems more effective. How would one address the air leaks in a Super 64X slide mechanism--same method? Are combs ever sanded to mate better with the reedplates--or is that an issue proper to diatonics?

Best,

Dean

A.J.Fedor · « **Reply #19 on:** July 28, 2012, 06:09:09 PM »

Yeah, I've been looking for some good Teflon spay for a hundred years. Please lemme know when you find some.

@ge

Dean Taylor · « **Reply #20 on:** July 28, 2012, 06:16:42 PM »

hi

here is the link--I hope it helps:

http://is.gd/u3gCfC

The idea of spraying this on left me cold--since it will abrade and probably be ingested..alarmist? Possibly...

Best,

Dean

reeds64 · « **Reply #21 on:** July 28, 2012, 06:51:19 PM »

I'm the guy who suggested the paint. The manufacturer says it contains Teflon, but there is not enough Teflon in it to make it slippery. Just do not bother repeating the word Teflon when referring to this paint, or you will get people hoping and thinking about a quality that the paint does not have. The nice quality of this paint is that it air dries so that it is hard enough to be solid, but soft enough that you can sand it with 1000 grit sandpaper.

reeds64 · « **Reply #22 on:** July 28, 2012, 06:57:43 PM »

Worry about ingesting a t i n y amount of the paint? If we breathe the air in a city, breathe the air downwind from a freeway, paint our kitchen, etc. we will poison ourselves to some extent. If we scratch our eyes or pick our teeth, do we pause to wonder where our hands have been all day?

reeds64 · « **Reply #23 on:** July 28, 2012, 07:02:15 PM »

Sanding the comb to make it mate better with the reedplate is standard protocol. Lay sandpaper on flat sheet of glass or whatever you have that is very flat. Lightly, lightly, lightly sand the comb.

While you are at it, temporarily remove the spring and lightly, lightly, lightly sand the surface of the comb that the backplate is against. Put the sandpaper on a flat surface, grit side up, and move the comb across the sandpaper. Your purpose is to remove any imperfection of the comb that is sticking up. Err on the side of sanding too little, rather than too much, so that you do not change the overall flatness of the surface.

News:

Author Topic: Question for Vern - improving air-tightness (Read 1223 times)