Thursday, April 27, 2017

Boxes of Torque

If you are weary traveler, searching the corners of the internet trying to find some information on Ford Falcon torque boxes, you are in the right place. Welcome to Ironhydroxide, a place where we tell stories about building an old econobox Falcon into the kind of high performance car it was never intended to be. If you are a regular, you already know this and you are probably just here for the gifs and youtube links.

What is a torque box? This is a question many a classic Ford owner has asked himself and most have not received a satisfactory answer. Today that is about to change.

In the late 1950s, The Big Three realized that they were about to get their butts whooped by the same group of schnitzel-eaters that they had whooped only 15 years earlier. Volkswagen, the brainchild of everyone's favorite fascist had grown powerful and was going for round two in world domination. The Beetle, known to the Germans as the Kรคfer, was steadily marching across the globe and even into the driveways of red-blooded Americans. Robert McNamara, who went on to become John F Kennedy's Secretary of Defense, recognized this creeping threat to the security of the good people of America Ford Motor Company. In response, he did something drastic and led Ford into battle with what was the smallest car they had built since the 1930s. This car was the Falcon and it was a massive success. It was cheap to build because it was a unibody construction, meaning that they no longer had to manufacture a frame and body.   After the first two years of production Ford had sold one million Falcons. For perspective, Toyota has sold about 400,000 Camrys each year for the past decade or so.

Now that the Americans were on the offensive they could now start to do what Americans do, that is, shove V8s into everything. This was 1963 and America couldn't wait for the Mustang to give them a little V8 car. America needed it now, and the good engineers at Ford obliged by shoving a V8 into the Falcon. These same engineers soon found that the unibody of the Falcon had the structural rigidity of mom's spaghetti and that became a real problem once had to deal with more than 100 horsepower. The solution to this problem was the Torque Box.

So this brings us full circle. What exactly is this miracle of engineering, the torque box? In the diagram below, you can see some of the main load bearing components of a unibody structure. The engine and supsension mount to the front subframe. Forces applied to by the engine or suspension on the body go initially into the front subframe. The red arrows shows the forces that would be applied by driving over a bump. A torque box, shown in pink, creates resistance to the rotation of the front subframe by tying it together with the rocker panel.

Ford unibody torque box diagram
Mustang passenger side torque box
While the torque box found its way into Falcons, Mustangs, Fairlanes, and just about every other unibody Ford, that doesn't mean they all had them. My car was definitely in the "no torque box" camp. (WARNING: ENGINEERING JARGON AHEAD) This means that all the twisting forces  and vibration at the back of the front subframe are being transmitted through the floor and firewall of the car. Long time readers may remember my vibration issues, but long story short, there is a nasty vibration that permeates the structure of the car when the engine is near 3800 RPM. I suspect that the resonant frequency of the interface of the front subframes and floor/firewall is around 63 Hz or some multiple thereof, and the engine at 3800 RPM (63 Hz) is exciting that interface. I theorize that if I can stiffen this interface, it will move the resonant frequency out of the range at which the engine can excite it.
Translation: I think adding torque boxes to Grace may eliminate a stubborn vibration issue in the body structure. 

So naturally I wanted to know how to install Falcon torque boxes. I spent hours using the google machine, trying to learn all I could. Boiled down, I learned this: Nobody knows crap about Falcon torque boxes. A few people know a few things about Mustang torque boxes. The misinformation is deep. Mustangs and Falcons are similar, so Mustang torque boxes should work... right? Wrong. 

I figured the only way I was going to learn what I needed to know was to spend some sweat and dollars, so I started by removing the fenders and ordering a set of torque boxes. 

Not having any clue what might fit in my Falcon, I ordered a set of torque boxes for a 1965-68 convertible mustang. I knew that convertible Falcons had torque boxes, so maybe these would be the same. I soon learned that all unibody Fords in those days had a drastically different rocker panel than hardtop cars, so I ate the massive cost of return shipping on those parts. Lesson learned. Convertible torque boxes DO NOT fit on hardtops.

Mustang convertible driver's side torque box side view
Mustang convertible driver's side torque box top view

The other thing I learned with the torque boxes in hand and fenders off was that the early Falcons had much shorter rocker panels than Mustangs, and that they were not designed to have torque boxes at all. In the picture below, the blue line represents where a torque box would go, and the red line shows how long the rocker panel would need to be to effectively transfer torques and forces from the front frame rail and torque box into the rocker panel.

At this point I was not sure it would work, but I went ahead and ordered torque boxes and rocker panel extensions for a 1965-70 Mustang Coupe or Fastback. When they arrived, I mocked them up and found that these parts were not interchangeable with Falcon.

Because the Falcon is the Mustang's progenitor, you'll often hear that they have interchangeable parts. This is a bunch of crap. There are not enough directly interchangeable parts for this to even be a useful myth. I found myself in the familiar position of building my own performance parts for the Falcon out of cardboard. From here, the pictures do most of the talking.

If you've taken the time to look carefully at my design you may notice a few things. First, this torque box is quite a bit smaller than the Mustang boxes. This is on purpose, the front end of a Falcon is shorter than a Mustang, so Mustang sized torque boxes would interfere with the wheel if they could be installed on a Falcon. To compensate for this and make fabrication easier, I built them out of thicker steel than the Mustang boxes. Second, the rocker panel does not extend over the outside of the torque box. I do have concerns about this. Without that extra length in the rocker panel, stiffness will not be as high as it could be. If I feel the stiffness is lacking, I will find a way to lengthen the rocker panel about 4 inches.

(Disclaimer: this information applies only to round body Falcons from 1960-63. I have no idea if it applies to 64-70 Falcons. I believe minor changes were made to the chassis in 64)

Now that I've done one side, I'm hoping the other side will go quickly. I am anxious to see if my engineering theory was correct, and a stiffer body will eliminate the vibration issues. In the meantime, enjoy some cars I found in my neigborhood while on a Sunday walk. It seems I'm not the only one in town with a Falcon...

Sunday, April 16, 2017


You might ask yourself: "What has happened with dear old Grace recently?" Or you might have forgotten that she even exists, and I wouldn't blame you since it's been at least a billion time units since I blogged last. Before I write about Grace, I think I first need to deal with the subject of the TURD, my daily driver Jeep Cherokee. And to deal with the TURD, I need to back up a little bit...
If you can remember as far back as my last post, you will remember that Jen and I went for a Sunday walk and our neighborhood was submerged by a massive rainfall. This year California had the wettest year ever actually recorded in it's 122 years of record keeping. No president since Grover Cleveland could claim to have granted a water year to the residents of California quite like Donald Trump did during his early days in office. (I kid, I kid. I know it's the secretary of Agriculture that controls the rain, not the President) All the reservoirs are full, and the snow hasn't even all melted yet. 

Snow in the Sierras. Jen for scale.
More snow in the Sierras. Another Jen for scale.
Well, during this season of deluge it came to my attention that the floorboards of my Jeep were in terrible condition. My carpet was eternally wet and I could feel water splashing against the underside of the carpet as I drove through large puddles.

Once the rains stopped and it dried out, I decided it was time to take action.  Like Noah stepping from the Ark, I peeled back the carpet and this is what I found:

With a little (OK a metric butt-load) of work leaning over the door sill while kneeling outside the cabin, I got the floor pans out with a spot weld cutter and my angle grinder. That left me with a floor looking like this:

Then after an eternity stitch-welding the new floor pans in, I got to this point:

I then pressure washed the carpet, let it dry, and then washed and reinstalled the rest of the interior. Also as a part of the maintenance and rehabilitation of my daily driver, I purchased a set of tires from the Tire Rack which I had sent to my house. I had been away all week on business in New York, so when they arrived at my house before me on Friday afternoon I received this from Jen:
While I really, really, love new tires I love my wife even more. I guess I'm not the best at showing it sometimes...

So that brings us up to speed. The past several Saturdays have either been swallowed by the TURD, or I've spent them doing more important non-car stuff. However, that doesn't mean that I haven't been working on the Falcon at all. 

One small issue I addressed was the clutch master cylinder. I found that the clutch pedal feel was very light and vague, and the stroke of the pedal was much longer than I liked. When a pedal feels too light, this is usually because the master cylinder is too small or the slave cylinder is too large. Since I would not be able to change the size of  the slave cylinder, I decided to change the master cylinder.
Previous master cylinder setup
New master cylinder setup

The bore of the new master cylinder's piston area is about 44% larger than previous, which should translate into a corresponding 44% increase in force required to depress the pedal. I haven't measured anything, but that figure is probably close to accurate.

So what's next for dear sweet Grace? Torque boxes. If that doesn't mean anything to you, don't worry, it took me months to really figure out what they are and what they do. But I'll explain it all, hopefully in my next post. If torque boxes to mean something to you, stay tuned because we'll be breaking new ground for the early Falcon chassis. In the meantime, stay safe and remember: The only thing that can stop a bad guy with a banana is a good guy with a banana.