Nude Turntable Project

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. .^)

Hi.

The Gyro testing table had 6 cast iron legs. Five of them were height adjustable with wooden decoupling pads. The sixth leg had no adjustment and it directly coupled with the concrete floor.

The Gyro testing table had 6 cast iron legs. Five of them were height adjustable with wooden decoupling pads. The sixth leg had no adjustment and it directly coupled with the concrete floor.

Interesting

gave this more thought. My current version Sp10/Armpod testing TT is different from the Gyro as it is a rigid structure bolted into the base/plinth. No provisions for height or level adjustments. All height and leveling adjustments are done by the three adjustable AT-616 pneumatic footers under the base/plinth. In this case the actual TT system feet are these footers and I use three.

As noted earlier the ET2 tonearm has its own leveling system independent of these feet for final leveling. I level the platter as best as possible then the tonearm. My SS legs are acting as supports and are not the actual TT system feet. I would want to keep all four for stability and rigidity. Sounds to me like trying this out means changing out one of the AT-616's for an alpha leg ? The one under the tonearm in the pic ?