???
Stew: Can You be more exactly, what do You mean, “.....the lateral torque on the stylus cantilever can be reduced significantly. Something like a minimum of 48% and a maximum of 84%...... “ ?
Are You taking about antiskating force? Or is it vibration force?
You tell use “...the lateral torque on the stylus cantilever can be reduced significantly.”
Can You measure this?
Regards
GiK
Stew: Can You be more exactly, what do You mean, “.....the lateral torque on the stylus cantilever can be reduced significantly. Something like a minimum of 48% and a maximum of 84%...... “ ?
Are You taking about antiskating force? Or is it vibration force?
You tell use “...the lateral torque on the stylus cantilever can be reduced significantly.”
Can You measure this?
Regards
GiK
Hi there, just looked at this PDF on the Disk drive motor. Cool So I pulled one apart and it all looks easy enough. What I am a little unclear of is how do I know what the RPM of the motor is. How did the guy doing the write up know?
It's all good to use the same diameter of pulley as a linn but if the motor is not spinning the correct speed then isn't is just going to be out?
I understand the dialing in with a parallel variable resistor but wouldn't you need some sort of strobe light to measure the rpm?
Is this how the guy did it?
Can someone help me figure out the rpm? Do I need to build some sort of strobe rpm counter?
It's all good to use the same diameter of pulley as a linn but if the motor is not spinning the correct speed then isn't is just going to be out?
I understand the dialing in with a parallel variable resistor but wouldn't you need some sort of strobe light to measure the rpm?
Is this how the guy did it?
Can someone help me figure out the rpm? Do I need to build some sort of strobe rpm counter?
Diskette motors run at 300rpm (I think - do a search). I am very doubtful that a simple resistor change will alter the speed properly. Such systems generally have a phase-locked loop and the only way of changing speed is to change the reference frequency. An electronics engineer would modify the existing electronics or design new electronics. A mechanical engineer would make a new pulley.
You can check the speed of a turntable using a strobe disc and strobe light. If you do a search on this forum you will find that I gave details of how to make an accurate strobe light.
You can check the speed of a turntable using a strobe disc and strobe light. If you do a search on this forum you will find that I gave details of how to make an accurate strobe light.
Noob - I answered my own question by finding the brand name (TEAC) and looking up the specs in Google. Nice So now I know mine runs at 300rpm. I couldn't see it originally under the dim desk light cause it was in Fluro Yellow!
A bit more research shows the way floppies work. They spin at one constant speed. Mine is 300rpm but apparently some spin at 360 and 600rpm.
This wasn't clearly stated in the original PDF about modifying one of these motors.
Anyhoo that's why the internet if fun and life is interesting.
Last night I was a stumbling mess crying in the fetal position distraught from my lack of knowledge. Now I am heaps smarter and I think all my muscles have grown a little too.
A bit more research shows the way floppies work. They spin at one constant speed. Mine is 300rpm but apparently some spin at 360 and 600rpm.
This wasn't clearly stated in the original PDF about modifying one of these motors.
Anyhoo that's why the internet if fun and life is interesting.
Last night I was a stumbling mess crying in the fetal position distraught from my lack of knowledge. Now I am heaps smarter and I think all my muscles have grown a little too.
Good info on the rotational speed of the diskette drives - so I'll have to look up the speed of the drive I want to use to get an accurate diameter for the pulley spindle needed!
So let's see if the speed is 300 rpm & we want to cut this down to 33 rpm we need a ratio of 9.09 so this would be the ratio of the diameter of the platter to the diameter of the pulley or am I missing something? The pulley size in the Audio Origami looks a lot smaller than 1/9 the diameter of the platter!
If using the diskette drive with an idler wheel rather than a belt does the same formula apply - I think it does?
Edit: The real issue would be not being able to easily adjust the rotational speed to some extent. If this was the case then it would require a very accurate pulley diameter for accurate speed!!
So let's see if the speed is 300 rpm & we want to cut this down to 33 rpm we need a ratio of 9.09 so this would be the ratio of the diameter of the platter to the diameter of the pulley or am I missing something? The pulley size in the Audio Origami looks a lot smaller than 1/9 the diameter of the platter!
If using the diskette drive with an idler wheel rather than a belt does the same formula apply - I think it does?
Edit: The real issue would be not being able to easily adjust the rotational speed to some extent. If this was the case then it would require a very accurate pulley diameter for accurate speed!!
jkeny said:
Here is an example of how to calculate pulley diameter.
This shows a 4" diameter subplatter being driven. Keep in mind that you also have to factor in what type of belt you are using.
The example below would be used for a flat belt. If you are using a "grooved" pulley for a string drive or round belt, you have to calculate the groove angle and contact area where the belt is being driven to get an accurate pulley size. I normally use the formula to get me close and then fine-tune the final diameter by measuring actual speed with the pulley on the motor.
Motor speed x motor pulley diameter divided by hub diameter = R.P.M.
Example:
Motor speed = 300 RPM
Hub size = 4.000"
Small pulley = 0.444" (33.3 rpm)
Small pulley = 0.600" (45 rpm)
Thanks Vinyl-addict,
I was calculating the whole thing based on driving the rim of the platter rather than a hub so I see why the pulley in the Audio Origami article looked wrong to me.
So if driving the rim & the platter size is 13" the motor pulley diameter would be 1.443". Or this would also be the diameter of an idler wheel if doing it directly against the rim & not via a belt. I'm thinking that an idler wheel would be easier to adjust the diameter of having an outside rim of rubber - using different rubber rim thickness's would allow easier adjustment of driver wheel diameter than turning aluminium pulleys.
Just thinking out loud - does this make sense?
I haven't heard anybody using this diskette motor approach as an idler drive - wonder why? The Lenco TTs prove that idler technology works well - kinda half way between belt & DD
I was calculating the whole thing based on driving the rim of the platter rather than a hub so I see why the pulley in the Audio Origami article looked wrong to me.
So if driving the rim & the platter size is 13" the motor pulley diameter would be 1.443". Or this would also be the diameter of an idler wheel if doing it directly against the rim & not via a belt. I'm thinking that an idler wheel would be easier to adjust the diameter of having an outside rim of rubber - using different rubber rim thickness's would allow easier adjustment of driver wheel diameter than turning aluminium pulleys.
Just thinking out loud - does this make sense?
I haven't heard anybody using this diskette motor approach as an idler drive - wonder why? The Lenco TTs prove that idler technology works well - kinda half way between belt & DD
jkeny said:
I like to use 300RPM motors when driving smaller diameters because when the pulley diameter starts becoming in excess of 1.25", you have to really nail concentricity and make sure the pulley fits nicely with the motor shaft.
The larger the diameter of the pulley, the more exagerated the eccentricity error will be, so just make sure the bore and o.d. of the pulley are machined at the same time for best concentricity and don't ream the bore. Finish bore the I.D. and the turn the O.D. Don't take shortcuts if you want the best results.
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