Daily Archives: October 8, 2020

OK getting down to brass tacks on this steering business

First, an etymology of the phrase “Getting down to Brass Tacks” because I know it and I think it will add to the conversation about the steering. The origin of the phrase relates to custom saddles for horses and cowboys, and literally refers to the size and number of the brass tacks used to secure the final seating surface to the frame of the saddle. This was important because too few or too small of tacks would cause the saddle to fall apart, and because the polished brass tacks were a decorative touch and too many was considered to be low-class, or <i>nouveau-riche</i>. And that should be in italics but I have to switch back and forth between editors so fvque it.

Anyway, this part of the design is very detail-oriented, in that the same parts from different suppliers will require different fitting because while they might be the same internally (spline count and/or shaft diameters) outside they are very different. Like about a quarter-inch different in outside diameter between basically the same U-joints from different manufacturers means some will clear the inside of the bellypan without relief dimples and some will require about an eighth of an inch or so relief dimple to not foul the U-joints when the steering wheel is turned. So I have to do a lot of catalog and website browsing to find the outside diameter of the various U-joints, so I can pick the ones that won’t require extra work on the bellypan.

Actually there is only one place where the outside size of the U-joints is at all important, the place where the steering shaft goes under the radiator, between the frame rails, and above the inside of the bellypan. The current plan is running a 3/4″ shaft under the radiator in the 1 1/2″ gap caused by the radiator having to sit on top if the bottom frame rails, and tucking that shaft up as close to the radiator as possible. I can get bearings that can be mounted so the shaft just barely clears the bottom of the radiator mount, meaning the U-joints have 1.125″ radius clearance without having to dimple the bellypan. Most of the U-joints I’m looking at will clear that with no problem, but there are some that don’t and I have to make sure I don’t get those. So I have to mark the ones that I know will fit and then cross them against other considerations, like how strong they are, and how much flex they have. Price is also a consideration, but there isn’t much leeway there. They pretty much cost what they cost, and there isn’t much difference between suppliers.

Anywho I have also figured out what to do with some of the leftover heavy angle stock: the panhard rod (or track bar, the two are interchangeable) needs a sturdy mount on both ends, and the quarter-inch thick stock will be perfect for that, being practically inflexible for the size needed for that bracket, no deflection at all as short as they are. And because right angles and flat surfaces, it’s practically self-jigging.

And I don’t know if I mentioned it explicitly before but because of the thickness required to prevent flex in the steering arm, the part is thick enough to be threaded for secure connection to the rest of the car. No extra nuts required, but I will use a safety nut on the bolt through the heim joint at the end of the drag link, because that bolt will be hanging down and could fall out of it wasn’t safetied somehow, which could cause a total loss of steering control. I don’t think saying that would be bad is any overstatement. The safety nut in this application would be equal to a double nut safety, as the threaded steering arm would function as the first nut.

And I’m getting a notification from my computer that my OS wants a shutdown to update, I’m starting to glaze over and try to faceplant into my keyboard because trying to think about something on-topic to write about. So this looks like a good time and place to stop writing this and publish and reboot.