Electric Fan

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Old and Slow
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Electric Fan

Post by Old and Slow » Mon Aug 08, 2016 2:34 pm

On 660XYB the fan motor is currently mounted on a cross-member fitted aft of the radiator and in front of the engine. The DC motor has its polarity reversed so that it sucks air through the rad, but this means the fan blade profile is "backwards" and less efficient.
The mounting bracket on the cross member in front of the radiator is still in situ, so I'm thinking of putting the fan back where it originally went.
Does anyone know why this mod was done? Perhaps to keep the motor out of all the stuff (snow, rain etc) that comes in through the grille?
If you can help solve this riddle I'd appreciate it, thanks.
Also, the fan is currently manually operated, I'm thinking of fitting a temperature switch as well. Any suggestions for type, location etc?
Philip


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Re: Electric Fan

Post by peter freeman » Mon Aug 08, 2016 4:05 pm

Kenlowe adjustable controller - KLM1416 - sensor fits in the top pipe.



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Re: Electric Fan

Post by scimjim » Mon Aug 08, 2016 4:11 pm

You've got a few options off the shelf - sensor in hose as Peter suggests, sensor in rad fins, sensor inline with a coolant pipe or modify the rad to take a sensor (otter switch or modern screw in).


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Re: Electric Fan

Post by toomanysabres » Mon Aug 08, 2016 6:13 pm

.....and any option needs a relay in circuit. Although the Kenlow kit is a mechanically operated microswitch by the capilliary so its effectively a relay


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Re: Electric Fan

Post by Old and Slow » Tue Aug 09, 2016 2:28 pm

The fan motor is 8 amps, so I'm planning on fitting a relay anyway.
The Rad has a fitting in the top chamber for what looks like a disused capsule (big brass nut holding a lump of something in the water), so this might be a possible approach, although the Kenlowe adjustability feature seems overkill. The Otter switches have hysteresis, ON-92 deg and OFF-79 deg seems sensible, and if I can site one in the existing fitting, so much the better.
But, going back to my original query, I'll fit the fan in its original location and see what happens!


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Re: Electric Fan

Post by piman » Wed Aug 10, 2016 9:41 am

Hello Old and Slow,

the Kenlowe thermo switch is rated at 30Amps, just for information.

There seems to be a view that a fan behind the radiator is more efficient as it is out of the air flow; not a view I agree with as any air cooled heat exchanger has to have a clear outflow as well as inflow so the restriction of the fan applies in either side. In your case as the blade is not ideal it should be less efficient.

Alec


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Re: Electric Fan

Post by Old and Slow » Thu Aug 11, 2016 6:37 pm

Hi Piman,
Thanks for the info on the Kenlowe kit. IIRC from my aeromodelling days, reversing a prop drops the efficiency to around 65% (useful for checking performance prior to crashing), so fitting it in front of the rad should improve things, and I agree: I can't believe that putting 20 sq.ins or so of motor in front will make a significant drop in cooling efficiency. Interestingly, the mount was rubber-bushed so that it isolated the motor body from the chassis; as the car is still positive earth I think someone thought the motor was negative earth and needed isolation: in fact the body isn't connected electrically, so putting it back at the front is a no-brainer, already done, tested and now I just need a hot day for a long run to see it keep the temp. gauge at N.
BTW, I mentioned a fitting at the top of the rad, but if the water level drops then the sensor won't function, so attaching it under the top hose is probably more fail-safe.
Philip


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Re: Electric Fan

Post by scimjim » Thu Aug 11, 2016 7:00 pm

From a radiator efficiency point of view (ignoring the make up of the rad) the ratio of pressure in front to behind is what determines the speed of airflow across the cooling fins. While mechanical obstructions will affect that ratio and prevent equal coverage, they're not the main determining factor. I often wonder how much calculation went into the GT/GTE inlet/outlet size and shape :-)

And the efficiency of a blade rotating in either direction is dependant on lots of things, mainly the profile, sweep and tip shape (ducting and paddles), so any blanket figure is misleading - I'm sure some blades would be as low as 10% when reversed :-) the original fan is possibly a straight blade with little profile, so is probably surprisingly efficient in reverse (relative to designed direction)?


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Re: Electric Fan

Post by Old and Slow » Thu Aug 11, 2016 10:02 pm

Hi Jim,
For the record, it is a Lucas motor and the fan is multi-bladed nylon with aerofoil section blades (somewhat like Clark Y or RAF32 in section, but with a Payne outline of parallel leading and trailing edges) that increase their pitch closer to the hub, like a real propellor!! Geoff Cooper and I had a bit of a discussion about it at Silverstone after a bit of overheating (I forgot to turn the fan on). :oops:
Of course in former times I was running diesel engines at 15,000 rpm but the general principle we applied was that the moulded prop blades were "100%" efficient when fitted the correct way round and probably just over half as good when fitted backwards.
There is no shroud on the Sabre Six, I think fitting one would be an advantage, but probably an unnecessary complication.
I suppose the original Ford fan on the engine pulley would be just as (in)efficient whichever way it was fitted, being flat metal blades. :)
Philip


Philip Needham
Ashley-bodied TR3; '54 Ford Consul; '55 AC 2-Litre Saloon;'65 850 Mini; '70 Ford Zodiac MkIV; XR3i
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Re: Electric Fan

Post by scimjim » Thu Aug 11, 2016 10:12 pm

I'm surprised the blades have so much shape to them - the later ones don't. The metal blades only fit one way and as you say are almost flat so very little pressure generation.


Jim King

Current: SE5 (8Ball), TI SS1 (snotty), 1600 SS1 (G97), 1600 SS1 (C686CCR), 2.5TD SE5a (diesel 5a), 6 x random other SS1s.
Previous: SE5, 3 x SE5a, 2 x SE6a, 3 x SE6b, GTC, 2.9i GTC, 3 x 1600 SS1, 1300 SS1, Mk1 Ti Sabre, Mk1.5 CVH Sabre
Chief mechanic for: 1400 K series SS1 (Megan3), 1400 CVH EFi SS1 (Grawpy), Sabre/MX5 auto (The Flying Broomstick),
1300 SS1 (Number One) & Sarah's coupe.
CURE THE FAULT - NOT THE SYMPTOMS

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