Help! - Doorway dolly question

[Bob Gruen]

I'm in the process of refurbing / modding an old doorway dolly and I have a question about tire pressures. The dolly has two tires on each corner, and I added a Matthews seat assembly that can place the cameraman above and of the four corners of the dolly.

The original pneumatic tires are old, dry-rotted, and flat-spotted, so I bought new tires hoping it would help with the tripod head wiggling back and fourth when the dolly is moved.

The new tires are not very round, so the head still jiggles back and fourth. They have inner tubes so I can set the pressure from a couple of PSI up to 45 PSI. So my question is: are these types of tires generally run soft, firm, or rock hard? If they are run soft do you use a few sandbags to counterbalance the camera operator's weight?

Thanks,

Bob

 

[filmat11]

The new tires are not very round, so the head still jiggles back and fourth. If they (THE TIRES) are run soft do you use a few sandbags to counterbalance the camera operator's weight?

Thanks,

Bob[/QUOTE]
Not very round ?...lol In a situation like you describe, there are two schools of thought on tire pressure. It's not always convient to carry around a tire pump or powered inflator of some kind, but weight and center of gravity on a dolly makes a big difference.
I have even used a Professional, Fischer Dolly, where we needed to add sand bags to one side of the dolly to accomadate the large, heavy set DP, his offset seat+ extension, and the heavy Sony Varicam with prime lenes. Of course the dolly wheels where not really an issue here, but adding weight to the dolly will help maintain a smoother ride. Keep in mind that a Fischer dolly is well over 300 lbs.
Placement of the tripod and OPERATOR on a small dolly can create varying results, especially if the operator should need to move his/her feet or shift their weight during a camera's panning move. A simply move can give a very jerky, uneven result.
Tire pressure can be daunting especially dependant on what surface your crossing .
Carpet,sand, tiled floors, grass, or concrete may indeed require different tire pressures.
Less air for outdoor-uneven surfaces, and more for hard surface. Sometimes the tires can "whine " or make a sound that is not too friendly to the audio dept. Tire pressure and the weight carried will contribute to this, even the age of the tire and of course the surface it's on...
I would also look into different tires, especially if they are not exactely like the ones that where there in the beginning. My 2 cents..