Throttle Quadrant Design

[Toobuilder]

I never have been a fan of throttle quadrants, particularily the rudementary levers that are the standard issue on these kits. For cross country flying, I have found that the very fine adjustments offered by vernier controls are essentially a requirement. However, I'm also getting more involved with formation work, and can now fully appreciate how a vernier throttle, while functional in a pinch, is less than optimal for constant adjustments.

Pictured below is my "best of both worlds" solution to my cross country and sport flying mission.





The throttle lever is a simple tubular weldment hinged at the floor and running in teflon washers. The lever provides long throw for fine power adjustments and is ergonomically correct for me. Its also a substantial piece that provides very nice feel. The grip is a standard bicycle grip that happens to match the back seat stick grip. The button on the end drives the boost pump on this airplane, which helps with the Lycoming hot start slight of hand action. Prop and mixture are low and behind my knee for a touch more legroom than I had before, and they are available to the backseater in an emergency. An easy push with the foot gets full rich and full RPM.

I now have over 26 hours of cross country time (to Key West and back), and am quite happy with the setup. The mixture is a bit too low, but I plan on doing a whole new console cover in composite, so that will be corrected then.

Anyway, I figured some of you might find this interesting and/or spark some new ideas.

Oh, and in case you were wondering about the red lever in front of the throttle, that's my tailwheel lock. When it's in the free swivel mode, it stands straight up and directly in the way of the throttle. If I happen to miss locking it before takeoff roll, the advancing throttle will knock it over center to the locked position shown.

[David Paule]

That's very nice and I like it.

I've noticed that several builders are using vernier controls for the mixture or prop governor and a lever for the throttle. On my non-RV, the vernier mixture is a bit too coarse while the vernier governor control is excellent.

Thanks,
Dave

[ronschreck]

Very neat installation. More and more of us are seeing the utility of this arrangement.

I don't see any provision for throttle friction on your setup. Is that an issue?

[Toobuilder]

Dave - Concerning the "too course" aspect of the verniers, I took care of that by adding an extension to the mixture arm. This ensures that I have the full stroke of the cable to actuate the mixture arm. The ACS units that I use have a 3 inch stroke, and even using the longest factory bolt hole position on the servo, full rich to ICO is only a bit more than half stroke. Lengthening the arm essentially doubles the resolution.

[Toobuilder]

Originally Posted by ronschreck

Very neat installation. More and more of us are seeing the utility of this arrangement.

I don't see any provision for throttle friction on your setup. Is that an issue?

The friction is provided by tightening the pivot bolt and pinching the teflon washers. It's not in flight adjustable, but it seems to be a set and forget issue so far. We'll see how it holds up in extended service.

...And thanks, gents, for the kind words.

[David Paule]

I'd be interested in a photo of the extended mixture arm, sometime when it's convenient.

Thanks!

Dave

[Andy Hill]

Interesting thread

RV-8 now has (Andair) throttle and Vernier Mixture/RPM. Would not change back, and RV-3 is being built identically...

Issues to consider over discussed above:

1. Finding cables with >2" throw might be an issue
2. If you use a Precision FI unit, NB the range of Throttle & Mixture Arms available
3. Vernier Precision is one matter, but also consider "freeplay" and other slack in the system - can somewhat negate any real precision

However, you are in for cost and complexity over a simple 3 lever quadrant...

[vlittle]

Michael has effectively eliminated a problem that most quadrants have, which is the coupling between the controls.

Having totally independent engine controls is desireable, especially in formation where you want free throttle travel control but firm prop and mixture.

If I were to do it again, I would ditch the quadrant altogether and go with independent controls.

[Tom Martin]

Nice job Michael! I made the quadrant for the rocket I am flying now. The throttle and prop are together and operate with levers. The mixture is mounted separately on the plane and is a vernier control. This arrangement has worked well for me; it is nice to keep the mixture away from the action! Occasionally, with all three levers in the quadrant I have inadvertanly moved the mixture when I meant to move the prop, not often, but it has not been an issue with this current set up.
With two levers only in the quadrant I have been able to avoid the "creep" that Vern mentioned that can happen between the levers. The picture below was during construction, the next after flight and with the covers on.
The lighter wood is Black Cherry, the dark wood in the handles is from Black Walnut, both pieces from trees on the farm.
If I was doing a lot of formation work I would most definitely consider a single throttle lever.

[JanRV6UK]

What about a 3 leaver quadrant that have independent friction adjustment for the throttle - to allow it to be operated freely and a separate adjustment for the prop / mixture.

Would that be an advantage ?