818C rear hatch hinge -- another poor design

[FFRWRX]

No matter how tight I do up the bolt/nut on this connection:

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It won't stay tight enough. When the lid is closed the pressure of the struts pushes it up. When I push it down it just moves again, if not right away then with a few opening/closing cycles. Obviously the one bolt cannot hold the torque that is trying to move the joint.

I've considered welding it, but it would be nice to still have some adjustability in the joint to line up the hatch with the body.

Before I spend time coming up with something, has anyone improved this hinge?

Thanks,

Rick

[lance corsi]

Rick, I fabricated my own design for this so I still have the ffr ones they sent. They’re yours if you want them for a backup plan. Just pm me.

[Just puttering]

Cut a piece to fill in the slot, then it cant move up?

[FFRWRX]

The issue is it can, and does, rotate. It is hard to tell if they are in the correct position now. I think they are close. When they are adjusted properly and then I open the hatch, they may move a little. So I would still like some adjustability in whatever fix I come up with.

[J R Jones]

A double slot is unique, no precedents that I know of. You do not have adequate surface area to clamp. You could try a heavy fender washer between the hinge parts to spread the fastener clamp load. Alternatively you could try a tooth washer between the parts, external or double tooth configuration.
jim

[RPGs818SNA]

Somewhat like JustPuttering, I'd fabricate pieces like shown below out of thin steel, bend the end tabs down to fit in the slots, and drill it where the bolts belong. To adjust, make a couple more.

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[FFRWRX]

Unless I'm not understanding what you are showing, I'm not being clear enough. The bolt does not move in the slot, but the 2 bracket pieces rotate around the bolt. The bolt can't be tightened enough to prevent the rotation of the 2 bracket pieces under the load of the struts and the opening/closing of the lid.

[RPGs818SNA]

No, you're right, my mistake. I couldn't help thinking the bolt you were tightening was the hinge point. Looking at the manual, I see it isn't.

So, here's Rev 1 of a piece that might keep that joint fixed in place. It should be thick enough to be effective but thin enough to bend. I'd guess around 18 to 20 gauge. It may take a couple of tries, but I think it would work.

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[FFRWRX]

Interesting. I was looking at them again. I sort of painted myself into a corner. I installed the hinges and adjusted them working from the inside of the car through the rear window opening. Now that the rear window is in place I can't make any adjustments to the hinge with the hatch closed. But I suppose that is like adjusting hood hinges on most cars.

I put the hinges back on the clamp pieces on the car and checked how they line up. Did as much mocking-up and measuring as I could and I'm pretty sure I have them in the correct position as far as angle between the 2 hinge pieces and the location of the bolt in the slots. I was just going to weld them and hope for the best.

But you got me thinking. Maybe I could machine an intermediate piece that fits into both slots and has the bolt hole. It would be a custom piece for each hinge as the bolt position is not quite the same. The one issue is that the bolt hole is as wide as the slot, so no room for extra material for another piece. But I'll give it more thought. The intermediate piece would cause the 2 pieces to be spaced apart, so something wouldn't line up. I'm sort of rambling here and talking to myself, but thank you for the help. I'll see what I come up with. Oh, I'm better at machining than bending metal.

Rick

[RPGs818SNA]

Oh, machining is allowed? (I have neither the equipment not the learning to machine things, so I tend to bend them.) In that case, perhaps you could make a piece that goes outside the arm, under the nut, and extends into both slots. That way you're not limited by the amount of extra material nor the thickness of the piece. I look forward to seeing what you come up with.

RPG

[Mark Eaton]

Keep posting your progress here as I am approaching this dilemma in the next 6 months or so...

[FFRWRX]

Working on something now. I realized that I had a washer between the 2 pieces. I probably shouldn't have. Without it there would be more contact area between the 2 hinge parts and maybe it would clamp together better; and without any paint in that area? But I don't want to just take the washer out and put it all together again just to see if that helps. Or maybe the washer being in there does help.....who knows. As long as I'm making some mods I'll continue with it.

[J R Jones]

I see the washer now. I suggest flange head bolt and nut as well.
Struts should not bottom before full closure.
If the displacement is one slot, not both, try eliminating that slot; maybe welding the (flanged) fastener to that slot.
Can you get a grade 5 carriage bolt fit in one slot?
jim

[FFRWRX]

Here is my overly complex solution. I'm an engineer....we like complicated things....keeps us in business coming up with fixes.

First, when I took the hinge apart I remembered why there is a washer in there:

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The square part of the carriage bolt protrudes through the bracket. So you need a washer to prevent that part from contacting the mating part and preventing rotation. Then again, I don't want rotation.

Anyways, here is what I've got going. This assumes that the hinges were both bolted together in the correct positions. I put them back on the car and took a bunch of measurements and think it is good.

Drew up some new brackets and machined them from 1/4" aluminum. I only had steel too thick or too thin, so went with aluminum thicker than the stock steel ones. The steel ones are 3/16" thick.

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This is how it works. The bolt spacing puts the 2 bolts at the ends of the slot, so when assembled the 2 parts can't move in any direction. Oh, and there are chamfers on the holes to clear the square part of the carriage bolt.

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This approach can only be done after the hinges are adjusted, since in my case anyways they are both different and require different positions for the bolt holes.

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I was going to machine a new bushing since my material is thicker than the supplied one. But a small counter-bore works fine.

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The only difference to the stock setup is that mine will pivot on the bushing that is part of the piece in the car; the one in my bracket will be clamped with the bolt. I think the stock arrangement can pivot on both bushings. In theory, mine will have a little less play in it.

I don't know yet how/if it works since I took the opportunity to paint the underside of the hatch and that has to dry.

For anyone else that has an issue with the hinge, I would suggest getting it all adjusted, then just weld the 2 parts together. And do this before you install the firewall window or you can't get at the hinges to adjust with the hatch closed. You still have a little adjustment at that point; moving the pieces bolted to the hatch, using spacers there if needed.

Haven't read of anyone with an 818C having this issue, so maybe it is only me?

Rick

[Neeraj Ahluwalia]

I had this issue with my 818C and I did not make as nice of a solution as you did.
All I did was assemble the hinges on place, adjust them, then drill a hole through it and put a rivet through. They no longer spin separately.

[FFRWRX]

Glad (in a way) to see that I'm not the only one with this issue. I did consider putting a rivet or steel pin to keep the hinge from moving, but there is barely any room for that. Would have been a much quicker solution though.

Rick

[RPGs818SNA]

The FFR design drawing seems to include an additional screw, item 10, that stabilizes the hinge, but, alas, that's not mentioned in the instructions.

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RPG

[FFRWRX]

The FFR design drawing seems to include an additional screw, item 10, that stabilizes the hinge, but, alas, that's not mentioned in the instructions.

RPG

Interesting. Notice how the part of the hinge where that extra screw goes widens out. Mine obviously doesn't widen out so really doesn't have room for the extra screw. So somewhere in the instructions it must/should say to get the hinge all set up, remove it, and drill a hole for that screw.

I just checked my manual; no extra screw shown and the bracket is like the one I have, not the widened one:

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At least the issue was noted by F5. Maybe it is fixed on all the new ones they are not producing any more? :confused:

[FFRWRX]

Done. Hatch is lined up pretty well, opens with the gas struts, and that joint will never move again!

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[octobersknight]

My hinge design looks much different than these. Mine already has an extra screw on it to prevent rotation. Kit pickup date was Oct 2018.

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I found this thread while looking for something else, and hopefully someone can help here: I kinda feel like I'm missing something obvious here - how does the hinge attach to the hatch itself? Am I supposed to drill my own holes and rivnut them once the hatch is set in place in the opening?

Thanks. (I'll start a new thread on this if I don't see an answer soon)

[lance corsi]

On the under side of the hatch where the obvious mounting points are, there is a piece of aluminum plate inlaid within the fiberglass but beware, the plate isn’t more than .125” thick if that, but you will center your piece that attaches to the hatch underside and scribe the holes, trying to keep the holes within the pad areas. You are also responsible for tapping the holes as needed. There is a plate there. And also take care not to drill all the way through your hatch!

[octobersknight]

Thanks, Lance. I'll give that a shot and will resort to rivnuts if tapping doesn't work.

[Ajzride]

Could someone post a picture of the parts list for these clamps? The PDF version of the build manual is so fuzzy I can't see them. I need to order a set since they didn't come with my coupe top.

[octobersknight]

Hopefully you can read this.

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[Ajzride]

Perfect, Thanks!!

[octobersknight]

Another related question: what hardware did you all use for the hydraulic strut bracket on the hatch? The parts list doesn't show anything at all for the three holes x2 brackets. And is there aluminum inside the channel there too, or do I need to throw in some rivnuts?

I have the collars mounted on the rear engine bay tubing but was stumped last night as to how to attach the upper mounts.

[FFRWRX]

I used self-tapping screws through the triangle plates provided. No aluminum in that area, but 3 screws does a good job at holding it. If they ever come loose I'll put them back in with some epoxy.

Rick

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