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Whilst removing my dynamo today I was able to take a good look at the fan. I have been suffering from poor cooling and I noticed that the blades were bent well out of shape to the extent that they would be working at significantly less than optimal performance.

 

I was (pleasantly) surprised that the actual blades seem to be made of a fairly soft material and could fairly easily be reshaped to provide the correct air flow using a large pair of long nose pliers. No need to remove the fan which is a real pain!

 

Presumably over the years they had become bent out of shape by manhandling because they were so soft.

 

Anyway if you are having any cooling problems check yours.

 

Ian

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If the fan has been so bashed and bent out of shape its not pulling an air flow I would say it has a good chance It's out of balance and may be cracked . Blade flying off at 3k or more RPM will make a nice hole on the rad or bonnet. Something bent it . Maybe someone doing a ham fisted belt changing or maybe old accident damaged. Bit of a pain removing but maybe worth a closer inspection in the long run. Good time to replace the hub bolt rubber bushes and tab washers

Mike

Edited by MikeTR-6
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  • 2 weeks later...

Whilst removing my dynamo today I was able to take a good look at the fan. I have been suffering from poor cooling and I noticed that the blades were bent well out of shape to the extent that they would be working at significantly less than optimal performance.

 

I was (pleasantly) surprised that the actual blades seem to be made of a fairly soft material and could fairly easily be reshaped to provide the correct air flow using a large pair of long nose pliers. No need to remove the fan which is a real pain!

 

Presumably over the years they had become bent out of shape by manhandling because they were so soft.

 

Anyway if you are having any cooling problems check yours.

 

Ian

 

 

Ian: If you do remove the fan be sure to check that all of the rivets which fasten the aluminium blades to the steel cruciform haven't loosened. If they are loose check for stress cracks radiating from the rivet holes. If the blades are cracked, your fan is toast and you need another.

 

Another option for increased cooling air is to fit a "tropical" fan.

 

tropical-2.jpgtropical-1.jpg

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Frank -

 

not really much of an option at the price they fetch on eBay.

I think an electric fan would be better value and more effective.

Not so 'original', though, and appearance DOES matter to us anoraks.

Hence my Dynalite alternator! (though I DO have an electric fan)

 

AlanR

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Frank -

 

not really much of an option at the price they fetch on eBay.

I think an electric fan would be better value and more effective.

Not so 'original', though, and appearance DOES matter to us anoraks.

Hence my Dynalite alternator! (though I DO have an electric fan)

 

AlanR

 

How do you get on with the dynalite alternator Alan, there were some discouraging remarks on here (pricey) how long have you been using it, I like the look it gives

 

John

 

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Ahhh, the good old ST 6-blade tropical fan - TuRK has one fitted for a number of years and it does excellent job - the 13" pusher Kenlowe hardly comes on nowadays.

 

Yes, they do fetch a tidy sum on eBay - I once saw one go for £167 (plus P&P) and another for £154 (plus P&P) and I also saw two given away, one recently - they can be found at Autojumbles for about £10 -£20 if you search carefully............gone are the days you could pick one up for under a fiver!

 

Cheers

Andrew

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Ideally remove the fan, sort it carefully, and balance it on an old-fashioned bubble balancer . . . . .

 

Cheers,

 

Alec

 

I have never heard of a bubble balancer, been in engineering all my life. Any chance you can give a brief description.(I have two such fans which will need balancing if I ever get around to finishing my cars.)

Cheers ken

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Hi Ken,

 

just put bubble balancer into Google . . . .

 

Old fashioned device for static balancing of wheels and tyres, superceded by dynamic balancing. The bubble balancer still comes in useful occasionally, and model helicopter enthusiasts use them in a small version for balancing rotor blades.

 

A few years ago I gave mine to the service garage I use - I rarely used it, and I still have access to it of course. They use it regularly, it's routine for them to check any replacement component that rotates - fan, clutch, whatever. Sensible precaution, if you have a traditional approach, and the old bubble has solved the odd problem over the years. I'd guess many garages nowadays wouldn't know one if they saw it !

 

Cheers,

 

Alec

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I have one on my phone!

 

not unsurprisingly the app is called 'Bubble'

 

and its free

Edited by ians
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I have to agree with Neil, as I have said in an earlier post I have only used the electric fan a very few number of times (no mechanical fan) in stationary traffic on hot day's. Original pump etc., however the waterways in the block and head were thoroughly cleaned during the engine rebuild.

Nigel (with TS952)

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Frank

 

How did you get the fan so clean ?

 

Cheers

 

Alan

 

 

popped it in the dishwasher when she who must be obeyed was out! :P

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We static balanced the fan on our 3A. Another type of balance, dynamic balance, requires special equipment, similar to that used to balance your tires.

 

 

Have you ever balanced a lawnmower blade? This will be similar. See sketch below

First remove the fan from the hub.

Clean it up and remove all attachment hardware

Check for loose rivets and cracks around the rivet holes. If you find cracks, you fan is toast. If you find loose rivets, carefully peen them tight.

You need a temporary shaft on which to mount the fan and a pair of knife edge supports.

We used some scrap lumber and a couple of utility knife blades

Place the fan on the shaft and then onto the knife edges

The supports/knife edges must be dead level

The object is now to get the fan to remain exactly horizontal without dropping one blade. Commercially, they balance fan blades by either adding weight to the lightest blade (the one that rises up) or removing it from the heaviest blade The best place to add or remove weight is at the center of gravity of each blade. Triumph has incorporated a little piece of metal, a balance piece, which can be moved in and out until balance is achieved. We found the best approach was to first balance the fan sans all hardware, including the balancing piece. We did this and found that there was one heavy blade. Using a small grinder, we carefully removed material from the steel spider (not the blade) of that heavy one, until we got a good balance. Once you have the blade balanced, rotate it 180 degrees and check to be sure it's still in balance. If not, then your blade edges aren't level or the shaft is out of true. You can spend as long as you wish on balancing - once you get to the point where the blades will only rotate a few degrees from level then that's probably more than good enough. Now you can replace the hardware and check its effect on balance. You will find a point where the balance piece location is neutral. Then do one more 180 degree rotation. If it is still in balance you can mark the position of the balance plate and remount your fan. Once back on the engine our fan ran true without noticeable wobble or vibration.

 

tr3afan-balance.jpg

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It is a tractor engine ???????seen one run that did use 3 litres of water per day driving a PTO saw bench and yes every now and then it was white in the sump :o but it ran like that 8 hrs per day for 6 years oil changed at the end of the week :P

Edited by ntc
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