Horizontal and Vertical sensetivity of Tonearm: How to baseline

[sudhirbhosale]

Hi all

I am working on building indigenous 100% wooden turntable. Pl see attached picture, plinth is ready. Current version have motor and platter taken from cheap Aiwa TT (Wooden platter design in progress, which will replace current one).
Now while designing tonearm I would like to measure and test tonearm movement. Fir this, I need to baseline tonearm movement sensitivity i.e. minimum force needed to cause movement (lower is better). I purchased Technics SLQ2000, against which I would measure performance of my TA. (I understand that these are not only success parameters)

I have two issues:
1. How to find out if current TA is perfect i.e. it's bearings Woking smooth i.e. friction within limit, so no need to service:
I found way out. Make TA perfectly horizontal by adjusting counterweight. Took strip of paper exact 1gm weight. Kept the folded paper strip on head. Head comes down. Then cut the strip half repeat process till head don't come down. That means that is minimum weight needed for vertical TA movement. Now I will measure same with brand new turntable if weight comes close then I can conclude that TA bearing don't have friction more than threshold.

2 My issue: How to do this to measure horizontal movement sensitivity?

Do TA bearings need oiling ? Or have any recommended dry method of lubrication i.e. any friction reducing chemical powder? What would indicate that TA bearing need servicing?

Thanks
Hi all

I am working on building indigenous 100% wooden turntable. Pl see attached picture, plinth is ready. Current version have motor and platter taken from cheap Aiwa TT (Wooden platter design in progress, which will replace current one).
Now while designing tonearm I would like to measure and test tonearm movement. Fir this, I need to baseline tonearm movement sensitivity i.e. minimum force needed to cause movement (lower is better). I purchased Technics SLQ2000, against which I would measure performance of my TA. (I understand that these are not only success parameters)

I have two issues:
1. How to find out if current TA is perfect i.e. it's bearings Woking smooth i.e. friction within limit, so no need to service:
I found way out. Make TA perfectly horizontal by adjusting counterweight. Took strip of paper exact 1gm weight. Kept the folded paper strip on head. Head comes down. Then cut the strip half repeat process till head don't come down. That means that is minimum weight needed for vertical TA movement. Now I will measure same with brand new turntable if weight comes close then I can conclude that TA bearing don't have friction more than threshold.

2 My issue: How to do this to measure horizontal movement sensitivity?

Do TA bearings need oiling ? Or have any recommended dry method of lubrication i.e. any friction reducing chemical powder? What would indicate that TA bearing need servicing?

Thanks

 

[Hiten]

Depending on your tonearm design the friction (I suppose thats what you meant by sensitivity) is comparatively less important. For example for vertical movement a little friction will help in damping the record warps (small or major). This helps in tracking. The horizontal movement can be experimented with some trick which is to put a piece of small paper and blow it with air from mouth (Search internet for proper method). (The tonearm should move instead of paper.) What type of design you are using to build a tonearm? Ideal tonearm should be stiff, with good damping properties. Biggest problem with typical tonearms is damping resonances and vibrations and having some mechanism to compensate variable skating force across the record. In the past I have collected lots of articles on tonearm design. Give me time I will post it here. I guess more than friction you should worry about tonearm weight, mass distribution, and damping resonances and vibrations. As for lubrication, no lubrication is required if you are building gimbal bearing tonearm from old salvaged turbtable just clean them and keep them dry. Otherwise dust would collect overtime and will obstruct free movement. Mind you they use pretty small size ball bearings. For a start you can build a pivoted tonearm which simple and easy to build.
Regards.

 

[jls001]

Building a gimballed tonearm is a serious undertaking. An unipivot would be technically much easier to achieve. My ballpen tip unipivot continues to give me happiness.

For testing horizontal sensitivity, I recall what Rajiv on the forum had advised me long ago - balance the tonearm perfectly and then place a 1 cm x 1 cm piece of paper on the headshell. Allow it to settle to steady state and gently blow air with your mouth. Blow it gently so that the paper doesn't fall off from the headshell BUT the tiny force of air must move the entire arm gently in the direction of the air.

Another rougher method is to hold the arm gently by the headshell and move it slowly in the horizontal direction, left and right, while feeling for any notchiness in the movement. The movement must be smooth and effortless.