My unipivot tonearm

wmincy · 24th March 2006, 06:58 PM

Almost for a half year I have been searching for a worth second-hand tonearm, navigating on ebay, on audio market websites... Nothing, or too expensive or too many bidders. So I decided to build one by myself: unipivot, knive-bearing, or ball-bearing? I choosed the first one as my father has the other two types of tonearm.
Oh, it was very hard to design and in the same time to be able to realize it, while you have only lathe and miller machine (not CNC): every idea is good but not always makeable!
Using lathe and miller macchine of my company (after working hour, of course!), I made all the parts.
Here are some photos of my tonearm.

wmincy · 24th March 2006, 06:59 PM

another photo

wmincy · 24th March 2006, 07:00 PM

...another photo

wmincy · 24th March 2006, 07:04 PM

...photo

pixpop · 24th March 2006, 07:34 PM

Very nice. Can you describe the arm some more.. what material is it?

Eggzy · 24th March 2006, 11:05 PM

wow wmincy that is cool!
are you going to polish the alloy bits or keep the brushed effect?

eric

Eggzy · 25th March 2006, 02:02 AM

...did you use a router bit to cut the elongated slots in the headshell? if so any probs with juddering?

eric

wmincy · 25th March 2006, 10:43 AM

Yes Pixpop, this tonearm lenght is set to 12" (the effective lenght is circa 340mm), you can see the numbers in the picture that indicates different parts (without the support and the entire holder block):
1- the first part of the body is in carbon fiber, and it is from a fishing rod spare part. At first I wanted to use arrow as the body, but there is no sizes for this purpose (diameters are too small).
2 - the second part of the body is in steel, hardened and tempered then grinded, well finished.
3 - the screw, or the pivot of this tonearm, has the end sharpened. It had also been hardened to prevent wear, as it supports all the mass of the tonearm.
4 - the 'V' part is in steel. It balances the lateral rotation, as for a unipivot tonearm is a big problem.
5 - two Ø3mm shaft that connect the counterweight with the V part.
6 - counterweight shaft. In alluminium.
7 - the brass counterweight. Around 200 gram.

The support of the screw was a big problem since the begining of the project. It should be absolutely sharp! Not round ended. This problem brought me to the hardness test machine. It a Vicker's hardness test machine with use of diamond cone. Before heat treating the support, I imprinted the cone form on it, so as result a very sharp and hard cone form!

The headshell is worked with miller machine (router is for wood), this one is in steel, but i'm not very satisfied about this choice. May be later i'll make one of alluminium.

wmincy · 25th March 2006, 10:54 AM

Eric,

polishing is one of the matter that care a lot, but as you have noticed it is still not as reflective as a mirror... Every part has been grinded for hours (the polishing took so much time that i almost became mad!) and sand sprayed. May be a chrome coating should bring it shining!! haha

Or using a render software.... hehe

Eggzy · 25th March 2006, 01:55 PM

Ah! I see WMINCY...
I thought the headshell was aluminium.

The reason I asked is because, I love to polish aluminium myself, I got a metal polishing kit from ebay & you can get a beautiful mirror finish with a little effort! Works with plastic bits too!

POINT OF INTEREST; I've noticed a lot of counterbalances which are de-coupled with rubber grommets etc. I can't help wondering whether this is a good or a bad thing? Could this just be creating an 'energy storage area?'

Has anybody examined the merits or drawbacks of a pivoted [swinging] counterbalance?

Anyway WMINCY it’s a wonderful arm. Keep up the good work

Eric

24th March 2006, 11:05 PM	#6
Eggzy diyAudio Member Join Date: Oct 2005	coooooooooooool wow wmincy that is cool! are you going to polish the alloy bits or keep the brushed effect? eric

25th March 2006, 02:02 AM	#7
Eggzy diyAudio Member Join Date: Oct 2005	headshell question ...did you use a router bit to cut the elongated slots in the headshell? if so any probs with juddering? eric

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24th March 2006, 07:34 PM	#5
pixpop diyAudio Member Join Date: Jan 2005 Location: Los Angeles	Very nice. Can you describe the arm some more.. what material is it?

25th March 2006, 01:55 PM	#10
Eggzy diyAudio Member Join Date: Oct 2005	Ah! I see WMINCY... I thought the headshell was aluminium. The reason I asked is because, I love to polish aluminium myself, I got a metal polishing kit from ebay & you can get a beautiful mirror finish with a little effort! Works with plastic bits too! POINT OF INTEREST; I've noticed a lot of counterbalances which are de-coupled with rubber grommets etc. I can't help wondering whether this is a good or a bad thing? Could this just be creating an 'energy storage area?' Has anybody examined the merits or drawbacks of a pivoted [swinging] counterbalance? Anyway WMINCY it’s a wonderful arm. Keep up the good work Eric