Fan Blade replacement

[Bill_qaz]

I think we need to form a Berni fan club
The wearing of the club hat will of course be mandatory.
10" or 12" are both acceptable Screenshot_20260615-165735_Chrome.jpg

Sorry, only Red or Yellow will be permitted...

Edited accordingly to suit your wishes Sherlock

[svenedin]

I can understand that when the car is moving forwards there is so much airflow through the radiator that it makes no difference whether it is a 10" or a 12" fan. Surely though it does make a difference when stuck in traffic in hot weather especially as in Berni's case when there is restricted flow through the radiator grille. In France I mounted my rally plaque on the bumper so as not to impede flow through the grille. This turned out to be a good move as the weather was very hot for days on end. Despite this, things did get very hot under the bonnet although the engine never overheated to my knowledge (no temperature gauge).

Stephen

[Bill_qaz]

I can understand that when the car is moving forwards there is so much airflow through the radiator that it makes no difference whether it is a 10" or a 12" fan. Surely though it does make a difference when stuck in traffic in hot weather especially as in Berni's case when there is restricted flow through the radiator grille. In France I mounted my rally plaque on the bumper so as not to impede flow through the grille. This turned out to be a good move as the weather was very hot for days on end. Despite this, things did get very hot under the bonnet although the engine never overheated to my knowledge (no temperature gauge).

Stephen

If you look at Bern's picture it looks as though the smaller length fan has a wider blade. So the air displacement may be closer than you would think. The pitch of the blade would also have an effect as well as the pulley diameter.
You wouldn't know your engines temperature without a gauge unless it reached the point boiling and venting from the cap.
There are also differences in replacement radiators which many of our cars would of had by now.

[Mervin]

"when there is restricted flow through the radiator grille."
Depending on the restriction, would it matter how big the fan is? The restriction will only allow a finite volume of air to pass through.

[geoberni]

If you look at Bern's picture it looks as though the smaller length fan has a wider blade. So the air displacement may be closer than you would think. The pitch of the blade would also have an effect as well as the pulley diameter.
You wouldn't know your engines temperature without a gauge unless it reached the point boiling and venting from the cap.
There are also differences in replacement radiators which many of our cars would of had by now.

Optical illusion by the camera, both blades are 2.5" wide.
I fitted Basil with a temp gauge because being a 1098 he had the facility readily available and, as I was fitting the Police signs, I wanted to know what effect it would have on the radiator performance.
I have noticed that on the open road at 55-60, if it's a hot day, the temp does start to slowly creep up from middle of the 'Normal section' towards the Red Line, hence why I started on this journey of discovery by buying a 2nd blade to make a X Pair, and stumbling into the 10" or 12" question...

[geoberni]

"when there is restricted flow through the radiator grille."
Depending on the restriction, would it matter how big the fan is? The restriction will only allow a finite volume of air to pass through.

But additional 'fan assistance' may reduce losses around the outside of the radiator, once it's past the grill...
I don't know, it's just a line of enquiry that caused me to stumble onto what seems to be 2 different fan blades supplied on the same part number.

[geoberni]

Just to update everyone, I was at the National on Saturday and if a bonnet was up I was looking at the fan blades....
Ignoring the few who had electric fans or multi-blade plastic fans, for whatever reason, my guestimate is that about 7/10 had a 12" blade. The rest were 10" including one car, a Traveller if I recollect correctly, which had a 10" double blade on a standard engine setup.

Also, all the blades I saw available with the stallholders were 12".
I seriously think that Morris/BMC had both lengths of blade under the same part number, most probably from 2 different suppliers.
That would also explain why the 'double blade' fan option was a different number rather than just stating to fit 2 individual blades.

I brought another 12" blade from one of the sellers with an 'Any item £1' section, so if I need to double up on Basil's fan, I have one available on the shelf.