Rolls Royce Turbo Jet Engine for Blue Birds

[orbitalsolutions]

Hello Jeff,

Thanks for the power/weight ratio numbers. They are along the lines
I suspected. Your informed posts are always a pleasure to read.

Now I know, for sure, why it is better to ride in a bus than on a
bicycle :-)

Seriously, I don't want to give anyone the impression that drive-
line retarders are not useful. They are terrific devices,
especially for novice drivers, but they are not mandatory.

Of course, proper driving technique is always your best safety
percaution. If you go up a hill in 2nd gear, than come down the
hill in 2nd gear. Keep an eye on your air, and be prepared to pull
over and stop if needed to build more air pressure (I have not, as
of yet, had to do this in the 'Bird). Even if you forget to watch
the air guages, the low air audio alarm should alert you with plenty
of air to get stopped, providing you are not driving at too fast a
speed.

That's the way I drive the 'Bird, so if you see me coming from
behind get the hell out of the way !! ... LOL

It would be no fun to have the spring brakes deploy with the bus at
speed. No fun at all. If you have never driven a heavy truck before
a retarder should make the experience easier and probably safer as
well.

-James
78FC33SB
LasVegas NV






--- In WanderlodgeForum@yahoogroups.com, "Jeff Miller"
wrote:
>
> On the way up, it's about power/weight ratio (comparing different
> year 'Birds). My '77 FC31 weighed in around 23,000lbs with all
tanks
> full. With several engine upgrades, and 4.63:1 gears, it would run
> well on the flats at 75mph or better. Slight inclines would slow
it
> down, but doing some simple calculations showed that it added only
> minutes to each day's drive to slow a few MPH on the climb.
>
> Coming down the hills was different. In a diesel rig, you CAN NOT
use
> the brakes to control speed. If you're having to use the brakes to
> keep your speed down, you need to slow down and downshift. This
makes
> the retarder a huge advantage plus the safety of being able to
slow
> down without using the brakes as the grade changes. This is why
Mr.
> Cummins invented his Jacobs Brake in the (?) '30s? I believe it
was a
> runaway when he was driving into Wolf Creek Pass or something like
> that, it's been a year since I've heard the story.
>
> On a NA engine you lose 3% of your horsepower for every 1,000'
above
> sea-level. At 10,000' altitude, you have likely lost about 63hp,
or
> have around 147hp remaining. Since much of the horsepower is used
for
> frictional losses in the drivetrain, engine accessories, rolling
> resistance, aerodynamic drag, ... this probably leaves enough
power
> to run around 50mph on the flats and nothing for climbing until
you
> gear down, and down. With our '77 again as an example I was able
to
> climb over 10,000', but with much black smoke which had to be
> regulated by lifting the throttle so bicycles could see to pass ;~)
> The turbo burns much cleaner at altitude and maintains most of its
> rated power up there.
>
> Our '77 was 210hp originally, and 23,000lbs. Our '84 was 250hp,
and
> 33,000lbs. The '82-up coaches are heavy and need the turbo. Still,
> look at the numbers, the '77 was 109.5lbs per horsepower, the '84
is
> a much lower-performing 132lbs per horsepower. This gave my '77 a
> performance advantage at low altitudes over the much heavier '80s
> models even with the Na engine. At 10,000' however, the '77 would
> have to pull 156.5lbs with each horsepower, so the advantage of
the
> turbo is back.
>
> Our '88 FC was more powerful still, with the 300hp and around
> 33,000lbs, its power/weight ratio is around 110lbs/hp so almost
> identical to the '77 (at sea level). The overdrive transmission
and
> high-altitude performance of the turbo (and retarder) make it a
> rocket in comparison though.
>
> The calculations are a little more complex than all of this of
> course, but the basic idea is there and FCs pretty much have the
same
> aero-drag regardless of the year. I don't know if Ernie has
retained
> the hp & climbing calculation from the old forum, if not I can re-
> submit it.
>
> Turbos are good, very good. The low-boost on the 3208 road engines
is
> pretty much not going to hurt a well-maintained engine, not like
it
> does in the 380-435hp marine versions. The engine simply doesn't
wear
> out very often, it is more likely to suffer a cooling system or
other
> failure that damages the engine. Retarders are also very useful,
and
> a safety feature also. I've seen what happens when an FC driver
over
> drives his brakes with no retarder on a grade, it's hard on the
coach
> even when he's lucky (this one was).
>
> - Jeff Miller
> in Holland, MI
>
>
> --- In WanderlodgeForum@yahoogroups.com, "davidkerryedwards"
> wrote:
> >
> > Just crunched the numbers. Comparing a 210hp NA with a 250hp T,
if
> > there is a 30% loss on the NA, and none on the T, there is a 70%
> > horsepower advantage with the T at altitude.
> >
> >
> >
> > --- In WanderlodgeForum@yahoogroups.com, "davidkerryedwards"
> > wrote:
> > >
> > > The main advantage I see in a turbo is maintaining sea-level
> > > horsepower at altitude. Here in Colorado an NA engine looses
> about
> > > 30% of its horsepower going over the passes, strictly as a
result
> of
> > > the thin air. A turbo overcomes most of that loss. At lower
> > > elevations, the advantage is much less significant in my
opinion.
> > >
> > > Kerry
> > > Denver
> > >
> >
>