Sunday, May 19, 2013

A Question of Equilibrium or Why is my Bus Tilting

My bus has a problem of equilibrium.  The bus’s suspension is based on air.  There are air bags on every corner on the bus.  There are two air bags per wheel.  The air bags are an extension of an air chamber that sits above the axles.  This chamber is basically a box about three feet long attached to the frame of the bus that straddles the axle.  There are air bags are on both ends of the box and these isolate the axles from the frame of the bus.  

When the bus airs up, the compressor fills various air tanks on the bus that act as reserves for the individual air chambers and bags.  The air fills the chambers and lifts the bus to operating height.  It is normal that the bus will air down over a period of time.  If you let the bus sit, it will settle as the air leaks out of the various chambers.  The problem is that the air is leaking from the chambers at different rates.  I was told by the previous owner that there was a leak in the rear chambers of the bus and in fact the rear of the bus does settle out much faster than the front. 

The bus also has a leveling system.  This was once a Greyhound bus.  Because weight in a bus can vary from side to side, the bus was designed with a system that allowed the bus to compensate for more weight on one side and level the bus.  My bus is also settling at different rates side to side.  In other words, as the bus settles, it leans to one side.  

I need to find the leak in the back and determine how best to fix it.  I also need to discovery why the bus leans as it airs down.  This is most likely causes by a defective valve that helps level the bus side to side.  One more thing to sort out as the adventure continues.