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Author Topic: Profile Landing Gear  (Read 3329 times)

Offline Steve Tomlinson

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Profile Landing Gear
« on: October 29, 2022, 06:31:34 PM »
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
STEVE Tomlinson

Offline Brett Buck

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Re: Profile Landing Gear
« Reply #1 on: October 29, 2022, 06:50:06 PM »
I used .050 2024-T3, probably heavier than necessary.

     Brett

Online Dan McEntee

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Re: Profile Landing Gear
« Reply #2 on: October 29, 2022, 10:47:12 PM »
  Check out the aluminum sheet in the K&S display at the hobby shop or hardware store. I'm not sure of the alloy but it is what I have heard old school sheet metal guys call "quarter bend" which means that you can bend it about 45 degrees with out it cracking. it's a fairly hard aluminum and landing gear I have made from the K&S .090 sheet had held up to a lot of abuse. Draw out a full size sketch of what you need for height and width and make templates from stiff paper to check size and fit. This stuff can be cut with a fine tooth jig saw blade  reasonably well. File the edges smooth and round them off. You will need a good vice to bend them where you want it. If you don't have soft jaws for your vice, clamp the metal between two pieces of maple motor mount stock and bend carefully with a soft head mallet and check against what you have drawn up as you go. make the top and bottom a little long so you can trim it to final dimensions after bending. This takes some patience and practice, but work slowly and work the metal with the mallet near the bend to get a nice crisp bend. No heat or tempering is required. When you have both sides bent to match each other, finish cutting to length and round off edges. Drill for the axles. You can use store bought axles or 4-4 bolts, nut and 5'32" brass tubing for bushing the wheels. When all finished and test fit to satisfaction, then you can polish them out on  rag wheel. SIG used to sell the landing gear from their discontinued Fazer kit separately and may still have some. Brodak may do the same for one of their profile kits. Du-Bro has plastic profile landing gear in several sizes that you may want to see if they have any that are right for your airplane. You can also "fake it" by making thin sheet metal fairings for your wire landing gear that give that look and appearance. Or make balsa and/or plywood fairings. That's the old school way.
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Offline Dave Hull

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Re: Profile Landing Gear
« Reply #3 on: October 30, 2022, 01:24:13 AM »
"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.

Offline Steve Tomlinson

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Re: Profile Landing Gear
« Reply #4 on: October 30, 2022, 10:53:04 AM »
  Check out the aluminum sheet in the K&S display at the hobby shop or hardware store. I'm not sure of the alloy but it is what I have heard old school sheet metal guys call "quarter bend" which means that you can bend it about 45 degrees with out it cracking. it's a fairly hard aluminum and landing gear I have made from the K&S .090 sheet had held up to a lot of abuse. Draw out a full size sketch of what you need for height and width and make templates from stiff paper to check size and fit. This stuff can be cut with a fine tooth jig saw blade  reasonably well. File the edges smooth and round them off. You will need a good vice to bend them where you want it. If you don't have soft jaws for your vice, clamp the metal between two pieces of maple motor mount stock and bend carefully with a soft head mallet and check against what you have drawn up as you go. make the top and bottom a little long so you can trim it to final dimensions after bending. This takes some patience and practice, but work slowly and work the metal with the mallet near the bend to get a nice crisp bend. No heat or tempering is required. When you have both sides bent to match each other, finish cutting to length and round off edges. Drill for the axles. You can use store bought axles or 4-4 bolts, nut and 5'32" brass tubing for bushing the wheels. When all finished and test fit to satisfaction, then you can polish them out on  rag wheel. SIG used to sell the landing gear from their discontinued Fazer kit separately and may still have some. Brodak may do the same for one of their profile kits. Du-Bro has plastic profile landing gear in several sizes that you may want to see if they have any that are right for your airplane. You can also "fake it" by making thin sheet metal fairings for your wire landing gear that give that look and appearance. Or make balsa and/or plywood fairings. That's the old school way.
  Type at you later,
   Dan McEntee

Thanks!   Great advice
STEVE Tomlinson

Offline Steve Tomlinson

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Re: Profile Landing Gear
« Reply #5 on: October 30, 2022, 10:53:58 AM »
"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"
Good info...thanks much
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.
STEVE Tomlinson

Offline Tim Wescott

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Re: Profile Landing Gear
« Reply #6 on: October 30, 2022, 01:30:36 PM »
Home heat treatment of aluminum is now on my "things to try" list.  But don't worry -- it's pretty far down.

It sounds like the precipitation hardening step could be done in a home oven, or for landing gear a decent toaster oven.  For the annealing step, I've been shown a procedure that involves sooting-up the metal with an acetylene torch with no oxygen, then burning the soot off with a neutral flame -- the idea being that the soot is a good indication of temperature, and because it's sheet metal in air it'll cool off pretty quickly.

(note that heat-treating most non-ferrous metals is backwards from steel: to anneal non-ferrous metal you usually get it hot and cool it quick; to harden it you usually get it moderately hot and hold it for a good long while).

So -- something to try.
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Offline Brett Buck

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Re: Profile Landing Gear
« Reply #7 on: October 30, 2022, 05:54:12 PM »
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.

   That is all interesting, but I just took regular sheet, cut it with my jigsaw, stuck it in a vise, and bent it, no problems.  I also took a anodized Hallco RC gear, one-peice and bent to go up along the bottom of an RC fuse, cut it in half, bent it back in the opposite direction right along the existing bend, and that is still working with no issues 30+ years later.

    For axles, in both cases, I used 4-40 hex cap screws, the same ones I mount engines with, with big washers to keep them from slipping out through the axle hole.

      This was all appropriate for the Skyray 35, which at the beginning, was 36 ounces and subject to more than a few unfortunate pancake landings.

      Brett

Offline Colin McRae

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Re: Profile Landing Gear
« Reply #8 on: November 08, 2022, 05:52:42 PM »
Brodak does make a universal aluminum landing gear set for profile models. I bought the gear for my Shark 402. I did not want to use the single center wheel set-up that came w/ the kit.

Offline Colin McRae

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Re: Profile Landing Gear
« Reply #9 on: December 03, 2022, 11:44:25 AM »
In case anyone is interested. A pic of the Brodak universal profile aluminum landing gear on my Brodak Shark 402.

Offline Gary Dowler

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Re: Profile Landing Gear
« Reply #10 on: April 02, 2023, 02:31:13 AM »
I have a flying friend who made a lot of profile gear from an old aluminum stop sign that he acquired somewhere.  Ive made my own from aluminum stock I bought of about the same thickness  Works well for what Ive needed.

Gary
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Offline Gary Dowler

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Re: Profile Landing Gear
« Reply #11 on: April 02, 2023, 02:34:38 AM »
Brett said

"This was all appropriate for the Skyray 35, which at the beginning, was 36 ounces and subject to more than a few unfortunate pancake landings.

      Brett"

Been, there, done that!!! Right Paul?  LOL!!

Gary
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