Pocher 1/8 Alfa Monza revisited

[Dougritt]

I really like the heat shield solution and the floor is totally cool!

[Dougritt]

Well done!

[Jo NZ]

Thanks Doug. I get a real kick out of finding material that looks right ( e.g. for the floor) in a hardware store!

[Jo NZ]

The body is ready for painting (or it was until I saw the defects in the photos!) and I'm waiting for the weather to improve before I spray it. I have block sanded it using 150 grit, initially, to get it flat, continuing to 800 grit before priming. There are a lot of areas where the plastic has warped or slumped that need flatting off.

In the meantime, here is the front bulhead - all holes have been filled, and new ones drilled in the correct locations. I have removed the protruding swaging lines - they should be indented, however I decided not to go that far...
I've also filled and recut the cutout for the steering column. I found a ready supply of red plastic in the wheel building jigs, and used gap-filling cyano to fix the plug. It works pretty well.



I've also machined the fuse boxes and cable clamps, from a material called Tufnol - it's resin bonded fabric, and it's been in my scrap box for a while (30 years ! This is when you say to yourself - "I knew it would come in handy one day..."). Tufnol was the nearest I could get to the brown bakelite used.

[Jo NZ]

After a little break (well nearly a year) when I started a Brooklands Bentley, among other things, I've come to an impasse... both cars need louvred bonnets. I made the bones of a press tool a long time ago but never made the tools - it went on the "too hard" pile because I'd read that the forming was done in the female half, and I couldn't work out how to make it.
Then I saw some crude tooling producing perfect louvres on YouTube... With the male side producing the shape.
Here's the press tool



and the first attempt at a punch



and die



The first tool deformed the metal on the second punch, so I made one with more land area, and also set the cutting edge aligned with the edge of the tool so that it's easy to stone to sharpen it. The width of the slot in the die doesn't seem to be important - but getting a good alignment of the cutting edge and the edge of the slot is



Louvres from the first tool are on the left. See the distortion behind the louvre. I also made the second punch a bit longer to better replicate the original - the Pocher louvres are about 1.5mm too short. Material is 0.4mm Aluminium sheet (not annealed, Dan, but I think I will anneal the top panels to get the curvature)



The first test piece, with correct alignment. Louvre spacing is made by machining the die width after the slot to the correct spacing, and butting up the previous louvre. This has a thin coat of etch primer



...and painted. Excuse the lumps in the paint, I was sanding elsewhere in the garage and opened the outside door on a windy day...
Incidentally this is a rattle can of paint I had handy - Austin Morris Cherry Red



Onto the real thing - the first panel for the Alfa (bonnet side, top left)



The second - the right side. There is a small return on the bottom, created with a squeeze in the vice over 1/8" steel rod. The vice soft jaws are cut from an old leather belt.





The first set of louvres. Before I punch the second set, I need to machine a slot in the die holder to provide relief for the return on the panel



Jo

[MODEL A MODEL]

Hi Jo!
It all looks pretty good to me! -Have you time to try another experiment? I've noticed on some 1:1 louvers a hole was drilled at the ends to help start and control the tearing of the metal sheet. I haven't tried this but since my Model A has some big louvers, I've been studying all the different ways that people have thought of . . . making louvers.

Your photo with the painted and bare metal panels, look pretty good to me! I don't think you need a female tool. But for another experiment? put some thin tape on your male die, (3M transparent tape is fine) wax it, as a release. Make a removable container where your "female" tool will be, and fill it with almost anything like epoxy , casting resin , . . . and lower your male die into it. Let it cure of course, and raise the male die. -The lower die, the female part of the conforming die doesn't really do anything but restore the louvered metals shape. The real work is at the cutting edge. Two-part epoxies sold at hardware shops should be able to handle the aluminum.

I do go on! I'm sorry!

Your louvers look great! -Don

[Jo NZ]

So - ready for fitting and trimming - the bonnet side panels



And the scrap....



Must get some more 0.4mm sheet

[ThierryD86]

I'm very inquisitive, Jo NZ !
How did you make your punch and your die ?

[Jo NZ]

The die was a strip of 2mm thick steel with a 2mm slot milled into it. The punch was cut from scrap steel - like this



and being of indeterminate ancestry is probably a bit soft. I milled it to leave a 1.3mm high rectangle and then created the rounded profile of the inside of the louvre with files. The cutting edge is honed on an oilstone to ensure a sharp edge. Making the tools is easy - but you can see from the scrap pile that getting a consistent, flat, non-angled and clean cut is where the magic comes in. It took several evenings to get it right. Even mis-counting the louvres is a trap for the unwary....

[Jo NZ]

Starting to fit the bonnet side panels

[PROPELLER]

Very impressive Jo.
Congrats!

[Jo NZ]

I've made the die for the top louvres. They taper so vary in length, but the difference between the front end vent and the rear is only about 2mm over 12 vents. I decided to make them all the same length - I can always go back and produce 12 forming tools if don't like it...

I annealed the top panel. I tried my heatgun but at 1600W it doesn't get hot enough. Flame annealing with a gas torch works fine - coat the sheet with soap, as soon as it goes brown/black it's done. Any more and it will start to slump.

The top and side being fitted



The curve on the corner of the bonnet is tapered. I found the ideal forming tool - a jewellers ring mandrel




Nearly fitted - I'll make the other side before I get everything trimmed

[markus68]

Very instructive. My next project will be a monza and i have to do the same some day. Markus

[Jo NZ]

The exhaust side

[MODEL A MODEL]