Skip to main content ↑ ↓
Topic: Side Radiator Coach Cooling Fans (Read 1470 times) previous topic - next topic

Re: Side Radiator Coach Cooling Fans

Reply #25 –
The pic of the fans in the rear side, show fans that appear to blow air into the side radiator.
 Read the rest, yes they blow air into the engine compartment .

Re: Side Radiator Coach Cooling Fans

Reply #26 –
To get a good feel of cfm required,  gross hp output × 40% inefficiency and convert to btuh rejected might be a good start. Once you have the btuh you need to reject a 30 degree delta T would get you into the cfm range. Btuh = cfm x delta T x 1.08. Your current fan size cfm can be estimated using  Loren cooks compute-a-fan app and picking a crappy stamped steel blade, and maybe 0.5" esp (external static pressure which is reasonable for our radiators), you can adjust hp results using 150 degree air if you wish. I have played with this math exercise and came to the same conclusion, my 300 hp coach is only using 5-10 hp to drive the radiator fans. This evidence is appears consistent with the  power transmission capabilities of my (2) 5/8" drive belts to the hydraulic pump. Those belts just can't transmit much more hp. Long story short ultimately the hydraulic pump belts capabilites  will be the best indicator of your fan hp consumption as it takes into account all inefficiencies. Period no matter what some claim.
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: Side Radiator Coach Cooling Fans

Reply #27 –
I owned a Newell for 5 years before my Foretravel. The fans were thermally controlled. The fans would cut on at 210 degrees and cut off at 180 degrees. Much better than running all the time.
Chappell & Mary
36' 2004 Foretravel U270 build #6273

Re: Side Radiator Coach Cooling Fans

Reply #28 –
And another  much more simple method to determine cfm. Finned area of the radiator in sqft x 800 to 1000 feet per minute is cost effective
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: Side Radiator Coach Cooling Fans

Reply #29 –
Seems like in my case ,I could mount 2 fans across the top of the rad ,wired to a controller that comes on at 200.
  Below that, another set that does the same. The lower set  would be backup as the lower part should be cooler than the upper area.  It's possible that my Cat would run better at 200, than it  does at 180.

Re: Side Radiator Coach Cooling Fans

Reply #30 –
The Prevost fans are reversable.  Normally blow if but reverse occasionally in the summer to blow off leaves and trash. In the winter they blow out to clear snow. 
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Side Radiator Coach Cooling Fans

Reply #31 –
Quote from: Old phart phred –
To get a good feel of cfm required,  gross hp output × 40% inefficiency and convert to btuh rejected might be a good start. Once you have the btuh you need to reject a 30 degree delta T would get you into the cfm range. Btuh = cfm x delta T x 1.08. Your current fan size cfm can be estimated using  Loren cooks compute-a-fan app and picking a crappy stamped steel blade, and maybe 0.5" esp (external static pressure which is reasonable for our radiators), you can adjust hp results using 150 degree air if you wish. I have played with this math exercise and came to the same conclusion, my 300 hp coach is only using 5-10 hp to drive the radiator fans. This evidence is appears consistent with the  power transmission capabilities of my (2) 5/8" drive belts to the hydraulic pump. Those belts just can't transmit much more hp. Long story short ultimately the hydraulic pump belts capabilites  will be the best indicator of your fan hp consumption as it takes into account all inefficiencies. Period no matter what some claim.
The pumps on the U320's are gear driven.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Side Radiator Coach Cooling Fans

Reply #32 –
Multiple electric fans mounted close to the radiator focus their airflow to a smaller area of the radiator core, reducing the amount of heat transfer available by the rest of the core depending on how many are operating. The further the fan from the core, the more even the flow across the core for better heat transfer. Draw thru fans provide a much more even airflow distribution than blow thru fans. Multiple Draw thru fans when one isn't working have to have something to prevent air from bypassing the core as air seeks the path of least resistance. I also Would love to get rid of my heavy hydraulic fan system, the pump, bracket, and oil tank. Advances in engineered plastic propeller fan design made by a lot of research by air conditioning companies has resulted in the addition of grooves in the prop to prevent airflow from migrating along the blade to the tip and falling off the blade. They have also added turbicles to the blades to make all of the blade effective. So far this research has produced fans with 30% more flow, while using 20% less power :o. Bad news is they make a lot less noise. These high tech propeller fans are available as replacement parts.
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: Side Radiator Coach Cooling Fans

Reply #33 –
I found that placement of the face of the fan relative to the face of the radiator affected the efficiency of the fan. Even with a surrounding shroud, being too close a distance between the fan and radiator severely reduced efficiency.
I found this out way back in 1966 when investigating why a stock car kept overheating. The owner tried different quantity of blade fans, adding a shroud, installing a bigger radiator, leaving out the thermostat, adding spacers to get the fan closer to the radiator and he still couldn't get the engine to run cool.
I took one look and saw that the fan was way too close to the radiator. Changed spacers so the fan was as far away from the radiator as my 1957 Chev and he never had a heating issue again. (this diagnosis cost him two six packs of Pabst and we each drank a six pack.)
Back then I worked cheap, but not free. :))
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

Re: Side Radiator Coach Cooling Fans

Reply #34 –
Quick tech facts about a high tech engineered  prop fan. Approximately 27" diameter, 8470 cfm, 1000 rpm, 1.2 kw
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: Side Radiator Coach Cooling Fans

Reply #35 –
300 hp x 2544 btuh/hp × 40%=305,280 btuh heat rejection.

305,280= 1.08 x 30 delta T x cfm
CFM required= 9422 cfm

Delta T based on the midpoint temperature between 180 degrees engine water and 120 degree ambient air temperature  0.5 x 60= 30 degree delta temperature.

Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: Side Radiator Coach Cooling Fans

Reply #36 –
Quote from: Roger & Susan in Home2 –
The Prevost fans are reversable.  Normally blow if but reverse occasionally in the summer to blow off leaves and trash. In the winter they blow out to clear snow. 
The world of computer controlled everything. Truly a love/hate relationship. Smart how they are attempting to get the best of both worlds. But fans generally work one direction well. I personally have chased better/cheaper fans operation costs for my coach. In playing with my manual fan override operation capabilities now on my coach i almost think the instant fuel economy being reported shows a  Decrease in fuel used with the application of 100% fans? All i can guess is a reduction of the low pressure behind the coach? No possible way IMO to accurately measure in my world. We will be driving southern Nevada to Michigan, North Carolina returning to Nevada next month. A 4% reduction would be mentionable. 5000 miles at 9 mpg at 4$ gallon would see a cost saving based on 4% being about $89 savings. I doubt on a $2200 fuel cost I would notice either way. Again maintain good tire pressures and slow down and probably see better savings.
Scott

Re: Side Radiator Coach Cooling Fans

Reply #37 –
It seems that all calculations above are based on total heat produced by the engine.  So, about 40% of the heat goes to pushing the pistons, and 60% is divided between the engine surfaces which radiate some heat, approx half the heat goes out the tailpipe, and the rest is dealt with by the cooling system.

 What is really required, however, is enough cooling capacity to drop temperatures across the radiator by...say...20 degrees?  Figuring a radiator and fan system large enough to transfer all waste heat seems wrong to this non engineer. 

I suspect a significant lack of engineering was applied to current fan/rad design as evidenced by 300 hp coaches having the same cooling system as 450 hp.  Cleaning this stuff out the engine bays would be marvelous.  In addition, with electric fans and enough solar panels....you can actually lay claim to having a partially solar powered motorhome!
"Not so  long ago we were a nation of risk takers, riding five million pounds of  thrust straight into space."  Joe Gresh
Chuck Pearson
1996 U295
2018 Can Am X3 TurboRS

Re: Side Radiator Coach Cooling Fans

Reply #38 –
What about... My ultralight airplane has a 35HP engine , driving a 54 in prop making about 220#s of thrust at WOT.  Thats a lot of CFM for sure.
 My bus engine fan pushes air out of the rear radiator . How much thrust? Maybe 24in fan at 2000RPm makes 60#s of thrust?? 
 If that is not running, I lose that thrust and the bus slows down..  If I fit electric fans that make 60 #s of thrust and they only come on  during uphills. That should work well.      But steady state cruise  I may lose MPG due to the loss of thrust?

  Real world is that the fan cost more energy than it ever could push .  Not running it  could save some fuel and noise.

Re: Side Radiator Coach Cooling Fans

Reply #39 –
I wonder if the hydraulic motors that have been replaced were just seal leaks. My '81 now over 40 years old has a single hydraulic motor with a large fan. I used it for up until 2012 and only replaced the pump seal once. I replaced both motor seals on my Monaco using the same system as the Foretravel's and the 2 motor seals on my coach while they were just seeping. With clean oil I don't see any reason for the motors to do anything but wear the seal out. Has anyone on the forum had a mechanical motor failure? I have 2 spare seals in a ziploc bag if mine ever need them.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Side Radiator Coach Cooling Fans

Reply #40 –
Chuck,

I wonder if the two fan systems use the same pump and the same seal? Are the two pump systems utilizing the same motor as the single?

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Side Radiator Coach Cooling Fans

Reply #41 –
For about 20 bucks or so you could build a misting system that would work every time. Had one on my Eagle and one on the Foretravel , replaced the radiator on the Grand Villa and have had no problems since. Just saying :))
Andy & Eileen
MONTROSE COLORADO
1992 U300  40' 6V92 TA
2016 4 Runner
1998 Jeep Grand cherokee

1998 Jeep Grand Cherokee) Build # 4135 Skp# 122921
 

Re: Side Radiator Coach Cooling Fans

Reply #42 –
Quote from: Pierce & Gaylie Stewart –
Chuck,

I wonder if the two fan systems use the same pump and the same seal? Are the two pump systems utilizing the same motor as the single?

Pierce
The '81 uses a very common U.S.A. TRW pump and the same with the motor. Single hydraulic system for steering and fan motor. They are both different than what is used on my '99. The '99 motors are both the same just different part numbers because one comes with the hydraulic control valve both used the same seal kit. Off the rv subject but Caterpillar uses a hydraulic pump and motor system for the drive systems on their track powered equipment rather than direct drive.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean