| Author | Message | ||
| Greg Peterson Rating: N/A |
If you look at the Cat RV performance paper it has a graph of cooling fan HP. It is over 20 HP when the engine is at 2000 rpm. It is even more for the bigger engines. These are for modern 4 stroke engines that are very efficient. It must require even more HP for a two stroke. Now I can uderstand why that fan belt is so big on my MCI. What ever happened to the guy that was going to put electric fans in his bus? If he made that work he should patent the idea because it looks like it could save fuel. | ||
| JW Smythe (Jwsmythe)
Rating: N/A |
Cars have the same issue. That's why those flex fans became popular. They bend flat at high RPM's, so they don't drag as much. I know many cars have gone electric, but really depend on the motion of the car to push air through the radiator to stay cool under load (i.e., when driving). The big diesels need a lot more cooling. I suspect it may be difficult to get electric fans big enough to keep the engine cool enough. You may get away with it, if you can duct enough air through the radiator when it's moving (and not remain stopped for very long). That may end up making something rather large and ugly hanging off the side of the bus. I'm not near my bus right now. Do these fans have clutches on them? I wouldn't suspect so, since they aren't turning any real high RPM's. | ||
| Gary Stadler (Boogiethecat)
Rating: N/A |
Shhhhhh Greg... "the guy" quietly disappeared after his project miserably failed (I believe he never even attempted it even after being given free new fans by Stan) The best solution is a fan clutch or variation of it, so you can simply turn the fan down or off when it's cold out and you're not humping a giant grade. (actually implemented by an automatic thermoelectric switch) My firsthand experience- I put a Horton 2-speed eddy-current fan clutch in my Crown (side radiator) that goes at about 1/4 speed when de-energized and full tilt when energized. During winter driving and even in San Diego summers when I'm on flat ground, I rarely see the fan turned fully on. My combination of a giant radiator and the slower speed created by the eddy current drive keeps it off 95% of the time. The eddy current thing is necessary in my case because being a side mounted radiator, I need "some" fan power all the time, but not full power. Being thermostatically controlled, the moment I hit a grade, on it comes. Watching the temperature gauge is amazing- the thing will cause a drop in temp from 190 to 175 in about a minute, and you can hear that horsepower being eaten alive by the fan!! I also have a bluebird bus which has a straight on/off clutch, because the engine is in the front and simple ram-air is enough to keep the engine at 180 under most circumstances. But hit a grade even in a moderate temperature, and on the fan comes. An interesting point, yes the fans do take 10-20 horsepower. That said, my Crown got 10 MPG on the way home (it's maiden voyage for me), with 5.29 gearing, factory fan going full tilt, at 61 miles per hour (max speed) at 2500RPM. After I got it home, I put in an over drive transmission, so now I could go 75 or so, which I do most of the time, now at 2100RPM. Still get 10MPG. Then I raised the roof a foot, and added the Horton fan clutch, a bigger radiator and a massive plastic fan, and probably 10,000 pounds of "stuff" for the conversion to the Burning Man Palace that it now is. Still 10MPG Seems like the Crown likes to get 10MPG no matter what I do to it...although NOT having the noise of that massive fan all the time is quite nice on the ears.... | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
MY 80 Eagle had a thermostatically controlled fan. The fan was driven by V belts thru a hydraulic type clutch that was activated by engine temperature. Richard | ||
| Kyle Brandt (Kyle4501)
Rating: N/A |
IMHO The only benefits of electric fans are: 1- easier to drive when radiator is not in line with the crank shaft. 2- can use battery power when all of the engine power is needed for pulling. Some of the draw backs are: 1- efficiency - to many conversions of work - rotary to electric then electric back to rotary. 2- 20 hp motors are expensive. 3- Wiring & alternator sizes required. There ain't no free lunches. If electric fans were the best way to go, they would be used by the bus manufacturers who have engineers that KNOW the cooling loads required. If you find yourself needing elec fans, I would suggest finding a bus that had 'em from the factory & copy that as a start. Good luck kyle4501 | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
To get a 20 hp motor you would need a three phase genset. They do not make single phase motors that big (20 hp). If it were available, a single phase motor would require about 100 amps of running current at 230 volts. Inrush would be in the 600 amp range. Please do not bring back the nut that screwed Stan out of a fan motor. Richard | ||
| Chuck Lott (Chuckmc8)
Rating: N/A |
Richard is right....just let it gooooooooooo | ||
| john w. roan (Chessie4905)
Rating: N/A |
Look at the pitch on the fan blade on...say a 4905 or a 4104 and number of blades. most electric fans are smaller with much less pitch in their blades.Think of the pitch as screw threads...coarser and deeper pitch will "screw" the air through faster in greater volume.I wonder if anyone has any stats on how much air the AC condenser fans move? Could be a way to add auxillary cooling to a setup with overheating/ bigger engine, turbo, or big injectors with limited radiator problems. | ||
| John Jewett (Jayjay)
Rating: N/A |
Gary, I imagine that if you converted MPG into PPH (pounds per hour) then let your engine run at the aforementioned 2100 RPM for an hour while sitting in the back yard, the fuel burn would still be about the same. DD's are like that and so are the big Ford 550CID industrial engines. Maybe your manuals would give the specific fuel consumption figures for each RPM range. ...JJ | ||
| Gary Stadler (Boogiethecat)
Rating: N/A |
You're probably right JJ... the mileage seems to have very little to do with how I drive it and how I load it, even over the mountains. Funny how that is.. and all along I thought it was the cool Crown curves!!  | ||
| Donald Lee Schwanke (Dontx)
Rating: N/A |
In my experience, rpm is everything when it comes to diesel fuel economy! I was able to experiment some with mine, and found that the cruise rpm would make a great fuel useage meter. We often hear old wives tales that you must run a DD two stroke wide open, simply not so with the old bus engines, with peak torque at 1100 RPM or so, and much less at 2100 or so. | ||
| DMDave Rating: N/A |
I think that came from the stationary units needing all the HP they could get. They used to run the Detroits wide open in the TimberJack log skiddrs too. I dont know anyone could do that all day that close to somthing screaming that loud. 35' aft is ok. | ||
| Tom Caffrey (Pvcces)
Rating: N/A |
DMDave, weren't those skidder engines the 53 series? I recall those being a whole lot louder than the 71s. I think the governor on them was usually set around 2800 or so, and that made them a little hard to take. For what it's worth. Tom Caffrey PD4106-2576 Suncatcher | ||
| Phil Dumpster2 Rating: N/A |
Back on the subject of cooling an engine, has anyone ever mounted the radiators on the roof of the coach, like a railroad locomotive? I wonder if that were done then it might be possible to use an electric motor to run the fans, and due to natural convection and/or forward motion enough air would be moved to provide sufficient cooling. | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
Where are you going to get 20 hp electric motors and then where are you going to get the power to run them? Richard | ||
| Tim Strommen (Tim_strommen)
Rating: N/A |
Gillig's experimental Fuel Cell Transit Busses use DC electric fans plus a roof mounted radiator for cooling the system. I don't know how much heat they are dissapating, but the motors are made by Lemco LTD out of the UK. These pancake motors (Axial Gap) can generate incredible ammounts of HP and RPMs from only a little power. The motors produced by Lemco LTD are being used in Fuel cell and Hybrid busses in both the U.S. and the U.K. as replacements for engine driven (belt, shaft, or hydraulic) fans. If one was to try to drive a fan with an electric motor, it would be recommended to have a secondary power source for emergencies... Also, these motors are not cheap - they can run over $2K U.S. pretty quickly (with options...). Cheers! -Tim Strommen | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
I really do not consider that they deliver an incredible amount of hp from only a little power as you state. Looking at the specifications for the largest motor (LEM 200) at 24 volts and 140 amps it delivers 3.36 kw. That is about 4 hp I believe. It would take at least five of these to produce the 20 hp required to cool a radiator. And 840 amps at 24 volts. Of course the radiator would have to be large enough to accommodate the space requirements of five fans. Does not really seem practical to me. Richard | ||
| Tom Caffrey (Pvcces)
Rating: N/A |
Richard, unless those motors are 100% efficient, the 3.36 kw is the input power only. This does not tell us the output horsepower. For what it's worth. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska | ||
| Tim Strommen (Tim_strommen)
Rating: N/A |
At 24VDC/140Amps, this motor will spin at 1300RPM, with a devilery of ~2.7KW (80% efficient) with 20Nm (~15lbft) of torque. This works out to about 3HP. (torque [lbft] X RPMs)/5252 = HP However (for the fuel cell busses I was referring to) at 60VDC/225Amps, this motor will spin around 3400RPM, with a delivery of ~14.5KW (87% efficient) with 30Nm (~22lbft) of torque. This works out to about 14HP. But you'd have to gear down the motor's output to keep the blades efficient - which increases the torque (lowering the speed) - etc, etc... Anyway - I did say fan>s<. When I looked at the VTA busses, they had three on the roof. Previously when this topic came up on the BBS, I do recall myself and others warning away people from simply dropping an electric fan in to replace a belt drive or hydraulic drive fan. This requires a ton of work and in most cases is not feasable. If there are problems with the original cooling system - they should be addressed as standard repairs - not as wheel re-invention sessions. In order to replace a belt or hydraulic fan with an electric, one needs to do the following: 1) Ensure the cooling water is in good condition 2) Ensure that the thermostat and water pump are in good condition 3) Measure the thermal rate of change throught the radiator while the original fan is in place (this requires the original fan to be working - thus if it's just broken, fix it) 4) Measure the flow of water throught the radiator circuit when at maximum load (you need to load the engine to determine the highest heat output) 5) Add 20% to those values 6) Find a motor that can drive the original fan at the same speed under load (this is tricky, really tricky, and expensive) - it's probably easier to find a new fan with the same outer diameter, but different blade counts and pitches so that you don't need to get a spot on match HP for HP, but htis will require some research with MS Excel to tune the right count of blades to the pitch while maintaining the original CFM and static pressure. 7) Find a motor controller that can support the motor's current load (not cheap either) 8) Buy heavy-gauge/high-temperature/oil-resistant wire to run to the motor/motor controller 9) Buy two more 8D batteries, or 4 more group 36 batteries. 10) Buy a 300 Amp alternator for the fan (where did you think that power was comming from?) 11) Put a scoop onto the outside of the radiator opening 12) Blow a hole in the nice smooth side of your rig to install a forced air cooling system for the motor (it needs air cooler than 170degF or it'll burn out) 13) re-measure steps 3 and 4 while spending weeks calibrating the motor controller so that it behaves like what the original fan did (this isn't a weekend thing - I'm talking 8-hour days for several weeks to work out the kinks...) Most likely before anyone gets to the point of step 13, they'll be kicking themselves for not buying the $30-300 part that would have fixed the original equipment - and saved them the stress of needing to look at the temperature gauge every two seconds... (and who can ignore the constant "I told you so's" from the other half... ) [Edit:] It should also be noted that in rear engine (pusher) configurations, the radiator fan is also attempting to regulate the temperature of the engine compartment - so some significant attention should be paid to the air circulation around the block (additional fans and openings for ventilating the engine compartment may reduce your over-all heat load on the radiator -especially with a heat generator like a DD two-stroke). IMHO, stick with the original hardware if at all possible. Cheers! -Tim (Message edited by Tim Strommen on June 05, 2006) | ||
| Stan Rating: N/A |
Tim: Did you get your system to work to your satisfaction? | ||
| Marc Bourget Rating: N/A |
Tim, Nice observation on noting the necessity for airflow thru the engine compartment. A question/issue that should have been raised when various posters spoke of punching louvers in the rear doors. [Not saying doing so is wrong, but who checked to see if it wasn't?] | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
Tom, I was being especially generous! LOL Richard | ||
| Tim Strommen (Tim_strommen)
Rating: N/A |
I scrapped the electric system when the motor wires was transmitting about 27 watts of 500kHz RF. Fortunately I found the problem before an FCC tech did . The fan was doing its job but I think the other modifications I made to improve the air circulation had a more positive affect on the cooling and my sanity. Namely on the inlet I put on 10 shutters that act as a scoop when open (by changing the pivot point from the leading edge to the trailing edge from fin to fin, it makes progressively deeper fins towards the back, while taking up the least space and staying syncronized) which added about another 6 PSI of air through-put at 65MPH. I also put in a high temp blow-out at the top of the engine compartment which is fan assisted (that's where I would have put the fans that the Double D had), and direct fan cooling to the exhaust manifold. I kept the heater core from the original Carrier bus heater unit and used two 16" automotive radiator fans just as a secondary cooler. This circuit also kept the original booster pump and solenoid valve as a backup to the mechanical pump to ensure that the water mixes with the water in the block (it also by passes the thermostat so that I get maximum water flow). I did keep the digital management because the system is kinda' complicated (although I'm about to rip it out and do it with a new microprocessor - ahhh toys....) and reinstalled the hydraulic motor (only with a servo controlled proportional hydraulic valve so I get better than On/Off operation). If I had a 48 volt electrical system, I could have used one of the compact motor controllers that's efficient enough, but I think it was an excersize in futility. If one wants to improve the cooling in the rear engine compartments, you probably want to get a small smoke generator and a tiny CCD camera put in your engine compartment (the self illuminating IR cameras work well for this). Then ou can go driving on the freeway and see what is going on with the air in the compartment. I made a few inexpensive and subtle changes to the way the air entered the engine compartment that really reduced the over-all tempurature - but this requires some control otherwise it will never get warm in the winter. And make sure you install your full-width mudflap in front of the engine compartment so that the radiator fan doesn't have to force air out the other side of the bus (or re-ingest the air coming out the same side). Cheers! -Tim [Edit] P.S. The cost of my electric fan setup crossed the $4K mark - if that's not a deterrent to replacing an exsisting system, I don't know what is... -T (Message edited by Tim Strommen on June 05, 2006) | ||
| Stan Rating: N/A |
Thanks Tim. I knew that you had done more serious research on this subject than anyone else on the BB. When I was trying electric fans I tried a short test on flat road on a warm (80 F) day with a slight breeze monitoring coolant temperature. My electric fans were not capable of maintaining temperature at load so making four runs NSEW indicated quite a bit of difference in air flow through the rad depending on the direction of the wind. This would be a consideration in trying to control airflow in the engine compartment. If I was starting to convert another bus with a larger engine I would try the suggestion of running a wind tunnel from the front of the bus or from a roof scoop and use a pusher fan. | ||
| Tim Strommen (Tim_strommen)
Rating: N/A |
Since I'm running a standard body on frame-rail transit chassis for my rig, I couldn't do the wind tunnel down the centerline. What I did instead is cut a four foot long, 6 inch high "window" on each side with cloasable shutters - right above what would have been floor level, underneath the bed (just behind the rear axle). This is ducted to blow on the back of the engine block, and directed towards the turbo and down onto the manifolds. This reduces the interference with the pyrometers (I have one for each side of the 6V92 block) and allows for fast evacuation through the blow-out at the top of the engine compartment door. I also made a short duct above the wide mud-flap at the front of the engine compartment that pulls heat away from the trasmission (if called for) and forces the high pressure air into the engine compartment. I installed tall shutter/louvers below the left side of the engine compartment to direct air torwards the back and centerline of the vehicle, along with a mud-flap on the left side (below the radiator) to reduce air circulation throught the radiator-the engine compartment-and back to the front of the radiator (etc), and under the right side to force air out to the curb side rear of the vehicle. This creates a strong pull through the radiator, and doesn't add any noticable pull to the steering (I used a pull scale to measure this value). But they can also be closed for cold morning starts with the Webasto running The solid length of L-Channel that was discussed being welded to the side of the bus ahead of the radiator was not as effective at breaking up laminar air flow as was staggered 2" pieces of 1"x1" L-channel at 15 degree angles (YMMV for your bus...). Ideally one doesn't want to pull in air around 3' or so to the ground as this air is typically frought with solar energy (converted into heat by the pavement) and isn't as cool as air even one foot higher above the ground. Cheers! -Tim [Edit] Corrected terrible grammar and spelling... (Message edited by Tim Strommen on June 05, 2006) |