Chassis - Chapter 2: Page 7 (June 2002)


On the previous page we modified the front axle, so now we needed some stub-axles, brake mounting brackets, and a wishbone to fix it all to the chassis.

Transit stub-axles . .We had already modified the Mk.2 Transit stub-axles (or spindles, if you like), back in early 2001. The Mk.2 Transit ones differ from the more popular (with hot-rodders) Mk.1 axles, in two ways:
1. The later ones have a larger diameter kingpin, so this makes the two types non-interchangeable, and
2. the later ones have the large hexagonal screw-in caps top and bottom, whereas the Mk.1 just has a fat rubber O-ring seal top and bottom.
The earlier ones are a little cleaner and lighter-looking, but not as durable - not usually an issue with hot rods, though. We used the Mk.2's because they came with the axle, and we didn't think the cosmetic side was too big an issue (might do something about the grease nipples, though). Also, being newer, it was going to be easier to get parts like new kingpins from the local auto factors, or even replacement spindles from a scrapyard if necessary. We had made a template of the Alfa Romeo front stub-axles and checked the Transit ones had sufficient material before buying the axle in the first place (a comparison is shown in the photo - the Transit is on the left). Not too much material had to be removed to allow the Alfa hubs to fit, and luckily they JUST fitted in our little lathe. A generous radius was left at the root of the new bearing and seal faces to prevent stress risers forming.

. . caliper mounting brackets . .In our, by now familiar, fashion, we ended up making two sets of brake caliper mounting brackets for the spindles! The first set were designed along the lines of aftermarket adapters used for mounting GM calipers on early Ford ones, and use the minimum amount of material to do the job.
If you look at the top left view with the rusty calpier mounted, you may see the problem: although nice and compact there is nowhere to bolt a top steering arm on! We hadn't at that time decided on what steering would be used, but were leaning towards cross-steering, which doesn't need an upper arm. However, when we had finished working out the front axle wishbone, we realised that there wouldn't be room to clear a cross-steer assembly, so decided on traditional side-steering.
Out came the 3/8" bright steel flat stock, and we set to drilling and sawing, filing and welding, until we had a nice pair of LH and RH brackets that bolted straight onto the spindles. The short length of tube is a socket for the planned front cycle-fender mounting stay, and the extra hole at the bottom of the bracket is to fix the rear stay. The three holes with screws visible are the ones used to bolt it to the spindle, and are tapped 7/16"-UNF. The top two holes are for the steering arm - the right-hand bracket is shown, but the left one is a mirror image, so we could still choose left or right-hand drive.

Now we needed to mount the axle to the chassis, but how?
Traditional-style hairpin radius rods would have looked good, but they are not recommended for tube axles because they impose a twisting force on the axle - tube axles do not twist, so everything is under stress during road use, which will lead to failure of the weakest part sooner or later.
We could have used a parallel four-bar set-up, which doesn't induce the same stress in tubes, but felt this was too modern a design for the style of rod we were aiming for. Although introduction of parallel four-bars is often attributed to Pete & Jakes Hot Rod Parts in the early 1970's, individuals had used four-bars long before then - there is no doubt P&J's helped in their widespread adoption, however. So that left the way Henry Ford mounted his axles: the single-point mounting wishbone. This allowed relatively unlimited, stress-free movement of the axle over all sorts of road surfaces.

. . and wishbone.We obviously knew the width of the wishbone at the axle, and the length was dictated by the mounts on the chassis, below the gearbox. We machined some 1/2" steel flat to make the front mounting plates, then bent a length of 7/8" diameter, thick wall CDS, into a loop for the main wishbone. Two more pieces were bent and cut to create the top bars of the wishbone, then it was all TIG-welded together. We had initially thought of filling in the sides between the upper and lower tubes, to look like original wishbones, but decided that we would leave them open for now, with just a small brace welded in each side. A piece of 1" CDS was threaded to take a 3/4"-UNF rose joint, then welded on at the back.
After a coat of satin black paint, it was ready to use: stress-free location for our front axle. On the down-side, there isn't much room to easily install a cross-steer set-up, and there is only one adjustment axis - fore and aft - but this shouldn't be a problem. And we still have the option of splitting the wishbone if we want to, or, from our previous track record, changing it for something completely different!

Now we can install the front end in the chassis, we need to get on with the rear axle.