Alfa Romeo TZ1: Ongoing chassis 2

As expected, the forward chassis structure fought me all the way. The coil turned out to be the final bit in the way, after I had cleared away the lower radiator hoses for oil and water. These will all go back on afterwards.

As with the Ferrari 250 LM, the 'ball joints' for the front suspension turned out to be fairly useless. I once again resorted to drilling and tapping for #00-90 screws to attach the hub to the A-arms. I have come across two different recommendations for tap drill size for screws this size, and I picked the smaller one on the basis that, first, I am threading into a soft material, and second, that it is a lot easier to drill a hole bigger than to make it smaller. So out came the #65 drill bit (0.035"); the other reference calls for a #62 drill, which is only 0.003" bigger, but better safe than sorry. A bit of a heart-stopper, since a screw-up (pun intended) would be potentially catastrophic, but it all worked out. Details follow.

Drilling through the A-arms. I tried to keep it all straight  by drilling through both arms at the same time, but these things are pretty flexible and I was only partly successful.



Drilling into the upright. I had to cut off the little pins, still present on the second upright, then mark the hole properly to keep it all centered. The upright isn't a lot bigger than the drill.



Two screws inserted through the A-arms into the upright. The only screws I have on hand are too long, and it wasn't possible to drill clean through the hub as with the Ferrari, so I threaded two screws in through the A-arm and into the hub as far as they would go, then snipped the excess off and sealed it all up with a drop of CA glue.



The finished product looks good unless you are magnifying it, as is the case here; some touch-up semi-gloss black paint will be needed. The springs are nice nickel-steel bits that look good.



With the front hubs one, I was able to get the chassis up on its wheels for the first time.



The chassis sits square on its four wheels, which is great, but the camber, toe-in and track of some of the wheels is still off. In particular the rear wheels don't fit under the rear fenders, so the body sits a bit high. This can be cured with the right amount of drilling into the hubs.




An important lesson here: a complete set of number drills, at the very least from #76 (0.020", 0.5 mm) to #61 (0.039", 1 mm) is critical. This kit also has 0.8 mm rod so you'll use your #67 bit (0.032") as well.



Next: lots of finicky little details to finalise the chassis before moving on to the interior, and the decision as to whether to attach the floor pan permanently and obscure all this nice work. Nonetheless progress is being made! So stay tuned.