Q-talk 156 - Mounting Dynon 2-Axis Autopilot Servos

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Category: Q-Talk Articles

Published: Wednesday, 19 December 2012 15:55

Written by Jerry Marstall

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by Jerry Marstall
N625JM

After too many years, I finally got tired of doing unusual attitude recoveries every time I refolded a chart. Time to install an autopilot.

Since I already had the Dynon D-100 and appreciated its reliability, I decided to stay with Dynon and stave off any compatibility issues. Went all the way and bought two servos (pitch and roll) and the AP74 control panel. The AP74 is overkill since everything that it does can be accomplished through the D-100, but its convenience makes it worth the extra $$$.

Now, where and how do I mount the servos? It was actually a very clean and easy process. I began with the elevator servo. Above is a picture of the pilot side of the canard, slightly to the right of the right rudder pedal mount. Yes, mine looks different because I had to elevate the rudder pedals to accommodate my oddly elongated body. Using the plans position for the rudder pedals, my ankles would not bend back enough to push the rudder pedals without depressing the brakes first.

For the forward positioning of the servo, I chose the most level portion of the canard. The lateral position aligns the servo arm with the bolt that attaches the left elevator control rod to the center elevator universal joint. Yes, my universal joint also looks different.

I then fabricated the mounting brackets. After attaching the servo to the brackets, I positioned it in the chosen location and marked the canard through the mounting holes. I then drilled holes into the canard to flox in the AN3 mounting bolts, shown in the first photo. After pressing the flox around the mounting bolts, put release tape on the bottom of the mounting bracket and on the canard around the base of the bolts and gently place the servo, with brackets, over the bolts onto the canard. This does two things. It smashes down the flox to make it smooth with the canard and makes sure you can lift the servo vertically off of the bolts for future removal. I chose not to leave the servo on the bolts while the flox set up. My luck would be I would bump the servo, the bolts would move out of vertical and then I would not be able to remove the servo. This way, if I did unknowingly bump a bolt, I would only have to dig out the bolt and do it over. I felt that approach to be easier than trying to get behind the servo to cut off the back bolt should it have moved out of vertical.

The next step was to connect the servo to the elevator. I simply bolted a strap vertically to the elevator bolt at the universal joint and connected the push rod.

Now on to the aileron servo. How you construct this bracket will depend upon how you built your reflexor mechanism. Mine was simple since my reflexor arm moves vertically from the center of the aileron control arm.

I chose to mount the servo at bulkhead FS95, to the right of the aileron control rod.

With the servo extending into the luggage compartment.

Note that the fuselage beneath the servo bracket needs to be reinforced with several layers of fiberglass. So that I wouldn’t have to do any repainting of the bottom, I bored down through the fuselage foam where the mounting bolts were going to go and positioned the bolts vertically with bolt head directly on the bottom skin of the fuselage. Flox was then squeezed in around the bolt like was done on the canard mounting bolts and several layers of fiberglass were placed across the surface on the inside of the fuselage, the width of the mounting bracket.

All that remains is to fabricate the flat plate that connects the aileron controls to the aileron servo. I butted it up against the original connecting arm to the aileron pushrods. Wire it and calibrate it and you are on your way.

I can now fold charts without making myself airsick. Actually it can make cross-country flights rather boring. But I now get there faster because I can finally fly in a straight line.

Q-talk 156 - A Quickie at Burning Man 2012

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Category: Q-Talk Articles

Published: Thursday, 20 December 2012 12:21

Written by David Smith

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by David Smith (aka "Kairos")
Q2 124AT #2178

This year I fulfilled a dream to take our Q2 to Burning Man and gift rides.

It had been 8 or 10 years since I had the engine off the plane and I figured if I was going to be taking Burners for rides out of a playa dust strip with high density altitude I should give it the once over. Turned out the compression was low in a couple of cylinders even though it seemed to be flying OK.

When I starting pulling her apart, the biggest problem found was the exhaust pipes were rusting through again. I've always kept them wrapped which has been good for all the wiring and controls under the engine. What I have found with the mild steel pipes is where they are wrapped good they don't rust. Even after 10 years some of the metal was blue. But where they weren't covered in a couple of small areas, the rust had eaten so much I could punch a hole with my fingers. The final pipe was easy to see it slowly rusting and getting shorter but the other areas I couldn't see without taking them apart.

The kit was bought in 1981, finished in 1984 and I've rusted through two sets of steel pipes. I ordered a new set of SS pipes from Revmaster which almost fit OK. The biggest problem with them is the turn coming off of cylinder #3 isn't as sharp as the original kit ones and I had to flatten the tube to get some clearance between the tube and the firewall.

Off came the engine from the airframe and removed the mag. The local shop went over the mag but I found out that the single drive Bendix dual mag isn't made any more and parts are scarce. I wanted new wires but they didn't order them in time for my trip but they did find a hairline crack in the distributor block and put the last one they had in along with a new capacitor.

I had the valves redone but the guides were fine. The one thing I wanted to do this time was go through the Revflow carb. It's always been fine except the 0-ring groove in the mixture valve stem was not to book spec and would drip gas while idling at full rich when the o-ring got old. I ordered a new actuator strap, valve stem, and o-ring. Redoing was easy. It's unnerving what little screws hold it together inside.

I pulled the cylinders and pistons and there was a fair amount of crud in the upper ring grooves. I pulled the upper rings and carefully reamed out the grooves and put the old rings back. I don't have a hone but I hand sanded a crosshatch on the cylinders to allow the rings to reseat after disturbing them.

Putting it all back together went straight forward along with the work to fit, cut, fit, cut, fit... the new pipes and having the collector welded on. The engine fired up OK but started running very rich. I adjusted the slider needle which made it idle OK but when I went to fly, it was too lean and I had to go back the other way. It's pretty much back to where it was but is still on the rich side.

Long ago, I put exhaust valve rotator valve spring retainers thinking the faster spinning valves would make them last longer and they did. But after doing the valves again and flying for a while I think I have been way too aggressive in my leaning. I've been running much richer and the compression is not going uneven like it used to.

I gave the airframe an annual and everything was OK so I put 30W non detergent oil in for the test flights which went fine then changed to normal 20-50 oil for the trip. The engine does have more power than before. You don't really notice when it gradually goes away.

And now for Burning Man. The trip across the Sierras was beautiful during the afternoon with little turbulence. I landed at Stead by Reno for the night to see our Son in the hospital there after he hurt himself when a bolt broke on a dome he was building at Burning Man and dropped him 15 feet.

The next morning flying to the festival was perfect and seeing the Black Rock City for the first time from the air was fantastic. You brief yourself before going there on the BM web site and they give you an information call sign so they don't have to go through it all when you call Unicom. It's different every year. This year it was information "Heavy Breathing". Another year I found out was "Whiskey Breath".

I had been worried about flying such a low hanging wheel pant, small wheeled plane there might get me in trouble and it can but it is doable. Landing on the playa on the fairly new runway was easy and felt cushy in a bumpy sort of way. The taxi back is long and you do have to watch out for soft spots. The biggest problem for the Q2 was having one wheel stick in a soft spot while going slow and drag the tail wheel around it. On asphalt, the hard rubber just slides but on the playa the wheel can catch and put a large torque on the tail spring.

I found a place to park with help from the airport volunteers where I had a clear area to taxi to and from the runway. By the way, the "runway" is a fairly smooth part of the playa that’s been marked by cones and a chevron on either end. Some watering and rolling is done but it gets rougher as the event goes on especially where the planes touch down. It's a mile long or more so I started taxiing down a way before getting on for take-off to miss the roughest part. I was amazed, towards the end the little plane would take an awful rattling but everything held together.

Before you can start flying rides, you have to have a briefing about the ins and outs of high desert flying. Afterwards, they give you a wrist band and tell you to use information "After Glow" when contacting Unicom. They also instruct women Burners looking for rides to not give any "favors" to anyone who offers a plane ride unless they have the coveted wrist band or they could be screwed twice.

Most of my passengers were light beautiful young girls as the density altitude can get over 7K when it gets hot, but I did take one over 200 lb fellow pilot (I'm over 200 lbs) with no problem. He was gifting rides in a powered hang glider and we swapped rides. To tour the city you climb to 5500 feet, then approach and circle clockwise just outside the trash fence. All climbs and descents are done well away from the pattern. There is a sharp ridge just to the south that peaks at 5500 feet so I would play around with that to give some thrills.

It gets really busy in the mornings till noon so you have to watch out. Fortunately the ultralights use a lower pattern. I was worried about the playa dust getting into the engine but found it's no problem. The dust is so fine and non-abrasive that it just doesn't bother engines but can clog filters. It wouldn't even scratch the canopy which I had to clean every flight. It will remove any oil and leave metal open for corrosion.

The dust clouds are really impressive and all vis can just go away in a moment but you can see it coming. One no-no is to jump in front of someone on a long final and take off as you leave a big cloud of dust that completely obscures the runway and makes you go around. I saw several pilots do it and one did it to me. I tapped his wing tip as I was passing him just to let him know he was a douche.

At the very end, two days after BM ended, the FAA sanctioned airport shut down and all the playa was an "airport" again. When I went to leave it was almost just me and the desert left so after my preflight, I just picked up the tail, turned her into the wind, got in, fired her up, looked around, and took off from a standing start. There was a good wind blowing and with no passenger the plane took off before I did.

The weather was perfect for flying back to the Bay Area with a stop at Truckee just for fun. I tried to clean the dust off my feet in the bathroom at Truckee but instead left muddy foot prints all over their polished floor. So sorry.

Other that our son getting hurt the whole thing was a dream come true. The Q2 is still an incredible airplane even after 28 years. The other day, flying low in cool air over the bay, at 3500 rpm I was indicating 184 mph. She still has it in her to give people the ride of their lives!

Our Son after two operations to pin the bones is his face and wrist back together and broken jaw wired shut made it back to Burning Man just before the last weekend to the cheers of all his friends. The picture above is of him standing next to the plane.

Q-talk 156 - Quick-Release Canopy

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Category: Q-Talk Articles

Published: Wednesday, 19 December 2012 14:45

Written by Harold Dirks

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by Harold Dirks
Quickie 2 - N32DK

This article is a brief discussion of what we did to construct and install the quick-release canopy on our Q2. Our plane has a front-opening canopy like many other Q’s. Most of these canopies use gas struts, but ours has aluminum-tube struts that easily disconnect from the canopy. The first picture below shows the struts in place. Each strut starts out as a long tube that is cut in half to make a top and a bottom piece. The strut tube bottom halves are reinforced with a short piece of aluminum rod inserted into one end. These ends have a slot cut into them to fit over the vertical part of aluminum angles that have their horizontal part bolted to the plane’s longerons. The strut bottoms and the vertical parts of the angles are drilled for a bolt which serves as a pivot to allow the bottom half of the struts to move backward. The bottoms of the struts do not quick-release.

Canopy Struts

The next 2 pictures show the home-made hinge/lock that allows the struts to fold in the center and lock when they are vertical. The lock portion consists of a spring with a moveable collar underneath. To open the lock, you push the collar up against the spring until the extended portion of the lower tube is free of the collar, and then pull back on the lower tube and release the collar. This is easily done with one hand. Once one side is unlocked, you use your other hand to unlock the other strut while holding the canopy up with your first hand. You can then use one or both hands to lower the canopy. The folded struts then lie out of the way alongside the longerons. To open the canopy, you reverse the procedure and again push the locking collar against the spring until you can lower it over the extended portion of the lower tube to lock the strut. A close examination of the lock reveals that it is made out of 2 lengths of larger diameter aluminum tubing that are a slip fit on the strut tubes. The collars are an even larger diameter tube that slip-fits the lock tubing.

Hinge Locked

Hinge Unlocked

The hinge is made up from six small pieces of aluminum plate. 3 pieces are L-shaped and the other 3 are rectangular. The bottom portion of the hinge is made of 1 rectangular piece and 2 L-shaped pieces that are sandwiched together with the rectangular piece in the middle. The sandwich is filed round on its outside edges to fit down inside of the bottom strut tube. The bolt shown below the hinge holds the bottom hinge part and the bottom lock tube part in place. The top hinge portion is another sandwich with the L-shaped piece in the middle. It is filed to fit up into the top tube and is held in place with the bolt shown below the movable collar. This bolt also serves as the lower stop for the collar.

The canopy struts attach to the canopy sides with special ball-head bolts that we obtained from a local farm store. These special bolts are used in many applications. The ones we used are originally installed on tractor carburetors as a throttle connection and are usually available as spare parts. The top strut connection to the canopy is shown in the next two pictures. In the first picture the strut is shown attached to the side of the canopy. In the second picture, the strut is detached and the ball-head bolt is visible. The ball-head bolt has threads on its other end, which allows the use of a washer and lock nut to fasten the bolt to the vertical portion of the aluminum angle whose horizontal portion is bolted to the canopy frame. This aluminum angle is similar to the ones used to attach the bottoms of the struts to the fuselage longerons.

The top of the strut uses a piece of aluminum rod that fits into the strut tube and is held by the bolt shown. The rod accepts the ball via a hole drilled part-way through (hidden in this picture). When the ball is inserted in the hole, it is held in place by the spring-loaded steel collar. A hole is drilled in the collar to fit the neck behind the ball and the hole is cut and filed to provide a U-shaped slot that extends to the top of the collar. The spring provides upward force on the collar to keep the ball securely in place. A cotter key placed at the top of the rod stops upward movement of the collar. To release the ball, you pull the collar down below the ball and then pull the strut away from the ball. The struts can be released from the balls at any time.

Strut Attached

Strut Detached

In addition to the quick-release struts, the canopy itself can be released from its mounting hinges. This is accomplished with the mechanism shown in the next two pictures. The first picture shows the release handle next to the compass box at the front of the canopy shroud. This aluminum tube handle pulls the small cable that operates the hinge release cam shown below the big word “EXPERIMENTAL.” The handle is easily accessible when the canopy is closed.

Canopy Release 1

The second picture shows a closer view of the release cable, cam, spring, and shaft. When the cable is pulled, the left end of the cam goes up, causing the shaft to move to the right, which retracts the hinge pins out of the hinge attachments and allows the aluminum hinge bars to fall down and free the canopy. The hinge bar attachments were milled out of solid aluminum blocks and the shaft is made from steel tubes and pins.

Canopy Release 2

The cam revolves around a lobe bolt that is barely shown under the shaft. The other bolt shown at the top part of the cam lobe provides an attachment for the right end of the spring. The spring provides tension to prevent any vibration from moving the cam. This spring also provides tension on the cable to keep the release handle firmly in its place at the front of the canopy shroud. We have used this release mechanism many times to remove the canopy for maintenance, but we have never used it in an emergency.

For normal use when the canopy is closed, a lever is located on the inside rear of each canopy side as shown in the next two pictures. The head of the screw for the knob is inserted into the hole on the tab to lock the canopy closed. The lever is shown open and closed in the pictures. Each lever is attached to the canopy frame with another handy aluminum angle like the ones used at the top and bottom of the struts. The head of the screw for the knob is inserted into the hole on the tab to lock the canopy closed. The lever is shown open and closed in the pictures. Each lever is attached to the canopy frame with another handy aluminum angle like the ones used at the top and bottom of the struts. These levers are easy to operate and can be quickly opened and closed.

Canopy Lock Lever Open

Canopy Lock Lever Closed