multi engine electronic synchronizers?
11-07-2003 | 01:21 PM
#1
Thread Starter
multi engine electronic synchronizers?
Does anyone know if multi engine electronic synchronizers are still available? If so from whom?
I recall a magazine article a decade or two back in which a digital box was used to put a pair of engines exactly in sync. You placed magnets on the drive shafts, and the box used a second servo to match the RPM of the stronger engine to that of the weaker engine. Your radio controlled only the weaker “master” engine. There may have been a little lag in the acceleration but at stable RPMs the two engines turned at the same speed. And if either engine died the radio controlled the remaining engine directly.
Thank you, but NO I do not want to know how to do this mechanically, I have a different application that needs the precision of the above box.
TIA Tom
I recall a magazine article a decade or two back in which a digital box was used to put a pair of engines exactly in sync. You placed magnets on the drive shafts, and the box used a second servo to match the RPM of the stronger engine to that of the weaker engine. Your radio controlled only the weaker “master” engine. There may have been a little lag in the acceleration but at stable RPMs the two engines turned at the same speed. And if either engine died the radio controlled the remaining engine directly.
Thank you, but NO I do not want to know how to do this mechanically, I have a different application that needs the precision of the above box.
TIA Tom
11-07-2003 | 06:58 PM
#3
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From: ames, IA,
RE: multi engine electronic synchronizers?
I installed the Jomar unit on one of my TwinAirs about 6 years ago. Let me first say that it does exactly what it's supposed to do. However, after about 20 flights or so, I de-commissioned it because I felt it caused me to have much more frequent engine-out situations. My completely non-scientific and unproven explanation is that the unit caused the "slave" engine to constantly seek the rpm of the "master" engine (just as it's supposed to). Because a smaller glow engine (in this case the OS .25) has a relatively unstable rpm profile, there was a lotta seekin' goin' on, esp at times when during throttle-down maneuvers, the slave engine might burble a little and be given a big throttle blip to "correct up" at the worst possible time..hence die.
I theorize that larger glow engines, or esp. gassers that I fly now would be much less susceptible to this problem, but I've stuck with independent mechanical tuning, which gives you off-harmony at some mid-throttle points, but I've found that twins fly and sound OK if you get the high and the low end close and leave the middle alone, as long as the engines and the linkages are identical.
Like I said, all the above is unproven opinion. It just goes along with my BTP (basic twin philosophy), that THE MOST important thing is to keep both engines running, and keeping identical rpm a distant second.
If you can talk me out of it, I've still got the wires in the wing and the magnets in the backplates.
mt
I theorize that larger glow engines, or esp. gassers that I fly now would be much less susceptible to this problem, but I've stuck with independent mechanical tuning, which gives you off-harmony at some mid-throttle points, but I've found that twins fly and sound OK if you get the high and the low end close and leave the middle alone, as long as the engines and the linkages are identical.
Like I said, all the above is unproven opinion. It just goes along with my BTP (basic twin philosophy), that THE MOST important thing is to keep both engines running, and keeping identical rpm a distant second.
If you can talk me out of it, I've still got the wires in the wing and the magnets in the backplates.
mt
