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Z320

BMW fan for TR 4 cylinders

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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.

P1150305-b.JPG.fce5c781632d236188dc7d8444b5bf38.JPG

This has alreday been on a TR and the 4 drills have already been modified by the previous owner, sadly not very accurate.

P1150342-b.JPG.2cd3377b2e4a0e73180820ea854cfcbd.JPG

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.

P1150343-b.jpg.56f3a4ce478f077b4cf710fd3a361238.jpg  

P1150344-b.jpg.38283d262cf0b973752a449443e005ed.jpg

Unfortunately my spare part (don't want to touch my TR) is a simple rusty bolt and Wasser

P1150346-b.JPG.b6e4879add8a2fc855237ba717b06036.JPG

So I made my own center tool to check the center of the BMW fan

P1150348-b.JPG.685e180b7baa1ac0e7fb35a7c004136a.JPG  

P1150357-b.JPG.dddc9d02337ceccfdd45d4871e29e51a.JPG  

P1150359-b.JPG.7fa2c7ebdb292d023d90f690974d3c37.JPG

 And to check the position to fan on the fan extension

P1150360-b.JPG.646faa918eb727fd332947a8cec09cd0.JPG  

P1150361-b.JPG.b40481677843db0aac23cc15383dc168.JPG  

P1150362-b.JPG.88de7c16720b0a59dda0176294a3ba83.JPG

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 by Z320

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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

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It's probably to allow access to some feature, perhaps a mounting bolt, on the BMW engine that a symmetrical fan would obscure.

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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 by trchris

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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.

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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

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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.

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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:

ue32648u.jpg

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.

11520786120.jpg

Edited by ctc77965o

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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.

P1150368-b.thumb.JPG.252af2f6976691c6fb054267a0c634f0.JPG

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 by Z320

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s strip of steel, 3 mm wide in the vice, the fan is balancing free on the strip, believe it or not

P1150371-b.thumb.JPG.5c58e388297083aa6db2c9e5089d965e.JPG   P1150372-b.thumb.JPG.29e0cc007e5f32d6d18f63c854255105.JPG

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 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

image.png.26e668c12e41d9afc9ca6d9276e82178.pngimage.png.2233aa0c75894ec0d45f547b5769ee0e.png

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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

 

1.jpg

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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.

 P1150373-b.JPG.2bc770c3b472e6cd35772566a948e904.JPG

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.

P1150374-b.JPG.f7101615f965b60296669a569f97c2bb.JPG

Easy to put 4 washers there - but a littel bit tricky, it's more convenient to make special sleeves.

P1150379-b.JPG.2cba102c1c8e25f0ea6d5bc10f7c3a08.JPG

Had to make the 4 drills wider and used this opportunity to center the fan correctly

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P1150385-b.JPG.cff9e16f87011cfe6ff1ac4b86ca0326.JPG

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

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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.?

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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 by Z320

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^ 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 !  B)

Pete

P1330387as.jpg.568e9591120b9f44bae9f2dd4f53343f.jpg

Edited by Bfg

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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

 

PartsChart_02.jpg

Edited by BlueTR3A-5EKT

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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 ? 

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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 :lol:
 

 

Edited by Z320

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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.

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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 ? 

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you can use a toothed "17" instead the solid "20" with the original pulleys

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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.

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1 hour ago, Z320 said:

you can use a toothed "17" instead the solid "20" with the original pulleys

huh ?

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