The Broccoli Bus

[aaronsb]

The rear engine on this thing looks like zero consideration was made for ram air cooling. The radiator is sideways and simply sucks in from the outside of the bus. It's hydraulically driven at least, so when the fan motor explodes your power steering will probably go too.

Originally Posted by jazty

Fun fact for some (all?) of you who own a front-engine bus on an International chassis and possibly others:
Have you noticed where the air intake is on the hood/cowling? It's right below the front windshield with the opening facing the windshield. Why? Because the windshield creates a high pressure area which helps push air into the engine! Or so I've read, anyhow.
Now that's clever use of poor aerodynamics...

[thjakits]

Jazty,
.....the Broccoli Bus is a RE-bus.

By the time air hits the rear of the bus it doesn't matter what you do to the front end....
[...unless something happened since the pics on page 1 ]

thjakits

[aaronsb]

Here is a photo of the team working on the bus, from right to left.

Chris, Cory, me, Nick, and Ava.

Cory is my riveting expert, Nick and Chris work at my shop rebuilding unimogs. They are good at everything.

Ava is my oldest daughter and she cleans up and brings us cold drinks.

Sam is the dog. He just wants to be loved a lot.

[thjakits]

Man!

YOU ARE SET!!

thjakits

[jazty]

Originally Posted by thjakits

Jazty,
.....the Broccoli Bus is a RE-bus.

By the time air hits the rear of the bus it doesn't matter what you do to the front end....
[...unless something happened since the pics on page 1 ]

thjakits

Yes, I was and am very aware of that. With the talk of air-dams and the effect of aerodynamics on the air passing through the radiator I just thought it might be an interesting tidbit of info.

[aaronsb]

Getting a lot of the rivets complete.

All the hard parts are done, now its just a lot of the straight spars which go fast.

I'd estimate about 60 percent of the rivets are placed.

[aaronsb]

The re bus really has about the same aerodynamics as a standby generator bolted to a pad I think.

Photo of the side access to the radiator and the way its mounted in the engine bay.

Bottom of the bay is just open.

Originally Posted by jazty

Yes, I was and am very aware of that. With the talk of air-dams and the effect of aerodynamics on the air passing through the radiator I just thought it might be an interesting tidbit of info.

[Malkieri]

I've always wondered if a scoop or something would push more air in through those. I am sure the engineers made the appropriate compromises in function and what-not, but I just don't see how that is the most efficient and effective method for cooling a rear-engine. Maybe some graduated louvers would be better than a single scoop. That would leave the full screen open but provide some ram air on movement... What do y'all think? Maybe someone can grab a set off an old Saab or Camaro or something from a boneyard and run some tests? You know the ones that look like this:

[thjakits]

Jazty, ...sorry! I was readying way to fast and missed the details in your original post!!

You won't believe it, but many manufacturers lack some serious aerodynamic knowledge and/or just approach things with a "a bigger fan will solve that" attitude.
Aerodynamic R&D often is not done in house but contracted out...

There are two old books out there (from and before WW2, FLUID DYNAMIC LIFT and FLUID DYNAMIC DRAG by Hoerner)
[In case you wonder - a lot of performance was to be gained by streamlining the huge cooling needs of the aircraft engines - what applies to them applies to road vehicles just the same, at somewhat lower performance scale]

There is a LOT of formulas and drawings in there - ...just looking at the drawings and analyzing the comparisons you could solve a LOT of the cooling problems and even improve on efficiency!

Have a closer look: Most fan arrangements do NOT seal to the front of the radiator - a big deal of forced airflow escapes to the sides before going through the radiator.
A lot of time, there is not enough space behind the radiator for the air to escape freely!

I bet instead of huge louvers are small line of vortex-trips in front of the intake and possibly a small lip at the rear could change the pressure in front of the radiator dramatically....

thjakits

AS mentioned the floor is open in the engine room, maybe even to the rear, but what about UP??

Hot air loves to rise!! WHY force it any other way??

You don't want huge louvers on the side - you will not always drive at full speed - what about trundling along a mountain road or in traffic and having a strong tailwind - effective ram-air could become ZERO in a heartbeat.

Some experimenting along the lines published in autospeed.com can show you fairly quickly where the different pressure areas on your bus are.
After that it would be fairly easy to start to work in the right direction......

[aaronsb]

I think that the way it's set up right now (rear engine, side mount radiator) is probably adequate, simply because the fan is driven all the time by a hydrostat motor. The size of the fan, and the size of the fan motor lead me to believe that thing can start blowing like prop driven airplane if it needs to. Since the inlet is small and the exhaust opening is large (the entire engine bay is open) it makes sense to exit the hot air out the bottom of the bus.

Some other thoughts: nearly every rear engine bus arrangement I see has the radiator with no real provision for passive at speed cooling. There's probably a reason for that - the coolant lines are huge, and multiple 2 - 3" water lines the length of the bus would put a lot of weight on there, as well as additional failure points along the mounting of the lines, and requiring a substantial increase in the size of the water pump to push the head of water up a hill and just drag from resistance of the water lines.

In conclusion, I think the drawbacks of using passive cooling with the vehicle moving through the air at speed I think are considerable when faced with the mechanical reality of moving the coolant from the front to the back of a 40' long vehicle.

Originally Posted by thjakits

Jazty, ...sorry! I was readying way to fast and missed the details in your original post!!

You won't believe it, but many manufacturers lack some serious aerodynamic knowledge and/or just approach things with a "a bigger fan will solve that" attitude.
Aerodynamic R&D often is not done in house but contracted out...

There are two old books out there (from and before WW2, FLUID DYNAMIC LIFT and FLUID DYNAMIC DRAG by Hoerner)
[In case you wonder - a lot of performance was to be gained by streamlining the huge cooling needs of the aircraft engines - what applies to them applies to road vehicles just the same, at somewhat lower performance scale]

There is a LOT of formulas and drawings in there - ...just looking at the drawings and analyzing the comparisons you could solve a LOT of the cooling problems and even improve on efficiency!

Have a closer look: Most fan arrangements do NOT seal to the front of the radiator - a big deal of forced airflow escapes to the sides before going through the radiator.
A lot of time, there is not enough space behind the radiator for the air to escape freely!

I bet instead of huge louvers are small line of vortex-trips in front of the intake and possibly a small lip at the rear could change the pressure in front of the radiator dramatically....

thjakits

AS mentioned the floor is open in the engine room, maybe even to the rear, but what about UP??

Hot air loves to rise!! WHY force it any other way??

You don't want huge louvers on the side - you will not always drive at full speed - what about trundling along a mountain road or in traffic and having a strong tailwind - effective ram-air could become ZERO in a heartbeat.

Some experimenting along the lines published in autospeed.com can show you fairly quickly where the different pressure areas on your bus are.
After that it would be fairly easy to start to work in the right direction......

[aaronsb]

Also, if it's interesting - I'm planning on installing a split AC system with the condenser mounted inside the other barn door in the engine bay on the right side of the bus. It's air will be drawn in from outside and blown downwards as well. Left side is engine cooling, right side is passenger cooling. Just for laughs, I am considering an air-water intercooler as well, which would necessitate a third radiator. That one would probably be transversely mounted, or stacked behind the air conditioning condenser.

[Dragonpop]

I was under the impression that all the C8.3 engines had a charge air cooler like mine which is mounted in front of the radiator where the fan can do it's thing.
I have seen where they also have an intercooler that mounts on top of the intake manifold which uses radiator water for cooling. What is the horsepower level
of your C8.3, mine is rated at 300hp and has the Air Filter mounted vertically instead of horizontal as yours seems to be. I was amazed at the speed of your
conversion process thinking your were some kind of superman but your post with the crew picture dispelled that idea. I'll try to make contact with you as soon
as I get some breathing room around here. Do you have plans of installing a tow hitch on your bus and any thoughts on fabricating hitch's for other skoolies as
well. My All American has a different Frame setup in the engine compartment than yours. Keep up the good work!

[Tango]

Quick side note & fun facts on airflow --- many vehicles that rely on flow through cooling are designed with a small inlet and large exhaust for good reason. The air passing through slows down where the cooling takes place. Many high performance internal combustion aircraft have to have what is called a "still air box" built around the cylinders to slow down the airflow enough that it effectively carries away heat. If the air passes over the cylinders too quickly it cannot remove any heat. We copied the idea and applied it (successfully) to some of the air cooled formula two-stroke racing bikes friends and I raced many moons ago.

Take a look at the design for the 'NACA Scoop". The sole purpose of that design is to slow down and depressurize (which also cools) the air that enters.

[aaronsb]

I'm pretty sure there's no charge air cooler on this engine. It seems to exit the turbine, loop around the engine, and enter into the intake manifold. Here's a photo where you can see the cast aluminum manifold going around. I haven't really put my hand on the whole length of it - it's possible there is a cooler hidden in that casting and I just haven't seen the engine coolant connections.



When I get a chance, I'll get a photo of the engine tag. It might just be an 8.3 CT and not CTA.

I have recruited a little bit of assistance here and there (for instance, I asked nicely and my neighbor graciously came over with his two boys to help turn the jack bolts all at the same time to lift the bus roof), but really started asking for some assistance when I had to hang the new sheet metal on the bus. I am not superman, but I also think it's not all together that difficult to do.

Yes I'd like to add a tow hitch. I think I'll use the hard points in the rear where the big tow hooks are currently. I'll have to come up with something that still allows the big hooks to function as intended.

I'm also considering a cattle catcher of some kind in the front to replace the stock bumper. On ours someone caught the drivers side front bumper and bent it. They bent it back but it's still not right. A few good evenings with a plasma cutter and some plate should yield a great bumper I can bolt back on.

I don't want to advertise directly, but I own a local company in the Seattle area that specializes in expedition vehicles. If there is anyone that needs help or would like some formal assistance with fabrication or assembly, PM me and I can fill you in on the details.

Originally Posted by Dragonpop

I was under the impression that all the C8.3 engines had a charge air cooler like mine which is mounted in front of the radiator where the fan can do it's thing.
I have seen where they also have an intercooler that mounts on top of the intake manifold which uses radiator water for cooling. What is the horsepower level
of your C8.3, mine is rated at 300hp and has the Air Filter mounted vertically instead of horizontal as yours seems to be. I was amazed at the speed of your
conversion process thinking your were some kind of superman but your post with the crew picture dispelled that idea. I'll try to make contact with you as soon
as I get some breathing room around here. Do you have plans of installing a tow hitch on your bus and any thoughts on fabricating hitch's for other skoolies as
well. My All American has a different Frame setup in the engine compartment than yours. Keep up the good work!

[aaronsb]

Yep, I was going to mention the NACA scoop, but then I started thinking "hey, it's a bus - I'm lucky to travel 65 mph down the highway"

I believe the reason the naca scoop is effective is it allows air to be drawn into a low pressure region from a high pressure region without a lot of disturbance on the skin of the vehicle. Additionally, it's easy to control the amount of flow, so you can get that "still air" into the passenger compartment or engine compartment (or whatever else you're trying to get the working gas medium into)

To add onto the mention of the still air box, just to get people's brains turning:

In many applications the still air box (and sometimes naca scoops) are used in the air combustion intake to assist with tuning for a particular helmholtz resonance frequency in the intake plenum. With a widely varying intake pressure, you affect the median resonance frequency, and thus affect the performance envelope of the engine intake with a mismatch between piston RPM at maximum torque and intake pulse frequency.

Yes, the engine intake becomes a giant beer bottle that you're blowing air over the lip with, and yes, those pulses aid in passively charging the intakes with more air per cylinder stroke.

None of that is really as important when you start to use a charge air system such as a supercharger or turbocharger, however.

I think the big open engine bay where the cooling fan draws in the side and out the bottom is actually a good design. It keeps things dry and slightly pressurizes the compartment so dust and dirt don't get as much as a chance to take up residence.

Originally Posted by Tango

Quick side note & fun facts on airflow --- many vehicles that rely on flow through cooling are designed with a small inlet and large exhaust for good reason. The air passing through slows down where the cooling takes place. Many high performance internal combustion aircraft have to have what is called a "still air box" built around the cylinders to slow down the airflow enough that it effectively carries away heat. If the air passes over the cylinders too quickly it cannot remove any heat. We copied the idea and applied it (successfully) to some of the air cooled formula two-stroke racing bikes friends and I raced many moons ago.

Take a look at the design for the 'NACA Scoop". The sole purpose of that design is to slow down and depressurize (which also cools) the air that enters.

[bansil]

HEY!!!

all of ya'll sitting here talkin' all this big engine shiat....just gotta STOP!!! period...8.3 this 8.3 that

(notice all the I just bought a new corvette envy in that responce?)

.
.
.
anyways...when you gonna bring that big bad boy.....this way?....I will throw you a 20 amp cord and a field

[aaronsb]

I'm working on it as fast as my budget, body, and wife & children can tolerate. I'm hoping to have all the rivets done in about another week and a half, time permitting.

I think this list will take me through december:

vinyl and ply floor demo
steel floor repairs
interior paint
exterior paint
convert door to swing outwards pneumatic door
running lights
vehicle electrical (stuff to make it legal and safe to drive down the road, such as powering the running lights)
new tires
engine bay cleaning
engine fluid change
engine brackets and stuff to repair a few leaks
fix a few dodgy wiring bits and linkages
remove weird crossing mirrors
clean up remaining pneumatic stuff from sign and crossing guard removal
interior insulation panels install
conduit for wiring in living space
hvac cold air duct down center of ceiling
horizontal wooden running boards for thermal break
spray in foam flush to running boards
new subfloor on top of foam and running boards
fix dents and bends in luggage bay
remove and replace luggage bay plywood

Originally Posted by bansil

HEY!!!

all of ya'll sitting here talkin' all this big engine shiat....just gotta STOP!!! period...8.3 this 8.3 that

(notice all the I just bought a new corvette envy in that responce?)

.
.
.
anyways...when you gonna bring that big bad boy.....this way?....I will throw you a 20 amp cord and a field

[thjakits]

Hi all - again,....

Aviation piston engine compartments - be careful what you copy! Until the advent of Experimental Aviation (google EAA) there was a lot of pseudo-science and witchcraft at work (mainly on small airplanes - the big guys had this pretty well sorted!)! Sometimes derived from improper design, battling failures that were not visible on the ground, like rubber cooling seals of big enough plenums lifting off their seats in the air - still hot cylinders are the result and and even bigger intake followed! Another big mistake was (...and sometimes still is!) not to clean up casting flash on the cooling fins! ...another one: not install the proper cooling air guides around the fins - air will not flow through the fins if it easier to flow around them....

Still-air box: IF there is airflow over the cooling ribs - it will cool, no matter how fast the air goes.
However if you slow the air down and let it heat up a bit more, you will need less air-mass - less air means less drag - so the real reason for the slowing down is increase of efficiency and reduction of overall drag.

And yes, that can be DIRECTLY applied to buses! You will have to build proper plenums (diffusor and accelerator boxes) though and you need to be careful to stay on the safe side of certain angles. IF you go that way though you will safe some serious fuel by not having to run the fan all the time....- especially with hydraulic drive fans - hydraulics are not exactly the most efficient way to drive fan.....)

For anything CARS or BUSES - stay away from the NACA ducts!! If you think so, they may look cool, but unless you REALLY know them, they will do you no good!
There are aftermarket NACA ducts out there to plaster into/onto your ride, but so far I did not see a SINGLE one that is properly made.

If you must know the very details I can forward a pdf with the details about NACA ducts to anyone who cares (...or you can google it up)
These ducts where a development by NACA to enhance overall aerodynamics - an effort to find a way to intake air in a better way than hanging a scoop into the airstream. NACA-ducts are very difficult to place correctly and make them work. As you never streamline a car/truck/bus into the wind (...you better keep following the ROAD!) - most of the time even a properly built NACA duct will not work on a road vehicle...

'nough said!

off the box

thjakits

[Stu & Filo. T]

Originally Posted by bansil

HEY!!!


anyways...when you gonna bring that big bad boy.....this way?....I will throw you a 20 amp cord and a field

Are Tennessee cops still pull over out of statere's & stealing all their cash?

[bansil]

Originally Posted by allwthrrider

Are Tennessee cops still pull over out of statere's & stealing all their cash?

just the highway JBT's (thats Jack Booted Thugs for the miss informed...still not sure? google Stalin and and Hitler )

your cool stick to the byways and let me know...I'll grab an ole firebird and run interference for you......