Steady rest wheels and construction
That is a great looking steady you made. It looks truly "steady." Any way the arms can move or vibrate will cause problems so that "steady" is important.
Lets see if I can remember all of the points that might make you want to do a bit of modifying:
Round edged wheels are definitely preferred. Flat wheels will mark any wood that is not a perfect cylinder. If the wood is tapered, only the corner of the wheel (corner = tread to sidewall corner in automobile tire butchered language) will touch the wood. The rest of the tire will be in air.
Flat edged wheels will leave two marks on the wood if you have them located in a cove in the turning. The two outer edges of the wheels will compress wood while the center of the wheel rides on air.
Round edged wheels will also mark the wood if the pressure is too tight on the wood. If possible use the steady on part of the wood that will have some more turning done to it or will have some significant sanding.
The wheels for the small fold-up scooters the kids ride and do tricks on are round edged, have good bearings, and are available many places. They are also quite inexpensive.
Three wheels will, as far as I know, do everything four wheels will do and are one less thing to adjust for minimum wood compression.
I designed my first steady rest to take up to 5 inch diameter wood. Well it was fine for small things like pens and thin candle sticks. However, even though I had a registration pin in addition to my adjusting (and tightening) mechanism, there was too much play for anything of any size or mass. I would tighten the heck out of things but the adjustment would not hold; an arm would move a fraction of a mm in the direction of rotation and throw the center of rotation of the wood off just enough to be trouble.
Enjoy,
JimB