Paul Lee - SQ2000 Project, Pierre SD USA

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The main part of the landing gear finally arrived (11/23/01).

Showing one of the landing gears. There is an interesting story about the wheel wells that I got back in August from KLS. I contacted Stan (KLS manager and designer) asking why the wheel wells are 17" dia and the wheels are only 13" - it takes up more fuel space and asked how I could reduce it. He indicated that it was to tire manufacturer varying wheel size diameters and builder slopines. Then I havent heard from him on that. But last Monday (11-26-01) a parcel arrived at the post office with two more wheel wells of reduced diameter (14.5"). Both wheel wells are shown here indicating the size reduction. That was nice of KLS - showing they are trying to please. If the smaller wheel wells work out it would mean about 5 gallons extra fuel.
Attempting to compress the RG strut.
Trunion plate hole(s) are cutout (showing left side). The small hole is for portrusion of a nut behind plate.
Showing the LH strut clamped in position. By hand rotation I found that the RH strut scissor mechanism was binding. The trunion pin angle was too large (7 degrees instead of designed 5.5). After a few emails, the factory promptly sent two new trunion plates. I used only the RH one since the old LH worked OK with some washer adjustments.
Now lets see.... Instructions: level fuselage and level landing gear strut until it is perfectly vertical. But how do you make it vertical if it has a deliberate 8 degree forward angle? Guess it meant that it should be vertical in a forward vertical plane. You cannot simply put a level to the strut since it is slanted and leveling it in the forward plane would be a function how well you place the level to the strut - which is difficult. But wait... the vertical plane should be same distance from front of fuselage as from spar center. So using a verticall level from front you should be able to line up the strut to be vertical. A couple of bolt holes were drilled through the strut to hold strut in position for flox application (see next paragraph).
But before strut leveling above is done, the strut plates were tilted so that both struts were approximately in the same plane and the gap behind plates is later filled with flox. The flox is necessary since the vertical angles of the trunion pins are not perfectly the same vertical angle AND the forward strut surface is not perfectly flat with the plate. Simply bolting the plates to the strut will introduce unequal streses on both plate and strut. The flox is prevented from binding to the plates with some clear plastic packing tape on back of plates. As seen in second shot below after floxing, curing and removal of the plate, the flox forms a perfect mating surface to the trunion plate so there are no uneqal streses due to bolting.
The brake caliper bolt mount did not fit off the fork sufficiently so that a small notch had to be sanded in the fork to free the sliding motion of the brake caliper.
The factory instructions were a bit vague about wheel toe-in lineup. I clamped a straight edge on each fork (after mounting the wheels otherwise would be harder to hold the fork in position while drilling). A chalk line was made on the garage floor below the center line of the fuselage (use plumb bob). And two more parallel (equidistant) lines were made on the floor near the wheels so that I could sight the parallax of the straight edge and the floor lines to line up the wheels. The center line below fuselage and the parallel line near right wheel are shown in the photo drawn with MS paint.

Irregardless of my efforts I could not compress the struts as instructed. So I simply moved the sleeve guide up a screw hole hoping that the weight of the plane will eventually compress the spring and then I can move the sleeve guides back to original position.

OK. Got the things compressed (04/04/02). It took the plane weight and the force of about 3 tiedown straps to force sufficient movement for the screws to be where they should be.
A good idea is to tape the screw slider opening with some clear plastic tape to prevent dust entering during construction. Hmmm... What prevents dust/dirt entry during normal operation? Will have to look into that.

This part has to be done before strakes are closed in. The hydraulic and brake hose connections needed mounting connection blocks. A simple loose hose/line connection would chafe and likely fail. The hydraulic connector block (left) I made out of 1x1 square solid aluminum bar with two parallel horizontal holes drilled one above the other, top NPT 1/8 holes drilled and then using alen set screws proper holes were blocked to form two U shaped conduction channels. Two vertical holes - not interfering with the channels - were drilled to bolt the block to the strake. (But see 07-01-02 update on block replacement below due to leakage.) The brake connection block was made out of a simple pipe welded to a mounting plate to hold in place. It is important to orient the flex hoses so that they are only in coiling motion and not torsion - else they may losen up or fail. When gear is down, the hydraulic hoses should be the shortest length necessary - while the shortest length for the brake hose is when gear is up.

The spring connected to the LS of cylinder and the RS mounting bolt is my effort to design emergency gear release. Plan to install a hydraulic bypass valve if the electric hydralic pump fails, so that gravity and the spring (which helps to snap the gear into lock position) will help to lower the gear. Another spring will be installed in the nose gear - something else may have to be done too since the NG lowering is against the airstream.

04/23/2004 Post build note:, after FAA inspection. I played around with the RG and still found the retraction unsatisfactory. It would not retract with correct force to hold the gear accurately in up position. The actuator stroke and overall length were too long and the actuator force and the weight of the RG are "fighting against each other". The photo on left shows an extra stop block I placed to prevent the back of actuator from moving further in the up position against the brace top pivot. In the up position this results in 0 forces on the brace and the only actuator force holding the gear up, is on the rod end bearing on top of the trunion shaft (right). Without it there are very high forces on all brace pivot parts and the rod end bearing - and the weight of the gear is pushing down on the brace while the back end of the actuator is pushing on top end of the brace.

12/23/2004 Post build note: You may have noticed that the actuator on the left is different from original above. I have replaced all 3 brass "Cylinders & Valves" actuators - two main ones supplied with kit - with steel body actuators from Custom Actuators. The steel ones have a 5000 psi working pressure while the brass ones are 1500psi. Because of that I cranked up the hydraulic force to 1500 psi and reduced the main RG actuators from 1.5" to 1.25" bore. I also saved about 4 lbs weight since the steel actuators are lighter. All this actuator experimenting, and finally getting it right, cost me an extra $800.

11/30/04 Post build note: After one hard landing(s) I noticed cracks on the trunion plate bushing welds - both left and right. I had them re-welded AND welded the aft side of the plate too. The original weld is quite a small bead and only one side. If you get the RG from SQ2000 factory, it might be a good idea to weld a small bead (take it to a good welding shop unless you are a pro) on the back side and then put an extra heavy bead on top of the front bead already there. For the back part you will have to bevel the spar hole front where the trunion bushing goes through to accommodate the new bead. Not sure if this is a problem with Infinity Aerospace units as well.

You can see the re-welded job in the post build photo above.

07/24/06 Post build note: After my April 2006 gear failure accident I redesigned and reinforced the upper brace pins and also replaced the slightly bent main trunion pins with 7075T651 high strength aluminum alloy. The left photo shows the revised design with the machined pin replaced with a through bolt and an extra bracket around the arm to the bolt. The lower right inset shows the original pin and the broken one. It is a simple machined unit with a nut and washer but failed in shear. The right photo shows the picture from top on left showing the main trunion new through bolt position. This allows me to simply replace the bolt with new ones periodically - say every 100 hours.
Showing the brake line connection block with hose and line connected. The aluminum line to the brake caliper is curved to permit some elastic yield (Hooke's law) since the caliper is not totally rigid wrt the axle.
(05/03/2009) Postbuild Note: I have revised the RG strut connection to the wheel fork. You can see above that the strut tube is connected to the fork with a single through bolt.

I changed the connection to a slightly adjustable toe settings by enlaring the strut tube bolt hole to oval shape. That way the bolt can be horizontally moved in the oval hole and adjust the toe. I have further added a custom made clamp (welded from 1" high 4130 steel tubing piece) as shown. That eliminates the potential wiggle slop in the strut-tubing/fork-connection with the bolt. Notice the required vertical 1 1/2" slit (front and back) in lower part of the tubing in order to allow the clamp compression. Click photo on left for closer view.

A slight toe out is recommended to eliminate gear slop/vibration on ground and emergency gear lowering for touchdown. The 04/13/06 landing gear failure reminded me of touchdown instability with loose landing gear brace. The gear/tires appear to hop around. I detected the instability again one time in 2008 when I did not extend the landing gear 100%. After the gear falure in 2006, I have aligned the gear with a slight toe out. It helps: 1. to keep the braces tight and rigid in case the gear is loosely lowered or the gear droped down without hydraulic pressure in emergency. 2. to keep the tires vertical by counteracting the load bending of the fork and minimize the tendency of the tire to scrape on the fork due to small clearance between tire top and fork.

And getting carried away with aluminum connection blocks.... The Matco brake fluid reservoir comes with a mounting bracket attached to the filler cap and the outlet is on bottom. That means you would have to disassemble the thing to put brake fluid in. Instead I mounted the thing on top of a aluminum connection block I made from 5/8 square aluminum tubing and welded a mounting bracket to it, so that the filler cap can now be used in normal fashion.

If you are working on your project, I could possibly make aluminum connection block(s) for you for a nominal cost. The mini lathe and the mig welder come in handy for shaping/welding aluminum.

Another thing to install before closing in the upper strake. The up/down microswitches are shown on galvanized sheet metal bracket fabricated. I choose galvanized steel since it can be adjusted and can stand a lot more distortion before breaking - unlike aluminum which breaks after a few bends. The lower part of photo shows switch assembly in place. The down switch is activated by end of cylinder while the up switch is activated by the clamp butt shown when gear retracts. The wiring to switches is not connected yet.
07-01-02 LS RG update: After hooking up RG retract circuit and connecting to inside switch and starting up the pump, the aluminum hydraulic distribution block on RG LS was leaking at the set screws. I replaced the block with another I then made, but it still leaked around the large set screw. Apparently the pressure caused the hole around the set screw to distort. A larger chunk of aluminum might have done the job but i decided to replace the assembly with brass/steel plumbing pieces which I will encase in glass/flox to similar block shape to fasten same way as the aluminum block.
I just could not see that much advanatage of retracts if there are big gaping holes on the underside of strakes. After spending eons figuring different ways, I finally settled on a two piece combination that leaves only three small gaps - one near bottom of wheel, another in middle which is required so that the wheel can move up and down and the third near the pivot (seen when the wheels are retracted). A total cover design would probably add 200 hours to construction and a lot of expense. The two pieces were made from the cutouts left over from wheel well installation. The lower one is held by the four wheel bolts through a aluminum plate that is glassed in the center and another reinforcement connected to the lower strut bolt. The upper one is held in place by two small T shaped brackets I welded to the strut. This is where the MIG welder comes in handy since it can be used as a surface welder not distorting the structure.
This is not a key. It is the RS cutout from wheel well hole which I use to make the wheel cover for the retractible. The right side is comming faster than left side - guess I know more what to do now.
The hydraulic pump performed slugishly on the rg lowering stroke. Apparently a bit of loose hydraulic hose rubber got into the lines and got mashed by the pump. Took it appart and clean it and purged the hydraulic lines. That still didnt do the trick and had it returned to the pump manufacturer for repairs.
Emergency gear lowering: The factory model has an emergency "blow down" system which I haven't been able to get hold of. The photo shows two pressure release valves (up/down) that permit the retracts to simply fall down by gravity when hydraulic pressure is released. The main gear do not seem to be a problem and the attached wheel covers are actually slanted slightly outward to help the wheels separate under aerodynamic pressure. But the front gear lowering is against the air stream and would not likely come all the way down by itself. After mulling the problem over for long time I've come up with a pulley/cable/lever system that forces the front NG to come down the rest of the way into locking position. The 4.5" flat idler pulley (from a farm supply place) does not rotate with main NG pivot bracket except when the cable is pulled and then the welded tooth pushes against the pivot bracket and rotates it down. A spring tends to hold the pulley in the retract position. The cable winch inside cabin is made up of the cable going through a 5/16 OD steel greased tube from the FS-37 bulkhead to a tie down strap ratchet mechanism (Wall-Mart) underneath the dashboard on passenger side. The whole system is about 30 bucks plus some welding skills.

If there are jobs I dislike, messy hydraulics has got to be on top of the list.

A late note: In the photo you can see the hydraulics sticking up out after the strake was installed. I decided that it would be too hard to service the RG stuff just from below and cutout a cover shape on top (and a small one in front of the RG pivot). Both pieces are held down by screws. I made servicing a priority.

Post build notes:
(9/14/04) Do I recommend retracts? A number of SQ2000 builders opted for fixed landing gear rather than retracts. Some other opinions are either all pro's or all con's. Here are the pros and cons I can see.

1. More landing stability. The retracts are over 11 ft apart compared to about 6.5 ft fixed gear.
2. The retracts are an effective air brake when extended.
3. Better looks in flight and on ground.
4. Possibly less air resistance than fixed gear.

1. More building time.
2. More expensive.
3. Less fuel capacity.
4. More maintenance.

(9/16/05) So far I had to replace 3 springs after a couple of hard landings. One problem is the spring alloy 3" elastic motion limitation (without deformation). But the spring travel allowed by the gear is about 4.25" plus the 1.25" pre-compression required to hold the plane empty. The springs are not difficult to replace or procure - several manufacturers can make them. Stan Montgomery gave me two replacement springs free but the new ones I ordered made of chrome-silicone alloy may last longer. Alternative titanium springs have an elastic working limit of 4.8" but fairly expensive at $600 each and still do not allow for the full 5.5" compression.

AFAIK Infinity Aerospace uses total gas oleo struts which will regulate landing shock better but I suspect may need more gas charge maintenance than spring loaded oleo struts.

(10/04/05) Added extra guide tubing around springs to help retain cylindrical shape when compressed and installed more firmer shocks (Gabriel G63798) with a unique valve system that dampens sudden gear motion on impact.

(06/29/06) Update: It seems that the new chrome-silicon alloy springs and possibly the heavier shocks have prevented further spring sagging. Although I had a RG landing failure 04/13/06, the springs showed no signs of sagging. The new springs were purchased from Associated Spring Raymond (part No.: C200-0406-1400-01A). I recommend their service.

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