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Author Topic: electric fans  (Read 2104 times)
Tin Lizzy
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« on: April 24, 2007, 09:08:49 AM »

Hi everyone,
Has anyone converted over to electric fans for cooling?
I would love to get rid of blowers etc.
thanks
Harry
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Tin Lizzy
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« Reply #1 on: April 24, 2007, 09:35:11 AM »

don't do it ... Many have tried a failed. Tim Strommen did this, read his comments http://www.busconversions.com/bbs/index.php?topic=3880.30
Ron
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Lee Bradley
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« Reply #2 on: April 24, 2007, 09:35:39 AM »

Everyone knows this can't be done.

Although .... a couple of years ago, at Rickreall, OR, I saw a MCI freighter with electric fans cooling a 8V92. The owner said it worked great.
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Hartley
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« Reply #3 on: April 24, 2007, 10:34:48 AM »

Oh,,,, Don't EVEN start with that nonsense again... Just run what you have and fix the existing system. It works!
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kyle4501
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« Reply #4 on: April 24, 2007, 10:55:21 AM »

To cool the engine requires air flow over the radiators. To get this air flow, you must move air & that requires HP! Look at the size of belt & gearbox driving the blowers. When under max load, the blowers can require over 30 HP. That's a BIG motor & a BIGGER current draw!

Yes you can go electric, but you need to answer the question 'Why did the manufacturer go to the trouble to put in blowers if an electric fan would have worked better?'

Elec fans are usefull in some applications, especially when the ram air effect is being used to push air thru the radiator while driving down the road.


Hey Lee, any pictures of that guy's setup? or more details?

DrDave is correct in that fixing your current system will be most cost effective solution.
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Lee Bradley
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« Reply #5 on: April 24, 2007, 01:26:40 PM »

I will check on photos but I don't think I have any.

The radiator (single) was location down on the driver's side of the engine with two big electric motors turning 16" or 18" fans. The fans where fully enclosed with a divider between the upper and lower fans so the fans could run independently without pulling air through the fan not running. The engine had two thermal switches set 5 or 10 degrees apart so the fans came on at different times. The fans could also be switched on from the driver's position. The radiator looked to be about 24" by 48" and was mounted facing almost for and aft, so it may have picked up some ram air.
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Tim Strommen
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« Reply #6 on: May 01, 2007, 12:30:52 AM »

Hey Tin Lizzy,

  You can determine if your system can be augmented or subsituted with an electric fan if you do a bit of research.  The big thing you need to determine the actual heat rejection for the engine to the cooling system.  After that, you need to know the ambient air temperature of the intended use environment.  That will tell you how much air of that temperature will need to come in contact with your exchanger surface in a certain ammount of time.  Depending on the configuration of your radiator, you may need more air over less surface area per minute than other configurations.  Once you know what the CFM is, you'll need to figure out the air restriction of the radiator and the needed positive pressure on the intake face, or more efficiently - the needed negative pressure on the outlet side of the radiator (this is "static pressure").  In order to turn a fan fast enough and big enough to get BOTH the CFM and static pressure is really hard to do with simple electric fans.

One way to increase static pressure is to stack fans, and a way to get more CFM over a specific surface area is to split up the surface area between several fan assemblies.  The ammount of heat that a common DD 2-stroke rejects to both the cooling system and the engine compartment is huge.  An electric replacement for a prime-mover driven cooling system is rather expensive as well (I spent more than $4K [I saved a ton of money by building my own motor controller $$$], and the system only hit about 85% of the effectiveness of the original hydraulic drive).


You say you would "like" to get rid of the blowers...  but do you really need to?


One of the things that I've started to fall back on is the "cabin mentality".  Leaving what was there before and building it into the new stuff.  After all - "its a bus".  There are some things that I'm changing (instruments and air to electric conversions for the accesories), but a lot of the old mechanical equipment is staying untouched.  While I may do minor adds to the way some parts work, the system's general design remains untouched (I'll confess however, this wasn't my first approach either Roll Eyes).

Cheers!

-Tim
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