Idea for Horizontal Fan

[HawgRyder]

It occured to me over the weekend (too much thinking time) that perhaps the answer to the horizontal (top of the engine) type fan that so many ppl want could be a different drive.
We have seen the original with gear boxes and aftermarket drives with both gears and belts.
I wonder if a Hydraulic drive might not work?
A simple vane-type pump on the end of the crank with a similar motor in vertical position to drive the fan would work.
It would make for a very simple install...and be a lot easier to design.
I have probably over looked something..but this is just a feeler to see if one of you guys can tell me why it would not work.
Bob

[kach22i]

I think last time we all looked into an "electric drive" the HP numbers were not small. It takes a lot of power to move that much air.

Maybe someone could look up that old thread and compare it to Hydraulic drive requirements.

[DavErb]

I can't answer directly as to a Porsche application but I have a lot of experience with hydraulic drive components since I work in the golf course industry and hydraulic units are the mainstay of that industry. I would recommend against going this route. Hydraulic drives have some advantages in that they are very flexible so they can accomodate odd layouts that would otherwise be difficult to line up shafts and/or pully systems. They are also very good at transmitting a lot of torque in a easily controlled fashion. The main disadvantage is that they are inefficient and create a lot of heat in their operation. Realize that you are using engine HP to drive a pump (with its associated inefficiencies) which pressurizes hydraulic oil to high PSI. The oil then has to move through a tube, either flex or hard both of which have problems, to a hydraulic motor (more inefficiency) and then back through a return tube. Every component in the chain is dumping heat into the local environment all of which translates as lost HP. You will have aslo created a number of possible failure points in the car .

I'd go with some sort of jackshaft or belt arrangement long before I used hydraulic drives

[HawgRyder]

Dave:
Good point about the heat.
This is the reason I asked for input on the idea.
If an engineer could get involved with numbers on heat generation in a 1:1 type of pump/motor situation, it would be helpful.
I was thinking in these lines of same crank/fan speed if possible (to keep heat down), or if not enough fan speed, then perhaps a 1:2 app to push more air.
I know that as the HP requirement goes up so does the heat generated.
And for the complexity of the install...would not 1 pump, 1 motor, and 2 hoses not be lighter and mechanically easier than gearboxes and belts?
I am thinking of the steering on boats (hynautic steering) for simplicity.
You turn the wheel and the rudder turns in sync.
I realize the speed is greater, but the principal is the same.
Bob

[neilca]

Bob,

I hate to do this to you but, check out this site
http://www.parker.com/hyd/fandrive/Fan_Drive_Brochure_030805.pdf

I find this to be very interesting....

neil

[DavErb]

Well in the case of the boat rudder you are playing to the strengths of hydraulic. Hydraulics are easy to route and they are great for torque transmission, good example being the brakes in your car. Flow is not constant so heat tends not to be an issue

However in a pump to motor circuit you have constant flow. The smaller the pipes and the higher the pressure the greater the flow friction as it passes through the pipes. The motor portion that drives the fan would be about the size of a fist and you'd need to come up with a sturdy mount for it so that the torque reaction doesn't twist the motor free. You *really* don't want to use the hoses as anti torgue devices. Found that one out the hard way
Then theres the problem of driving and mounting the pump portion. You could do a simple mount by using the old fan postion or the AC compressor position but then you're halfway to a belt drive. You could possibly do a direct drive off the left side cam drive but that would be putting an undesigned for load on the cam chain and tensioners. From a hazy recall of the room available at the pully end of the crankshaft I think you'd have a hard time fitting a decent sized pump off the end of the crankshaft.

Anyway I don't want to sound too negative here. Probably a big chunk of us ended up with these cars becuase we like messing around with mechanisms. It can be done if you want it and I hope you enjoy the journey

[svandamme]

how did they do it on 935's??

didn't they run it from top of the same crank gear, that drives the oil pump in the bottom??


how difficult would it be to mod an aluminum case so a gear can run from there???

[MattAlpha]

The way large ships' rudders are controlled is through hydraulics. The difference is that their pump/s are running at a constant pressure all the time (or the pumps would be even less inefficient). When the "wheel" on the helm is turned, that motion is then sent to a swash plate that controls the amount of hydraulic fluid needed to turn the rudder in the direction and magnitude indicated.

Its more complicated than you may think, and it is wasteful/ineffecient. Hydraulics are used on ships because of the strength properties. I would be more inclined to try this with belts and an automatic gearbox type of arrangement.

Just my 2 cents,
Matt

[HawgRyder]

Neil:...very interesting..thanks
Stijn: ..that shaft is horizontal..so you still need gearboxes, which is how the factory did it I believe.
Matt: .. I know about hydraulic steering...but what I was refering to is Hynautic steering...the wheel is the pump...the force is applied by the pilot...no motors..no reservoir...just oil and tubing...very low pressure.
The search continues...LOL
Bob

[svandamme]

Originally posted by HawgRyder

Stijn: ..that shaft is horizontal..so you still need gearboxes, which is how the factory did it I believe.

sure, but not impossible to find no?
the hard part is getting the drive out of the crank case

[Wayne 962]

This has been discussed many times. The problem is that this is almost a solution looking for a problem. The front-mounted air fan works very well, and does a very good job at cooling the engine. Adding the horizontal fan costs thousands of dollars, with very little tangible benefit. Off the top of my head, I cannot think of any non-turbo six-cylinder race cars that used a flat fan assembly. The 1973 / 1974 RSR used the regular vertical fan, and had no significant cooling issues, as far as I know.

Yes, this would be cool, but it's like the 3.0L MFI system - just not really very practical considering the cost and miniscule performance gains.

-Wayne

[slodave]

I have no useful input, but here is an RSR engine pic


I thought that the fan was smaller than the fan on my 3.2, but the shroud is a bit different (not just being fiberglass).

Dave

[bigchillcar]

would someone post a pic of that 917 motor that wayne had on display a year or so back? i think that's the last pic i saw of a porsche racing engine with the fan on top?

[slodave]

Originally posted by bigchillcar
would someone post a pic of that 917 motor that wayne had on display a year or so back? i think that's the last pic i saw of a porsche racing engine with the fan on top?

Not the greatest, but here are 3 for you:


Another:


Dave

[bigchillcar]

fast work..slodave.. thanks! so..just how is this fan driven exactly? i know little of the famous little motor's drive details..

[bigchillcar]

isn't the long block essentially a 12-cylinder, made by putting two 6-cylinder motors somehow inline? or was i smokin' crack the day i thought i read that?? is it driven by some sort of vertical shaft, transferred from the horizontal crank, maybe drive-reduced by a *type* of planetary gear translation? if belt-driven..i don't see where..

[slodave]

I remember some sort of gear drive. I think it had two 90° gear boxes, linked with some drive shafts.

[bigchillcar]

no way..wag on my part. i didn't stay at a holiday inn express last night..but i did watch two episodes of star trek (original series) this evening..and i find this idea, if not fascinating..somehow, interesting..

[slodave]

OK, maybe I was smoking crack. Here's a split case:


Dave

[bigchillcar]

can't tell if it's drive-reduced or not..i'm no engineer..but it appears like it could be turning the fan in ring & pinion fashion at crank speed?