Rear bulkhead and floor supports

This is the final piece of fabrication work that involves welding directly to the chassis. I am trying to keep the overall weight down as the engine power is not going to be great for the time being. No doubt I will get around to doing something about that but not in the near future.

The rear fire wall is constructed out of 1" x 1.6mm ERW square tubing. I will do the corner weights soon and see what it all comes to.

The requirements are 1) A place to attach the seat belts 2) A place to attach the seats. 3) Support for the wooden floor.

Here is an Index page for the build

Steering arm and linkage

I discovered the steering arm and linkage I acquired appeared to be from another model and did not fit my A7. The steering arm however was not that far away from what was needed but  needed a 90 degree twist at the end. It also needed an adapter to connect to the upright. I had a look at the standard A7 ball ends and I am not that impressed with the design such that I decided to use  a pair of M10 ball joints from McGill Motor Spport and a CDS 22mm bar in between them.

The design for the adapter is shown below, it is designed to take my now twisted steering arm and connect it to the offside upright forging hole.



The 10mm had to be reduced to 5 mm to make space for the brake cable.

Adapter in place

Steering arm in place

Subsequent measurements show only two turns lock to lock.

Update 4th Aug 21

This modification is now replaced with updated Hilman Imp steering conversion.

Here is an Index page for the build

Rear radius rods

The Austin Seven rear suspension suffers from bending sideways on corners. This results in excessive overseer. If you view (http://austin7special.blogspot.co.uk/2015/07/considering-rear-chassis-modifications.html) I have now considered all the options and I have decided on the A frame implementation.

On the chassis part I have decided to make a ball joint similar to the front tie bars. The first job is to make a ball on the lathe to mirror the ball on the torque tube. Obviously the ball on the left is rear facing and has a 10mm hole to take the radius rods.

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 The tie rods are manufactured from 22mm CDS tube with custom turned ends. The chassis ends are simple cups to take the ball shaped A7 joints and the other end is a 30mm bar turned out to an interference fit of the Metalastic bush. The metalastic bushes are std10mm x 23mm x 28mm bushes off ebay probably used for a quad bike or the like.

Tie rods in place

Tie rods

Clevis plates added to diff casing

Update 4th Aug 21

This  subsequently proved to be a big mistake and updated with a Panhard Rod see further posting. The old mountings on the diff were ground off.

Here is an Index page for the build

Throttle pedal

I have been looking at various A7 specials and I must say the pedal arrangement has less than generous space for your feet. I am used to  small pedal boxes being a kit car enthusiast but A7 specials are even more of a challenge. To get a more usable pedal box on the rhsI decided to put a power bulge next to the throttle. Browsing the ebay adds for throttle pedals I found one for an Austin Mini from the 60's that looked interesting so I took a punt. I had to bend the shape a bit with extreme heat and shorthen it a bit but nothing drastic.  Here is what I came up with and I must say I am very pleased with the result.



Here is an Index page for the build


Custom tie bars

The front suspension has tie bars from the chassis (centre point ) to the stub axel mountings. These tie bars prevent the geometry changing under load. The suspension was manufactured by Bowden in the 50-60's as such the track width is greater than standard A7. I could not find any such wider tie bars on the usual s/h sources so I had to fabricate some. The suspension end had to be heated to yellow and bent. The tie bar tubing was cut out of  25mm x 3mm thick CDS. The cup ends were turned out of 38mm bright bar and the axel ends out 25mm bar as pre attached diagram. After turning the 43mm long section it was grooved and bent to the correct angle. The groove is necessary to keep the bend angle tight, I welded it up afterwards.



Chassis end

Upright end



The finished tie bar vs original

 

To secure the tie bar end I used a full nut and  one half nut made out of an old castle nut but with the same thread and a larger spanner size cut down on the lathe. The half nut is on the inside. There are two thrust washers cut out of 30mm bar 3mm thick. The thread by the way is a 5/16 x 16tpi UNC thread form available from Tracy Tools.



Update 4th Aug 21

The tie bars were subsequently modified to have jack screws to adjust their length as part of a Rack and pinion upgrade.

Here is an Index page for the build

Brakes

The brakes have been a bit of a trial for me, there are so many permutations even if you stay with the original mechanical systems. My system is a mixture of Bowden mechanical at the front and an early A7 mechanical system at the back. The brake drums are of two different types. The front brake drums don't fit the back and vice versa. The front brake shoes (3off) were missing and as far as I can ascertain are unobtainable. I decided to get a set of eight s/h alloy 1 1/4" and  move on  from that point and make everything fit.

Rear brakes

The cams at the back were not even running in a brass bearings, just holes in the forging and seized at that. As these were badly worn these had to be drilled and bushed and reamed to size. The cams that were initially supplied, were the wrong type and had to be changed again for an earlier type. This of course results in another strip down of the hub carrier.

Rear brakes connected up and working

Front brakes

The front brakes were another  challenge, requiring the 1) fabrication of a new back plate. The standard A7 oem back plate had to be cut away to accommodate the Bowden forging protrusions and mounted on the back to make room for the non standard brake drums.  I have no idea what the drums are off but they do not fit the Bowden assembly ideally.  2) The  pivot point for the brake shoes had to be moved to accommodate the smaller A7 alloy shoes. 3) I had to increase the internal contact width slightly and fit a 2mm spacer on the wheel studs to make them fit with the 1 1/4" shoes. The drums were also well off the concentric being about a mm of wobble. This had the effect of locking up the brakes. 4) The drums were trued up on the lathe.  The front brakes, now at least, go together and look as if they may actually stop the car.

 



Front drums fit after truing up on lathe

Hand/foot brake

The handbrake started out devoid of modifications other than shortening the leaver to allow it to reside under the bulkhead. I tried the standard parts for the Bowden cables operating the front brakes but was hugely disappointed by the lack of any fine adjustment. I can see the rear bakes have this problem but the front brakes are somewhat more critical as 80% of the effectiveness comes from them. I decided to modify the balance bar and add a full length cable from an Austin Maxi.



Modified balance bar to front brakes

Previous adjustment

Previous balance bar arangement

Update 4th Aug 21

I have subsequently updated the brakes to hydraulic twin leading shoe at the front and single leading shoe at the rear, the brake liners have also been updated to Mintex high performance racing material.

Here is an Index page for the build