da Rock

A buddy is looking at two things......

1. He wants a B25 with two glow fuel engines on it and wants to trim each engnine's throttle. We've both got radios that have a throttle trim function on the throttle channel, but neither of us have figured out how to put 2 throttle servos on the throttle stick with each being trimmed.

2. He and I both are shopping for new 2.4 JR/Spektrum radios and looking at the DX8.


The questions are: Are there JR/Spektrum that will solve the problem stated in 1. above, and can the DX8 do it?.

BuschBarber

My Feedback: (2)

Ideally, you want a transmitter with Dual Engine programming. Many of the higher end radios have this function. Another way to accomplish this is to use a Programmable Mixer and mix the Throttle channel with another free channel that the second Throttle servo is connected to. Both Throttle servos will work off the Throttle stick, but each channel can be Trimmed individually. You would assign a knob or lever to the second channel, for it's Trim.

Check out Alan's Hobbies. His web site has the most comprehensive list of links to RC information. I am sure he has information on Multi Engine programming.

http://crash.ihug.co.nz/~atong/

ronwc

My Feedback: (404)

I have many glow engine planes with 100's of sucessful flights. Separate throttle trims could probably be done by plugging one of the servos into a separate channel and linking to throttle. However, i have never found the need for separate trims. I use the following tuning procedure which has worked well for me. Start one engine and tune slightly rich, make sure good reliable idle. Shut first engine off and tune second engine separately the same way. In simple terms, get each engine running the best it can. Shut off second engine, refuel, crank both and fly. They may or may not be perfect in RPM sync, but I have never run into a problem doing it this way. I have seen many guys tune each engine, and getting ready to take off hear not quite in sync, reach down and lean one. That is usually the one that cuts off on takeoff, low and slow, and does the death roll in. IMHO, the big key to twins is realiability - if the engines are tuned perfect separately, any tuning after is detuning. I could see some usefullness with throttle trim, but it would be difficult to know which engine is high/low while in the air. Here are a few pics of some of mine, one with 3 engines -

DougV

With the Futaba 8FG, you go to the Function menu and select an empty channel, then assign J3 (throttle stick) to this channel and assign one of the sliders or knobs so you can have separate trims, very easy to do. (Maybe you can do the same with the DX8)

Doug.

AWorrest

My Feedback: (5)

The JR 9303/9503, 11X and 12X all have provision for dual engines where you have the options of having trim on just one engine, or common trim for both engines or separate trims for each engine. Keep in mind that throttle trim on JR transmitters only affect the lower have of the throttle range. If you want to vary the throttle output over the entire throttle range, you’ll have to use a program mix.

Allan