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Thread: Pull down latch for murci door

  1. #1
    Senior Member dratts1's Avatar
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    Pull down latch for murci door

    I have heard of the Cadillac pull down trunk latch and people have talked about it for the doors. I don't like the way I have to close my doors and would like a soft close. Has anyone ever actually done this or is it just an idea?

  2. #2
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    With recent happenings, it looks like I won't have a doner car for my own project until late this year. But when I DO get started, I plan on doing the scissor doors early in the project in order to have it done before the rain seasons. I intend to address allot of known problems with scissor doors including possibly those you mention. I'll let you know what I come up with.

    One thing you may want to consider is a fat and soft seal at the roof. This MAY be able to kill two birds with one stone, both softening the closing and helping prevent leakage.

    If what you are after is a soft click, I don't know about Cadillac but if it were me, I'd use polished stainless parts of my own making, keep them well lubed and carefully selected springs. A word of warning, if you make the latch parts yourself, use the same grade of metal for all the catching mechanisms. If one grade is harder then another, it'll warp the other much faster then normal.

    Scissor doors strike me as something you're only going to get right by making the working parts for and fine tuning yourself. It's just too fine a process to build by just swapping parts and welding a few things in place.
    Last edited by ronin; 08-10-2012 at 04:27 PM.

  3. #3
    dratts1, are you still working on your latch or is the door skin bonded on already?

  4. #4
    Senior Member dratts1's Avatar
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    I have the door skinned and the Mercedes latches installed. I have yet to witness how the soft close mechanism works so I don't know how I would have to install it. I assume that the trunk mechanism might have to go on the bottom of the door. I see that BMW and Audi both have soft close door options and could possibly mount like the Mercedes. I may have to reskin my doors anyway. My mechanic broke my Sebring windows and I have Marks plastic windows now but I want to install power glass windows eventually. I have a roadster or I would have participated in murci-me's window buy.

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    There are 3 things I am 100% sure of and willing to bet any one of my guns one. 1, that I can (skill wise) make a complete shell for a Camaro that resembles a Lamborghini Aventador (how accurately is somewhat questionable), 2, that I can install the glass and make it water proof and 3, that I can install scissor doors and make them both water proof and reliable. That's because, even though I know little about car mechanics, these are things I understand very well in general principal with allot of experience in doing and can make them work on virtually any application.

    That said, I can give you pointers about how some things might be worked and adjusted in order to accomplish your goal, but until I have actually built, tested and proven the functions of scissor doors, I cannot give you any specific impute and say with full confidence that it will work. I am 97% sure that on both maters of waterproofing and smoothing the operation of scissor doors it's going to come down to fine tuning.

    So for now, here are a few pointers. Things that tend to work in general principal. These are things that MAY be worth trying but again, I can give you nothing definite until I've pulled it off myself.


    * Make the connections very durable. I would add reinforcements to the frame where the hinge and scissor doors are mounted. The attached picture shows what I am talking about. The reinforcements, if made correctly and out of the correct metal may increase weight a little, but if made right will also make the door more durable and more precise in it's movement. Think of a milling machine milling a piece of metal tightly clamped to a heavy milling table VS a drill press against metal held in place by your hand. Notice in the picture that the reinforcements use a pattern that makes a good balance between weight and durability. This is one of the areas where fine tuning come in.

    * Fit the weight of the door to your gas shock. Figure out your door's overall weight and get a gas shock rated for that general ballpark. One clue as to what "power to weight" you want in your gas shock is that real Lamborghini doors will come up on their own if the door latch is remotely disengaged as shown in this video:
    AMAZING Remote control Lamborghini Doors - YouTube
    So I would work on balancing the door until the point where they open like that just by disengaging the door latch. If they open that slowly but on their own, then closing them is probably going to be fairly soft. How to balance them is something that; again, comes down to fine tuning. My initial thought would be to start with a gas shock that is just a tiny bit too weak for your door's weight and drill strategically placed holes in different parts of the door's skeleton and fullers in the reinforcements but it's ultimately a matter of each individual door and something I would have to play with hands-on to be able to give you a definitive formula that I know will work. You could also go the other way and start with a gas shock that's a little too powerful and add weight to your door (by welding washers on to the skeleton or something like that) until the weight and gas shock power are balanced.

    As for the water proofing, I think this is going to be more subject to fine tuning then anything else mentioned so far, but the first thing that comes to mind for me is to put a miniature "storm drain" along the door frame of the car and as you can see in this video (at 1:06), the Lamborghini Aventador does in fact have that.
    2012 Lamborghini Aventador LP700-4 Start Up, Exhaust, Test Drive, and In Depth Tour - YouTube
    Of course, that counts for little of the Aventador doesn't have a tight seal. On the real car, the "storm drain" and rubber seal are all the same piece. If you can find that and make it work, great. But if not, you may need to make your storm drain out of aluminum or plastic and add a thick rubber seal over it. That can not only seal your door like a refrigerator but also serve as a buffer in closing the door.

    * When it comes to door latches, I have actually fixed a couple before and found them very similar, though larger and easier to work with then sears/hammers/triggers in handguns and some rifles. And I am known for my trigger jobs. If you want these things to work smoothly, you have to polish them, use carefully chosen spring tension and some use. This "use" is referred to in firearms as the "break in" period, where rubbing the working parts together allow them to conform and work better. I never did this myself but I have friends who have sped up the process of breaking in triggers by adding metal polishing compound to the working parts. Might work in cars. I can't say though. Never tried it at all myself. If your main objective is smoothing the "clicking shut" part of closing the door, polishing and straightening out the working parts will probably have a greater impact then everything else combined, though the other factors will probably give you improvements in their own individual aspects.
    Name:  scissor door reinforcements.JPG
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    Last edited by ronin; 08-12-2012 at 05:58 AM. Reason: improved discriptions

  6. #6
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    how about a timing belt bearing as hinge, they run smooth, are incredibly durable, can take a hit, and arent wobbly at all. wouldnt it be possible to weld a bar to the pulley itself and mount the door on that, and the bearing on the chassis. something like this http://img.eautopartscatalog.com/live/A530190874RUV.JPG

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