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One of these days I'm going to have to learn this CAD stuff! I downloaded Ironclad the other night and their sales guy has been calling me continuously since! At this point it's faster for me to get out the drawing table and t-square and do it by hand.
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Did you run it though cosmos or whatever simulation Solid Works is using these days? Would be cool to see the colored output image.Originally posted by S LathropScratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.Comment
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Here is what I ran. This is Solid Works static simulation, not cosmos.You do not have permission to view this gallery.
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Cool. Thanks! Been a while since I used Solid Works.Scratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.Comment
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Thought I would share my design for a lifting point at the main spar. The main reason I did this is to have a removable picking point so nothing is sticking up above the wing fairing. It's a nice simple design that uses a forged 3/8ths eye (US made, not Chicom crap), a Grade 8 nut that is captured on the bottom using a Home Depot socket. That way the nut doesn't lose strength after welding and I don't have to rely on hand-cut threads. I annealed the 9/16ths socket so I could drill a hole just a bit bigger than 3/8ths where the drive would fit. The bracket is made from .071 4130 plate because that's what I had the most of on the shelf. I'll probably go with .080 for the final copy. What isn't shown in the pics is a hole that I will drill at the bottom edge of the socket for a small loop of safety wire to keep the nut from falling out. I sent it off to be load tested and I got the result last night. I'd say that failing at just a hair under 8500lbs is a success. The forged eye started to let go after about 6000lbs. On the way up I had them stop at 2000lbs to check for deformation and it was negligible. YMMV
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Impressive that they are that strong. I built a pair of these after seeing a picture of them on the forum. I debated using the .100 4130 I had or ordering .125. Ended up using the .100, now I feel better about that decision. I did weld the nuts though, using the nuts that came with the high dollar US made eye bolts. 5.5 oz for the pair.
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Nice testing, now if only our wings had some load analysis.Last edited by spinningwrench; 09-22-2022, 07:17 PM.Comment
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Awesome idea. I am making a pair of these.Comment
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When filling fuel out of a jerry can on floats it's nice to have something like a lifting eye to grab onto on the wing.Comment
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I don't think anyone has any illusions of losing a knot or three of airspeed due to a couple of tabs poking up into the air...not even a Cirrus would know the difference!
I will explore the statement that all forces are all straight and vertical with the twisted strap. As an example I made this little training aid from 1in square tube, the same outside dimension of the front spar attach fitting. If the lifting force was symmetrical it should hang straight. I guess, for the sake of discussion, the question should be if it matters that it is off center a bit. Would the twist strap work? Absolutely...and .125 4130 is not going to break! Is it better to lift on both sides of the fitting? I think so and my on-call aerospace engineer agrees as well. It loads the fitting as designed. I do like the aesthetics of removing the eye and just putting a plug in the fairing. My wing covers would probably have to be modified with a reinforcement in that area with a strap setup. Besides, I could also use that as a hard point for mounting a camera, hood ornament, rocket launcher or some other fun stuff.
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Yeah I figured that's what you meant. My longer post that didn't seem to take in the comment section was that if you were only lifting one side of the aircraft, than you would be applying that slight side lift force. But it wouldn't matter, since the other side was still fully supported on the ground.
If you are lifting the the entire aircraft with points on both wing spar attachments, than again it's lifting straight, vertical, and no side loads what-so-ever, since the fuselage is the spreader bar in essence.
There's nothing wrong with the way you did it or are doing it. I was just providing a simple alternative to others in case they didn't know. I see many builders spend days to create solutions for problems that have already been long solved, and the builder simply didn't know about it.
Peter
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It would seem you could just wrap a short commercial nylon lifting strap around the bottom of the spar at the attach point and be done with it without requiring a separate fabricated piece of metal. You would have to remove the fairing piece of course.Comment
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I think I posted some of these on another topic a while ago. Not very good pictures of the actual bracket made. Used a piece of .125 steel shaped around the front fitting and angled to the slope of the roof. In the center photo, they show that they are slanted which is not their finished position. An AN7 nut was tacked on the inside of the top. The lift bar has been modified not to flex with the load on it as it appears in the photo. Couple of small covers to remove to access the lift brackets.You do not have permission to view this gallery.
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On the 4-place the CofG is fwd of the front spar so you will need lifting lugs on the front spar and the engine mount bolts at the firewall. I made a set for all the spars fore and aft before i realized. I fabricated mine similar to the atlee dodge previously mentioned. Also made a sling so it lifts straight and no side loads on any structure. I used load rated 3/16 chain with clevis at each end and a big 1/2 rated ring. Adjust the lenth of the chains above the sling to get the lift at the C of G for your aircraft then it hangs in the level position.You do not have permission to view this gallery.
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After a lot of thinking I decided to abandon my original lifting eye plan and made a pair of lifting brackets like Atlee Dodge sells. Why? Well, two things. One is simplicity. The Atlee Dodge setup is tried and true and my mechanic friend thinks they are the way to go. Second is when Luke68 shared his story about N247LC and the off-runway excursion. He made his lifting straps like Atlee Dodge and the help was immediate in getting his BH off the runway. In Alaska we fly quite a bit over inaccessible places and the only way out is up...in other words a helicopter ride. If you don't have a place to attach a sling to, the helicopter crew will make one and it's not pretty! Time is money. I would doubt that I would have a pair of screw-in lifting rings handy at all times...and I could get to them.
I got two pieces of 304 SS bar, 3/16 x 1 inch. I drilled a couple of 3/8ths holes using a Hougen RotaCut in the end so I could position them once I put the twist in them. Using a vise, crescent wrench and my OA torch I heated the bars and put a 90deg twist in them, making sure the start of the bottom twist wasn’t going to interfere with the fuselage wing mount or the wing spar. That's why there is a right and left. Once satisfied with that, I put them in place and cut holes into the upper wing fairings to accommodate them poking out. A line was drawn at the base so I could determine where to drill the upper hole in the lifting bracket. Once satisfied with the brackets, cut to length and the top holes drilled, I smoothed out everything, marked the left and right and bead-blasted them to a satin finish. I like them! BTW those clevises are made in the USA, 1T load rating.
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