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2 Stroke VS 4 Stroke
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lstavenhagen(at)hotmail.c
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PostPosted: Sun Jan 01, 2006 6:54 am    Post subject: 2 Stroke VS 4 Stroke Reply with quote


Quote:
Men...on the 2cycle Vs 4cycle engine issure, I have been following this
thread, and
in reading I sometimes wonder if some might be confuseing...or better said,
interchangeing, the meaning of the word relilable with durability?
Working for the largest manufacturer of 4 cycle engines in the world, I
am
very familiar with the commonly misunderstood comparision of these 2
engines.
A 2 cycle can easily be built as reliable as a 4 cycle...but it is almost
impossible to build one as "durable"...I say "almost" because someone who
works for Detroit Deisel might be reading here and take issue with the
statement.
So remember in your reading of the posts...are we debateing a durability
problem..or a dependability problem. Sometimes both I think..and they
shouldnt be confused.
Could we agree that a certain Rotax 2 cycle might be as dependable as a
certain 4 stroke....but it just wont last for as long? With that might come
the admission that it wont be as "dependable" for as long......

I'll go along with this 100% - this is unquestionably true....
In fact, ironically, this is one of the main improvements in terms of
reliability of 2-strokes over the years - a very good knowledge of the
limits in terms of how long things last in the motor and what kind of
operation they're NOT tolerant of.......
This is what I mean when I say knowledge is the key to reliable operation of
any engine including 2-strokes. And the reason I can confidently say that
the Rotax 2-strokes ARE quite reliable.
For example, some operational things that tweak 2-stroke weaknesses are:
- extended full throttle operation. I.e. running at max or very near max all
the time. This is where the 300 hour TBO listed in the manual came from Wink.
The usual cause here is underpowering the airplane to cut costs - putting a
503 on a big 2-place and flying it dual a lot of the time (where really the
582 or something bigger is required). Generally, aviation 4-strokes can
handle this all the way out to TBO (some of the continental/lycoming
aviation motors are literally designed to run at full throttle just about
all the time), but a 2-stroke due to its design is simply not as durable
when run this hard.
- low MOI limits on the Rotax gearboxes, particularly the B box. Some of the
most popular props on the market (like the IVO in 3-blades and the warp
drive) are 50% or more over the MOI limits of the B box. They can take it
and regularly do, but the stresses they put on the crank and other moving
parts inside the motor and gearbox itself are outside of the design limits.
This can lead to premature damage and wear, and sometimes catastrophic
failure.
- mag end electric starters. The 2-stroke Rotaxen's weak spots are generally
the cranks (especially with the 582) and the ME electric starts can do a lot
of damage (especially the GPL starter, but even the Rotax model) - you have
that bendix flying out and smacking the starter gear which is like taking a
hammer to the edge of it. This puts a heavy side-loading shock on the mag
end of the crank, which can knock the journals out of alignment. Also, they
have to instantly get the entire moving system - crank and prop - up to 300
rpm, which puts a lot of stress on the crank (much moreso than the pull
start). You have no such problem at all on the bigger 4-strokes, since
their cranks are MUCH beefier even if they are press-fit designs.
- over or under propping. Here is where the 4-stroke shines and the 2-stroke
just makes you pull your hair out in aggravation. In particular, 2-strokes
are extremely susceptible to high-rpm/low throttle opening situations due to
their design (this leads to poor lubrication and cooling). So too small of a
load, such as a fast descent with the throttle reduced or too small/too fine
of a prop, is a hazardous situation to be in with a 2-stroke. With a
4-stroke there's no such concern at all, since the lubrication circuit is
completely independent. Just keep it below redline and you're ok basically
Wink. Overpropping is less bad on a 2-stroke but still bad since their torque
curves tend to be fairly peaky. 4-strokes - no problem or very little
problem....
Last but not least:
- simply lower TBO generally due to higher specific output, more maintenance
required. These are just facts of life of 2-stroke operation and these have
to be paid attention to. The crank seals on the Rotax simply start to leak
at 100 hours or so and there's nothing that can be done about it. They also
simply wear out faster (400 to 500 hours on the aircooled) and just simply
need to be rebuilt after that time. The 4-strokes just simply last longer,
i.e. the 912 has a TBO more than 4 times longer than the 2-stroke! That's
just a fact of life (and certainly nothing I ever debated against).
So, while these are definite limitations of the 2-stroke, they're KNOWN
limitations - that allows us to work around them and avoid the reliability
problems they can introduce.
Indeed, the most dangerous thing in aviation is the unknown. The Rotax
2-strokes aren't as reliable as they are because they're so fantastically
good quality (they're basically just beefed up snomo engines), but it's
because we KNOW so much about operating and maintaining them.
Incidentally, this is true of the 4-stroke designs as well. Knowledge is the
key there too...
Ok, nuff said....
LS
N646F
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kfackler(at)ameritech.net
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PostPosted: Sun Jan 01, 2006 8:04 am    Post subject: 2 Stroke VS 4 Stroke Reply with quote


Quote:
- low MOI limits on the Rotax gearboxes, particularly the B box. Some of
the

Quote:
most popular props on the market (like the IVO in 3-blades and the warp
drive) are 50% or more over the MOI limits of the B box.

What does this mean, i.e., what is MOI?
-Ken Fackler
Kolb Mark II / A722KWF
Rochester MI
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lstavenhagen(at)hotmail.c
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PostPosted: Sun Jan 01, 2006 8:26 am    Post subject: 2 Stroke VS 4 Stroke Reply with quote


Quote:
What does this mean, i.e., what is MOI?

Oops, sorry. MOI means moment of inertia, the rotational mass of the
prop....
LS
N646F
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jhauck(at)elmore.rr.com
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PostPosted: Sun Jan 01, 2006 9:40 am    Post subject: 2 Stroke VS 4 Stroke Reply with quote


|
| - mag end electric starters. The 2-stroke Rotaxen's weak spots are
generally
| the cranks (especially with the 582) and the ME electric starts can
do a lot
| of damage (especially the GPL starter, but even the Rotax model) -
you have
| that bendix flying out and smacking the starter gear which is like
taking a
| hammer to the edge of it. This puts a heavy side-loading shock on
the mag
| end of the crank, which can knock the journals out of alignment.
Also, they
| have to instantly get the entire moving system - crank and prop - up
to 300
| rpm, which puts a lot of stress on the crank (much moreso than the
pull
| start). You have no such problem at all on the bigger 4-strokes,
since
| their cranks are MUCH beefier even if they are press-fit designs.
|
| LS
|
LS/Gang:
What is the solution for the above? Do you think super glue would
help keep the cranks from twisting as the result of the electric "self
commencer" ???
Take care,
john h
Thinking the electric starter was one of the most significant safety
factors of the two stroke ultralight/light plane engine.............


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lstavenhagen(at)hotmail.c
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PostPosted: Sun Jan 01, 2006 3:01 pm    Post subject: 2 Stroke VS 4 Stroke Reply with quote


Quote:
LS/Gang:
What is the solution for the above?

The model "E" gearbox.
This one does the electric start the right way - it cranks the motor at the
PTO end off the drive gear. This way the inertia of the prop isn't
transmitted through the crank during starting.
More importantly, there's no side loading perpendicular to the crank due to
the hammering action of a bendix on the gear as there is on the mag end
starters.
The E box is also lighter by a few lbs and cheaper than a C box + mag end
starter...
Do you think super glue would
Quote:
help keep the cranks from twisting as the result of the electric "self
commencer" ???

Personally, I won't buy any airplane with a 2-stroke that has a mag end
starter fitted to it, unless the motor is already runout or nearly so and
needs rebuilding (new crank) anyway.
E box, though, is ok.....
LS
N646F
Quote:
Take care,
john h
Thinking the electric starter was one of the most significant safety
factors of the two stroke ultralight/light plane engine.............


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Kolbdriver(at)bellsouth.n
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PostPosted: Sun Jan 01, 2006 4:47 pm    Post subject: 2 Stroke VS 4 Stroke Reply with quote



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lstavenhagen(at)hotmail.c
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PostPosted: Sun Jan 01, 2006 5:19 pm    Post subject: 2 Stroke VS 4 Stroke Reply with quote


Quote:
Do you have data from Rotax concerning the above statement?

Most of this comes from field experience. Mark Smith, for example, is a good
source of information on this as well (he does a couple of motors a week and
is pretty familiar with this). Most guys who've done a lot of motor work
will tell you similar things.
Quote:
I find it hard to believe that the electric starter, powerful as it is, has
enough torque to twist the crank. The starter drive (Bendix) is engaged in
the ring gear before the starter motor makes one full revolution so the
engine is pretty much accelerating to cranking speed along with the starter
motor. I don't see how it is hammered.

It's the action of the starter gear flying out to hit/engage the gear that
does it. After a whole bunch of times, it eventually can do damage to the
mag end of the crank. Typically, it shows up as higher than normal runout on
the mag end.
The mag end starter thing is a lot like running the high MOI props on the B
box - kind of a crapshoot. Most of the time it can take it and there isn't a
problem. But it's still definitely a mode of operation outside the limits
and does increase the liklihood of damage.
For what it's worth, the Rotax mag end starter isn't as bad as the GPL
starter (but you're still much better off with the E box).
As for accelerating the crankshaft
Quote:
form 0 -300 rpm with the starter motor, what about 300 to 2200 when the
engine fires? Every power stroke on each cylinder also side loads the
crank
much more than the starter does.
The crank is even accelerating and
decelerating two times per revolution for an inline 2 cyl. 2 stroke.

The crank is designed to take these kinds of loads in these areas.
Quote:
As for reliability of 2 stroke engines, I have had 350 hours of reliable
service and only about 60 seconds of unreliable flying with them. (pto end
rod bearing failure at 210 hrs TTSN 582)

I've never had a mechanical failure of any kind with any of my Rotaxen (one
electrical problem with my 447 and that was it). I attribute that success
partly to, among other things, running props that meet the inertia limits of
the gearboxes I run (or using the clutch in case the prop is too heavy like
on my current plane) and not using mag-end electric starters on any of my
engines.
Also, with the E box available, I've never understood why anyone would use
anything else. It is set up the correct way, weighs less and is
cheaper.......
LS
N646F
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blackbird754(at)alltel.ne
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PostPosted: Sun Jan 01, 2006 5:20 pm    Post subject: 2 Stroke VS 4 Stroke Reply with quote


Aha......yes ..Rotax does know about the crank twist problem......My new
blue head 582 with an "E" box has the starter mounted to the gearbox and
pull rope on the mag end........I have read all of the info on the new
bluehead and ....it seems Rotax has done their homework with this new
motor....
Time will tell.............
Wayne McCullough
Kolbra 4


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lstavenhagen(at)hotmail.c
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PostPosted: Sun Jan 01, 2006 5:50 pm    Post subject: 2 Stroke VS 4 Stroke Reply with quote


Quote:
From: "Wayne T. McCullough" <blackbird754(at)alltel.net>
Reply-To: kolb-list(at)matronics.com
To: <kolb-list(at)matronics.com>
Subject: Re: Kolb-List: 2 Stroke VS 4 Stroke
Date: Sun, 1 Jan 2006 20:22:33 -0500
<blackbird754(at)alltel.net>
Aha......yes ..Rotax does know about the crank twist problem......My new
blue head 582 with an "E" box has the starter mounted to the gearbox and
pull rope on the mag end........I have read all of the info on the new
bluehead and ....it seems Rotax has done their homework with this new
motor....
Time will tell.............

I'm tellin' ya'll I'm not making all this stuff up Wink.. Quite a few guys
have already spent a lot of money learning about this and I for one prefer
to just learn from their experience...
The E box is the best deal all around if you need electric start. Sure it's
1400 bucks, but it can't damage your crank and it works really well....
Personally, I think I'll always find a way to use a pull start if I run a
2-stroke if for no other reason than the weight savings. The only thing I
wish I could do with my firestar is pull the rope after getting into the
plane (my trike was setup this way and it was heaven). As it is, I have to
start outside the plane and there're obvious safety concerns with that. The
clutch helps with this a good bit though....
LS
N646F
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frank-margie(at)worldnet.
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PostPosted: Sun Jan 01, 2006 8:05 pm    Post subject: 2 Stroke vs 4 Stroke Reply with quote


Don,
I understand there is a single cyl, 4 stroke Honda, used in Motocross bikes-----and evidently it's about bulletproof, despite being really abused, at very high RPM's, under very tough conditions. The guy who told me about them thought they would make a good U/L engine-----are you familiar with anything fitting that description?
Also, in the Dan Johnson article on the Hawk Ultra, in the Jan '06 U/L Flying, he talks about a 2 cyl Jabiru in the developement stage. Supposed to be 45 HP (at) 85 lbs. Sure sounds interesting if it comes to pass.
Frank Clyma
-------------------------------
From: "Don Gherardini" <donghe(at)one-eleven.net>
Subject: Re: Kolb-List: 2 Stroke VS 4 Stroke
HI Will,
Hehe...ya pard...I would brag on how good the 447 has treated me on the
Flagfly...but then it would probably quit me on the very next flight too!
I think I understand you perfectly Will, and I believe you are very likely
correct...that your 503 has been...and is a very dependable engine, much
like most of them.


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donghe(at)one-eleven.net
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PostPosted: Sun Jan 01, 2006 8:43 pm    Post subject: 2 Stroke vs 4 Stroke Reply with quote


Frank,
Yes I am very familiar with the Honda engines in the motocross bikes....and
yes, they are about bullet proof...but as an ultralite engine, I dont think
they are suitable at all due to the transmission built into the lower
crankcase...adds a ton of weight.
I have Looked at every single motorcycle engine Honda makes with an eye
towards light aircraft power, and I have found none suitable to be easily
dismembered from the transmission and adapted to a reduction drive
configuration.
If some ever does find out how to do this economically..they will have given
the light aircraft world a whole new and wonderful source of powerplants, as
the mass-production of Motorcycle engine makes them so much cheaper ...not
to mention the availability of wrecked bikes for super low prices.
Now I have NOT heard of the 2 cyl Jab....and it surely excites me......I am
going to head for their website right n ow as I dont subscribe to UL flying
anymore..
thx for the tip!
Don Gherardini
FireFly 098
http://www.geocities.com/dagger369th/my firefly.htm
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PostPosted: Mon Jan 02, 2006 11:32 am    Post subject: 2 Stroke vs 4 Stroke Reply with quote


Yes I am very familiar with the Honda engines in the motocross bikes....and
yes, they are about bullet proof...but as an ultralite engine, I dont think
they are suitable at all due to the transmission built into the lower
crankcase...adds a ton of weight.
I have Looked at every single motorcycle engine Honda makes with an eye
towards light aircraft power, and I have found none suitable to be easily
dismembered from the transmission and adapted to a reduction drive
configuration.
------------------------------------
Don,
Back in the early 80's, a friend put a Honda Oddesy ATV engine on a Weedhopper, and it worked very well (it was a 2 stroke). He chose it because it did not have a built in gearbox. You know where I'm going with this, and I know you've already been there, but I'd like to hear what you did/didn't find. It's hard not to be impressed with any Honda motor, and they build lots of them without gearboxes---and today, most are 4 cycle. Sure would be nice if something off a snowmobile/seamobile/genset/pump/whatever might work for a legal U/L.
I've also seen pics of a larger bike engine (not a Honda) installed in a light plane, with the gearbox serving as the reduction unit. This list has had postings on BMW conversions, and there is a Harley based demo at Sun 'n Fun (on a test stand). How much does a Honda motocross motor weigh incl the trans? Can it be lightened by removing some of the gears? Might the gearing hold up if used as an RDU?
I for one really enjoy the info you have shared with this list----can I get you to expound on the above?
Frank Clyma
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PostPosted: Mon Jan 02, 2006 12:05 pm    Post subject: 2 Stroke vs 4 Stroke Reply with quote


Don & Frank,
Just before leaving for the holidays, I was Googling and I ran across a
fellow down in South America that had put a small Honda motorcycle engine on
a trike. After reading Don's post, I spent a couple of hours trying to
rediscover the page as I did not bookmark it. I failed. But as I recall it
was running some where around 12,000 rpm. The fellow used the gear box and
modified it so that he could mount the propeller.
May be in another day or two I can recall what I was originally looking for
and search again. It is amazing what people are doing.
Jack B. Hart FF004
Winchester, IN
do not archive
02:30 PM 1/2/06 -0500, you wrote:
Yes I am very familiar with the Honda engines in the motocross bikes....and
yes, they are about bullet proof...but as an ultralite engine, I dont think
they are suitable at all due to the transmission built into the lower
crankcase...adds a ton of weight.
I have Looked at every single motorcycle engine Honda makes with an eye
towards light aircraft power, and I have found none suitable to be easily
dismembered from the transmission and adapted to a reduction drive
configuration.
------------------------------------
Don,
Back in the early 80's, a friend put a Honda Oddesy ATV engine on a Weedhopper, and it worked very well (it was a 2 stroke). He chose it because it did not have a built in gearbox. You know where I'm going with this, and I know you've already been there, but I'd like to hear what you did/didn't find. It's hard not to be impressed with any Honda motor, and they build lots of them without gearboxes---and today, most are 4 cycle. Sure would be nice if something off a snowmobile/seamobile/genset/pump/whatever might work for a legal U/L.
I've also seen pics of a larger bike engine (not a Honda) installed in a light plane, with the gearbox serving as the reduction unit. This list has had postings on BMW conversions, and there is a Harley based demo at Sun 'n Fun (on a test stand). How much does a Honda motocross motor weigh incl the trans? Can it be lightened by removing some of the gears? Might the gearing hold up if used as an RDU?
I for one really enjoy the info you have shared with this list----can I get you to expound on the above?
Frank Clyma
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PostPosted: Mon Jan 02, 2006 2:52 pm    Post subject: 2 Stroke vs 4 Stroke Reply with quote


Jack and all
I ran across a CBR600 powered tandem seater at Lucedale Miss fly in
three years ago.. The guy use the whole engine.. He had the gear shift
and clutch levers in the cockpit.. Used a roller chain and when I called
him, he said that he has several hundred hours on the combo.. He lives
south of Lucedale as I recall. Said that he was installing a cbr 900 in
a Pulsar.
Ronnie Smith gave me his phone number.. Herb
do not archive
On Mon, 02 Jan 2006 15:12:26 -0500 "Jack B. Hart"
<jbhart(at)onlyinternet.net> writes:
<jbhart(at)onlyinternet.net>


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PostPosted: Mon Jan 02, 2006 5:10 pm    Post subject: 2 Stroke vs 4 Stroke Reply with quote


Herb Gayheart wrote:
Jack and all
I ran across a CBR600 powered tandem seater at Lucedale Miss fly in
three years ago.. The guy use the whole engine.. He had the gear shift
and clutch levers in the cockpit.. Used a roller chain and when I called
him, he said that he has several hundred hours on the combo.. He lives
south of Lucedale as I recall. Said that he was installing a cbr 900 in
a Pulsar.
Ronnie Smith gave me his phone number.. Herb
do not archive

I've seen what had to be the same a/c at a flyin N/E of Jackson MS,
about 100-125 mi north of Lucedale, so he obviously isn't afraid to
travel with it. He told me that the shifter was so he could use a lower
gear when carrying passengers.
Charlie

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donghe(at)one-eleven.net
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PostPosted: Mon Jan 02, 2006 5:12 pm    Post subject: 2 Stroke vs 4 Stroke Reply with quote


Frank,
The installation Herb is talking about is really the only one I have seen
with a Honda Motorcycle flying successfully. The key to his success I
believe is that the plane fits the engine....in other words..it works
because that particular airplane...a Drifter/Brezzy looking kind of thing
has alot of wing and isn't expected to go very fast. I have lost contact
with this gent..and I always wondered how the long chain would work. There
is a pic of this bird and engine installation at VULA.com
I believe he told me he took off in 3rd and shifted to 4th after leveling
out.
Now...I can easily believe the old Honda 250 2 cycle from an odyssey would
fly a weedhopper. I sold weedhoppers back in the late 70s as a dealer and
remember well how they flew with very little power. also remember a
weedhopper weighed in at 180 lbs soaking wet and had a huge wing. The plane
fit the engine.
What we have to deal with today is a crop of birds that have evolved in
their design to "Fit" the engines, and about all of them have been tweaked
to perform with the snowmobile 2 cycles that have been slightly tweaked to
fit a propeller application instead of a torque converter drive.
What I really think would be the answer is to pick another source of engines
and design some airplanes to fit them better.
Some of you have seen and know of the Legal Eagle flying with a 32 hp
industrial v-twin.(generac)...This is a better match than a Firestar and a
motorcycle engine. IN fact their was a fella who installed a 25 hp Kohler on
a Firestar and claimed it flew really well...until the crankshaft broke off
at the PTO end, which is a common trait among Kohlers even in the lawn
tractor biz. Briggs Vanguards are now up to 35 hp and are very well built
engines and I bet a buck we will see alot of those on airplanes like the
legal eagle's,N-3's and similar planes with alot of wing. Talk about
range!..todays V-twin engines burn from 1.5 to 2 gallons an hour at WOT and
full load.
Anyway..back to the motorcycle engines..
If we operate a Honda motorcycle engine...just about any of them, at a load
that will limit the rpms to 80 or 90 % of the max rpms (like we do our 2
cycle Rotax's) the lifespan will decrease dramatically. These engines are
designed to fit the application and environment they work in...and a full
load at 100% throttle on a dirtbike...or a street bike is always a momentary
thing in the machines they power. to get a motorcycle into the same load
that we regularly operate our airplane engines at...we would need a huge ,
steep hill and a big ole heavy trailer behind the bike...and the hill would
be so steep that about the time we shifted into 2nd or 3rd gear, the engine
would not turn up to the redline. ANd then we hold it there, without letting
off....for an hour or more.
Let me tell you we are gonna wear that Honda out in a hurry men. It will
begin to heat up without any let up in the load, and when an engine cannot
get rid of the heat..we will melt it down.
So...when we look at that CBR600...aprox a 80 hp engine at 12,000 rpms, it
will only work if it is allowed to operate at a continuous load that will
absorb about 50 hp at half the rpms, then it will be able to get rid of the
heat. The transmission allows him to run it at a higher hp level for
takeoff,(when the load is highest) and then shift to reduce the engines rpms
and keep the propspeed up...sounds great and works well I bet...just as long
as you have an airplane that will support to 200 lbs of engine and
transmission and I bet a 25lbs of chain,, and you are not looking for much
of a rate of climb.
Then there is a fella with a Neuport or a spad replica with that Yamaha
v-twin motorcycle engine..very interesting I thought..useing the shaft drive
output and fixing a prop on it..anybody hear how it is getting along?
another plane with alot of wing...2 of em in fact!
Frank, you ask if some gears could be removed from the transmission to save
weight and would they rest hold up if used as a Reduction unit....I cannot
answer these questions...I have pondered them myself for a long time.
Would the straight cut gears in that trans stand up to propeller vs piston
power pulses?
I think a fella could take out a few and replace em with spacers probably.
MY son and I used to be in the tractor pulling sport, and the things we did
there to engines and transmissions would make an engineer spit in disdain!
BUt we broke alot of things too!
How much does the engine and transmission weigh...cannot say..I dont know.
we havent really even specified which motorcross bike we are gonna di-sect
as a donor to this project.
The BMW twins are being used because the transmission will unbolt from the
crankcase, and because they are a lower rpm and high torque engine of high
quality. The have exceptional head cooling ability for a motorcyle engine.
I think there is no doubt they are the best motorcycle engine for aircraft
adaptation.
We need continuous duty designed engines for our sport...and the industrial
engine market is quickly approaching a place where they will have just what
the back to basic flying machines need...the difference this time
around...is the engines will last about 20 time longer than the ones we
started with back in the late 70s.
BTW....a 24 hp honda costs about 1100 complete with electric starter. The
31 hp Vanguard is about 1500..and the 35 will probably be a 100 or so
more...RETAIL....!
Just think...if Dennis and Homer would have set out to design that firefly
to fit the v-twin industrials we have today instead of the 447...hmmmmmmmmm
Don Gherardini
FireFly 098
http://www.geocities.com/dagger369th/my firefly.htm


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PostPosted: Mon Jan 02, 2006 5:37 pm    Post subject: 2 Stroke vs 4 Stroke Reply with quote


Charlie
I have often thought that this set up would work on a modified MkIII
fuselage.. Set the engine on a plate that is attached to the boom tube h
section--or an h section modified such that there are two through bolts
spaced a foot or more apart to attach the engine.. Lowering the engine
three feet or so would be a good thing.. IMHO. Herb
do not archive
On Mon, 02 Jan 2006 19:10:31 -0600 Charlie England
<ceengland(at)bellsouth.net> writes:
<ceengland(at)bellsouth.net>


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PostPosted: Mon Jan 02, 2006 7:31 pm    Post subject: 2 Stroke vs 4 Stroke Reply with quote


Frank,Don all
To clarify---I talked to the fellow for an hour or more.. Lives in
Pascagoula, Ms area.. ( I said south of Lucedale to keep from trying to
spell Pascagoula!! Wink )
He told me that he had 300+ hours on the chain drive, that he had
removed an idler pulley on the long chain since it caused more vibration
than it solved.. He also said that the only thing that he had replaced
was the drive sproket and that was just on gut feeling since he could see
no wear.. The o ring chain appears to be really tough..
No doubt that the installation was heavy--water cooled engine with a
heavy gear box..
I seem to recall that he took off in 2nd and ran the rpms right up
there... 12k or so.. Had a respectible dia prop.. Likely 68 inches or
more.. Cruised in third or 4th.. Cannot remember his cruise rpms? Likely
50 to 60 % of full power? My recollections from three years ago.. As
I said Ronnie Smith at South Miss. Light Aircraft has his number..
I priced CBR engines at a salvage yard a few months ago and recall
that the price was in the $1200 range.. I could have bought a late model
BMW engine for 1500 bucks.. Properly engineered , I suspect that the BMW
engine installations can approach 4 cycle Rotax engines in Reliability..


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PostPosted: Mon Jan 02, 2006 8:16 pm    Post subject: 2 Stroke vs 4 Stroke Reply with quote


The Honda 4 stroke dirt bikes have very light, reliable, 4 storke, liquid
cooled engines. The only problem is that the transmission is a part of the
motor and makes it pretty heavy. My 650 CC motor is rated around 50 HP and
weighs about 120 pounds with the gearbox. You could never take enough gears
out to make any kind of meaningful difference in that weight. That combined
with the very short chain drive output shaft makes a chain drive the only
practical way to drive a propellor from that engine... Chains break,
require regular maintainence, and wear out. I would not want a chain dirven
prop on my plane... I also agree that these motorcycle engines are not made
to put out anywhere near rated power for extended periods of times. An
engine running near 12,000 RPM most of the time will not last very long. In
typical use, those motorcycle engines see their maximum RPM's for less than
a minute at a time. I would think that a Honda motorcycle engine running at
anywhere near rated power would wear out quickly and be unreliable.
I think the 2 stroke rotax engines are more practical and even more reliable
than trying to push a motorcycle engine way beyond what it was designed to
do.


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PostPosted: Tue Jan 03, 2006 2:38 pm    Post subject: 2 Stroke vs 4 Stroke Reply with quote


Don,
Are you trying to torment me? If so you are succeeding.
Dennis
Quote:

Just think...if Dennis and Homer would have set out to design that firefly
to fit the v-twin industrials we have today instead of the
447...hmmmmmmmmm

Quote:

Don Gherardini
FireFly 098
http://www.geocities.com/dagger369th/my firefly.htm


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