Dot & Georges .

[Dot]

The "professional" mob that that pic came from is the mob that screwed us some yrs ago. They are in Qld as are most shonks looking to make a quick buck. Shall pass that info on to the Gman. ta boys.

[supersparky]

Dirk, Are you saying that it is better to deflect air down from the top of the bus to the ground or up from the ground towards the top then away?? I have been considering modifying a wind deflector similar to the old Falcon or Commodore Station Wagons to try and keep the back window clean. That's a bad choice of words, perhaps I should have said to allow rear vision visibility when it is raining or when driving on wet roads. I know a picture is worth a thousand words but unfortunately I don't have one to describe what I have in mind. Maybe you do?

[T1 Terry]

A wind deflector shaped around the sides of the bus at around window level work quite well for keeping the rear window clean, I think it was the VC Valiant station wagon that first came up with that idea, but it may have been even earlier in the XK and XM falcon station wagon here is pic I found on the web that sort of gives the idea of what I mean

[Dot]

how many of those in line blower thingos do you reckon would do the trick Mr T?

[T1 Terry]

Two, one blowing out each side, fit a stainless plate to act as a heat shield set away from the eng compartment roof and have the fans sucking the air out of this cavity between the heat shield and the floor of the under bed.
The alternative is two fans but drawing air in from each side and blowing it up and under the bed base (engine compartment roof) so the hot air is forced out the bottom cooling the engine parts on the way. This method could be on a separate switch for the times you want a warm bed, or left on for an extended run time after you stop to ensure the bed base is cooled. If you go the route of drawing air in from the sides, use small scoops to direct the air into the 4"pipe and blower but fit fly screen wire across the opening to keep leaves and bugs out.

T1 Terry

[BruceS]

Dot I've got 2 of those blowers sitting on the boat. I reckon you should look at how much they blow before you spend money on them.
The 'problem' you have is half a tonne of cast iron and water that is up around 175-180 degrees F and regardless of what you use it will take half an hour to dissipate that much heat.
I think an extra layer of insulation and then pull up half an hour earlier and pop the engine bay door open. Try to park with wind blowing up your backside. (opposite to Chuck)
Cab over truckies have been fighting this problem since year dot........

[Dot]

Reckon the first port of call is the insulation place for sure. At Christmas when we went to Melb we pulled up at 1pm as it was too hot to travel 1/ the sun coming in the big windscreen and 2/ the heat from the motor coming through the back walls around the motor which was heating the back end of the bus up a lot. When we stopped we opened the engine panel to let it get more air over it but the outside air was just about as hot as the motor Going to Adelaide this week to check out the insulation stuff. Did you know you can die from having wind blown up your backend! so Chuck isn't as silly as we first thought

[jon_d]

Insulation can only slow the heat transfer.

So, you need to have enough of it so that the transfer is so slow that the engine is cold before the heat gets though.

eg; If it takes 1hr for the heat to transfer though the insulation, then if you drive 1 hour, then, the heat is already getting into the cabin.

[T1 Terry]

It is a common problem with rear engine buses, the insulation will delay the time it takes for the heat to soak through, but it will still soak through given enough time.
The heat shield method will produce an air pocket between the heat source and the area you wish to shield from the heat. By changing the air regularly you move the heat away from the area so it can not transfer to the next level which in this case is the under floor. The only better method would be a water jacket made from that thin tubing they use for pool heaters that they string up over the house roof. Water can move 3 times the heat energy that air can so the water moving through the tubes carries the heat to a radiator core where it can be dumped into the moving air stream created by the fan.
A mix of the two methods, water spray into the air stream will remove quite a bit of heat as well, this is how an evaporative air cooler works and why they put water spray nozzles on the intercoolers of race engines and big diesel engines that are working hard.
I see Jon has posted while I typed this out, had to take the dog for the trip around the block in the middle of typing as well

[Kelvin12]

G'Day David,

Terry's photo is what I have in mind. The reverse of rear end spoiler, instead of down force to improve traction the reverse spoiler directs air down. It re-directs clean air down into vacuum created at the rear of the square ended vehicle. The air flow fills in vacuum stopping the crap sticking. Especially necessary with buses in particular. There is another system apparently popular with the American truckies and looks like numerous fish tails in reverse where several of these reverse fish tails channel the air from the sides into the funnel shape which fills the vacuum behind. More of an air flow / fuel saver thing than a clean behind. They look bloody terrible though.

Dirk