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Twin ic throttle mixing

Futaba transmitter

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Jon - Laser Engines15/05/2019 08:21:26
4775 forum posts
179 photos

Couldnt agree more. Get the mechanicals right then used the software we now have available to ice the cake and add the cherry. If you try and bake the cake with the software..well, good luck with that.

gillyg115/05/2019 08:29:33
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118 forum posts
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I agree chaps.mind made up, set up the mechanics correctly, and shouldn't have a problem, thanks for everyone's input though. Much appreciated.

Chris Walby15/05/2019 08:31:48
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954 forum posts
228 photos

I don't have a issue with the technology per se as with the retracts it allows individual setting up that would take 10 time longer mechanically.

Its the human element (me!) that spent quite a lot of time getting the system to do what I wanted it to do and now + 6 months down the line I can't remember quite what I did. There lies the risk of me doing something and inadvertently changing something else....In the quite corner of the workshop I would probably twig what I had done, but at the field....not so sure.

So not an issue (for me) if its done and dusted, but is if I have to go back and work out all the sub trim, mixes etc later on..

Charles Smitheman15/05/2019 12:38:12
226 forum posts
18 photos

I manged to mix the throttles on my Ripmax Harmony using my Futaba T14SG. The only thing I have failed to get to work is engine cut on the second engine. I did write down how I did it. It was a pretty agonising process for one who prefers carving balsa.

One reason for bothering with a twin i.c. is surely the challenge of being ridiculously complicated. We could just stay home and watch the telly after all. But each to their own.

I had a goal with mine, after watching a video on you tube of a Pica Duellist doing a 540 degree "stall turn"

I think that most of my clubmates thought me mad and probably dangerous, but I have managed the manouver on a few occasions, and the model still survives!

I enjoyed the challenge, yes it was worth it smiley

Chris Walby15/05/2019 13:34:37
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I have tried throttle mixing on a small electric twin as it has no rudder servo, from memory it produced some very non scale yaw/pitch effect which was most unpleasant and fly. Not needed as it was a land launch so no benefit to taxiing either! laugh

Jon - Laser Engines15/05/2019 14:40:09
4775 forum posts
179 photos
Posted by Charles Smitheman on 15/05/2019 12:38:12:

One reason for bothering with a twin i.c. is surely the challenge of being ridiculously complicated.

i think i have been doing this too long as i consider an ic sport twin to be no more complicated than a trainer. Its either that or the fact that models like my P39 have up to 5 servos, 2 sequencers, 2 air tanks, a spool valve and miriad of pipes etc just for the retracts. I have even taken to chopping up my cowlings into several bits as apparently one isnt good enough.

Dont worry, ill show my self out.

Nigel R15/05/2019 15:48:34
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2985 forum posts
471 photos

I'm only planning on the usual 4 channels for my sport effort with a Y lead for the throttle servos and to spend a little time getting everything as mechanically identical as I can.

Jon your P39 retracts sound more complex than most entire models in my fleet!

Martin Harris15/05/2019 16:33:53
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8740 forum posts
214 photos
Posted by Chris Walby on 15/05/2019 13:34:37:

I have tried throttle mixing on a small electric twin as it has no rudder servo, from memory it produced some very non scale yaw/pitch effect which was most unpleasant and fly. Not needed as it was a land launch so no benefit to taxiing either! laugh

One of your clubmates did the same on his hand launched Mosquito and was quite happy with the results.

Reading some of the posts above does raise some thoughts though. Mention was made of the effects of over complication and its just possible that I might have suffered from just that with my throttle mixes. It could explain an unfortunate incident...

A couple of weeks ago on a very gusty day with a fearsome crosswind, I decided to exercise my superior skills with my Slim Twin and impress my clubmates with my mastery of the air. In hindsight I might have wondered why the Red Kites, who regularly watch our pathetic attempts at aviation with a look of avian disdain, had decided to view my antics from the safety of their roosts in the nearby woods...

I took the precaution of lining up diagonally across the runway into wind, opened the throttle and the model leapt into the air immediately - no real surprise in the strong wind as it is off in a few lengths even with no wind. What was a surprise was the immediate roll to port which failed to respond to aileron. The result was an undignified arrival on one wingtip and a cartwheel.

I put it down to the effects of curlover from a nearby hedge and mishandling at low airspeed but on thinking some more, I'm wondering if I might have left it in No.2 start position. That would have resulted in a yaw to the left as both engines would continue to run with the No.1 (port) engine only idling which combined with an initial roll due to turbulence fits my recollection of panic the flight.

I don't recall finding the switch in that position after picking up the pieces or having suspicions that the port engine was not contributing its fair share during the couple of rather fraught seconds that the flight lasted but it would fit the scenario and perhaps act as a reinforcement of the warnings that with complication comes the greater possibility of making a mistake. I still like the ease of handling during starting (and the positive effects of asymmetric mixes) and will continue to use the various mixes but it highlights the extra awareness that you need.

Jon - Laser Engines15/05/2019 16:42:58
4775 forum posts
179 photos
Posted by Nigel R on 15/05/2019 15:48:34:

Jon your P39 retracts sound more complex than most entire models in my fleet!

It was all in the name of keeping the engine cool. I needed the u/c doors to function to stop the air going the wrong way. Strangely the cooling and doors have been totally reliable when they were the thing i was most worried about!

Martin, its another reason all of my models are the same and the throttle is the throttle. I have one powerplant per model, even if the powerplant has 4 individual engines it is one powerplant. Switches are all in the same place and i use the same procedure for all of them. In some cases i even flick to high/low rate for takeoff or landing even on models that have no other rate set up. Its just to keep the habit and prevent me forgetting something if i have not flown the model for a while. Its something i recommend to all new warbird pilots. Unless you can find the gear and flap switches blindfolded leave it on the ground. You dont want to be fumbling around looking for switches on the first climbout.

cymaz15/05/2019 16:57:37
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8586 forum posts
1161 photos

Try setting the throttles with one servo for this...

face 21

cyrl1-e1511033166910.jpg

gillyg115/05/2019 17:36:55
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118 forum posts
17 photos

That looks nice cymaz, what is it? Home design or plan/kit, and what size engines, / wingspan? Would be interested. thumbs up

gillyg115/05/2019 17:40:14
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118 forum posts
17 photos

By the way chaps, what are we using for all the connections between wing and fus, as in so many servo leads or multi point connectors, and I'm not going sbus before anyone suggests it.

Peter Miller15/05/2019 18:22:25
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10076 forum posts
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Posted by cymaz on 15/05/2019 16:57:37:

Try setting the throttles with one servo for this...

face 21

cyrl1-e1511033166910.jpg

Not a problem!

This model had four engines all worked from one control. They were four G-Mark 12 twin cylinder engines. They worked a treat. Admittedly it was control ine so they all worked from on bellcrank but on servo would have done the same job

b-17 1.jpg

cymaz15/05/2019 18:29:33
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8586 forum posts
1161 photos
Posted by gillyg1 on 15/05/2019 17:36:55:

That looks nice cymaz, what is it? Home design or plan/kit, and what size engines, / wingspan? Would be interested. thumbs up

Here is the write up about it. Thanks for the interest

EvilC5718/08/2019 12:32:36
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25 forum posts
13 photos
Posted by Martin Harris on 14/05/2019 15:49:13:

Starting is where I find the ability to control the engines separately has some particular advantages. I have a 3 position switch which is set to idle starboard, idle port or full control on both.

I start the port one first, check it for full throttle running and then switch control to the starboard engine, locking the port one to idle. I then start and check the starboard engine and then activate both throttles for a full power check. Having the running engine locked at idle means I can manipulate the throttle on the one I'm starting with no sudden surprises!

I can also practice engine outs with the switch selecting either engine to idle.

Having the ability to throttle back an engine can also add to the repertoire of an aerobatic twin...

I'm afraid I don't know whether your transmitter is capable of this level of sophistication.

I balance by ear - but I'm more concerned with reliable operation than getting the RPM to any particular figure and I can't remember the last time my tacho came out of my modelling box.

Edited By Martin Harris on 14/05/2019 16:00:45

I like the sound of this, has anybody ever set this method up using a DX8, and if so, how?

Chris Walby18/08/2019 13:37:58
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954 forum posts
228 photos

DX8 gen 1, I don't think so

DX8 gen 2, I would have thought so....and you intending on using for starting or flying?

EvilC5718/08/2019 13:49:06
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25 forum posts
13 photos

Gen 1 unfortunately, so it's a non-starter for me then (excuse the pun).

Starting primarily, as per Martin's OP. Also, as Martin says it allows you to practice engine out situations at a safe height before you are forced to when one cuts at an 'inconvenient' time.

Sheepish18/08/2019 13:55:31
10 forum posts
1 photos

One possible way of doing this is using the heli canned program on a programmable TX.

I did this many years ago with an old JR X-347. I had a Chris Golds Lancaster and set it up with the inner engines on one servo as the throttle on the heli set up and the outer engines as the pitch servo on the same heli program. This allowed me to have hold functions, throttle cuts and throttle curves on the pairs of engines. The Lanc never worked out that it wasn’t a heli

I am just getting to grips with Frsky now and I guess anything you can think of would be possible with that if you have the time to spend working it out. angry

EvilC5718/08/2019 15:06:03
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25 forum posts
13 photos

OK thanks Sheepish. I read somewhere earlier today, that sometimes this can be achieved in Heli mode. I'll investigate...

Sheepish18/08/2019 15:14:10
10 forum posts
1 photos

I hope this solves your problem. I wanted to be able to simulate engine cuts and throttle inner and outer pairs separately and also be able to cut pairs of engines on the Lanc. This was all possible but it did require a bit of creative thinking and me remembering the translation between heli terms and fixed wing terms in the program.

It will be interesting to see what you end up with.

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