fledermaus

I have the Hangar 9 Twotter with EVO 36 glow engines. I am planning to build floats for it this winter and have been looking at how to steer it on the water. I could just put in water rudders but REAL Twotters use differential thrust.

There's lots of examples of e-power set ups for differential thrust, but I can't find much for glow-power. Is there any problem doing something similar with glow engines, mixing two separate throttle channels as slaves to the rudder channel, with a switch so that the mix is not enabled during flight? What I am wondering is whether one can set this up only to INCREASE the throttle on one engine without decreasing the other one, because that might actually kill the engine if you are taxiing at idle?

foodstick

You know I have always wondered about trying something like this on a single engine plane, Just to play with..but I never did.
I can see where it would offer even more options to experiment on a twin.
I always figured somebody has tried it? But I have yet to see it mentioned..

v22

My Feedback: (8)

I have not done this to steer a plane ..but have done it for roll control on a VTOL I did many yrs ago and it worked fine ... I actually was only using one motor as the roll controlling motor with a gyro hooked in to the servo and it worked great , so I see no reason why one motor reved up without the other one doing anything would not steer a float plane on water very well .

langerl

My Feedback: (5)

Hi Maus,
If you look into the Twin Synch system (TBM site) you will find that there is an option in the programming that allows the differential throttle (engine) steering that you are looking for. You can use it on glow motors, but the Twin Synch hardware does require installation of a Hall Effect sensor on each motor/prop hub. This is in effect a magnetic pick-up for counting engine RPM, as in almost the same system used in most gas engine electronic ignition modules. Besides allowing you to synch your engines, and do the differential throttle steering (at a programmable 0 to 40% throttle) you also get the insurance of a twin engine throttle failsafe function. This function essentially pulls the throttle of a remaining (good) engine in the event of a flame out of the other. The net effect is to give you a momentaryidled singleengine"glider" instead of a snap spinwhile you aresetting up for single engine flight with rudder and aileron trim / corrections. When you are readyforit, you just push up the throttle (adding power to the idled good engine)and look for the nearest runway approach.

Check it out. I've got Twin Synchs (sp?) on all my big twins; won't fly them without the system.

Disclaimer: I do not now nor have I ever worked for TBM or the Twin Synch developer. I have however helped one of the system Beta testers during exhaustive system certification testing. It really works.

Hope this helps you out.

Regards,
Lynn

fledermaus

Lynn: sounds interesting. I had not heard of this Twin Synch system before but it makes sense. I've been flying my Twotter on wheels with a single throttle line and had no problems - touch wood - with engine out so far. It's just a matter of time, of course.

Without the Twin Synch system, I guess my concern would be that simple rudder to throttle mixing would cause both opening and closing of the throttles as the rudder goes left or right. If you close down the throttle of an engine already at or near idle, it could stall the engine. The e-power people don't have this problem of course, but since this plane was built for glow I want to keep it that way.

langerl

My Feedback: (5)

Yes, if you mix throttle and rudder with a conventional radio, I suppose you will always have to worry about throttle if you use your rudder at all; however, some radios may allow for a conditional link i.e. disable the link at a certain throttle setting or by selectable switch. The beauty of the Twin Synch is that you can disable the differential throttle and rudder link at any particular throttle setting. If I recall you can do this between 0 and 40% throttle. After the condition is met or exceeded, the linkage is disabled. My friend used this feature to great success in managing take offs on his Ziroli D-18 (Twin Beech). It was almost unsteerable on T.O. until he set up the differential throttle -rudder link. From that point it was a *****cat on take offs. I DID however wonder how this function worked on low power approaches. It wouldn't do at all to have differential throttle response on slow landing approaches! Perhaps there was also a switch enabled Twin Synch operationthat he used on landing.

Anyway, if you're interested, you can go to the TBM site and download the Twin Synch manual. It will provide you will all the info you may need....and then some. There's also a very long running Twin Synch users thread running on the Twin Forum. Loads of info there too.

Good luck.

Regards,
Lynn

Wayne22

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I know guys that have been using differential thrust for years on glow and gas powered flying boats and floatplanes. It is a mix that is turned on at low speed on the water..how you do it depends on your particular radio and your channel assignments - but it is very do-able.

fledermaus

Well, I think I will look at how my JR 8103 (yes, I am old-fashioned) can be programmed to see if I can have it increase the left throttle on right rudder and the right throttle on left rudder without any decreasing of the throttles. It is easy to set up a mix that I can manually switch on/off, that much I know.

The Twinsync looks really neat however, and it is only about $100 which might be an easy alternative if the mixing is a pain in the *ss.

Prairie Mike

I have mixed the throttles to the rudder and turn the mixon/off with the landing switch. (JR 783 & 8103). I just use it on the ground for taxi. Don't want that feature in the air since I use the rudder during flight. Have had guys scratch theirs heads trying to figure out whats goin' on while taxiing.
You could easily do the same thing for water taxi.

Wayne22

My Feedback: (2)

if you run into problems, contact this club...they should be able to help you out
[link]http://www.slams.ca/[/link]