wl> The circus train equipment was considered freight. Yes it did have passenger equipped cars but that was it.

My point was that once coverted to circus train use they were no longer "passenger" cars. It's a technicality, yes, but a crucial one when it comes to which set of AAR and/or Federal rules applied. The same is true for all RR business cars.

>The circus train had a 90 lb brake pipe, just like any freight on the SP. The cars all warnings on the outside, "Caution: 90 Pound brake max"

This was for the former "freight" cars (flatcars, etc.) which were set up for a different braking ratios than the former "passenger" cars.

> Well we got over into the yard and the switchman coupled us up. There we sat and sat and sat while the hogger was trying to get an air test. Finally, the Conductor came up, walked over to look at the gauges and grabbed the feed valve, screwed it back down to 90 lbs. Then he plugged the train. Had the hogger pump it back up and plugged it again. By then the Circus Train Trainmaster was up in the cab. It took one more dumping the air before before we could get a decent air test.

> Yup, its freight equipment.

"Freight" has nothing to do with the functioning of an air brake system because all the pressures involved (brake pipe, auxiliary reservoir, and brake cylinder) operate relative to each other, not some fixed number such as "90 psi" or "110 psi". The circus train would have worked just fine at 110 psi. However, the Circus Trainaster was the boss fella, so you had to follow his instructions.