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DIY Tonearm

John Channing said:
I also think, if you look at the second hand price of an Aro, which seems to have crept ever higher over the last few years (now well north of £1000), there is a reasonable sized DIY market if you can put something together for say, £100.
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Well If we go down that route I could put a website together to sell kits from easily enough. I could also produce instructions etc. We'd have to decide who owns the rights and who profits from that though. I know that is probably getting ahead of our selves but worth putting out there.

Stefan
 
John Channing said:
I agree, there won't be 500 customers, but even with 10 firm buyers, it might be worth getting 50 made as people will make mistakes, modifications etc. and if the tonearm works well there will be other buyers.
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Definately worth making more than is needed.
 
orangeart said:
We'd have to decide who owns the rights and who profits from that though. I know that is probably getting ahead of our selves but worth putting out there.
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I would suggest a not-for-profit makers club, where any money made is used to develop the next hifi related project.
 
+1 although for the person who is doing a lot of the hard work of setting up a website and packaging and arranging and fielding orders, some sort of renumeration is in order and I would gladly pay say 25% of the costs to that person for doing it, so its worth their time. Time is money, effort is money. While I am an advocate of open source hardware, people need to be rewarded for this sort of thing.
 
I have emailed a couple of local machine shops to start looking for other options (local would be best to handle quality issues and prototyping). I will transfer my headshell and bearing cup designs into proper software and start modelling the geometry of the complete arm next.

Any suggestions for decent 3d CAD software?
 
Fox said:
+1 although for the person who is doing a lot of the hard work of setting up a website and packaging and arranging and fielding orders, some sort of renumeration is in order and I would gladly pay say 25% of the costs to that person for doing it, so its worth their time. Time is money, effort is money. While I am an advocate of open source hardware, people need to be rewarded for this sort of thing.
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Quite, of course this is all a ways off if at all, I'm happy to do it but there would have to be something in it to stop Mrs. Orangeart putting her foot down. We'd have to form some sort of board to decide what was happening with any spare money and where it was going to be kept. Let's get the thing built first then see what we all think etc.

Stefan
 
Fox said:
I use Solidworks
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I could by a few Aros for the cost of solidworks ;)

I discovered OpenScad which uses a declarative language to build things, rather than a GUI. This is much better for me :). I will show an example later once I have got the hang of this.
 
Just had a wild thought. Why does the arm cup have to be circular? Why not make it square. Not so pretty but much easier to attach the counterweight spindle, the balance shaft and the bias shaft and I can't help thinking it would open up some possibilities for attaching the arm tube shaft.
 
When you are turning things on a lathe circular is easy, square is very hard.

U shaped might work but where would the azimuth shaft locate?

Pete
 
Squares are usually extrusions, but that is all going to pot with higher resolution 3d printers and laser sintering... still not at the resolution of cnc machining unless you spunk up big money. But in a few years time the need for solid anything will be less of an issue. Honeycomb structures with integrated printed conductive paths are already with us but alas I feel that it will never see a tonearm.

then you get into tolerances... what can this structure support when it is a spun/printed/woven lattice? The Geometry is mind bending and the numbers to work it out are beyond me. Seriously seriously hard work.

Anyway back in the real world. When undertaking any machining project I would define the end point first and work backwards, because idiots like me come along and say "hey how about a 12" variant?" and then people speak of slotted heartless and so on. That can come later with a longer arm tube and a new headshell offset. Agree on the end product, make it, then develop it.

My 5c (as a fairly experienced builder)
 
Fox said:
Anyway back in the real world. When undertaking any machining project I would define the end point first and work backwards, because idiots like me come along and say "hey how about a 12" variant?" and then people speak of slotted heartless and so on. That can come later with a longer arm tube and a new headshell offset. Agree on the end product, make it, then develop it.

My 5c (as a fairly experienced builder)
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Funny you should say that. I started messing around with OpenSCAD which uses a language to define and transform shapes. I have basically parameterised the design so you can dial in your preferred headshell angle (within reason), arm length, and arm diameter, and it will automagically make it work.

I sketched out the other components (armtube, body, stub, and counterweight) and assembled them together to make an arm. Have a look and see what you think. The offset angle is 22 degrees (Rega), but I wasn't careful about the arm length (still some tuning of the model required). You can download a STL file here:
https://www.dropbox.com/s/ldnfsk3qszblf25/assembly.stl

If you need to, you can download a viewer here:
http://www.freestlview.com/

Feedback please :)
 
Looks good, Roksan base would be good for me, unless I make a new top for my Xerxes.

Pete
 
timH said:
Point is how much precision is actually needed for this particular part?
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A reasonably high level of precision is needed for every part of an arm.

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VPI already do a 3D printed arm tube and if it is modelled in CAD it's not difficult to have it 3D printed. The issue is the materials it can be printed from and the cost of higher resolution printing.

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There's no point in making the bearing housing square, it's more difficult to machine and the benefits are minimal (if they exist at all).
 
YNWOAN said:
VPI already do a 3D printed arm tube and if it is modelled in CAD it's not difficult to have it 3D printed. The issue is the materials it can be printed from and the cost of higher resolution print.
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I wonder how well they sell, it might be very special but I'd imagie the perceived value of a 'plastic' tonearm is low. Most of us have seen some of the very ropey 3-D prints in Maplins of RS as well. I'm sure these are nothing like that but the perception of 3-D printer stuff is of early prototype quality.
 
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