Zenith Aircraft Builders and Flyers
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sizeing engine/drive/propeller
I am interested in using the Great Plains 2300cc with a reduction drive.
I have asked locally (EAA chapter, fellow pilots, etc) about engine size for the ch750, now am asking 750 community.
I have not yet asked the questions of Zenith or Great Plains, or any propeller manufacturer. Will do so in near future.
I am not interested in Rotax or Jaburu, and not so enamored of the Corvair modifications, although that might be of interest if VW use is unlikely. And possibly an 0-200 if price was right.
I would like to know several things in order to make a rational decision, as opposed to the many anecdotal responses I have recieved:
1. What is the cruise L/D of the 750
2. What is it's drag polar
3. What is the static thrust of the engine (will it go stol, for what duration (here I am interested in the heating and cooling of the engine; if the takeoff roll is of short duration perhaps that would allieviate heating problems)
4. What is the reduction drive efficiency
5. What is the reliability of the reducer, how many hours untill failure, what is characteristic failure mode (assuming cog belt or v belt drive, not a geared reducer)
Of course one would like to know something about all of these components in order to do a systems analysis, and then push parameters around. So, I am trying to gather in as much info as possible.
Trust, but Verify
Mike
P.S. I am trying to figure out how to use this discussion tool, so please forgive if it goes wrong.
Replies to This Discussion
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Permalink Reply by Chris Aysen on
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Michael - 3 different engine configurations: those that develop hp at roughly 2800 rpms (lycomings and continetals), those that develop hp at roughly 3200 rpms (Jabiru, Corvair, UL, & direct drive VW), and high revs with reduction units (Rotax, VWs w/reduction, and some autos with reduction units). Thrust seems to increase with propellor length, i.e. Great Plains 2180 with 1.6:1 reduction unit with 72" prop produces 350 lbs of thrust while a 2.0:1 ratio with an 84" prop produces 450 lbs of thrust. So the question would be what length prop could I turn on a given engine. Seems like the most efficient engine would be a direct drive (less weight) that produces its hp at a lowered rpm thus is the conditions needed for a longer prop.... As for heat control of the VW engine see Wayne Clagg. Can't help you on the drag polar numbers, I would suggest ask Chris H. Reduction drive efficiency and reliability? I assume you mean Great Plains. See Great Plains. Hope this helps.
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Permalink Reply by Wayne Clagg on
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Hi Michael, if you are interested in the Vw with a Valley redrive contact me directly at rclaggf4u@aol.com. I will show you how I solved my cooling issues. Wayne
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