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Discussions => Instrument Design, Construction and Repair => Topic started by: Rees on November 07, 2018, 09:04:18 PM

Title: Hohner "Fondo" gasket
Post by: Rees on November 07, 2018, 09:04:18 PM
As many will know, when fitting modern Hohner reedblocks into old Ericas/Pokerworks, etc. a new gasket will be required for the fondo (I shall use the eff word as my dog is Italian ;)  ).
This is a complete pain and involves the use of a surgical scalpel. Did you know that they are made for cutting human flesh?
"Blood on the Fondo" - good tune that.
To come to the point - would it make sense for us fettlers and other interested parties to get these pre-made somewhere?
Someone here must know how to do it.
I'll take 50 for starters.
Title: Re: Hohner "Fondo" gasket
Post by: Theo on November 07, 2018, 09:16:22 PM
No blood on the fondo here! I glue the material in place and then cut the holes using the holes in the woodwork as a guide.  I think it might be hard to get a pre-cut gasket to fit well because the gasket material is necessarily soft and tends to be stretchy.
Title: Re: Hohner "Fondo" gasket
Post by: John MacKenzie (Cugiok) on November 07, 2018, 09:19:06 PM
You need someone with a laser cutter as employed by Olav Bergflodt. They could be cut out by the dozens. I just tried pre cutting one to fit on the reed block, using a punch. It was very satisfactory but the holes didn't fully line up. I put this down to stretching of the material while I worked it. However, as long as air can't migrate from one hole to the next, it should work OK. Time will tell.


Sir John
Title: Re: Hohner "Fondo" gasket
Post by: Winston Smith on November 07, 2018, 09:58:32 PM
I've often wondered if neoprene "O" rings wouldn't work just as well (or better?) as they seem to be taking the automotive world by storm these past (I was going to say "few" before I realised that I've been right out of it for 15 years or so!) years?
Title: Re: Hohner "Fondo" gasket
Post by: John MacKenzie (Cugiok) on November 07, 2018, 10:19:16 PM
I have pondered the use of a rubber/plastic washer with a L shaped profile, that pops into the holes. Can't see why it wouldn't work.

SJ
Title: Re: Hohner "Fondo" gasket
Post by: Rees on November 07, 2018, 10:56:00 PM
I have pondered the use of a rubber/plastic washer with a L shaped profile, that pops into the holes. Can't see why it wouldn't work.

SJ

Good idea although it would make the holes slightly smaller which may affect the sound.
Title: Re: Hohner "Fondo" gasket
Post by: Rees on November 07, 2018, 10:57:23 PM
No blood on the fondo here! I glue the material in place and then cut the holes using the holes in the woodwork as a guide.  I think it might be hard to get a pre-cut gasket to fit well because the gasket material is necessarily soft and tends to be stretchy.

I do the same thing but always end up with raggety holes and often a few piercings :(
Title: Re: Hohner "Fondo" gasket
Post by: Rees on November 07, 2018, 10:58:38 PM
Can a laser cut olovisc without setting it on fire?
Title: Re: Hohner "Fondo" gasket
Post by: diatonix on November 07, 2018, 11:45:38 PM
Can a laser cut olovisc without setting it on fire?

Thin leather, olovisc and similar materials can be cut with low power and high speed. The laser is so fast that there is simply no time to ignite. In addition, most machines are equipped with "air assist", which will very efficiently prevent flaming.
Title: Re: Hohner "Fondo" gasket
Post by: mory on November 08, 2018, 07:34:22 AM
A self made curved blade formed from a section of tube the right size might help, if you sharpen it on the inside of the bore you'd have no problem damaging the sides of the sound board hole and a sharp point would allow easy penetration. An old punch the right size with the end grind removed and a piece taken out length ways works fine and holds it edge I used to use this making gaskets to get the holes in the right place. It works best if it's slightly less than half the tube diameter. AtB mory
Title: Re: Hohner "Fondo" gasket
Post by: RogerT on November 08, 2018, 07:54:31 AM
You could try https://www.cacornish.co.uk who make all sorts of Concertina leather bits. You could give em your spec and see what they come up with (leather so thick, wiv 'oles here, here and here'). They are pretty accommodating (speak to Lynda) though it won’t necessarily be cheap.
Title: Re: Hohner "Fondo" gasket
Post by: Theo on November 08, 2018, 08:35:29 AM
No blood on the fondo here! I glue the material in place and then cut the holes using the holes in the woodwork as a guide.  I think it might be hard to get a pre-cut gasket to fit well because the gasket material is necessarily soft and tends to be stretchy.

I do the same thing but always end up with raggety holes and often a few piercings :(

I can do a training session.  ;D ;D

I always use a new scalpel blade.   The best blade is a straight edge one, I'm using a 10A at the moment, but I think there is another that is narrower which could be better.   I don't use the self adhesive olovisc, but the woven type with a felted nap on one side.  It cuts more easily than the self adhesive.  I can send you a bit to try.
Title: Re: Hohner "Fondo" gasket
Post by: RogerT on November 08, 2018, 09:12:16 AM
..and where do you get this other material Theo?
Title: Re: Hohner "Fondo" gasket
Post by: Rees on November 08, 2018, 09:13:47 AM
[
I can do a training session.  ;D ;D

I always use a new scalpel blade.   The best blade is a straight edge one, I'm using a 10A at the moment, but I think there is another that is narrower which could be better.   I don't use the self adhesive olovisc, but the woven type with a felted nap on one side.  It cuts more easily than the self adhesive.  I can send you a bit to try.

Thank you Nurse.
Yes, I always use a new 10A blade.
Most grateful if you could send me a bit of that stuff. Is it from Charlie?
Title: Re: Hohner "Fondo" gasket
Post by: John MacKenzie (Cugiok) on November 08, 2018, 09:33:29 AM
Differently shaped/angled scalpel blades might help. I was wondering about trying a 12, with the curved blade, edged on the inside of the curve. Has anybody gone down this route?

Sir John
Title: Re: Hohner "Fondo" gasket
Post by: howard mitchell on November 08, 2018, 10:04:10 AM
Hi Rees ,
I have access to a laser cutter at my local community workshop, Melton Space.
If you can send me the dimensions required and a sample of material, I can quickly draw it up and cut a few test pieces.

Mitch
Title: Re: Hohner "Fondo" gasket
Post by: Graham W on November 08, 2018, 10:26:01 AM

[/quote

I always use a new scalpel blade.   The best blade is a straight edge one, I'm using a 10A at the moment, but I think there is another that is narrower which could be better.
[/quote]

No.11 has a longer slimmer tip.
Title: Re: Hohner "Fondo" gasket
Post by: Theo on November 08, 2018, 12:05:49 PM
[
I can do a training session.  ;D ;D

I always use a new scalpel blade.   The best blade is a straight edge one, I'm using a 10A at the moment, but I think there is another that is narrower which could be better.   I don't use the self adhesive olovisc, but the woven type with a felted nap on one side.  It cuts more easily than the self adhesive.  I can send you a bit to try.

Thank you Nurse.
Yes, I always use a new 10A blade.
Most grateful if you could send me a bit of that stuff. Is it from Charlie?

From Carini OLOVISC 7/10 H 140 NON ADESIVO

I'll send you a free sample!
Title: Re: Hohner "Fondo" gasket
Post by: Rees on November 08, 2018, 02:05:17 PM
[
I can do a training session.  ;D ;D

I always use a new scalpel blade.   The best blade is a straight edge one, I'm using a 10A at the moment, but I think there is another that is narrower which could be better.   I don't use the self adhesive olovisc, but the woven type with a felted nap on one side.  It cuts more easily than the self adhesive.  I can send you a bit to try.

Thank you Nurse.
Yes, I always use a new 10A blade.
Most grateful if you could send me a bit of that stuff. Is it from Charlie?

From Carini OLOVISC 7/10 H 140 NON ADESIVO

I'll send you a free sample!

Grazie mille .......
Title: Re: Hohner "Fondo" gasket
Post by: tirpous on November 08, 2018, 02:08:45 PM
Quote
From Carini OLOVISC 7/10 H 140 NON ADESIVO

I'll send you a free sample!

I want one too !!   ;D
Just kidding.  Thanks to all for sharing information !
Title: Re: Hohner "Fondo" gasket
Post by: Rees on November 08, 2018, 02:13:06 PM
Hi Rees ,
I have access to a laser cutter at my local community workshop, Melton Space.
If you can send me the dimensions required and a sample of material, I can quickly draw it up and cut a few test pieces.

Mitch

Thanks Howard.
I have a few jobs to complete (as it ever was) and then I shall settle down to some draughtsmanship. I'm also compiling some diagrams for laser cutting of fondos in GL1 plywood 1.5mm and 3mm.
Title: Re: Hohner "Fondo" gasket
Post by: howard mitchell on November 08, 2018, 02:45:12 PM
Hi Rees ,
I have access to a laser cutter at my local community workshop, Melton Space.
If you can send me the dimensions required and a sample of material, I can quickly draw it up and cut a few test pieces.

Mitch

Thanks Howard.
I have a few jobs to complete (as it ever was) and then I shall settle down to some draughtsmanship. I'm also compiling some diagrams for laser cutting of fondos in GL1 plywood 1.5mm and 3mm.

We can certainly cut 3mm ply.  Here's a picture of a tiered pencil holder recently made out of 3mm and a box for the spare left hand of my Sagne made from 8mm.
Title: Re: Hohner "Fondo" gasket
Post by: Rees on November 08, 2018, 03:13:48 PM
Ideal. I'll be in touch dreckly.
Title: Re: Hohner "Fondo" gasket
Post by: Rees on November 09, 2018, 12:38:10 AM
Yes, this has been really good. Thank you all for your help and onwards we shall go. :)
Title: Re: Hohner "Fondo" gasket
Post by: RogerT on November 09, 2018, 07:49:11 AM
What do you do your draughtsmanship with Rees?
Title: Re: Hohner "Fondo" gasket
Post by: Rees on November 09, 2018, 02:40:16 PM
What do you do your draughtsmanship with Rees?

A pencil .....
Title: Re: Hohner "Fondo" gasket
Post by: John MacKenzie (Cugiok) on November 09, 2018, 02:42:20 PM
On a slate? (Welsh of course)

SJ
Title: Re: Hohner "Fondo" gasket
Post by: RogerT on November 09, 2018, 05:17:59 PM
What do you do your draughtsmanship with Rees?

A pencil .....
I see. And how does this get converted to instructions for a laser cutter?
Title: Re: Hohner "Fondo" gasket
Post by: Broadland Boy on November 10, 2018, 12:25:59 AM
You may have different 'staff' to Rees, Roger  ;)
Title: Re: Hohner "Fondo" gasket
Post by: Rees on November 10, 2018, 01:03:06 AM
CAD-man cometh and does a magic thing beyond my ken :)
Title: Re: Hohner "Fondo" gasket
Post by: george garside on November 10, 2018, 09:25:37 AM
and mine!

george
Title: Re: Hohner "Fondo" gasket
Post by: howard mitchell on November 10, 2018, 10:27:36 AM
What do you do your draughtsmanship with Rees?

A pencil .....
I see. And how does this get converted to instructions for a laser cutter?

If it helps, we use Thunder Laser which has some 2D CAD facilities built in and sends GCode directly to the laser cutter.
It can separate parts of the drawing into layers and tell the cutter which parts to do first.  You can also set speed and power for each layer so you can, for instance, etch a logo and then cut around it.
It can also import almost any graphic files in raster or vector formats.
I use Inkscape or Adobe Illustrator to draw new plans.

We also have a 3D printer and we're working on a CNC router. Both require 3D CAD - FreeCAD or Autodesk Fusion 360 and then appropriate controllers, Repetier for the 3D printer which does all the slicing and temperature control, Fusion does tool paths for the router and GRBL and GCode Sender do the machine control.

Mitch
Title: Re: Hohner "Fondo" gasket
Post by: Winston Smith on November 10, 2018, 10:45:14 AM
Back when dinosaurs ruled the planet (or so it seems, from Mitch's new-fangled explanation) I really was a dab-hand with an oxy-acetylene cutting torch, but I suppose one of those wouldn't be quite so neat as these space-age gizmos!
The ingenuity of man (or woman) knows no bounds!