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Idler table tad faster by design.
- Thread starter Metalownz
- Start date
Metalownz
Audiophile? Getting there
Thats the thing i dont want to use sandpaper anymore on this pulley. Im afraid it'll shave it more than it is. I just want to smooth out the pulley so its as soft as it was before. Any other ideas?
Doug G.
Lunatic Member
Thinking about this further, even the act of polishing the pulley may affect the speed because the coefficient of friction will change between the pulley and idler. Is the pulley grooved or just kind of dull looking instead of shiny. If that's the case and there aren't any deep irregularities in it, I think I would leave it.
What did you use to reduce the pulley diameter? A file?
Doug
What did you use to reduce the pulley diameter? A file?
Doug
Metalownz
Audiophile? Getting there
You make a good point. I used sandpaper. Its not super rough actually. But not as soft as it used to be. Not polish soft, but still soft.
Doug G.
Lunatic Member
I think I would leave it. The pulley and idler will "break-in" together with the idler, in spite of it being rubber and the pulley being brass, eventually polishing the pulley anyway.
New pulleys in turntables aren't highly polished to begin with. The area contacting the idler will get more polished than the surrounding brass but that's just how the whole thing works and it takes a long time.
Doug
New pulleys in turntables aren't highly polished to begin with. The area contacting the idler will get more polished than the surrounding brass but that's just how the whole thing works and it takes a long time.
Doug
Metalownz
Audiophile? Getting there
Good enough for me Doug. I guess ill just pop on some LP's and enjoy the music.
Grbluen
Super Member
Bingo! I finally tried some heavier oil. It does indeed correct the speed. I bought some gear oil and then decided that anything that smells that bad has no place in the home. I remembered the silicone oil that I'd purchased for the tonearm damping project. I guessed at the 15000 cst. It's almost perfect! It's so close that I'm not going to try adjusting it! The platter definitely does not want to settle with the heavier oil. I'll have to keep an eye on the bearing.Heather weight oil in the bearing well will slow it down. It works.
Thanks Bob!
monkboughtlunch
Super Member
I realize this is an old thread, but wanted to share that idler wheel DUROMETER (i.e. a measure of rubber hardness) can and will affect driven platter speed. In some cases it can make it run faster.
One symptom of an aged idler wheel is it becomes less pliant and harder.
In extreme examples, a common symptom of a hard and glazed idler wheel is that it loses its grip, resulting in lower speed.
While it may seem counterintuitive, in other examples, a slightly out of spec and too hard idler wheel can still grip enough to turn the platter, but the platter spins FASTER than intended as the rubber is too hard to act as a proper "speed reducing gear" when contacting the motor pulley and platter rim. (This is because the softer pliancy of the idler wheel when new 50 years ago had more ability to be depressed when it contacted the pulley and platter rim, thereby becoming a speed reducing gear.)
Did the original poster rebuild the idler wheel? And if so, who rebuilt the idler wheel and what durometer grade of rubber was used in the rebuild?
There are several common items that can impact driven platter speed in an idler:
1. Oil viscosity (if a heavier oil is used, typically, the motor starts spins slower when cold and then increases in speed as the oil heats up and becomes less viscous)
2. Platter and motor bearing lubrication condition and grade
3. Idler wheel durometer and rubber condition
4. Diameter of motor pulley steps
It would be ideal to determine what grade motor oil and rubber idler durometer was specified / used by the original manufacturer back in the day and compare that with what is being used now.
There are very few vendors now who rebuild idler wheels. One popular vendor in the USA uses only rubber with a durometer of grade 65. The problem with using only one rubber hardness grade to rebuild idler wheels for wheels of all makes and models of turntables is that it's a "one size fits all" approach and this may not work properly for idler designs that employed the speed reducing gear principal. Thus, you might get a table that runs a percent or two fast using a rebuilt idler with 65 durometer rubber.
Thus, with the general difficulty in finding a wheel rebuilder who offers different durometer grades of rubber, it may be easier to install a rebuilt wheel that is too hard, results in too fast speed, and then sand down the motor pulley to compensate. Of course, going forward, you will have to use the same durometer for any idler wheels you install / rebuild in the future as sanding the pulley is a destructive move that cannot be reversed. One challenge with sanding a motor pulley is that if not done properly it can introduce audible anomalies, including thumps and wow and flutter issues.
One symptom of an aged idler wheel is it becomes less pliant and harder.
In extreme examples, a common symptom of a hard and glazed idler wheel is that it loses its grip, resulting in lower speed.
While it may seem counterintuitive, in other examples, a slightly out of spec and too hard idler wheel can still grip enough to turn the platter, but the platter spins FASTER than intended as the rubber is too hard to act as a proper "speed reducing gear" when contacting the motor pulley and platter rim. (This is because the softer pliancy of the idler wheel when new 50 years ago had more ability to be depressed when it contacted the pulley and platter rim, thereby becoming a speed reducing gear.)
Did the original poster rebuild the idler wheel? And if so, who rebuilt the idler wheel and what durometer grade of rubber was used in the rebuild?
There are several common items that can impact driven platter speed in an idler:
1. Oil viscosity (if a heavier oil is used, typically, the motor starts spins slower when cold and then increases in speed as the oil heats up and becomes less viscous)
2. Platter and motor bearing lubrication condition and grade
3. Idler wheel durometer and rubber condition
4. Diameter of motor pulley steps
It would be ideal to determine what grade motor oil and rubber idler durometer was specified / used by the original manufacturer back in the day and compare that with what is being used now.
There are very few vendors now who rebuild idler wheels. One popular vendor in the USA uses only rubber with a durometer of grade 65. The problem with using only one rubber hardness grade to rebuild idler wheels for wheels of all makes and models of turntables is that it's a "one size fits all" approach and this may not work properly for idler designs that employed the speed reducing gear principal. Thus, you might get a table that runs a percent or two fast using a rebuilt idler with 65 durometer rubber.
Thus, with the general difficulty in finding a wheel rebuilder who offers different durometer grades of rubber, it may be easier to install a rebuilt wheel that is too hard, results in too fast speed, and then sand down the motor pulley to compensate. Of course, going forward, you will have to use the same durometer for any idler wheels you install / rebuild in the future as sanding the pulley is a destructive move that cannot be reversed. One challenge with sanding a motor pulley is that if not done properly it can introduce audible anomalies, including thumps and wow and flutter issues.
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