The Murphy Builders Site

I am in the process of completing a gull-wing cargo door on a Moose and looking for a lockable flush mounted door latch
What have others used in this application??

Jack Joos SR193

Hello Jack,

I have a latch mechanism/handle from Austin Hardware along with 1/4" welding rod that engages front & rear of door flange. I've seen another solution where a builder used welding clamps (obviously only engage from reaching inside the door window) then lock the door window with a car-door electric (key fob) pin mechanism. I've seen several other creative solutions.

Ted

Hi Ted,

I've looked at the Austin Hdwr catalog, but it's not obvious that the flush mounted latches can be operated from the inside.
Which specific Austin latch item are you using?

Jack

Handle is part # ALH 279L SS 1250
I can't the receipt for the inside latch mechanism, as a friend ordered those. Pictures attached of several implementations.

Ted

Check www.hendricksmfg.com Very nice flush mounted latches.

Ouch! $430 for a set of two! I know I have less than $80 for all three of mine. But then, I'm cheap <grin>

Thanks for the pics and info guys---now to make a decision on which latch arrangement.

Good day all,
I'm reviving this thread because I want to use a system like the latch shown in the photos above for my gull-wing doors. Ten years ago I got a demo flight with Curt (Rebflyer@aol.com) and (to the best of my recollection) he constructed a DIY 3-point latch system very similar to the ones described here. Does anyone know of (of have any pictures of) a DIY 3-point rod-actuated latch system for our gull-wing doors? I stress the DIY feature only because I can't seem to find a flush circular actuator latch for anything less than $60 online. Seems like a simple concept to duplicate.

I acknowledge that there is a well-known 2-point latching example in the archive photos that has been adopted by several gull-wing builders.



Can anyone comment on the robustness of this design? I have a nagging concern about the stresses on the delrin block that sees some bending moments while it holds the door against the fuselage (when the latch is engaged). Only two rivets hold that block in place.

In contrast, the advantage of these rod-actuator latches is the fact that the rods (and the guides) take those stresses.

Anyway...looking forward to hearing from folks on this....maybe even Curt can send pictures of his plane?

Rob

I copied my handles from Jesse's doors, which I believe you posted a photo of. I can tell you that it's a very strong design and I have had zero issues with it. I used a piece of delrin at both the lower and rear insertion points and it'e fine. I used a piece of 3/16" 5052 fuel tubing for my actuator rod; if I did it gain I'd use steel like Si and Matt Smith did. They also incorporated a spring in their doors that works to hold the linkage closed. A good idea. I used a angled slot in the lower one (like Jesse, I think) and cut an angle on the end of the linkage that enters the rear door frame. As you close the latch these two items tend to tighten the door against the frame. I don't think it takes too much force to hold the doors closed, especially if you get a good fit at the front where some have had problems. Craig

Thanks for chiming in, Craig.
I'm glad to hear you haven't seen a need to redesign the latch system...given what you've done with the landing gear on your plane, I'm confident that if the latch needed reinforcing, you would not have hesitated to do so! :thumbup:

Jesse/Si's latch also appears very simple to make, and since it seems to work, I am always happy to follow others rather than break new ground.

Some questions on the details of the design...Hopefully Si/Jesse, or yourself have the answers:
1) The outside handle is custom-shaped from aluminum block and the pivot bolt holds it onto the assembly. But what is the exact mechanism by which the handle is 'keyed' to the pivot bolt to transfer rotational forces (i.e. opening the mechanism)? There appears to be a rivet through the handle that acts like a 'set-screw'...does that stop rotation around the pivot bolt too, and if so, how?
2) Is that a delrin spacer between the outside handle and the door skin?
3) On the inside, how is the latch handle 'keyed' to the pivot bolt (again to prevent rotation around the pivot bolt)? I can see the bolt goes into a nutplate to hold the assembly together, but the inside and outside handles need to be 'keyed' to the bolt shaft to transfer rotation of the outside handle to the inside mechanism (most commercial latching mechanisms use square shafts to get around this 'keying' issue).

Thanks to all of you in advance,
Rob

Rob,
On the outside handle I used a stainless machine screw through one side of the handle and the bolt shaft, and tapped into the other side of the handle. There may be a Delrin spacer. I can't remember....Now that I think about it there has to be a good nylon or Delrin washer there because the inward pull from the latch translates there.
On the inside its a similar deal, but I just used a roll pin. My inside latch/handle is two pieces. The little block where the bolt goes through is actually held onto the rest of the latch with two machine screws tapped into it. That's what makes it look like a nut plate I guess. The roll pin goes through that and the bolt shaft. It would have been neater to machine the whole latch from one chunk, but I don't have the technology.
I used camming action as Craig described on the latch and rod interfaces with the fuselage. I got away without using springs by creating a ramp into a detent for the lower latch in its Delrin striker plate. Took some fiddling to get it right, but works great. I used thicker walled aluminum tube for the rods that's 6061 I think. No regrets there. Only issue I have is I get a little air gap at the front of the door over 95kts or so. Could be remedied with a better seal or I was thinking of putting a little spoiler strip on the fuselage right in front.
Jesse

Thanks a ton, Jesse.
I think I have all I need to move forward.

It would be a huge help if you could upload a photo (at some point) of the area where the roll pin goes through the aluminum 'block' and bolt. A 'bird's eye' view of the whole thing... just to get a sense of thicknesses of the various components.

Thanks again,
Rob

Will do, may be a couple weeks though. Still on duty for fire season away from home, even though it's raining buckets for the next few days.

Jesse,
I think this photo (taken from Craig's online photo album) clears things up.


So, no need for you to send another.

Rob