All Alloy Cup progress

[Ruairidh Dunford]

You can get original pattern ones off the shelf Bill - they work very well, see:

https://www.theaustinsevenworkshop.com/p...t-pipe-swb

and

https://www.theaustinsevenworkshop.com/p...b-tailpipe

I have this type fitted to all my SWB cars, including the Cup.

[AllAlloyCup]

Thanks for this Ruairidh,
Will their SWB downpipe go over or under the “hoop”
on the Cup? Plus Any idea what the OD dia is at the silencer end?
I’m using a Ruby manifold, not sure if that affects alignment
In a Cup situation? That’s why I thought I’d need to make one.

Regards

Bill G

[Ruairidh Dunford]

If your hoop has been made correctly the pipe should lay inside it and go through the hole in the front cross member and the tailpipe in the hole in the rear cross member - so I understand.

I think the outlet pipe is 1" and a small amount of careful tweaks should soon see it all fit perfectly, in my experience, Bill.

[Peter Johnson]

FWIW I could not get the downpipe to fit either side of the hoop. The new pattern downpipes are nothing like the original pipe on my New Zealand car. In the end, I cut the flange off at the manifold end and took an inch or so out. With a bit of bending, the pipe travels through the hoop. It is, however, very close to the carb so I have wrapped it in some insulation.

Peter

ETA. I haven’t used the chummy pattern silencer. I decided to use a stainless round silencer to similar dimensions, but without the mounting brackets.

[Ruairidh Dunford]

I don't know how long ago you bought the downpipe Peter but I have noticed a marked improvement with ones produced in the last couple of years, against ones previously available - they follow the original lines much closer.

My own Cup should be back home this week and I will be in position to see if it all fits, along with an original fuel tank support bracket (hoop).

[AllAlloyCup]

Thanks Peter and Ruairidh ,
For the information about exhausts and fitting.

I’m tempted to stick to a 35mm pipe dia from
Manifold to tailpipe, as I have loads of it,
Plus the downpipe came off a working Trials special.

As Peter points out it’s the hoop that’s the issue.
It’s position is fixed by the rear engine mounting bolts.

If I can lift the existing downpipe over the hoop
A very shallow Z shaped joiner pipe would mate neatly
With my Cherry Bomb silencer which has 35mm entry points.

On Tom A’s car the tail pipe was about 6” long with a fish tail ending.

Do most Chummies of that era simply have a very short tail pipe pointing
Towards the near side?

I believe later A7’s had tailpipes up and over the rear axle
All the way to the rear of the body?

Any ideas about rear tailpipe arrangements appreciated.

Regards

Bill G

[Ruairidh Dunford]

Handbooks are not my favourite source of historical evidence (quite a bit of artistic licence in them!), however the set up on page 22 here: http://archive.a7ca.org/wp-content/uploads/PL_353I.pdf gives you an idea of the standard factory set up. The ones linked to above are very close to this in design and the longer tailpipe you mention came in with the LWB chassis (I think).

[AustinWood]

The Chummy (and my fabric saloon) tailpipe is short and turns inwards. It's integral with the silencer.

[AllAlloyCup]

  745B0454-5F00-4960-B757-E4A431294162.jpeg (Size: 70.26 KB / Downloads: 353) Hi Jim

As Ruairidh suggested I checked out the parts list illustration
and could see how short the original  integral tailpiece was.

As a Cup and also a “special” my Cherry Bomb is
Very unoriginal but will make a nice sound!
I’ve got one on the tail end of my TR3A system :-)

I found an extra steel manifold flange bought a while ago
and using this as a spacer, plus the gasket etc. It
Dropped the old exhaust down a bit, plus
I put the pipe in the vice and squeezed some gentle bends in it
Plus ovaled it where it passed under the hoop.

Sorry hoop but I ground about 1/4” off your bottom edge.
This gives a 1/4” clearance there.

As the engine, and exhaust are bolted solid to the chassis
there’s not much possibility of flexing or rubbing anywhere?
There’s still the radius arm clearance, is 2” sufficient? At the intersection point.

So may just add a short tailpipe and get the one pipe joint
silver soldered or brazed, though the join is far enough away 
from the exhaust manifold to perhaps use plummers solder?

Will try brazing first I think.

Thanks to those adding ideas.

Regards

Bill G

[AustinWood]

The chassis does flex quite a lot going over uneven ground. The hoop may come very close to the exhaust.
On the Nippy I used to drive there was only one way to sit on the set, It brought the right knee against the body close to the door and right foot on the floor. I could feel the distances between these three pointe moved a lot as the chassis flexed.