<VV> My new experimental fan

kevin nash wrokit at hotmail.com
Sun Nov 12 13:50:55 EST 2017

Hugo- yes, it is heavier, and it certainly would have been nice for it to be closer to the stock magnesium fan weight, however, compared to the earlier steel fans, this prototype is still a very light fan- those things weighed something like 4.5 lbs (!). All of the stock fans have extremely poor efficiency, resulting in both

less than ideal output and way too much horsepower usage.... all of them use between 8 and 9 horsepower at 4000 rpm, when they ought to be using less than half of that. It is simply impossible for the stock fans

to get to what is considered a normal, expected efficiency of around 60% because of the open shroud

design- air is flung out in all directions simultaneously, and continuously, basically causing all of the blades

to use an excessive amount of horsepower and be unusually sensitive to flow blockages, vs the more normal blower/scroll arrangement where only a tiny fraction of the blades are open to the exit at any given

moment. One of the seriously attractive features of a backwards curving fan is that they experience a very

small, efficiency drop when run open... but this claim HAS to be tested, and tested again... If I don't see

a big enough efficiency gain, then the little bit too heavy weight of this particular prototype will be the least

of my problems.

    Assuming that the efficiency is more like what is expected for a fan like this (60%+), and the output

is what I expect, and the performance can be verified by other competent testers, then I can worry more

about the method of manufacture and material and get the weight down to more like what it should.

If it was made from Magnesium, it would weigh roughly 11 ounces, and printed from composite it would

be around 7-8 ounces, but will require significant re-design for stiffness. I don't want to do that until the

design is thoroughly proven.

    Kevin Nash

From: Hugo Miller <Hugo at aruncoaches.co.uk>
Sent: Sunday, November 12, 2017 9:04 AM
To: kevin nash
Subject: Re: <VV> My new experimental fan

It’s the weight – or rather the rotating mass – that would concern me most.

From: kevin nash
Sent: Saturday, November 11, 2017 8:58 PM
To: Hugo Miller ; virtualvairs at corvair.org
Subject: Re: <VV> My new experimental fan

Thanks Hugo!

This particular fan weighs nearly exactly 2lbs. If the shop that machined it had been able to cut it right exactly to my CAD model, it would have weighed 1.4 lbs, compared to the stock Magnesium fan weight of 1.2lbs. While it would have been nice for the fan to have been lighter, I'm certainly not complaining about the weight... this is a prototype, and fan weight is not a concern for me as this time. The output and efficiency are though and this fan is perfect for testing those attributes.

For what it is worth, if this fan had been made exactly to the model, but made from magnesium, it would

weigh around 11 ounces !

Kevin Nash

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