Electric fans vs miter box?

[Mike in GA]

 This has probanly been discussed before, but here goes... I wonder if my squirrel cage fans and miterbox could be replaced with a couple of heavy duty electric fans outide the rads on my 8v92T?  Wonder if electric could move a comparable amount of air? I gotta think the miterbox, etc. takes a fair amt of engine power.
Reaction?
Mike in GA

[TomC]

Yes this has been discussed before. 8V-92TA is THEE hardest engine to cool. You need the largest radiators, make sure the enclosures are air tight, and that the squirrel cage blowers, and flappers are operating correctly. Many disconnect and wire open the flappers. Since the 8V-92 has good thermostats, too cool isn't a problem. But the flappers do cut down on horsepower usage, since when they are closed, the blowers don't use power.

As to electric, the only buses that are using electric are the current transit buses. That's because they have big radiators, use 12 fans, and transits do stop and go that allows for cooling. On road buses will not be able to use electric because of long hill climbs during summer heat.

Just make sure your cooling system is maintained as well as possible. MCI designed that cooling system well. Course, the 8V-92TA was only rated down around 400hp. If you're bumped up the horsepower, then cooling will be taxed. Good Luck, TomC

[luvrbus]

It's hard to replace the 40hp need for the blowers with electric fans,Boomer made it work on a Eagle though with a Cummins engine, it took some engineering on his part   

[uncle ned]

Mike  Remember the two dogs story.

where on the southeast busnuts web page do i go to for sending payment for the Palmetto cove rally.

Hope to see you again but I doubt if I can bring your Honda down/  It has not been started in years.

But if you can find Captain Ron ,he might help us get it started.

Uncle ned

[bevans6]

I had an itch reading this so I did a little reading and squashed a few numbers.  If you thought the fan belt and the gearbox robbed a lot of power from the fan drive system for the engine, you'd actually be wrong.  I got to thinking about this, misremembered some rules of thumb from old engineering days, and looked it up.  All hail the power of Google...

If you assume you need to move a certain amount of air with a fan, and the fan efficiency itself remains the same (I actually have a suspicion that the squirrel cage fans that the MCI has are quite efficient, comparing to other fans and arrangements) then you need the same actual delivered horsepower to spin the fan.  Let's say that is 10 hp for arguments sake.  A fan belt drive system is 98% to 99% efficient at transferring power, and a 1:1 right angle bevel gearbox is also about 98% efficient.  That makes the fan belt/gearbox system 96% efficient at driving the fan, so to input 10 hp to the fan you draw 10.4 hp from the engine.

Now lets do electric.  You already have an alternator just sitting there, on a bus it's either fan belt driven or planetary gear driven.  Lets assume they are both 98% efficient (I think the planetary drive is actually a little less but didn't look it up) but as it turns out we can ignore drive efficiency.  An automotive alternator has an efficiency curve that typically peaks at around 60%, so lets assume we are running a peak efficiency (we aren't, actually, in most systems).  DC motors are a lot more efficient than AC motors, they peak at around 80% efficiency.  So to get our 10 hp input to the fan, we need to draw a tad under 21 hp from the engine.  So an electric fan setup is just about exactly half as efficient as a mechanical system.

Now lets talk amps.  If we actually need 10 hp input to the fan, and need to generate 21 hp to obtain that (this already takes into account efficiency of the alt and motor) then 1 HP = 746 watts, 21 hp = 15.6kw, which at 28 volts DC is 555 amps.  Which is an unlikely amount of power to get from an alternator on a bus.

Edit: I got this wrong, the electric motor at 80% efficiency would need to pull 9,325 watts out of the alternator, which is only 333 amps at 28 volts.  The alternator loss jumps this back up to the 15.6 Kw out of the engine, back to the 21 hp.

So I thought I would look up the equivalent for a hydraulic pump system, since I know some guys who converted to hydraulic pumps and motors for their MCI cooling system.  A hydraulic pump can be up to 95% efficient (remarkably close to a fan belt and a gearbox), and around the same efficiency for a hydraulic motor, so hydraulic is a good choice if you can't use a fan belt.  It would take around 11 hp to drive our notional 10 hp fan using a well engineered hydraulic system.

Now I picked 10 hp to make the math easy, you can easily up or down scale if you know your actual fan HP.  Clifford said 40 hp, I have no idea but I've read similar numbers.  I also have no idea how re-engineering the radiator system would affect fan HP or CFM requirements.  But I do think the numbers are interesting.

60 degrees on my screen porch as I write this, which is pretty flipping odd for the last day of February in Nova Scotia.

Brian

[brmax]

Hydraulic! good idea I think, many construction pieces have implemented them, and bumped up more usage since ecm capabilities to turn them on and off at some desired temps and heck even more designs like hi speed during a certain gear and such, kinda relates to our on road vehicles have been doing with electric /air  solenoids clutch fans. I guess a big kicker is putting them anywhere you can fit them, so give an engineer options and only good things can be the outcome, versus asking them how cheap can we go 
Have a good lunch guys
Floyd

[Oonrahnjay]

Hydraulic! good idea I think, many construction pieces have implemented them, and bumped up more usage since ecm capabilities to turn them on and off at some desired temps and heck even more designs like hi speed during a certain gear and such, kinda relates to our on road vehicles have been doing with electric /air  solenoids clutch fans. I guess a big kicker is putting them anywhere you can fit them, so give an engineer options and only good things can be the outcome, versus asking them how cheap can we go 
Have a good lunch guys
Floyd

     They are fitted on Cummins ISC engines,  Big and heavy but they sure seem to do the work right.

[Iceni John]

Find a hydraulic setup from a school bus in a wrecking yard  -  cheap and easy.   I have a two-speed hydraulic fan and it works well, running off the same pump as the steering.

John

[luvrbus]

Caterpillar has a good chart for hp used to turn a fan it's interesting ,only bad thing about the hydraulic fans is the heat the system generates over the course of a day.I am speaking of the hydraulic fans on construction equipment all mine would heat.I don't know for sure how one would work in bus on the highway.They didn't work that well on a Eagle bus   

[Iceni John]

Mine has a small heat exchanger outside the radiator for all the hydraulic fluid, including the steering's fluid.   When I was testing the fan a while ago I was running it at full speed at high idle (Wow! Talk about a leaf blower!), and after a few minutes the heat exchanger was barely warm.   Mine goes to full speed at 195 degrees and back to half speed at 189 degrees.

John

[brmax]

Sounds pretty cool John, what sizes we talking here for some of this exchanger stuff, again like the idea and want to add whats mentioned this is another heated source needing cooled.
your workup is interesting, I got the ears on
good day
Floyd

[kyle4501]

where on the southeast busnuts web page do i go to for sending payment for the Palmetto cove rally.

http://www.sebusnuts.org/HomePage.html 
on the right side - look for "Spring Rally 2016 (Palmetto Cove, SC)" pick the 'add to cart' button.

[Scott & Heather]

Sorry this is so long but in light of the above conversations, is this article a bunch of bunk?



"Hot summer days like the Portland-area has experienced this week require public transit buses to do more than crank up the air conditioning. Extremes of summer heat - as well as the hard cold of icy winters - force big diesel engines to work harder and burn more fuel to maintain their optimal operating temperatures.
That means more diesel fuel consumption and emissions that pollute the region's air and contribute to global warming.

TriMet, the agency with Portland's mammoth bus fleet, has tried for years to improve efficiency by reducing idling time, improving maintenance, and keeping tires inflated. But the agency has also been quietly stepping out to help pioneer a new, efficient cooling technology first developed for use in Army tactical vehicles.
Here's the concept: Pull out the engine's mammoth hydraulically driven cooling fan and replace it with eight small electrically powered fans that turn on discreetly, only when and where needed.

Here's the benefit: TriMet has found it can save about 700 gallons of fuel a year per bus. That can add up when multiplied. In the mass transit world, where thousands of diesel buses lurch from block to block burning fuel at a handful of miles to the gallon, even a slight gain in energy efficiency can be significant.

The new hardware has in recent months been retrofitted upon dozens of Portland-area bus engines. In the coming weeks, the last of a targeted group of 66 TriMet buses will be converted.

The agency estimates it will save $138,000 a year in diesel across the fleet and keep 512 tons of carbon dioxide from the atmosphere annually.

TriMet's partner is Engineered Machined Products, Inc. of Michigan.

"If you can limit the amount of parasitic load on an engine you not only save fuel but you pollute less," says Ralph Bedogne, vice president of EMP Corp. "When you don't burn fuel, you don't burn emissions."

Installed as a retrofit, the systems cost about $15,000 - or about half that when they're installed into a new bus at the factory. Savings on fuel and maintenance recoup the cost of installation in three to five years for the more expensive retrofit, depending on diesel prices.

"We wanted to demonstrate some environmental leadership and save some money by reducing fuel consumption," says Eric Hesse, TriMet's strategic planning analyst.

Dozens of transit agencies across the country are now retrofitting their bus fleets with the cooling systems or ordering new buses to have them pre-installed - sometimes with federal economic stimulus money. TriMet and EMP shared a U.S. Environmental Protection Agency Clean Air Excellence Award for developing the device.

EMP calls the technology a "minihybrid thermal system" -a complicated name based on a relatively simple idea.

Big diesel engines found on most of TriMet's fleet normally operate at up to 197 degrees. On warm days, that can easily rise to more than 205 degrees - beyond the most efficient temperature range.

The conventional buses TriMet runs have large hydraulic fans in the back, cooling the engine under the buses' rear seats. That's where the problems begin.

The fan - about 2 1/2 feet in diameter - sucks hydraulic fluid constantly. Depending on the size, a bus could carry 300 to 500 pounds of fluid just to keep the fan going.

The fan comes on full blast when any part of the engine or the coolant gets too hot or cold. It runs on an alternator greased with oil, and prone to occasional leaks.

The fan uses about 45 horsepower - about 16 percent of the peak output of TriMet buses' 280 horsepower engines.

The EMP system replaces the hydraulic fan with a set of eight smaller fans that operate independently of each other. They only turn on when the area near that fan needs to be cooled. And there's no need to carry hundreds of pounds of hydraulic fluid.

"It's smaller and it's cheaper," Bedogne says.

The EMP system also relies on a more efficient, brushless alternator, that puts out more electricity and uses about 10 horsepower. It also uses air rather than oil for lubrication -avoiding a common source of leaks, maintenance problems and even fires.

"They're maintenance free, basically, which is cost savings," says Don McInnis, maintenance supervisor at TriMet's Center Maintenance facility in Southeast Portland.

The technology wasn't initially intended for buses.

EMP had been testing the cooling devices on U.S. Army personnel carriers when Bedogne met a TriMet maintenance manager in 2005. Bedogne was explaining the technology at a conference in California sponsored by CALSTART, a non-profit that promotes energy efficiency in transportation.

"Could this be put on a bus?" then-TriMet manager Tony Bryant asked.

Intrigued by the potential new market, EMP's Bedogne asked TriMet for help testing the new gadgets.

They sent two TriMet buses with the electric cooling systems to the Arizona desert for a one-week workout.

"We gave it a pretty crazy run, really to try see what it would do in steep grades," Hesse says. "Part of this was to demonstrate for the industry that this would work in extreme conditions such that a variety of agencies could be attracted to it."

Electric-diesel hybrid buses offer an alternative way for transit agencies to boost fuel efficiency, but those buses often cost double the $350,000-$400,000 price of a new diesel bus. The Federal Transit Administration requires agencies to keep old buses for at least 12 years, and many of TriMet's last 20 years.

For its help in developing the product, EMP gave TriMet an initial 25 cooling systems at a steep discount and helped with some technical know-how. It sent EMP engineers to Portland often during the initial test period, and continues to offer TriMet discounts and technical help.

TriMet doesn't share in any of EMP's profits, but Hesse says the agency's role as the first to test the technology will give it an edge in competing for government grants.

TriMet is applying for a federal economic stimulus grant that would help pay for a $3 million project to retrofit 154 more buses with the devices and gather data for a CALSTART study on the fuel efficiency results.

"It's still a pretty quick payback, depending on the cost of diesel you're estimating," Hesse says. "We are seeing this become an industry standard."

Taken from "Oregon Live.com"




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[Iceni John]

As Tom C says, electric fans work on transit buses only because of their frequent stops.   Our local transit authority here has some new CNG-fueled bendy buses, and they have a lot of electric fans for their radiators.   One thing I noticed  -  in hot weather those fans are running at full speed even after the bus comes to a complete stop, and they do this sometimes for a minute or so before they slow down.   That tells me that they are only barely able to keep up with the heat load, and if the bus ran for longer between stops they possibly may be unable to cope.   OK, it's generally hotter here than Portland OR, but I'd be curious to know if any transit buses in Las Vegas or Palm Springs or Phoenix have electric fans, and how well they cope with 110-plus temperatures in the summer.

John

[Lee Bradley]

and those are newer buses with 4 cycle engines that are much easier to cool than the older 2 cycle Detroit Diesels. Probably their biggest cooling load on those transit buses is the transmission.