Re: Air valve

I doubt the caboose valve is anything you would want for an engine brake.

Both NYAB and Wabco offered a variety of straight air or independent brakes over the years. I believe the Wabco straight air valve used with schedule A-1 and similar to the one used by NYAB LT is an S3 or S3A. There was a nice little self lapping valve used on small diesels without train air called an SA-2. Not sure how easy it would be to obtain any of these or maintain them as they are obsolete.

The most common independent brake valve these days is the SA-26. You could fabricate the pipe bracket for it. It is self-lapping (output pressure varies according to handle position) and requires three connections: Main Reservoir in (air supply) and output to the brake cylinder (typically 30-50# maximum). The third connection is for an actuating pipe and depressing the handle connects it to the main reservoir. Maybe use for sanders? The exhaust is sometimes piped to a position outside the cab. These are available from any locomotive air brake shop and do sometimes show upon ebay for a few hundred bucks.

Another possibility to consider is a Controlair valve. This was originally a Wabco line of industrial air controls that was later sold to Rexroth. I would suggest you look at the H-2-FX. There are several versions of each valve as to how they control the air, auxiliary ports, and pressure ranges. These are commonly used for boat throttles and drilling rig controls. There are many distributors that handle these (Google is your friend) but new ones are a little spendy. They do show up on ebay often but be sure which version you're buying.

They also have small Rotair valve which is a handle controlled 3-way valve available in 1/8, 1/4 and 3/8. A closed center version should give you release, lap and application imitating the older straight air valves.

There is also the S series of relay vales in 3/8, 1/2, 3/4 and 1" which is a 1:1 relay valve. If the controlling valve doesn't have the capacity for the size of the brake cylinders, piloting an S relay valve would take care of the problem.