engine side valances or mechanical fan?

[dougbgt6]

I wouldn't lean on the side valences, they are cardboard with a thin strip of insubstantial metal on the top. The club shop ones are aluminium and very nice. Some are coming my way soon!

[Badwolf]

The ones I have made are 3mm aluminium with the angled top piece rivetted along the top all to be finished in black POR15 once I have decided whether to add some venting holes.

[PeteH]

Hi, Been browsing cos it` too early in the day to fire up the Angle grinder!. (6-15am) and read this post.

How about. Triumph fitted the valences with the priority intention being to keep muck off the engine?. So therefore they have no design intention as far as cooling or air flow is concerned?. As with the vast majority of 50`s designs, the Herald and it`s derivatives came with an engine driven fan, normal for it`s era?. Conversely Most moderns now have thermostatically controlled electric fans as standard. As most of us will be aware there was also the "Viscous" Fan, fitted to many cars in the Period approx 1970 -85 Ish? too. That in itself suggests that there is some reason for this move, car makers are generally adverse to spending extra on anything as it effects the "bottom line"!, and an electric fan with associated control's must be a more expensive item than a plastic one bolted to the front of the engine?.

The movement of air through a radiator, is needed to be thorough, so cowl design is an essential parameter, a design which keeps the airflow as smooth as possible and directs it to all parts of the Radiator, will transfer the maximum possible heat from the radiator up to its design capacity, regardless of the motive type. The fan efficiency, its ability to move a design volume of air, with as little flow disturbance, is likely to be as responsible for maximum cooling and fan speed could be a critical factor too.

Looking at the foregoing, and without access to a wind tunnel in which to conduct tests at various speeds. My "gut" feeling would be that whatever the decided method of motivation, making sure that the airflow though the system, including the area in front of the vehicle, the grill and any lights, badges etc, which will disturb airflow, cowling in front of the radiator even? to direct the maximum air in to the matrix, efficient fan blade design, plus a shroud with the least "loss" would be the desired outcome?. In aerodynamics "Smooth" is God, reducing, or more to the point, controlling "eddies" is virtually a discipline in itself.

 

Pete.

[Anglefire]

I read the article on the Canley Classic site which talks about electric fans and their opinion is that they in general block some of the radiator reducing it’s efficacy therefore resulting in the fan coming on more to keep the engine cool. 

Imho the best sort of fan is an viscous one. No power loss when the vehicle is keeping cool due to natural air flow but as the temperature off the radiator increases it stiffens up pulling more air through. And being progressive doesn’t result in big swings in temperature if sized correctly  

Modern ones have an electric heating element in them too but that is so that the air conditioning condenser can increase air flow to keep it working correctly. 

[PeteH]

Hi

I had a suspicion, that some Triumphs where actually fitted with Viscous Fans?. But Not the Vittesse or Herald according to Haynes?.

Pete

[Anglefire]

US market ones had them on some Spitfires. By all accounts not terribly reliable. Don’t know why unless it was just early tech. 

[Pete Lewis]

Some 1500 spits amnd many of the 2000 mk2 range had viscous,  although not very techy versions

More goo and paddle wheel , bearing failures are good at failing

Pete

[Blitz]

On 12/02/2017 at 0:29 PM, dougbgt6 said:

I find myself agreeing with everything that's been said, swayed back and forth by each additional post!    

 

I DO think the valences channel the hot air, against the bulkhead yes, but also under the gearbox. But of course only at speed, sitting in traffic they're no use at all!

 

Last year my GT6 had it's first overheating incident and blown head gasket in 40 years. I sat helpless in a traffic jam for 45 minutes watching the gauge climb. Had I had an electric fan it would have cut in and probably saved me. However, had the disaster not happened I wouldn't have taken the head off and found the blocked water pump, almost certainly the root cause of the problem. I would still be driving around in blissful ignorance,

 

That's the issue with electric fans, they can very effectively cover up the inadequacies of the cooling system. The mechanical fan should be able to cope. So what to do? I'm gonna fit an electric fan!   This will be additional to the mechanical fan and on a switch, to be used only in emergency. In this way I will know if the mechanical fan is becoming less effective and remedial action is required.

Old thread but like your thinking on this. emergency electric fan rather than covering up potential problems. File your comments in my head for later use 

[dave.vitesse]

The UK TR7 was also has the viscous Fan, works well. The main advantages of an electric fan is it reduces warm up time and if a large enough one is fitted it helps reduce overheating in jams traffic.

Dave 

[rlubikey]

I'm no expert on this, but before the early 70's Triumph and others used to quote horse-power at the flywheel with everything stripped off the engine. Then, around 1971, Triumph started quoting DIN horsepower which was typically about 5.5% lower. (150hp TR6 became 142hp) My guess is that they could get some horses back with a viscous fan. I seem to recall, back in the day, that they used to say it gained 2- or 3hp - not much, but in the game of spec-manship, perhaps they thought it was enough to justify the extra cost in increased sales. Doesn't a viscous fan make the car quieter too? More civilised = more sales. These are both small but important gains.

Regarding electric fans blocking the radiator, they freewheel in the breeze causing very little difference when you're moving. If the cooling system is that marginal, there's something wrong with it. In front or behind, it doesn't matter (much) - a blind behind the radiator blocks it (almost) as much as one in front! I've read the Canley's story and I don't believe it - there must have been another variable at work there.

As well as spreading the flow through a radiator, a cowl stops warm air from nipping back (well, forwards actually!) through the radiator and being drawn through yet again, reducing the cooling capacity as the cumulative air temperature is higher. They didn't bother much with cowls back then, but one example happens to be my area of expertise. The Atlas van started with the humble 948cc Herald engine. Then Triumph dropped the 1670cc wet-liner engine in for more power but, because they were unable to enlarge the radiator any more (no space), they kept the mechanical fan but added a cowl  to ensure the air went through the rad only once.

The problem with electric fans on old cars is they only come on intermittently in slow or stationary traffic (and not at all out on the open road) so under-bonnet temperatures soar when you're queueing, even though the engine's cool enough. For example, my electric fans come on for 20-seconds or so every few minutes. This is not good for our old fuel systems with no mixture adjustment as the fuel warms on its way into the engine and so a continuously running fan helps keep things a bit cooler even when the thermostat is closed.

Cheers, Richard

[rlubikey]

Oh, and on DIN hp, the Dolly Sprint was going to be the Dolly 135 - that's 135hp. Well, 127hp is suspiciously 6% lower than 135 so, I reckon that, despite stories that they just couldn't guarantee 135hp off the production line, the change was really to do with the company changing from Imperial horse-power to DIN pferd-stark! Just a guess of course.

Mind you, aren't we lucky they called it the Sprint - what a great name!

Right, that's enough thread-drift.

Cheers, Richard

[dave.vitesse]

BHP went from SAE (a US spec) to DIN a (European spec) around 1970. Around 6% lower with the DIN. Though some of the spec like the early TR6 were some what higher than they actually were. All the UK car makers did it. The truth is in the performance and 138 to 140 SAE was nearer the mark for the early TR6. 

Both the GT6 and the Vitesse cooling systems are near the limit, this being due to having a large engine in a small spare. OK on the open road but the temperature can start to rise when stuck in a traffic jam.

On the Vitesse the original washers holding the rad to the chassis were neoprene, the replacements are rubber and appear to give too much heat insulation which doesn't help. I removed the rubber type and used large metal washers, this helped. The heat is then carried away from the rad frame into the chassis, every little bit of cooling helps. This was on a new rad and recon engine. I tapered the washers to get the angle the rad correct and haven't had any vibration problems with the rad due to not have any insulating washers. The GT6 doesn't have any insulating washers and is bolted directly down the chassis. I found removing the side screens helped in a traffic jam. Even with a 2.5 lump under the bonnet.

Never had problems with the Herald or Spit I fitted a full length rad.

TR7, Dolomite 1850/Sprint and Stag must be flushed out every year otherwise the rad can get blocked up with particles from the aluminium head. I guess the head will dissolve eventually! 

I agree the electric fan in front of the rad does windmill, may be use it as a generator? I haven't noticed any reduction in the cooling with a fan in on the front of the rad.

Dave

[Anglefire]

I suspect a lot of the canley Classic article is when the electric fans had a big cowl which although directs the air through the fan when running, effectively restricts the air when not. Or the brackerery shields the rad particularly when the rad is the smaller type and is marginal at best. 

I fitted a full width rad to my spitfire and has run lovely since. Temperature sits smack in the middle of the gauge.  It used to overcool which although it had a thermostat fitted I suspect it was knackered or the wrong temperature range.