My hold-open door braces seem to be too loose. They are apparently supposed to have a bushing where the mount screws go through the ends, but it’s gone (and are supposedly unavailable). The center pivot seems sloppy as well. What can I do?
Search strings: door stay, door brace, loose brace, loose stay, tighten up, loose door
Technical Editor:
You can snug up the brace center pivot by re-staking it. The bushing system used by Beech on the ends was a waste of time and money. Most of the excessive wear discovered by owners is because someone lost the pivot bushing, and never noticed. Very few of the planes still have the bushing in place. Without the bushing (and often even with it), the hole in the brace gets hammered out; and the screw won’t stay tight.
Use a 100-degree countersink to bevel the two end holes (only if needed). Use a stainless-steel Tinnermann-style washer in the mount hole. Fasten the end with a 100-degree Philips flat-head screw. If the self-locking tension is lost in the anchor nut, put a dab of red Loctite on the screw threads (not the head). Tighten the screw enough to put some drag on the brace.
Washers: http://www.aircraftspruce.com/catalog/hapages/stainlesswashers.php
MS24693C Screws: http://www.aircraftspruce.com/catalog/hapages/ms24693.php
You can use this system on both ends of the brace. Take care to check the clearance of the folded brace, both with the screw heads and between door and jamb. If necessary to get a good perimeter fit for the washer, use one washer size smaller than the screw, and slightly open up the center hole with a Dremel stone. You can also use multiple flanged washers, and you can use standard washers between door and brace to get the brace out past any plastic door edge trim.
This method of “bushing” the mounting screws lets you keep the braces adjusted as snugly as needed, despite gradual wear. You can also just replace the Tinnermann washers if wear becomes excessive. These braces are unreasonably expensive, so salvage yours if you can.
UPDATED 8/28/2008
The SS Tinnerman washer approach with the flat head screw is what I began using years ago, long before I wrote this suggestion on BAC. Its only real drawback is needing to have either tight threads in the anchor nut, or a good selection of structural screws. You need to be able to select a screw length on which the shoulder will bottom out on the anchor nut, to keep the screw from backing out, if the anchor nut no longer has tight threads. Another possible drawback, depending on what you can find, is that the size ten (-3) SS Tinnerman washers often have a flange OD that is too large. If that’s the case, you’ll need to use a Dremel and a stone to enlarge the hole in a size 08 washer. Sometimes a given lot of 08’s will let a -3 pass through; or will be a light press fit on a -3.
I used this approach for a long time, until I obtained some stainless steel tubing suitable for custom bushing manufacture. The advantage of the beveled washer approach is that you can adjust play by adding more or fewer beveled washers, making it easier for the owner to take up play (if they have some mechanical aptitude). Another advantage is that the parts are unlikely to become lost.
The advantage of the bushing approach is that you can make it the exact thickness needed, so that the screw clamps the bushing to the frame, while the brace rotates around the bushing. Another is that you do not require an assortment of screw lengths, as the ‘stock’ screw length will clamp down the bushing. The drawbacks are that the bushing can again become lost, if care is not taken during door stay R&R. Another drawback is that the only way to remove play is to make a larger bushing, or expand the existing bushing a bit more. With either approach, I normally place an AN960C-3L thin (‘light’, stainless-steel) washer between the door jamb and the door stay, so that the beveled washer or bushing have a solid base. You often also need washers for spacers between the stay and the door, so that the stay can properly clear the plastic trim. You naturally must take care to leave enough space for the stay to fold on itself when the door is closed, without binding up on anything.
The only screws suitable for this application are AN525 washer-head screws; or AN526C stainless steel truss-head screws. The AN525 screws allow the most clearance, when the door stay is folded in on itself (door closed). Also note that these pivot points must regularly be lubricated. I use a dab of grease for assembly, and LPS-2 for ongoing lubrication.