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Message |
Duane (24.217.163.108)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, July 07, 2003 - 9:45 am: | |
I was wanting to hear from others on their thoughts of removing the hydro system I now have on the 89 Ealge model 20 and replace it with electic fans attached to the radiator. There are 18" fans that move 2250 cfms. My thought were using 4 of these, all of them able to be switched on or off for cooling needs. This would decrease the weight of the present system,also minimize servicing and eliminate the horsepower robbing belt.
The present system has a belt to run the huge pump and the lines to the fan system and a storage tank that holds 11 gallons of fluid.
The radiator is on a swing out so doing the work and checking the fans would be easy to do.
Help out there give me some feed back!!!
Thanks
Duane 89 Eagle model 20 St. Louis, MO |
Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, July 07, 2003 - 5:11 pm: | |
First, let me say that I'm currently a Crown guy and don't know your bus. I'm just piping in some ideas...
(1) If you replace the hydraulic fan with electrics, you probably won't gain much efficiency, because you're replacing a belt driven energy source (the pump and all it's related inefficiencies) with another belt driven energy source (the alternator and all of it's related inefficiencies). My guess is that either way the energy used/lost will be roughly the same. You'll trade a messy oil tank for a monster alternator... maybe a good trade, maybe not...?
(2) The usual lingo floating around states that either a belt or hydraulic- driven fan system consumes 10-20HP (at the fan) doing it's job. That can translate fairly directly to the question, "if it takes 10 horsepower of belt-driven fan to cool the system properly, shouldnt it also take 10 horsepower of electric fan to do that same job?"... now ten horsepower at 12 volts, assuming 800 watts per horsepower, is 8000 watts, or 666 amps being drawn from your alternator on a continuous basis....not practical I think, nor do I recall 12 volt fans that powerful even being availiable...
So somewhere there is a problem with this thinking that 12 volt fans, even 4 big ones, can move enough air to do this job properly. Keep in mind that a front-mounted radiator has the assistance of freeway wind blowing thru it so the fan does not have to be that large or on all the time. You can get away with a totally electric system easily. But us pusher guys must have ALL of the air supplied by fan ALL of the time, so the requirement on the fan is much more stringent.
That said, I recently machined my 24 inch 8 blade fan down to 22 inches by bolting it to the quill shaft of my vertical mill and spinning it up to 2000 RPM, the cutter being held in the mill vice. In free air mind you, the 2hp mill motor turned the fan at that speed just fine (Virtually everything not attached to the floor of my shop ended up blown into the ceiling!!).
So I am still left wondering if the electric idea will truly work, because I sucessfully turned the fan that everyone says takes 10 horsepower with 2 horsepower.... BUT even two horsepower is 1600 watts, which is 133 amps at 12 volts, which means you gotta have a whomping big alternator to be able to produce that kind of power on a continuous basis in addition to the requirements of the bus....
(3) Back 15-20 years ago I had a Superior pusher whose factory fan and radiator design was about as poor as one could get. I first turned the radiator 90 degrees and mounted it to the rear side of the bus, and made a hydraulic pump/tank/motor system to drive it. It worked but it was the biggest pain in the rear I'd ever constructed. After 5000 miles of putting up with it, I tore it out and replaced it with a big long fan belt driving a 90 degree miter gear that had the fan attached to it. It was sweet. If I had it to do over again, I'd do it that way if it was at all possible. NO oil system, NO monster alternator... just a simple efficient belt drive.
I got the gear assembly from a bus junkyard.. I actually got two of them for a hundred bucks each, just in case I ever needed a spare. In fact I still have the spare here if anyone wants it... that bus is long gone....
Cheers
Gary |
two dogs (209.245.224.28)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, July 07, 2003 - 7:08 pm: | |
my thinking is, you've already got the monster alternator....& it's really not doing much if you have eliminated the origional bus air,so ,I think you have "extra" electricity to play with, the alt. on my Eagle is twice as big as an adults head |
two dogs (67.30.23.5)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, July 07, 2003 - 9:56 pm: | |
I bought two fans from a junkyard for 5.00 each.(I had to remove them)."Autozone" has an adjustable thermostat switch for 20.00...this was on a 1940 Packard with a 455 buick engine...I just have a standard g.m. alt & it doesn't have any trouble keeping everything running & charged..I think your idea will work,just get the biggest fans that will fit on your radiator...
TWO DOGS |
dougthebonifiedbusnut (136.217.0.198)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, July 08, 2003 - 8:38 am: | |
Hey Duane,
Where are you getting your fans cause I'm doing the same thing with my Crown.I'm glad Gary came up with those numbers cause I have forever been a little suspicious of rthe numbers that have been floating around I think just the other day someone said around 35 hp to turn the fan |
Scott Whitney (66.82.9.12)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, July 08, 2003 - 11:02 am: | |
I am going out on a limb here, but possibly Gary was able to spin the fan in the mill with less power than it would need in a bus because there was no shroud or radiator in that system. Wouldn't a closely fit fan shroud and the resistance of the radiator fins themselves, create some forces, which could be a significant factor in power required to spin the fan?
I am thinking of a shop vac. When running with an open hose, it hums along just fine. But as soon as you get a partial clog of the hose, or put your hand over it, the motor really sounds strained - and I would guess, its amp draw goes up considerably. So running a fan wide open would be very different from running a fan in a semi-closed system, no?
Also, the electic motors that came from my old bus heating and A/C system were huge monsters, but yet the fan size was still smaller than the fan on my radiator. So I'd assume that the size of the electric motor required to turn a bus radiator size fan would be a real whopper. Maybe splitting up the load into four motors would bring the motor size down, but would still take some serious electrical power to run, I'd think.
Just guessing. . .
Scott |
Peter Broadribb (Madbrit) (65.73.229.118)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, July 08, 2003 - 12:28 pm: | |
Don't wish to rain on anyone's parade, but this has been discussed many many times before and the concensus of opinions was that it won't work.
As previously stated, the amount of horsepower needed to drive a fan sufficient to cool a regular bus radiator is prohibitive for the bus systems.
If it was feasible, don't you think it would be done by the bus companies? Electric fans would be much cheaper and easier to maintain than a complicated hydraulic system.
The best alterantive system would be to use an angle drive and belt drive the fan from the crank. Nice and simple and very reliable. I had planned to do this on my MC-8 when I installed a side mount radiator. I was going to adapt the squirrel cage drive into an angle drive and mount it over where the a/c compressor was.
Peter. |
Tom Caffrey (Pvcces) (64.114.233.194)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, July 08, 2003 - 10:15 pm: | |
Some information about fans: propeller fans tend to take more power as the resistance to air movement increases but centrifugal fans take less.
From the above, you can see that propeller fans tend to lose efficiency with a head of pressure, but centrifugal fans tend to maintain their efficiency.
The vacuum cleaner sound you hear when you plug the hose is of the motor winding up to a much higher RPM while the current falls. This is because the lower the volume of air moved, the less work the motor is doing.
Some centrifugal circulating pumps are designed to have a minimum head pressure. If they are run without enough head pressure, the motor will be overloaded.
For what it's worth.
Tom Caffrey PD4106-2576
Suncatcher |
Duane (24.217.163.108)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, July 08, 2003 - 11:35 pm: | |
Thanks for all your replies.
more information
I have since removed the bus a/c and have a gear driven alternator that is a 300 amp. All it runs is to charge the 2 8 d batteries. My thoughts were to put this alternator to better use since it runs all the time anyway. The hydralic fan does not seem to turn that fast. I dont know the cfms it has.
But I can buy 4 SPAL 16" fans that run at 2250 cmfs each and pull 16 amps each. That is 64 amps on an alternator that has a capacity of 300 amps.
I am only looking for an alternate way of doing this. I know at the time the Eagle was built in 1989 and thie was probably was the best way to do the cooling system with the hydralic system.
Keep giving me feed back. I do take it all in.
Duane 89 Eagle Model 20 St. Louis |
Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, July 08, 2003 - 11:53 pm: | |
Duane, heck why don't you try it and report back to us. Then we'll all know for sure if it does or doesn't work.
BTW, when I ran my fan up on the mill, I did mention that it was in "free air". I'm sure it uses a lot more HP as Tom says. So 2hp in free air could easily grow when the same fan is shrouded and pulling thru a radiator.
My guess is that you'll quickly be putting four SPAL fans on ebay and redoing your system with a mechanical system of some sort, but if you can afford the time and $ to try it out, I'd be happy to hear about the results. I do have to agree one more time with Tom... if it actually would work, the big guys would be using electric fans on all the busses. They don't....
Cheers
Gary |
Peter Aduskevich (Slowslowpete) (67.75.101.111)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 09, 2003 - 1:25 am: | |
I have a 20,000 lb Bus with a 6bta 180? Cummins. Drove cross country a few times with 2 1600 cfm but had to keep speed down to 55 in hot weather. But i can also run at 55 with out any fans on a dead flat road at 70 degrees air temp. I now have one 1600, 1 2200, and two M.B. condenser fans . Don"t know cfm's but they have 9 or 10 blades and draw 10 to 13 amps. With the four fans I can run at 65 plus now . But hills are a problem. Thanks to FF's donation of a 4106 blower motor., Which I mounted a 16 inch , 21/2" pitch blade from a viscous fan. In clean air it draws 80 amps . Have not tried it yet. Some one was making electric fans for large trucks but could not locate them. I don't know if you will have enough air for your engine. Hope this is of some help. Peter |
Hal StClair (Hal) (65.160.214.159)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 09, 2003 - 2:10 am: | |
Just to give you an idea on the cfm &hp required to drive your fans:
According to Kysor Fan,
9 blade 28" fan 19,500 cfm @ 2200 rpm-30hp@2.5"w.c.
9 blade 30" fan 24,000 cfm @ 2200 rpm-41hp @2.5"w.c.
You 'might' make one of these cool a 8V71 'if' you have a 'good' radiator and well designed shroud. But if you have anything with more 'umph', you probably won't make it.
My 34" fan can pull 51hp at max rpm with my S60. If I were to use electric, I'd have to tow a 40KW genset to drive it! Hp is Hp, weather you get it from the crank or from a genset, there is no free lunch.
Just my way of seeing things. Hal |
RJ Long (Rjlong) (24.127.74.29)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 09, 2003 - 4:09 am: | |
Ok, let me provide a scenario for you to think about:
You set up the electric fans, wired in such a way to run off the coach's electrical system supplied by the big OEM alternator.
Now you go for a drive, and start pulling a 10 mile 6% grade on a 100 degree day. Next thing you know, the alarmastat shuts you down because you've overheated the engine. You've got enough momentum to pull over safely on the shoulder.
Giving the coach about twenty minutes to cool down, you hit the starter button and. . .
NOTHING
Not even a click. . .
Your electric cooling fans have drained your batteries. . .
HTH,
RJ
PD4106-2784
Fresno CA |
Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 09, 2003 - 9:18 am: | |
Good way to put it RJ!!! I've been trying to politely say "it won't work" without being too cast-in-concrete about it. A few guys swear electric fans will work, and who am I to say they won't!
But I agree with you, I personally think it's a pipe dream. Heck, lets let someone make liars out of us, and prove that known laws of physics are only "suggestions"... we might have some fun watching!!! (and more likely, we might have fun hanging around with them having a lot of beers while waiting for their mills to cool down on a hot day!! Dang, too bad I don't drink beer...)
Cheers
Gary |
two dogs (67.30.23.122)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 09, 2003 - 11:48 am: | |
I still think it will work..just unbolt your hydrolic fan,put elec. fans on radiator, (I used wire ties) & take off.. if it cools good enough,bring it home & completly remove hyd. unit.
in the hotrod books the fans cost about 80.00 ea.,at the junkyard they are 5.00 to 10.00,...for an experiment ,I'd try the junkyard ones,ya' could even afford a "spare" |
Peter Aduskevich (Slowslowpete) (67.75.105.205)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, July 10, 2003 - 1:42 am: | |
Do not use thru the rad. methods to attach fans for rad. or tran./oil coolers. The torque from startig and running the fan will ruin the rad.or cooler in short order if only one of the thru ties gets loose. Radiator's tubes and fins are very thin and weak. Peter |
two dogs (67.30.23.31)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, July 11, 2003 - 11:25 am: | |
that's the only way he can mount the fans,they don't have that much torque,just go thru with a plastic wire tie, go around a core & back to itself,it works! |
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