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A new cooling discussion

Posted: Fri Jun 28, 2019 1:51 pm
by CNHSS1
If you wish to check that your are getting airflow through the core, and its tracking the road speed and not stalling above a certain speed, if you have a modern leccy fan mounted on or very close to the BACK of the rad core, you can connect 2 x long cable to the cabin and to the fan, and connect to a digital multimeter in the cabin. The airflow will often windmill the fan, so will act as a dynamo. The higher the road speed, the higher the meter voltage reading :-)

A new cooling discussion

Posted: Fri Jun 28, 2019 1:51 pm
by CNHSS1
Doesn't work with those original bent tin 'stirrers' :wink: :roll:

A new cooling discussion

Posted: Sun Jun 30, 2019 5:14 pm
by chrisgallacher
Old and Slow wrote:
Thu Jun 27, 2019 8:44 pm
When I bought 660XYB it had a bracket system behind the rad holding the existing motor; to restore some originality I put the motor in front of the rad where it ought to be, which is probably why I've introduced potential cooling issues. I've only boiled over once, when I forgot to turn the fan on. Do I have a problem? I don't really know, as the original arrangement gives the gauges a 30-second inbuilt response delay time; I turn the fan on when the needle starts to climb above the "N" and it takes a while for it to drop. I already have the bracketry and putting an auxiliary fan behind the rad might be "belt and braces" but like insurance, you hope it will never be needed. It will, however give my navigator (SWMBO) peace of mind, and who's worried about an extra 10 amps out of the dynamo (!).
Going back to Philip's comments about the Sabre Six, when I got mine it just had the original (I think) electric fan in front of the rad. It's not that close coupled and isn't that powerful - it's ok in general use but I wouldn't want to rely on it in queueing traffic on a hot day. I still have it, controlled by relayed, manual switch:
rad1.jpg
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But I've also fitted a modern, powerful & reasonably discrete electric fan behind the rad. It's not ducted but the diameter covers much of the rad area and is placed as near to it as possible without fouling. It's from (I think) a Vauxhall Omega, bought on ebay a few years ago for next to nothing and it sucks a howling gale through the rad. It does place a fair load on the electric system, but having converted to an alternator that's less of an issue. It's properly relayed, switched by a temperature sensor in the top hose with a manual over-ride switch. I hate the idea of overheating especially with an alloy head - I get very nervous and stressed about it. We're just back from the East Anglia Classic Rally held yesterday - the hottest day of the year - and everything stayed nicely under control both on the drive up in stationary traffic and over the whole day of caning the car in stifling temperatures.
rad2.jpg
rad2.jpg (114.77 KiB) Viewed 332 times

A new cooling discussion

Posted: Tue Aug 06, 2019 8:59 pm
by Old and Slow
I came across this whilst doing a bit of light reading ("Aeronautical Engineering", Odhams Press, date unknown, looks like early '50's) and for 4-stroke petrol engines it states (p 224) that the total energy from the fuel is output as follows: 30% as useful power, cooling system dissipation 30%, energy lost via the exhaust system 40%.
This means the Rad has to dissipate approx the same as the engine is outputting to the wheels. That's a lot of heat to be got rid of, I reckon!
Just thought you'd like to know this.

A new cooling discussion

Posted: Tue Aug 06, 2019 9:15 pm
by philhoward
Modern spark ignition engines are floating around 40% efficiency, I believe? Most of those are also turbocharged, hence recovering wasted energy from the exhaust.