Model Forum / Radio Controlled / Air Models / May 2005

Greetings

Something like this was published in a magazine several years ago.

Sorry don't recall which one.

RCM would be the most likely. Might try their web site first.

As I recall it only synced above half throttle and sensed it you lost an
engine and allowed you to retain control of you good engine.  Was built with
common DIP chips and standard componets.

Will look at work where my files are later today. I need to build one for a
Britian Norman Islander that I am starting construction of soon.

Hugh

It is not necessary to synchronize the engines to the degree you want.
I have three twins and here is what to do.  Adjust each engine to rich
side of peak about 200 rpms.  Richen the weaker engine to the other
engines rpms.   All of mine are within 200rpms of each other anyway
and I don't have to do this proceedure although I check it each flying
sesson.  You will not notice even if one engine is acting up to even
1000 rpms if your speed is high.   If this is your first twin,
remember, engine out cannot be corrected with ailerons.  Practice
using the rudder.  An engine out is a yaw problem not a roll problem.
If you have and engine out, keep wings level with the rudder, turn
only towards the live engine if possible and keep plenty of speed up
or your rudder control will not save you.
Good Luck
Gene

Greetings

Just found the article in my files at work.

Title: Electronic Sync System For Twins
Author: Joe Utasi
Published in Model Aviation, October 1982

Printed circut boards were avialable form Jomar Products at the time of
publication.
Would be simple to layout in Eagle PCB designer and do a toner transfer to
copper clad and etch. It is single sided, no surface mount, no
microprocessor design.

Requires the high throttle pulse to be a long pulse. Draws 16-17 ma at 4.8
volts. Uses two Hall effect sensors and magnets in spinner backplate. Sync's
engines RPM not crank shaft position. Cuts in at 2500 RPM.

Circut board would be aprox size of a modern receiver and just plugs in to
receiver throttle channel and then plug each throttle servo into the sync
board.

Article has a nice discription of how the circut works and mods / tuning you
can make.

This was one of several electronic projects that Joe developed and had
published in MA. Don't know if Joe or Jomar are still around.

Hugh

There was a system many moons ago.  Don't recall who made it.

It involved mounting small button magnets on the back plate of the spinners.
Then positioning a hall effect sensor (mag tape head is one example) behind
each spinner so that it sensed the passage of the magnets.  This provides an
RPM reading from each engine.  It then went to a control box which
controlled the two engine servos to match the RPMs.  There was a master
slave relationship with the slower engine being the master.  That way the
system would not constantly try to bring the slower engine up to the faster
engines RPM when at full throttle.

There was also a fail safe mode. In the event of an engine failure, the
system would sense the RPM having dropped below a predetermined level and
disconnect the slave feature.  Thus allowing the remaining engine to
continue under normal control.

I seem to recall that price and the fact that it was a novelty rather than a
necessity kept sales too low to stay in business.

Hi All,

A french engineer is doing the system I wanted last year   :D   ! (An
much more, sequencer for gears, flaps, servo slower ... etc ...)

It's not a master-slave system, but it would synchronise engines b
slowing down the faster, and accelerate the slower. And the option t
stop the surviving engine automaticaly.

The system is configured by a tool under windows freely downloadable.

I don't try it yet. The developper is looking for beta testers.

See at the bottom of http://servomax.forumactif.com/ for englis
version

ML

--
ML