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Two seat helicopter build.

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Jake2465

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Once I get the cross members welded in, I will need to go ahead and fabricate the landing gear and skids and get sitting on its own legs. I have this set up so the engine gets rolled underneath the frame (between the skids) and hoisted up into position with a transmission jack. Once I find myself in that situation, The engine will have it's own carriage that mates to mounting points on the frame. Once all of that gets done, it's on to the sprag pulley / clutch and the main rotor transmission.
 

JimDawson

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Where's the spinny thing on top? :grin:
 

rwm

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Glad to see you back at this. I have been wondering. What is that frame made of? Will there be any heat treating?
Robert
 

Jake2465

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The frame is 6061 square tube. There is no heat treating on it.
 

Jake2465

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Got what amounts to the beginnings of the airframe welded up. I parked it over the engine to simulate where that would go.

1.jpg

3.jpg

2.jpg
 

Jake2465

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Before I can make plans for the engine, I need to get the frame on it's own legs. Today I went to Harbor Freight and bought this hydraulic tube bender to try and bend my 4130 tubing into the shape of the landing gear legs. That silly tube bender just kinked the 4130... It looks like I just clamped the tube in a vice and bent it with a cheater pipe. So, tomorrow I get to return that abomination and go with my plan B.

Plan B is machining out a set of elbows and slipping 4130 tubing inside them to make the shape of the gear legs.

Regardless of how they are formed, I will also machine out mounting brackets and weld them to the frame. With that setup, I can use a set of AN bolts with castle nuts and cotter pins to secure the gear legs to the frame. this will allow the gear legs to flex and have some spring without putting moment torque on the mount points.
 

Latinrascalrg1

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Awesome project.....I Hope to see it flying one day.

When bending tubing, regardless of it being square or round, I found the best way to get the radius I need is to pack the tube with water or sand and then seal the ends before trying to bend. If you use sand it is usually enough to simply stuff/jam a rag into the ends and then tape over them with some duct tape to secure it in place but if you use water you will need to make the openings water tight somehow, usually welding is involved. Either way will get you a much better more Controllable bend without the kinks.
 

Jake2465

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Awesome project.....I Hope to see it flying one day.

When bending tubing, regardless of it being square or round, I found the best way to get the radius I need is to pack the tube with water or sand and then seal the ends before trying to bend. If you use sand it is usually enough to simply stuff/jam a rag into the ends and then tape over them with some duct tape to secure it in place but if you use water you will need to make the openings water tight somehow, usually welding is involved. Either way will get you a much better more Controllable bend without the kinks.
I have been doing some more thinking on the gear and I came to the idea of machining out some 135 deg elbows so the tubes could be simply cut to length and clamped inside the elbows. I know there is going to be a lot of strain on the elbows, so they will need to be made pretty stout. The helicopter is supposed to have a max gross of 1500 lbs. I also have to account for a less than optimal landing in which the helicopter may bounce a little. So, it's completely possible for the gear to need to hold more like 2500 lbs before reaching yield strength.
 

Latinrascalrg1

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Are you planing any type of Shock Absorption into the landing skids to help alleviate the extra stress you are concerned with?
I know Absolutely nothing about building a helicopter but im kinda in the same question boat with RWM concerning the Safety Factor feeling it may not be enough considering the low end is equal to the Maximum Weight!
Regardless of how you go about it once you get it resolved you can sign me up for a ride, ill pay for the fuel.
 
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tq60

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Before I can make plans for the engine, I need to get the frame on it's own legs. Today I went to Harbor Freight and bought this hydraulic tube bender to try and bend my 4130 tubing into the shape of the landing gear legs. That silly tube bender just kinked the 4130... It looks like I just clamped the tube in a vice and bent it with a cheater pipe. So, tomorrow I get to return that abomination and go with my plan B.

Plan B is machining out a set of elbows and slipping 4130 tubing inside them to make the shape of the gear legs.

Regardless of how they are formed, I will also machine out mounting brackets and weld them to the frame. With that setup, I can use a set of AN bolts with castle nuts and cotter pins to secure the gear legs to the frame. this will allow the gear legs to flex and have some spring without putting moment torque on the mount points.
We had same problem when we got same and tried to bend large conduit.

One needs better dies but us "cheap folks" do things different.

Return to harbor freight to get tubing expanders for expanding exhaust pipe.

Place plastic bag over one and insert into end of conduit tight but not expanded.

Ram pack conduit with sand and plug opposite end.

Now bend and sand keeps it round.

Sent from my SAMSUNG-SM-G930A using Tapatalk
 

Jake2465

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1500-2500-Is that enough of a safety factor?
Robert
There is definitely a trade off between strength and weight to be considered. Helicopters are weight critical and so that causes me to build things lightly. Since this is my own work, it is not likely that others will be flying it. I am pretty good at landing a helicopter and I can kiss the ground if I need to. But, having gear that can take a little bounce is important. It is a matter of how much safety factor is acceptable. Usually, it is likely that when a helicopter touches down, the four corners will touch down at different times. The good part about this is that the weight starts to be absorbed before the full load of the helicopter is planted on the ground.

Also, the main rotor will be providing a good amount of lift that will reduce the felt weight of the gear legs upon landing until the pilot fully lowers the collective. So, more than likely the landing gear legs my only feel a helicopter that weights 150 lbs or less because 90% of the weight is being taken out with help of the main rotor.

I believe the gear legs and skids will approach 25lbs in the current configuration. That is with using 1.25" round tube of 4130 with .065" wall. I believe that size of tube will be OK for this. I have concerns about overbuilding for possible high safety factor and consequently building a little flying tank that guzzles fuel (if 11 gal /hr was not already considered a bit on the gas guzzling side, lol).
 

Jake2465

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Now bend and sand keeps it round.
If you did not use that hydraulic tube bender, then what was used to make the bend?

I have not worked with bent tubing, but is the metal substantially weakened when worked like that? I have had thoughts about just cutting the tubing and slipping them into 135 deg elbows to get my angles.
 

Latinrascalrg1

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I have not worked with bent tubing, but is the metal substantially weakened when worked like that?
I know this question wasn't directed to me but info is info is info right!

Anyway to try and Help answer your question (Simply Because I Honestly Would LOVE to see you fly your creation)......That would depend on the type of metal you are using and how you go about the Bending process! It is very possible to induce stress into the metal that may lead to cracking/breaking of it structural integrity however there is also a very very likely chance that by bending the material you actually add strength through "work hardening." The main issue with being Work Hardened is that it could be a potential problem because of the way the "Hardened" metal tends to become very brittle but this can usually be resolved by an annealing process to help stabilize the internal structure of the metal to be Hard yet flexible enough to NOT be Brittle.

Just thinking out loud I would think you would want something pretty hard but at the same time somewhat flexible but also light weight so you dont end up with a giant paper weight right!
So, Would it be possible to source some carbon fiber tubing to make the landing skids from instead of metal?
Considering you are building a Helicopter I Would think that you posses the skill to produce your own version of skids from aluminum and Carbon fiber that will be Exactly what you need while keeping the weight to a minimum.
If im overstepping i apologize.....Im. not trying to tell you how to build your project at all. I am however Very interested in what you are doing and would really Love a ride once you get it flying (hint-hint lol.) I use to enjoy building toy models, especially anything the flies, but I like your thinking, Go Big or Stay Home....Why build a toy when you can build a DREAM! Good on you, Maybe one day I will be able to summon that strength in myself!
 

JimDawson

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I have not worked with bent tubing, but is the metal substantially weakened when worked like that?
I don't think that would be a problem. The metal on the outside of the bend will stretch slightly, but should not weaken the part unless you bent it several times.
 

Jake2465

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I do have a big roll of carbon fiber that I was planning on using for the instrument panel and fairings. That may be a good idea. Only trouble is that Carbon fiber does not lend itself very well to flexing and tends to crack if any sharp blows are given to it. I also do not have a climate controlled room to make sure conditions are optimal for the resins. I was just thinking that having steel tubing that has well known properties would be easier to work with. I know that the chances of me getting this thing done goes up a lot if the steps I take to make it remain as simple as possible.

Perhaps it may be worth my while to take the tubing to someone and have them work their magic on it and get some 45 deg bends in there. Then, I could attach some carbon fiber fairings to the gear legs later on.
 

Jake2465

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JimDawson

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I think it comes with 3 sets of rollers, not sure about the sizes.
 
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