Okay, I know this is a pretty fundamental question for this forum, but... why do you use syncros on multiengine aircraft? What's the benefit?

I've been flying a Twinstar this summer, my first twin, on 2 OS .28 heli engines. To date I've not yet been able to understand what the benefit of a synchronizing device for the two engines would be... Is it maybe more of a requirement on larger engined aircraft?

KevinM:

Synchronization is not necessary. You can fly indefinitely without it.

But the advantages include elimination of the low frequency vibration from mismatched rpm that tends to destroy everything that's not rubber mounted.

The biggest advantage is matching the thrust from both engines.

And they just sound better when they are at the same speed.

Bill.

I used an elevon mixer on my Bronco so both engines were controled by the throttle stick and I used the ch 6 trimmer to control offset on the motors.
Evan though you don't know which engine is lagging, you con rock the trimmer and sync to motors
and as Bill said it sounds great !!!

Later
Dan

Kevin and Dan:

I made a double post about using the EMS/Jomar twin sync system, and mechanical sync with the linkages.

See it here:

http://www.rcuniverse.com/forum/Twin...1130772/tm.htm

Might get some ideas.

And Kevin, I like your elevon mixer trick.

Bill.

Dan

Could you elaborate on how you set up the elevon mixer? Do you still need a different channel for each engine?

John

To use the mixer ( I used one from Jomar ) you'll need a mixer and two servos.
one input from the mixer hooks up to you throttle channel, the other input hooks up to
your #6 channel . then the outputs fron the mixer hook up to your throttle servos.
this works well on my OV-10 though you need a transmitter with an adjustable ch 6 rather than just a switch
you can do this same thing with your transmitter if it has computer mixing.

anyway your throttle stick will control both servos and yur ch 6 allows you to rock back and forth untill the strobing stops.

Hi Bill, thanks for your reply. I had previously read your post concerning the different syncronization techniques, but I could not find an underlying reason as to WHY one would go to the trouble. (I had no doubt there was one, I just couldn't fid it!) I've had many great flights with my Twinstar and noticed only a little out-of-syncronization beating, but it's been so minor and never caused me any issues that I'm aware of. (I did spend a fair bit of time ensuring the linkages were as close as I could get them before flying.) Incidentally, due to nagging engine difficulties I've also had quite a few single engine landings, and without any of the bad habits mentioned in other threads on the Twinstar...

Dan, I too like your idea for synching on the fly. I imagine this could also easily be accomplished entirely electronically with a computer radio. I do have extra channels, so I'll have to give this one a try.

Thank you all for your wisdom. I've been bitten by the twin bug and am now working on "kitbashing" a new twin of my own, so I figured I'd better do a bit of asking where I felt thin on knowledge...