Hi Tom,
It's great you're showing up here in underground world of homebrewed TT builders.
For DIYers the sheer platter mass is the easiest and sometimes the only practical way to reach a decent speed stability. But here is the catch: unevitatble inaccuracies of "kitchen table manufacturing" may nullify the whole gain. Two things mostly matter here: bearing tolerances and platter balancing. Widely used conventional journal bearing has an inherent drawback: platter shaft goes into precession within the bearing gap. Thick platter with the long spindle suffers from dynamic unbalance, especially when the platted CG is set away from the bearing geometrical center. Piere Lurne discussed this topic in length.
Bearing drag fluctuations due to this phenomenon shall be much more substantional, that stylus drag variations, with all my greatest respect to Chris Brady. So, staticaly/dynamicaly balanced heavy platter with the CG at the center of tightest tolerances bearing is the ticket IMHO. How close a humble DIY builder can approach to this target? - I dunno.
It's great you're showing up here in underground world of homebrewed TT builders.
For DIYers the sheer platter mass is the easiest and sometimes the only practical way to reach a decent speed stability. But here is the catch: unevitatble inaccuracies of "kitchen table manufacturing" may nullify the whole gain. Two things mostly matter here: bearing tolerances and platter balancing. Widely used conventional journal bearing has an inherent drawback: platter shaft goes into precession within the bearing gap. Thick platter with the long spindle suffers from dynamic unbalance, especially when the platted CG is set away from the bearing geometrical center. Piere Lurne discussed this topic in length.
Bearing drag fluctuations due to this phenomenon shall be much more substantional, that stylus drag variations, with all my greatest respect to Chris Brady. So, staticaly/dynamicaly balanced heavy platter with the CG at the center of tightest tolerances bearing is the ticket IMHO. How close a humble DIY builder can approach to this target? - I dunno.
Greetings,
Ah, if I only had the time, this (DIY) section of the internet would be one of my favorite places to hang.
The DIY-er has one great advantage over the manufacturer - the ability to put huge amounts of sweat equity into their projects.
In the areas of both electronics as well as turntables, obviously a solid design counts for a lot, but frequently manufacturers have to make cost compromises in order to achieve a realistic price for products other than their cost no object items.
Where the DIY-er can somewhat easily stomach a boutique transformer or adding 20 more pounds of platter mass, the manufacturer might be cost constrained from doing so. The cost effects of weight seem to be exponential, and sometimes, I wish I was in the cartridge business instead.
So, the DIY-er can make up for minor design deficiencies in this manner - bearing in mind of course that a solid design is still the basis for any success.
With respect to the bearing design, Chris Brady, myself and the other members of the original "Teres-5" took this center of gravity issue very much to heart - with respect to the idea of any precession that might ensue from wobble resulting from too high a center of gravity.
What we learned, is that while this geometry is a good thing to achieve (and we designed it into the platter/bearing), its need can be obviated by holding aerospace tolerances in your bearing clearances.
There's another place where a DIY-er may not be at a disadvantage - bonding with their machinist. If you can find out what your machinist's favorite micro-brew is, you can make quick friends (make sure they're not enjoying it when making your parts)
An interesting thing about many machinists is that they're very passionate about some esoteric pursuits, and will come in on days off to make stuff for them. Frequently, it's guns and hot rods ... at least in my experience.
What this means is that you have a chance at bonding with them indirectly by showing them that you're as out of control as they are. Sick minds think alike, and we all have to stick together
Cheers,
Thom @ Galibier
Ah, if I only had the time, this (DIY) section of the internet would be one of my favorite places to hang.
The DIY-er has one great advantage over the manufacturer - the ability to put huge amounts of sweat equity into their projects.
In the areas of both electronics as well as turntables, obviously a solid design counts for a lot, but frequently manufacturers have to make cost compromises in order to achieve a realistic price for products other than their cost no object items.
Where the DIY-er can somewhat easily stomach a boutique transformer or adding 20 more pounds of platter mass, the manufacturer might be cost constrained from doing so. The cost effects of weight seem to be exponential, and sometimes, I wish I was in the cartridge business instead.
So, the DIY-er can make up for minor design deficiencies in this manner - bearing in mind of course that a solid design is still the basis for any success.
With respect to the bearing design, Chris Brady, myself and the other members of the original "Teres-5" took this center of gravity issue very much to heart - with respect to the idea of any precession that might ensue from wobble resulting from too high a center of gravity.
What we learned, is that while this geometry is a good thing to achieve (and we designed it into the platter/bearing), its need can be obviated by holding aerospace tolerances in your bearing clearances.
There's another place where a DIY-er may not be at a disadvantage - bonding with their machinist. If you can find out what your machinist's favorite micro-brew is, you can make quick friends (make sure they're not enjoying it when making your parts)
An interesting thing about many machinists is that they're very passionate about some esoteric pursuits, and will come in on days off to make stuff for them. Frequently, it's guns and hot rods ... at least in my experience.
What this means is that you have a chance at bonding with them indirectly by showing them that you're as out of control as they are. Sick minds think alike, and we all have to stick together
Cheers,
Thom @ Galibier
Hello,
For those, like me that cannot use tape for lack of space and must or prefer to use strings, here's the solution as published few years ago by Teres (if I remember well) before they started suggesting tape:
http://www.marinews.com/Double-Blood-Knot-251.php
Hope this helps....
Dario54
For those, like me that cannot use tape for lack of space and must or prefer to use strings, here's the solution as published few years ago by Teres (if I remember well) before they started suggesting tape:
http://www.marinews.com/Double-Blood-Knot-251.php
Hope this helps....
Dario54
Belt material
The old flat belt from SOTA was getting loose and slippy so I decided to try thread or string drive. Had to turn a new drive drum with a groove for the thread but that was quickly done. Then to try several different "strings". Most all worked well enough but the best I found is what WellTempered uses for the Amadeus TT, .004 transparent nylon thread by Coats thread company. (The spool I have is actually .005"). It took a few tries to get exactly the right length for no slippage but just enough "give" to let the synchronous motor start up reliably. Too tight and the motor won't start, too loose and it has trouble starting and slips. Get it right and it works very well. Besides it is soooo much cheaper and easier to get than the SOTA belt.
Bill
The old flat belt from SOTA was getting loose and slippy so I decided to try thread or string drive. Had to turn a new drive drum with a groove for the thread but that was quickly done. Then to try several different "strings". Most all worked well enough but the best I found is what WellTempered uses for the Amadeus TT, .004 transparent nylon thread by Coats thread company. (The spool I have is actually .005"). It took a few tries to get exactly the right length for no slippage but just enough "give" to let the synchronous motor start up reliably. Too tight and the motor won't start, too loose and it has trouble starting and slips. Get it right and it works very well. Besides it is soooo much cheaper and easier to get than the SOTA belt.
Bill
for an endless supply of mylar in various widths/colour/texture go to your nearest angling shop that sells fly tying supply's and be amazed at the very very cheep and bewildering array of mylar, they will also sell you pure silk, kevlar, nylon and all sorts of fancy threads of various gauge. they also sell all sorts of silk/nylon braids.
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