RK saloon bonnet

[Parazine]

You're into "A" level dismantling there. There should be bent over tangs on the front and rear of the bonnet tops, hinge area. Bending these up will allow (!) the hinge pieces (solid Nickel by the way, can be polished up) to slide off the bonnet and the whole hinge falls to pieces.
BEWARE HOWEVER, the tangs may be rusty and thin and will  almost certainly be tired and old. If they have been moved before, they will probably break off due to metal fatigue and leave you with no way to secure the bonnet hinge. Welding them is difficult and annealing them is also problematic. Hence all the cars with bonnets that move about and go out of shape instantly.

[David.H]

Thank you Parazine....
My painter / body-man said I should number them, but didn't mention the tangs, I will look. If I can avoid dismantling the centre section I will. Die-ing down to 3/16 could work - bit flimsy- , but (stop you ears purists) 6mm will be the first thread to try....there may well be enough meat to get M6 out of it. 
David

[squeak]

Before you reach for the die, the furniture trade do a barrel nut that reaches up through the channel to where the good threads are. I note they are available in 1/4"  6mm  and 8mm.
https://www.ebay.com.au/itm/1-4-M6-M8-M1...0677.m4598

[David.H]

That is an idea! I have some hex body rivnuts that I could try, but I ran an M6 nut uo the thread with little effort.....
The bonnet trial fitting (easy with no paint!) went ok with the correct way up bracket.The side clips were a bit tight and the bonnet sits too high behind the filler cap. I think if you tighten the centre bolt too much of course it bends the extremities of the hinge up....hence the need for spacers.The new rubber seals appear as if they are too thick and it is tempting to carve a bit out of them....
I will try and post pictures tomorrow.

[Parazine]

Here's some pictorial evidence at last.

This is the plate spacer from my late '29 RK saloon, a generally very original car so I wouldn't be surprised if this is way Austin did it. BTW, you can see the troublesome tangs here:

   

Here's the brass spacer I made for my '27 Chummy, it just drops into the U section and supports the special hinge bolt. More tangs to be seen:

   

And a friend sent me this picture from his Chummy, showing how he got round the vaporising tang problem; a couple of self tappers inserted through the hinge and bonnet:


  Ian Bonnet.JPG (Size: 144.14 KB / Downloads: 196)

[Zetomagneto]

No need to bend the tags at both ends if you can remove the brass hinge rod first then the hinge sections can be slid away. They may be stuck by old paint but there is no physical fixing so just patience needed.
If your tags are good at both ends just removing the rod will enable you to replace the threaded fixing.
I would try to avoid bending the tags if at all possible

[Parazine]

Yeah, it's a definite maybe that the rod can be moved but I've found with all the early bonnets I've dismantled (quite a few over the years), the amount of force required to start the rod moving is likely to distort the bonnet tops or break the tangs off. Don't ask how I know...….

Still, sometimes you're lucky!

[David.H]

Some pictures of the hinge, the bar and how the front is sitting too high...trim the rubber seal? Bend the hinge...!
There also seems to be a bit of disagreement as to whether the bar sits under or over the bracket? My rad end bracket has a depression (dished), but the bar has nothing similarly shaped. 
All this excitement over a bonnet bar!!!
David

[Parazine]

Your bar is a cut down item from a later car (the original was about 3/4" wide) so this may help explain the ill fitting of the bonnet.
The rear mounting method was originally to put the end of the bar, which is flattened, into a clip, spot welded onto the scuttle with no securing screw. You can't see the clip on my photo's but I'll try and add one later. At the front, the bar was fixed with a 3/16" screw and nut to the rad bracket (Usually 2BA or 5mm is used these days). I'm sure it fits on top of the rad shell bracket. Fixed in this way, it floated longitudinally.

[David.H]

And your friend's bar appears to have the flanges down, not up....!
D