Unusual Clamping Issue

Hello HSMers, I'm trying to figure out a better way to secure the endpin of a standup bass. At the bottom of the instrument is a wood socket with a steel collar and a thumb screw. There is a hole through the collar which holds a rod. If the rod is metal the collar/thumb screw works well enough, but many bass players think that a wood endpin sounds better. None of the typical approaches work very well for wood, so I am thinking of drilling a 5/8" hole (the pin diameter) orthogonally into a piece of 7/8 aluminum round, slotting most of the length in the same axis as the hole center, and drilling a second hole into the round, through the slot, near the open end, and using a thumb screw to draw the halves together. Look at the drawing (Sorry, my CAD skills and software are a bit primitive):

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I would set the clamp into the wood socket, and get rid of the metal collar. Me thinks this would give good clamping pressure as well as lots of surface area so as to protect the wood peg. Would 6061 aluminum be a good choice? I want to use something light and easy to machine if possible. Any criticism of the design? I want to explore all possibilities before I start spending money, as I don't have the tools to do this myself. Thanks for all advice. Robobass

Reply to
lostfrom68jay
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Why not use a wooden pin with a metal end?

Reply to
jtaylor

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Looks ok except for the slot going into the other side of the 5/8" hole. Since it has sharp inside corners, it will be a stress riser, meaning, if a crack starts, that's where it will start. The clamp should have enough flex to work without slotting the other side of the hole.

Fred +2c

Reply to
ff

My question is how you set your "clamp" into the bottom of your bass without it buzzing like crazy which is probably why people like the wooden pegs in the first place. ( I used to do similar things to create annoying buzzes intentionally when I played in my high school orchestra which is why the conductor used to whack me on the head with the big end of his baton).

Several of the Cello's I played had a tapered socket into which we would insert a tapered wooden peg. The wooden peg had an adjustable metal pin in the end to allow comfortable use by short or tall players but you could do the same with a fixed length 100% wood peg.

Your CAD skills are adequate for the task.

Carl

Reply to
Carl

wrote: (clip) If the rod is metal the collar/thumb screw works well enough, but many bass players think that a wood endpin sounds better. (clip) ^^^^^^^^^^^^^^^^^^^ It may be purely psychological. Why don't you try some blind A-B tests to see whether anyone can really tell the difference. If it turns out to be all in their heads, just wrap the metal leg in wood-grain Contact paper.

If there is a discernible difference, then I suggest turning a wooden leg with a shoulder, that can be shoved in without clamping. Need adjustable? Make an assortment of legs. Don't have a lathe? I'll do it for you if you pay for the dowels and postage.

Reply to
Leo Lichtman

Robobass

I had a similar issue repairing a wooden music stand that needed a better clamp (wooden screws look good but don't last). If you used a threaded thumb screw it ate the wood. What I did was line the hole the wooden shaft went through with thin wall brass tubing and cut a flap (3 sides of a rectangle) into it where the thumb screw came through. That way the screw bore on metal and the flap clamped the rod over a large enough area that the wood didn't crush. That was ~10 years back and the last time I checked, the music stand was well used but the shaft was still unmarked.

I should also say that I used undersized tubing, slotted it down the back, away from the flap, and sprung it into place. Bit into the wood and hasn't moved a jot.

Jim

PS By the way, Leo, probably what the bass players notice is a difference in the resonance of the instrument. Wood (or plastic) decouples the bass from the floor. Metal does not so they get reflections off the surface and feel different modes (don't underestimate how sensitive musicians are to details like that). But a metal pin with a wood / plastic end should do the same.

Reply to
Jim McGill

lostfrom68jay wrote: ...> I'm trying to figure out a better way to secure the endpin of a

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With a round hole drilled across a round, you'll have sharp edges at the outer edges of the drilled hole. Why not use rectangular bar instead?

If you make it of steel instead of aluminum, you could thread one side of the second hole and have one less part to fiddle with when adjusting how much of the endpin sticks out. I think the size should be about the same whether you make it with steel or aluminum; if you were to go with acetal (eg Delrin) or polycarbonate (eg Lexan) allow a little more thickness and width. Eg, a piece of Lexan about

2" long, 1.25" wide, 1" thick.
Reply to
James Waldby

Why not use rectangular bar

Well, I want to set the clamp into the wood socket. Round holes are easier to drill than square ones.

I was planning to thread the bottom half of the aluminum. There should be enough turns to keep it from stripping. I think the size should

I was thinking about Delrin. I thought the diameter could be about the same, but it should be longer. Of course I would need to insert a steel nut.

Two more questions:

1: Which Alu alloy is most resistant to stress hardening i.e. can be bent a bit without becomming brittle? 2: Does anyone know of a sawmill or other wood supply facility that can cut dowels from unusual woods. I'm thinking about laminated bamboo and unusual hardwoods for this project, but I can't pay someone to cut them all on a wood lathe! Robobass
Reply to
lostfrom68jay

I haven't done this on anything bigger in diameter than a violin sound post- which is made with spruce rather than hardwood, but here's how I've made sound posts.

Cut the part to a close rectangular size to your finished diameter. Plane, saw, or whittle the corners off till it's almost round. Drive the whittled pin through a series of holes of decreasing size in a piece of metal. The piece of metal I use is about 1/8" thick. It doesn't have to be hardened. I don't know if there's a better way, but this has worked for me. If you have a drill press, you could probaby rig up a contraption to turn a square peg in the chuck with a cutter and some sort of support on the drill press table.

RWL

Reply to
geolane_NOSPAM_

Some of the sockets have a cork liner. Buzzing is an issue, but mostly not a problem with wood or metal pins. I haven't exactly worked out whether it will be a problem with my design, I'll have to make a model to find out!

Basses really need a large length adjustment capacity. If you always stand, maybe you could have a fixed length, but classical players generally sit, and want to use the provided stools rather than carry their own along. The stools are often not very adjustable.

rob

Reply to
lostfrom68jay

Some of the sockets have a cork liner. Buzzing is an issue, but mostly not a problem with wood or metal pins. I haven't exactly worked out whether it will be a problem with my design, I'll have to make a model to find out!

Basses really need a large length adjustment capacity. If you always stand, maybe you could have a fixed length, but classical players generally sit, and want to use the provided stools rather than carry their own along. The stools are often not very adjustable.

Robobass

Reply to
lostfrom68jay

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