I've got a pneumatic brake wheel, about 2 1/2" diam. The air valve is apparently an on/off type where the lever moves at right angles to the valve-rather than the normal 'Robart' type. The drum of course uses 'O' rings. Don't know the make. When you 'engage' the brake valve, it locks up the wheel, and when you turn the air valve off, it stays locked up. Should it immediately release the wheel? I wanted to use it on a nose wheel on a plane I'm building. Do you need a proportional valve or is there something wrong with the drum, 'O' ring( it's a new ring).