#1: Spherical Bearing A-arm Pivots
The first is Allen's '90 Miata with a turbo BP built for the Super Street Modified (SSM) class in SCCA Solo. I've had the privilege of driving this car a few times in various states of tune, and it's really awesome. It's not quite to the extent of the crazy rules in SSM, but it's getting there.
So my job on this one is to swap the rubber bushings in the front lower control arms out for spherical bearings. This is similar to the job done on the GTI rally car in an earlier post, in that it requires welding in a carrier to hold in a spherical bearing that is then retained by a snapring. Allen actually has some polyurethane bushings for these arms, but stiffer bushings have a lot of potential for bind when the pivot axes aren't perfectly co-linear, which means that every time you change the alignment, you effectively alter the wheel rate. Bushings are also still a bit squishier than sphericals, so the benefit is two-fold: increase joint stiffness and reduce suspension bind. That increase in joint stiffness means less camber loss under lateral load and also a reduction in compliance toe change which are both things designed into the suspension to keep people from getting themselves into trouble. However, this car has been re-purposed exclusively to get into trouble so that is all counter-productive.
Allen requested the use of some fancy seals to keep grit out of the sphericals, so he sent me some detailed project requirements:
This is actually some really awesome MS Paint CAD
I put it in actual CAD because that's how I think:
Really, this is totally redundant though
As with any other project that I write about, I turned the parts out on the lathe:
Here's the finished bearing carrier:
And then I welded them into the arm and stuffed in the spacers that I made to retain the seal and space the joint up to the same width as the factory bushings and reduce the bearing bore to the factory bolt diameter:
Blast, paint, assemble...and there you have some bind-free, high-stiffness A-arm pivots!
#2: Coolant Expansion Tank
The next Miata is Curt's ride, which also started out as a turbocharged SSM car. Curt exploded his transmission at an autocross last summer though, and that was enough to push him down the tried and true drop-a-giant-V8-in-it path. He's got a really in-depth build going on, and it is impeccably documented on his website here.
Curt first picked up a welder for this project, and he has come an impressively long way in a short time. But he has no way to weld aluminum, so I offered to fabricate a custom coolant tank for him. The coolant expansion tank is exactly what it sounds like; it's a place where the coolant can expand as it gets hot and it's at the top of the system so it also serves as an air bleed. It's basically a box with some fittings and a cap. This one has a sight glass too as an easy way to check coolant level.
Curt made some nice CAD for me and sent me some drawings:
Again, I built my own CAD model because it helps me think, and I changed a couple dimensions to give me some clearance to weld:
There's not much to this except to cut all the pieces out of aluminum and weld them together. I used the lathe to make a huge fitting to thread the sight glass into, but the rest of it was just taking the fittings that Curt sent me and welding them to a box.
Great practice welding aluminum for me. I could use some more, but the part seems sound. And here it is sitting front and center in his engine bay:
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