Thread: Ideas for shaking/vibrating a car

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I have a 1940 Chevrolet I'm going to use for a prop and need some advice on what to use to make it shake. The goals of the prop:

Skeleton in driver's seat with a triggered strobe to light it up
Red lights in the headlamps to fade in/out
Fog machine under the car
ooga horn that cranks up for a couple of short blasts
Car shakes/trembles when activated. (need help here)

I can program this stuff pretty easily with a proximity sensor and an Arduino to get the timing right, the part I'm frustrated about the most is the shaking bit. It won't take a whole lot to shake the car since it's a survivor from 1940 with flexible tires and 70 year old springs and shocks, but the question is - how to do it?

My thought process of the day involved a reciprocating saw attached to a drawer (on ball bearing rails) with maybe a 5 gallon bucket of water in the drawer or something. Would a cheap Harbor Freight recip saw move 5 gallons of water like that on ball bearings or is 5 gallons of water too heavy?

The effect I'm looking for is more of a rattle - doors loosely closed that click and clack back and forth, little bit of movement from the skeleton, etc.

How would you tackle this scenario?

It may be shaky for a car, but it's still a car - that's a lot of mass to move. I doubt the reciprocating saw would move enough weight aggressively enough to give you the effect you're looking for, but I could be wrong. If it's not too tough to set it up you might give it a try. The trick would be getting your mass as far away from the ground as possible. It's much easier to shake the car from the roof than the frame.
Could you get the effect you're looking for by shaking just the doors & skelly? The reciprocating saw would probably move them much easier than the whole car.

you might consider a 'shaker' like this: http://www.parts-express.com/pe/show...number=299-028

It is a transducer that you connect to your audio source just like you would a subwoofer, but instead of a speaker this thing is attached to a chair (or in your case the body of the car) and it shakes it. Depending on the frequency of your audio file you could probably create all sorts of effects with something like this.

A washing machine agitator motor should do the trick. If you can find one that moves up and down like the older ones from the 70s and 80s it would have plenty of kick. Should be fairly easy to control as well I would think.

After spending a few minutes with the car and a 20lb dumbbell, I don't think it's enough to do anything substantial. I did grab the car from several points and shook it around to try and find the "sweet spot" and may have a solution - and it involves the previous suggestion of a washing machine motor and transmission.

Take a 1/2" sheet of plywood, park the rear tires of the car on it to hold it in place. Attached to that would be the washing machine motor and transmission under the rear bumper on the passenger's side. With the transmission in agitation mode, a rod attached to the output of the transmission would go diagonally from the motor/transmission on the ground over to the bumper mounting point on the driver's side. If the agitator will give 2-3 inches of movement, that would be plenty to get the car to yaw back and forth. It took surprisingly little effort with one hand to get the car to yaw violently back and forth.

I'm going to call a couple of appliance repair shops and see if I can find a used motor/transmission setup for this.

Thanks for the tips, I'll keep the thread updated.

I have done this several years ago with and old packard hearse I had.. was a lot more mass to move.

used a 1 hp motor 1500 RPM or more.. then welded a fram to the center floor board of the cat that would hold the motor about 2 inches off the floor for clearance.

I used a 12 inch pully that on one edge I welded two 3 oz wieghts.

it is enough wieght to make the car rock but not tear up the motor at high speed for short bursts.

doing this I went thru many trial and error phases to come up with this,, and the best mounting point was the center of the car. as it created equal mass to move and allowed the waves of energy to travel equally. this created some good rocking and rattles

make sure the mount is solid, very solid. or it will walk/break/ bounce around the inside of the car body

Car shaking hmmm? How about two teenagers in the back seat?

If you're going to that much trouble, would a little audio action to the scene reinforce the perceived shaking effect? ...grating metal, squeaking springs, ghostly groans, etc. hmmmm....maybe some music from the movie "Christine"?...oh, I know...the song "Shake, Rattle & Roll"! ha.