Wednesday, May 17, 2017

The Froot Loops of Safety

Sometimes when idiots like me build cars, they don't get everything right and the cars self destruct. One of the many dangerous ways cars can self destruct is by spitting out a driveshaft. This can happen when a driveshaft or U-joint breaks. 

Sometimes a driveshaft will break because there is too much torque going through the drivetrain. I don't think this engine will make so much torque or the tires will be so sticky that the driveshaft will tear itself in half, but it's possible that the angles aren't just right, or the shortened driveshaft isn't balanced right, or there is a welding issue... any number of things could be wonky. In an attempt to contain the driveshaft should things go haywire, I've installed a driveshaft loop.

NHRA rules require a driveshaft loop on any vehicle that runs the quarter mile quicker than 13.99-seconds while running slicks or quicker than 11.49-seconds on street tires. Since this car isn't built to be a drag racer, it's not likely that either of these situations will happen, but I do want that peace of mind. So like usual, I bought a kit and immediately started slicing and dicing. The rest is pretty self explanatory.

Just the other day I decided it was finally time to reinstall the old Grace-face. She's been without it since May of 2013. That's almost four years exactly. A lot has changed since then. A whole lot. I had barely just started the project. I was still single. I hadn't even met my wife at that point. I hadn't started getting fat yet. There was still a Backyard Steve. Man, I sorta miss Backyard Steve. I'll never forget one time when I came home from work and while chatting with Backyard Steve I noticed two thick scabs on his knee. He could tell that I was staring at his knee so he volunteered an explanation. "Oh yeah, that..." Backyard Steve said "I was doing business with a guy and he tried to cheat me, so I pulled my gun on him. It's a .22 pistol. While I was pulling the gun out I shot myself in the knee." He pointed at the scab above the kneecap "The bullet went in here", he then pointed at the scab below the kneecap "and went out here. It's ok though, I clobbered him with the butt of  my gun. Cracked his skull." Who knows if the story was true, but life was more colorful back then.

May 2013
May 2017
Anyway, Grace has made a lot of progress since those days. I'm not sure if I have, but my wife would at least tell you I wear much nicer shoes than I did in my bachelor days. ¯\_(ツ)_/¯

Monday, May 15, 2017

Boxes of Torque (part dos)

Did you know that dogs and cheetahs can be best friends? Well they can, and I saw it. It has nothing to do with my car, but its cool.

Today in Boxes of Torque (part dos) I make a passenger side torque box. Having already made and installed the driver's side, the passenger side went much quicker. I copied the patterns I had made for the other side and verified that they would fit. Then like Da Vinci with his paintbrush, I set to creating fine art with my angle grinder.

scribing the bend line makes it possible to bend thick sheet metal without a brake

In this shot you can see the S-bend in the tail of the torque box end cap. This tailis drilled and then plug welded to the inside of the lower rocker panel flange.The gap between the tail and the bottom part of the torque box is then filled bya weld 

One of the main attachment points for the torque box is inside the passenger compartment. A slit has to be cut in the floor sot hat the tab can pass through and be welded. I also added a spacer (which can be seen in the middle of the photo) to take up some space between the weld tab and the inner body structure.

With the exception of the welding burns on my arms that are still healing, the second torque box went in very smoothly. This brings us back to the original question. Did the torque boxes change the natural (or resonant) frequency of the subframe / rocker interface, thereby reducing a disconcerting vibration in the body structure when the engine is around 3800 RPM? The short answer is Yes.

I test drove the Falcon briefly and took it through the RPM range a few times. When I hit the problem RPM range, there was still more vibration than at other RPM ranges, but the amplitude was greatly reduced. While is still more than my ideal situation, but I have to remember that this is a shaky old engine in a shaky old car, and that it will likely improve once sound deadening materials and an interior are installed. My initial feeling is that my DIY Falcon torque boxes are doing the job I hoped they would do.

I had a request or two for the patterns of my torque boxes. I'm posting them below with a couple disclaimers. These worked for me. They may not work for you. My car is a 1962 Falcon 4-door sedan and I can't make any claims about any other configurations. I used 3/16 mild steel sheet to build these boxes. I'm sure there are better ways to stiffen a chassis (before you say subframe connectors, I already have subframe connectors) but this has seemed to work for me. Both patterns shown below will work on driver's and passengers, but the main body will have to be bent different directions to be used on different sides. I haven't included a plan for the main body truss. It's a funky quadrilateral that you are just going to have to figure out yourself because you are a big kid now.

Torque box end cap

Torque box main body

I'll be back soon with another episode but until then, stay cool and charge hard.