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Old 13th October 2010, 12:30 PM   #1
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Default Motor position

To all you turntable builders out there, I would be interested to know how you choose a motor position. For an onboard motor, the options for the motor spindle position would be on a circle around the subplatter. However, the preferred position on this would seem to be as far away as possible from the cartridge when on the inner grooves to minimise any interference problems. However, using this criteria only, this would seem to put the motor at about 11 o clock, toward the back of the plinth. However, this is now moving the motor closer to the arm pivot which may give rise to induced effects on arm wiring. Perhaps the position is not that critical at all, however, I would be interested to hear whether anyone ever considers this, after all, in many new builds, the motor position is free.
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Old 13th October 2010, 04:49 PM   #2
kevinkr is offline kevinkr  United States
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I consider it in my often ill-fated TT projects, and FWIW I think placing the motor as far from the cartridge is the way to go as it is far more susceptible to magnetic pick up than the the wiring in the pivot or arm tube. For me somewhere around 10:30 - 11:00 O'clock would be the right position for the motor..
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Old 13th October 2010, 05:13 PM   #3
wjlamp is offline wjlamp  Greece
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Quote:
Originally Posted by davecooper View Post
To all you turntable builders out there, I would be interested to know how you choose a motor position. For an onboard motor, the options for the motor spindle position would be on a circle around the subplatter. However, the preferred position on this would seem to be as far away as possible from the cartridge when on the inner grooves to minimise any interference problems. However, using this criteria only, this would seem to put the motor at about 11 o clock, toward the back of the plinth. However, this is now moving the motor closer to the arm pivot which may give rise to induced effects on arm wiring. Perhaps the position is not that critical at all, however, I would be interested to hear whether anyone ever considers this, after all, in many new builds, the motor position is free.

If you do have self space place it,as far enough as,you belt allows you to.
If your turntable,is of the suspended kind,the best place is the one,that disturbs the suspension less.On the solid type plinth,I do prefer a 19:00 -21:00hours position ,for reasons of accesibility.
If motor related interference,is your problem,a silent groove disc,will solve your problem. Roll it and change the positions of the motor.Leave it at the position less problematic.If all sound the same,go to phrase one.

B.L.
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Old 13th October 2010, 06:13 PM   #4
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Like kevinkr, my preference is for the motor at 10:00 to 11:00 o'clock, and for pretty much the same reasons. I've never had any problem with it there.
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Old 13th October 2010, 08:44 PM   #5
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same here. I kept it from the cartridge as much as possible.
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Old 13th October 2010, 08:58 PM   #6
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Thanks for the replies. My measurements seemed to put the optimum position at about 11 o clock so it's nice to see this backed up. The (possibly also ill fated) turntable I am thinking of building will be a simple solid plinth and decoupled motor affair so no suspension issues to worry about.
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Old 15th October 2010, 05:20 PM   #7
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by davecooper View Post
Thanks for the replies. My measurements seemed to put the optimum position at about 11 o clock so it's nice to see this backed up. The (possibly also ill fated) turntable I am thinking of building will be a simple solid plinth and decoupled motor affair so no suspension issues to worry about.
When you do please share some photographs.. I always like to see what fellow diyer's are doing. It's often quite inspiring.

My one ill-fated (expensive) acrylic plinth project turntable will live on in the hands of a friend who will use it to build himself a TT in the near future.. With 3 TT "projects" and several arms I don't need another.. I'm swapping it for a bunch of NOS octal tubes of various sorts..
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Old 15th October 2010, 05:39 PM   #8
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Quote:
Originally Posted by kevinkr View Post
When you do please share some photographs.. I always like to see what fellow diyer's are doing. It's often quite inspiring.
Here are a few shots of mine. The plinth and the platter are acrylic, the whole thing sits on a granite surface plate isolated with some EAR Isodamp grommets. The motor is a surplus 900 RPM hysteresis synchronous capstan motor, for extremely smooth rotation. The spindle is machined from non-magnetic stainless steel.

I built this around 1990, when I had access to a machine shop.
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Old 15th October 2010, 10:45 PM   #9
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Still at a bit of an early stage at the moment so no pics just yet but will certainly be posting some when the TT has progressed a bit. I am phographing every step just in case anyone is interested in the build.
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Old 16th October 2010, 03:42 PM   #10
Nanook is offline Nanook  Canada
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Default fiddlesticks I tell ya, fiddlesticks!

One argument that you all seem to forget is the potential for lateral vibrations (with respect to the cantilever at any given time) to effect the cantilever while in the groove of the record. I did a little mathematics and the location of the motor does have a preference for the 7-7:30 position, based on analysis of the angle of the drive belt to the driven platter.

Seems the Pink Triangle/Funk Firm folks agree...

Jaques Merde: very good implementation.Looks good. I imagine that it sounds very good.
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Last edited by Nanook; 16th October 2010 at 03:44 PM. Reason: added comment
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