With about a 4.8/1 reduction to the prop??
--
We have met the enemy and he is us-- Pogo
Anyolmouse
193 HP ??? Are you positive about that number? I would like to see where
that number came from, if it is available on the net, if you wouldn't mind.
If it is correct, that should do rather nicely. People have flown BMW bike
engines in the past. I believe that most of the successful ones have used a
different gearbox to reduce the prop RPM. Seems to me that I remember that
they adapted a Rotax gearbox to the job, but I doubt that there are any
Rotax gearboxed that could handle 193 HP.
--
Jim in NC
What kind of TBO is expected @ 12,000 rpm?? Some guy who has been playing
with engines for quite awhile has a rule of thumb that says 4500 is a kind
of mark for piston engines beyond which the durability starts decreasing
more rapidly??? I haven't double checked this, but it makes some sense that
the faster the piston engine spends the quicker it wears. There is several
projects using the Yamaha 4stroke snowmobile engine that turns up around
12,000 for it's hp. Data should be available soon on their durability...
Here in Germany we do have this BMW conversion ->
http://www.takeoff-ul.de/pdf%27s/Description_TAKEOFF_engine_02-2006.pdf
but those numbers are far away from 193HP (112 Nm, 12,000rpm).
KH
yes, but that one is much heavier only half the HP. Here is a press release
http://www.autoblog.com/2008/04/17/officially-official-bmw-s-1000-rr-race-bike/
yes, but that one is much heavier at only half the HP. Here is a press
release:
http://www.autoblog.com/2008/04/17/officially-official-bmw-s-1000-rr-race-bike/
I'd make a great SLA powerplant - as would other 4-cyl motorcycle
engines.
To answer other posts in this thread:
How long would a 12,000 RPM engine last?
Longer than a Lycoming. These engines are bulletproof.
They get their amazing power-to-weight ratio by being a high revving
engine. Trying to get the same power from a slow revving engine would
cut engine life since the bearings would have to handle far higher
torque.
Yes, you would need approximately 5:1 gear reduction but that's well
within the range of a single stage planetary gear set. Would it last
at thst RPM? Why not? Motorcycles have gears.
Like all engine conversions, it's all in the details. Do the
engineering right and it'll work fine.
true for cast-iron cylinder barrels, not true for diamond-like hard
modern coatings.
here's a pic of the engine:
http://www.ph21.de/guest/1000RR.jpeg
> What kind of TBO is expected @ 12,000 rpm?? Some guy who has been
> playing with engines for quite awhile has a rule of thumb that says
> 4500 is a kind of mark for piston engines beyond which the durability
> starts decreasing more rapidly???
It's not the rpm but the piston speed which cause wear.
Bikes engines have very slow piston speed.
The challenge is the PSRU.
At this time, nobody built an alternate engine lighter than an
aircraft design engine.
--
une tᅵlᅵ qui s'ᅵteint et c'est un cerveau qui s'ᅵveille
Philippe Vessaire Ò¿Ó¬
>>At this time, nobody built an alternate engine lighter than an
>> aircraft design engine.
>>
>>
> are you joking? 193 HP @ <60 Kg that is turbine land.....
Rendez-vous when this engine will fly....
At this time, yes, it is jokes.
This BMW engine is not easy to use, it'built on the same sheme than
japenese engines.
Not sure about the BMW but most of these motorcycle in-line 4's have a
separate cylinder block and a split crankcase a la Lycoming/
Continental. All the expensive, hard to reverse engineer, power
tricks are in the cylinder block and heads.
So, learn about metallurgy and CNC machining. Make a custom crankcase
and crank for two in-line 4 blocks. Presto! A silky smooth, liquid
cooled, opposed 8 cyl 300 HP airplane engine. The motorcycle-type
balanced crank throws eliminate a need for a flywheel and the 5:1
planetary PSRU fits in the nose case.
2.0 liter is probably overkill so look for a 500cc in-line 4.
Peter
How many engines have you built and flown?
Yes, you would need approximately 5:1 gear reduction but that's well
within the range of a single stage planetary gear set. Would it last
at thst RPM? Why not? Motorcycles have gears.
Like all engine conversions, it's all in the details. Do the
engineering right and it'll work fine.
**********************************
Motorcycles do not run wide open in second gear for hours at a time, either.
Motorcycle gearboxes that have been used for prop speed reducers have nearly
all failed in short amounts of time.
I agree. The devil is in the details, and it is tough to get it all right.
--
Jim in NC
Peter
Bellt drives do just that.
I've re-built and flown a lot of aircraft engines - including an
Allison V-1710. I've also built a lot of racing engines for both cars
and motorcycles. I understand the good and bad of each.
Yes, but whenever a mechanical engineer needs gear reduction that
stands up to abuse they usually select planetary gear sets.
Planetaries are the smallest, lightest and strongest gears available
due to the large number of engaged gear teeth. Look inside an
electric drill or an automatic transmission.
Belts and spur gears may be useful when you need to raise the thrust
line in addition to slowing prop rotation.
Bingo !!!!!!!!!
> Bellt drives do just that.
Indeed, and they would be my favored means of PSRU. With this case, we are
talking about needing between a 4:1 or 5:1 reduction. That would make for a
mighty big big pulley. ;-)
--
Jim in NC
5-1 ,,,, Geez, that ain't no pulley... Thats a spinner with
grooves... <GG>
Yes, you would need approximately 5:1 gear reduction but that's well
within the range of a single stage planetary gear set. Would it last
at thst RPM? Why not? Motorcycles have gears.
Like all engine conversions, it's all in the details. Do the
engineering right and it'll work fine.
Yes, you would need approximately 5:1 gear reduction but that's well
within the range of a single stage planetary gear set. Would it last
at thst RPM? Why not? Motorcycles have gears.
Like all engine conversions, it's all in the details. Do the
engineering right and it'll work fine.
Nobody in this thread is suggesting using motorcycle gears. I
suggested a designed-for-purpose planetary PSRU. The point was to
suggest that "gears" (Generic) could stand the RPM.
However, it's worth noting that some motorcycles use spur gears
instead of a primary chain between the engine crank and the input
shaft of the transmission. These ~3:1 gears carry 100% of the power -
100% of the time.
Yes, building an engine is tough. So is building an airplane. Both
require a long learning curve.
As I understand it, it's the inertia of the propeller that is the
problem. With a gear-driven PSU there is no damping element between the
crankshaft and the propeller. With a motorcycle the rear wheel has much
lower inertia plus there is the clutch that can offer some dampening.
Older BMW motorcycles had a spring-loaded dampening element in the
driveshaft.
There are lots of opinions about this. Look for successful PSU designs
that have many hours on them.
Jim
Molt Taylor was right. It's really hard to make a PSRU work well on
any engine with less than 8 cylinders. That's one reason why I
suggested fitting two small displacement, 4-cyl blocks together to
make a flat-8.
You're also right in saying that a 5:1 belt or spur gear system would
be weak and why I suggested a planetary gear set in a nose case.
These gears could be several inches wide to provide enormous tooth
contact area for strength. If they were helical cut gears, the "lash"
could be very small so they would run very smooth and quiet without
the "hammering" from power pulses.
Such a planetary PSRU would be very small, relatively light and
enormously strong. Which is why they were the gearing of choice for
all large radials.
> Molt Taylor was right. It's really hard to make a PSRU work well on
> any engine with less than 8 cylinders. That's one reason why I
> suggested fitting two small displacement, 4-cyl blocks together to
> make a flat-8.
A six cylinder in row or any engine with balance shaft may do the job.
Or, better, a Wankel....
I agree with the planetary gear (C6 from Ford transmission ?)
The chalange is always the dynamic comportement, vibrations may
cause severe overloads.
There are planetary gear sets from every major auto maker in the world
so there are hundreds to choose from. The drag race guys sell beefed
up planetary units in any ratio you can think of.
I was thinking of 8 cylinders for another reason. It's very hard to
see how two spark plugs could fit in a cylinder head with 4 valves and
two overhead cams. A second strategy could be to run 4 cylinders with
one ignition system and the other 4 with a 2nd system. If one failed,
the engine would still run on 4 cylinders albeit with only ~30% power,
but that might enough to get me to an emergency landing field. A 6
cyl running on 3 might not.
> It's very hard to
> see how two spark plugs could fit in a cylinder head with 4 valves and
> two overhead cams.
Check Mercedes engines: they have 2 spark plugs per cylinder
from 10 years either on V6 or V8 or V12...