RCU Forums - Tachometer

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ORIGINAL: Campgems

Matt, my problem is outside with bright sun. It looks as if it needs more of a light/dark transistion than the Magnum does. Oh well, I have two now;)

Could just be an issue with a dodgy light dependant resistor in yours... or it could be the prop you use. I generally use mine with MAS props which are black with wide blades, so would offer good contrast. With a lighter coloured blade, or if you're holding near outer edge of a narrow tipped prop it'll be more prone to error.

I'm not saying it always gives a perfect reading - occasionally it'll jump from 13000 to 2500 for a second or so, and the reading always fluctuates a little so there's a bit of "averaging" done. Still, what do you expect for $20 or so? :D

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LuftwaffeOberst
It's also good to have if you down the road want to fly twins, you can sync the engines better. Also with a tach, you can keep tabs on how hard your engine is working. I also have a Radio Shack IR Thermometer to know how hot my engine is in those " In Cowel " setups. But that's a different topic.

That was my main motivation for buying mine - syncing the twin engines on my Dual Ace (maybe I should have said "justification" - after all, he who dies with the most toys wins! :D) however I've found out (as I mentioned above) that it's actually more accurate to sync twins by ear! There's a certain harmonic "note" that you only get when two engines are running perfectly at the same RPM - it's easy to discern, and you can hear it fade in and out as the engine revs change slightly.

As for the thermometer, I really need to get one of them. What sort of temps do I need to be worried about with engines?

You just can't tune for maximum RPM, you end up to lean. I tune using the pinch method, which takes a little while to 'learn' the technique, but what I end up with is an engine that runs slightly rich (which is good), slightly lower than max RPM, and one that won't quit because it is to lean.

I've tried using the tach, but I don't like doing it that way. I seem to end up with a setting that is to lean, and don't get good transitions, nor do I get good performance on vertical maneuvers.

Don't get me wrong, I do have a tach, and do check RPM with it, but use my ears to tune the high-end. Again, as with other issues, this becomes a personal choice and how we learned to set the engines up.

CGr.

He who dies with the most toys is still dead!!! I have that poster on my shop wall, found it about 20 years ago. :D

OK, now y'all have me thinking again. I can find peak RPM by ear, but I don't know if I am hitting the RPM's (right prop) I should or if I am idling as low as I should. These were the "tuning" parameters I was seeking to dial in. The TNC is a bit pricy, but I'll look around at the other suggestions and figure out how to proceed.

Thanks for the great info!!!

Jack

Quote:

ORIGINAL: Gray Beard

He who dies with the most toys is still dead!!! I have that poster on my shop wall, found it about 20 years ago. :D

And think of the yard sale you are going to miss when you are gone:(

Don

HAHAHAHAHAHAHAHAHA I never thought of that. I really hate to miss a good sale!!!:)

Gene, just think, it's going to have "almost" everything you ever wanted:)

My wife told me once, "Don't you dare die and leave me with all that S*&( to get rid off", and that was before I got back into RC airplanes again and I now have a whole new load added to the colection. And what a yard sale it's going to be.

Don

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ORIGINAL: Sandmann_AU

Quote:

ORIGINAL: Campgems

Matt, my problem is outside with bright sun. It looks as if it needs more of a light/dark transistion than the Magnum does. Oh well, I have two now;)

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I use my ear as well, then I check with the Tach. If one engine's RPM is slightly higher than the other... then I will richen the faster motor where it matches the slower engine.

I do the pinch test to one motor on the first run to see if I have it adjusted right, check with the Tach... then I do what I wrote above. I guess I have to write things in detail on how I do it... right? :eek:

On the question about engine temps, it all depends on what motor you are using. I put my engine on a test stand and get my initial reading. When I do another reading in a In-cowel motor, I know if it's getting enough air flow over the cylinder. You don't want it much hotter than you first initial reading. Also putting a prop that is too big for the motor... or too much pitch can make a engine over heat and work harder as well, resulting in damage down the road.