godofredo.barrenechea(at)
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 Posted: Mon Feb 09, 2009 7:33 am Post subject: 601-HD(s) landing gear |
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Carlos,
I suffered from the same, and took your first option. I filed the Gear Slides (6V5-2) in order to keep the 0.75" clearance between the two slides, accommodating the thickness of the horizontal steel tube.
Since I'm building a tail dragger, I can't include the top and bottom nylon bearings that Larry calls for, but instead, I'm fitting an UHMP (Ultra High Molecular Weight Polyethylene) doubler along the ~10cm that the cross tube touches the slide. This should help in reducing the wearing of the slides.
The solution used to be quite popular some years ago in this list, when I still thought of finishing this project in a couple of weekends...
Cheers,
Godo Barrenechea
601 HD (still in progress)
Barcelona (Spain)
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Time: 09:33:22 AM PST US
Subject: question: 601-HD(s) landing gear
From: "Carlos Sa" <carlosfsa(at)yahoo.com>
I just received some parts from ZAC (the first ones I bought since starting the project). Among them, 6L3-1, the main landing gear lower bearing support.
The internal width of the part is almost 1mm (~0.75mm) less than the nominal 95 mm.
On the other hand, my gear slide assembly, with a 0.75" spacer in place, is almost
96 mm wide. This adds to ~1.5 difference between the assembly and 6L3-1...
I am going to contact ZAC and ask for the proper fix, but meanwhile, I would like to have your input, as some of you probably had the same problem.
I see 3 possible fixes (keep in mind the skeleton is ready for riveting (clecoed):
1) file the gear slides so I can reduce the total width of the assembly; this would require a slight bend of the 2 gear ribs in order to keep the 0.75" spacing.
I don't like this idea, because it might get me into trouble when I install the reinforcing extrusion, 6V11-5. It is already a tricky process with low tolerance.
2) file just the bottom outer surfaces of the slides so 6L3-1 fits. I doubt this is acceptable, as it reduces the thickness of the extrusion where it attaches to 6L3-1.
3) file the slides and add a shim (0.032", or 0.8mm) between the slides and the gear ribs. This seems appropriate, but I am uncertain about the shim. I searched AC 43-13, and found no use of the string "shim" in chapter 4.
On the other hand, "zenair construction standards draft 1-07" says "The maximum shim thickness is equal to the fastener diameter".
Comments, anyone?
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CH601-HD, plans
Montreal, Canada
________________________________ Message 2 _____________________________________
Time: 01:29:18 PM PST US
From: LarryMcFarland <larry(at)macsmachine.com>
Subject: Re: question: 601-HD(s) landing gear
Hi Carlos,
If the fit outside 6V5-2 and inside of 6V11-5 for 6L3-1 is too broad, assuming the bungee cross tubes are welded already, I'd shim the 6V5-2 slides to get the spacing needed along their entire length, one or both sides as needed. The gap for the strut cross tube isn't an issue as it keeps the gear straight and only needs to have a 1/16 or so gap for travel sliding clearance. That work surface can be filed for clearance without any difficulty. I remember filing these surfaces to clear the tube and worrying. There is no visible wear between these parts. The strut bearing diameters do wear rapidly, so do fit up nylon bearings on the bottoms to match.
Larry McFarland 601HDS at www.macsmachine.com
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