| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 1616.1 | Complex and they wear out quickly!> | CSTEAM::HENDERSON | Competition is Fun: Dtn 297-6180, MRO4 | Mon Jul 25 1994 11:16 | 7 |
| Hanno Pretner used them many times and did wonderful maneuvers when he
reversed the pitch etc.
I have seen several in use in the UK many years(13 plus) ago on scale
ships. Sure sounds great when the pitch changes.
E.
|
| 1616.2 | | UNYEM::BLUMJ | | Mon Jul 25 1994 11:56 | 7 |
| re: -1
Seems like Prettner has tried a lot of "innovations" in his R/C career.
I can remember him using belt drive reduction with very large
propellers some years ago.
Apparently this stuff doesn't work well in the long run.
|
| 1616.3 | Neat Stuff | LEDS::WATT | | Mon Jul 25 1994 15:32 | 11 |
| Jim,
I disagree. I think that these innovations do work - it's just
that they are not widely available and most RC'ers are not up to making
the necessary components themselves. Reduction systems sure work
nicely on electric gliders (the slow ones). Rubber power guys have
used vairable pitch props for eons. Variable pitch props are probably
less of an issue with the 4-strokes that are so popular in pattern now.
I'm sure Hanno was using his with a 60 2-stroke.
Charlie
|
| 1616.4 | unrelated question | UNYEM::BLUMJ | | Mon Jul 25 1994 16:27 | 4 |
| Totally off the subject, if 2-stroke 1.20 size engines were allowed in
pattern do you think they would be used heavily?
|
| 1616.5 | Opinions. | CSTEAM::HENDERSON | Competition is Fun: Dtn 297-6180, MRO4 | Mon Jul 25 1994 16:49 | 28 |
| re: -.1 and -.3
> Apparently this stuff doesn't work well in the long run.
I think the operative was "in the long run". All of these belt or gear
drives seem to wear out. Plus in pattern it is added weight.
Ref the 120 2-c question. I have seen both the YS120 4-c and the
OS 120 2-c. in Extra 230's, in the desert. The YS won and the OS was noisy.
This is not to say that with the correct pipe etc the 120 would not be
a winner. The Pattern planes will have a size limit on them so power to
weight ratio will always be the real issue. The one thing that I think
that all 4-c's have over 2-c', especially with tuned pipes, is that
they are much less fussy on the needle. If you set it to rich, (the
4-c), it will get through the flight and if you stay within the power
limits you can even win a round or two. [believe me I know you can]. If
you are off a little with a 2-c the darn thing will load up and
embarrass you. Pattern folks love power but the respect reliability
more....
end of 2-c'ents worth.....
Regards,
E.
|
| 1616.6 | More Opinions | LEDS::WATT | | Mon Jul 25 1994 17:28 | 19 |
| I think you will see more large 2-strokes if the displacement rule goes
by the wayside. I agree with Eric that the YS120 is hard to beat but
there are an awful lot of parts in a 4-stroke to fail. When they do,
it is expensive and quite often sudden. If you are into contests, you
need a spare engine! Two-strokes on the other hand are very simple and
will definately win on power to weight if the development of the tuned
exhaust happens. Right now, there is no reason to develop a large
pattern 2-stroke because we can't use them. There are a bunch of
powerful 2-strokes going into the big Reno Racers though. You will
probably not see a 4-stroke winning any of those races! Yes they are
noisy but only because they are pylon racers. Indy cars are noisy
also. Muffled tuned pipe 2-strokes are very quiet if the RPM's are
kept down with a big prop. The 2-stroke pattern ships are easily kept
to 90 dB or even less.
By the way, I love my YS120!
Charlie
|
| 1616.7 | electric geared variable pitch prop - yes please! | FRUST::HERMANN | Siempre Ch�vere | Tue Jul 26 1994 02:38 | 21 |
| hi all,
i have seen a variable pitch prop on an electric pilatus porter.
it was built by the swiss hans buehr.
he could even produce reverse thrust, and you should have seen his landing
approach with reverse thrust... also the roll out after touchdown was quite
short!
he used the tail assembly of a helicopter, so he did not have to worry
about anything. i think it was even a 3 bladed one. looked very good.
needless to say, the prop was driven by a belt gear reduction.
else you would not be able to get the pitch-actuator through the center of
rotation. (unless you can drill through your motors shaft...)
about belt drive and wear: to my knowledge belt gears are very quiet, very
effective (approx. 98%) and very durable. the latter applies of course only,
if the gear is sized reasonably for the power applied. in germany belt gears
are available for power up to 2000 W!
cheers
joe t.
|
| 1616.8 | | UNYEM::BLUMJ | | Tue Jul 26 1994 08:58 | 17 |
| Interesting stuff here...
Eric - does OS make a 1.20 2 stroke? I thought the 1.08 was the
biggest they produced.
I do not like what I am hearing about 2 strokes being more sensitive
to needle settings. Due to the prevailing wind direction at my field
I will be taking off with trees ahead and on both sides. If the engine
sags shortly after takeoff, it is highly likely that the glider in tow
will crash.
Am I reading that 4-stokes are fussier to adjust(valves, etc) but are
more reliable running? My primary objective for the engine in the tug
is consistent power and absolute reliability.
|
| 1616.9 | absolute reliability | KAY::FISHER | BXB2-2/G08 DTN 293-5695 | Fri Jul 29 1994 12:07 | 12 |
| > <<< Note 1616.8 by UNYEM::BLUMJ >>>
...
> Am I reading that 4-stokes are fussier to adjust(valves, etc) but are
> more reliable running? My primary objective for the engine in the tug
> is consistent power and absolute reliability.
Then you want gas.
Bye --+--
Kay R. Fisher |
---------------O---------------
################################################################################
|