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Re: NashFan for Racing?
Posted by: vairmech ()
Date: September 05, 2021 04:48PM

63turbo Wrote:
-------------------------------------------------------
Snip
I do have a fix coming for the sudden tension swap caused belt tossing problem, and really ought to banish that problem once and for all. I will post on it when finished!
>>>>>>>>>>>>>>>>>>>>>>>

Kevin, email me about what you are working on.

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

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Re: NashFan for Racing?
Posted by: 63turbo ()
Date: September 05, 2021 05:46PM

PM sent!

------------------------------------

Kevin Nash
Friday Harbor Washington
63 Spyder, Daily driver, EFI read about my project here: [corvaircenter.com]
first test start on EFI here:[www.youtube.com]
first official EFI boost test here:[www.youtube.com]
My new fan! [corvaircenter.com]
engine less 62 Spyder
Canadian 64 Monza Parts car
Test Start#2 [www.youtube.com]



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Re: NashFan for Racing?
Posted by: vairmech ()
Date: September 06, 2021 05:03AM

email me about what you are working on.
>>>>>>>>>>>>>>>>>>

63turbo Wrote:
-------------------------------------------------------
> PM sent!
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Hmmm, email or PM? LOL, not the same!

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

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Re: NashFan for Racing?
Posted by: 63turbo ()
Date: October 11, 2021 07:20PM

Heres some interesting info regarding airflow and hp consumption for a stock mag fan spinning at 1.2:1 vs a cut down fan using the stock pulley ratio:


The stock corvair fans dont follow the fan laws very well, in terms of predicting pressure and flow, but interestingly enough, predict hp consumption perfectly.
heres an example of how this works (or not) with the mag fan.

According to GM data, the mag fan on a 140 will produce 1510 cfm at 8.4" of water
at 4000 engine rpm (6320 fan rpm) and at 2000 engine rpm, 750 cfm at 2.3" of water
and at 1000 engine rpm, 375 cfm and .58" of water. These numbers are picked off a graph from "GM RESTRICTED STOCK ENGINE TEST", 1965 HO-6.

If the pressure and flow at 1000 engine rpm are extrapolated to 4000 engine rpm, we should be able to predict the pressure and flow there. Since this is 4x the rpm, then the flow should be 4X the flow at 1000, so 4X 375=1500 and that checks out pretty well. However, to predict the pressure, it is the square of the flow change, so we multiply .58 by 16 and get 9.28", which is way off from the measured pressure!. lets go the other way, predict the pressure from 4k, and divide by 16 instead... in which case 8.4/16= .525" which is again off low. I checked the pressures with my own measured pressures with my mag fan at these rpms and found that the measured pressure numbers I got agree with GM numbers quite well. What's interesting is to go to higher rpms, now everything gets WAY off!! at 5250 the most pressure I ever saw was 11.5"....The fan laws would predict 16"!!

All this being said, since it is or should be clear that the fan isnt moving air well at high rpms, basically maxed out at 5250, wouldn't it make some sense to try a different pulley ratio if it is desired to run at higher engine rpms? or would it work better to make the fan smaller and spin it faster, as is commonly done for racing? We can use the fan laws to figure that out!! Here's a link to try this yourself [www.engineeringtoolbox.com]

A summary of a fan law comparative test that I did is shown below, and is based on either a stock fan that is slowed down enough that at 7000 engine rpm, the fan will be spinning at a speed "as though" it was at or close to the practical maxed out flow seen at 5250 for the engine with the stock pulley ratio, and a cut down fan that is using the stock pulley ratio but going to 7000 rpm. The results are really interesting! For this comparison, fan pulley ratio of 1.2:1 is used, because this is as close to the above criteria as can be done with a variable ratio pulley, and results in a peak fan speed of 8400 rpm. Results:

1.2:1 stock mag fan @8400 fan rpm

flow= 1732
hp= 18.7
pressure=11.8"

1.58:1 mag fan cut down to 10" @8400 rpm

flow=1233 cfm
hp=10.6
pressure=9.41"

now extrapolate the above to 7000 engine rpm, which is 11060 for fan:

flow=1623cfm
hp=24.2 (!)
pressure=16.3"

In actual dyno testing, with a cut down fan at 7000 rpm with lower shrouds off,
18 hp seems to be more like it, so belt slippage is probably occurring... if its not using the power, it is not spinning the fan! To estimate the fans real world output, I used this last data point, and plugged in lower fan rpms, until the predicted hp matched reality,
and since the stock fan was predicted to use 18.7 hp, I reduced the cut down fan speed until it used only 18.7hp to "equalize" these 2 set-ups. The fan rpm that used only 18.7hp without slippage turned out to be 10155 rpm.

flow= 1491 cfm
hp=18.7
pressure= 13.8"

From the above, absent any belt slippage, the "small fan spinning faster" consumes 29% more horsepower and flows 6.3% less air than the "big fan spinning more slowly", and when slippage is factored in by equalizing the hp, the smaller fan is only putting out 1491 cfm and is down 13.9% compared to the big fan.

------------------------------------

Kevin Nash
Friday Harbor Washington
63 Spyder, Daily driver, EFI read about my project here: [corvaircenter.com]
first test start on EFI here:[www.youtube.com]
first official EFI boost test here:[www.youtube.com]
My new fan! [corvaircenter.com]
engine less 62 Spyder
Canadian 64 Monza Parts car
Test Start#2 [www.youtube.com]



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Re: NashFan for Racing?
Posted by: zarfnober ()
Date: October 11, 2021 08:05PM

Kevin, you’re making my head spin in reverse rotation.

You should be given a medal for what you’re doing here, looking forward to the new fans!

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Re: NashFan for Racing?
Posted by: JimBrandberg ()
Date: October 12, 2021 05:08AM

The video that was on here last month showing a fan belt in actual road use is interesting.

Jim Brandberg
Isanti, MN
CorvairRepair.com



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Re: NashFan for Racing?
Posted by: 63turbo ()
Date: October 13, 2021 08:10PM

Here's another video on the same subject: [www.youtube.com]

Its pretty clear that a radically improved guiding system is whats needed.
The mule drive on our cars as is, is way too sensitive to tension, and alignment.

I was encouraged watching the video that was posted not too long ago, and the one by Kevin Wilson (in the link above) as the widget I'm working on would appear to kill the problem dead in its tracks. Both videos show were the belt is most likely to come off, (as it enters the idler pulley) so a REALLY good guide there that does NOT depend on tension to feed the belt into the idler correctly in all cases
loose or not aluminum pulley or not, to banish the problem. I'm 90% done with it and will post it here when ready... it is trick as hell!!smileys with beer

------------------------------------

Kevin Nash
Friday Harbor Washington
63 Spyder, Daily driver, EFI read about my project here: [corvaircenter.com]
first test start on EFI here:[www.youtube.com]
first official EFI boost test here:[www.youtube.com]
My new fan! [corvaircenter.com]
engine less 62 Spyder
Canadian 64 Monza Parts car
Test Start#2 [www.youtube.com]



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Re: NashFan for Racing?
Posted by: toms73novass ()
Date: October 14, 2021 03:10AM

63turbo Wrote:
-------------------------------------------------------
I'm 90% done with it and will post it here when ready... it is trick as hell!!smileys with beer

Looking forward to this! smileys with beer

-Tom


63' Monza Spyder Convertable (in process) MY Build Thread
62' Wagon rebuild MY Build Thread
65' Monza MY Build Thread
73' NovaSS 454 Big block (Sold)
86' BMW 325es
67' UltraVan 211 "Violet"
NFCC, UMCC
Grand Island, NY

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Re: NashFan for Racing?
Posted by: Jonathan Knapp ()
Date: October 15, 2021 09:20PM

Hi Kevin,

Wouldn't leakage in the top shroud, front and rear cylinder shrouds, and around the oil cooler cause pressure to drop without a decrease in the amount of air flowing into the fan?

Jonathan Knapp
Wheeling, WV
'66 Corsa Autocrosser

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Re: NashFan for Racing?
Posted by: 63turbo ()
Date: October 16, 2021 06:12AM

Jonathan Knapp Wrote:
-------------------------------------------------------
> Hi Kevin,
>
> Wouldn't leakage in the top shroud, front and rear cylinder shrouds, and around the oil cooler cause pressure to drop without a decrease in the amount of air flowing into the fan?

If airflow is being measured at the intake, and static pressure is being read in the top shroud, yes. A great way to improve the cooling on any Corvair is to find those leaks and plug them. If the "leak" is the fan to shroud gap though, this affects how much airflow is actually read, as less air will actually go in vs what the fan is theoretically capable of doing.

------------------------------------

Kevin Nash
Friday Harbor Washington
63 Spyder, Daily driver, EFI read about my project here: [corvaircenter.com]
first test start on EFI here:[www.youtube.com]
first official EFI boost test here:[www.youtube.com]
My new fan! [corvaircenter.com]
engine less 62 Spyder
Canadian 64 Monza Parts car
Test Start#2 [www.youtube.com]



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Re: NashFan for Racing?
Posted by: Jonathan Knapp ()
Date: October 16, 2021 09:57PM

Kevin,

Is there an optimal fan to top shroud clearance amount? Or is the closer-the-better the right answer?

Jonathan Knapp
Wheeling, WV
'66 Corsa Autocrosser

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Re: NashFan for Racing?
Posted by: 63turbo ()
Date: October 17, 2021 06:56AM

Jonathan Knapp Wrote:
-------------------------------------------------------
> Kevin,
>
> Is there an optimal fan to top shroud clearance amount? Or is the closer-the-better the right answer?

Basically, the tighter the clearance the better, but the point of diminishing returns is when the gap is 5-6% of the blade height. For a mag fan, this would be
approximately 1/16".

------------------------------------

Kevin Nash
Friday Harbor Washington
63 Spyder, Daily driver, EFI read about my project here: [corvaircenter.com]
first test start on EFI here:[www.youtube.com]
first official EFI boost test here:[www.youtube.com]
My new fan! [corvaircenter.com]
engine less 62 Spyder
Canadian 64 Monza Parts car
Test Start#2 [www.youtube.com]



Options: ReplyQuote
Re: NashFan for Racing?
Posted by: Skizz ()
Date: October 17, 2021 10:54AM

Saw my first one installed on a car at Maggie Valley.

64 Monza Vert
64 Spyder Vert
2002 Chev 1500
1996 Impalla SS
Eastern NC

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Re: NashFan for Racing?
Date: October 17, 2021 11:51AM

Has anyone ever tried a serpentine belt (Polly-v) for our mule drive? I’m considering doing it for my build. An 8-rib can carry a tremendous load. Even a 6-rib carries 40+ HP continuous on marine applications.

---------------------------------------------------------------------------------------------
You're unique, just like everyone else...

Johnny B
Central WI

Wife's '68, 3.0L, twin-screw compressor and fuel injected in the works...

Project Pressurized Pancake


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Re: NashFan for Racing?
Posted by: 63turbo ()
Date: October 17, 2021 03:46PM

I dont know of anyone that has done that with a corvair/mule drive type set-up, but the shock loading would have to be tremendous, as zero slippage is allowed with those. I've heard of this being done on vw's and has resulted in broken fans!

------------------------------------

Kevin Nash
Friday Harbor Washington
63 Spyder, Daily driver, EFI read about my project here: [corvaircenter.com]
first test start on EFI here:[www.youtube.com]
first official EFI boost test here:[www.youtube.com]
My new fan! [corvaircenter.com]
engine less 62 Spyder
Canadian 64 Monza Parts car
Test Start#2 [www.youtube.com]



Options: ReplyQuote
Re: NashFan for Racing?
Date: October 18, 2021 07:59AM

63turbo Wrote:
-------------------------------------------------------
> I dont know of anyone that has done that with a corvair/mule drive type set-up, but the shock loading would have to be tremendous, as zero slippage is allowed with those. I've heard of this being done on vw's and has resulted in broken fans!


I’ve got experience driving screw chargers with these, but there’s an active tensioner involved. Usually <1.5% slip, but certainly not zero.

I’ll mock one up when I longblock the PressurizedPancake.

---------------------------------------------------------------------------------------------
You're unique, just like everyone else...

Johnny B
Central WI

Wife's '68, 3.0L, twin-screw compressor and fuel injected in the works...

Project Pressurized Pancake


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