Dave C Posted September 10, 2014 Report Share Posted September 10, 2014 A simple question I hope! My GT6 mechanical fan has 7 blades. I see that an 8 blade version is available. Is the 8 blade version a worthwhile upgrade, i.e. does it shift significantly more air? Thanks, Dave Link to comment Share on other sites More sharing options...
Gary Flinn Posted September 10, 2014 Report Share Posted September 10, 2014 Dave If your Fan is the old Steel Bladed one then an upgrade to a Plastic Vitesse fan should help? (See attachement) A lot of people fit Electric Fans, but I've never had any over heating issues on my Vitesse with this type of fan fitted. Although when stuck in traffic in the Summer the Temperature guage needle does rise slightly above the normal position Link to comment Share on other sites More sharing options...
Dave C Posted September 10, 2014 Author Report Share Posted September 10, 2014 Mine is the plastic 7 blade fan. The blue plastic 8 blade version you have pictured is the one I was wondering about..... Link to comment Share on other sites More sharing options...
Gary Flinn Posted September 10, 2014 Report Share Posted September 10, 2014 I'm not a Mechanical Engineer but if the 8 blade fan is a bigger diameter, I guess it will shift more Air? Presumably if it's the same diameter as your 7 Blade version is should also shift more air because of the extra Blade! Or am I being to simplistic? Link to comment Share on other sites More sharing options...
Dave C Posted September 10, 2014 Author Report Share Posted September 10, 2014 Yes, my assumption was that they introduced the extra blade to move more air. I was just wondering if it makes a difference noticeable enough to spend 40 odd quid on one!......... Link to comment Share on other sites More sharing options...
KevinR Posted September 10, 2014 Report Share Posted September 10, 2014 In the big scheme of things, the mechanical fan is fairly useless. It doesnt matter whether it is 4, 7 or 8 bladed, its still fairly useless. When the car is moving, the majority of the airflow through the radiator is because the car is moving forwards so the air is being rammed through the radiator - it doesnt need much help from a fan. When the car is stationary or moving very slowly, the "theory" is that the fan will pull the air through the radiator. The reality is that the the majority of the air that is being pulled through the fan is air that has "leaked" in from the sides just in front of the fan, and very little is actually air drawn through the radiator fins. For the fan to work properly, you need a close fitting shroud around the fan and the radiator, so that the fan "must" draw air through the radiator, rather than from the sides - just like a modern electric fan has. If fitting an electric fan on the front of the radiator, the same applies, you need a tight fitting shroud to direct the air blown by the fab through the radiator. Without the shroud, the air fom the fan will just bounce off the radiator and be recirculated by the fan. Link to comment Share on other sites More sharing options...
Gary Flinn Posted September 10, 2014 Report Share Posted September 10, 2014 Yes, my assumption was that they introduced the extra blade to move more air. I was just wondering if it makes a difference noticeable enough to spend 40 odd quid on one!......... Probably not by the sounds of it! Does the Car Overheats when you are stuck in Traffic? Link to comment Share on other sites More sharing options...
Dave C Posted September 10, 2014 Author Report Share Posted September 10, 2014 I had an overheat when I arrived at Triumphfest and was sitting in the car, waiting for my wife to make an appearance! So a fairly classic situation I think, i.e. a long drive on a very hot day followed by a period with the car stationary and the engine idling. That has caused me to overhaul the cooling system; The radiator has been re-cored with a more efficient modern core The oil cooler has been re-positioned so that it no longer obstructs air flow to the radiator The front number plate has been re-positioned for the same reason A radiator cowl has been fitted So that just leaves the fan. I've read lots of comments for and against electric fans, that's why I was having a think about the original one. On the basis of Kevin's comments above most of the improvements I've made would probably make more difference when the car is moving, so I still need to do something about the fan. Link to comment Share on other sites More sharing options...
KevinR Posted September 10, 2014 Report Share Posted September 10, 2014 I have an electric fan on mine, and it only cuts in when stationary or in slow moving traffic. I fitted a capiliary thermostat in the upper hose, and this switches a relay that gets power direct from the battery, and it works a treat. The fan I have is fairly large diameter on the front of the radiator, with a cowell to stop leakage out the sides. I cant remember what car it came from, I picked it up at a general autojumble. Link to comment Share on other sites More sharing options...
jondhm Posted September 11, 2014 Report Share Posted September 11, 2014 GT6s are particularly prone to overheating because the fan is mounted on the crankshaft rather than on the water pump pulley as in most cars (including from memory Spitfires, Heralds and Vitesses). This is because of the very limited under bonnet clearance. So the fan rotates more slowly (just look at the relative size of the pulleys) and also tends to suck some air from under the radiator rather than through it. Also, the position of the fan means it blows less air around the top of the engine. Mark 2 GT6s at least have vents in the bonnet to let some hot air out. I have a Mark 3 GT6 with plastic fan, and I am not sure it is much better than a metal fan. I live in London, and have now fitted an electric fan as well, which I have adjusted to cut in when the temperature gauge gets to the 3/4 mark. So far this setup seems to work well. By the way, don't drive through floodwater in a GT6. The fan, being low mounted, hits the water. With a metal fan, this sprays the engine and floods the electrics. With a plastic fan, the blades flex forward and slice through the radiator core (and yes, it has happened to me!) Link to comment Share on other sites More sharing options...
jondhm Posted September 11, 2014 Report Share Posted September 11, 2014 Me again. Don't overlook the simple trick of pulling the choke out so the engine idles at 1,500 rpm. The fan rotates faster, so you get a bit more cooling when stuck in traffic. Link to comment Share on other sites More sharing options...
Colin Lindsay Posted February 9, 2015 Report Share Posted February 9, 2015 "In the big scheme of things, the mechanical fan is fairly useless. It doesnt matter whether it is 4, 7 or 8 bladed, its still fairly useless.|" Try a simple test: let your hot engine idle and check the temperature, then take the fan off and let it idle some more. See which overheats - with fan or without. That will tell you what difference the fan makes, even if it is marginal. I’ve never had any overheating problems, either GT6 or Herald, with a good clean radiator and cooling system, although I do use the later plastic fan on my GT6 due to slight damage of the metal original. Link to comment Share on other sites More sharing options...
dougbgt6 Posted February 10, 2015 Report Share Posted February 10, 2015 I had a modern where the electrics to the fans failed. Had a quote of £500 to fix it! So I wired up a switch to the dashboard to turn the fans on and off, £5. I was surprised to find I didn't need the fans at all on the motorway or even in slow moving traffic. Only in a stationary queue for more than 10 minutes did I need to turn the fans on. On the other hand didn't the Spitfire aeroplane upgrade from a 4 blade to a 5 blade prop? Link to comment Share on other sites More sharing options...
Gary Flinn Posted February 11, 2015 Report Share Posted February 11, 2015 I had a modern where the electrics to the fans failed. Had a quote of £500 to fix it! So I wired up a switch to the dashboard to turn the fans on and off, £5. I was surprised to find I didn't need the fans at all on the motorway or even in slow moving traffic. Only in a stationary queue for more than 10 minutes did I need to turn the fans on. On the other hand didn't the Spitfire aeroplane upgrade from a 4 blade to a 5 blade prop? The Original Spitfire had a two blade fan!, most had the 3 blade type during the war, but the later Griffin engined versions had 4 Blade I think? Link to comment Share on other sites More sharing options...
dougbgt6 Posted February 12, 2015 Report Share Posted February 12, 2015 Spitfire mk XIV had a 5 blade prop http://www.military-history.org/articles/world-war-2/battle-of-britain/6-unusual-spitfire-adaptations.htm Picture 6, at the bottom. Link to comment Share on other sites More sharing options...
Gully Posted February 12, 2015 Report Share Posted February 12, 2015 The prototype Spit and early production Mk I airframes had 2 blade props, but were soon replaced by a 3 blade unit. The 4 blade prop was introduced on the Mk VI (aside from a few Mk V experimental high altitude airframes). The Merlin engine Spits from the Mk VI onwards had 4 blade units, whilst the Griffon engine aircraft had 5 blade props. There's a late mark Griffon engine Spitfire on the air show circuit with two contra-rotating 3 blade props - I think it uses a Shackleton gearbox arrangement. Gully Link to comment Share on other sites More sharing options...
Gary Flinn Posted February 13, 2015 Report Share Posted February 13, 2015 I knew someone would know! I've seen a Griffin Engine in the local Industrial Museum. A guy I know used to have a Lancaster Merlin engine in his Garage!! He lived near a factory that used to Scrap them after the war and recyle the Aluminium/Etc, don't know what happened to it though? There's also a guy who goes round the local carnivals in Derbyshire who starts up and runs a Merlin Engine on a stand out of a Scorpian Tank I believe, it sounds awsome with no silencers and is only in a mild state of tune, with no Supercharger, still knocks out 850 Bhp though Link to comment Share on other sites More sharing options...
Pete Lewis Posted February 13, 2015 Report Share Posted February 13, 2015 Rolls Royce heritage has a merlin on a trailer , and 2013 saw peter grieves from carlise run his up at our duxford show awesome but they have a cut down prop, or you get grass with the experience Pete Link to comment Share on other sites More sharing options...
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