Has anyone used electric fans to replace their hydraulic cooling fans? How many CFM do the hydraulic fans pull through the radiator?
Would something like these work?
Fans | Be Cool Radiators (https://www.becool.com/jump/fans)
These are up to 3140 cfm, about 1/2 HP and use about 26 amps
16 Inch Electric Puller Fan Euro Black Super Duty Be Cool Radiator | Be Cool... (https://www.becool.com/product/16-inch-electric-puller-fan-euro-black-super-duty-be-cool-radiator)
$260 each plus everything else you need. Way less than a hydraulic fan motor, probably less than the rebuild kits.
They make a brushless version too that appears to be variable speed.
So in other projects I have had interest in going with electric fans. Here is what I learned. I understand that our coaches fans are capable of using 80hp. My old Chevy 6.5L diesel used 38hp. Never had on a dyno so don't know first hand. One horse power at 100% efficiency is 746 watts of power as I recall. So that would be 64 amps at 12volts dc for one HP. Just doesn't make sense to run primary cooling fans on electricity when direct drive or hydraulic works so effectively. My current Bronco LS conversion will run two continuous duty fans at 12 amps each. There is a larger fan but they are not rated continuous duty. The numbers are difficult to manage running electric motors IMO
16 INCH ULTRA ELECTRONIC 165 WATT COOLING FAN FFD16-3000CFM SUPER LOW AMP... (https://www.ebay.com/itm/110831358724)
Scott
Correct.
You can't reasonably/practically get the CFM with electrical fans.
CAN it be done-- virtually anything can be done-- but may not be practical. Would certainly require a significant alternator and wiring upgrade.
I've pondered this as well, though electric fans tend to take ram cooling of radiator into effect which we are without. Here's a place with heavy truck specific fans:
Turbine Electric Fans for Over-the-Road Trucks and Tractors (http://www.electricfanengineering.com/turbine-electric-fans/over-the-road-truck-tractor/)
Electric fans work great on the front but won't move enough air for our side radiators. They could provide cooling in case of a hydraulic failure by allowing the coach to be driven at lower speeds. Normally, our Detroit has a huge 300 amp sealed oil cooled, brushless alternator with a direct drive. This could supply enough juice for a big fan but our U300 radiator would have to be larger. Our Buffalo bus had a huge radiator with an equal sized AC condenser. Rear side radiators are a bad deal unless you have a sidewinder engine and can direct drive the fan.
I did see a German bus in San Francisco with a big air cooled flat diesel. It had one big electric fan above. It was idling for the AC to keep the interior cool for the tourists when they came back but the fan was not in use as convection was enough at idle. The rear wheels also turned to leave the parking space plus with the fan above, the driver said they could R&R the engine in about 20 minutes as all connections were modular, the air suspension allowed the bus to lower onto a special rolling cradle and then it could be raised with the air to allow the engine to be rolled out and replaced if necessary. Very cool bus.
Pierce
I to thought that we had no ram air effect, but now think that the low pressure area behind the coach actually draws more air threw than we realize. Wish I knew for sure, but?
Scott
So during the entire DIY wax valve conversion I'm still running my background fans speed at basically off. If I could ever make time and figure out how to read fan speed or fan hydraulic pressure I would actually have a clue on what's going on. It seems to work well so I guess I'll kind of loose interest in knowing.
Scott
I hope "basically off" still has some air flow, as you have to have air flow over the CAC, even if coolant temperature doesn't require air flow.
When I installed a OM617 5 cylinder in my MBZ 406D, the engine went forward to where the radiator had been so I put a truck radiator alsmost flat but at a slight angle behind the transmission. Convection worked at idle and enough air blew through it at normal speeds. Worked great. 23 mpg on trips.
A front radiator or two is this winters project for the U300. Pick-n-pull has late radiators with fans really cheap. Just have to figure out how to get larger hoses to the front. The heater hoses are not quite large enough. The U300 is a perfect 3 season coach but I hate having to watch the temp gauge in our mountains in summer. Just a few degrees more ambient are enough to bring the temps up to 200 or more.
Nice thing about the Detroits, they don't have intercoolers but an aftercooler below the big blower so don't need the fan air.
Pierce
The 60hp claim is disputed frequently. But when hydraulic fan motor efficiency (very low) is figured in maybe. How much air (max cfm) is actually moved by these fans? I think that is where to start.
My 240 amp 40si brushless Deco alternator uses less than 12 hp at max output.* Plenty to run a couple electric fans. If it takes 60HP from the engine to drive the hydraulic pump to turn a hydraulic motor to get whatever CFM it gets that is much more.
More of a mind experiment at this point. Perhaps there was no electric fans available 20-30 years ago to do the job efficiently or reliably.
* my math ... 240 amps x 14.5 volts max = 3480 watts / 746 watts/hp = 4.7 hp / 72% alternator efficiency = 6.5 hp. Plus belt drive inefficiency. So what I read that said less than 12 HP seems about right.
Roger,
Not only the loss from the hydraulic fans but the pump loss on top of that plus the friction loss in the hoses. All adds up.
We used all 318 hp to pump 1000 gallons of water per minute with direct drive to the pump. Using the deck monitor, it took max HP to pump 250 gpm at 80 psi.
Pierce
I believe the HP numbers were for when the controller failed and the fans went on high all the time. The wax valve conversion eliminated that unless on high.
That's why we do so well in 3 seasons. I charged up and out of Death Valley coming back from Q in winter without even looking at the temp gauge but in summer, it's first gear. When the temps are high, the controller goes to high speed so uses more HP and creates more heat. I think 4 electric fans across the face of the radiator would keep it cool most of the time on the flat and in the mountains when the temps are cool. But everything loses efficiency at high altitude, any kind of high humidity and high outside temps. But this is all a guess about electric fan installation. I know Kent Speers utilized a small front radiator and even with a smaller engine, I seem to remember Brett installing one.
We have all the room in the world up front but the bus style coaches utilized that room up front for the generator, etc.
Pierce
Its on my list to investigate. I used to tow a two car trailer all over the east coast with a 305 Chevy van. I replaced my driect drive fan with 2 electrics and picked up .8 MPG solid and never overheated. The Thermo stat switch is adjustable and could be tapped to a upper hose . ' Worked swell.
The air flow in the rear of our busses is not easy to direct or figure out . I plan to tuft test my bus soon before any fan mods. It is entirely possible that air would enter the rear radiator opening without the fan running .
My vision may include a small air scoop into the side, and a set of fans in the rear, if air does exit the rear as hoped.
There is no real reason to run the 50HP fan all of the time . It must cost almost a 1MPG and some outright straight-line performance .
My custom race car/truck had a rear mounted radiator and tuft test showe3d that the air went backwards, from the top , through the radiator.
Photo Sharing. Your Photos Look Better Here. (https://www.chrisgreenphoto.com/Events/SCCA-CFR-Turkey-Trot-2017-Sebring/i-skgK674/A) This pic is from Sebring at about 125MPH. If you look closely , you 'll notice a small tell tale over the bed flowing up, from the rear radiator. The opening in the pas door is the air duct leading under the rad. The air flow went backwards until I extended the roof to the edge of the large wing . The wing's primarily mission was to draw air through the radiator . I should have just allowed the air to flow backwards..
The entire project was to endurance Road race a Ford Ranger( to optimize the rule set ). At this point the front to rear balance was 49% front.
The new owners moved the wing to the rear of the chassis, added new stiffer rear springs springs , etc. Got slower each time ...
Fan requirements for FRONT radiators with "60 MPH forced air" are completely different than side/rear radiators with zero forced air.
Adding a front radiator with electric fan and "T-ing" into the hoses to and from the dash heater core is a pretty inexpensive way to add cooling capacity.
Our rear radiator coach has three electric fans plus the nylon engine driven fan.
Two of the electric fans are on the rear of the radiator and the remaining electric is on the desert cooler radiator for the transmission.
Never had a high temp reading yet. (knock on wood)
Stand behind the coach when these fans are running and you will get dried off and dehydrated quickly. The air flow coming out is very high!
Also, whenever I wash the coach I back flush the radiator fins by squirting water with my garden hose at full faucet pressure.
Standing inside the coach, with the bed platform raised, every spring I check that I can see light coming thru the radiator so I know it isn't clogged. If it is I clean and degrease the radiator.
I added an electric race car fan to my 1981 Foretravel that seemed to help a bit. It had a 3208 cat with a rear radiator.
Perhaps more important is keeping your radiator clean.
Oil and other liquids become dirt magnets and can drastically affect a radiator's cooling ability.
I would say very very little, but that being said I think this may be more of a problem in colder weather. By the time I'm at freeway speeds I'm typically at temperature already and I would think the fan speed has already started ramping up, but unknown. I have IAT protection but have never seen it triggered into operation. Saw my highest continuous IAT last week on 50. 114 degrees. 105 oat. Turning the radiator fans to hi made zero difference. I have no way of bypassing the wax valve control.
Scott
The outstanding question remains, what are the CFM ratings of the hydraulic fans that would need to be replaced by electric fans. Side radiators are different from front or rear radiators, granted. But we are considering the possibility of replacing existing hydraulic fans on a coach with a side radiator with electric fans. It seems to me that equal CFM is a good place to start. Temperature controls and variable speeds would be nice but we have to start with a minimum necessary requirement for sufficient cooling.
Roger- the new Prevost's are using electric fans. I'm not sure how many CFMs , though- but it can be done.
It may be related to radiator size (and shape) and fan size and the number of fans. It might be possible, worth consideration and thought.
ELECTRIFYING THE FUTURE AT PREVOST | Prevost (https://www.prevostcar.com/news-and-media/media-center/news/electrifying-future-prevost)
I'm not saying it can't be done, I'm say I can't afford to build up a redundant system capable of powering fans to gain 4% of fuel cost to return on investment. I'm not going to run 200k a year. Might be plausible if I did. Does anyone privately? Probably get a better return inflating my tires and slowing down 10 mph. At least my tire are inflated correctly. I'm trying. Guess you could retain hydraulic system and overcool with fans to prevent hydraulic from assisting and power with your solar, now it's starting to make sense, heck forget the 12 volt and run ac fans at 120 volts. Hum, maybe your on too something after all.
Scott
Good find! The radiator looks bigger than ours but so is the coach. With an extra alternator, this might work with four electric fans on our coach. I was about to take the AC compressor off and that would be a perfect spot for the alternator. Could go directly to the engine batteries only a couple of feet away. Get rid of the isolator and use a 200 amp battery switch instead.
Pierce
It is just a though exercise. Maybe never comes to pass until you have to replace a hydraulic fan motor (if you can get one) at more than $3K each ... or maybe 2.
Even if the fans only use 40 HP replacing them with electric fans which might only use 5 HP to power the alternator for the extra load is significant. 35 HP is ~10% of what gets to the road now according to dynamometer tests done at Cummins on my coach.
Maybe just add a regulated 120v engine mounted generator to run fans and AC. Just wondering out loud. Its raining today.
It is hardly worth thinking about if the OEM fans on side radiator coaches move 15K CFM. But no one seems to know.
Naturally, the cost of replacing either the pump or motors is a big factor but I always worry about a failure leaving us stuck somewhere. Since our coach spends quite a bit of time in Mexico, I wonder if they even have access to any of these parts. Many thousands of engines and even Allison facilities there but I don't know of any buses south of the border that use the hydraulic fan system.
We have quite a few Pick-n-Pulls in our area and the cost of a double set of electric fans from late vehicles is really cheap along with large alternators from late PUs. Less than $100 for four fans and about $30 for big single wire alternators. Just have to plan it now.
Pierce
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 .
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.
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.
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
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.
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 pumps on the U320's are gear driven.
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.
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. :))
Quick tech facts about a high tech engineered prop fan. Approximately 27" diameter, 8470 cfm, 1000 rpm, 1.2 kw
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.
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
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!
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.
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.
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
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 :))
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.