DJM Manufacturing Throttle Quadrant Installation

I'm one of those wackos who has to have the throttle in his left hand, despite the side-by-side seating. It just doesn't feel right otherwise. Yeah, yeah, I could adjust, but why bother? Anyway, when I originally built the plane, I installed a left-handed throttle quadrant. It was a standard three-lever setup that I bought for about 45 bucks. It did serve the purpose just fine, but it's time to spruce things up a bit. Besides, I wasn't 100% happy with the geometry of my original installation. The friction knob just barely contacted my left knee when my feet were low on the rudder pedals. And "just barely" is really "way too much" when it comes to discomfort. That, coupled with the fact that my throttle and prop cables were trashed inside and needed to be replaced, was my rationale for taking on a little cockpit improvement project.

I removed the old quadrant, exposing the control cables and clevis ends.

My goal was to stick with the cable and custom bulkhead setup, because I invested an ungodly amount of time making that right. All I needed to do was raise the new quadrant up slightly and tilt the top in and the bottom out a little more than the old one was oriented. I had to enlarge the pass-through hole in the panel a bit (not shown here, this photo was taken before the enlargement) so that the cables and clevis nuts would clear.

This is the old quadrant. I recently recall hearing somebody compare the knobs to a "Lincoln Log" set. That's about right! This is definitely not the fanciest or best looking setup, that's for sure. Also, the levers are pretty long. While that can be a good thing with respect to leverage, it lets the arms flex a little too much...this became an issue when my cables got gummed up.

I have three other gripes about this quadrant:

  1. The clevis pin holes in the arms are aligned on all three arms. While that does ensure that the throws are even, it's just not necessary in my opinion. You'll see a better way of doing it in a minute...
  2. The clevis actually rubs the top of the quadrant as it passes through center. It doesn't add noticeable resistance, but still, that's not cool. It's partly due to the angle at which I mounted the quadrant, but it could use a little more clearance.
  3. The sides, while beefy (probably overkill in thickness), only have little holes for slipping the clevis pins into place. That means you need to come in with a tool (I use needle nose pliers) from behind (or in front) in order to install the cotter pins in the clevis pins. Access is a pain in the butt. Not all that difficult, but it could be way easier if the sides were open. I could have easily cut the sides open myself, so I guess I shouldn't whine about this too loudly since I didn't attempt to make it better. But it's an undesirable feature out of the box, so to speak.

Enter the replacement...this is not your father's throttle quadrant! This is the SMCT3L (side-mount curved-top 3-lever) quadrant from DJM Manufacturing. DJM is Dayton Murdock, a machinist who happens to be an RV builder himself. What better way to go than supporting an RV builder who makes a fantastic product?! This puppy is superior in every way, to boot. The first thing that grabs you is the set of beautiful anodized aluminum machined knobs. They are nothing short of works of art.

The frame is made using black anodized aluminum, with thinner and wide-open sides. The levers are drilled staggered. The clevises don't come anywhere near the top.

The friction mechanism is more sophisticated and works better. It's smooth all the way through the range at all friction settings.

On the old quadrant, the friction bolt is just sliced off on the outside of a nutplate. On this new quadrant, there's a special retaining nutplate that holds the friction bolt in place. Much cleaner design.

The engraved and white painted labels are aesthetically appealing and obviously functional. (My previous quadrant had no labels whatsoever other than the painted knobs.)

Let's cut to the chase. After much fiddling and playing around with installation angles, I took some measurements and fab'd up a ridiculously simple mounting setup.

I had hoped to use the existing nutplates in my instrument panel, and it ended up working out that way. The angle on the right side is just a piece of .063" thick 6061-T6 angle, bent open to about 105 degrees, and sliced at just the right angle to tilt the quadrant back at me a bit, toward the left side of the fuselage, and to tilt the bottom outboard. The angle bracket bolts right to the quadrant.

I'm glad I installed those three nutplates inside the F-704 covers on the side of my fuselage! I knew they'd come in handy someday. On the left rear corner of the quadrant, I just installed a little "twisted" piece of .063" stock. That third mounting point makes the quadrant fully rigid relative to the fuselage. Much cleaner than the old quadrant's mounting setup, which was only screwed to the panel (which allowed it to flex a bit).

I bent the throttle lever to the left a bit so it wouldn't be as tilted over. It's very comfortable this way.

You can see how easy access is to the clevis ends, clevis pins, and cotter pins. While I was getting the cables set up, and while I was measuring for and installing the rear mounting point, I had the quadrant on and off several times -- and having wide-open access to the connections sure made quick work of it. Some people have commented that they would cover the side, but I much prefer to have it open. Easy inspection, easy maintenance, and I like seeing in there.

Dayton asked me how I liked the new quadrant, and I had only positive things to say. He really wanted some sort of constructive suggestions, but I was hard pressed to come up with anything. Dayton is obviously a perfectionist, and he makes a terrific product.

Anyway, I've flown about 16 hours on the new setup as I write this. I wish I had just gone with this DJM Manufacturing quadrant from the get-go. Could have saved myself the hassle. There are all sorts of variations on this type of quadrant. Flat top, curved top, two lever, three lever, center mount, etc. I have always liked the feel of a quadrant, even in the Mooneys and Cherokees and stuff. If I was building an RV with center controls, I would definitely go with one of Dayton's quadrants. Good stuff!

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Dan Checkoway ()