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Old 3rd October 2010, 09:59 PM   #31
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Default Hi Cactus

Quote:
Originally Posted by cactuscowboy View Post
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.
Hi again Cactus Cowboy

I'm afraid that I might have caught the tone arm making bug from all the great inspiration on the site at the moment.

I'm just guessing, but seeing as you've just made a unipivot arm, then a gimble type arm might be next on your list.

I have recently made a miniature 'steadicam' the simple device patented by Garrett Brown (steadicam photographer on Kubrick's 'The Shinning', still some of the best steadicam stuff ever done I think).

I found that when making the steadicam the brand new ball races I was trying to use were not 'beded in', and whilst the amount of oil/grease they contained is fine for 1000rpm the fact that a steadicam (or a tonearm) never ever does a single whole revolution in it's life, made the unbeded and grease thick bearings unsuitable, due to way too much friction.

Eventualy I thought of using secondhand (and totaly free both in $$$'s and friction) bearings from scrap VHS players which you can literaly find on every street corner.

I have now taken apart 6 VHS players and apart from getting free transformers, capacitors and the like, they are a great source of precision mechanical parts.
Every video head I have taken apart has perfectly worn-in (not worn out) bearings inside it and 6mm dia shafts and bits and pieces to hold and support bearings etc.

The other free source of these types of parts I have also used is busted computer printers of which there are also loads about.

I like your idea of rolled and glued veneer, I would never have thought of that one.

I have also been looking at 10mm id woven carbon fibre tubes, which are extremely light, but rigid, and 18" costs about $15.

I am thinking to make the gimble out of ordinary copper pipe or similar, and fitting the bearings straight is easy, you just put the 6mm shaft through the bearings to hold them straight and run slow set epoxy carefuly round in a fillet between the pipe and bearing sitting in it's hole.

I'm not that great when it comes to wood, but I might have a go, as I think a wooden headshell would be cool.

My idea for a ready made movable weight, is to use 'shaft collars' available in loads of different diameters, in stainless steel & aluminium for $3 a go from engineering suppliers (haven't figured out where to get those for free yet, damn).

Thought I'd bung in a few ideas that have helped me.

Have enclosed some photos of the miniature steadicam, which was made using only a hand drill and a load of files.

There's a cool site called homebuiltstabilizers.com if you want to check out peoples DIY steadicams.
Have also enclosed a PDF paper on 'dynamic balance', it's written for steadicam guys but is just as applicable to tonearms (it's an interesting read and not full of 'Hi-Fi' gobbledegook).

Cheers for now. Simon....

Also you've inspired me to take my Dual TT out of it's existing plinth, and make a new chunky wood one, which I think will suit it. Also taking the old arm off to use as an experimental test bed for the DIY arm. Oh no, not another project, I've got 2 TT refurbs to do now !!!
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Old 4th October 2010, 12:38 AM   #32
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Quote:
Originally Posted by The Space Egg Corp View Post
I'm just guessing, but seeing as you've just made a unipivot arm, then a gimble type arm might be next on your list.
No, actually, I intend to continue with unipivot.

I have a number of high quality turntables (nothing uber expensive) which are all equipped with conventional gimballed arms. I look at my Technics SL-1200 for example and I know that I cannot DIY an arm of that design that comes even remotely close to the quality and performance of the Technics. Keep in mind I don't have a machine shop, so I can't attain high levels of precision in any tonearm I build.

Unipivot is a different story though. It's such a simple design (small number of parts) and the one highly critical part, a super low friction bearing with zero play, is easy to obtain and inexpensive.

Thanks for your detailed post, you've given me some good ideas, the use of "shaft collars" as counterweights for example.
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Old 30th July 2012, 11:19 AM   #33
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Very interesting tread. I have stared working on a Naim Aro inspired tonearm with a carbon fiber tube. I will check out the unipivot bearing you suggest.
Until now I have only used a ballpoint pen and a 6 mm stainless screw for bearing. the project is under construction.
Click the image to open in full size.

Since the carbon fiber tube allows at least 4 projects, I have also started on a Well Tempered inspired arm.
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Old 20th October 2013, 03:04 AM   #34
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Default Wooden arm

Hello cactuscowboy,
Arm looks quite good! (referring to accompanying photos of post #7) I especially like the vta counter stabilizers. I had observed one part which when I build my arm, will implement different. It is the actual 'unipivot' location. I believe the center of gravity could be much lower, negating the use of so much outboard stability weight.

regards, Francis
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