A Different Escapement Setup.

[iflylilplanes]

A new plan popped up on Outerzone "Little Ship" https://outerzone.co.uk/plan_details.asp?ID=15303 the RC setup, I have not seen before, a free floating/rotating control surface. If I have this correct, the article with the plans is a bit uninformative, it uses a sequential escapement with a rotating control surface, trimmed to fly a slight left turn long side up, press and hold is either up or down elevator, release right rudder, press and hold again up or down elevator, and lastly release back to slight left turn.

Have I got it right?

[Shaun]

Dave, It's called a rudervator.
Ok on slower models but never really caught on..

[Mike_K]

The Mercury Cossor was the first commercial UK R/C set in 1947 and was a Ruddervator design. It was an attempt to have rudder, elevator and throttle (cut) control with a single-channel CW set.

The transmitter had an 8-position rotary switch marked: D (Down), N (Neutral), R (Right), N, U (Up), N, L (Left), N. The switch was quite simple, it had to be rotated clockwise, one position at a time and in between the 8 positions the switch opened a pair of contacts with a cam and follower and it transmitted a CW signal. At the aircraft end the receiver operated an 8-position escapement with a shaft and what looked like half of a propeller blade. In four positions it was free to rotate (in the slipstream) and in the other four positions, it stopped. When escapement stopped, the ruddervator acted either like a rudder if it stopped vertically (with its shape if it stopped vertically up then right, down left) or an elevator if it stopped horizontally (again up or down depending on which side it stopped).

The operation must have been "interesting", before the flight you would need to ensure the switch position and escapement were "in sync". You would launch with the ruddervator freely rotating, then when you wanted control, you had to rotate the switch slowly to the desired position. If you had previously selected left rudder and wanted left rudder again you had to go all the way around the switch again, slowly enough for the escapement to keep up. If the receiver got interference, the escapement could operate and get out of sync and ahead of the rotary switch. If say you were in neutral position before right rudder and interference moved the escapement to right rudder, you could not simply rotate the switch as it would move the escapement on to neutral position before up elevator. What you had to do was turn the transmitter off before rotating the switch so that it didn't transmit while the switch "caught up" with the escapement.

The throttle control was really throttle-cut. In the neutral position before down elevator on the escapement, there was a delayed action set of contacts that would cut the ignition (it was expected that it would be flown with petrol/gas engines), so you would have to wait in that neutral position. But that meant after right rudder, you could not linger around in that neutral position, otherwise, your engine would stop! You would need to go through the down elevator position to the next neutral position if you wanted straight and level.

The Mercury Cossor sets never caught on because they all had faults with their Cossor manufactured valves (tubes for our American friends) and by the time Cossor had sorted the problem ED and ECC had become dominant in the UK. For most models of the period, simple rudder control was far more reliable and only a few years later Rockwood/Schmit launched a reed set in the USA, so full control was available without the complications of a Ruddervator.

If you want to read more about Ruddervator rcfiles.com have some articles from MAN 1948 and 1950

http://vintagercfiles.com/EarlyRCarticl ... rticle.pdf

http://vintagercfiles.com/EarlyRCarticl ... rticle.pdf

http://vintagercfiles.com/EarlyRCarticl ... rticle.pdf

and all the early info on rcfiles

https://vintagercfiles.com/Early_RC.html

[iflylilplanes]

Thanks, Mike for the explanation, sounds like a system for a slow flyer. Not planning on it but, is this system something that can be replicated with modern RC technology, has anyone tried?

[Martin]

It would be easy to use two servos to operate 'rotation stopper pins': one servo would work two pins that stopped the rotating vane at either 12 'o' clock or 6 'o' clock (or neither with the servo at centre). That would give rudder control. Similarly, a second servo could operate stopper pins at the 3 and 9 clock positions for elevator. You could use a normal proportional transmitter for test flying, though the control operation would be all or nothing, and, of course, if you operated rudder and elevator at the same time, it would be pot luck which one you got, depending on where the rotating vane happened to be when the servos moved.

So, using modern proportional gear, you could get slow and clunky non-proportional control: what's not to like? I might just try it, just to be different!

[iflylilplanes]

It sounds like fun, I may have a go as well.