Sorry if I confused the crankshaft question, The front housing on the MOKI can be rotated so that the carb points in the same directiuon as the exhaust port. If your engine installation can accomodate that layout then you can save yourself some big $'s.
I first ran into opposite prop rotation on twins when I was scratch-building an F7F Tigercat. I took two Enya 53 4-c's and moved the cams on one of them to get reverse running. You need two cams with their own gears driven by a central gear to do this. It was a blast breaking-in the motors on my son's trainer.
The regular motor was no problem but when I fitted the clockwise rotation motor to the same model things got a little funky. You needed a lot of left rudder on take-off which caused a left roll as soon as the airplane left the ground. Quite a high pucker factor was recorded several times.... The problem was that the engine needed left-thrust instead of right-thrust. To cut a long story we survided, even though we did amuse the peanut-gallery more than once.
The story on the F7F get even funnier. The opposite rotation on a twin really helps if you lose the port (left) engine. The reaction to the rotation of the prop on an anti-clockwise engine (normal rotation) does not help you keep the port wing up and level. A clockwise rotation on the remaining starboard engine helps keep the port wing up because the plane will naturally try and rotate in the opposite direction to the prop.
You can also set the side-thrust of the angle the engine to counter the turning of the plane towards the dead engine and thus reduce the tendancy to spin out. Opposite rotation engines can be set "opposite" on their wing panels. This makes the planes easier to fly and you lose less energy to the side thrusts employed on two engines rotating in the same direction. Next time you see a Twinstar just check out the angles of the engines that they have used to give good flying with one engine out! You will see what I mean.
Here's the funny bit; After messing with the Enya's and engine layouts etc for almost a year, I finally read beyond the F7F development book that I had been reading and using. Guess what? The prototype had opposite rotating prop's but the production version was modified to accept same direction props because it would require too many spares to be carried to support the fighter in field/combat operations!
Back to the drawing board [This was in 1987 BTW)
Regards,
Eric.
Sorry about the ramble but it is snowing and blowing a bit in NJ today....
ORIGINAL: Multimaniac
Just my question - do you really need counter-rotating props????
Neither do I know the plane you are going to build nor the engines, but my experience from building many twins and multis is that I never needed counter rotating props. Sure, it looks great and may have some aerodynamic benefits, but for my purposes (e.g. on planes like the A.W. Whitley or the Turbo Panda, not fast planes but model twins that can be flown quite aggressively), I wasn't able to feel (in flight) a difference between counter-rotating and not-counter-rotating props....
I think the greatest "benefit" of using normal engines is, besides the lower price of the whole thing, the one that there is a vast variety of different propellers to fit your needs best. There is only a small sortiment of left-running props!
best regards
Chris