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Roof-mounted vs. rear-mounted LNG tanks


ABQ RIDE

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I was wondering, does anyone know what are the advantages and disadvantages of using roof-mounted vs. rear-mounted LNG tanks? New Flyer uses roof-mounted while NABI and ElDorado use rear-mounted.

Which has me also wondering, if Gillig wins the City of Phoenix contract (which includes diesel and LNG buses), will Gillig use roof-mounted or rear-mounted LNG tanks? If I would guess, they would use roof-mounted, since rear-mounted tanks would require a rooftop HVAC which Gillig doesn't seem to like.

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OCTA NABI 40LFW LNG (Rear Mounted)

http://farm5.staticf...b4f555df8_z.jpg

Santa Monica NFI L40LF (Roof Mounted)

http://farm8.staticf...12f7a89dd_z.jpg

You meant LNG tanks, right?

Yeah thats the one.

I also want interior pics please and thank you.

I can only imagine that roof mounted would be more accessible for maintenance, let alone its farther away from the main heat source, aka the engine. The bus would likely be more balanced with it centered on the roof anyways.

This is just like, my opinion though. Not like I know much about anything mechanical anyways.

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Yeah thats the one.

I also want interior pics please and thank you.

I can only imagine that roof mounted would be more accessible for maintenance, let alone its farther away from the main heat source, aka the engine. The bus would likely be more balanced with it centered on the roof anyways.

This is just like, my opinion though. Not like I know much about anything mechanical anyways.

There's not much diffrence inside for both, except the NABI has a plain wall at the back where the HVAC is supposed to be at (Unless you're willing to see a Los Angeles CNG version of the NABI interior, http://farm9.staticflickr.com/8146/7168582942_d9132ffcef_z.jpg)

What I do know is that OCTA & Santa Monica NABI's (they have them too http://farm7.staticflickr.com/6084/6055862803_bddb8fd2c0_z.jpg) is that they are having problems with them (idk about Valley Metro) although I have no idea what the problems are

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LNG doesn't take up that much space, think of it like Diesel

Yes but LNG has a lower calorific value than that of diesel. Say in theory one bus has a 100 Gallon tank of diesel and another has a 100 Gallon tank of LNG. The diesel bus will go much further on that same volume of fuel. If the LNG bus has a smaller tank than that of a diesel it must be a fairly low range vehicle... having a roof mounted tank gives all that much more than having a teeny tiny tank in that small space above the engine. Logistically, I find LNG far inferior to that of diesel, but for the sake of the topic the roof mounted tanks are a better design.

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Also, another difference between the Valley Metro and OCTA/Big Blue Bus NABI LNGs is that the Valley Metro buses have Cummins C8.3G/C Gas Plus engines, vs. Detroit Diesel Series 50G engines on the OCTA and Big Blue Bus NABI LNGs. The DD 50G is a slightly larger engine than the Cummins C8.3G/C Gas Plus.

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Also, another difference between the Valley Metro and OCTA/Big Blue Bus NABI LNGs is that the Valley Metro buses have Cummins C8.3G/C Gas Plus engines, vs. Detroit Diesel Series 50G engines on the OCTA and Big Blue Bus NABI LNGs. The DD 50G is a slightly larger engine than the Cummins C8.3G/C Gas Plus.

0.2L displacement difference will not really make any sort of difference... Let alone that S50G will be working harder anyways.

EDIT: I think you may have been refering to the physical dimensions then yes the S50G is a taller engine.

Edited by 306 Carlton
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EDIT: I think you may have been refering to the physical dimensions then yes the S50G is a taller engine.

That's the reason why the OCTA/SM NABI's has those bumps + they have to fit that cooling system because the tanks are near the engine

That's what a ex-OCTA operator told me

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And actually, the OCTA NABI LFW LNGs have been repowered with Cummins ISL G engines. But yes, they originally had Detroit Diesel Series 50G engines, except 2102 which had a John Deere 6081 engine and 2259 which had a Cummins C Gas Plus.

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Looks to be. I see nothing that resembles any sort of fuel storage back there either...

Dan

I apoloigize for that, I put up the wrong fuel type (that picture is a MBTA NABI 40LFW CNG, not LNG) I have asked a friend if he could provide me a photo of the correct bus

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