Page 1 of 1

PostPosted: Thu Mar 27, 2008 10:15 am
by Banned my Admin

PostPosted: Thu Mar 27, 2008 11:57 pm
by JPXman
OMG - push/pull configuration?????

its the most amazing attempt at lazair customization i've ever seen - even more than the pioneer behind the seat on a lazair that i have!

has this thing flown?
are the engines and props worth $5,000? must be close....

interesting item for sale at that price to say the least. but tell me that front engine is not cantilevered off the front wing attach fitting that we have been talking about?

i need more pictures, i am in awe. to even attempt this conversion deserves some attention - but without any engineering input or massive experience building homebuilts i wouldn't trust it as far as i could roll it.


PS: i didn't realize that he used the old 185 nacelle and mounting plate with no extra beefing up at all - that is not good.
PPS: what are those on the trailing edge - flaps or more ailerons???

PostPosted: Fri Mar 28, 2008 11:58 am
by JPXman
of course this is my opinion:

counter rotating engines are for aircraft with a critical engine where the engines turn in the same direction. correct me if i'm wrong, but if the critical engine fails then longitudinal direction control becomes difficult, in that most if not all of the available rudder is used to counteract the thrust from the one operating engine. thus the phrase "never turn towards the dead engine" as you'll never be able to get the plane out of the turn with available flight control.

1. engines turning in opposite direction, however cool looking, gains very little for a lazair. there really is no critical engine on a lazair with 185's - the thrust is too small. With bigger engines, it becomes more noticeable, but still manageable. i know this from personal experience with the JPX engine.

2. you need to buy a new prop if the engine turns in the opposite direction (or have ground adjustable prop so that you can crank the blades backwards - what carel has done)

3. making a 2-stroke run backwards is easy. my JPX sometimes starts up turning the wrong way happily until i realize it (you can hear the difference). just adjust the points that way. to make a pull starter go the other way, is another matter. the rope is easy, but the pauls that extend would have to be reversed - i think you'd have to find another starter but i may be wrong - unless the pauls are squared and can grab the flywheel nubs in either direction.

so don't go solving problems that don't exist. engine TORQUE is not combatted by counter rotating engines. P-factor is eliminated though. helping critical engine performance is negligible, as the critical engine on a lazair isn't that critical - if you have an engine failure, regardless as to whether you lose the left or right engine, or whether it counter rotates, it will still grab your attention and require big rudder input to stay pointed straight.