BusBuilding

Back when some of us worked on automobiles, we thought nothing of crawling under the car to change the oil or fix a muffler or just bang on a whazzit to get it working.

The number one safety rule is never, never, never crawl under a bus without the framework being firmly supported. Unlike an automobile, almost all buses depend on an air suspension system to stay “afloat.”

Here’s what can happen. Except for some assemblies which are directly connected to the wheels and axles, the entire bus floats on 10 or more highly pressurized ‘air-springs’ at all times when the bus is running and for some time even when it’s not.

You may have seen buses at rest that almost seem like ‘lowriders’; that doesn’t mean they have been modified, it only means that over time, the air supporting the bus structure has equalized with the atmosphere, as will happen with all of them. Over time, through hundreds of connections, air escapes. It may take weeks or longer for a well-maintaned bus to leak down, or it may take less than a day for one that needs attention to the air system.

What can be unpleasant to yo bones is when they leak down suddenly!

It is not common for something in the air system to just go POP, but it can happen. Air systems have numbers of safeguards in place for maximum safety, but no one who knows what they are doing would suggest that you just crawl under a bus. You can accidentally graze an automatic leveling valve and cause the bus to shift in a matter of seconds. Or that component you’ve been planning to replace finally decides to give it up.

And you don’t even have to crawl under it to be at risk. It’s very tempting to stick your head inside a wheelwell between the tire and the bus body to take a look at an inner wheel part, but if you’ll notice, (don’t try this at home) your head just barely fits in that space. IF there were a sudden air dislocation, your head goes POP, because what was about seven inches can narrow to two in an instant. And instant end of bus converter.

Same of course is true if you were actually under the bus. There’s just barely enough room for your head or torso under the transmission, engine or framework when the bus is fully aired up. If it suddenly comes down, you don’t want any body parts in the way. It could and has happened.

As Mark said, in a recent thread,

It is very difficult to breathe with 40,000 pounds dropped on your chest.

Now concerning exactly what materials to use to block the bus structure, you have some options.

Some people use 4×12 and 6×12 pressure treated beams combined with 2×6x10 and 2×8x10 blocks of pressure treated pine boards.

Others say that pressure treated lumber holds a lot of moisture and tends to flatten out under a heavy weight, (you do know we are talking heavy weight, right? and that good oak cribbing is the material of choice.

Still others swear by new, quality railroad ties for cribbing. The hard word obviously can handle the weight.

It’s also important to have some backup blocks in place, but most important is to never work under a bus alone. IF it begins to lower, your helper can insure that a secondary system is deployed, allowing you time to escape.

One of the fellows passed along this worthwhile guide from Canada’s Thompson Rivers University which covers many aspects of the Use of Blocking and Jack Stands.

An excerpt:

Wooden Blocking

1. Wooden blocking shall be made from Douglas fir species of a suitable size to ensure strength (min. nominal dimensions 4″ x 4″). Certain hardwood species may also be used if suitable (i.e. oak).
2. Softwood species such as pine, spruce or cedar shall not be used. None of the hardwood species which occur naturally in BC are suitable for use as blocking.
3. Wooden blocking shall be free from rounded edges, visible rot, cracks, checks or splits.
4. Oil soaked wooden blocking shall be inspected for suitability prior to use.

There’s also always discussion about this topic on the BNO Forum and the Bus Conversions Magazine Forums.

Be safe!

This entry was posted on Friday, March 31st, 2006 at 6:16 am and is filed under Bus Conversion, Safety. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.