Helical Strakes

[blackparticle]

Has anyone seen Richard Hammonds Engineering Connections on BBC? Episode 4 to be precise, the one about the Greek suspension bridge.

In it is an experiment to show what happens to metal tubes with low-level winds and the vortices that cause vibration. And then what happens when you apply a helical strake.

I watched it.. and then looked at the legs of my tripod.. and then the telescopes..

I'm now at the chin scratching and pondering stage.

[Digz]

I caught the end of that and thought that a the helical strakes were a wonderful idea, never crossed my mind to apply them to the scope and tripod legs. I wonder how effective they would be?

[Psychobilly]

Dont think you would suffer the same wind induced vibrations in a tripod leg.. probably better of with a decent set of AV pads if you dont already have them...

[Digz]

hey dude, mmmm, I guess your right as the tripod leg is fixed and triangulated. I wonder if it would work on a tube?

As for AV pads I havent actually got any and tbh not thought about them until now......

[Psychobilly]

hey dude, mmmm, I guess your right as the tripod leg is fixed and triangulated. I wonder if it would work on a tube?

As for AV pads I havent actually got any and tbh not thought about them until now......

AV pads are an "essential" accessory when I am away from the obs with the tripod... did drive back to a fairly local dark site when i left one behind once... I use the "proper" sorobothane ones rather than the washing machine variety

couple of other VIV Damping solutions in this paper...

http://www.benthamscience.com/meng/samples/meng%201-1/Kumar.pdf

[blackparticle]

From what I understand the vibration is caused by changes in air-pressure caused by faster currents moving past slow moving air pockets. It seems all circular tubes will be affected to some degree by this, regardless of being fixed or not.

At what point any vibration causes pixel deviation is all down to focal length, mount stability and overall weight I suppose.