Z320 Posted January 6, 2020 Report Share Posted January 6, 2020 (edited) Hi, on another thread I mentioned the BMW fan on my TR4A IRS instead the original steel / aluminium one. It was alreday on the car when I bought it in 2009. It is from the BMW models 1502, 1602, 1802, 2002 from the 70-ies and at Germany I have seen it on lots of TR 4 cylinders because it is highly recommended. Some years ago I thought it would be nice to have the car with the original fan, but with the original it run badly like a sack of nuts! Also I had to realized the TR part is out of balance and its weight is 1,105 gramm. Checking the volume of air when it car is ideling with an aneometer the BMW fan brings 50% more air than the TR fan. So I switched back to the BMW fan the same day. For a closer look in 2020, and not to touch my TR, I bought another BMW fan from a german TR spare parts supplier. Here it is, weight is only 225 gramm. This has alreday been on a TR and the 4 drills have already been modified by the previous owner, sadly not very accurate. To center the fan the original center bolt is very useful, it centers itself by a shoulder in the fan extension, 22 mm in diameter. The head of the center bolt is 30.45 mm, with a single wrap of cardboard this fits to the inside diameter of the BMW fan (32 mm). Next photos are from Pete / Bfg, many thanks to him. Unfortunately my spare part (don't want to touch my TR) is a simple rusty bolt and Wasser So I made my own center tool to check the center of the BMW fan And to check the position to fan on the fan extension This way it should be as good as possible in the center. Next I will do a modification on the 4 drills with steel inserts similar the way I found it on the BMW fan on my TR. If you have any questions until I can show this - please ask. Ciao, Marco Edited January 9, 2020 by Z320 Quote Link to post Share on other sites
ianc Posted January 7, 2020 Report Share Posted January 7, 2020 This fan looks very strange - it's not symmetrical (i.e. blades not at 72 degrees displacement round the centre) and the thickness of the blades seems to vary as well. Have BMW discovered that such an arrangement shifts more air than a completely symmetrical fan, or is it a crappy design? Or does a 6-cylinder engine require a different approach? Ian Cornish Quote Link to post Share on other sites
RobH Posted January 7, 2020 Report Share Posted January 7, 2020 It's probably to allow access to some feature, perhaps a mounting bolt, on the BMW engine that a symmetrical fan would obscure. Quote Link to post Share on other sites
trchris Posted January 7, 2020 Report Share Posted January 7, 2020 (edited) Would not a early yellow TR6 plastic fan be just as good ? not tried to fit one but would think its a straight swop? just a thought Chris just read some former post and see that the original extension needs replacing so not so straight forward however some members mention using a early spitfire fan which can be fitted using the existing extension would fitting a plastic fan alter balance?? Edited January 7, 2020 by trchris Quote Link to post Share on other sites
stuart Posted January 7, 2020 Report Share Posted January 7, 2020 47 minutes ago, trchris said: Would not a early yellow TR6 plastic fan be just as good ? not tried to fit one but would think its a straight swop? just a thought Chris just read some former post and see that the original extension needs replacing so not so straight forward however some members mention using a early spitfire fan which can be fitted using the existing extension would fitting a plastic fan alter balance?? If you read the other topic mentioned above you will find thats precisely what I said as I have run one on my 4a for the last 26 yrs and it works just fine to keep mine cool in traffic/high temperatures in conjunction with a separate header tank. Why re-invent the wheel. Mine fits on the original extension. Stuart. Quote Link to post Share on other sites
roger murray-evans Posted January 7, 2020 Report Share Posted January 7, 2020 2 hours ago, ianc said: This fan looks very strange - it's not symmetrical (i.e. blades not at 72 degrees displacement round the centre) and the thickness of the blades seems to vary as well. Have BMW discovered that such an arrangement shifts more air than a completely symmetrical fan, or is it a crappy design? Or does a 6-cylinder engine require a different approach? Ian Cornish Ian, I have an Fe Ford V8 engine in one of my Allards, and the mechanical fan on that has a similar asymmetrical blade layout.Although my engine isn't fitted with a viscous coupling , perhaps it should have one to iron out the potential imbalance/It's probably a science in itself, and I'm sure BMW (and Ford) put great thought into it. Would be interesting to know what that layout brings to the table though. Cheers Roger M-E Quote Link to post Share on other sites
Lebro Posted January 7, 2020 Report Share Posted January 7, 2020 Looks to me that the fan will be it's self out of balance, & so maybe this is deliberate in order to balance the front end of the crank. In which case it would not be suitable for use on a TR Bob. Quote Link to post Share on other sites
ctc77965o Posted January 7, 2020 Report Share Posted January 7, 2020 (edited) All, Owning 3 BMW 2002 i recognise that fan as the standard fan for the BMW M10 engine. The asymmetric blade arrangement IS balanced, it prevents beating frequencies - regular blade arrangements will always have resonant frequencies and this design avoids that . Rolls Royce metal fans of the 50's and 60's were also assymetric: For your info BMW offered 2 fans for the '02 range, the one seen in the pics above and a larger 'tropical' version which pulls more air...its the tropical one I use here in Malaysia. Both fans still available from BMW...as is most of the rest of a BMW2002...not bad for a 50+ year old design. Edited January 7, 2020 by ctc77965o Quote Link to post Share on other sites
Z320 Posted January 7, 2020 Author Report Share Posted January 7, 2020 (edited) This is already a pretty interesting discussion before I come to my point of interest! My mate Thomas owns a BMW 1802, the rad and fan is in pieces, there is no balancing weight anywhere, the fan is fixed on the pulley (no visco clutch) and there is no reason to see why the fan is as it is. We guess it is the way it is to reduce oscillations. He and me measured our fans and both we made a sketch, had a telefon call and some calculations, see my photo. Imagine the fan is seasawing on the Y-line: blade "B" is balanced in itself, "A" is balanced with "C", "E" is balanced with "C". That was easy? Imagine the fan is seasawing on the X-line: in the +Y direction the weight is 1 (B) + 1 x cos 65° (A) + 1 x cos 65° (C) = 1,84 in the -Y dierection the weight is 1 x cos 23° (D) + 1 x cos 23° (E) = 1,84, that's the same. You can turn the x- and y line like you want, this fan is balanced. Pretty intelligent this guys in the 1960-ies? Edited January 8, 2020 by Z320 Quote Link to post Share on other sites
Z320 Posted January 7, 2020 Author Report Share Posted January 7, 2020 s strip of steel, 3 mm wide in the vice, the fan is balancing free on the strip, believe it or not Quote Link to post Share on other sites
BlueTR3A-5EKT Posted January 7, 2020 Report Share Posted January 7, 2020 (edited) As were Chevrolet https://www.ebay.com/itm/1964-1967-Chevrolet-17-1-8-5-Blade-Cooling-Fan-327-Restored-Original/303146081349?epid=655027146&hash=item4694ea1c45:g:do0AAOSwDKBc0G78 Edited March 21, 2020 by BlueTR3A-5EKT Quote Link to post Share on other sites
RAHTR4 Posted January 7, 2020 Report Share Posted January 7, 2020 The seven bladed fan as fitted to Spitfire Mark IV and 1500 models. It also has exactly the same fixing hole centres as a TR. Regards, Richard Quote Link to post Share on other sites
Z320 Posted January 8, 2020 Author Report Share Posted January 8, 2020 This is also asymmetric..... Quote Link to post Share on other sites
Z320 Posted January 8, 2020 Author Report Share Posted January 8, 2020 Hi, on the Spitfire fan you see that I also found on the BMW fan on my TR - steel sleeves in the 4 drills. I'm shure the reason for them is not to damage the plastic when tightening the bolts. On my new BMW fan they are missing and the drills are to small for them. When you look very close through the 4 drills you see the fan has about 2 mm distance to the extension, The reason are the fins on the backside of the fan - or the "too wide" fan extension. I never realised that before on my car - perhaps it does not matter to tight the bolts anyway. Easy to put 4 washers there - but a littel bit tricky, it's more convenient to make special sleeves. Had to make the 4 drills wider and used this opportunity to center the fan correctly Ready, shure - easyer to use the one from the Spitfire, but how knew that - and I alredy have the BMWs. So waiting for material next is to make a "halfweight" extension - and finally to run the fan on the lathe. Ciao, Marco Quote Link to post Share on other sites
Bfg Posted January 9, 2020 Report Share Posted January 9, 2020 1 hour ago, Z320 said: waiting for material next is to make a "halfweight" extension - and finally to run the fan on the lathe. Are you still planning on doing this extension in steel, or are you planning on working in aluminium now.? Quote Link to post Share on other sites
Z320 Posted January 9, 2020 Author Report Share Posted January 9, 2020 (edited) Hi Pete, I will make it out of steel, weight will be about 550 gramm. I mind more to get it tall to get the belt off, concentricity and anyway solid. But this guides to an interesting question! How solid does the extension has to be? If you believe the arguments of some electric fan useres the solid one robs the engine 2 HP? Or 4 HP? The extension has to hold that power! And this plasic fans too! And my lathe with its power of 1,500 W will not be able to run the fan with 4.000 revs? True or not? I don't know... Edited January 15, 2020 by Z320 Quote Link to post Share on other sites
Bfg Posted January 9, 2020 Report Share Posted January 9, 2020 (edited) ^ The tropical fan on my 4A engine (x6 short aluminium blades on a steel hub) weighs approximately 0.9kg. And the whole pulley + fan extension + centre bolt + this fan weighs in around about 3kg. To rotationally accelerate that mass certainly takes some force, but it would be relatively little compared to the 11kg of flywheel + the 4kg of diaphragm clutch ..especial as unlike those items ; the mass of the fan + extension assembly is very close to its rotationally axis. Once a constant RPM is achieved, anything above 40mph, then the ram of airflow helps offset it, and the cooling effect of the fan is minimal compared to the vehicle's through flow of air. Then the fan blade's chord angle / angle of attack presents, at best, a deflecting sweep across that airflow ..so the energy used to maintain its rotation would be very small indeed. Conversely, I would think the tension on the fan belt, with its 2" lever arm (radius of the pulley) from the crank, which pulls the dynamo and water pump around, would have absorbed much greater power both to accelerate and at that constant speed. Of course (re)charging a battery which monitors cooling needs and drives an electric fan is not free energy. Then at high vehicle speeds, combined with tall gearing ; the airflow would try to turn the mechanical fan ..so although highly inefficient - that force would be conveyed to help turn the crankshaft ! Pete Edited January 9, 2020 by Bfg Quote Link to post Share on other sites
BlueTR3A-5EKT Posted January 9, 2020 Report Share Posted January 9, 2020 (edited) Marco - Aluminium fan mounting extensions: were available in the past from the likes of V W Derrington, Lawrence Tune and SAH. I like the idea of it made from solid so you can control the internal diameter better than the cast iron item. We had (have) one somewhere in our piles of 'stuff' . I think it was a cast item, not very nice quality either. Do not forget the front crank bolt gets done up quite tight and you need clearance over the steering rack on a modern car. Plastic fan is a nice project if a bit baffling. The first job I did in 1972 to my TR was remove the mechanical fan, which looked like Pete's with a broken blade and fit an electric fan made from an old windscreen wiper motor and a Ford Escort plastic fan. The fan fitted to the motor with a piece of Meccano (Below item 27 I think) The motor attached to the chassis cross tube with two exhaust clamps. Pete - Aluminium Fan Blades: Not beyond you to remake the missing blade and rivet on a replacement. Aluminium is easy to buy in pre cut strips, https://www.aluminiumwarehouse.co.uk/help-me-choose/grade-guide Rivets could well be 3/16" or 1/4" diameter - SP80 I would guess will do https://www.lasaero.com/products/article/J000LNXBX Rivet snap to assemble from RDG https://www.rdgtools.co.uk/acatalog/3-16--rivet-snap-489.html Cheers Peter W Edited January 9, 2020 by BlueTR3A-5EKT Quote Link to post Share on other sites
Bfg Posted January 9, 2020 Report Share Posted January 9, 2020 Aside from the usual suspects selling the kit - is there an economical way to go from a wide fan belt to a normal / narrow one ? Quote Link to post Share on other sites
Z320 Posted January 9, 2020 Author Report Share Posted January 9, 2020 (edited) Hi, first let me say many thanks to all who do not want to convince me to swap over to an electric fan! That's great! Hi Peter, thanks, I have in mind the torque to lock the front crank bolt, that's why I make the extension in steel, aluminium is to soft for the tall diameter I want to go to. Hi Pete, "then at high vehicle speeds, combined with tall gearing ; the airflow would try to turn the mechanical fan ..so although highly inefficient - that force would be conveyed to help turn the crankshaft !" you are a genius Edited January 15, 2020 by Z320 Quote Link to post Share on other sites
stuart Posted January 10, 2020 Report Share Posted January 10, 2020 15 hours ago, Bfg said: Aside from the usual suspects selling the kit - is there an economical way to go from a wide fan belt to a normal / narrow one ? One for sale in the classified at the moment. Stuart. Quote Link to post Share on other sites
Bfg Posted January 10, 2020 Report Share Posted January 10, 2020 Thanks Stuart, yes I saw that an noted it was just £15 cheaper than buying a new one from the TR shop. Is it just me or doesn't £120 + postage seem a heck of a lot of money for three pulleys and a fan belt ? Quote Link to post Share on other sites
Z320 Posted January 10, 2020 Author Report Share Posted January 10, 2020 you can use a toothed "17" instead the solid "20" with the original pulleys Quote Link to post Share on other sites
stuart Posted January 10, 2020 Report Share Posted January 10, 2020 45 minutes ago, Bfg said: Thanks Stuart, yes I saw that an noted it was just £15 cheaper than buying a new one from the TR shop. Is it just me or doesn't £120 + postage seem a heck of a lot of money for three pulleys and a fan belt ? Possibly but FWIW I paid £100 for a NOS set at Malvern from a trader about 5 yrs ago at least. Stuart. Quote Link to post Share on other sites
Bfg Posted January 10, 2020 Report Share Posted January 10, 2020 1 hour ago, Z320 said: you can use a toothed "17" instead the solid "20" with the original pulleys huh ? Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.