Tag Archives: steering limits

Still thinking, but more specifically

Relax, I’m thinking about the steering on the Sprint-T, not doomsday devices. Besides doomsday devices are a one and done thing, and unlike most mad scientists (we actually prefer the term aggravated engineers, thank’ewverra’much) I actually thought ahead and know if I blow up the world I lose my place to sleep at night, lacking a means of space travel. Besides have you checked the price of plutonium lately? No, thanks, I’m out of the doomsday device business.

So, back to the main topic, I’m pricing the specialty metal to make the steering arm that makes the steering quicker, and it’s super expensive for what I need. I mean in absolute terms it’s not much, it’s just I have to buy 4 linear feet of stock to make a part that will be just over 6″ long finished. And that 4 feet of stock costs $33, so most of the stock is wasted unless I find something else that needs to be that strong.

Cutting the stock to the length I need for the steering arm, henceforth to be named “the part” in this doc, I need to cut about 8″ to make the part. The part needs to have an arm that is 33/16” from the spindle axis to center of the hole for the drag link, but there is the attachment hole to the spindle on the other side of the axis from the drag link hole to also account for, plus the gussets needed to prevent flex in the part because the load will be off-axis no matter how I bolt up the drag link to the part. And dropping the drag link down to clear the suspension links will make the leverage off-axis greater causing more flex in the system. Therefore the part needs to be made from heavy stock, and gusseted, to keep the flex as low as possible.

I don’t think there will be any detectable flex in normal driving, but autocross and SCCA Solo Racing are not “normal” and put the steering under about as high a stress as you can get without going off-pavement or banging curbs. And now that I think of it there is a slight possibility of banging an actual concrete vertical-faced curb doing that, so I guess that means another gusset. The plan is now to have a gusset on either side of the bolts holding the part to the spindle, because curbs. Anyway, this stock is right at the limits of my welding equipment and cutting tools, so if I need to use heavier stock to make this part I will have to farm the part out to a professional with better equipment.

Just a passing note, I made the suggestion on Twitter that if @realDonaldTrump refuses to vacate the White House as he claims he will, then he should be treated like he says protestors against police brutality should be treated, but obviously in fewer characters because: Twitter. I’m now locked out of reading Twitter until I apologize by taking the tweet down, which obviously I will do as soon as Agent Orange apologizes for saying the same thing about protestors or when pigs fly. I don’t care, either one is equally likely. I don’t really need Twitter, it was just something to kill time with.

And with that act of defiance I’ma put this thing to bed.

It’s finally here!

And by “It” I mean the steering box that has been on backorder since early June because of the Stupid Virus. I’m changing the name because the existence of COVID19 seems to make people stupid, besides what it did to my employer and the GOP. Anywho, this is a picture of it below.
Steering box, remotes and bumpersticker for scale

I’m keeping it in the plastic bag for the nonce, having learned my lesson about surface corrosion from the spindles I bought a few years ago. I may be slow, but I’m not stupid. And FYI that thing is HEAVY! no, it’s HEAVY! That tiny chunk of metal has to be over 15 pounds (6.8 Kg) which brings up the question of why they still use iron in the main casting? Probably because steel or iron is cheaper than aluminum, but then the question is why it isn’t an option since this is a repop for a part that has been out of production for five decades, the Vega stopping its run in 1977, and presumably GM stopping production of replacement parts shortly after.

And it turns out that it was fortunate I bought the Pitman arm for the 5/8” heim joint, because this was shipped with the arm for the Ford taper tie rod end. There is something I can use the extra Pitman arm for, by placing the two arms side by side with the ends reversed I can get an fairly accurate center-to-center distance to use in making the steering arm to mount on the spindle. I mentioned this in a post a while back, this post to be precise, that I can use the steering arm to change effective steering ratio without adding any weight. In the post I was thinking that since I was using the steering arm at the spindle instead of a steering quickener the difference between the arm and the quickener box was the amount of weight I was saving, but in reality the arm at the spindle has to be there regardless of what I do at the box, so I save the entire weight of the steering quickener when I go with the shortened steering arm on the spindle, plus the weight loss of using a shorter arm instead of the one normally used. I think what I was thinking about was there’s no need to use a steering arm at the spindle because there is an extended bolt to attach the drag link on the arms I already have, except that unless I move the steering box further behind the axle the drag link will hit the tie rod, and I don’t have that problem with the steering arm for the drag link mounted to the lower holes of the spindle and the steering arms for the tie rod mounted to the upper holes of the spindles, especially if I use the extended bolt on the drag link arm to drop the drag link even further from the suspension links.

Now I just need to figure out the load path from the steering box mount that was in the kit with the box, to the rest of the frame. For the application the kit was made for the box mount welds directly to the frame rail of a ’23-34 Ford. This is going to be a bit more complicated as the frame rails are either over a foot above the box or several inches below it, and beyond just holding the box in a certain place in space relative to the frame and axle there are significant forces that will be applied to the mount, off axis forces at that. That means either the mount will be very heavy and apply torsion to the frame tube, or the mount will have to be braced from the other side of the frame. Since there’s nothing in the way of the mount going to the other side of the frame I’m going with that unless and until something else has to be put in the space between the radiator and the front axle. The radiator will be mounted slightly to the right to make the nose symmetrical and keep everything under cover, but since the tie rod and the pitman arm are both going to have to extend beyond the side of the nose it’s actually a moot point. The steering will come out of the left side of the nose because it has to, the Pitman arm will swing to the left further than the confines of the nose at full lock anyway, even the reduced amount of lock with the shorter steering arm at the spindle. The fun part now is how do I adjust the internal stops in the box to prevent the steering linkage from getting damaged by over travel caused by the steering box? Without internal stops the drag link could be overcentered and the car be unable to return to center when the steering wheel is turned the other way. Or I could use a stop on the axle that hits something on the spindle to prevent turning far enough to the right get to that point. Turning to the left the drag link hits the back of the spindle before getting to the over center point, I could use a stop on the axle that stops the spindle at the same point of rotation in the opposite direction. Hitting those stops would generate substantial forces on the steering mount, getting back to the original topic of internal stops in the steering box and the steering box mount. There is also the point that at full lock the tires will be almost perpendicular to the axis of the car. This would be useful for moving the front of the car sideways when not running, but I don’t see any practical application for this much steering angle.

And here we see yet another example of how I think, wandering here there and everywhere as I solve a problem. I’m not sure which part of my mental problems this typifies, but I know this isn’t my PTSD or depression at work, the only mental illnesses I have that I can’t blame this thinking style on. Maybe my ADHD, yes this is undoubtedly what happens when genius meets butterflies and squirrels. And since I just noticed my word count has tripped the 1K mark for this post I think this is a good spot to put this post to bed.