Restoration of TC8485 – Part 2

In issue 31 (August 2015) I reported on the early days of my restoration of TC8485. To recap, when I bought the car it was in need of a complete frame up restoration and in my first instalment, I covered stripping the car down and restoring and repainting many of the black parts that bolt to the chassis (including both the front and rear leaf springs). I said that progress would be slow for the next few months due to other commitments but that I wanted to get to a rolling chassis by the end of the year.

In this instalment, I cover restoring and rebuilding the chassis, hubs and leaf springs to end up with a rolling chassis. As it turned out, it took longer than I anticipated, partially due to some technical issues that I cover below, but also due to a head injury that I sustained when I slipped on some ice whilst out running that put me out of action for a while (it turns out that exercise is bad for you after all!).

The chassis

I started to strip the chassis with chemical paint remover but then realised it was very messy, difficult and altogether a bad idea, so I had it grit blasted along with the rear axle (total cost £70 delivered). I thought about having it powder coated but decided to go for originality and painted it instead. I’m pleased with the result.

Before I painted it, I decided to take some accurate measurements to ensure that the chassis was straight. The key measurements are the diagonals from the front edge of one of the rails to the rear most body tub out-rigger on the other. The diagonals should be within 1/8” of each other and mine were about ¼”. I don’t know whether I could have lived with that, but pride dictated that I needed to do something about it.

To get a better picture of what was going on I put masking tape along both rails, marked it at 4” intervals, measured the gap between opposite markings and then plotted the differences on graph paper at an exaggerated scale. This revealed a sort of S-shaped distortion in one of the rails whilst the other was dead straight (you could see the difference by sighting along each rail).

As tolerance on the key diagonal was marginal, I decided to have a go at straightening it myself. This was easier than I expected using blocks of wood and a jack at strategic locations. I used a long block of wood to spread the load on the rail that I didn’t want to move and a shorter one to create more of a point load on the one that I did. Much to my surprise, I quite quickly managed to get the diagonals back within tolerance. You do however need to slightly over-bend the rail to allow for bounce back when you release the jack.

Rear Springs

As reported last time, I had disassembled the spring leafs, sanded them down and painted them with POR15. These were reassembled with a mix of silicone grease and graphite between each leaf. It was relatively easy to bend the clamps back around the stacks of leafs, but it did damage the paint, so cosmetic repairs had to be made. A new set of poly bushes was purchased from John James and all four sets of springs went back on the chassis without a problem (or so I thought).

Ed’s note: Incorrect axle location – the result of a faulty batch of rear springs badly made some years ago (see text). The dimension, centre to centre of the chassis spring mounting points, is 36 inches. The loaded length of the rear spring should be 36.5 inches, and the pivot point for the axle centre 18.0 inches from the centre of the front (metalastic) bush.

I bolted the rear axle back onto the springs and then attempted to fit the rebound hoops. I couldn’t get these on without the front edge of the axle pressing against the hoops, as can be seen in the photo below. This was clearly not right and careful measurement, plus some head scratching, revealed that the dimple in the main leaf of each spring set (i.e. the longest one, with the eye holes) was too far forward by about 1”. This explains why the rebound hoops were in the back of the car when I bought it! This might seem like a small discrepancy, but it is significant when you remember that the main leaf locates the position of all of the others as well as the position of the rear wheels in the arches. Rather than buying a whole new set of rear leaf springs, Brost Forge (located between Kings Cross Railway Station and Caledonian Road Tube Station, London) made me two new main leafs for a very reasonable price, which were collected on a business trip to London.

Compressing the springs i.e. flattening them so that they are drawn upwards, in order to be able to bolt up the axle.

Incidentally, the springs need to be compressed in order to bolt on the rear axle as the axle presses hard against the chassis until the full weight of the complete car is on its wheels.   I had previously made a trellis out of spare wood to rest the chassis on whilst I was working on it. This was just wide enough to bridge between the springs, and by resting a bit of steel box section across the top of the chassis, with a jack sitting on top of that, and the whole lot tied together with a load strap, I was able to compress the springs to allow the axle to be bolted on with ease.

Hubs

The next stage was to restore the hubs. Whilst I had the hubs apart I decided that it would be prudent to replace all of the bearings, even though the old ones appeared to be in reasonable condition. It’s a simple job whilst the car is in pieces and at relatively low cost. At first I struggled to get the pair of bearings out of each front hub as I tried to press them out from one end of the hub only. On reflection, it’s obvious that they cannot come out that way as it would mean that the wheels would fall off in use! The correct way to get them out is to first of all remove the smaller bearing by passing a suitably sized drift (I used a socket on an extension bar) through the larger bearing and tap/press it out, then press the larger bearing out by using a larger drift from the small bearing side. This is necessary because both bearings press against lips in the hub which prevent them from pushing all the way through. With the new bearings pressed in, I got the front of the car rebuilt without any further problems.

Interestingly, the front hub backing plates on my car had been heavily modified by a previous owner who, I believe, lived in California, to improve cooling. I thought about replacing these in order to go back to factory originality, but, in the end, I decided to paint and keep them as they are part of the history of the car – so my car is now ready for those long, hot, British summers that we always get (it’s good to be optimistic!).

Ever seen one of these before? Lightened front backplate with cooling scoop!

When reassembling the rear hubs, I decided to forsake originality on this occasion and use the improved design combined hub nut and oil seal in order to prevent the known problem of differential oil leaking onto the rear brake shoes. I also decided to apply the improvement described in ‘TC’s Forever’ designed to reduce stress on the half shafts. Here, the idea is to ensure that the outer edge of bearing is pinched between the wheel hub and the bearing carrier when assembled in order to prevent play. In some cars, the extension flange on the hub is not long enough to touch the bearing. Careful measurement of the hub and bearing carriers on my car showed that, allowing for the hub to carrier sealant or gasket, I needed a 0.3mm shim on each hub to ensure pinch up. If anyone else is intending to use this approach, then The Bearing Company) supplies a wide range of shim diameters and thicknesses. The 80mm OD ones are perfect for this job.

Improved bearing carrier securing arrangement with inbuilt oil seal.

Differential

Inspection of the differential revealed that it had already been fully restored. There was no oil in the rear axle housing, the differential gears were covered with a film of fresh oil that had clearly never been used in anger, and the gear teeth looked unworn.   However, rather than just trusting that it had been done properly, I decided to check that the backlash had been set correctly. The TC Instruction Manual (‘the Brown Book’) helpfully states that the correct amount of backlash between the crown wheel and the pinion should be between 0.007” and 0.010”. However, with the differential assembled it’s not actually possible to get any sort of measuring device between the teeth. I solved this by clamping the prop shaft end so that it couldn’t move and then placed a small, soft faced, G-clamp on the crown wheel to act as a reference point and end stop. By placing a digital vernier caliper between the G-clamp and the diff housing it was possible to measure accurately, and repeatedly, the amount of backlash by rocking the crown wheel backwards and forwards.

Adjustment of the gap is then relatively easy to do by adjusting the two large nuts on the outside of the differential bearing races. It should be noted however that the adjusting nuts should be locked in position with the correct pre-load before taking another measurement. Finally, the crown wheel teeth were painted with a small amount of engineer’s blue to check the meshing of the gears. I found that only coating half of the circle of crown wheel teeth works best as its easier to see the tooth mating markings when the pinion becomes coated in the blue and then leaves markings on the clean half of the crown wheel. The end result of these adjustments was a fairly close approximation to the drawing in ‘Blower’.   Whilst the differential was off the car, I also took the opportunity to send the pinion cap to Roger Furneaux so that the improved lip seal could be installed.

Finally, the dampers/shock absorbers were tested off the car to make sure that they were working properly. The front ones were fine and only needed a rub down and re-spray before being put back on the car, but the rear ones were not working properly and had to be refurbished by Raj Patel at Recon and Return, Leicester.

Next Steps

The immediate next step is to sort out the braking system and the next big step in my restoration is to rebuild the body tub. Due to lack of space, this is going to have to be done on the restored chassis, rather than on a jig, so I’ll need to be careful not to damage the work that I’ve done so far. The advantage is that I now have a rolling chassis so I can work on it outside in, hopefully, the sunny summer weather. I’ll report back again at the end of these stages.

Steve Wallace
July 2016

Ed’s note: Talking of Steve’s “S-shaped distortion in one of the rails” of his chassis, how about this one for size? It was sent to me by Brian Murphy in Melbourne. Brian said that this chassis was advertised as “TC chassis for sale … but has had a hit”………. Some “hit”!

Thought to be TC0284, it has been successfully straightened and in the last pic I saw, it had Brian’s Q-type replica body mounted on it as a temporary measure whilst chassis TA1475 is being restored.

DISCLAIMER BY THE EDITOR

‘Totally T-Type 2’ is produced totally on a voluntary basis and is available on the website www.ttypes.org on a totally FREE basis. Its primary purpose is to help T-Type owners through articles of a technical nature and point them in the direction of recommended service and spares suppliers.

One thought on “Restoration of TC8485 – Part 2

  1. Geoff Piddington says:

    The photo showing the front ventilated brake backplate also gives a view of the rear of the stub axle. From appearances, it looks like an original. If so, I strongly you suggest that it be crack tested or replaced before use.

    Re lubricating the spring leaves. A mixture of powdered graphite (any foundry will supply it by the kilo for a fraction of the retail cost)an equal amount of shellac flakes (hardware stores stock it) and methylated spirits mixed to the viscosity of house paint, will after application to the working faces of the spring, dry very quickly to a hard dry and long wearing surface ideal for springs and the inner surface of wheel rims.

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