As a hidden hinge, I’m using VW Golf MK5 hardware. That’s not through scientific evaluation, more that some were in the boot of a GTi I once bought.
The Passenger Side (N/S/F) model numbers are:
- 1K0 831 411 H (bottom)
- 1K0 831 401 G (Top)
The Driver’s side (O/S/F) model numbers are:
- 4B0 833 421 A (bottom)
- 6E0 831 402 C (top)
To make mounting them a little more tricky, the dimensions of the top hinge bares very little similarity to the bottom. Although a pain, the extra shape required in the pillar will actually add strength.
As you can see, I’ll need to recess the bottom hinge 15.5mm (57.5 – 42) to get the hinge pins to align. When you cut a depression for the bottom hinge, leave clearance for the spring. Once recessed, I’m going to make a cover plate to tidy it all up.
Without reinforcement, the door pillar will probably flex, so on the inside, out of view, there will also be four 18awg steel braces with 38mm dimple die holes as strengthening. Hopefully this will be one tough pillar without being super heavy.
The door may also need some reinforcement and because space will be limited, I’ll use a strip of 3mm steel plate to limit flexing. My worry is, this door is going to be made out of 18awg steel, it’s longer than many 2 door cars and will have every conceivable piece of hardware fitted.
Door Locks – Solenoid or Traditional
To operate the central locking solenoid on the Golf Door Locks, I’ll be using an after-market remote control. I’m going for flush door handles; either Kindig style or even simpler:
Will My Concealed Hinges Work?
I couldn’t picture whether the door would open without fouling, so I had three choices:
- Mock everything up in CAD to the finest detail
- Fabricate it all in steel and tear my hair out in clumps when the door stuck 100% shut
- Cut up some old cardboard boxes and use them as models.
In the picture above, you can see that the initial intention was to mount the face of the hinge just proud of the door pillar. My two minute cardboard template, proved that this wouldn’t work. I wanted a curved front edge on the door, if I’d gone for square I would have been fine.
The right hand purple line follows the edge of the door pillar, roughly where I was initially going to put the hinge pins. The line 65mm to the left is where the hinge pin needs to be. It also means that I’ll have to drop the top hinge 40mm.
Like a modern car, the front edge will rotate inwards behind the bonnet side. Whereas, if I was to us a traditional style of hidden hinge, either the hinge would be massive or that front curve would have to go.
So far, to make this one piece, has taken 5 pieces of steel, all gas seam welded and beaten flat again. Seeing as I’m making the shape up as I go along, hopefully when I fabricate it’s twin, I’ll be using less pieces and doing less hammering. I’ve only been gas welding a couple months and this is my first attempt at panel beating.
Accumulation of Error
The reason I’ve made the A pillars first is to use the hinge pins is a solid datum point. Both horizontally and vertically. If I were to start the car in one corner and fabricated 30cm sections clockwise around the car, I’d be scuppered when I got back to the front.
You might even be able to see, in the panel above, it naturally wants to twist about 8mm towards the rear.
Even if I could perfectly mirror a panel from the drivers side, the twist alone could ruin this project. I have a very old Dunlop tracking gauge, which is essential a scaffold pole with two long sharp spikes you can slide up and down. It’s been quite useful a couple times. As long as the floor is level, you can get instant and surprisingly precise measurement feedback.
As you can see, there is no rear corner on the door. I’ll make two door pillars and get them clamped exactly into position with every possible conceivable measurement taken. Then I’d make two rear door ‘B’ pillars. I’ll be free to move them back and forth until they are right.
When I get to the rear arches, I’ll also use the door hinge pin as the datum.