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Ali transmission tunnel

Posted: Sat Dec 05, 2015 8:29 am
by Dave Woodward
Anybody have a template for a transmission tunnel that I could use as a starter for 10.

Have been thinking about fabricating an Ali replacement as my glass tunnel blows hot air since putting a toploader in.

Dave.

Re: Ali transmission tunnel

Posted: Sat Dec 05, 2015 3:49 pm
by Roger King
You'd do better to make patterns and make it yourself, Dave. It's not difficult - I had to make a new one for my Hawkirkhamwhatever as the Polish one doesn't fit if the car is carpeted. Carpet should fold around the edges of the ali tunnel thereby holding it off the bulkhead etc. If you're not using carpet it's a bit easier, but would be draughtier.
An original tunnel has three components - the top, and the two sides. The two sides have flanges at the top and a row of pop rivets along the top surface. You may need to bash out (sorry, panel beat) a bit of a bulge for the shifter mechanism. Every original car I've seen has this done.
Also the carpet on the tunnel itself is just one piece folded and glued. There should be no binding along the folds, just plain Karvel carpet (reasonable repro available from Woolies trim).

Roger

Re: Ali transmission tunnel

Posted: Sun Dec 06, 2015 6:36 pm
by amulheirn
Interesting - thanks Roger. I was thinking about making an ali tunnel myself after seeing pictures of Nik's new 289, which appears to have one. I've got the Hawk fibreglass one in the garage, so I thought it might be easy to reproduce in aluminium.

What software would you use if you wanted to draw up plans and get this cut by someone professionally? Or do I just get a pair of tinsnips and a straight edge and start cutting and folding?

A.

Re: Ali transmission tunnel

Posted: Sun Dec 06, 2015 9:12 pm
by CobStang
Go to your local builders merchant and head for the cement shed, the pallets that the cement is shipped on are usually covered in a sheet of cardboard that is @2mm thick and @1m sq. This is superb for making patterns, for the folds just score 1/2 way through with a Stanley knife and it will bend.

When satisfied you can either make up yourself in Ali or take the patterns to a fab shop.

Re: Ali transmission tunnel

Posted: Sun Dec 06, 2015 9:30 pm
by amulheirn
CobStang wrote:Go to your local builders merchant and head for the cement shed, the pallets that the cement is shipped on are usually covered in a sheet of cardboard that is @2mm thick and @1m sq....
Thanks CobStang - that's a useful tip!
Roger King wrote: ...Carpet should fold around the edges of the ali tunnel thereby holding it off the bulkhead etc. If you're not using carpet it's a bit easier, but would be draughtier.
Roger - so the carpet is sandwiched between the edge of the tunnel and the bulkhead? Does that mean it is exposed to damp from underneath? Do you have any photos you could share?

Thanks again!
Andrew

Re: Ali transmission tunnel

Posted: Mon Dec 07, 2015 12:05 am
by Roger King
The carpet does indeed act as a 'gasket' between the various panels, as Dan Case puts it.
OK, so an original car has the following:
The front, fixed section of the trans tunnel, ahead of the two tubular dashboard cowl braces, has fibreglass sides which are part of the footboxes. These have a horizontal flange at their upper surfaces. These are covered with black Karvel carpet, glued to the footwells and folding over onto the top flanges.
There is then a right-angle aluminium panel screwed to the two flanges and the bulkhead, which forms the 'roof' of the tunnel over the gearbox ahead of the two braces. This is removable, and is also covered with black Karvel, folded over the edges and glued. This panel is screwed to the fibreglass tunnel walls and the ali bulkhead with 4 x 2BA machine screws, lockwashers and nuts. A Kirkham will have this panel rivetted to the fibreglass and ali of the bulkhead, which is incorrect.
The removable part of the tunnel is made of rivetted flat ali panels and overlaps the front, fixed, tunnel section already described by about 1", joining at the point where the two bracing tubes are. This tunnel is also covered with black Karvel, folded over the front vertical sides and the horizontal top. The carpet is glued to the ali and there is no binding trim anywhere on the tunnel.
Therefore there are a number of layers of carpet pinched between components of the tunnel in various parts of the construction. I don't know how damp they would get in use, hidden up over the gearbox, but it doesn't really matter as that is how AC did it, so that's how it is!
I'll try to find some photos, but I'd have to do quite a bit of dismantling to show this if I can't find any, so I'm not promising.

All the above with the fantastic assistance of Dan Case in the US who has an original, unrestored car, and from my own finely-detailed examination of COB6029 in the Haynes Musuem workshops.

As for making the tunnel, Mark's card mock-up is a very good idea. I have never used a drawing programme in my life - I have a drawing board, a ruler and a pen, which seems to work OK! For my tunnel fabrication (and many other panels) I used an electric jigsaw with an 'aluminium' blade (tin snips distort the metal) and a home-made folder in a large vice.

Re: Ali transmission tunnel

Posted: Mon Dec 07, 2015 12:30 am
by clive
Dave, where is the hot air coming in? I used to get air blowing in from the front of the tunnel, lifting the carpet, which was extremely uncomfortable on long hot sunny trips so I filled the gap with dum-dum putty. Problem solved. Only thing is, it isn't so cosy in the winter.

Re: Ali transmission tunnel

Posted: Mon Dec 07, 2015 8:23 am
by Dave Woodward
CLIVE, as you suggest it comes in at the front, but also along the sides.

The tunnel was refashioned by Baz when the new tran went it and he did a fab job (no pun intended) but a bit unfair to expect him to make it airtight!!!

Will take a look at dum-dum putty.

Cheers.

Re: Ali transmission tunnel

Posted: Mon Dec 07, 2015 9:46 am
by Roger King
How does air get into the front of the tunnel? Doesn't the tunnel overlap the front section, so air blows over the gap? It's a while since I had the Hawk so I can't remember.
Carpet rolled over the edge, as originally used, would seal against air. I wouldn't have thought too much water would get up there, but if you're using a decent wax spray it wouldn't matter.*

* I still used Dinitrol on my Hawk underbody. Any open fibreglass fibres will soak up water like a sponge and start to blister, so everywhere you have drilled through gelcoat, or any crack, or panel edges, is vulnerable.

Re: Ali transmission tunnel

Posted: Mon Dec 07, 2015 9:58 am
by amulheirn
For some reason I thought you'd mentioned using Terosol Roger?