tevans55

I am building a twin engine bomber with DLE 20s. My question is...will it matter if I run both ignitions through the same 2500 mah Nicad. The ignitions would have individual switches with separate leads from the same battery. Each engine will have a servo for the throttle and a servo for the choke. Thanks for any help.

Tired Old Man

My Feedback: (1)

It will only matter if the one battery fails. If that was never to happen you would be G.T.G.

All Day Dan

My Feedback: (5)

I was in to multi-engine models with K&B 61's about 15 to 20 years ago until I switched to gas powered 50cc engines. The most engines I had packed on to a model was three and I was trying to design a four engine plane until I realized that the size was too big. The one thing I always adhered to is if one engine quit, I idled back the other one ASAP because, unlike full size aircraft where you immediately know which engine is still running, you can't tell with models. The big problem is that you can't turn in to the bad engine because in you shall go. If you are going to use one ignition battery for both engines this may help save an airplane when it fails. But with like all batteries, the regular monitoring of a battery's capacity and it's voltage would normally prevent this. In any case, don't think a battery as an open circuit. They all have a resistance associated with them. This means that you are actually connecting the ignitions modules together and that may be your biggest problem. Get in touch with an electrical engineer at your field who is familar with these high voltages generated by the modules and ask him what he thinks before you do it. Please post some images of your project. Since the small displacement gas engines have come out my interest has been renewed. Here's an image of me taken about 20 years ago with one of my planes. Dan.

jedijody

My Feedback: (1)

For 90% of the pilots I see fly twin engines it would be far better for both engines to go out at the same time and come in dead stick. Almost every time I see a flame out on a twin engine installation the pilot winds up making a turn into the dead engine and it's all over shortly thereafter.

av8tor1977

My Feedback: (6)

"Twin Synch" seemed like the way to go for me. Did they ever get the bugs worked out of it?

AV8TOR

a1pcfixer

My Feedback: (7)

I had one of Bill Wike's earier versions, and although he made multiple software revisions, it continued to exhibit glitches.
Throttle servo's jumpy, synch dropping off, variations between the two at idle, used to be some of it's bugs. Hopefully Bill
got it all working better than the early versions. TBM is the exclusive dealer of it now.

Another thing about those Twin-Sync's is that your adding a bunch of extra connections, and the needed wiring.

Best for twin engine models is to have two engines that you've already got well tuned and running great & consistant, on
some other single engine model.....BEFORE putting on your twin eng model!

1) Get each engine running it's best on a single eng model, THEN mount both on your twin.
2) Be sure to have LOADS of rudder movement in case one does die.
3) If one does die, drop back to 1/4 throttle and land fast!

tevans55

Thanks for all of the help. I have been flying a Hangar 9 B-25 for 4 years on OS 46 glows and now I am building the ESM B-25 with DLE 20s. I asked this question because I will need additional nose weight and it would be nice to be able to install the battery for the ignitions in the nose with ample mAh to run 2 ignitions. I am installing a Smartfly 10 Power Expander with dual batteries and wanted to use a third for the ignitions. I will have a fourth battery for the Wingspan bomb drop so I should have plenty of nose weight. I am waiting to see how much weight is needed for balance before I start purchasing batteries.

a1pcfixer

My Feedback: (7)

Ahh, OK....ballast.

But consider what Dan said above about both ign modules being on a common battery source.
Not something you'd have run across on glows.

Ask in the.....
Twin & Multi Engine RC Aircraft
http://www.rcuniverse.com/forum/forumid_192/tt.h

And keep my 3 pointers in mind too.
Good luck!

tevans55

Thanks everyone for your help.

Dan- I will post some photos when I get something built... right now all I have is parts in various stages of paint and rivets!! I do have the H9 B-25 on youtube below. This plane is about 4 years old and flys on OS .46 AX's. I bashed the kit into Doolittle's plane.

a1pcfixer- I have posted my question on the twins forum for this plane and have received no response in several days. I guess this is not a popular idea or it does not work well. I am VP of our club in Louisville and there are no fellows with the education or experience to answer the question.

I am going to contact a few vendors of electrical equipment and see what they think...If you have any suggestions as to suppliers I might contact let me know.

http://youtu.be/hDBp4pfJpGo