Nude Turntable Project

09-02-13: Ct0517
Richard – thanks for turning me onto the “alpha leg” :^)
I may try it with the sp10 setup later. One Stainless Steel leg and 3 PVC or other slower material legs.

With regard to your proposed 4 legged experiment, it appears that the physics and engineering principles underpinning the optimal mechanical grounding principles have been overlooked.
A tripod is inherently more stable than 4 legs. A tripod distributes the weight evenly around the centre of gravity across its 3 legs. This is why cameras and theodolites are usually mounted on tripods, they are more stable. Note also your Verdier TT uses 3 feet to take advantage of this principle.
The use of a grounding leg plus 2 non grounding legs to achieve a single point mechanical grounding works far more effectively with a tripod ( 3 legged ) configuration. The Goldmund Reference Technical Report in the Absolute Sound magazine, issue 51 has an informative discussion for those wishing to understand the principles of mechanical grounding.

Thanks Dover. Sometimes I get ahead of myself when I get hold of an new idea. I tend to get a little giddy and feeling like a little kid. My version 5 will support 3 legs not a problem as they are screwed in on both sides. Project added to the overall list. Its no. 14 right behind no. 13 – Build wife new kitchen :^( I am thinking of outsourcing this project so I can play with my audio stuff more this winter.

A tripod is inherently more stable than 4 legs.

Not true........try sitting on a 3 legged stool?
Four legs is generally accepted for stability in chairs.......but in office chairs on castors.......even 4 castors is not sufficient for stability with 5 castors being mandated for safety in the workplace.

The reason 3 supports is often used for turntables......is that the 3 supports will ALWAYS make contact on the supporting structure.
With 4 supports......depending on the load of the turntable.....only 3 may be making full contact.
With 4 legged chairs......a person's weight will 'spread' the bottom of the legs so that all 4 legs are weight-bearing whilst without the load of an occupant......only 3 legs may be fully in contact with the ground?

Hi Dover,

"A tripod is inherently more stable than 4 legs." I've read variations on your statement many times. But I wonder under which conditions it is true?

Is a tricycle more stable than a (4 wheel) wagon? Think about which one would be easier to tip over if making a sharp turn. But if that is an unfair example for a stationary object, then which one would be easier to tip with a shift in loaded mass while otherwise stationary.

As for camera tri-pods, I believe there are two reasons for their design. First, they are lighter and more portable than quad-pods, all else being equal.

But it is their second design feature that really gives the advantage. The three legs are splayed well outside the center point of the mass they support by angles. And I think it is the angles of the legs which provide the stability, rather than the number three.

Said another way (sorry, I'm trying to find the best way to express my sense of this issue and my question), if we have two small tables of the same weight and height, one has three vertical legs, the other four vertical legs, which will be more stable? If you push on the edge of the top surface, midway between any two legs of both tables, which one is more likely to tip?

Thanks Halcro, you beat me to it. .^)