Apr 28, 2021     A couple of discoveries. - (49.0 hours)       Category: Landing Gear

Was finishing up sticking tabs to the fuselage when I needed a bunch added to the firewall structure. So, removed the rotisserie and placed the fuselage on the landing gear (as a plus, it looks more like progress that way too). After finishing welding the added tabs to the firewall area, figured I could re-install the rudder pedals and cables and get in to ensure I get the heel brake levers "clocked" correctly on their shafts before drilling for AN-3 bolts. Since I had already welded the shafts to the torque arm that connects to the master cylinders, this meant I would have to drill the aluminum pedals to the chro-moly steel shafts to complete this. Given their location, doing it in place accurately was going to be a problem. Left them to sit a few weeks while monkeying with other bits, hoping for inspiration to strike in the form of a clever solution to drilling these. Best suggestion I received was a simple and elegant solution IF I hadn't already welded the arms to the shafts: Simply drill the pedals to the shafts in the drill press first, THEN install and clock everything, and only then tack the arms to the shafts in place. Brilliant! Except this would now involve a lot of backing up... cutting the arms off the shafts, fabbing new arms or cleaning up the cut off ones, putting the fuse back in the rotisserie etc, etc. I'm slow enough as it is and getting older by the minute. Who's got time for that? Finally admitted to myself building a drill jig wouldn't be that much trouble and would get me the accurately-located hole(s) I was looking for. Worked like a champ! Pedals clocked just slightly forward allows simultaneous full rudder deflection and still get my size 12 planted on the pedal face.
The other rude surprise that was also some time in the making involved the brake calipers, or more correctly their torque plates. Completed the landing gear construction last year to the letter of Drawing 17 unfortunately. Found an error in the plans I was unaware of until this week. Possibly, I missed my distance-learning homework assignment and others already knew about this and have included it in the known-about list of problems with the plans,,, I don't recall having seen anything about it. Goes like this: Big note at the bottom of Dwg. 17 states "Rotate brake mounting flange 7 degrees to allow clearance when aircraft is sitting on tailwheel". It also shows a caliper located aft of the strut angled up from the horizontal by about 7 degrees. I am here to tell you that won't work. A horizontal caliper or even slightly angled down one will. The drawing even shows the interference I discovered, the top corner of the caliper interferes with the aft gear leg strut. Since I wasn't going to cut the mounting flange off the axle or re-drill it in place (it's 1/8" steel), my solution was to re-locate the calipers to the forward side of the axles. This is exactly where my Cessna 180 and my neighbors Cessna 140 calipers are located. Probably ok.
Takeaway lesson: Build it to fit regardless what the plans have to say about something. (Trust but Verify)
A follow-up to the caliper-gear leg interference issue: I saw a photo somewhere on the interwebs of a (Hatz?) caliper bolted to the brake torque flange with spacer bushings about 1/2" long. News flash! This would solve the interference problem and shorten the length of axle on the outboard side of the wheels. A similar length 1-1/2" ID bushing slipped over the axle tube inboard of the wheel would allow the inboard wheel bearings to ride against that bushing instead of the telescoped tube the axles are welded into. Bottom line: The bushings move the whole mess, brake calipers, wheel bearings etc. outboard about 1/2" providing clearance with the aft gear leg and less excess axle stub on the outboard side of the wheels.

  Sep 25, 2020     Brakes - (9.0 hours)       Category: Landing Gear

Been working on brake bits for awhile. Got around to starting the fabrication of the master cylinders mount block. It's 3/4" square tube with 5/16" X 0.063" inserts to accept 3/16" bolts. It welds to the lower crosstube below the floor, behind the passenger seat. Didn't have the proper 5/16" tube on hand so called a temporary halt to the operation. I have fabbed and installed the brake torque plates to the axles after I completed main gear assembly on 4/22/2020. Turned these on Dan's lathe and drilled holes to match the Grove brake calipers which bolt to them (these are pretty much a match for Cleveland brakes). Also turned and faced tubes to accept bronze bushings for the heel brake pedal shafts. Still need to install. The heel brake pedals themselves are now on hand (used) and will need a cleanup prior to install. Tried to purchase new manufacture pedals but could only find right ones... Left side is apparently out of production? Hello, Ebay. These pedals, as manufactured, have a bronze insert which needs to be driven out in order to fit the shaft size in the plans. Also the ear opposite the pedal needs to be cut off as well. The reservoir and associated plumbing is also on hand awaiting install. Planning to run the plastic (Nylaflow) brake lines all the way down the gear legs to the brake calipers. Not on the plans, but photos show short, curved steel tube lengths attached to the main gear legs at the top and bottom through which the nylon brake lines are threaded... seems like a good idea. A tab and an adel clamp would likely serve as well. Some have questioned running plastic lines to the calipers as brakes get hot and so do the calipers inviting a brake line failure. On the Hatz, a dragging brake MAY create such a problem, but I think the resultant control pressures/requirements from a dragging brake would be cause for investigation and limiting operation until solved. I have been told the heel brakes are used primarily for holding the Hatz in position during preflight runups and for stopping the aircraft at its parking location. The only plastic brake line brake failure incident I'm aware of was in a Varieze or Longeze. These aircraft have much higher landing speeds, smaller wheels, generally tightly cowled wheel pants and no provision for mechanically connected steering on the ground other than differential braking. Big difference, I'm willing to risk it.

  Mar 15, 2020     Main Gear - (78.0 hours)       Category: Landing Gear

Began the main gear construction by fabricating the spring struts. These struts are under tension loads when weight is on the wheels (even more depending how firm the landing may be), but the springs themselves are under compression loads due to the design of the strut. The long end (bottom) telescopes into the upper shorter end. The longer bottom end pins to a welded washer and bushing that sits on the top of the spring and is allowed to slide on the slotted upper tube. The bottom end of the spring has an identical welded washer and bushing fixed to the upper tube and the lower tube is slotted there to allow the telescoping action. This telescoping action then loads the spring in compression when sitting on the gear. First picture shows a spring compression tool I built to assemble the struts. The springs are pre-loaded in the struts and require this to assemble. Strut ends have welded bushings and finger straps formed and welded over them to increase their tensile strength.
First order of business was to invert the fuselage on the bench and install the hard points for the fore and aft gear attach pivots. Started with the aft point which also serves as a location for the lower wing forward spar attach. Located the forward spar attach bushing and tacked it in place using a short tab welded to the longeron. More welded bits boxed it in and a finger gusset was wrapped around from top to bottom, formed to the adjacent crosstube and welded fast. Once the wrapper gusset was finish welded in place, 1/8" U-brackets were fabbed and tacked in place atop the gusset. These brackets are the aft main gear leg pivot points and so required aligning with the longeron and forward gear attach fittings yet to be installed. A 5/16" steel rod was used for the alignment process. Once the aft leg U-brackets were tacked and welded in place, the forward leg attach plates were prepped for install. Forward attach plates were spaced apart using short lengths of steel tube bolted between them. The contact points with the longerons were coped out to allow proper dimensioning of the predrilled attach bolt holes off the longerons and in alignment with the aft mounts. Also alignment with the opposite fitting across the fuselage was required. The inboard edges of these plates weld to the adjacent 7/8" crosstube, but they are spaced 1-1/8" apart, hence the lip bent in the edge of the plates to contact the crosstube for welding. Once these hardpoints were completely welded, the lower cabane V was next. Stood some scrap MDF in the forward leg weldments to locate bolt holes, then used this board as a jig to dimension and fit up the cabane. Finish-welded the lower cabane V in situ on the airframe and stress-relieved same to prevent and correct any warping or movement in the process. Once the cabane V was complete, re-inverted the fuse and installed the spring struts. Used angle iron bolted to the framework to position and hold the components in place. Welded and drilled axles were added and a pair of angle iron were drilled and pinned to the axles clamping them with the specified camber and zero toe-in. These angles were also leveled, the hardware clamping everything in place. The forward gear legs were up first. After fabricating the upper leg pivot it was made to fit the forward fuselage gear fitting. In order to fit the leg to the axle, I downloaded a coping template from metalgeek.com . This process simplified the leg fitup a lot minimizing the back-and-forth fitting prior to tacking the leg in place. The aft legs were similarly started at the pivot point to match the aft leg fitting on the fuselage. Another coping template allowed fitting the aft leg to the forward prior to tacking and welding. Upper gear leg 1/2" crosstubes were fitted to the gear legs prior to finish-welding the remainder of the legs. This helped minimize any distortion drawing the pivot points together and provides structure for later fabric covering. Lastly, two gear leg ribs were added each side, brake torque plates welded in place and axle to leg gussets were added. Fuse was righted and placed on wheels.

  Jan 24, 2020     Tailspring mount - (9.3 hours)       Category: Landing Gear

Welded 1-1/2X3/4" rect tube in place between the lower longerons per plans to hold 3/8" bolt through the forward end of the tailspring. Tailspring is replacement unit for a 7AC acft. Acft Spruce & S p/n is 06-14400. I think its a Univair part since it has their stuff on it too U3-428-3; FAA PMA: 7AC, 11AC, 7EC, 7ECA, 7GCAA, 7GCBC. 3/8 " ID bushing is welded in the center to accept aforesaid bolt. Tabs added are the mount locations for the lower horizontal stab brace wires. Bend angle was derived from measuring the scaled plans. Material was also not specified, but I used 0.090" 4130 steel plate. Decided on this after reviewing the drawings for the EAA Acrosport, WagAero Sport Cub, Steen Skybolt and Starduster plans all of which use similar tabs.
The tailpost bottom fitting and tailspring clamp similarly fails to note materials. Again, used 0.090" plate to fabricate. The clamp internal dimension is specified as 1-5/8" (or, 1.625") but the tailspring utilized is 1-1/2" wide... Slop is not something desired in this fitting. Not sure why that dimension is specified, but using a layer of rubberized baffle material scrap around the spring where the clamp meets it forms a snug fit.
Update: Quizzed my neighborly A&P/IA Chris Bobka about the fitment issues... he didn't like it. Instructed me to weld in 0.063" thick shims on both sides of the U-bracket, narrowing the gap to 1-1/2" to match the spring width. Now any lateral loads from the spring will be transferred steel on steel. Further advised to sandwich a 1/4" rubber block between the bottom of the tailpost and the top of the spring at the aft mount. Another 1/4" rubber pad was added at the forward mount similar to a Cessna 140/170 tailspring mount. The forward pad is retained by a 0.050" steel U-bracket and is compressed by landing loads on the tailwheel. The last two photos show the individual components and the assembled spring and mount.