So I got a car mount from Filmtools.

This one : http://www.filmtools.com/filmedweigca.html


It has 3 vacuum cups, heavy stainless rods etc.

I've mounted a Canon XH A1 onto the trunk of a car. Speeding around 100 km/h. Got disappointing results : lots of harmonic vibration...

Is there a particular technique for mounting this car-mount? Should the vacuum cups be as far spread out as possible?
Any hints...?

The only time I've ever rigged my camera to my car was when I used a Bogen video head with one of these:

http://www.videogear.co.uk/images/uploads/superclamp.gif

I clamped it to the door and drove around. This is what I got:

http://vids.myspace.com/index.cfm?fuseaction=vids.individual&VideoID=2244658

The specific vehicle you use will also have an effect on the results. When I shot this, I was driving a '91 VW Jetta, and it was very smooth. Now I drive a Ford Ranger 4x4, and there's virtually no smoothness to it whatsoever.

I can't remember if I posted this previously but here it is - two cannabalised West Coast truck mirror frames and some extra tube, halves cut out from automotive drive shafts and angle iron.

Fits into car window frame either inside or out. Should not be overtightened of the door gets bent out of shape. Lanyard is tied so that if it works loose i does not hit the road.

http://www.dvinfo.net/media/hart/Westcoast%20Window%20%20Mount.JPG

Hi Eugene
I am using a similar homemade system for my "roadmovies". I can post a picture of the setup if you are interested. It do not have so many joints. I have driven hundreds of miles with this system attached. Outside, on the side, inside the car, it have never failed. I try to avoid the hood to support the rig, because the hood tends to vibrate. Big surfaces of thin metal, and sometimes loose hinges makes the rig vibrate. And you do not make it easier at 100km/t. I never drive that fast, if I need, I speed it up in post. If you hold your hand out of the window in 100 km/t, you know what battle the camera and rig must fight.
I try to hold the speed at 50 - 60 km/t.
I usually attach the rig with two cups on the upper part of the front window, an one on the roof. As near to a profile in the roof as possible. And if I have to mount it on the hood, I make sure the hinges and lock have no slack, and mount it as close to corners or profiles as possible.
If I had to drive that fast, I would make an aerodynamic enclosure. A good model airplane builder can help.
And always secure the rig with a strap.

You can see an example in the video: Eksempel 1 Atlanterhavsveien on this site: http://www.picturenorway.no/index.html

And take care.
Arnt