Help with design/geometry for DIY table...designers wanted :) - diyAudio
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Old 12th December 2006, 12:27 AM   #1
Glowbug is offline Glowbug  United States
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Default Help with design/geometry for DIY table...designers wanted :)

Hey all...

I'm starting to think about building a DIY turntable, it seems like a fun project and one that I'm certainly going to get a lot of use out of. I think I've decided on using Scheu parts, such as their 30mm or 50mm acrylic platter, outboard motor and expensive but nice inverted bearing. Tonearm (for the time being) will be a Rega RB250. Now the only part is to get the design all worked out.

I have a woodworker friend who will be doing the construction of the pieces, but I need help with dimensions and geometry. Pardon my horrible Paint skills:

Click the image to open in full size.

That's kind of what I'm going for...like a Teres-looking table.

I know the spindle-to-center of tonearm distance for a Rega is 223mm, but I'm not too sure about...well, the other dimensions Figuring that the "big circle" end under the platter is going to be 12" or a little over, I'm not sure how long to make it or how big to make the other end, if this is making any sense at all...

Does anyone who has built these kind of TT's before care to chime in with some help, or better design skills than I?

Thanks in advance...

~ Jim
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Old 12th December 2006, 01:50 AM   #2
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The most significant measurement for the RB250 is the pivot to spindle length 223mm +/- 1mm. Mark your centre-points for where the platter spindle will locate and where you will drill for the tone arm base and you are then setup fine. The rest of your design will execute basically on asthetics you are trying to achieve.

I'm not sure if this answers your question on measurements but follow that course and you will be fine. Remember one major tip: MEASURE TWICE, CUT (DRILL) ONCE!
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Old 12th December 2006, 01:50 AM   #3
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Hi Jim,

The drawing is the easy part. Deciding what the configuration should be is a sometimes a little harder. In your case, choosing ready made components makes things easier, as long as the parts have correct dimensions. If they don't, then you will have to what till they are in your hands.
I can certainly help you in the drawing department. Of course the fact that I love turntables doesn't hurt.

Jeff
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Old 12th December 2006, 04:20 AM   #4
Glowbug is offline Glowbug  United States
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Another thing I can't quite figure out is the height that the tonearm needs to be mounted at...

I'm pretty sure I'm going with a 30mm platter, could I just mount the tonearm at the same level as the platter? (like a regular Rega Planar with no "armboard", is what I mean) I'm considering using 1.5" or 2" thick butcher block material as the base, having it all in one clean piece would look sharp, IMO. The part that goes under the tonearm would obviously be dado'ed to make it less than 27mm so I could mount the arm.

Thanks guys for the input so far...and for putting up with my n00bishness
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Old 12th December 2006, 08:25 AM   #5
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If you are going with a fixed arm height, it should be mounted level to a record sitting on platter with the stylus sitting in groove. This will give you proper VTA. You can measure by using a ruler and check various points along the arm tube relative to the platter. Some guys have used playing cards stacked up to level one point and recheck down the arm tube to see if it still is level to the record with the stylus sitting in groove.
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Old 12th December 2006, 01:10 PM   #6
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Hi,
on a standard Rega arm the underside of the headshell is 45mm above the armboard with the arm level, so you could take your armboard-to record distance and (loaded) cartridge height from that to work out the mounting height.

I'd really recommend allowing a few mm of vta adjustment because some cartridges (and records) like to be run a bit tail up or down.
regards, Jeff
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Old 12th December 2006, 02:40 PM   #7
Glowbug is offline Glowbug  United States
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Thank you for that info. So if I have 45mm of room to play with...

30mm of platter + 4mm of record/mat + 14mm of cartridge = 48mm of clearance...would an aftermarket VTA adjuster like a Michell or Origin Live give me that extra height without having to build anything else on the plinth?
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Old 12th December 2006, 02:49 PM   #8
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If you're planning to experiment with arms in the future, I'd suggest making an aluminum arm board for the Rega, or source an existing armboard from a suitable TT. If you just drill a hole for the Rega, you can be certain that it won't suit whatever arm you try next.
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Old 12th December 2006, 02:57 PM   #9
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Another thought..

if you think you might want a dust cover, you would be wise to source that before you design your plinth.
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Old 12th December 2006, 07:49 PM   #10
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I don't care too much about a dustcover. I'll probably just use one from a Michell Gyrodec, something that covers the platter and the tonearm only.

Quote:
If you're planning to experiment with arms in the future, I'd suggest making an aluminum arm board for the Rega, or source an existing armboard from a suitable TT. If you just drill a hole for the Rega, you can be certain that it won't suit whatever arm you try next.
I doubt I'll do much experimenting, might just work my way up the ladder of upgrades for the '250, and see where that goes...if I want to experiment with a unipivot, the VPI JMW series uses the same geometry and mounting pattern, IMO...so that's enough to keep me busy for a while.
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