[kieckerjan]

Tangential, but I was once told a story that seems fitting here. It was told to me by a mechanical engineer who was educated at Eindhoven Technical University in the Netherlands.

He claimed that in the early days there was a lecturer or professor there that, at least in Eindhoven, was very important to his field of expertise. If I understood him correctly, this prof's ideas about engineering mechanical systems revolved around restricting the degrees of freedom as much as possible. A three legged table cannot wobble, but a four legged table can and usually does because it is overdetermined. In mechanical systems (for instance sensitive optical mechanics) reducing "wobble" is key. And the best way to reduce wobble is to make sure it cannot occur.

Here it gets interesting. My source claimed that this professor had laid down his ideas in a standard work in Dutch, which was never translated in another language, restricting its influence to Dutch mechanical engineers. He also claimed it is not a coincidence that Philips and later ASML took an early lead in designing optical systems.

Not sure if it is true, but an interesting story nonetheless.

[hydrogen7800]

This sounds like the principle of "designing for exact constraint". You learn about under-constrained and over-constrained typically in a strength and materials course in ME undergrad. An simple case of exactly constrained is a 2D beam with a pin/hinge at one end, and a roller support at the other. The pin removes the 2 translational DOF's and the roller removes the third rotational DOF. A beam with a pin/hinge at both ends is over-constrained and is "statically indeterminate" (or over-constrained), which requires you to use other techniques to find the stresses in that beam, such as principle of "virtual work", or some others I've forgotten. For more complex structures, there is a formula which has as its inputs the number of members, number of joints, type of joint, etc, and will give an integer output which will tell you over, exact, or under constrained. Although a 3 legged table will never wobble, they will more easily tip, and the surface of 4 legged table can be considered somewhat flexible, and provide an additional DOF that keeps the legs in good contact with an irregular floor.

[buescher]

Kinematic design for precision mechanics - optical mounts, machine tools, robots, etc - is well known outside of the Dutch literature. It would still be interesting to know who your guy was talking about. Here’s a neat page: https://fab.cba.mit.edu/classes/865.21/topics/mechanical_des... And a nice overview paper from Arizona with a good bibliography: https://wp.optics.arizona.edu/optomech/wp-content/uploads/si...

[lloeki]

> this prof's ideas about engineering mechanical systems revolved around restricting the degrees of freedom as much as possible. A three legged table cannot wobble, but a four legged table can and usually does because it is overdetermined. In mechanical systems (for instance sensitive optical mechanics) reducing "wobble" is key. And the best way to reduce wobble is to make sure it cannot occur.

This is how I was taught mechanical engineering (France, 2000-2005) and not a Dutch in sight.

[kieckerjan]

Fair enough. But I am talking about 50 years ago or so.