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  1. #1

    Join Date
    Jun 2002
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    204
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    Aiken, SC
    Tractor
    Kubota 3710, 1970 Leland 384

    Default Has anyone switched to an electric fan?

    I am currious to know if anyone has put an electric fan on their CUT?

    I have thought about putting one on my L3710. On the documentation that I have seen (ads) they claim 3 to 5 hp. recovered on the engine.

    I know that there would be an additional load on the alternator, but it would seem that a thermostaically controlled fan would be more efficient.

    Anyone have any thoughts or comments on this idea?

    Come to think of it this forum is full of those. Seems like a redundant question.

    Don

  2. #2

    Join Date
    Jul 2001
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    1,806
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    Houston, TX.
    Tractor
    2001 TN65, 1951 8N Ford

    Default Re: Has anyone switched to an electric fan?

    That three to five horsepower is on a way higher horsepower engine. I doubt very seriously a tractor manufacturer would devote that high a percentage of the available power to the fan. You could give it a try, just save your old fan just in case it doesn't work out.

  3. #3
    Gold Member
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    Jun 2000
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    499
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    Syracuse, New York
    Tractor
    1952 Case DC-4, 2001 JD4300 MFWD, HST

    Default Re: Has anyone switched to an electric fan?

    I think electric fans are much more usefull on road vehicles because much of the time the vehicle is moving fast enough to get sufficient air through the radiator to cool the engine without the fan. There is usually no need for a fan at highway speeds. Since tractors rarely travel that fast[img]/w3tcompact/icons/wink.gif[/img] the situations where a fan would be not needed are very few. Also, large electric fans use a surprising amount of power. Most CUT alternators would be hard pressed to keep up with the electrical demand.

  4. #4
    Veteran Member jimgerken's Avatar
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    Nov 2001
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    Minnesota
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    John Deere 3720

    Default Re: Has anyone switched to an electric fan?

    MJB has a good point about highway speeds. I converted a small car once. It was a great idea most of the time. When moving, the fan did not run. If caught in traffic, it would run continuously. The motor was something called a "printed circuit" motor, and drew a lot of current. It also did not last long ( a few years). You will not get something for nothing. If the airflow is similar with the electric fan, the power requirement will be higher than the belt-driven fan is. There are losses in the electrical system. The only way this will pay off is if you do not require the fan running some times (that speed thing).

  5. #5
    Veteran Member
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    Feb 2002
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    WVa
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    Kubota L3710, Ford 5600, Case MB4/94, Kubota B6200

    Default Re: Has anyone switched to an electric fan?

    I'd be concerned about overheating which is not unusual because of the screen in front of the radiator. It's not unusual, for me at least, to have to stop several times a day and clean the screen. You need to keep an eagle eye on the temp gauge. If it's higher than normal, the screen is blocking up.

    No matter how hard I've worked the tractor, the temp gauge has never risen above the regular reading unless the screen is filling up.

    Adding an electric fan might compound the problem. I know as long as the engine is running, the mechanical fan is working. With an electric fan, you may not catch a problem fast enough. I've been surprised at how fast the screen can block. If that coincides with a electric moter failure, the results could be expensive. Your temp gauge could be normal one minute, you get distracted by something that happens, and when you look back at the gauge it might be pegged.

  6. #6
    New Member
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    Sep 2002
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    New England
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    Kubota L48

    Default Re: Has anyone switched to an electric fan?

    Hmmm.... Maybe I can weigh in on this topic. I've been designing electric fan systems for automotive OEMs for 10 years. Some of the points I mention below have already been made on this thread, but I'll restate them anyway.

    There are at least 3 reasons I can think of that car OEMs use electric fans:

    Speed Control
    Noise
    Cross-Mounted Engines

    The chief negatives are:

    Cost
    Cooling Power

    Other options include hydraulic systems - but the cost is prohibitive.

    The main reason an engine fan wastes power is that it often provides more airflow than is necessary. It is the nature of the design. One of the main reasons that they are used is that electric systems can not deliver enough cooling power for certain applications. The other is cost. Electric automotive fans cost at least 5 times more if serious cooling is needed.

    As many have mentioned the electric fan will not use as much engine power. Mostly this is because any fan will consume power as a function of RPM^3 (flow scales linearly with RPM, but power goes as the cube!). The engine RPM is all over the map whereas the electric motor RPM is not. The engine fan has to be designed to deliver enough cooling for low RPM/ high heat dissipation conditions (trailer tow up steep grade with automatic transmission at 30mph with A/C cranking in Death Valley in July). Therefore the engine fan will most likely produce more flow than necessary under many conditions. Of course the viscous clutch is supposed to mitigate this but it works by banging the fan on and off according to the exit air temperature from the radiator. This means that power is robbed in a all or nothing way which results in short bursts of high losses. The same can be said of the electric system with the exception that the electric fan RPM is constant and thus it is more likely to take less power but for longer periods of time under high RPM conditions.

    The drag racers I know use electric fans and waterpumps.

    Another reason why higher power is associated with mechanical fans is that electric motors that can deliver a lot of mechanical power at 12V are very expensive. You need a lot of current and that takes a lot of copper & iron (to carry the magnetic flux) to be efficient. Not to mention a bigger alternator. Therefore electric systems are not usually designed for bigger applications such as: pickup trucks that need buttkus cooling at high speed to meet trailer tow requirements - or sports cars that need very high speed cooling.

    Electric fans usually lose out to engine fans for high speed applications because the electric fan is designed to run at one or two speeds whereas the engine fan speed is a function of the engine speed. All fans become windmills at some high speed. That is to say they all get in the way of cooling the car but the engine fan gets in the way less than the electric fan at really high speeds because it will spin faster than its normal 'design' speed because the driver is winding out the engine. Of course the other reason is that the huge tip clearance of the engine fan becomes an asset when trying to force a lot of air through the fan. Electric fan designs often use either partial coverage shrouds or so called speed flaps to overcome this problem.

    I spent some time at an OEM proving ground working on top speed cooling of a certain American sports car icon. The engine fan did rob ~5% of the engine power, but that only gives the cube root of more top speed in the car ~ 1.5%. When we swapped in the electric fan the car was going 2.25 mph faster (big grin for those of you doing the math) but we had to shut it down after only 2 laps because the engine oil was exceeding 275C. With the engine fan the car could run all day.

    Electric fan systems are usually as efficient as purely mechanical systems at the best design condition for each. The reasons are manifold. One major reason is that the fan itself can be a lot more efficient if it is applied to an electric motor than to a viscous clutch on the engine. First off the mechanical system needs huge clearance between fan blade tips and shroud to allow for engine roll. Whereas the electric system can accomodate a gap of ~1% on fan diameter which greatly reduces recirculation losses. Moreover the electric fan can be designed to meet a lower max RPM criteria (someone might rev the engine fan to 10,000 RPM but that would never happen with the electric motor) and with the lower max RPM comes lower mechanical stresses. This in turn allows the viability of a continuous band around the blades to further reduce recirculation (bad for efficiency and the production of broadband noise based on the ingestion of turbulent eddies on the leading edge of the airfoil). But an economical banded fan design would never survive on an engine fan - it would burst from the radial displacement of the blades that in turn cause bending stresses in the fan band. The mechanical considerations of the engine fan drive the blade design towards strength instead of aerodynamic considerations. Only recently have we seen plastic engine fan blades molded over steel hub plates and the blade geometry is very simple. Prior to that all engine fans were stamped steel which of course severely limits the blade geometry.

    When the electric fan is off then the power loss is very small - it is only the extra amount of alternator loss associated with the larger alternator needed to run the electric fan. When the engine fan is off it still consumes a lot of power through the viscous clutch. Those clutches are not made of cast finned aluminum for nothing!

    Another important point is that the electric fan is controlled by a thermo switch in the coolant whereas the mechanical fan is controlled by a thermo-switch in the air. These two temperatures are not completely hard linked and thus to insure safe coolant temperatures the engine fan often runs 10% more than is necessary.

    Fan noise can be reduced by skewing the blades and by introducing a band. As mentioned before the band will cut down on ingestion of the tip vortex as well as a bunch of messy eddies. The skew works by reducing the velocity normal to the leading edge of the foil. Skewed blades usually require corrections to the raked profile of the fan to be able to maintain efficiency. The bottom line is that a quiet blade is not a strong blade - and therefore engine fans are noisier than electric fans when all other things are held equal.


    Noise is only an issue when the car is idling or at lower speeds. Otherwise the engine and/or wind noise will mask the fan.

    The Ford Crown Vic uses a hybrid system that has an electric fan upstream of the engine fan. They counter-rotate. It is a good setup, when the cop car or taxi is idling with the A/C on then quite possibly only the electric fan is needed - which is quiet. When the cop is in high speed pursuit his car will not overheat because the engine fan will crank. But moreover he can get that slingshot start with the viscous clutch off because at low speeds the electric fan was doing the job but then 90 seconds later when the high heat flux comes into the radiator the corresponding hot air will trigger the viscous clutch and buttkus cooling will be available.

    I also took part in engineering a dedicated 42volt system that we installed on my truck. It used a second alternator with output voltage that floated from 3-42V according to the vehicle cooling needs. We used two fans on very large brush motors. My colleague patented the idea and I ran my truck like that for 3 years. Unfortunately it was too late to generate serious interest in the OEMs because total vehicle 42V is now just around the corner. Nonetheless I can tell you that we took the electric fan to a test facility and proved it could cool the truck almost as well under all conditions - and I can attest to how much quieter it was. It also had better acceleration and long term logging of the operation of each system showed that ultimately the electrical system was more efficient for meeting the varying needs of my truck. Having said that the cooling airflow needs of a compact tractor are much more consistent than that of a truck.

    In the future we will see electric fans on larger power applications. There are two reasons for this: the auto industry is switching over to 42V and brushless motors are starting to be economically feasible. Brushless motors are more efficient and obviously the higher voltage allows for lower joule losses in the transmission lines. The net result are fan motors capable of ~ 1 hp at the shaft. When placed in a dual fan configuration this will be powerful enough to cool many more applications and extremely flexible given the ability to more closely integrate the motor control strategy with the engine computer.

    Having said all that .......


    I don't know much about tractors except what I have read here and my 2 weeks of experience with my new B2150 :-) But I did notice my tractor has an engine fan with plastic blades. I did not notice if a clutch was present or not.

    In my view it probably does not make sense to put electric fans into tractors under the current circumstances.

    The serious noise advantages will not be realized - not over the masking produced by the diesel.........
    The cross mounted engine is not an issue - because regardless of the orientation of the engine the vehicle never travels fast enough to need to orient the radiator to recover the vehicle dynamic pressure.
    The max RPM producing too much cooling and robbing too much power should also not be an issue because the tractor is designed for one fixed RPM. So long as the fan has been designed to match the cooling needs of the engine at the design RPM then it should not use too much power.

    Therefore the extra cost of an electric system probably can not be justified. Moreover the mechanical system is cheaper to maintain because automotive DC motors are not designed to be repaired.

    Eventually tractors will probably switch over to 42V and by then high power brushless motors will be economical. In that environment I can see where the superior control and better efficiency will eventually appeal to the OEMs enough to justify the cost.

    That is my two cents as to why the OEMs might not make tractors that way yet.

    As to conversion of an individual tractor well it really comes down to how well the mechanical fan has been engineered. If it produces exactly as much flow as is needed at the design RPM then I think it is probably hard to seriously beat. If not then the potential exists - but the cost includes a larger alternator to go with the electric fan. It is very possible that the fan is over-designed. I know in the automotive world there is a strong desire to reuse parts, particularily for low volume applications. Sometimes this means that it is spinning faster than need be because it is inexpensive (reused part does not have to be engineered, validated etc...). I have no idea if this extends into tractor design. If the tractor uses a viscous clutch and it is banging on and off when you use it then opportunity exists.

    Another less expensive possibility is to try a larger fan pulley.

    At the other extreme .... one sure way to increase output power through investment in the cooling system is to increase the radiator capacity and then you surely may reduce the fan power regardless of the type of system used. But that is a big investment.......

    Sorry for such a long post.

    Booth

  7. #7
    Gold Member
    Join Date
    May 2002
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    296
    Location
    Zelienople, PA
    Tractor
    L2500

    Default Re: Has anyone switched to an electric fan?

    I think Booth has it.


    In my opinion. I do not think it would be cost effective either. You may wind up with more headaches than you want.

    I do a lot of modifications to jeeps. And it never seems to fail that once you change one thing you and up changing a few other parts too.

    If you are looking for more power why not trade in your tractor. Eveninf if you hade more hp you are limited to your traction available.


  8. #8

    Join Date
    Jun 2002
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    873
    Location
    N Central Ohio
    Tractor
    NH TC35D/SUPER H&M/F-20/JD B&D/FORDSON/JD250 SSL

    Default Re: Has anyone switched to an electric fan?

    If u have a hydro and it has an oil cooler w/ the
    radiator the fan would need to run all the time
    to keep oil cool or major $$$$$$$$$$$.

  9. #9
    Veteran Member
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    Apr 2000
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    1,028
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    Mid-Michigan
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    Kubota L3710 GST

    Default Re: Has anyone switched to an electric fan?

    WOW!
    Very, VERY interesting! (I read the whole thing even though you were WAY over my head on some of it)

    We could use your expertise over on the GoldWing website where there is serious arguing going on over cooling (or lack thereof) and fan design [img]/w3tcompact/icons/laugh.gif[/img]

    pete

  10. #10

    Join Date
    Sep 2002
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    83
    Location
    Ohio
    Tractor
    ford 3000,case SI..Just purchased a 404 Futon (40 hp 4wd) with a koyker FEL

    Default Re: Has anyone switched to an electric fan?

    ok my 2 %...i have installed electric(useally GM ft whl dr) fans on a fewJD tractors and IH combines...they worked flawless.I run one on my CJ7 Jeep...which is used mostly off road.I use a manual over ride off sw..shut fan off for water crossings.thinking very seriously about installing a "pusher" on my 3000.as was mentioned about cleaning the ft of the radiator while mowing,when the temp gets in the red..is clean out time again..i`ll let you know if it takes care of the timothey seeds ...Sid

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