Gentlemen,

Some of you may have seen My posts on Electric Speed.  I would like inputs from those of you who have used Castle ESCs' Brake function.  I want to to stop my prop horizontally as the airplane slows from about 125 MPH to landing at maybe 40 MPH after a lap or so glide.  The motor is an AVEOX 1415-2 which has magnetic centering that mimics a flat 12 four stroke engines compression.  Without any Brake input the 8/8 prop barely seems to slow during the glide.

I'll be calling Castle next week so it would be good to know how effective the brake settings are in stunt.  Does the prop tend to stop?  How different are the settings?  If the prop does stop, does it seek any particular position?  I could come up with a position sensor to tell when the prop is horizontal; also some kind of pin/disc setup on the spinner which would move forward when power is cut (but sure would prefer not to!).

Any suggestions?

Thanks,   Will Stewart

Alan,

I'm glad the brake works fine for you.  Does fine mean that the prop stops?  In flight?  In the same postiion?
What brake setting, etc...

Will

One thing that comes to mind is that the timer has an extra servo function (they call it a "retract" gear feature). I was thinking whether it might be possible to use a microservo to push out a plastic stop into the prop arc after the motor was throttled down (that might take a little experimentation with the different timing periods in the timer). Of course this is a big complication.

Alan,

How about a switch in the retract path. Determine the interval for the retract to function (ie: retract) and after that interval activate the switch to allow the retract to deploy at the proper time. Humm, I think the motor continues to run after the deploy of the gear so that would be a PROBLEM!!

My guess is that if you turn Will Hubin loose with this problem he can come up with a timer that deploys a servo to stop the prop just after the brake is activated. Can't speak for Will but this just might be a challenge he would rise to.

John 

My experience after 2 years of flying Electric F2B is that the brake function on various ESCs takes the revs back to 2 or 3 per second while gliding in for touchdown. At that point the prop usually stands still. It's adequate enough for the judges to see that it's not a landing glide under power. And that's all the rules require.
The brake function works because the moving magnets are inducing a current in the windings. By shorting these, a counter-torque builds up that works against the movement of the magnets. At flying speed ( just after switching off power) this torque cannot entirely overcome the driving power of the (then) windmilling prop, but there's a good braking effect anyhow.
It will be a lot more difficult to stop a prop on a speed model, because the forces that are driving the windmilling are considerably higher.

Alan,

In full scale flying, over the years, I've experimented with windmilling of fixed pitch props, and have heard tales from other pilots as well.  Generally an engine in normal mechanical condition will windmill in a glide and can be stopped by slowing and pitching up.  It will remaind stopped (providing improved L/D) until restarted in a shallow dive.

I gather that the braking function is proportional to RPM and vanishes when the prop is stopped, with motor magnetics holding the prop in position as speed bleeds off.

This may work for me unless the prop stops vertically.

Will

Hi Will,

Glad you joined the discussion.  Your timers are working very well for me. The one in my B ship has the pushbutton bypassed since, somehow I managed to have a drop of CA fall on it.  Anyway, your suggestion of a rod moving forward on brake application at the right side of the motor shaft axis, to intersect the prop (or perhaps a contoured spinner backplate) is the best so far.--Maybe a disc with two holes.

As things stand now, my airplane (pictures elsewhere on the Forum) has a forward wire skid long enough to protect the prop, but soft enough to bend on every landing (either I land too hard, or the length of 1/8 music wire was not properly tempered).  I have now made a plywood panel, carbon fibered to the front of the wire and the bottom of the fuselage.  Since it is close behind the prop, its contoured like a stator in cross section.  Possibly it will stabilize the wire enough, and recover enough momentum to null out its' drag.  We'll see at the December meet.

I don't want to reprogram  my CC ESC for brake yet, but will try the brake after the meet.  If the prop stops for me, the next step would be to discuss the prop-stop function.

Best regards,  Will Stewart

AFAIK, there is no reason not to use a brake, now that the new CC software supports it. What I have chosen is a hard brake (full on), with a "gentle"turnon--but minimum delay. I don't recall the exact terms in the software, but there are three parameters as I indicate. You do want the brake to come on smoothly and not put full braking power in one blast--prop might go spinning off!

Just run a nyrod pushrod (nylon sliding in a nylon tube) forward from the servo.  Small enough to get past any motor, easy to install.  If the motor is not trying to run, it will be strong enough to stop a speed prop.  It might not stop an 11 or 12 inch folder, though.  We tried it on an RC glider back in the early '90's and the aluminum prop hub was just cutting the nyrod off.  When we tried putting some wire inside the nyrod, it would break the nyrod out of the fuselage nose ring.