Turntable Bearing heated

Hi Tjj226,

Torque never enough, but I am not thinking to have a too low torque, near the limit perhaps.

However the two motors checked unloaded have a pretty good same speed as the electronic that control them individually, despite the age, is good in my opinion.

Under the load also I have well synchro them with pulleys diameter, belt tension. Off course there are some variation due to many factors such as belt precision in roundness, in length, in the motors itself. But my motor have a variation of the speed plus minus 0.1 or 0.2 RPM out of the 360 RPM unloaded and I consider it pretty good. Sure you may get better but......
Attach the pic of the 2 motors that have 90mm rotor ( not so small ) flat type being brushless with outside rotor.

Next week I will have my platter bearing re made therefore I will have data with the complete unit. At the present I just run the fly wheel unit without the platter and after I used the Cera Tec additive I got at cold some more RPM immediately ( not enough for me ) and tehmax speed in warnm state is the same.

Keeping posted and Tks to all.

Adelmo
 

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Adelmo,
How much running clearance do you have between spindle and bearing?

Unfortunately I do not recall it anymore, and I do not have the tools to check it now with the required precision. My fly wheel bearing takes pretty long time turning it after I in let the oil before it reach the bottom position. In fact I spin it with motors for several minutes before it reaches slowly the bottom position. I also say that turning by hand the fly wheel is very smooth indeed and easy to turn. I do not feel any hesitation to turn it. The inertia I think is not low, but wanted so, the fly wheel weight 4 Kg with an outer Diameter of 90mm. However the two belts with round section 2.4mm and ID of 85mm do no slip and easily turn the fly wheel at start. Sure some belt stretching may happen during the start, though not noticeable by eyes, but shall resume to normal immediately I think.I also checked the turning force by hand turning the fly wheel before the sphere touch the bottom ( levitating by the oil ) and I did not feel a difference so important though obviously there might be a light difference, at least in theory.

Just to have an idea, the standard sintered oilite bushes for a 20mm shaft I consider to be too loosen.

I expect with the running of the mechanical parts some improvements anyhow.....

Tks n rgds

Adelmo
 
Hi,
my thinking was more on line with bearing having tight tolerance.The spring can be adjusted to compensate for wear after time. or platter weight can be reduced. I understand less contact point imposes more pressure and possible more wear. alternative solution would be to cut cylindrical bush(Sleeve) bearing longitudinally in three section and one section will press against the shaft (withspring) the empty speca can hold the oil. As shown in the pic.
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as for temperature affecting the speed, not sure but what could possible happen is when heated the bearing has more tolerance so ultimately one looses the advantage of tight tolerance bearing.
regards

HI,

More loosen tollerance also warm up while turning and become more loosen so less precise compared to the tighter tollerance during the warm spinning.

Tks n rgds

Adelmo
 
Hi Tjj226,

Torque never enough, but I am not thinking to have a too low torque, near the limit perhaps.

However the two motors checked unloaded have a pretty good same speed as the electronic that control them individually, despite the age, is good in my opinion.

Under the load also I have well synchro them with pulleys diameter, belt tension. Off course there are some variation due to many factors such as belt precision in roundness, in length, in the motors itself. But my motor have a variation of the speed plus minus 0.1 or 0.2 RPM out of the 360 RPM unloaded and I consider it pretty good. Sure you may get better but......
Attach the pic of the 2 motors that have 90mm rotor ( not so small ) flat type being brushless with outside rotor.

Next week I will have my platter bearing re made therefore I will have data with the complete unit. At the present I just run the fly wheel unit without the platter and after I used the Cera Tec additive I got at cold some more RPM immediately ( not enough for me ) and tehmax speed in warnm state is the same.

Keeping posted and Tks to all.

Adelmo


Hi,

Today I checked again the two motors RPM, I loaded only with the fly wheel and their respective speed in both motors is 360.4 RPM or 360.5 RPM. The RPM variation is just 0.1 RPM for both motors, I think they are good motors with good torque for this application and good electronic control as well though they do not have speed adjustment as I do not know how to implement in the electronic card of each motor.

Next week i will check again the RPM loading with platter belts ( now the platter bearing under maintenance while I am re making the bottom thrust plate ) but I think also with full load will not change this motors RPM result.

Seems there is a difference in RPM in the Fly Wheel VS the motors RPM. Not big but is there. I will investigate more on this..........

Perhaps I need to change the motor s pulley contact surface with the belt. Now the motor pulley do not have a round belt s groove, just a flat surface, therefore might happen too less contact and some loss of RPM in cold start. The reason to have the motor s pulley with flat belt contact surface and the Fly Wheel pulley with round grooved belt contact surface is that in this case the belt is all the time perfect self centring without any lateral force.


Rgds

Adelmo
 
Firebaugh main bearing

Hello everyone,

I am getting tired of reading about improvements of existing turntable bearings. Increasing their precision will only make them more expensive.

Please put your thinking caps on and design a turntable bearing that is ultra simple and ultra low cost at the same time! William Firebough designed such a bearing in his turntable design.

I will attempt it myself in 2022.

Sincerely,

Ralf
Hi, I'm very interested in your approach to the problem. Any link about the construction details of such a triangular main bearing?
Tks
 
HI,

Just an update to the Fly Wheel bearing heater.

I just received the below parts so I will try to implement them on the bearing:

Heater cloth pad 5V DC to wrap around the bearing house. Their temp I suppose is 30 to 35 Celsius degree, I think enough for this application.
Temperature controller with sensor that will cut the heating when pre set temp is reached.

Perhaps this system can be kept on all the time or just turn on few seconds-minutes before to play LPs, depending on the heating time and off course if shall work well.

Now I need to figure its fitting, connections and needed switches to be added...

Rgds

Adelmo
 

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I agree with others that the set up appears to be lacking torque. The motors themselves might have enough torque but how to transfer that torque to the platter (with its existing mass, bearing quality, lube, etc...) is questionable. I am not against belt drive, despite my username, but I am against an elastic rubber belt wrapping around a small circumference. And then a flywheel driving the platter with another elastic rubber belt. No matter how precise the electronics are in the motor controller, the belt compliance would surely knock off all the precision. Any turntable requiring 40 minutes to get up to speed is not about precision and it also requires a user with the patience of a saint!
 
Hi Direct Drive,

Today upon the arrival of the Temp Controller I checked what is the fly wheel bearing temperature before start and after intensive spinning.
Obviously before start was similar to the room temperature, abut 21.5 Celsius . After intensive spinning the temperature set steady at 31.5 Celsius. Therefore that si the temperature I can run steady RPM immediately, so my goal is to achieve immediately at the start up of the TT that condition and I shall not need to wait 45 minutes.

Regarding the steady speed reached that condition it is steady. I checked with a laser tachometer while playing LPs from beginning to the end.

Regarding the diameter of the pulleys, mine are not big, but neither small and allow me to say that they are much bigger than many well reputed and costly TT. My pulleys diameter are about 30mm diam.

It is said and I believe it is true that Rim drive or Idler drive have more punch, more dynamic than a TT belt drive. However here I am trying to improve a belt drive TT and not trying to beat the Rim or Idle drive on those 2 issue. Though I believe belt TT have a good low rumble comparing to the others drives and take away such rumble for those TT takes soooo many energy and the solution shall be pretty costly as well, if there is a an effective solution for it.

To drive my fly wheel unit I have tried 2 belts with 2.2mm diam, 2.3mm diam, 2.4mm diam and 2.5mm diam, of course the belt length amongst was taking in consideration the different diameter. In my opinion the best amongst them is the 2.4mm that have relatively low amount of RPM loss from the theoretical mat count and reasonable stiffness VS vibration, in my opinion a good compromise. Also the rotation of my motors is pretty smooth and vibration less.

For the platter belt there are well reputed TT manufacturer with heavy platter using a single rubber belt 1.5mm diameter that in my opinion is too soft to drive a heavy platter. In my opinion at least 2 belts are needed as minimum to drive those platter.

I plan to use 3 belts instead. VPI uses 2 belts. Not sure if there is any difference between 2 or 3 belt as not ready test yet.

Mylar belt is said to be better, but on the other side do they transmit more vibrations compared to rubber belt? After All in the motor drive for TT I think does not exist a perfect world and some compromise need to be reached and accepted.

My present goal with my fly wheel drive are:

get steady 33.33 RPM without the need to wait so long, I have the steady RPM but the waiting time is too long.

If above not achieved with the bearing heater and temp controller I will step back to the single motor drive without fly wheel and test it with 3 belts and perhaps Mylar flat belt.

I still believe that bearing temperature change the bearing allowance as other TT manufacturer says. By the way, did anyone ever checked the bearing temperature before start and after let s say 3 hour spinning? You might be surprised of the result, unless the bearing is really too loosen in the allowance, but in that case in my opinion there is LP information loss not so acceptable.

Hope tomorrow I shall get my platter new thrust bottom plate done from the Lathe guy ( today he did not make it yet ) so I shall finish in few days the heating and see if it is working as I hope.

Another check I may do in the platter bearing ( not the fly wheel one ) is to test a Peek thrust plate instead of the bronze one. It is said as lower rumble, this time I have the opportunity to make this test as platter bearing disassembled.


Tks n rgds for the support, appreciate it.

Adelmo
 
My TD-124 took a while to come up to speed despite the usual fixes. It is located in my chilly basement.
The plinth is two watercut granite surface plates so I ran two reptile cage heating pads under the turntable to allow more rapid speed stabilization.
They are plugged in all the time keeping things a few degrees above the ambient temp. Seems to work.

MFZhhM0.jpg
 
HI WntrMute2,

Good to hear that I am not alone in heating the TT bearing and it has some positive result to the speed between cold and normal spinning state.

Easier solution yours. Mine is similar, instead I use 2 small cloth heater ( usually are for gloves ) and wrap them around the bearing house, I have added a temp controller with the temp sensor that switch off the heater when no need. Therefore I can set the maximum temperature of the bearing and in gas etc bearing would be warm already the heater keep off.

Today I have made the electrical connection and fitted the temp sensor of the temp controller with an aluminium ring. Electrically all works, now I need to tune the temp setting of the controller.

Unfortunately when I was ready to make a more serious spinning test the right motor s rotor has some noise, is touching something, perhaps some cable as with this tweak I have increased them inside the pod. Need to figure it out.

Also I need to make a small case for the temp controller, at the present is hanging with its wires outside the motor pod.

My goal is to have the TT ready with steady speed at 33.33RPM in no more than 10 minutes in case I shall not keep on all the time the heater. That would be acceptable for me since 10 minutes is about the time I need to switch on the Amp, the pre phono, put the Lp in the platter, take away the speakers cover....

In case I decide to keep on all the time the TT shall be ready immediately if the system work well, shall see...

Hope this evening the lathe guy call me saying the new Platter bearing s thrust plate is ready for collection so tomorrow I shall spin LPs.

Tks n rgds.

Adelmo
 
Hi All,

Finally I received the Platter s bearing new thrust pad. I made a better wires lay out on the inner motor pod and checked the system with the bearing heater.

I start the TT, switch the Pre Phono on, the Amp on, put the Lp on the platter and the TT have already reached the steady RPM of 33.33. The heating pads and temp controller works and I do not need to wait 45 minutes as before before the TT reach the 33.33 RPM:
Once the bearing has reached the standard temp that at the present is 30.5 Celsius seems it is not increasing anymore. We shall see in hot summer.

Now I need to make some cosmetic work to integrate the Temp Controller in the motor pod.

Rgds

Adelmo