"Other than music wire [1/8"] what material and hardware is used to make " sheet metal" landing gears? I am seeing gear bolted to both sides of a fuse, but if its soft enough to bend to shape, do you heat treat / temper aluminum to keep that shape? And axles are RC type axles? Much appreciated"
A few comments: You can use aluminum or titanium sheet gear, depending on what the gear is going on, and what you are trying to do. I have used both. You asked about aluminum, so let's skip ti.
For aluminum, you want an alloy with pretty high temper, meaning it will take a lot of stress before yielding. 2024 alloy with a T4 temper is excellent as it is a bit easier to bend than T3. A 6061-T6 is good. 7075-T6 is the strongest, but now we are talking about a material that is (much) harder to get, and much harder to bend. I would avoid anything other than these for landing gear.
The K&S website states that their .090 and .125 sheet is 6061-T6. You shouldn't need .125 for a stunt gear unless you are trying to make it very narrow....in which case why not use 1085 steel (ie. music wire).
If you try heating the aluminum material with a torch or other source that is hot enough to make it easier to bend, know that you are not going to get back all of the strength properties when it returns to room temperature. Therefore this technique should be avoided. I don't see how an average guy working in his garage is going to precipitation harden and solution treat aluminum, so.... Some aluminum alloys are not heat treatable, so the strength is increased by work hardening. If you take the torch to it, the grain size grows, the matrix distortion relaxes and the strength goes away. I suppose to could try to get it back by hitting it with a hammer--but then you have a landing gear that looks exactly like you hit it with a hammer....
You have a tradeoff when keeping the weight constant between increasing the thickness of the gear which is far more effective per ounce at stiffening it up, or increasing the width of the gear leg which lets it flex more. This also affects how difficult it is to bend during fabrication (and bend unintentionally when the landing isn't so great.) If you have access to a bending brake, then all you need to know is what the setback adjustment for the brake should be to provide the required bend radius. Each alloy, temper and thickness has a minimum safe bend radius that avoids overstress and cracking. for your material of choice, google up a bend radius chart for the exact material you are using. If you are bending to minimums, be sure to clean up the edges of the leg before bending to reduce the chances of a rough edge initiating a crack. Polish it if you are going to polish the gear anyway for a final finish. Also, you can orient the blank so that the bend line is 90 degrees from the rolled direction of the sheet. You can tell the rolled direction most easily by looking at the ink mill marks. They run the length of the sheet. 2024 alloy uses blue ink, and 6061 alloy uses red ink.
Don't use a scriber on aluminum parts during layout except for cut lines. A scribe mark is also potentially a crack initiator. A fine point Sharpie works well, though.
The bending moment on the gear leg increases the further you go from the wheel. So the gear should be wider at the fuse top to handle the increasing stress. A few formulas would give you the taper that would result in constant stress in the leg.
The R/C axles work, but those that I have seen are heavier than you really need. Even for a pretty big plane, you can use a 4-40 socket head cap screw with a solid shank. Just sandwich the gear with a nut on each side. Loctite is strongly recommended, else use an elastic stop nut.