Cars and catapults not going to plan

The weekend was chock full of frustrations and things that didn’t go quite as planned. On Saturday, I brought the Miata down south to Arthur where I changed the car’s shocks with Tom at his buddy’s shop. Let’s just say that as of right now, the process is not entirely finished. And on Sunday, my design group completed a very basic prototype of our Mechanical Design II project, and the prototype absolutely didn’t work. Rats.

When Friday rolled around, it looked like that I had the weekend all planned out. I retraced my rally route, remeasured the mileages, and made a bunch of adjustments to the rally instructions. Now all I need is someone else to cold run my rally to check for oversights or confusing rally instructions. But the Friday night run was very successful, and I thought that the rest of the weekend would be just as smooth sailing.

On Saturday, I drove the car down to Arthur. Tom, the guy who pretty much got me interested in Miatas in the first place, told me that there was going to be a Miata club meet there at his buddy’s repair shop. Not only that, there were two lifts in the shop and $200k worth of tools that were available to use. So I brought my car, the KYB AGX shocks that were sitting in my bedroom for several months collecting dust, and a set of shock boots and bumpstops that I had shipped during the week. The idea was that we would change the shocks and be done before lunchtime. I got there at 8am and we promptly started a half an hour later.

The problems started right out of the gate. The nuts holding the rear shock mounts to the chassis were so rusty that we couldn’t fit the right socket over them. Instead, we had to shoot each nut with lots and lots of penetrating oil, and then scrape away most of the powdery iron dust with a small screwdriver before we could fit a 14mm socket over them. But we got the nuts off and disconnected both the rear and the front shock mounts.

Wheels came off, and we decided that we would change the rear shocks first. Problem: the bolt that was pinning the shock to the lower A-arm didn’t want to come off at one side of the car. More penetrating oil was used, and with a breaker bar, we finally broke the bolt loose and continued on. We used a four foot pry bar to press the A-arms down and removed each shock and shock mount assembly. New shocks, boots, and the old springs and shock mount were assembled, and the rear shocks were put back in the car.

I remember, at the time, thinking that doing the rear shocks seemed like a complete pain in the ass. As I sit here writing this, however, the rear shocks didn’t seem all that bad. At least not compared to the mess that was changing the front shocks.

The front shocks were a bitch and a half to change. Rust and exposure to the elements that really beat up parts of the Miata’s front suspension. Upon inspection, one of the bushings on a sway bar end link was completely fucked up — the bolt was frozen inside, and dry, cracked rubbing was exploding out of the end link. We needed to disconnect the front sway bar, but the end link refused to cooperate. After fifteen minutes of trying, I decided that the sway bar end link was something that I should probably replace anyway, and gave Tom the go-ahead to just cut the sway bar end link out of the bracket.

Sparks fly everywhere as Tom cuts the off the head of the bolt and the nut. We yank the sway bar out of the bracket. There’s no way to reattach the front sway bar anymore, so for the time being, I’m going to be driving around without one. Sway bars don’t affect the drivability of the car, it just changes the roll rate of different ends of the car. With the front sway bar unattached but the rear sway bar attached, the car will want to push (understeer) during cornering, but I can adjust my driving to that.

The sway bar end link wasn’t the only problem on the front suspension. We had the same problem as we did in the rear: the bolt that pins the shock to the lower control arm didn’t want to move. However, this time, we couldn’t get the bolt out, as it was completely frozen inside the bushing. Again, we had to cut the bolt and used prybars to force the old shock out of the bracket. Fortunately, there was plenty of hardware there in the shop, and we replaced the bolt with an SAE bolt for the time being. I’m going to have to replace this bolt with the appropriate metric bolt in the future.

While working on this shock, we also noticed that the ball joint had a lot of play in it. Oh boy, more fun stuff that needs to be fixed. More importantly, I can’t align the car until the front ball joints are replaced. I was hoping to have the new shocks installed and a performance alignment done before the first autocross of the season, but that’s not going to be possible now.

Not that I’ll have any time next weekend to autocross. Most of the next weekend will be spent on a design project. The other goal during the weekend was to build a prototype and finalize our design, but to make a long story short, the prototype failed spectacularly and we need to go back to the drawing board and figure out what to do now.

You may remember when I talked about building an automatic rubber band gun. After doing some thinking, the group decided that that would be too difficult to build on a budget. The problem lay in the fact that each individual rubber band needs to be stretched in order to fire if we were going to load them into a gun unstretched. And that would be a very formidable task indeed. So we thought up some other design project ideas, and we finally settled on a water balloon launcher. The goal is to launch a 1-5 gallon water balloon a distance of 100-300 feet.

Right after I changed the shocks in the Miata, I drove back to Champaign to a group member’s house and our group spent three hours fabricating a track and cart. The idea was that this cart, sitting on top of a track, would get propelled forward by a tension spring. The cart would hit a stopper and come to a halt, and the water balloon would then go flying out of the car and onto its target. It seemed like a fail-proof idea at the time. We called it quits at dinner time and arranged to meet on Sunday afternoon.

I worked a couple of checkpoints in Jon’s TSD rally early on Sunday afternoon. This was so that I would have a clue as to how to run a checkpoint when I run my rally on April 25. When I was done with my checkpoint duties, I had to run from Odgen back to southwest Champaign. Once I got back in Champaign, I spent another three hours with my team finishing up the rail, cart, and firing mechanism. When we took it to the backyard of the house and attempted to fire the thing, we managed to fling a basketball forward three feet, and a baseball about four feet. Damn. The problem was that all of the force of the spring was being absorbed by the catapult structure instead of being used to fling fun things away. The wooden structure that we had built was slowly coming apart. Not good.

So it looks like the next weekend will be spent trying to come up with a new design and a new prototype. We are leaning towards more traditional methods of flinging things long distances: trebuchets. We might add some fun things to the basic trebuchet to make the design “ours,” perhaps springs somehow, since we have a couple of those already. Anyway, the point is to build whatever we design, and if it does actually work, then I’ll videotape a firing and post it here.

It’s going to be a long road to get to that point, however.