Radiator fan consumes over 10% of engine HP!

[Len Silva]

One of the reasons that Eagles have fewer cooling problems as well as better fuel economy, is that they have a slight taper at the rear 10 feet or so of the body.  I think it comes in about 3/4" on each side.  A friend who was an engineer with Eagle back in the day, told me that they did extensive wind tunnel tests and came up with that design.

[Jeremy]

One of the reasons that Eagles have fewer cooling problems as well as better fuel economy, is that they have a slight taper at the rear 10 feet or so of the body.  I think it comes in about 3/4" on each side.  A friend who was an engineer with Eagle back in the day, told me that they did extensive wind tunnel tests and came up with that design.

Buses and trucks with curved rooflines are a common sight here now - I've no doubt there are genuine fuel savings to be had






Jeremy

[Len Silva]

It wasn't the roofline but rather the sides that were tapered.  The Eagle bus is about 1-1/2" narrower at the back than at the front.

[bevans6]

Both ideas create more laminar air flow, which is less draggy than turbulent air flow.

Brian

[Jeremy]

Bus design has gone backwards ever since Alfa Romeo perfected it in the 1930s:



And you've got to wonder whether GM hadn't solved both aerodynamics and cooling in the 1940(?)s:




Jeremy

[luvrbus]

That is not a GM that bus is a Flx with the top scoop and they ran hot with their straight 8 Buick engine  

good luck

[Ed Hackenbruch]

I like the Alfa.   It looks like the steering wheel is back at the second window?  Now if the whole thing was 35' long it would be a very unique conversion..... or as is, a really kool toad!

[Jeremy]

..... or as is, a really kool toad!

Actually, if it was correctly designed, towing a teardrop-shaped trailer behind your bus would probably be a very good way of reducing your fuel consumption. Especially if the rear of the bus was fitted with those 'bargeboard' things that trucks use nowadays to streamline the truck and trailer together

Jeremy

[Iceni John]

That is not a GM that bus is a Flx with the top scoop and they ran hot with their straight 8 Buick engine

I wonder how Jay Leno's mechanic keeps his 400-plus horsepower 6V92 cool in his Flxible?   http://www.jaylenosgarage.com/video/hot_rod_bus/766081   It sounds like cost wasn't a major concern with that project, so maybe he also put in a huge radiator and fan.

It's also interesting that the Detroit reps interviewed say that a 6V92 shouldn't run on more than 5% biodiesel, but that's a whole other subject . . .

John

[JohnEd]

Art,

Yours is an excellent post.  Well said, relevant, fact laden, brief as possible, and no showoff'y math to derail minds.  My hat is off to you, Sir.

In the write up it sites the "limitations" of the design.  The pics of the Ferrari show it integrated into the up sloping hood.  I think the air over the hood is trying to go straight and the duct is the easiest way to go.  My point is that the design works in a flush arrangement but the flow is enhanced in the example.  I have no doubt that if the thing was integrated into the design of the rad. opening there would be significant benefit....logically and with no aero knowledge.  That may warrant further investigation for "free" air flow.

The real hangup for me was creating the "neutral pressure" air pickup to put on the ends of the Manometer.  All I can come up with is a huge fuzzy ball like the microphones wear in windy interviews.  Armed with that info I think that "lip" feature could be evaluated and have numbers attached to the idea.  I think it is important to note that all these ideas are free to operate and have an indefinite lifespan.  The other thing is that all the meticulous attention to detail can be completely offset by adding a 1/4 inch to the fan diameter or some such thing.  We are trying to regain the original capacity without the investment in new rads.

I have heard repeatedly that high pressure car wash water directed thru the rad recovers a lot of cooling by cleaning crud out of there.  That squirrel cage must be limping along if it is carrying the crud build up on the cage that I have seen in pics.  The outlet of the SC fan was a simple cut out in the sheet metal of the chamber floor.  That is a really poor way to design an exhaust and is really restrictive.  The later designs have a sort of a short duct that does flo well.  The SC inlet shrouds that close up the SC really do add to the efficiency of the fan when not needed.  That is controlled by a thermo that could operate when the need for all the cooling isn't there.  I think it is pretty much an on/off affair, however....unfortunately.  Shutting down the parasitic load of that fan when you are cruising would certainly boost MPG.  No doubt some could say we are picking fly shxt from pepper

Thanks for the info Art,

John

[RJ]

That is not a GM, that bus is a Flx with the top scoop

Clifford -

Surprise!  That's a PGA-3301, one of 840 built in 1951>1952 for the Army.  Here's a pic (from the same site Jeremy culled his) of the front of the coach - notice the trailer next to it has the same paint scheme as the rear photo.

And, for your enjoyment, I've also included a pic in military dress.

Enjoy!   

[luvrbus]

Never saw a 3301 with a scoop on the top I saw 2 before with the 4-71 engine the radiator sets in the back and the air is sucked in just above the radiator door it has a weird belt driven fan but you never know how the Army ordered a bus

[dougyes]

The MCI-D models still have the two rads and two fans mounted high in the rear with side intakes. The new ones have a HUGE fan because the new motors run hot for pollution control and the rads need to keep things tame. Stop by MCI and have a look at one. My experience, though I don't do northern winter driving, is that the top mount rads stay much cleaner than the side mounts. Of course the engine bay is much more accessible.
The J and E models use side rads with one fan doing all the work driven by a belt  to T drive.
NACA vents look cool! At least they could be used as engine air intakes. They could also be used to supply air to the passengers in the bays!

[buswarrior]

In this thread, http://www.busconversions.com/bbs/index.php?topic=9582.0

I typed some stuff about Fred Hobe's experiments with large radiator scoops.

The small ones are of questionable value, and may inadvertently swirl the air OUT of the rad opening.

happy coaching!
buswarrior

[DMoedave]

some of the GM's (the 37 series for sure) had that set up. Here is a 3703 like ours at the Hershey Pa museum showing the intake and radiator mounted above the engine.