Those are not flywheels, at least a rotating mass has some flywhell behavior but it's not defined as a FW because the motor gives the rotation and the platter receives it and they are connected by the belt. A correct way of doing it is: motor(pulley) - belt-FW-belt-platter)
So if I try to bounce on a trampoline, I won't be able to because my mass is different to planet earths ?
Two masses with a spring in between will have a resonance, even if one is much lighter than the other, whether it will be to such an extent that it will be detrimental to sound is another matter.
Two masses with a spring in between will have a resonance, even if one is much lighter than the other, whether it will be to such an extent that it will be detrimental to sound is another matter.
Seriously?
Have you compared the noise/rumble of a running automobile timing chain to that of even the cheapest belt drive turntable?
Perhaps they do stretch, but on the other hand that stretch also helps isolate the platter from motor vibration. The mylar belt might give you better speed consistency but that might come at the expense of higher transmitted vibration. It will be interesting to see you post your results.
Ray K
Ideal for a non stretchable belt, if that is the only parameter!
Long life too.
I feel the OP is being OCD, I have already said so in earlier posts.
Long life too.
I feel the OP is being OCD, I have already said so in earlier posts.
You are correct but what you described is only true for a stationary belt and platter. A flat belt travelling around a rotating system doesn't oscillate the same way. Try it and see.
Ray K
Anybody know 'Flywheel, Shyster and Flywheel'?
Let someone do the calculation for variation in speed at 33 RPM on a 5 kilo platter at constant speed and load.
There is no sudden load, the variation can only come from belt tension changing or motor speed variation.
The result will be enlightening.
Let someone do the calculation for variation in speed at 33 RPM on a 5 kilo platter at constant speed and load.
There is no sudden load, the variation can only come from belt tension changing or motor speed variation.
The result will be enlightening.
Like I said, this will prove the OCD part...
This calculation was part of the calculation for the energy stored in power press flywheels...
Turntables are kid stuff in comparison.
5000 grams or 50g rams, it will be below noteworthy in my opinion.
This calculation was part of the calculation for the energy stored in power press flywheels...
Turntables are kid stuff in comparison.
5000 grams or 50g rams, it will be below noteworthy in my opinion.
And perhaps stylus drag. Stylus drag is small, but its an actual force (it depends on tracking force setting, and will vary - with radius, with signal level, with grot building up on the stylus even), so you have to ensure the belt's stiff enough to keep this effect below audibility for all the likely tracking forces you're going to see - you can't arbitrarily reduce belt stiffness for better speed regulation, there's an optimum value in the middle somewhere.
The mass of the platter only affects the bandwidth of the variation, note, and in practical terms the startup-time too.
So forget the flywheel effect, look at the stiffness of the belt and the torques involved - stretching the belt will change the speed, so we are concerned with how much percentage stretch for a given torque perturbation, and with the order of magnitude of these perturbations.
Note that friction forces are somewhat chaotic and cannot be treated as purely constant, so variations in friction over time may be significant.
Friction is often very temperature dependent, motors warm up, bearing oil becomes thinner, if the rubber belt warms up it will try to contract and its tension will increase.
Once you've determined that the belt stiffness is adequate for all the torque perturbations likely to be involved, you can select a moment of inertia for the platter to adequately low-pass filter motor vibration noise from the platter. The belt and platter form a low pass filter. Usually the motor mountings are more of an issue with motor noise, they are likely to be the main route from motor to central bearing unless the motor is on a completely separate chassis.
There's also a long term speed effect caused by the belt becoming slacker over time leading to different deformation/stretching over the motor pulley, and different lateral forces on the bearings changing the bearing friction...
There's a lot of physics involved once you go down the rabbit hole.
Not the way I see it. That's the AC behavior which is superimposed on the DC behavior as in electrical circuit analysis. It's not too difficult to analyze the electromechanical system using spice, if one is so inclined. This link illustrates the methodology.
NOW BACK TO THE SUBJECT
''It is kind of sad that no one read your post closely or could understand what you are looking for''
Well TomWH, that's kind of the nature of DIYaudio, happens many times.
The belt from Galiber, looks promising & is reasonable priced at $38, so I will send for one, hopefully the postage cost is not larger that the item cost!!
The reason though of this is a while ago I read a blog on Audiogon, where a guy had found a cross hatched metallic coated tape that gave lower speed variance that the standard tape/Mylar belt. Sadly that tape is no longer available.
Unfortunately i cannot just try the idea myself as I do not owe a rubber belt, I moved from idler drive to DC driven motor tape drive. Then you of course have the problem of finding out which rubber belt is a good one for the job. So that is why I though I would ask the group.
Cheers
''It is kind of sad that no one read your post closely or could understand what you are looking for''
Well TomWH, that's kind of the nature of DIYaudio, happens many times.
The belt from Galiber, looks promising & is reasonable priced at $38, so I will send for one, hopefully the postage cost is not larger that the item cost!!
The reason though of this is a while ago I read a blog on Audiogon, where a guy had found a cross hatched metallic coated tape that gave lower speed variance that the standard tape/Mylar belt. Sadly that tape is no longer available.
Unfortunately i cannot just try the idea myself as I do not owe a rubber belt, I moved from idler drive to DC driven motor tape drive. Then you of course have the problem of finding out which rubber belt is a good one for the job. So that is why I though I would ask the group.
Cheers
Look for similar belts in industrial supplies.
Just measure the inside length, use a string wrapped around the pulleys, then open it up and measure it, also groove widths, top and bottom.
Sewing machine belts, for industrial grade machines, come to mind.
About $2 here.
Basically fabric backed synthetic rubber, cogged inside edge.
Just measure the inside length, use a string wrapped around the pulleys, then open it up and measure it, also groove widths, top and bottom.
Sewing machine belts, for industrial grade machines, come to mind.
About $2 here.
Basically fabric backed synthetic rubber, cogged inside edge.
VHS tape is worth trying since it works originally by wrapping the tape around a video drum head.
Thanks, that's a good point, have not tried that one for some reason & I have got a couple of old tapes lying around somewhere.
But not really going with my question, guess I am in my own mad world.
Cheers
But not really going with my question, guess I am in my own mad world.
Cheers
I've been experimenting with different belts on my DIY turntable for quite a while. My TT uses a large Papst motor running at 750 rpm,
driven by a 3 phase supply derived from an SG4, along with 3 x 200W amps and 3 x 80VA transformers, it is completely silent and has no vibration
I can feel.
The lowest W&F I've achieved with a good quality rubber belt is 0.03%. Poorer quality rubber belts show much higher W&F.
I have also used Kapton tape, which shows a little more high frequency noise, and a best figure of 0.06%, the increase I think caused by the joint
passing over the motor pulley. The biggest issue with the Kapton tape is the removal of the adhesive layer on the back, as it appears impossible to buy it without adhesive. I have tried several solvents, but what's available these days doesn't do a very good job.
If anyone comes up with a good way of removing the adhesive I think this material might be the best solution as the adhesive side seems to be slightly more matt than the other.
driven by a 3 phase supply derived from an SG4, along with 3 x 200W amps and 3 x 80VA transformers, it is completely silent and has no vibration
I can feel.
The lowest W&F I've achieved with a good quality rubber belt is 0.03%. Poorer quality rubber belts show much higher W&F.
I have also used Kapton tape, which shows a little more high frequency noise, and a best figure of 0.06%, the increase I think caused by the joint
passing over the motor pulley. The biggest issue with the Kapton tape is the removal of the adhesive layer on the back, as it appears impossible to buy it without adhesive. I have tried several solvents, but what's available these days doesn't do a very good job.
If anyone comes up with a good way of removing the adhesive I think this material might be the best solution as the adhesive side seems to be slightly more matt than the other.
Hi, thanks for that, have not tried Klapton tape so have now got a roll on the way. All I do with the adhesive on my Mylar tape is handle it. by pulling it through my fingers, bit of a PITA but eventually the adhesive goes.
Can you give us a link the the best belt you used, as finding a good belt is like trying to find a good dentist.
Cheers
Can you give us a link the the best belt you used, as finding a good belt is like trying to find a good dentist.
Cheers
I don't think that'll work with Kapton tape, the adhesives are either silicone or acrylic, neither of which is easy to remove.
I'm going to try paint stripper next, hopefully it'll take off the 'glue' without damaging the polyamide.
Sorry, but I'm not sure where I got my 'best' belt from; I've tried a few, but I'm not very good at keeping records 🙁
I'm going to try paint stripper next, hopefully it'll take off the 'glue' without damaging the polyamide.
Sorry, but I'm not sure where I got my 'best' belt from; I've tried a few, but I'm not very good at keeping records 🙁
FWIW:
If you need to remove sticky medical tape like band aids, cloth tapes, surgical adhesive bandages, and the like, ethyl alcohol (sometimes called surgical spirits), or Iso propyl alcohol (commonly sold as rubbing alcohol), dribbled at the edge cause the adhesive to lose strength, and the stuff can be peeled off easily.
Particularly useful when hair may be pulled out.
No, I have not tried Vodka...only pure Iso alcohol.
If you need to remove sticky medical tape like band aids, cloth tapes, surgical adhesive bandages, and the like, ethyl alcohol (sometimes called surgical spirits), or Iso propyl alcohol (commonly sold as rubbing alcohol), dribbled at the edge cause the adhesive to lose strength, and the stuff can be peeled off easily.
Particularly useful when hair may be pulled out.
No, I have not tried Vodka...only pure Iso alcohol.