Our household aircraft fleet is focused on low-wing airplanes—a handful of RVs, the tiny little jet, and the eXenos motorglider—all of which can be jacked or lifted with simple, short jacks. We have wing-point jacks for the RVs built from Harbor Freight hydraulic cylinders, which also work on the eXenos (though that’s just as easy to lift with an engine hoist on the motor mount), and the little jet is lifted with a single motorcycle jack under the middle of the belly.
But our oddball aircraft is the high-wing Tundra—a big metal bush plane (think “homebuilt C-170”) that has no jack points on the landing gear or wings. Even if it did have wing hard points, I wouldn’t want to invest in—much less store—the big jacks needed for a high-wing airplane. The Tundra was designed as a floatplane and has lifting points on top of the wing and fuselage so it can be hoisted for float changes, but we don’t have a large H-frame crane for that, and we’re not about to get one.
The landing gear on the Tundra is a beautiful set of legs built by Grove (along with their wheels and brakes). The gear legs are gun-drilled for the brake lines, with the exit fitting on the bottom—making it impossible to catch the leg with a jack without crushing the hydraulic line. The axles bolt to the side of the lower vertical face of the gear leg with two AN5 and two AN6 bolts—none of which alone offer purchase for a jack. In the past, we’ve lifted the airplane by wrapping a cargo strap around the gear leg and lifting with the engine hoist, letting friction between the strap and the gear leg do the work—but this always left me a little queasy about leaving it that way for long.
What we needed was a jack point that stuck out on the inboard side of the gear leg far enough to pick up with a floor jack. This would greatly simplify working on brakes or swapping between normal tires and the balloon set we use for off-airport adventures. What I came up with was a ¾-inch steel shaft welded to a flat plate that mounts to the inboard face of the gear leg and uses the four axle-attach bolts to carry the load. Essentially, the axle and jack point sandwich the gear leg, and from a design perspective, the jack point is nothing more than a thick set of washers on the axle attach bolts (with longer bolts, of course). Rather than carrying around excess steel in flight, I figured a ¾-inch ID extension tube could be slipped on when jacking is required to give a more secure purchase for the jack.
With the design conceived, it was time to head to the shop for some fabrication!
Detailed Design
The jack points are simple—a plate with a short shaft welded on. But how big should it be? To find out, we measured the area without crawling around on the cold hangar floor. Holding a metal rule by the bolts, we snapped a picture. On the drawing desk, we determined the bolt spacing to the nearest 1/64 inch and confirmed they were in a rectangular pattern. Because the gear legs are tapered, we decided to make the plates slightly oversized and shape them to final dimensions during installation.
Material choice was easy—I had a piece of ¾-inch ID 4130 tubing for the extension, so the shaft was set at 3/4 inch. Yes, it was TLAR (“That Looks About Right”) engineering—and in retrospect, grossly overdesigned. But when lifting something as big as the Tundra, bigger feels better. Plus, larger makes it easier to work with and harder to misplace the extension tube. The plates were 3/16-inch steel—thick enough to accommodate my still-developing welding skills. I didn’t have 3/4-inch steel shaft stock, but ¾-inch grade 8 bolts were readily available, so I bought a few 5-inch bolts as raw stock and got started.
When modifying anything structural, the key question is: Can this lead to something bad happening? For this design, I was cautious about altering the axle attachment points. The bolts remain the same diameter as the originals, the axle still contacts the gear leg directly, and since the new part acts as a thick washer, the load paths are unchanged—so long as there’s adequate thread engagement with longer bolts.
The other “what-if” scenario was failure during lifting. If the jack point broke under load, the airplane would simply settle onto its wheels. If it bent, it would be visible before failure. The only real risk was if the jack point failed suddenly with a wheel removed—but that’s why we always put a jack stand under the axle when working. The risk was low and isolated to shop work—not flight—so it was time to fabricate.
Machining and Welding
I’m still learning machining and welding—skills I came to later in life. This project started as practice, with a useful product as the bonus.
The shaft began as a 3/4-inch bolt. I chucked it in the lathe and machined off the hex head, leaving a 1-inch disk roughly 3/32-inch thick, and cut the threaded end off, leaving a 3-inch cylinder. A ¼-inch hole was drilled in one end to save a little weight, though the final pair weighed less than a pound, so it hardly mattered.
The 3/16-inch steel plates were cut to 3×2½-inch blanks on a chop saw. The centers were marked and pilot-drilled, then carefully centered in a four-jaw chuck. The hole was enlarged to 3/4 inch for a snug, no-play fit with the shaft, and counterbored 1 inch in diameter and 3/32 inch deep so the flange would sit flush.
Final shaping would wait until the assemblies were fit to the gear legs.
Welding took the most trial and error—I made six total before getting two perfect. The first attempt warped the shaft from heat. The second improved, but still tilted slightly. The third time, I clamped the parts flat on the table with aluminum-foil shim stock to keep everything square. I tack-welded, then ran full welds front and back. When I spun the assembly in the lathe, the plate ran dead true. After a cleanup pass to flatten the weld bead, I had two good parts.
Assembly and Testing
Before hoisting the airplane, I predrilled the four mounting holes, measuring carefully using the same photo method. After drilling one unit, I clamped the other to it and drilled through so both matched exactly.
We hoisted the Tundra as before, removed the wheels, and test-fitted the jack point—perfect fit. After tracing the gear leg outline onto the plate, we milled the plate to match, dressed the edges, and reinstalled it with bolts 1/4 inch longer than stock. Everything bolted up cleanly. We repeated the process on the other side.
For the final test, I slipped a 6-inch piece of 4130 tubing over the jack point, positioned a 1 1/2-ton floor jack, and pumped. The wheel lifted smoothly, nothing groaned or flexed, and the setup felt solid. Success in all categories.
Projects like this build both skills and confidence. The Tundra now has a safe, easy way to swap between runway tires and bush wheels—and I gained more welding and machining experience, plus a few imperfect parts for future practice.
Great article and good idea.
THIS is great content! Please keep articles like this coming.
Nice project and article. My C172A stands fairly high on its spring-steel gear. There is a jackpoint on the underside of each cabin-entry step on the gear legs. Since the step mount has a fixed width, it physically cannot slide up the tapered gear leg past the appropriate point. That always seemed to me to be a clever design, in that it moved the jackpoints inboard, and meant the jack would never get in way of any work being done on the wheels.
A side note. I have the exact same floor jack- it must be 50 years old!
Paul,
Nice trick measuring the distance between the holes with a rule and your cellphone camera. Here’s another one that may come in handy for those with digital calipers. Measure the bolt (or hole), zero the caliper, measure to the outside of the bolts (or holes); the displayed reading will be the center to center distance.
Cheers, David