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ONEBADBUG
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Joined: January 27, 2004
Posts: 66
Location: SPOKANE, WA
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 Posted: Sat Jan 14, 2012 4:22 pm Post subject: |
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| Yes, the FI engines all had it. I wonder how much it helped? |
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rkeller
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Joined: February 15, 2007
Posts: 105
Location: Wake Forest, NC
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| Posted: Mon Jan 16, 2012 7:55 am Post subject: |
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| earthquake wrote: | I always wondered if some sort of inlet spike/volute [probably the wrong term] to direct air in to the fan would improve flow.
Casey |
Thinking about it more over the weekend, you are correct in both parts. The volute is on the discharge side and is a smooth curved funnel that decreases the speed of the air but increases it's force or pressure. The fan shroud or doghouse intentionally or unintentionally does this. The spikes a.k.a. inlet air vanes ," look at the trapezoidal shape of the fan blades in the previous photos" act as a sort of velocity stack; they are designed to direct the laminar flow of air and begin moving it towards the blades. There is some debate whether their benefit is cancelled out by the potential, at certain speeds, to create vortices but I think that is for testing to decide.
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Hophead
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Joined: January 03, 2005
Posts: 900
Location: Paradise,Ca
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| Posted: Wed Jan 18, 2012 7:32 pm Post subject: |
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In airfoil terminology your double airfoil is actually a single airfoil but the trailing edge has what they call "reflex" that is the upturn you speak of.
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36hplandspeedracer
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Joined: January 30, 2006
Posts: 684
Location: Mendon, Utah
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| Posted: Thu Jan 19, 2012 9:33 am Post subject: |
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RKeller, when I was in VW schools in the late sixties I was taught the holes in the back plate of the fan were to provide cooling for the generator. Late model fans do not have this feature because the generator mounting plate includes a deflector to direct air bounced off the case up and into the cooling holes in the back off the generator/alternator.
Am I wrong in this thinking?
I trust that info enough that when I installed a doghouse oil cooler and fan shroud on my 36er for better cooling, I took the late wider fan and had a machinist duplicate to cooling holes as shown in your photo since the wider fan is required for the wider doghouse fan shroud.
My 2c worth............
Burly |
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Jacks
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Joined: July 15, 2006
Posts: 840
Location: San Clemente, Ca.
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mark tucker
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Joined: April 08, 2009
Posts: 8499
Location: SHALIMAR ,FLORIDA
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| Posted: Fri Jan 20, 2012 8:40 am Post subject: |
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| 36hplandspeedracer wrote: | RKeller, when I was in VW schools in the late sixties I was taught the holes in the back plate of the fan were to provide cooling for the generator. Late model fans do not have this feature because the generator mounting plate includes a deflector to direct air bounced off the case up and into the cooling holes in the back off the generator/alternator.
Am I wrong in this thinking?
I trust that info enough that when I installed a doghouse oil cooler and fan shroud on my 36er for better cooling, I took the late wider fan and had a machinist duplicate to cooling holes as shown in your photo since the wider fan is required for the wider doghouse fan shroud.
My 2c worth............
Burly |
thats what I see from my perspective,gen cooling.there is a reason for everything, well almost. |
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rkeller
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Joined: February 15, 2007
Posts: 105
Location: Wake Forest, NC
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| Posted: Sat Jan 21, 2012 9:18 am Post subject: |
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Regarding the holes on the back plate of some stock fans. The Exploded diagram shows the back of the fan (solid part or with holes ) butting up against the inner fan cover which is solid and has no paths for air to travel to the generator or alternator. I can see how making the fan lighter by decreasing the mass (i.e. holes) would be a benefit but from an aerodynamic standpoint they are just going to create turbulence and are not able to pass air to the generator.
Still looking for contact info on the current mfg.
Have also looked into blower fan manufacturers here in the States but they require a $20,000 to 25,000 minimum order plus tooling costs or are otherwise not interested. Looks like stamping them ourselves out of high strength aluminum may be the most cost effective way to do it unless we can contact those who are manufacturing the stock fan currently to see if they would like the work. |
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36hplandspeedracer
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Joined: January 30, 2006
Posts: 684
Location: Mendon, Utah
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| Posted: Sat Jan 21, 2012 11:12 am Post subject: |
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| rkeller wrote: | Regarding the holes on the back plate of some stock fans. The Exploded diagram shows the back of the fan (solid part or with holes ) butting up against the inner fan cover which is solid and has no paths for air to travel to the generator or alternator. I can see how making the fan lighter by decreasing the mass (i.e. holes) would be a benefit but from an aerodynamic standpoint they are just going to create turbulence and are not able to pass air to the generator.
Still looking for contact info on the current mfg.
Have also looked into blower fan manufacturers here in the States but they require a $20,000 to 25,000 minimum order plus tooling costs or are otherwise not interested. Looks like stamping them ourselves out of high strength aluminum may be the most cost effective way to do it unless we can contact those who are manufacturing the stock fan currently to see if they would like the work. |
Rkeller, you are looking at a diagram of a "LATE" model fan. In that style of generator cooling, the air from the fan hit's the top of the engine case and bounces (or flows?) off the case and up into a vent located at the bottom of the rear generator mounting plate (#19 ) and the front generator mounting plate (#17 ) and up into the holes located a the back of the generator. Most folks with 12 Volt generators are not aware of this design feature and do not pay any attention to locating the vent at the bottom above the case(the back plate will mount in any one of four locations-Only with the vent at the bottom is it correctly mounted!) and accelerate failure of their generator(or alternator)!
The 36hp generator only has a single generator mounting plate (#17 )with no bottom vent, only the holes in the back of the generator. The holes in the early fans "are not to make it lighter", but to allow air to be drawn into the back of the generator for cooling. Very inportant! I would encourage you to add the holes if you are using a small diameter 6 or 12 Volt generator.
Burly |
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mark tucker
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Joined: April 08, 2009
Posts: 8499
Location: SHALIMAR ,FLORIDA
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| Posted: Sat Jan 21, 2012 11:17 am Post subject: |
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| mine has a vent for the alt. |
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Flavio
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Joined: May 14, 2008
Posts: 395
Location: Madeira Island, Portugal
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| Posted: Sat Jan 21, 2012 12:56 pm Post subject: |
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Very interesting thread.
Because there is any hole in the 36Hp plate (#17) I'm wondering how does the fan cools the generator....? |
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rkeller
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Joined: February 15, 2007
Posts: 105
Location: Wake Forest, NC
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| Posted: Sat Jan 21, 2012 5:09 pm Post subject: |
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Aluminum Alloy is certainly strong enough to allow for the holes. If the low pressure area a.k.a. vacuum side, is in front of the inlet side of the blades then it is conceivable that the openings could allow air to pass through the alternator from the higher pressure engine side to the air inlet vanes via this air passage your speaking of. Anyhow regardless which way the wind blows, the bottom line is a separate base plate with holes could certainly be an option.
I still don't see where this air passage is. There is a plate, as posted earlier and as seen on this diagram as item 11, that looks like it would block any air passage. Is it a race customization or was it stock?
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gimmesomeshelter
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Joined: May 08, 2004
Posts: 1112
Location: San Carlos, CA
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| Posted: Tue Feb 14, 2012 5:29 pm Post subject: |
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Rkeller-
Now that I'm gainfully employeed, I can start spending money on VW parts again! 
I was planning on sending my fan to Gene Berg to be welded, but now I'm wondering if I should wait for you to finish your research/prototyping. Do you have an ETA for the completion of your project?
Cheers,
Paul
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36hplandspeedracer
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Joined: January 30, 2006
Posts: 684
Location: Mendon, Utah
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| Posted: Tue Feb 14, 2012 5:44 pm Post subject: |
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I believe the small diamter 6V generator, which mounts to the big center hole in the 36hp mounting plate, has large air intakes cast into the rear generator bearing plate. I do not have one handy to check but that is what I recall. It is there that the air passing through the holes in the fan plate would enter the generator for cooling and exit through the generator brush holes.
"I think?". Other opinions are welcome!
Burly |
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rkeller
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Joined: February 15, 2007
Posts: 105
Location: Wake Forest, NC
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| Posted: Tue Feb 14, 2012 5:55 pm Post subject: |
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| 36hplandspeedracer wrote: | I believe the small diamter 6V generator, which mounts to the big center hole in the 36hp mounting plate, has large air intakes cast into the rear generator bearing plate. I do not have one handy to check but that is what I recall. It is there that the air passing through the holes in the fan plate would enter the generator for cooling and exit through the generator brush holes.
"I think?". Other opinions are welcome!
Burly |
The engine compartment is higher pressure than in-front of the blades. The path for the air is as you stated but the flow would be the other way, from the engine compartment to the low pressure suction side of the fan through the generator, the holes then through the blades and out. |
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36hplandspeedracer
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Joined: January 30, 2006
Posts: 684
Location: Mendon, Utah
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| Posted: Tue Feb 14, 2012 6:06 pm Post subject: |
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Sounds good to me and still acheives the desired goal of having cooling air flowing through the gernator. Thanx..............
Burly |
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mark tucker
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Joined: April 08, 2009
Posts: 8499
Location: SHALIMAR ,FLORIDA
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| Posted: Fri Feb 17, 2012 12:41 am Post subject: |
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| any body ever put a type 3 or porsche style aluminum fan on a shroud like these??althou they would work best with a stator. |
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Joost
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Joined: December 16, 2011
Posts: 19
Location: Holland
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gimmesomeshelter
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Joined: May 08, 2004
Posts: 1112
Location: San Carlos, CA
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| Posted: Mon Feb 27, 2012 8:19 am Post subject: |
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Hello-
Too bad they don't post any data comparing their fan to a stock one.
Cheers,
Paul
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mark tucker
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Joined: April 08, 2009
Posts: 8499
Location: SHALIMAR ,FLORIDA
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| Posted: Mon Feb 27, 2012 5:45 pm Post subject: |
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| how much do the stock ones put out? and is there a standard pressure there tested at? |
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Jacks
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Joined: July 15, 2006
Posts: 840
Location: San Clemente, Ca.
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| Posted: Mon Feb 27, 2012 11:24 pm Post subject: |
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| It's measured in CFM. I'll post data for 356 tomorrow. |
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