As reported in Part 1, the chassis that came with the car, i.e. the one underneath it, turned out to be unserviceable in so many ways that a replacement was the only practical option and thankfully a suitable chassis became available from an American TR4a – a non-IRS car.
The first picture shows the “repairs” to one of the front lower fulcrum brackets and illustrates one of the reasons the original chassis was condemned.
However, before making the decision, I had also laid it out on a large sheet of brown paper on the garage floor and using a plumb line and the reference measurements given in the workshop manual I could check the alignment of key datum points. The results were reason for write off, number two.
My replacement rolling chassis was from a leaf sprung 4A meaning that I needed the front ‘bridge’ as this is only fitted to IRS cars. Thankfully, this was perhaps the only piece of the original chassis that could be, and was, worth salvaging. I cut it off and sent it away for shot blasting after which it was treated to a lovely cost of bright yellow primer – all I had to hand at the time.
The other required change was to remove the differential bumpstop for the live axle.
Bizarrely, the only real corrosion on the replacement chassis was the LHS central floor mounting bracket, so this too was cut from the original chassis and subsequently used on the replacement.
The workshop manual includes many measurement points for the chassis, but very few for the differential mountings. I thought this through many times and settled that I could establish the distances for the front and rear locating pins and as the rear bridge was in-situ, that would be my starting point to locate the front bridge. I cut a piece of plywood with four holes for the differential pins, but was not convinced that it would be sufficiently accurate to ensure the diff ran true and correctly aligned. “What would happen when I came to bolt the diff into place later in the build?”
Then in a ‘Eureka Moment’, I thought why not just bolt the diff to the mountings and then weld it up in place? That way, I know the mounts will be in the right place, so that’s what I did.
All four pins have received the standard boxing reinforcement and the front fulcrum brackets will also be getting strengthening braces before painting the whole lot in chassis black.
One final note on what was found inside the chassis. Every time I rolled the chassis over it was accompanied by loud rattling from within. Oh dear, I thought, this sounds like it’s falling apart from the inside. However, a combination of pressure washer, compressed air and vacuum cleaner extracted around half a pound of Pecan Nut shells together with the remains of some sort of insect nest. All cleaned out, the chassis now lies silent.
Next time, back to the bodyshell.