<VV> Plastic radiator fans

hugo at aruncoaches.co.uk hugo at aruncoaches.co.uk
Sun Feb 4 23:01:16 EST 2018

Pine cones, and other plants and mollusc shells, grow their spirals 
according to the Fibonacci sequence (each number being the sum of the 
previous two numbers, i.e. 1,1,2,3,5,8 etc). It is roughly a ratio of 
1.6:1. For some weir mathematical reason you can get the same sequence 
by applying the square root of five divided by two minus one.
This fan reminds of that design process.

On 2018-02-04 14:14, kevin nash via VirtualVairs wrote:
> Thanks John, I appreciate that! I had been staring at that thing on a
> computer screen
> for a really long time before it had been made… I still get geeked
> out just from how it
> looks, almost like it grew. A friend had made a rendering of it from
> my computer model, and it made it look like it was mirror polished
> aluminum, and after staring at
> that version of it for about 20 minutes, I decided it was way too
> cool looking to exist
> only as a “vapor fan” and gritted my teeth and spent a SCAREY amount
> of money on it to get a couple of prototypes done for test purposes.
> Hopefully it tests as well in real
> life as it looks and has done on my test fixture!
> Kevin Nash
> Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for 
> Windows 10
> From: John Howell<mailto:32chevy at 0306.org>
> Sent: Sunday, February 4, 2018 1:56 PM
> To: kevin nash<mailto:wrokit at hotmail.com>
> Subject: Re: Re: <VV> Plastic radiator fans
> Kevin,
> If nothing else your fan design is really cool looking !
> John Howell
> On 2/3/2018 5:57 PM, kevin nash wrote:
>> Plastic Radiator fans have been a mixed bag... in some applications, 
>> they seem to last a long time, in others not very long.
>> The big differences are how high the peak temperature is, how high 
>> the peak rpm is, and how hard is the shock from changing
>> rpms, and of course how much horsepower they have to use. None of 
>> those factors favor usage in a air cooled engine application.
>> They certainly have been tried for racing, and it doesn't seem to 
>> take long for the blades to bend, just from aerodynamic forces!. 
>> Usually, when fans have the exact same strength and stiffness there 
>> isn't much difference in weight, steel vs plastic. It is only when it 
>> is possible to compromise on stiffness that big weight reductions are 
>> possible... I really need a stiff fan for a design like this! modern 
>> turbo's would look exactly like mine do at the tips, the reason they 
>> don't is because of tip flutter from pressure... something I don't 
>> have to worry about as the pressures that this fans is supposed to run 
>> at are much lower, but still far higher than any "propeller"type 
>> design can do. I designed this fan to be grenade proof even if it is 
>> run up to 28" and has been spun up as high as 11000 rpm, just short of 
>> some OE Porsche tip speeds... and as I discovered recently, is 
>> probably way more output and pressure than any aircooled engine can 
>> really use. It seriously needs to be geared down a lot for most 
>> applications, which is part of what I was after, as lower tip speed is 
>> the most effective way to deal with inertia. Also, notice those huge 
>> scallops in the tips
>> of the fan- those scallops have a fairly sizable impact on the 
>> inertia of the fan, but doesn't change the weight very much- there's
>> also flow and efficiency reasons for those scallops being there, but 
>> my big reason for doing that was for inertia reduction.
>> Just in case any of you are curious, the level of effort required to 
>> accelerate my fan with a stock sized pulley seems to be identical
>> to accelerating the alternator with its pulley.
>> Kevin Nash
>> 63 Turbo EFI daily driver
>> http://www.vv.corvair.org/pipermail/virtualvairs/attachments/20180131/a3be854f/attachment.jpe
>> Matt Nall
>> Charleston, Oregon
>> http://tinyurl.com/The-Corvair-Patio
>> http://tinyurl.com/Matts-Tech-Pages
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