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Air (Part I)

One of the nice things about the bus is that it has an air system for the air brakes, which means that it has a compressor that runs off the engine with a mechanical pressure regulator and a dehydrator for the system, which doesn’t mean that it makes apple chips, but rather that it helps keep water from building up in the brake lines (which can be a big deal in the winter!). You might ask why this is a nice thing, since your car most likely gets along fine without such things.

Well, first, it offers the possibility of refilling tires if need be, or, if you like, any number of air-powered accessories, like tools (impact hammers/wrenches, drills, jacks, etc.), or an ‘air seat’ for the driver (highly over-rated from my experience on school buses that have them), or air suspension bags (to aid the shocks and smooth the ride), or to run air horns. However, one of the things that our bus didn’t have as part of its air system was an auxiliary tank.

Air brakes for a single unit vehicle only need one tank with three partitions. The first partition (wet tank) is the place where air is stored for future use, and to trap more of the moisture that might have made it through the dehydrator. The second partition feeds from the first tank and serves to provide air to the front brakes, and the third (also fed from the first) provides the air for the rear brakes. This is why, on a vehicle with air brakes, there are either two pressure gauges (one each for the second and third partitions) or a single pressure gauge with two differently colored needles, each indicating one of the two brake partitions. (Multi-unit vehicles with air brakes usually have a separate gauge for the trailer brake tanks.)

Now, some of the people on the Skoolie board had just tapped into the first tank for a ‘service’ air line for tools (or in a pinch, to hook a compressor to, in case the one on the engine failed), but it’s not something to tamper with if you want safe brakes. I wanted to be able to use an air line for tools, as well as run air horns, and have the possibility to upgrade to air suspension bags in the future if we decided we wanted it. In order to do this, we needed an auxiliary tank.

I found an auxiliary tank online that was a 20 gallon one that would fit alongside the air brake tank under the bus. While one might think that this would be a simple matter of running a line between that first partition of the brake tank over to the auxiliary tank, you can’t do that, because there is a maximum amount of time your air brake system can take to get up to “working pressure” of about 85 psi from starting with no pressure. If you hook a 20 gallon tank up to that first partition, you have to bring that whole storage area up to the 85 psi threshold within that minimum time, which just doesn’t work.

Air pressure valve, 85 psi on
Air pressure valve, 85 psi on

In order to get around this problem, I had to install a pressure valve in the line between the two tanks. This valve stays closed until the pressure in the brake tank partitions get up to about 90 psi, then opens, allowing the compressor’s air after that bring the whole system up to pressure over a longer period of time. One of the things that ends up happening here is that I have a lot more air available for my brakes when the system is up to pressure (120 psi), as the 20 gallon tank can feed air back to the brake tank as long as the system pressure is over 85 psi.

The pressure tank I got had a whole lot of ports, but none on what I wanted as the bottom (because of the placement of the ‘feet’ for attaching it), and one on what I wanted as the top, so I ended up having to support it from underneath, rather than bolting it directly to the floor. The location of this port to be facing down was important so that it could be used as a drain to get rid of excess moisture, and I did double-duty in putting in a pressure release valve in, so if the system over-pressured (150 psi +), it would let the excess pressure out and save other elements from stress. , but I could also manually activate it as a drain.

Bedrails can make good structural supports!
Bedrails can make good structural supports!
Building supports for the air tank
Building supports for the air tank

So, one port was the pressure relief valve, another was the air coming in from the brake tank, and, for now, only one port would be used for feeding up through the bus body to two air sounding devices. The first was a Leslie Supertyfon RS-3L that was originally installed on a Conrail Diesel locomotive that my father had acquired somewhere (more on this later). The other was an ‘air chime’ which, when used nautically ends up meaning an air horn, but in this case was the closest I could get to a steam whistle. It channels the compressed air through four different chime pipes, a rich sound compared to the air horn.

The next thing to do was to lift the tank into place, which is actually tougher than it sounds, as I was attaching it to the bottom of the floor and to the side of the bus’ ‘skin’ where it drops down.  In order to hold the tank in place, I decided to use a nice floor-jack and lift it, but this also was trickier than it sounds, as the tank was balanced just so and having the supports catch on the brake tank or the skin of the bus could cause it to tilt and slide off the jack.

Jacking the tank into place
Jacking the tank into place
Lifting the tank into place
Lifting the tank into place

 

 

 

 

 

 

The new tank and pressure regulator in place
The new tank and pressure regulator in place

 

To be continued (in Part II) …

 

And for a really nicely detailed explanation of air brake systems, look to this great Army informational film from 1967:

The trip that never was …

  Before I got the floor finished and the seats in place, I had decided that I wanted to take the bus out for ‘exercise’.  The engine should be run about once a month, and the bus should be moved at least a little to make sure the diesel fuel sloshes about and doesn’t get set for algae and that the tires don’t ‘square’ from staying in one position too long.  (The ‘squaring’ comes form the wires in the radial tires sitting with so much weight on them in one place for a long time.)

  I had planned out a nice route from our house out to Broderick Park on Squaw Island Park by the Buffalo River, and wanted to take my wife, our son, and my mother-in-law.  It was to be the first real ‘passenger trip’ in the bus.  I used the old seat holes and threw two seats in place, right up front behind the driver’s seat, so it was mostly a big empty space, and somewhat loud when on the road, but I thought it would be fun.

The original entry steps.  Well, still the entry steps,
but now a little different …

  It took a little bit to get my mother-in-law up the steps and into the bus.  She had some knee problems, and the bus only had two steps to get in.  At some level, that sounds simple, that she only had to make it up two steps, but those two steps (three, once you count the initial entry or the top step, depending) have to get you from ground level to 42 inches above, which is floor level.  And of course, I’d removed all the seats and the forward ‘wall’ and support railing when doing so.

  But with a couple of concrete blocks and a little wooden step, she got in, my wife and son got in, and we were ready to go.

  We got just outside the gate on our driveway, and I set the parking brake, went and locked up the gate, then got back in and we set off.  Once we had pulled onto the street, however, the air pressure, which normally sits right around 120-125 psi was plummeting, and there was a hissing sound. Well before we even got to the corner, the little ‘wig wag‘ arm let loose and was swinging (as it should have, right at about 80 psi).  I pulled over and set the parking brake so I could get out and try and suss out what was happening.

  Once the parking brake was set, the hissing stopped and the pressure started to rise again.  I took a quick look out and around, but couldn’t find a broken hose or leak, so when the pressure hit 125 again, we started off hoping that it was a fluke and we could go about our trip.

  It wasn’t a fluke.  Once again, the pressure dropped and I decided that we’d just go around the block and stop when necessary to get the air pressure back up, then go again.  Four stops later, we were back in the driveway, everyone was off the bus and I was trying to figure out what was wrong.

That’s not a shadow behind that front left bolt,
that’s missing plastic that cracked out!

  With the wheels chocked and my wife taking the parking brake off while I was outside of the bus, I tracked the hissing to the rear axle, port side.  Climbing under, I found that a port pressure release (as I was to find its name later) was leaking.  I chocked the wheels and go into seeing what I could about the part.  Some scraped knuckles later I had it out and confirmed that it was not a seal, but rather a leak from cracked plastic.

  The port pressure release might look like a simple piece, but it’s tucked way up inside the frame rail with the bolts behind the that go through from the inside to the outside, which means that the nuts are almost inaccessible back behind the dual back tires.   Luckily, with a wrench jammed in on the bolt, one can still, with long arms, blindly work a ratchet to get the nut loose.

The nice, spacious workspace.  The detached lines are
1/2″ air lines that attach to the port pressure release.

   Now, by the time that I got the piece out, it was after hours when the parts department of the local dealership was closed.  I tried to do a parts search to figure out what kind of cost I would be looking for to fix it and get the bus going again, but without knowing the name of the part, that’s really tough.  So I had to wait for the dealership to open and take the part in and hope that they had it.

  While they didn’t have any of my exact make and model, they had an updated part that would meet the needed specs.  It turned out to be a simple part that cost only $22 and they just grabbed off the shelf, so I ended up getting two, just in case one of the others went in the same way.  Then I only had to put it back in.

At least the new one has more aerodynamic styling …

  That seems sort of simple, in that it’s just a matter of reattaching the relatively rigid air hoses back together, but of course, when I was taking them off they always wanted to screw back in because of the twisting of the plastic hose on the barbed fittings.  So when I started to screw them back in, they wanted to unscrew because I was twisting the hoses the other way.  I ended up spinning them in the direction against the threads for as many turns as I could manage and still keep control of their twisting, then fit them into the correct port on the port pressure release.  This ended up working fine, and the lines all went back together.

  Now, if you’re used to hydraulic brakes, like I was, you might find yourself a bit intimidated by working on air brakes, but it really is much easier.  See, in a hydraulic braking system at this point I’d have to open the line at the brake and pump on the brake pedal and force the fluid (and any air bubbles) out of the ~20 foot line to the back axle in order to make sure that the brakes would work safely.  But in an air brake system, all you have to do is start the engine up, build air pressure, chock the wheels, take off the parking brake, then get out and check around the reconnected lines for an air leak.  As it was, I had none, and with the engine already running, moved the bus forward, hit the brakes and the bus stopped perfectly.

  Yet another bus hurdle was overcome, and while no trip was taken, everything was okay, and I felt a lot more confident in the buses’ brakes.

Starting the walls *or* How to make a big open space less open …

  With the sill plates for all the walls in place and the floor and seat-frames in for the areas aft of the ‘bridge’, I was set to put up walls.  Now, this might seem simple, but keeping things plumb in a off-level in two direction bus with a curved ceiling is a bit tougher than one might think.

  First (and easiest) were the wall studs that were right by the outside of the bus by the window supports, because it was simple to line them up to be plumb.  And the 2×3″ lumber fit just about perfectly with the window supports.  Well, except for the seat-rail that needed to have a cut in the stud to fit up close.  And the  drilling into the studs to allow for the four screws and washer-discs that held the windows in place, though I didn’t really have to deal with those until I thought I knew what I was doing because I started right behind the aft cabin seat on the port side.

My handy Kreg jig and the official screws that go with it …

  This wall is the front wall of the bathroom, and went along one of the skinned windows.  It was a bit trickier to put in because it didn’t run along one of those support ribs, and thus I had to use a framing square to try and keep it plumb while fitting it behind the seat.  But on another note, it was east to secure, as several screws were put straight through it into the inner metal ‘skin’ of the bus, or into the pressure-treated plywood of the inside of the skinned window.  At the bottom, I used a Kreg jig to make pocket holes and then used pan-headed wood screws to the sill I had already attached to the bus floor.

Behold the wonder of the pocket jig.

  And after I had that first stud in, I realized that it was harder to figure out the others.  I ended up using some masonry line to make a straight line across the bus to the other windows so that I could get a straight line for my wall.  While I could run a chalk-line from one end of the bus to the other and mark a midline both on the ceiling and on the floor, you really can’t easily do that on the curved ceiling going from side to side.  And this is actually a big deal trying to do the studs on a 16″ on center standard.

  It’s very easy to measure on the floor, but at the top, I ended up having to use a large and a small framing square to measure out the 14 1/2″ distance from the previous stud, being sure to be perpendicular, and then measuring up to the ceiling both to mark the location and to make a measurement on how much longer the next stud would be.  And then the stud needed to have an extra angle figured in for the slope of the ceiling.

Like this …

  This wall had an added extra issue, in that the inner corner would have been right in the middle of the forward ceiling hatch. As you can see from the picture, I chose to build around it.  That’s because the hatches that they chose to add to our bus included vents that could be adjusted forward or back, and I wanted to be able to not only have these work for the cabin (and potentially the master bedroom) while still providing privacy for people in the bathroom (or in the bunks).

  But this wall was relatively easy.  In order to finish up the back wall for the bathroom, I had to deal with the wheelwell (well, at least the one on the port side, but I’d have to deal with the starboard side eventually…).  On the port side, I ended up integrating the box over the wheelwell into the wall, and then running the rest of the studs up along the galley area.

  On the starboard side, I made a nice box that would have a wall built atop it, and a doorway that would run alongside it. These

Starboard side wheelwell box.
Port side wheelwell box.

were set to be fairly tight with the metal of the wheelwells, and able to be packed with fiberglass insulation to negate road noise and provide a thermal barrier as could be managed.  You might note the crossmember over the blue painter’s tape that’s on the wheelwells – that’s the sill of yet another wall on either side of the main walkway.

Like the bathroom.
For the tops of studs.

 But the farther I went along, the easier the process got, until I had a nice forest of studs dividing the space up into phantom rooms and doorways.  One of the only real problems with these was that some of the 2×3″ boards had twists or warps, and these could make it hard to keep the walls in line. Another was that the screws at the top of the studs had to go into either the metal skin or the structural support ribs of the bus body itself.  I used a whole lot of these Teks screws, and they were ‘self -tapping’, and for the metal skin of the ceiling, they were.  However, when you needed to screw into one of the structural ribs, they just wouldn’t make it.  I ended up having to pre-drill holes for these screws, which meant lining up the stud that already had the pocket jig’s holes in them, and keeping them from drifting while I fitted the small drill in the pocket jig holes and drilled into the metal.  Not surprisingly, they wanted to slide all over the place, rather than drill a hole, and this took some practice and a bunch of drill bits.

  But eventually, I got that all done, and the space was divided, and began to look like this:

Looking from the master bedroom toward the front.
Lots of walls one could walk through …

  It just doesn’t look the same as that big empty room, though it did start to give a feel for how tight or spacious a part of the bus was going to be. It certainly makes a difference to have the 3D feel of the plan.  Tape outlines on the floor look fine against your feet, but the studs really make the space feel delimited. 200 square feet can feel really small sometimes …