DIY oak unipivot tonearm

[cactuscowboy]

Originally Posted by The Space Egg Corp

Hi Cactus

My father was an engineer in materials and electronics and a big music lover.
He was very much a DIYer in a lot of things (cars, furniture, photography etc. not diyAudio though), and I for sure got the make it yourself bug from him and my grandfather who made his own cameras.

"Make your tonearm out of wood son, t'will be much better."

I think I would conceptualy have to agree.

I have at home a set of well made commercial wind chimes.
They have a nice decay to them, but make no audible sound unless struck by the chimes mallet (not strictly true actualy, you can get a slight organ pipe/flute effect if the wind happens to catch them right).

I thought it would be interesting to make some wind chimes with a much lower frequency and longer decay.
Three chimes were made each 182cm long, in 1 1/2", 2 1/4" & 3 1/2" diameter aluminium alloy tube.
With holes for a hanging wire 1/4 way down the tubes, which I figure is a ideal distance to get them resonating nicely, very low, long decay frequencys were produced easily.

Thought I'd have a go at a cowbell and woodblock next, forgeting the cowbell for now, the wood block proved impossible to get any amount of decent resonance or sound from despite trying various shapes deliberately designed to try and promote this.

Anyway to cut a long story short, if you hang a 2x4 a dowel or a log next to the ally tube wind chimes and give them a bash with a mallet, what do you get resonance or sound wise,

THE SWEET SOUND OF NOTHING.

Cheers Simon...

Hello Simon,

My decision to use wood was based on simple practicality. I have an assortment of scrap wood, the basic tools to form it, and it just seemed a good choice at the time.

One thing that struck me about this oak unipivot tonearm is how 'quiet' it is, quiet in the sense that tapping it vigorously produces little to no ill effect through stylus/cartridge/amp/speakers. I think oak was a good choice, but it's got me wondering what properties and potential advantages fir, ash, maple, etc.... might offer.

[wrenchone]

I believe they make Xylophone blocks with pear wood, so you probably wouldn't want to use that...

[planet10]

Originally Posted by The Space Egg Corp

"Make your tonearm out of wood son, t'will be much better."

Grace made 2 very similar unipivots... one with an aluminum girder and one with a chunk of wood. The wood was the preferred arm.

dave

[Nanook]

Great to see other folks doing unipivots.

cactuscowboy:
the arm looks very good, and I am sure it sounds good as well. I do have a minot comment regarding the arm construction. To create a "headshell" that is integral to the arm, it might have been more suitable create a separate "headshell" piece and glue it to the main shaft. The idea there would be to minimize the stress along the grain (I know I'm being anal).

Your re-plinth and arm look excellent.

[cactuscowboy]

Thanks for the comments Nanook.

I hadn't considered "stress along the grain" and I'm not totally clear on the point you're making? If you're referring to physical strength or integrity of the headshell/tonearm there's no worry there as it's very strong.

I had considered making tonearm wand and headshell separate, and in hindsight wish I'd gone that direction. As constructed, the offset of the integrated headshell did interfere with working the tonearm wand on the planer and router table.

I've been thinking about the next tonearm. I like the idea of continuing with wood, and wonder if a guy could create a wood tube by wrapping/glueing very thin veneer around a round form, say a 3/8" steel rod. Remove the form and you've got a thin-walled and very strong wooden tube. I don't have a wood lathe so that's what got me thinking in this direction.

[TerryO]

Originally Posted by cactuscowboy

Thanks for the comments Nanook.

I hadn't considered "stress along the grain" and I'm not totally clear on the point you're making? If you're referring to physical strength or integrity of the headshell/tonearm there's no worry there as it's very strong.

I had considered making tonearm wand and headshell separate, and in hindsight wish I'd gone that direction. As constructed, the offset of the integrated headshell did interfere with working the tonearm wand on the planer and router table.

I've been thinking about the next tonearm. I like the idea of continuing with wood, and wonder if a guy could create a wood tube by wrapping/glueing very thin veneer around a round form, say a 3/8" steel rod. Remove the form and you've got a thin-walled and very strong wooden tube. I don't have a wood lathe so that's what got me thinking in this direction.

Using a veneer wrap over a mandrel has been mentioned before but I'm not sure anyone has actually done it.

Layers of paper and glue might also be used I suppose, they've built canoes with layers of butcher paper and weldwood glue and they turned out pretty sturdy in actual use.

Best Regards,
TerryO

[Nanook]

Terry,

Moray suggested this to me about 2 years ago, building an arm with paper (preferably some very nice rice paper or such). If foam filled, it could be a very strong composite arm...

[TerryO]

Originally Posted by Nanook

Terry,

Moray suggested this to me about 2 years ago, building an arm with paper (preferably some very nice rice paper or such). If foam filled, it could be a very strong composite arm...

Stew,

Instead of filling it with foam, how about taking 2 pieces of foam, cutting a groove down the center for your wires, then gluing both halves together and then tapering it. I suppose it might be possible to mount it vertically on a drillpress (poor man's lathe) and gently turn it down. You could then follow it up with paper & glue (or even thinned shellac) as necessary.

This is just a idea, you're the expert and you will probably see all kinds of flaws in my mindless imageneering.
You know, I might just get off my lazy A** and actually try it when the weather turns cold.


Best Regards,
Terry

[Nanook]

and just because an idea isn't mine doesn't mean it doesn't have merit. I do however like keeping things simple, and I am a little impatient (it would drive me nuts to wait to use the foam/paper arm). Until the arm was in a final state, I'd probably ruin a bunch of them...

The merit of ultra lightweight and self dampened construction has its own appeal, but having an arm too light can create problems as well. The idea of making an arm using foam as a form to wrap whatever kind of material around it, does make sense, but enough material would need to be added until a particular weight is reached.

[cactuscowboy]

Interesting ideas!

I've been thinking about the laminated paper or wood veneer tube concept. I like wood from an aesthetic standpoint, but it would have to be very thin flexible veneer resistant to splitting to work. As for a form or mandrel, perhaps a plastic soda straw would be a good non-stick base, with a steel tube to hold its shape while fabricating.

Also open to ideas and comments regarding aluminum, brass, carbon fiber, fiberglass, bamboo, types of wood, pros & cons of each, etc...