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promod69camaro
Joined: 22 Aug 2007
Posts: 14
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 Posted: Fri Aug 24, 2007 4:48 pm Post subject: Эрот |
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| Quote: | ?? ?????? ?????????????????????????? ?????????????????????? ???????????????? , ?????? ???????? ????????????, ???????????????????? ?? ???? ???? 956 ???????????????? ?? ???????????? ( ?????????????????????? ?? ?????????????????? ???????????? ????) . (???? ???????????????? ?????????? ?????? ?????????????????????? - ????. ????????????. ?????? ????.????????,
???? ?????????? ???????????????????? ?? ????????????????, ???????? ?????? ?? 4 ?????????? ??????. ?????? ?????? ?? ?? ?????????? ?????????? ?????????????????? ??????????????????, ???????????????? ?????? ?? ?????? ?? ???????? ?? ????????????... ???????????? ?????????????? ???? ?????????????? ?? ?????? ???????????? ?? ???????????? - ???????????? ???????????? ????????. ???????????? - ?????? ????,
???????? ???????????? ???????????????? ?????? ???? ????????????. ???????????????????????? ????????????????, ?????????????????? ?????????????????? ????????????. ?????? ?????? ???????????? ??????????.
???????????????????? ??????????, ???????????? ???????????????? ???????????? ????????????????, ???????? ???????????????? ?????????????? ?? ?????????????????????? ??????????????. ??????-???????????????? ?????????? ?? ??????????
?????? ?????? ???????????????????? ???????? ?????????????????????? ?????????? ?? ??????????????, ???????????? ???????????? ?? ???????????????????? ?????????????? ?????????? ????????????, ???????????????????? ?????????? ???????????????????????? ??????????, ?????? ?????????? ?????????? ?? ?????????????????? ???????????????? ?? ??????????????,
?????????????????????? ?????????????? ?? ??????????, ???????????? ???????? ?????????? ????????, ???????????????? ?????????????? ?? ?????????? ???????????? ??????????-?????????? ???? ???????????? ?????????????? ????????????, ???????????????? ?????????????????? ?????????? ????????????, ???????? ???????? ??????????,
?????????????? ???????????????? ?? ???????? ?????? ????????????????????????. ?????????????? ???????????????? ?????????? ???????????? ?? ????????????????, ???????? ?? ?????? ???????????? ???????????? ???? ?????????????????????????????????? ?????????????? ??????. ???????????????????? jennifer love hewitt ???????????????????? ?????????????????? ?? ?????????????? ???????????? - ???????? ???????????? ???????? ???????? ???????????? ?????????????? ??????????????
?????????????? ??????????????????. ???????????????????????? 22 ???????????????????? ????????, ?????????? 100 ???????? ?????? ?????? ?????????????????????????? ?????????????? ???????? ?? ??????
???????????????????? ???????????????????? ?????????? ?????????????? ?????? ????????????????????. ???????? ?? ??????, ?????? ?? ???????????????????? ???????????????????????? ?????????????? ?????????????????????? ?????????? ?????? 7.. ?? ???????????????? ?? ???????????????????? ??????????????, ???????? ???????? ?????????? ????????????????, ?????????? ???????????? .
?????????? ???????????? ???????????? ?????????? ???????? ????????????????... 
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MARIJUANA VAPORIZER
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Last edited by promod69camaro on Sat Feb 26, 2011 6:31 pm; edited 5 times in total |
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Gilles.Thesee(at)ac-greno
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| Posted: Sat Aug 25, 2007 3:26 pm Post subject: Prop speed reduction unit (PSRU) |
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promod69camaro a écrit :
| Quote: | Propellers seem to operate much better around 2200 to 2500 RPM. And at lower RPM, there is less prop noise to deal with. Lets say a person put a 1.5:1 reduction PSRU on the motor, and had a new cam ground for operation to 4000 rpm if necessary, which it probably would be. That would allow the engine to make about 25% more power, and the prop speed would slow into the more efficient speeds. There would be cooling issues, and it would not necessarily have to run at the higher RPM all the time.
I am sure there are all kinds of reasons not to do it. For one, its a direct drive aircraft engine and why mess with it. But the fighter planes in WWII all had PSRU's on them, even the radial power plants.
Shawn,
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Your observations on PSRUs and WWII engines are correct.
Actually, some propellers can an do perform well at high RPM.
Nevertheless, with a fast turning prop, the diameter must be limited,
and the overall propulsion efficiency goes down. There is an optimal
prop disk area for each output.
For a high power engine, you need a large disk area, hence a slow
turning prop, because the tip speed limit is the same.
Bottom line, 2700 rpm is just about right for a 100 hp direct drive engine.
Concerning your projected modification, you may end with a completely
new engine, but why not ?
Best regards,
--
Gilles
http://contrails.free.fr
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jetboy
Joined: 22 Jul 2006
Posts: 233
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| Posted: Sat Aug 25, 2007 9:11 pm Post subject: Re: Prop speed reduction unit (PSRU) |
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Shawn,
you have more or less answered your question, I would like to add that the 3300 or 2200 for that matter is unlikely to last with a prsu because you wont be able to cool it sufficiently. I understand a helicopter company was using the 3300 but gave up after burning up 2 or 3.
The torsional vibrations to the crank will need addressing. Rotax dont just bolt any old set of gears on the 912 and even their current setup doesn't do that well. For a study on torsional vibration do a search using that term and BD5 might yield a very good paper on the difficulties.
If it were me trying to do more with the unit I would be looking at mild supercharging first.
Ralph
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Ralph - CH701 / 2200a |
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Peter H
Joined: 20 Mar 2007
Posts: 197
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| Posted: Sat Aug 25, 2007 11:11 pm Post subject: Prop speed reduction unit (PSRU) |
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I think you can do better if you quit the Bing. I am part way into
installation of the Frensch TBI fuel injection and have got an extra 170RPM
static up to date.
Peter
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pjdisher(at)bigpond.com
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| Posted: Sat Aug 25, 2007 11:58 pm Post subject: Prop speed reduction unit (PSRU) |
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Hi Peter ,
I'm also wanting to shaft the Bing at the moment in preference to the Sonex
Aero-Carb or the ellison.
I'm interested in what you have done in using this French TBI fuel
injection, It obviously runs a lot better.
Could you also give me there web site address. I'm very keen for an
alternative.
Many thanks,
Peter Disher
Australia
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Peter H
Joined: 20 Mar 2007
Posts: 197
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| Posted: Sun Aug 26, 2007 1:08 am Post subject: Prop speed reduction unit (PSRU) |
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Peter,
I bought an Aerocarb and based on problems found by a hangar mate I decided
to check it on the bench first. Bad news _ the design is wrong, the throttle
cable is attached off centre and not even co planar with the slide. Any
attempt to move the throttle open quickly means an off centre load which
causes the slide to twist and jam. Worst case when attempting a go around .
My mate has to ram the throttle fully open for take off as any attempt to
open slowly causes it to jam .His is a J 4 cyl and the problem is worse with
the J3300. Suction at low throttle openings pulls the slide against the
frame and friction does the rest.
I attempted to discuss this with the CEO of Aerocarb and got attempts to
blame my installation followed by personal abuse and then was banned from
his Jabiru Engines list.
I think the Ellison is better designed but all slide type carbs are subject
to this kind of problem which is more pronounced with the larger engines. A
central attachment for the cable to the slide will help to overcome the
problem.
My TBI installation was pioneered by Helmut Frensch (Tailem Bend) He is a
retired development engineer for Mitsubishi.
Details with pictures were posted on the list where I am banned. (LOL)
I have sourced a suitable throttle body and at the present time I am
adjusting the fuel maps to suit.
I conducted extended experiments with the Bing and will be able to contrast
the results.So far I have gained 170RPM static.
Regards
Peter H Queensland.
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