Category Archives: School Bus

At The Terminal – Snow & an Accident (not mine!)

So, more lessons from being a real school bus driver, not just a skoolie.

I have to start with a news story from last Thursday (December 11), where a school bus driver slid the back of his bus into the open door of a parked car, catching a pregnant woman’s arm as the door was forced closed  (and another report).  The weather was snowy, with rain that had turned to snow overnight.

Bus Accident 12/11/14  The video from the surveillance camera (in the first link) really nicely shows what happened.  It’s obvious that the driver had the bus in drive and the wheels spun as the bus tried to get going, but then they caught, and then spun again, causing the bus to slide into the woman’s car and catching her arm.  Now, for people who are used to gasoline powered cars, it must look like the driver stepped down hard on the pedal, let off, then stepped down hard again, but that’s not likely to be the case.  The diesel engines in these buses are slow to ramp up.  Yes, you can step down hard on the pedal, and the bus will go, but it’s not as reactive as a gas engine.

    You might also ask if the street is slanted.  I used to drive the route and the driver is only on that street for one block (unless they’ve changed something serious since October), and the street is nice and flat.  Why then would the bus slide like that?  Well, for one thing, it was empty (the driver is out of my terminal, and I heard the report on the radio), he being almost an hour late due to the weather and not having had his first stop’s student on the bus (otherwise, as you can see in the video, he wouldn’t be able to get off the bus).

Now, you might not think that the kids on the bus weigh alot, but the buses that size can now carry 58 students (they were standard 65 student buses, but the upgraded seats that all have three-point harnesses cut that down), and we carry all the spectrum from pre-kindergarten to eighth grade students.  If you figure a simple 85 pounds per student, you’re looking at just about  two and a half tons of kids in the buses weight.  This makes a huge difference not only in acceleration and braking speeds and distances, but also in handling, as these buses are rear-wheel drive, front-engine buses.

As it was for my run on that day, I ended up getting to my school fifteen minutes late, and spent most of my run 10 minutes late, but not because I felt the roads were so slippery.  Coming out of our yard and heading to the start point of my route (in my empty bus), I noted the slippery aspect of the roads, and dropped my gearing from drive (which worked fine in the gravel of the bus lot) down to second, due to the thin film of slippery slushy snow under all the fluffy snow of the five or six inches that were on the roads.

One of the things this did was limit my buses’ top speed down to 25 miles per hour (which isn’t a big deal since the speed limit in the city is 30 mph), but also kept the bus from shifting down as quickly.  This made it easier to get and keep traction.  I also started braking a little earlier, since people stomping on the brakes to stop suddenly and then stomping on the gas to get going at intersections makes them extra slippery.  But here’s a place where driving the bus actually helps – your drive and dual braking tires are in the back, farther behind where cars tend to make slippery.  So I actually found the driving to be fine.  No slips, no slides, no being out of control.  And the more students I picked up, the better it got, as I got more weight over my drive wheels in the back.

My lateness was due to accidents that I had to pass and other drivers who were not driving safely.  And while I understand that not everyone is as comfortable in winter driving as I am, everyone should be as aware of how to drive  in these weather conditions, just in case.

It also makes me much more comfortable with the prospect of driving the skoolie through inclement weather.  Due to the built in nature of the furniture and appliances (and the water tank, when that goes in), there should be plenty of stable weight to maintain control.  Plus, manual transmissions help out a lot in situations like this.  If I could go back to Thursday and change my bus from an automatic to a standard, I probably would have had an even more enjoyable day, driving-in-that-weather-wise (but probably not for the amount of stop-signs on my route!).

But the bus accident above was another really good reminder of how a driver has to be really careful all the time.  As much as the street the driver was on was a one-way street, he should never have been that close to that car anyhow.  The video certainly makes it look like he could have been another foot or more over toward the right side of the street.  Does that accident come down to poor judgement and the bad luck to hit an extra-slippery bit of street?  Probably.  But that sort of thing scares me silly, so I try to drive carefully.

As we all should.

Electrics (Part II)

(Continued from Electrics (Part I))

The next step was the batteries. Of course, the bus already had two big batteries wired up to start the bus, so you might ask why we’d need other batteries. The answer is that there are two types of batteries that you’d find in an RV (or maybe even your car), and they each do different jobs.

The batteries already in the bus, and the ones in regular cars, are primarily meant to start the car and store up excess power from the alternator. That is, they are meant to have a high/hard draw of electricity in relatively short bursts. Often these will have ratings of ‘cranking’ amps or ‘cold cranking’ amps to show how much ‘power’ they have compared to other such batteries. Bigger batteries have more ‘cranking’ amps, meaning that they can provide more power to the starter. The bus’ two batteries have a total of 1880 ‘cranking’ amps and 1500 ‘cold cranking amps’. (For a comparison, my pick-up truck has 825 ‘cranking’ amps and 690 ‘cold cranking’ amps.)

 

The type of batteries that I added were ‘deep cycle’ batteries, which are meant to be slowly discharged of more power than the regular auto batteries are.  Thee are rated in ‘amp hours’ which tell you how long they will hold up giving power dependent on how much draw you put on them.

You might be wondering how you would know if you have a battery with enough ‘amp hours’ for your system.  There are a number of different on-line calculators (here’s one from http://www.batterysizingcalculator.com/ ) to make sure you get what you need.  Many RV systems are set up for only 20-24 hours of battery usage, assuming that you’ll be running your generator, plugging into shore power, or be using your vehicle’s alternator to recharge your batteries by then so you don’t overdraw your system.  A system that draws 30-40% of your battery’s ‘amp hours’ in 24 hours will totally drain your batteries in three days of use!  (A great resource on understanding all this is in “RV ELECTRICAL SYSTEMS-A Basic Guide to Troubleshooting, Repair and Improvement” by Bill and Jan Moeller, 1994, Ragged Mountain Press, Camden, ME  which is a little outdated on some of the appliances available but the theories and math are really sound.)

Anyhow, I worked out our system for four days of off-grid usage, estimating for a bunch of appliances and hour-usages, and came up with about 480 amp-hours at 12 volts that we needed.  There are a number of ways to get that.  Some people use a number of smaller voltage batteries (6 volt golf cart batteries are favorites) that can be wired in series to give the 12 volt systems, or several 12 volt batteries wired parallel to give the amp-hours needed, or combinations of series and parallel connections of lower voltage batteries to give the right voltage/amp-hour combinations.  The trick in all these is to use the same type/capacity batteries throughout the system, or the batteries could be damaged through uneven power draw or charging.

Another consideration was which type of battery to choose.  Most car batteries are flooded or wet-cell, which can be ‘sealed’/’maintenance free’ or  ‘serviceable’; the ‘serviceable’ ones being the ones you have to top up with distilled water and have to be sure to give adequate venting to let off the (potentially explosive) hydrogen gas and the sulfuric fumes that can come from charging, while the ‘sealed’ ones have the ‘eye’ that give you a color if everything’s okay, but can still vent gasses while charging.  These have to be mounted upright (or they could spill), and need to be mounted outside of the ‘liviing’ area of the vehicle (or be really well vented in a non-reactive compartment).

Additionally, there are AGM (Absorbed Glass Matt) and Gel-Cell are different in that the electrolyte isn’t simply in a liquid, but rather in a gel held between the plates in the battery, with the Gel-Cell actually being more of a rigid gel with a higher silica content.  These can be mounted in any direction and only off gas is badly overcharged (or with the wrong charger in the case of Gel-Cells), so these can be mounted in a passenger compartment without special ventilation.  The AGMs are considered one of the best at holding charges, and the Gel-Cells are considered very deep cycle (with a very slow recharge time) and have better durability in hot weather.  (Nice info summary and more info here at http://www.batterystuff.com.)

I ended up going with two Lifeline GPL-8DL batteries, each 12 volts with 255 amp-hours, so that when run in parallel we would end up with 510 amp-hours.  These are, however, pretty sizable batteries, each weighing 162 lbs, and being 20″ x 11″ x 9 3/4″ in size.   As big as this is, though, the two of them fit just fine under the rear-facing bench seat behind the captain’s chair, which serves to keep the length of 2-0 line running from them to the convertor (and later to the inverter and solar controller) to a minimum.

To be safe, I wanted to put a fuse in the system, and found a 500 amp surge/125 amp continuous fuse, with a little 15 amp bypass fuse that  would keep small systems running after the big fuse burned out.  In addition, the big fuse could be unscrewed to limit the danger to the batteries themselves.  When you are working with so many amps, even at a seemingly harmless 12 volts, it can be dangerous.

Now, I needed to put in some appliances! (Or at least one …)

Continued in Electrics (Part III)

Electrics (Part I)

After the air system was in, and I knew the locations of the air lines and accouterments, I could run the electrical lines.  A good friend of ours had let us salvage parts from a 1970’s vintage RV trailer, and from that I was able to get some electrical components,   the two important ones for this were the 10 gauge 25′ power cord and the 30 amp circuit breaker box.  The box had a 30 amp main switch, and three additional 20 amp breakers.  The only odd thing was that the 30 amp plug

A 30 Amp plug

on the end of the power cord had been replaced with a 15/20 amp plug meaning that the power coming into the bus was limited to 20 amps (so far).

15/20 Amp plug

One of the critical things that I learned on our Sprague Brook trip is that getting the power inside the bus proper is very important.  And having a roll of 25′ of three-ply 10 gauge stranded wire to connect to a power outlet outside the bus is no small thing to mount in a secure location.

I decided that the wire would coil in the empty area of the battery box on the port side of the bus, and thus would have to come up through the floor just by the heater box inside the bus compartment (right by the captain’s chair).  As with the soft air line, this needed to be protected from the sharp edge of the metal floor, where the vibration and movement of the floor while the bus is in motion could cut the insulation and wires, producing a dangerous short or a ‘hot skin’ condition of the bus, which is where the metal skin and frame carry the 120 volt AC current, and anyone touching it completes the circuit (Zap!).

I wanted to keep the 10 gauge wire, though, as the smaller the gauge, the less electrical energy is lost getting from the plug to the outlet, and it turned out that the ~1/2″ cable fit just inside a 3/4″ compression connector (for an electrical box to connect to a rigid chase pipe) that I had acquired as a “bit”.  once I had double checked that the hole I was going to drill would come out in the battery box, I slid the compression connector down into the hole and screwed it down tight (leaving the unneeded compression fitting off), and it produced a perfect safety barrier against the sheet metal flooring.

Looking into the battery box, the connector is on the top and the cable coming down through the floor.
Looking into the battery box, the connector is on the top and the cable coming down through the floor.

After the connector was fitted, I ran the wire through it, attached a new 15/20 amp plug, and then set up the breaker box.  I decided to put it just behind the captain’s chair, as it wouldn’t be of any use while the bus was in motion, and was conveniently located by the battery box and the seat where I would be storing the house batteries.

The breaker box in place in the frame of the wall between the captain's chair and the rear-facing bench seat in the passenger area.
The breaker box in place in the frame of the wall between the captain’s chair and the rear-facing bench seat in the passenger area.

The box has a 30 amp main, and three 20 amp feed breakers.  I attached the power cable to the main, and ran one of the 20 amp breakers to outlets behind the captain’s chair and another in the ‘closet’ area behind the wet-wall for the bathroom.

The specs on the power converter.
The specs on the power converter.

Another of the breakers was dedicated to a Magnatek Model 3240 power converter.  This is a unit that takes 120 volt AC  input and converts it to 12 volt DC current.  it can be hooked up to 12 volt batteries and has an automatic switch to detect the AC power, and switch to battery power when the AC is disconnected, and vice versa, without cutting power to the attached 12 volt appliances.

The power converter in place behind the rear-facing bench seat, attached and double-grounded against the wall.
The power converter in place behind the rear-facing bench seat, attached and double-grounded against the wall.

I had picked this up when I got our fridge (a forthcoming post) and the guy threw it in for a very small amount, which on the one hand is great, since we needed something like this, and on the other hand is annoying, since it was an ‘as is’ purchase and it turned out the battery charging element wasn’t working.    At any rate, the converter is a simple affair, using regular automotive ‘knife-style’ fuses, and having both filtered and unfiltered DC outputs (filtered is for sensitive electronics, like the radio).  One of these I set up to go to the radio/tape deck, so that the clock would stay running and I could listen to music while the bus wasn’t on, and another I would run off to the DC connection for the fridge.  Others would be for lighting and appliances like the water pump and water heater, but those will come later and be run through a DC breaker box which isn’t in place yet.

More on this in Electrics (Part II)