Taranis Co-ordinated throttle..... Madness or Genius?

[Dave Hopkin]

Ok, I doing a TN Vulcan with 4 50mm 4S edfs

To avoid multiple Y Leads each EDF is on a separate channel (it works just fine)

As I am not adding a functional rudder a thought occurred to me but I can't decide if its a moment of pure genius or utter madness...

On the Tarnis CH2,3 & 4 are slaved to CH1 which is on the Throttle stick so all 4 EDF's spool up together....

So by adding a mix to each throttle linked to the rudder stick, I power up the port pair of motors on a Stbd turn and power down the other pair, I have set the variance from the rudder at + and - 5% respectively

The rudder-throttle co-ordination can be switched in and out by a TX switch

So you opinions

• Genius?
• Madness?
• Recipe for an unrecoverable spiral dive ending in matchsticks?

[Denis Watkins]

Like other readers Dave, or maybe not, when I Google TN Vulcan, I get a motorcycle description.

I want to assist you with a comment, and wanted to look at the size of the delta you have in mind.

I fly a couple of deltas and they do have peculiarities of their own

[Dave Hopkin]

Its the Tony Nijus 48" jobbie **LINK**

[Denis Watkins]

Thanks for that Dave, it is a beautiful model. I think your logic is genius and works theoretically as the thrust alters, the aircraft would turn, as you have already summised before you made your design.

Immediately I look at the TN Vulcan, and see how close the thrust lines are, they would turn the model but I guess it would be a huge turning circle, and not the responsive immediate turns we often require.

My vote is that you use your proposal on an airframe of your design, that gives you a chance, with the EDFs set outboard as far as possible, thus magnifying their differential in thrust. Am certain you have deduced this, and someone may have installed differential in a Vulcan.

But the control method is your invention so far

Keep us posted

[Dave Hopkin]

I certainly don't expect it to turn dramatically on differential power alone, having done RC ships for a good few years where multiple screws were pretty close to the centre line (to enhance rudder authority) turning on screws alone was pretty gentle (could be increased by reversing the inner screw) but combined with aileron I am hoping it will allow more scale like turns to be made (also it may help if it ends up using a take off dolly for ground steering)

[Steve Jones 2]

I mixed throttle up with rudder to tame my Brian Taylor Mossie on the take off run . Without it was a lottery and nightmare , with 5% mix turned on all take offs straight as a die . Switched it out once Airbourne

Steve

[Denis Watkins]

Apologies Dave, in my mind I took the rudder operation out of the equation when you used that stick on the EDFs,

But you meant to use the EDFs in tandem with rudder.

It is still genius and thinking out of the box on your part.

You mention boats, and they can teach us a thing or two about SOFT mounting IC motors too, making models quieter.

I think RC complements model disciplines and we can learn no matter which fluid we pass through or above

Edited By Denis Watkins on 27/08/2016 19:30:37

[Dave Bran]

I have used throttle to rudder mix to get rudder from the eccentric thrust permitted on more than one twin since 2008.

In fact two of the twins are still on the active list.

One is on a B25 that does not have mobile rudder surfaces and with Mode 2 I can fly circuits using only the left stick, which puzzles the heck out of those who don't know!

[Martin Harris - Moderator]

That system certainly works on a conventional twin. One of my clubmates has been using it on a Mosquito without a rudder for a couple of years without incident. It's very effective but the thrust line differential is probably a lot bigger.

[Dave Bran]

Here is the idea taken to extremes!

**LINK**

[Dave Bran]

Dave H, you will I think be pleasantly surprised just how much steering you will be able to get, that Spin Delta own design has motors that are very close together, and no rudder.................does not seem short of turning effort, does it!!

Edited By Dave Bran on 27/08/2016 20:03:45

[Biggles' Elder Brother - Moderator]

Its a perfectly viable idea Dave - not mad at all. I have done it on more than one twin - with considerable success.

There might be some lag in the yaw response for EDF's compared to props, and I'd agree its unlikely to be very agile - but you should get some useful effect. Go for it!

BEB

[Chris Bott - Moderator]

With a prop twin I found an undesirable side effect in that the extra airflow over one wing gave a big differential in lift. Thus the effect I saw was more in roll than yaw.

You shouldn't have this effect with edfs though.

I did find it very useful for taxiing.

Oh and check your fail-safes. This was a big issue with some spectrum receivers. It's much more straightforward with FrSky.

Edited By Chris Bott - Moderator on 27/08/2016 21:17:26

[Tony Richardson]

Good idea Dave, as you have all the motors on seperate channels and the Taranis is so versatile how about progressively slowing the motors on one side while speeding them up on the other ie turn to the left outboard motor is slower or stopped inboard left motor a little faster / inboard right motor faster still outboard right motor fastest or full throttle and vice versa it may make for smoother turns as the EDF eflux is quite close to the centre line, just an idea.

[Martin McIntosh]

Don`t try to make an already complex model even more so. I have one of these and Y leads are just fine. As stated above, the motors are too close together for differential thrust to be very effective and you should also consider the overall power loss in a turn. I fitted a rudder plus steerable nose leg which is all you need on the ground. In the air you would be unlikely to require rudder on this. Build and fly it `as is` before trying out fancy tricks.

BTW, what 4s packs have you found which will actually fit in that thin wing? Have you considered that the motors are likely to burn out since they will be over driven?

[Dave Hopkin]

Posted by Martin McIntosh on 28/08/2016 15:57:44:

Don`t try to make an already complex model even more so. I have one of these and Y leads are just fine. As stated above, the motors are too close together for differential thrust to be very effective and you should also consider the overall power loss in a turn. I fitted a rudder plus steerable nose leg which is all you need on the ground. In the air you would be unlikely to require rudder on this. Build and fly it `as is` before trying out fancy tricks.

BTW, what 4s packs have you found which will actually fit in that thin wing? Have you considered that the motors are likely to burn out since they will be over driven?

It will be hand launched so ground handling isnt an issue....

As I said each of the 4 edf's are on separate channels with the differential switched on or off from the TX so it will be tried out only once the model is trimmed out

4s 2200 Zippy's fit inside the wing pockets but the normal 4S 2200 turnigy is a little too large - Dont know why you assume the motors will be over driven when I am using EDF's specified for 4S cells.......

[Martin McIntosh]

Hi DAve,

I assumed that you are using the EDF`s specified by TN which he says may not be suitable for 4s but I would be willing to give that a try. I have stayed with Zippy 3s 2700 packs which for that capacity are the slimmest I could find and only just squeeze in.