Electric fans

[bobthompson]

Many moons ago I had overheating problems on my mag engined trials car - I foolishly fitted a fat modern radiator core and an electric fan. It was foolish because  it is too fat to refit an engine fan. 
The smallest fan I could find is 9" and draws 3.5 amps. On a one-site trial, like Cobham, there are no road miles to recharge the battery, so it goes flat and needs changing at lunchtime! Bad for my digestion......
 My dynamo only puts out 6 amps max and also runs the coil ignition conversion and multiple starter motor events.
Does anybody have any knowledge of a better fan that draws less currant?

[Austin in the Shed]

I'm surprised you would need an electric fan if you've fitted a large capacity rad core for the kind of use you describe.The fan shouldn't need to run full time on a seven anyway,many run on the road without a fan belt.
Have you tried back flushing the coolant system or using a de scaler it.
Often on lightly used cars the inside of the alum water branches corrode badly and can clog everything up.
I owned a model A Ford from Uruguay,as soon as I got it on the road it overheated,did the water drop test and seemed ok ,problem persisted so had it re cored.Great for a year or two then the problem returned,core blocked up again.
Can only think the build up in the head and block loosened up and started circulating in the water again.
Can you see through the filler if the rad tubes are clear ?
I make up a conical brass gauze filter for a couple of my cars,hopefully to block the filter rather than the rad core.
I did post a photo on here once showing how bad the block can silt up,particularly around the valve chest side,a good 1 1/2" up from the bottom with no effective water cooling.

[bobthompson]

Thanks for your thoughts, but not the case. Newly cleaned and rebuilt engine, new rad core, all clean. Problem is very high revs at max load for too long up trials sections. There is never any overheating on road sections and fan never used then. Believe me - this car does not get light use!

[Henry Harris]

Water pump required.

[Mike Costigan]

Maybe the modern radiator core is unsuitable for a thermo-syphon system - have you tried refitting a standard Austin core?

[Steve Jones]

My trials Chummy, now sold, was very similar to Bob's in specification other than it was coil, not mag, and 12v. It had a modern 'thick' radiator core and it too led a pretty hard life to say the least. The only hill I ever experienced any overheating was Bealey Plantation used on the John Harris Derbyshire Trial. That's a long flat out pull where you keep your foot down and on a couple of occasions, when it was a warmer than usual late winter/early spring day we got a bit of steam at the top leading to hearing the fuel boiling in the SU float chamber when we stopped and vaporisation when setting off again. Other than that, a bigger problem was getting it to run warm enough and I often used to blank off the bottom third of the radiator.

The fan belt was set quite loose and I do wonder if having it a bit tighter so that the fan was properly driven would have helped on those runs up Bealey. Mind, with the best engine fitted, we did see 6500rpm sometimes...

Steve

[John Cornforth]

Hi Bob

Just wondering if you could fit a couple of 120 mm square computer case style cooling fans over the hottest part of the core. Usually 25 mm thick. The type designed to run from USB need 5 Volts DC at usually under 0.5 Amp each. You will need to chop off the USB plug. If you feel lucky, run them direct from the 6 to 7 volts of the battery, they will just go a bit faster. If you want to play safe, add a small series resistor to drop a volt or two and end up at about 5 volts.

Any kind of airflow is vastly better than none

Cheap enough for a try-out

[Charles P]

I have a mag engined blown car with an electric fan operated by a manual switch when the temperature gauge rises too much. It also means that I don't need to have the fan on whilst moving, which is generally pointless.
Overheating is never too far away with a blown car in modern traffic, but the battery is never troubled.

Charles

[bobthompson]

Thanks so far!
I am running 12 volts.
Mike's point is interesting!
Do many people run standard Austin radiator cores and fans successfully in situations similar to mine?
If so which type of core? Does a standard fan use much power - It was suggested to me that a fan uses at least 5% of engine power.
Reverting back does have attractions!
Steve - why did you use a modern core?

---

And Charles - what fan do you use?
My fan is also only manually switched and is never needed on the road.

[Ruairidh Dunford]

We have driven over the Alps and Pyrenees 5 up with a camping trailer in several different A7s

They all had standard cores with 4 blade fans.

Temps topped at 40c on several trips and all was fine.