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BMW fan for TR 4 cylinders


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Hi Marco,

All TR2, TR3 and TR3A’s were fitted with a short extension, part number 108493 – 3.3/4” long, which had a shorter fixing bolt, part number 108493.

For the TR4 & TR4A the extension is part number 128318 and is longer at 4.3/8”, this version requires a longer fixing bolt part number 128318.

Fitting the earlier shorter extension on a TR4 or TR4A engine allows a TR6 plastic multi bladed fan to be fitted without fouling the radiator.

As you are going to machine a new extension it maybe worth considering making a shorter version...?

Regards, Richard

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Sadly my lathe is only up to 240 mm diameter, so I can't run the fan on it like this

P1150389-b.JPG.ac80d728340c9002f3e924ba866526aa.JPG

but this way it should work - tomorrow when the Loctite is tight :ph34r:

P1150396-b.JPG.1e83b04cea57a056ea51f1709feee089.JPG  P1150400-b.JPG.6d1918e682cb99e988381112baa1770d.JPG

This is also more like on the real TR engine

Ciao, Marco

Edited by Z320
240 mm
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Hi Pete, looks huge, could you check is it's diameter, please.

Today I had the fan running up to 4,000 revs on my lathe without any problem.

But it was a little bit windy in my workshop - and the fan locks dangerous on 4,000 revs....

Sadly I have no gauge to plug in between cable and socket to measure the needed electric power.

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Sure I'll be glad to measure it when it arrives. 

This one is off a Triumph GT6  but I am told the same was used on the TR6.  They used at least three types (..possibly more ?) this 7-blade type,  the 8-blade with square tips, and another with 13-blades ..also with square tips.  I don't know if they ever got it right.

What were you hoping to achieve by mounting your fan onto your lathe ?    

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Hi Pete,

I've often been told about the lots of power needed to keep it running.

On the lathe I want to check this by one test in 500 revs steps with fan and one without.

I don't know if anyone did that, I found nothing on the www

Ciao, Marco

Edited by Z320
the !%#}+@ auto correction
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4 hours ago, Z320 said:

I've often been told about the lots of power needed to keep it running.

Marco, I wonder if you are chasing your tail trying find a solution to unsupported hearsay * ?  

< Here >  on ebay is the first car cooling fan I found (not a big search !).  It says  air flow rate is  >1130 CBM/Hr @ 2100 RPM, and the power consumption at 12v is 80w (max) for fan diameters between 7" and 14".   I cannot say if these figures are accurate but they do give us a rough idea of the power used to propel an electric motor and lightweight plastic fan, whose mass is main focused close to its pivotal centre.   Put the fan on a pencil and you'll be able to easily blow it around.   

80w @ 12v = 6.67 amps (max).  This is about half the power your windscreen wipers will use.

80w is much the same as two rather dim headlamp bulbs  ..without the side or tail lights on !

The fan is doing next to no work at all while the vehicle is passing through the air at speed.  No work means no energy is used. 

The 100bhp TR4 engine is rated at 74,000w.

Pete.

* polite expression

Edited by Bfg
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I think the power consumption from a continuous driven mechanical fan is quite a bit higher, this was discussed on here in the past. 

Waldi

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23 hours ago, Bfg said:

.

just purchased . .

s-l1600.jpg

£9.50 inc P&P

Pete,

I think you will find that this fan has an offset hub and thus places the blades closer to the radiator.

The Spitfire fan is the reverse of this and moves the blades away from the radiator.

The Spitfire fan has an overall diameter of 12.1/2", it will be interesting to learn the diameter of the fan that you have acquired.

Regards, Richard 

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Hi @ all,

a friend supported me with this to check the power of the fan on my lathe (due to the data sheet max. 4,000 revs / 1,500 Watt)

P1150412-b.JPG.ae49cf8c66f7bc099fb7573d13799e9b.JPG

This was real impressing and the fan with 4,000 revs made me VERY uncomfortable (very windy in my workshop...)

P1150413-b.JPG.fffdce237d95cf5b174a9ece2077eeec.JPG

One test run without fan and one with fan gave this results (the difference between both runs)

   500 revs:        5 Watt

1,000 revs:      68 Watt

1,500 revs:    115 Watt

2,000 revs :   241 Watt

2,500 revs:    500 Watt

3,000 revs:    780 Watt

3,500 revs: 1,260 Watt

4,000 Watt: 1,755 Watt

This might be not absolutely correct because of 3 reasons:

- 1,755 Watt is more than my lathe can supply (due to the date sheet)

- on the car the fan runs not free but behind the rad

- on speed the speed itself supports the airflow and reduces the need of power, as Pete mentioned

So finally - we are back on the crystal ball again.

And I'm pretty far in progress with part 3 of the fan project - the "half weight" fan extension.

P1150421-b.JPG.777c6efa0c4c0c331c616723225bf227.JPG

Perhaps someone can explain how the original fan and extension was balanced at the factory?

I guess all together, with the balancing washer, than marked with that tiny drill, so possible to dismantle and put together again?

But only with THIS fan, THIS extension, THIS used balance washer, the correct side of the washer out and due to the tiny drill?

Ciao, Marco

Edited by Z320
orthography
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.

Sorry Marco I cannot help you with how it was balanced, but surely your only concern is how to now do so ? (..with your new parts).

. . . delivered today.

P1330529s.jpg.1d74ac7391b258975f5fccea7f22df6e.jpg

^  194.2g including its hardened rubber, the four steel spacer tubes, and 3 out of 4 steel washers.  If I recall, the original tropical fan blade was 910g, so I'm happy with this plastic one and its refined aerofoil blade shapes. 

P1330531s.jpg.5efc46d03628a5ea34cbe8d43cf339d7.jpg 

Positioning is different to the original in respect that the new would mount onto the end of the extension piece, whereas the the original blades sat further back towards the engine.  Not having a car here, I don't know if the 20mm difference will position it too close to the radiator ?  If so, then someone has suggested using the shorter extension piece off the TR6.

P1330534s.thumb.jpg.e29d6a4ac69d7a2103b684d5529f40d5.jpg 

Different number of blades but very similar in diameter.  The perspective from it being in front of the original fan makes it look bigger in comparison, but its radius / each blade length may be perhaps 1/4" (6mm) more.

Pete

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1 hour ago, Z320 said:

1,755 Watt is more than my lathe can supply

. . . . my lathe (due to the data sheet max. 4,000 revs / 1,500 Watt)

See,  what did I tell you Marco ..about the through flow of air returning power to the crankshaft  :lol:  :lol:  :lol:

 

" So finally - we are back on the crystal ball again".   Well, you have a car, and you have a fan.  All you need now is a rolling road, a big electric fan blower to simulate traveling along the road at 160km/h,  and a spanner ..to try with the fan and then without it.. 

You Sir are the scientist ..to go down in history having definitively answered this question ..which has flummoxed motor enthusiasts for 100 years !  B)

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On 1/12/2020 at 5:29 PM, RAHTR4 said:

Pete,

I think you will find that this fan has an offset hub and thus places the blades closer to the radiator.

The Spitfire fan is the reverse of this and moves the blades away from the radiator.

The Spitfire fan has an overall diameter of 12.1/2", it will be interesting to learn the diameter of the fan that you have acquired.

Regards, Richard 

Thanks Richard you are correct about the offset. 

Having 7 blades it's not easy to measure but I'd say it was pretty close to the same at 12-1/2" (317mm) diameter.

Pete

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8 hours ago, Bfg said:

Well, you have a car, and you have a fan.  All you need now is a rolling road, a big electric fan blower to simulate traveling along the road at 160km/h,  and a spanner ..to try with the fan and then without it.. 

Sorry Pete,

too much effort, someone else could do that. I'm not hungry for the last horse power / Watt.

I keep the solid fan as a very relaiable and always working construction, I will only want to make this better (perhaps).

Ciao, Marco

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Folks,

back home from office this evening I found myself in REAL big problems!

My wife found what I did in my workshop - how can I tell here the truth now?

 

P1150428-b.thumb.JPG.6f42b882426ad2e3acda13ff6b8d665d.JPG

(She is my darling, always kidding me)

Ciao, Marco

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Cherish the moment Marco, this is a rare occasion where man&wife are both happy with new TR parts:)

Waldi

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I found a friends AH3000 had a yellow plastic assymetric fan that look identical to the BMW one... seems its available as a tropical upgrade on healeys...

then this (designed for TR6, so must fit a 4A somehow):

835-270-TT-300x285.jpg

http://www.mossmotoring.com/cooling-the-handsome-brute-with-the-texas-kooler/

 

 

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