This will be anathema to the purists ....

K

krswen

Junior Member
but has anyone ever made a fan shroud? Done right they can improve fan performance significantly.

Another interesting fact I ran across the other day in one of my aerodynamics textbooks (this guy needs to get a life, right?) .... in the chapter on propeller theory; a single blade is the most efficient. Adding blades does move more flow, but since they begin to interfere with each other (wake shedding), 4 blades doesn't move four times as much flow.

It would appear that a well-designed two-blade with aerodynamic twist (not just fixed camber) like Henry made may be close to ideal.

Ken
 
krswen said:
but has anyone ever made a fan shroud? Done right they can improve fan performance significantly.

Another interesting fact I ran across the other day in one of my aerodynamics textbooks (this guy needs to get a life, right?) .... in the chapter on propeller theory; a single blade is the most efficient. Adding blades does move more flow, but since they begin to interfere with each other (wake shedding), 4 blades doesn't move four times as much flow.

It would appear that a well-designed two-blade with aerodynamic twist (not just fixed camber) like Henry made may be close to ideal.

Ken
Click to expand...

Ken, I agree that performance may be enhanced but you don't get something for nothing, ...and thus there will be a trade-off. The main question is "why" do you or I need a shroud? Most would agree that an engine needs to run fairly warm to enduce optimal combustion, --and if the fan shrouded system allows for lower coolant temperatures, "what" have you gained? Many of us with good radiators have even driven our Model A's without any cooling fan in traffic with no adverse overheating effects. I guess it is nice to know some of that aerodynamic stuff but is it really applicable on a restored Model A?
 
I am not an engineer and have no real idea of flow, or fluid mechanics. However, the major auto companies obviously feel multi-bladed fans are the most efficient and have spent a lot of money researching the issue. Since they wouldn't spend a penny more per vehicle than they have to, there must be some sound reason why they, as well as computer fans,window fans, ceiling fans-pretty much any fan I can think of, has multiple blades. ??
 
A fan shroud helps when there is little or no air pressure on the front surface of the radiator, like going less than 10-15mph, when you are drafting (NASCAR!) or in traffic with a modern car that has the radiator behind both a small area grille and an A/C condenser. In a 2mph 100*F parade it may be good to have a shroud, but it won't fix other problems that cause a hot motor on an A, like deteriorated solder between the tubes and fins, or scale and crud. If you want a shroud, you can buy one from one of the catalog guys, no need to make your own.

A two blade fan (or any number of blades) are most efficient when moving forward, into laminar airflow. Multi blades move more air in a static situation, whipping through their own turbulence wake. The horsepower penalty is nullified in modern cars with a thermostatic and centrifugal fan clutch.

If you want to try something trick (for a model A) to increase low speed cooling, rig up a multi-blade fan with a thermostatic fan clutch. Good luck with the clearance issues. Maybe with a short flatty V8 pump? There are multi blade flex fans sold to rodders to eliminate the clutch, but they are extremely noisy.
 
1. carb. air filter
2. T/stat
3. overdrive
4. add on fuel filter
5. four bladed fan
6. temp.guage
7. rad. overflow bottle
8. elect. ign.
9. fan shroud ?
10. i left off GPS :eek:.
11. hyd brake's
can any one think of any more improvements?

Poor ole Henry, if only he had known a little more about "A" model's :rolleyes:
Just kidding :D, great info. here. Thanks
 
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Blessyou boys,

I have always felt the engine pans assist the cooling as more air is directed to the back of the engine. Henry continued to install engine pans into the late 30's and I don't think it was to keep the engine clean ? Only my thought, maybe an engineer could shed some light on this subject.

Ron
 
I have been wondering about fan shrouds for a while on the A. I am used to the 4x4 and Jeep world as my main automotive vice. A shroud is used to direct air flow over the entire area of the radiator core when the fan is pulling air through, at low speeds or when the car is stopped. Without the shroud (as in a model A) only the radiator core surface directly in front of the fan has air flowing through it and is aiding in heat rejection. The shroud allows the fan to pull air over the entire area of the radiator core.

With the low power of the A and the relatively large radiator core area, a shroud isn't really needed. Also an A has a nice easy airflow path, through the radiator and out the hood shrouds.

One situation that it would be beneficial in is a parade, the shroud would help the fan to pull air over a greater radiator core area, thus improving cooling.

In a properly maintained A with a good effective cooling system, a shroud isn't needed, in fact you might find that with a shroud a thermostat is needed to help maintain engine temperature and not "over cool" the engine.

If you want to learn more about shrouds, just start reading about overheating problems in Jeeps when folks install a 300-400 hp V8 and then go wheeling at low speeds. Air needs to be pulled throught the entire radiator core area, flow over and around the engine and then find it's way out the bottom of the Jeep.
 
I might be wrong but did not the 28 come with a shroud, and stop putting them on, seems like the rest of the model a did fine without them,
 
The Very Early A had a fan schroud, referred today as a tabby shroud. The schroud was modified and a tray added at the bottom to accomodate the right headlight wires, this schroud continued until early 1929, then was eleminated. I have always felt it was a way of cutting costs not that the schroud didn't assist in cooling ?

Ron
 
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