SME 3012 question

[drSM]

I have a 3012 that has the main counterweight seperate from the thing beside it (further away from fulcrum) that carries the L shaped rod onto which the rider weight sits.
More recently i have another 3012 (from a LWB td125) which is different only in that the main counterweight and the bit that carries the L rod are the 'one piece'.
I think they are both 3012 mkII from the late 60s, early 70s.
Were these arms available in either version ?
Thanks

[killie99]

All you ever wanted to know about 3012 .... https://www.vinylengine.com/library/sme/3012.shtml

You'll need an account to view/download the docs.

[Andy831]

Have a look here

http://www.analogue-classics.com/htm...09___3012.html

[Barry]

Have a look here

http://www.analogue-classics.com/htm...09___3012.html

Yes - that's a very useful site.

To answer the OP's question, the earlier 3012 Mk.II arms came with the two-part counterweight, whereas in the later versions the counterweight was of one piece.

If you go back far enough, the Mk.I arms had the playing weight and transverse balance adjustment mechanism as an end cap, pemanantly attached to the back of the rear arm stub, with the main counterweight held captive on the back stub between the knife edge bearings and the end cap.

[take5]

Yes - that's a very useful site.

To answer the OP's question, the earlier 3012 Mk.II arms came with the two-part counterweight, whereas in the later versions the counterweight was of one piece.

If you go back far enough, the Mk.I arms had the playing weight and transverse balance adjustment mechanism as an end cap, pemanantly attached to the back of the rear arm stub, with the main counterweight held captive on the back stub between the knife edge bearings and the end cap.

I agree with all of this post , but the bit in red possibly needs clarification, re "permanant", in case the opening poster gets confused.

it isnt strictly permanant in that this rear piece can be removed if wanted.
but unlike the later versions, it cant be moved along the tone arm stub. It can only go on the end, once the main weight is on first, and is then tightened in position.

at least it is like that on my series 1 3012. (Or, as I like to call it..... my "pension fund")

If you go to the analogue classics article and scroll down to near the bottom, you will see a picture of the series 1 3012 and the part we are talking about.

[Barry]

I agree with all of this post , but the bit in red possibly needs clarification, re "permanant", in case the opening poster gets confused.

it isnt strictly permanant in that this rear piece can be removed if wanted.
but unlike the later versions, it cant be moved along the tone arm stub. It can only go on the end, once the main weight is on first, and is then tightened in position.

at least it is like that on my series 1 3012. (Or, as I like to call it..... my "pension fund")

If you go to the analogue classics article and scroll down to near the bottom, you will see a picture of the series 1 3012 and the part we are talking about.

I was going by the photos I have seen of the Mk. I arms. I couldn't see any end cap attachment grub screw, so erroneously assumed the end cap was permanent. Thanks for the clarification and apologies for the confusion.

[drSM]

Aha Thanks for all that
Understand now
so this 'one piece' 3012 is in fact a slightly later 3012.
It would fit with the original owner acquiring the turntable and arm in early 70s
My older one was from 1967

I like the 'pension fund' 3012 Brian Take 5
I have seen one of those series 1 arms - goes for silly money.

I looked on ePay and my 3012 series 2 is worth about USD 1100 to 1500 - wow


I ll post another question re these 3012/3009 arms
I ve seen all manner of ways that users assemble the outrigger - usually dangling ' low and to the right' but even in that article wwwanalogue classics there are pics showing it coming off on the upper side of the back weight.
And i have seen pics of the outrigger extended out far off the axis of the main tube
Surely this creates unnecessary torque on the knife edge which one would think is unnecessary and cant be 'good' .

In contrast on this Rega arm on my old Planar2 first gen 1979 (Acos Lustre?) the designers dangle a cylindrical weight on the other side.
What could this be trying to achieve?

There are arms where all the counterweight is along the axis of the tube - i cant see the logic in putting weights off axis ?

[Barry]

The 'outrigger' is there to provide transverse or lateral balancing of the arm. The arm is J-shaped, so without any lateral balance the cartridge/headshell mass would cause one of the knife edge bearings to lift (the one on the right-hand side as seen from the front). By adjusting the distance of the L-shaped outrigger (with the additional sliding weight, used to adjust the VTF) from the axis of the main armtube, the force on each knife edge bearing can be equalised. Or in other words, the anti-clockwise torque imposed by the cartridge/headshell mass is counterbalanced by the clockwise torque created by the outrigger weight. Heavy cartridges, such as the Ortofon SPU, need to have the outrigger extended far from the main arm tube axis.

The outrigger arm should be fitted low and to the right as seen from the front of the arm. This is for the purpose of stability; which might explain what the extra cylindrical weight on the Acos arm is for.

Arms which only have their counterweights coaxial with the arm tube, presumably use captive needlepoint bearings which cannot lift as can knife edge bearings. If the arm can be designed so that the stylus tip lays on a line passing through the centre of the arm tube, any residual torque about the axis of the armtube would be very small and within the operating specification of the bearings.

[drSM]

The 'outrigger' is there to provide transverse or lateral balancing of the arm. The arm is J-shaped, so without any lateral balance the cartridge/headshell mass would cause one of the knife edge bearings to lift (the one on the right-hand side as seen from the front). By adjusting the distance of the L-shaped outrigger (with the additional sliding weight, used to adjust the VTF) from the axis of the main armtube, the force on each knife edge bearing can be equalised. Or in other words, the anti-clockwise torque imposed by the cartridge/headshell mass is counterbalanced by the clockwise torque created by the outrigger weight. Heavy cartridges, such as the Ortofon SPU, need to have the outrigger extended far from the main arm tube axis.

The outrigger arm should be fitted low and to the right as seen from the front of the arm. This is for the purpose of stability; which might explain what the extra cylindrical weight on the Acos arm is for.

Arms which only have their counterweights coaxial with the arm tube, presumably use captive needlepoint bearings which cannot lift as can knife edge bearings. If the arm can be designed so that the stylus tip lays on a line passing through the centre of the arm tube, any residual torque about the axis of the armtube would be very small and within the operating specification of the bearings.

Perfectly explained Barry, Ta v much

[drSM]

Could someone suggest how much is this arm worth?