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Author Topic: promising method of flexible pallet connection  (Read 771 times)

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hickory-wind

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promising method of flexible pallet connection
« on: December 19, 2022, 04:06:25 PM »

Hohner’s method of attaching pallets to lever arms has drawbacks. There are many instruments that arrive in my shop with leaking pallets- both treble and bass sides. This is due to the pallet not lying flat against the “sound board”. (pic 1- Preciosa with multiple leaking pallets) The pallet is hitting on an edge or even a corner only and the rigid connection doesn’t allow the pallet to lie flat and close all the way. Even if restoring with flexible hot glue, there remains very little flexibility in the pallet connection since the groove width is tight on the lever and the pallet groove is flat bottomed as is the portion of stamped steel lever arm that rests on the groove bottom. I have been experimenting with using a ball pivot at the bottom of the pallet groove with promising results. (pic 2 with extra ball to the right on my hand)

First the pallet groove is widened slightly to allow some rotation around the axis of the groove/lever. I have a series of small files for this. (pic 3) Guitar nut files are good for this. I then embed a small diameter metal ball partially into the bottom of the pallet at its center. This provides a 2-axis pivot point. Combined with hot glue this provides a good amount of flexibility in both left/right and top/bottom rotations.
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hickory-wind

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Re: promising method of flexible pallet connection
« Reply #1 on: December 19, 2022, 04:08:37 PM »

To test this, I used an old Erica shell and prepared three test pallets. All were cleaned and had the groove widened just a bit. I then inserted a 0.5mm shim under the tops of the pallets (pic 4) to purposely cause an exaggerated tilt condition before gluing. The left pallet was glued to the lever using a rigid glue (Bondic UV cure). The second pallet had the ball pivot and then was secured with hot glue. The right pallet didn’t have the ball but hot glue was used.

The rigid connection retained the full tilt and leaked a lot. The hot glue joint (on the right pic 5) partially closed but still leaked some. The ball pivot joint lay completely flat on the sound board and sealed well.

Here is a link to some video (starting at the discussion point) showing the results:
https://youtu.be/jbEKjobjXis?t=51

I am still experimenting on how much hot glue to use but I find the approach very promising. I found the loose balls at a bearing supplier (VBX.com) here in the states but there should be an equivalent somewhere in Europe. A lifetime supply (1000) cost less than $10 and fits in a tiny bag (pic 6).

Scott
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Theo

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Re: promising method of flexible pallet connection
« Reply #2 on: December 19, 2022, 04:20:58 PM »

Ingenious!  Always good to see a controlled experiment.
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Theo Gibb - Gateshead UK

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Rog

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Re: promising method of flexible pallet connection
« Reply #3 on: December 19, 2022, 04:52:46 PM »

Have you found that widening the groove on the pallet so that it can gimbal slightly before you glue, doesn’t work?

hickory-wind

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Re: promising method of flexible pallet connection
« Reply #4 on: December 19, 2022, 05:36:56 PM »

The ball pivot has more effect on the top to bottom gimbaling than the left to right. The flat groove bottom and long flat portion of the steel lever really tends to limit motion in that axis.

Scott
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chris hall

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Re: promising method of flexible pallet connection
« Reply #5 on: December 20, 2022, 03:12:53 PM »

interesting idea. what diameter bearings? ...and what glue gun and make of glue?...ive been trying different hot glues and glue guns and am yet to find the ideal combination. the latest one i bought is a tec 305 12mm with a 1.25mm nozzle......made a neat job but not holding as well as id like.
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John MacKenzie (Cugiok)

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Kimric Smythe

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Re: promising method of flexible pallet connection
« Reply #7 on: December 21, 2022, 07:30:17 AM »

On old piano accordions with larger pallets i often find a little chip of celluloid in the middle of the slot on the palette , this is similar to your bearing. Helps to make sure that the pressure is in the center of the palette. Makes sure it is level before gluing or waxing.
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bellowpin

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Re: promising method of flexible pallet connection
« Reply #8 on: December 21, 2022, 05:26:35 PM »



I am still experimenting on how much hot glue to use but I find the approach very promising. I found the loose balls at a bearing supplier (VBX.com) here in the states but there should be an equivalent somewhere in Europe. A lifetime supply (1000) cost less than $10 and fits in a tiny bag (pic 6).

Scott
      the ball bearings remind me of shotgun pellets. would a lead pellet work?  it only has to rock slightly . alternative cartridge types that are lead free, such as steel or bismuth are being made . one cartridge taken apart would suppy dozon's of balls . many sizes to choose from, number 6. or 7. maybe.
     interesting idea , well done.     
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Theo

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Re: promising method of flexible pallet connection
« Reply #9 on: December 21, 2022, 06:01:10 PM »

Seems like a lot of trouble when steel balls (for bearings) are cheap and readily available. For example https://www.bearingshopuk.co.uk/1mm-loose-steel-balls/
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Theo Gibb - Gateshead UK

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hickory-wind

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Re: promising method of flexible pallet connection
« Reply #10 on: December 21, 2022, 08:16:33 PM »

I've been using the 1.4mm bronze balls as they just rub the walls of the slot which hold them in place. 1mm don't fill the slot so could move during assembly. The 1.5mm steel haven't arrived yet.

I mostly use a 100watt Surebonder glue gun. Slow to warm up but has replaceable nozzles. The one in the picture reaches down between the metal rod clap-trap on the bass/chord side pretty well. The glue sticks I use are nice and mechanically flexible installed but are obnoxiously stringy during use. Any suggestions?

Scott
« Last Edit: December 21, 2022, 10:33:27 PM by hickory-wind »
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diatonix

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Re: promising method of flexible pallet connection
« Reply #11 on: December 21, 2022, 09:09:15 PM »

A small piece of leather (usually cut from a leather valve) placed in the center of the groove does the same trick. I use it on all my pallets. By using thicker or thinner pieces it is also very easy to make minor adjustments to the button travel/height/alignment without having to bend the lever.
« Last Edit: December 21, 2022, 09:35:16 PM by diatonix »
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chris hall

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Re: promising method of flexible pallet connection
« Reply #12 on: December 22, 2022, 03:22:08 PM »

I've been using the 1.4mm bronze balls as they just rub the walls of the slot which hold them in place. 1mm don't fill the slot so could move during assembly. The 1.5mm steel haven't arrived yet.

I mostly use a 100watt Surebonder glue gun. Slow to warm up but has replaceable nozzles. The one in the picture reaches down between the metal rod clap-trap on the bass/chord side pretty well. The glue sticks I use are nice and mechanically flexible installed but are obnoxiously stringy during use. Any suggestions?

Scott

cheers scott..my glue gun is very similar but 140 watts so i guess its ok. I'll try going back to the nozzle it came with (2mm) instead of the 1.2mm nozzle i tried. I'll try a different glue stick. it seems there are many types. I have some 1.5mm ball bearings on the way to give the bearing idea a try on a 114 hohner.
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