Fan conversion rambling

NextGen · Post by **NextGen** » Tue Jul 30, 2002 11:22 pm

http://www.ismi.net/riecherttuning/coolingt4.htm

Guys go to the site above for the horizontal fan set up like the Corvair. Got to be a horror on the belt with that 90 degree turn, but it sure looks mean!!
Joe

Rolf · Post by **Rolf** » Tue Jul 30, 2002 11:46 pm

My brother got such a horizontal fan setup on a 2,0L type 4 in his Porsche Spyder Replica and it worked OK untill a little while ago when he ran into some problems. It started to throw of the fan belt above 5000 RPM's with out anything been altered or changed. Replacing the fan belt only made it all worse and we rechecked every thing and one of the small fan belt pulleys had a bad bearing and we had bought some bad fanbelts that would snap the cores inside the belt after only a few miles. Replaced the bearing, got some otheer fan belts from a different supplier and it runs very well again. Well I must admit tha the belts have to be replaced more often than a normal upright conversion or stock cooling system, but there's not room for any other cooling steups in this car. To get the car roadlegal we have to use a shorted VW floorpan and therfore not able to make a midengine car.

Rolf

[This message has been edited by Rolf (edited 07-30-2002).]

Dave_Darling · Post by **Dave_Darling** » Wed Jul 31, 2002 9:16 am

The engine lid is something (not much, but somewhat) of a high-pressure area. Better to vent to a low-pressure area if possible.

I've seen photos of "tuft tests" that show a layer of air running forward along the rear deck lid at speed, and going into the engine bay. Probably not great for downforce, but it helps the cooling issue a little bit.

--DD

------------------
1974 VW-Porsche 914 2.0 (Type IV powered!)

Pelican Parts' 914 Tech Geek http://www.pelicanparts.com

ray greenwood · Post by **ray greenwood** » Wed Jul 31, 2002 12:46 pm

Tom Perso. Great idea for the clutch. I was kinda lurking on this thread...and thinking along those lines. Think about this. We all know how a torque converter works right?....Does anyone on this thread know how the rear differential in an Audi quatro works? Some of them at least...depending on what generation...work along theses lines: A shaft with thin meatal plates welded to it passes into a chamber mounted solidly to the frame. This is the power shaft. Surounding that shaft and its plates, inside the chamber...is another chamber with ring shaped plates, mirroring the plates on the power shaft. The ring plates have a hole in the middle so they do not touch the other shaft. That chamber with the ring plates has a shaft atteched to the end exiting the mounted chamber. That is the driven shaft. The plates are very close together and surround by a very viscous synthetic oil. The gaps between each plate are very close...like maybe .010...I'm guessing. The power shaft turns...friction is transfered to the oil. It heats...but not much...expands...and starts transfering friction to the driven plates, because it acts like a solid. No contact at all by metal. It is RPM and torque sensitive and has little lag. The ratio of transfer is dependant upon the closeness of the plates and the total surface area between the two. It is in effect a viscous coupling.
So....the atlernator shaft could go into ...say...a small 3-4" diameter box with a bearing on each end, with a stack of plates interleaved. One set welded to the shaft driving the fan...the other to the alternator shaft. Output speed would be relative to rpm. You would have to adjust ratio of air volume to speed, by the size of the fan from the beginning. Rate of slip would be governed by the closeness and surface area of the plates. It should work. Just some thoughts. Ray

Bobby74 · Post by **Bobby74** » Wed Jul 31, 2002 2:06 pm

I used to work for Beaverton Service Center, a lawnmover shop. The John Deer mowers use an electric clutch for the 42" blade!! This clutch does fail when it gets clogged to death, and results in a SCRRRREEECH... It could be used for this application, the motor is over 12HP.

The automatic (yes they do have them) transmissions on the MTD mowers and others have Hydostatic transmission drives (what Ray was explaining reguarding Audi's). These transmissions are faily compact and use a viariable drive where you can move a lever from 1 - 12 speed, while moving

I use to take these up on 2 wheels through the parking lot "testing" them. Talk about turning radius... You could also use he hydo clutches found on larger trucks/RV/etc. they have to turn a heavy duty large diameter fan, metal also.

Mueller · Post by **Mueller** » Wed Jul 31, 2002 2:29 pm

Ray,

Toyota now has an electric clutch strong enough for the superchargers that come on some of thier vehicles, if this can be regulated on and off depending on load and temperature, that would be pretty slick in my opinion. Heck, even a standard A/C electric clutch might work.

I know that the easiest way to adapt a new fan would be to mimic the way the 911 fan is run (vertical), but I really like the idea of the horizontal fan like the Corvair or better yet the 917 !!!!

I know that Porsche did make a few of these for six cylinder cars:

I'm just not sure how much extra power the 90° drive would take. Also finding bevel gears that'll work and building the box might get expensive.

------------------
Mike Mueller
'75 914 2.0

PapaG · Post by **PapaG** » Wed Jul 31, 2002 3:27 pm

A new VC for my Syncro Vanagon is around $800 us. I don't know what a VC for a Audi costs.

Chris_914 · Post by **Chris_914** » Wed Jul 31, 2002 4:21 pm

Now I really like the 90° drive. Might be a bit big but some fabrication using spider gears from a differencial, couple of flanged bearings, and a coulple of axle stubs. Throw on an A/C fan clutch activated by a thermostatic switch.

------------------
Chris
75 914 2.0L
72 1302s Super Beetle
71 Squareback
97 K2 Golf

Bobby74 · Post by **Bobby74** » Wed Jul 31, 2002 7:47 pm

That drive is a much better idea, but may have a bit too much drag.. So just make more power

Corvairs use to have trouble holding a belt, my dad use to loose them all the time when he threw it sideways. P.s. Corvairs will not roll, he tried on sand at over 60-80mph and it just slid... Swingaxle even, no camber compensator.

Back to the point, I would use a KISS system with as few parts as possible, and are most availible (IE Junk yard if you have to). I like the A/C or supercharger clutch idea, and it would keep it vertical.

tuna · Post by **tuna** » Wed Jul 31, 2002 9:12 pm

A few people have mentioned here the Corvair belts and their problem with the 90 degree turn. This reminded me of an email discussion I had with Joe of the West. It seems that the belt tossing has a solution. Here's what he wrote:

<QUOTE>Tom,
The belt throwing problem on the Chevrolet Corvair was rectified some time back by a Chevy Agency in Conn.(Zink Chevrolet, I think) They sold custom bodied Corvairs and also did some racing. The problem is that the belt elongates in proportion to the amount it
streches from the resistance (load) pulley to the power source (crank pulley).
The greater the length of the belt, the longer it streches.
The elongation happens on the right side on the Chev Corvair (idler pulley side) and on the left side on the Reichert set up since VW's rotates clockwise.
The elongated slack side of the belt rises out of the "fixed" pulley groove and the belt is thrown. A new belt is a temporary fix until the fiber plies start to separate. The lighter magnesium fan on the Corvair reduced the fan throwing episodes, but in time as the belt got older, it would start throwing
again.
A simple spring loaded idler pulley will temporarily "follow" the belt as the
belt elongates.and retains the belt in the pulley groove.
I personally tried it on my Corvair Turbo 150 rail in 1970 after I heard about it.
Very simple fix. Never threw a belt after that. I'm not sure what Reichert is doing
or has done about the problem.
Joe
Oregon Peformance Products http://www.spiretech.com/~opshroud
</QUOTE>

Bugfuel · Post by **Bugfuel** » Wed Jul 31, 2002 9:51 pm

I've had discussions about this too, maybe even with Joe because it all sounds too familiar. The tensioner doesn't even have to be spring loaded I think, just a fixed roller at a well thought out location. Simpler to fabricate. The roller would not allow the belt to "lift off" the groove, and it would try to lift off at only a narrow section of the pulley, not all the way around (like he said, the slack occurs only on left OR right side of the pulley, depending on direction of rotation)

I have even seen solid "pins" fitted for this purpose, but I don't think it's a long lasting solution as the belt would seriously rub against the pin.. has to be a roller type of solution. Like a wide bearing that the belt back rides against. The pin version was found on a race engine that only sees short bursts at a time.. more a failsafe than continuous contact with the pin.

I've seen something like this (roller) in real life, on race engines. Even upright belts with no 90 degree turns

(and yes, also in corvair type systems)
It's been so long however that I don't remmeber any details. And these were mainly type 1 engines, only one type 4. The race T4 was the one with 90 degree turn.. top mounted fan... corvair type.. yes it kept throwing belts at high revs until a roller was added

Jan

WipEout · Post by **WipEout** » Wed Jul 31, 2002 11:37 pm

Just a thought: www.aircooled.net has a serpentine belt system for T-1s. Would a third "tensioning" pulley like that be a viable solution for the stretching fan-belt in a corvair style system? here's the link to aircooled's picture:
http://www.aircooled.net/new-bin/viewpr ... 0280883474

DAVID MANN

ray greenwood · Post by **ray greenwood** » Thu Aug 01, 2002 5:54 am

Mueller...aaah...the 917 was an interesting work of art wasn't it? So thinking horizontal fan, but wanting to get away from the wierd pulley system, how about this: a small high speed skew bevel power take off (90 degree) to drive the fan itself. Horizontal shaft...say about 12" long running to a pulley in line with the crank pulley in a bracket with bearing. Small power take offs in every conceivable configuration and size are available pretty easily these days. Having an upper and lower in-line pulley would allow two different chances to affect the ratio of the shaft speed, or the PTO could be production or reduction gearing...but that would take up more space than 1:1 gearing. If you could run straight cut gears, you would not need hypoid oil and could run an oil line to it with a return to the crankcase. I love this thread! Ray

Dave_Darling · Post by **Dave_Darling** » Thu Aug 01, 2002 6:26 am

Actually, that was a 935 (I think) fan setup that Mike showed. Some of them had horizontal fans, I think because it cooled better.

I'm just not sure how much extra power the 90° drive would take.

If you believe the numbers thrown around on the Racing rennlist e-mail list a while back, quite a bit. Like the 12-25 range for the one pictured, and more for the 917 one!!

--DD

PS--
...Corvairs will not roll, he tried on sand at over 60-80mph and it just slid... Swingaxle even, no camber compensator.

If he had tried it where he actually had traction, as opposed to over sand, I think you'd've found that the car could roll.

------------------
1974 VW-Porsche 914 2.0 (Type IV powered!)

Pelican Parts' 914 Tech Geek http://www.pelicanparts.com

Griznant · Post by **Griznant** » Thu Aug 01, 2002 6:42 am

I remember watching a Porsche racing legends video awhile back and I remember some comments on the horizontal fan setup.

I think it was the 917 which had problems with the fan hub shearing off at high rpm or something which would send the fan shooting up through the bodywork. I'll have to see if I can dig this out as I remember it was a big issue for awhile with someone being either hurt or killed by a flying fan.

Later,

G