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Old 08-02-2016, 10:01 AM   #21
Bus Nut
Join Date: Jun 2016
Location: Orange County, CA
Posts: 525
Year: 1990
Coachwork: integral
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
Originally Posted by Bamboozle View Post
So I am about to embark on the change from my hydraulic fan to an electric i was wondering what where the difficulties you had in the process...Also what is the best type of fan will a Taurus fan really work? Any info is greatly appreciated.
Just bear in mind that it would have been a lot cheaper for Gillig to have installed electric fan(s) at the factory instead of a hydraulic system - there's probably good reason they went hydraulic. The general concensus on other bus conversion forums is that electric fans can never duplicate the CFM and cooling ability of a well-designed hydraulic or mechanical system, and folk who put electric fans in their rear-engine buses always have problems later with overheating, especially when climbing hills in hot weather. Good hydraulic systems have a temperature switch that controls a solenoid to restrict hydraulic fluid flow at lower temperatures - this will greatly reduce the power requirement at lower temps. How is the rest of your cooling system - is it in good condition overall?

FYI, I'm now in the process of completely replacing my entire cooling system because I've had steadily-worsening overheating problems since I bought my bus. I had Atlas Radiator in Santa Fe Springs CA make a new core that has 10% larger surface area than the old one, and it has 6 rows of closely-spaced dimpled tubes and a high fin count. Multi-Wing is making me a new 9-blade adjustable-pitch high-efficiency fan to replace the clunky old 6-blade metal fan that looks like it came out of a Model T. QCC is making me another Webster YC hydraulic gear motor to drive the fan. I'm also going to buy a Derale 65k BTU transmission fluid cooler to remove heat from the engine coolant - folk who've done this say it lowers coolant temps by a few degrees. All new thermostats/seals/gaskets as well, and new Alarmstat and Low Coolant switches also. My coolant tested OK, so it should be good for a few more years - a new coolant filter will take care of it. Yes, it's a lot of work to do all this, but I don't want to Band-Aid things. A cracked head is much more expensive than what I'm doing now!

At least for Detroit 2-strokes, it takes up to 40 HP to drive the fan. There's simply no way that any electric fans can equal the CFM of the stock hydraulic or mechanical system. Maybe folk with 4-stroke engines can get away with electric systems, but I cannot!

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Old 08-02-2016, 12:21 PM   #22
Bus Geek
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Join Date: Mar 2011
Location: Houston, Texas
Posts: 7,050
Year: 1946
Coachwork: Chevrolet/Wayne
Chassis: 1- 1/2 ton
Engine: Cummins 4BT
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One of the main issues with RE buses seems to be (and has been much discussed here) the inherently poor airflow to the cooling system. I would think that any improvement there would also yield better results.
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Old 08-02-2016, 11:01 PM   #23
Join Date: Jul 2016
Posts: 54
Originally Posted by cadillackid View Post
you are also running a smaller engine and a smaller bus too... your radiator size ratio to engine size will be high compared to an RE bus or esp the 'DT' conventional busses.. the 'DT' conventionals have half the grill area as the turbo cooler and half as the radiator as opposed to a stacked position like most turbo-charged vehicles.. the result is very low radiator area / engine size ratio so they rely on the fan to do a lot of the cooling esp in hard pull situations... at idle or around town my fan clutch's low-speed constant is pretty much enough to always cool the bus unless im doing a ton of stop / heavy accelerate, stop, etc.. like stop and go traffic where the traffic goes from 0 - 35 - 0 - 35 etc..

electric fans will easily cool a very ;arge bus when the speeds are constant at a low level.. or I should say engine loads not speeds...

but pull a mountain pass where your foot is to the floor and the engine is under full load slowed below governor RPM... thats where you make heat... lots of it.. if you have a Huge coolant volume that can absorb that heat then you would be fine as your fans can remain on high speed aftyer the engine loading has ceased.. the cooling system will dissipate more heat than is being produced until the temperature is back to normal.. but if your cooling system isnt large enough to absorb that load, it relies on the ability to dissipate all of the heat produced as it is produced..

I dont know what the engineers used for numbers and capacities when designing the RE busses from the factory... or the conventionals.. but I do know from having a bad fan clutch that always stayed at a constant 300 RPM on my DT360 conventional is that it stayed at 195 or below most of the time until I got it on the highway or in stop-go traffic then it warmed up.. It needed more cooling than it was achieving some of the time..

Tango's bus is custom and so the cooling system for it must be designed according to the custom design.. and I venture to say the radiator cvolume will be somewhat small just because of size restraints.. and then rely on fans to dissipate the heat as needed...

its my belief that cummins engines tend to run cooler because their torque curve is pretty extreme at lower RPM's allowing the engines to "unbury" themselves pretty easily from being Lugged.. Lugging any engine will make tons of heat... alas why gasoline engines detonate or "ping" at Lugged low RPM's.. the cylinder head temperature are quite high during that timeframe..

Im all about electric fans in general... ive used them in most every hotrod i ever built with great success.. but I also had nice big aluminum radiators where I had high radiator volume ratio compared to engine size..

Generally manufacturers design their system based off theoretical numbers, then hook it up to a load, at given ambient temperature and humidity then measure the time to boil. Then they get an efficiency number and resize the system to allow for the <100% efficiency.

Which is great for a volume vehicle but not much help for one a one off vehicle.
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Old 08-02-2016, 11:11 PM   #24
Join Date: Jul 2016
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Originally Posted by Tango View Post
One of the main issues with RE buses seems to be (and has been much discussed here) the inherently poor airflow to the cooling system. I would think that any improvement there would also yield better results.
The rear radiator flows better when there's a vacuum behind the bus, the exit grill and airflow from under the bus have a major influence on when the effects kick in.

for low speed The grills top edge of the exit opening needs to be higher than the radiator inlets. Hot air rises so at low speed engine bay hot air flows out where? Some manufacturers struggle with the concept some don't.
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