Who knows about coaches?

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Originally Posted by Brian Hjelm

Ian, what does a bus weigh? What axle ratios do they use? O/d or direct?

1500 rpm and 3.7 overall gear ratio is near spot on 80 kph and 1900 rpm gives 100 kph. Then if you turned the wick up to 2100 you would hit 108kph.

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The standard setup (way 90%+ left the factory) for a Landseer or Tourmaster was about 1700rpm for 100km/h, with a 7 speed you could drop a gear at 95 while climbing. (I can’t remember ratios, it’s a long time ago)

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Originally Posted by V8Ian

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I was hoping to achieve 10+mpg from a 6V92 at at least half of the weights I used to gross.

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10mpg is near 4km/L which would be half the fuel these vehicles used in commercial operation @ 19t loaded - driven hard with no consideration for fuel. If you are raising the roof the aero will increase fuel consumption. If you are towing fuel consumption increases. I would think a fitted out motor home would be a bit lighter but still pushing 15t +trailer/car (700kg + small 4x4 = 2-2.5t). If memory serves me the Landseers fitted with 8v92t used bugger all extra fuel, guys always reported that they just did it so much easier.

Obviously you have looked at whats out there – seems like a few with all the body work done ready for internal fitout, might be way to go.

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Originally Posted by Brian Hjelm

106 kph @ 1500 based on 504 tyre revs per mile. That combo gives an overall ratio of 2.7:1. I would be concerned about the ability of a 300-335 hp engine to pull that gearing on any circumstances but dead flat and no headwind. You would probably have the pedal on the metal in any other circumstances. What weight do you anticipate? Buses have large frontal area. All these criteria come into the equation. The relatively low tare of a bus might be the saving grace here.

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I have been advised by many, both here and on the road that the tag is superfluous, ergo the maximum GVM would be 22.5 tonne. Using Harlie's figures, which are very close to my roughly calculated guestimate, 15 tonne is close to the mark. Add 5 tonne for a trailer and I still have a relatively light GCM of 20 tonne.

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Originally Posted by V8Ian

I have been advised by many, both here and on the road that the tag is superfluous, ergo the maximum GVM would be 22.5 tonne. Using Harlie's figures, which are very close to my roughly calculated guestimate, 15 tonne is close to the mark. Add 5 tonne for a trailer and I still have a relatively light GCM of 20 tonne.

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Ian, here are a couple of handy formulae.

Road Speed =

(Engine Revolutions per Minute x 60)
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(tyre revs per kilometre x overall gear ratio)

Horsepower requirement is a function of gross weight, frontal area, and road speed. The total horsepower required is the sum of three individual requirements. (1) Rolling resistance horsepower. (2) Grade resistance horsepower. (3) Air resistance horsepower.

Using the tables in Motor Truck Engineering by James Fitch and assuming 100 kph, 1st class highway, 1% grade, 20 tonnes gross, 96 sq. ft frontal area, we have:-

rolling resistance hp - 80.4
grade resistance hp - 72
air resistance hp - 111
required net hp - 262.4

Engine driven accessories consume from 12 to 25 hp and 17 is used as a benchmark for calculations unless a particularly heavy draw is made by certain accessories like two air compressors not one, particularly large output alternators and a/c compressors. So add 17 hp to that and you require 280 hp to maintain 100 kph on good level road. At 110 kph the requirement rises to 378 hp. This is why the guy who commented that the 8V92TA's "did it easy" was on target. The smaller engines are going flat out, full load where the 8V at 435 hp had plenty in reserve.

Ian, on thinking about it, perhaps a two axle bus with an 8V92TA would be the way to go. Those 8V's are economical where they are not being used continuously or nearly so at full load. I don't think from my experience of operating them that they would use any more than a smaller engine of any type that has the hammer down most of the time. And, you are only running 20 tonnes not line haul at 43 or more. On the shuttle we ran to a schedule of 14 hours Brisbane-Sydney New England Highway and Putty Road. Could do it in 12 hours if necessary without having to push too hard.

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Originally Posted by Brian Hjelm

Ian, on thinking about it, perhaps a two axle bus with an 8V92TA would be the way to go. Those 8V's are economical where they are not being used continuously or nearly so at full load. I don't think from my experience of operating them that they would use any more than a smaller engine of any type that has the hammer down most of the time. And, you are only running 20 tonnes not line haul at 43 or more. On the shuttle we ran to a schedule of 14 hours Brisbane-Sydney New England Highway and Putty Road. Could do it in 12 hours if necessary without having to push too hard.

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They were 'interesting' days, sometimes I miss them. :angel:

I remember Rex Laws and Redline Coaches :o redline by name and that was where the tacho sat! and the little red LOW Vacuum light on :eek:

In later years I had need to travel on VIP one driver buses,Syd-Bris O/night about 100klms north of Coffs Harbour the bus started to wander as the driver dozed off, a passenger got him to stop, and asked if anybody had a bus license, nobody had but 2 of us had truck licenses, so we shared driving until Ballina, the first time I had driven a full air braked vehicle, being used to Vacc over Hydraulic, a replacement driver was waiting in Ballina.

when we moved up here to Qld I started driving School Buses, Bedfords SB's BLP's Vam's Vacc over Hydraulic and full air manual syncro,manual crash, and Allison autos.still like a nice smooth crash box like the old Commer CBEW with rear Perkins 6-354 :) 100kph with a full load of school kids on,it was Vacc over Hydraulic.could do 5 close stops before low Vacc light and buzzer came on, a mostly flat run ;)

My favourite was an SB3 with a 330 Diesel was originally Kirklands Coaches,was a petrol 300 but converted to diesel,used to do Lismore area,I can still remember seeing Alstonville on the destination scroll :) it is now my ex-bosses motor home,it had a low ratio diff in it for climbing the hills an doing stops, flat out empty 51MPH,full load 80 primary's 51MPH :D loved it 4spd J2 syncro box smooth as.vacc too.

cheers

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Originally Posted by Brian Hjelm

Ian, on thinking about it, perhaps a two axle bus with an 8V92TA would be the way to go.
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Good luck find one of those. There was several 2 axle Landseers built around 1990. They were fitted with 6v92t & 6speed Spicer or 6 speed ZF syncro, no toilet and shorter at 34-35ft. Loaded weight of 4t lighter made them a bit of a rocket.

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Originally Posted by V8Ian

I have been advised by many, both here and on the road that the tag is superfluous,
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Don’t rule out a tag axle completely. Down side is extra weight, and dragging in parks. But the tag adds a LOT of stability.

Remember a coach has similar windage to a fridge semi which has 6 axles, I can report that 2 axle coaches (even the otherwise identical Landseers) are quite exciting at highway speed with strong winds, they really get pushed around.

Also coaches don’t really make good tow vehicles due to basic geometries. They have a BIG rear overhang (distance from axle to tow point) and were never balanced for any significant ball weight. The “pie wagons” that Greyhound used to tow for freight and companies like Downunder Tours tow for camping gear weighed about 4t and believe me, you really knew it was there, I would hate to tow one with a 40’ 2 axle coach. If it was me towing 5t, I would want the extra axle for towing and highway stability.

Denning fitted a dump valve as an option that wound deflate the tag bags completely so it was only axle&wheel weight on the tag tyres for maneuvering, (it was actually for getting weight on Drive when bogged), easy retrofit to any air suspension to get this functionality. Later came the units that lift the tag off the ground.

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Originally Posted by harlie

Good luck find one of those. There was several 2 axle Landseers built around 1990. They were fitted with 6v92t & 6speed Spicer or 6 speed ZF syncro, no toilet and shorter at 34-35ft. Loaded weight of 4t lighter made them a bit of a rocket.

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Plenty older ones with 8V71N's though and a dead easy conversion to a turbo 92.

I wonder what happened to the 8 x 4 touring coach being built by George Roman at his Carina home? It was to have an 8V92TA. I couldn't hazard a guess at how many years it sat there being slowly constructed as money became available.

Ian, my brother-in-law has a converted coach for sale. May I PM you with some information about it?
In the late '70s I was going to build a "café-racer" type motorcycle. When I did the costing it turned out to be cheaper and quicker to buy a new motorcycle of a similar type, which I did (Yamaha SR500, great bike except the brakes were absolute rubbish).

wouldn't you be better getting a 6v92 for conversion? $ spent on conversion buys quite a bit of fuel so may as well stick with the 6v92. 8v71N is a gutless dog. IMO if you want a 8V look for one of the scennars build Landseers, or McCaffertys build Landseer High Deckers, but they all have a duel tyre tag.

Anyway, how many km is this mobile home going to do in the year. If you really want a 2 axle coach get one of the day tour built MCA, Apollos ect with a little cummins or cat, you will get the 10mpg.

But there's a reason why the conversion companies are using old Landseers & Tourmasters - they were build tough, they servived outback camping tours into areas that they really should not have been. MCA (for example) were building 53 seat coaches on 2 axels that were 5t lighter than the Landseers, soon found out that they didn't last. In 1994 12 people lost their lives when 1 rolled on the Gateway just sth of Boondall because the front suspension bracket snapped of the chassis. Nation wide all MCAs were grounded until modifications were completed. At the time I was in the industry, and involved in the aftermath, everything underneath was heaps lighter.

If it was me looking for a m'home. I would go a Landseer 3 axle or if the frame is going to be rebuilt a Tourmaster (beautifull drive) for reliability and strength or my favourite for layout, a PMC Apollo High Deck with Scania K112TR that was built for Sunlinner

Another thing, most coaches have a slope in the floor under the front 2 rows. The "High Deck" versions don't, the floor is flat right to the modesty panel.