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andyr

'SkeletaLinn' v2 ...

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Very interesting project, look forwards to seeing the progress.......just a question, wheres the motor go?

 

Think the heat from welding would distort the thin frame too much, would be very hard to weld and keep it straight.

Could you counter balance the weight of the tone arm by using lead weight?

 

Oh now I know what your avatar is all about, thought it was a capital A for Andy ;) .

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Very interesting project, look forwards to seeing the progress.......just a question, wheres the motor go?

 

Think the heat from welding would distort the thin frame too much, would be very hard to weld and keep it straight.

Could you counter balance the weight of the tone arm by using lead weight?

 

Oh now I know what your avatar is all about, thought it was a capital A for Andy ;) .

 

Thank you awty,  :)

 

Yes, I think you are absolutely right about it being very difficult to weld the 3mm-thick aluminium U-channel without distorting it.  (I believe Tase's background is panel beating ... so with him, Maslow's Law comes into play - when he suggests welding! :P )

 

In theory, yes, I could counterbalance the arms by using lead weights - but this would add even more weight to the total weight I have at the moment, with the bearing/platters plus 2 arms.  As I am trying to use the Linn springs, I must limit the total weight in order not to overload the springs.  In v1, I had to use a custom-made spring that was 30% stiffer than a Linn spring for the LH mounting position (nearest the bearing); with v2, by centralising the 3,830gm weight of the bearing & platters, I am hoping I can use a Linn spring in this position, instead.  But it may well turn out that I have to use my custom-made, stiffer springs in all 3 positions! ;)

 

The motor will be positioned 'above' the horizontal side of the triangle, in the below pic, near the LH end.  Because of the slightly different position of the bearing in v2 (compared to v1) I will be able to place the motor in almost a direct line from the main arm pillar (located at bottom RHS, on the extension of the hypotenuse), through the bearing.  (Linnies know this as the "7 o'clock motor position"! ;) )  Theory says a straight line is better, in relation to the side-to-side inertia that the stylus has in the groove; the standard Linn position has the motor pulley on the same side as the arm pillar and subtending about a 110 deg arc with the bearing and arm.

 

 

Regards,

 

Andy

post-104099-0-98335700-1412483388_thumb.

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Yes, I think you are absolutely right about it being very difficult to weld the 3mm-thick aluminium U-channel without distorting it.  (I believe Tase's background is panel beating ... so with him, Maslow's Law comes into play - when he suggests welding! :P )

 

 

 

 

:huh: Maslow's law a new one........so checked on wiki and.......thats not nice to say Andy!!! ;)

 

So time for education  Guys...... :P    .125" is about 3mm

 

 

Tase.

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At trade school we had to learn how to oxy weld alloy sheet :-(

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:huh: Maslow's law a new one........so checked on wiki and.......thats not nice to say Andy!!! ;)

 

So time for education  Guys...... :P    .125" is about 3mm

 

Tase.

 

Mmmm, sorry Tase!  Thanks for the educational material ... but I would need several years of trying, I reckon, to make the end result look nice! ;)

 

 

Regards,

 

Andy

Edited by andyr

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Have you thought about bonding the aluminium together on assembly with a suitable epoxy glue like a construction adhesive, this is how monocoque frames are made in motor sport, increases the strength immensely.

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Have you thought about bonding the aluminium together on assembly with a suitable epoxy glue like a construction adhesive, this is how monocoque frames are made in motor sport, increases the strength immensely.

 

Interesting concept, vwo60.  You mean 2-part epoxy glue as in 'Araldite'?  Or builder's adhesive as in 'Max-Bond'?

 

What would happen to the glue bond when the chassis was placed in the powder-coating tank (as I believe that's quite hot)?

 

 

Andy

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Vivacity Engineering pty ltd , Megapoxy range

Loctite Hysol range

Cheers

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You would probably not be able to powder coat it as the oven would be to hot for the epoxy, you could simply two pack paint it, there is no tank in powder coating, the paint is applied in powder form using a electrostatic charge, once the powder is applied it is placed in the oven to cure, two pack paint is nearly identical but it uses a catalyst to cure the paint,  have you also considered bolting it together using grade 12.9 3mm button head cap screws and nyloc nuts, this way you could power coat it in pieces and then bond/bolt/rivet it after it is coated, just mask up the faces that you will bond together you could then apply even torque to the fasteners rather than using pop rivets which are a hit and miss affair. also you could increase the rigidity further buy using angle bracket on the joints were you have riveted it on the top only. this would then make both joints attached in both planes. these are just suggestions and to date you have done a great job.

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You would probably not be able to powder coat it as the oven would be to hot for the epoxy, you could simply two pack paint it, there is no tank in powder coating, the paint is applied in powder form using a electrostatic charge, once the powder is applied it is placed in the oven to cure, two pack paint is nearly identical but it uses a catalyst to cure the paint,  have you also considered bolting it together using grade 12.9 3mm button head cap screws and nyloc nuts, this way you could power coat it in pieces and then bond/bolt/rivet it after it is coated, just mask up the faces that you will bond together you could then apply even torque to the fasteners rather than using pop rivets which are a hit and miss affair. also you could increase the rigidity further buy using angle bracket on the joints were you have riveted it on the top only. this would then make both joints attached in both planes. these are just suggestions and to date you have done a great job.

 

Mmmm, thank you vwo60 ... but you have me confused.  I attach one of the pics I have already posted, which shows that I already bolt the sections together.  :confused:   AFAIAC, my use of 20 x 45 x 3mm aluminium U-channel for the 3 sides of the triangle, plus 2 x 6mm aluminium sheet pieces (bolted to the U-channel):

  1. for the cross-member supporting the bearing housing, and
  2. to lock together the 2 sides of the triangle at the left

... make the structure as rigid as it needs to be.  And I create the structure before it is powder-coated.

 

 

Andy

post-104099-0-35263700-1412507987_thumb.

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You young 'uns think you are old farts for not knowing what a Miranda Kerr is. Hah! I had to go to the OED to find out what was meant when you referred to a 'google'.

Whippersnappers.

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Sorry, I did not see that it is made of channel, also the bolts look like pop rivets in the photos, the joint next to the arm is only attached by the top plate, as I suggested you could always attach the joint on the vertical plane, you never can have enough rigidity as I am looking at this from a engineering point of view. again just a suggestion, all my projects are just a evolution and there might be an improvement in the sound to be had.

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A status update:

 

Here are the components of the chassis ... after liberal use of a 20mm hole-saw! ;)

 

post-104099-0-70648400-1413615402_thumb.

 

 

And here is the assembled chassis, ready for powder-coating:

 

post-104099-0-54408000-1413615423_thumb.

 

 

This is the test to see whether I have put the bearing in the right location, to get equal weights on all 3 springs (after having taken the cantilevered arm weights into account).  That is lead shot in the soup containers, matching the 450gm weight of a Magnepan Unitrac, in the top position, and the 750gm weight of Duc's Univector at the bottom:

 

post-104099-0-28500300-1413615437_thumb.

 

 

Here's a side-shot.  I measured 26mm from the base of the chassis to the ply base-board, for the spring near the bearing and 27mm for the springs at the arms.  So not exactly equal - but pretty good, I reckon! ;)  My calculations say that the weight on the LH spring is 8% more than each of the other 2 springs - which would seem to be borne out by the measurements - which is a lot better than a standard LP12. :D

 

post-104099-0-13648500-1413615450_thumb.

 

 

So the next things to do are:

  1. get the chassis powder-coated
  2. have Duc machine the spring bases and the motor pod - black anodised this time (not natural brass).

 

Regards,

 

Andy

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Very good

IN my humble opinion the biggest design flaw of the linn, by far, is the uneven weight on each spring

Your desgin is coming along very well Andy !

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Very good

IN my humble opinion the biggest design flaw of the linn, by far, is the uneven weight on each spring

Your desgin is coming along very well Andy !

 

Linn's Keel goes some way to address this balance issue...........Does your Skeletalinn v2 have a good "bounce" @@andyr??

 

Is that a new Cirkus bearing + outer platter?

 

ATBTase.

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Linn's Keel goes some way to address this balance issue...........Does your Skeletalinn v2 have a good "bounce" @@andyr??

 

Is that a new Cirkus bearing + outer platter?

 

ATBTase.

 

Yes, Tase - new Cirkus bearing & platters.  Well, bought in 2013.  ;)

 

But why do you feel the Keel addresses the weight balance issue?  (I can't see how it affects it at all.)

 

 

Regards,

 

Andy

Edited by andyr

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Yes, Tase - new Cirkus bearing & platters.  Well, bought in 2013.  ;)

 

But why do you feel the Keel addresses the weight balance issue?  (I can't see how it affects it at all.)

 

 

Regards,

 

Andy

 

As I said @@andyr not completely no. But some way.

 

whilst the COG and weight remain the same I presume the Mass distribution compared to the ( pretty much now defunked ) pressed steel + MDF affair will be different as Linn would have looked at the area among others.

 

As can be seen the CNC machining is asymmetrical. Tis the way it was designed The motor spring and the top right spring are adjusted pretty close. We had this set up in 20 mins or so and was a doddle to do. I have not touched it since ( coming up to a year ). 

 

 

post-109454-0-98142900-1413850781_thumb.

 

 

ATBTase.

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As I said @@andyr not completely no. But some way.

 

whilst the COG and weight remain the same I presume the Mass distribution compared to the ( pretty much now defunked ) pressed steel + MDF affair will be different as Linn would have looked at the area among others.

 

As can be seen the CNC machining is asymmetrical. Tis the way it was designed The motor spring and the top right spring are adjusted pretty close. We had this set up in 20 mins or so and was a doddle to do. I have not touched it since ( coming up to a year ). 

 

 

ATBTase.

 

Great pic, Tase.

 

However, the nut on the 'arm spring' seems to be wound up more than the 'motor spring' ... and you said this is pretty close to the top right spring.  So, maybe the overall weight distribution is:

  • 40% on the arm spring, and
  • 30% on each of the other 2 springs?

In my case, I reckon I have achieved the following weight distribution:

  • 35% on the motor spring, and
  • 32.5% on each of the other 2 springs.

Just as a matter of interest - re. your spikes.  When I had my LP12 mounted on a wall-shelf, in my last house, I mounted threaded spikes on the underside of the plinth, so as to be able to level the plinth (as the guy who welded my wall-shelf got it slightly off-level).

 

I then substituted fairly hard rubber feet (similar to the stock Linn feet), which were mounted on bolts to again give me a leveling capability ... and the result sounded better than when the spikes were used (not just to my ears ;) ).

 

 

Regards,

 

Andy

Edited by andyr

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At trade school we had to learn how to oxy weld alloy sheet :-(

 

You're still my hero Mal. :love

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Guest Muon

I would be sticking with Kate Upton Andy!!

 

hot-kate-upton-photos.jpg

Unfortunately Kate is already being challenged big time by gravity, not so with Miranda (even after a child).

 

OT, nice thread Andy.

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As I said on the V1 thread, great project Andy, well done. And thanks for the outstanding documentation. The V2 enhancement should be worthwhile..... and easily fine tuned with small weights on 1 or 2 springs.

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As I said on the V1 thread, great project Andy, well done. And thanks for the outstanding documentation. The V2 enhancement should be worthwhile..... and easily fine tuned with small weights on 1 or 2 springs.

 

Thank you, Newman.

 

Regards,

 

Andy

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And now an update. :)

 

I picked up the powder coated chassis on Friday and yesterday fitted the bearing in place & transferred the arms from the v1 chassis.  So this morning, it was time to mount it on springs, to see how level it was with the real arms (rather than weights simulating the arms).

 

Last weekend, I reported that, with the chassis just resting on the springs, I measured 26mm from the base of the chassis to the ply base-board for the spring nearest the bearing and 27mm for the springs at the arms.  This time it was a bit different - I measured 67mm from the base of the chassis to the base-board for the springs nearest the bearing and the front arm, and 68mm for the spring at the back arm (the extra height is because the springs were mounted on the brass spring bases, so I can do the necessary levelling).  So obviously the Unitrac is a bit less than 450gm.

 

Here are pics of the complete TT (before mounting it on the springs) ... plus one after levelling. :)

 

post-104099-0-52202900-1414280374_thumb.

 

post-104099-0-14656100-1414280390_thumb.

 

Next tasks are to:

  • set up the motor, and
  • arrange the deck in the right place on the (temporary) chipboard base, so I can do the measurements to get a perspex one made up (with the hole for the motor pod in the right place, relative to the edges of the base).

 

Regards,

 

Andy

Edited by andyr

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looking good Andy.

time for some spin :)

Duc

 

Thanks Duc - indeed it is!  I am meeting up with Steve soon, to take delivery of a new motor (seeing as I destroyed the old one! :D  :( ).

 

It shouldn't take much work to get it going after that. :thumb:

 

Andy

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