Frame Restoration

The frame was in fairly good condition, having only superficial rust and no signs of damage. Beyond the obvious need for cleaning and repainting, I made some badly needed modifications. The first was strengthening the front-suspension mounting point, a recognized weak spot in TR4s and 4As. The second was improving the vertical stiffness in the rear, a problem primarily with solid-axle TR4As.

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Contents

Initial Crud Removal

The frame was carrying somewhere between 10 and 20 pounds of greasy dirt, most of it near the mounting points of the transmission and differential. This is not surprising; the car leaks oil, it combines with dirt, and the result is a soft, gooey deposit. As it ages, it can turn into a hard, concrete-like one.

Here are some details of the frame as I began cleaning it. Parts were embalmed under an impressive layer of oily crud, which was almost an inch thick in places. Other parts had a layer of dry dirt, which, over the years, had turned into something like concrete. There was a little light surface rust, but not even any pitting. The frame also showed little damage; it had only a few dents. The worst were on the underside, probably damage from incorrect jacking. I've never seen an old TR frame without a few of those. I eventually determined that the frame was factory straight, a nice thing to find out.

I had kept the suspension in place to make it easier to move the frame around, but it eventually had to be removed. With the removal of the front suspension, rear axle, springs, and shock absorbers, the frame was stripped and ready for work.

The first step in cleaning the frame was to scrape off the oily dirt. I used a combination of paint scrapers and a vibratory multitool. Here, about a third of the frame has been scraped, and already several pounds of crud have been removed.

The so-called breast plate had been a repository for dirt, oil, and gravel. It was difficult to clean; the thick layer of dirt and pebbles had turned to concrete, and the corrugations didn't make cleaning any easier. Once I got it clean, however, I found four small holes. Two round ones were drilled, but I didn't know their purpose or if they were original. The other two holes were not the result of rust. It appeared that the drive shaft had been rubbing on the plate in a couple placed and thinned it, allowing the holes. Strange. I'll make sure that can't happen again.

As I continued, the frame started to look much better, and it gave me a lift to see a nice, solid frame emerging from beneath the crud deposits.

When the top side was finished, I had to flip the frame over to do the bottom. It was too heavy and unwieldy for one person, so I used my crane.

This is the first time the frame has been upside-down since it was in the Triumph factory! (Or, so I hope...)

I set the frame on my wheel dollies, to make it easy to move around, then continued to scrape crud.

Degreasing and Washing

Once the crud had been scraped off the frame, it was necessary to remove any residual oil. Cleaning and degreasing the frame involved washing it with a solvent, then wire-brushing it to remove hardened dirt, rust, and loose paint, and finally washing it with a strong detergent.

To clean the frame, I brushed it with a lot of clean naphtha and either let it run off or wiped it off with a clean rag. That got rid of the remaining oils, and once the solvent dried, the metal was dry to the touch. But a lot of loose rust, paint, and dry dirt remained.

The next step was to go over it with a wire brush in an angle grinder. That was fine for the large flat areas, but it didn't reach into the smaller places. Those required hand brushing and sanding. The point was to get rid of the surface rust and dirt that would interfere with painting, not to get it down to bare metal.

Finally, I took out my pressure washer and gave it a once-over with strong detergent, followed by a strong spray to remove any remaining surface dirt and loose rust. I also blasted the inside of the frame, getting out a lot of dirt and even a mouse nest. Fortunately, the TR4A frame has a lot of vent and drain holes, which allow it to be purged and dried effectively. I tilted it up on each end for an hour or two to drain, then let it sit in the sun for a few hours to dry completely. The cleaned frame is shown in the second picture, and a detail of the front in the third. I still needed to hand-sand some spots, especially weld areas for the frame mods. I then could do the frame modifications and paint it.

Many readers, I'm sure, are wondering if this doesn't risk creating new rust. As long as the frame is dried quickly after washing, no significant rust will form. Even if a few rust spots appeared (none have), they would not be of any consequence. I'm more concerned about rust on the inside of the frame, but the careful drying process should prevent it from forming.

Rust becomes a problem when metal sits wet for a long time, either because of puddling or some kind of material (e.g., mouse nests, dirt, dead pigeons) that holds water. Grinding the surface down to clean metal also might not be the best idea, as the thin surface-oxide layer seems to inhibit further rusting and is a better substrate for paint than bare metal. Of course, the surface won't last forever unpainted; after cleaning, getting a coat of paint on on the frame is a priority. But first, it needed a little work.

Dimensional Checks

Before I got too far, it seemed prudent to make a few dimensional checks. The shop manual describes a procedure for making those checks, which involves setting the frame on stands, dropping a plumb line from certain points on the frame to the floor below it, marking those points, and measuring them.

Although those measurements should identify any lateral deviation from the correct shape, they probably are not very good at identifying a twisted frame, a common problem. To identify twist, I used an electronic level. If the frame is twisted, one side should exhibit a downward or upward slope relative to the other side.

Using my electronic level, I began by leveling the frame in the lateral and longitudinal planes, just forward of the waist. The bar in the pictures is a 6-foot length of aluminum tube, 1/8-inch wall thickness, carefully checked for straightness. I normally use it for doing wheel alignments. To level the frame laterally, I placed it across the frame as shown, set on a pair of 1/2-inch aluminum blocks. This averaged out any irregularities in the frame surface, thus reducing their effect on the measurement. I did something similar in the longitudinal plane. I then checked flatness throughout the frame; it was within 0.2 degree everywhere, much of which was just surface irregularity. (For reference, 0.1 degree is 1/8 inch in six feet.) One spot initially measured 0.4 degree, but it turned out to be caused by a slight dome in the frame metal, not an alignment problem. In the rear, where the frame kicks up a little, both sides measured the same within the 0.1-degree resolution of the level.

The next step was to drop lines to the floor from the points identified in the shop manual and to mark the floor. The points are in pairs, symmetrically on each side of the frame. The idea is to find the center between each pair and and set up a datum line for the center of the frame. If the frame is straight, those center points should all lie on, or very close to, that line. The center datum lined up with the points with an average error around 2 millimeters, a result probably within measurement and layout accuracy. I also checked a few of the diagonal measurements, which were similarly accurate. I didn't check all the diagonals, since it was already clear that the frame was factory straight.

I had been bothered by the fact that the front suspension had a stack of four camber-alignment shims on the right side but only one on the left. That concerned me, as the large difference could have been caused by frame misalignment, so I checked the front of the frame carefully. The frame rails were right on, so were the spring towers, and the locations of the A-arm mounting bracket faces, measured from the edges of the frame rails, were all within +- 0.05 inches. Nothing I measured could account for the extra ~0.2 inches of shims on one side. It seemed clear that the frame was not the reason for the large number of shims, and the likely problem was simply a build-up of small differences, due to dimensional tolerances in the frame and wear in the bushings or other suspension parts.

Repair of Jack Damage

The underside of the frame was dimpled, probably from the use of a bottle jack to lift the car. The frame is only 16 gauge metal, which dents more easily than many people realize. It had several dents; the worst were near the front on both sides. They had no structural consequence, but they were unsightly, so I wanted to get rid of the deepest ones.

To fix the dimples, I cut out the worst areas on both sides, hammered the pieces flat, and welded them back into place. I ground the welds quite flat so the patches wouldn't be noticeable once the frame was painted.

Below, the patch with the first of a couple coats of high-build primer.

Preventing this kind of damage is easy: use a large wood block between the jack and the frame.

Frame Modifications

A few things needed to be done:

  1. TR4A frames have weak mounting points for the lower A-arms in the front suspension. I purchased the standard kit of reinforcement pieces to correct this problem; it required some drilling, trimming, and welding.
  2. The vertical stiffness of the rear is not adequate. Because of the way the suspension is supported, this is less of a problem with the IRS cars. The solid-axle cars have a greater problem, but there are more possibilities for stiffening the frame.

Front Suspension Mounts

I had some difficulty getting all the paint, rust, and dirt out of some parts of the frame where I eventually needed to weld. Although I have a small blaster, I hate media blasting, as it makes quite a mess, and sometimes leaves abrasive in places where it's not wanted. Still, it seemed like the only way to get the crud out of the frame corners and other minimally accessible spots.

After blasting, I sprayed the areas with weld-through primer.

Reinforcing the lower A-arm supports involves welding reinforcements to them, using special back-up washers, and adding a second stud to each A-arm mounting bracket. (The bracket modifications are described in the Suspension page.) Since the modified bracket has two studs, at least one new hole must be drilled in the suspension mount. Below are the left-side mounts with the reinforcements welded into place.

Note that the "foot" of the front mount (left picture) had to be trimmed rather short so it wouldn't interfere with the bumper support, which bolts to the side of the frame.

I bolted a back-up washer to the front of each mount as a template for drilling two new holes. This was not the greatest of ideas, as the holes in the washer are larger than the ones that were drilled. As a result, the drilled holes were not located perfectly, but a little filing fixed them. The idea of a drilling template is fine, but making a special, more precise template would have been better.

Only the forward holes were used to attach the A-arm to the car; I planned for the others to have bolts that clamp the washer to the suspension mount, thus stiffening the mount a bit more. I wasn't sure how easy that would be, as the space was minimal. As it happened, I had to modify the bolts for those holes, but I made everything fit.

I used some sealer to close the small gap between the reinforcement and the mount. That should help prevent water infiltration and subsequent rust. That gap can't be welded, as a weld in that location can't be ground down, and it might interfere with the seating of the A-arm bracket. I trial-fit the brackets, and they seemed to fit well. I was worried that the nut for the A-arm's large pivot bolt might not clear the new reinforcing plates, but I found that there was adequate clearance.

Rear Frame Stiffening

To stiffen the frame in the rear, in the vertical plane, I decided to add plates of 12-gauge steel to the insides of the frame rails. This seemed like the least intrusive approach. It still should provide a significant improvement, as it nearly doubles the total thickness of the steel in the vertical sides. As a disadvantage, it makes the frame look like it has been patched. It also adds a couple pounds, which is perhaps 10% of the weight of the crud I scraped off the frame.

I'm concerned about water infiltration between the reinforcing plates and the frame, where it can't evaporate easily, eventually causing rust. To protect them, I gave the frame rails and insides of the reinforcing plates a coat of weld-through primer. Calling this stuff "weld through" is a bit optimistic, as it's difficult to produce a good MIG weld on metal primed with it. (Stick welding through it might be easier; I don't really know.) To weld the plate successfully, I had to sand the primer off the bottom lip of the frame, and, as later pictures show, I didn't prime the outer side of the reinforcing plate.

I cut patch pieces and curved them slightly to fit closely to the frame rails. I gave one side, the one adjacent to the rails, a coat of primer. The picture below also shows one of the four reinforcing plates. In the background are the reinforcing pieces for the front suspension, which I also primed.

I first clamped the patches and tacked them into place. After removing the clamps, I welded them. Not a beautiful weld, but competent, I think. The welder produced quite a lot of spatter; I wish I could figure out how to minimize that. Maybe it's inevitable when you use the welder at full power, as was necessary here.

In retrospect, I should have moved that plate all the way forward to the frame arch. I thought of that at one point and promptly forgot. Well, no job is perfect.

I spread a fillet of body-panel sealer along the edges of the welded pieces, as the welds alone probably were not water tight. I then primed them. I know, this is not what you usually do with a frame, but in this case I think it's warranted.

Radiator Shield

The frame has a separate cross piece, bolted to the front, which shields the radiator from things the car might hit, such as rocks, telephone poles, small children, chupacabras, or the occasional moose. Mine clearly had protected the radiator from many such impacts, as it was badly dented and bent inward in the center. Taking out the dents was not particularly difficult, but because of its L-shaped cross section, removing the bend was much harder. I tried a number of options with my hydraulic press, but nothing worked. No great surprise. It must have taken quite a whack to get it into that condition. And, shrinking metal back to shape is always more difficult than stretching it.

I finally decided to cut V-shaped slots in the shield at the point where it was bent, straighten it, and weld the pieces back together. I also straightened the front rings and cleaned it with a wire wheel.

Before welding the gap, I checked the shield's fit to the frame, then welded the gap from both sides. I also welded the front rings, which had been smooshed.

I ground down the weld on the outside, where it would have been visible, but left it full thickness on the inside, for strength.

The shield was primed and painted with the same paints as the rest of the frame.

Those rings, by the way, are not intended for towing; they're not strong enough. They probably served as anchor points for a tie-down in shipping. I could have justified leaving them off, as they have no practical value at this point, and might tempt someone to use them for towing. But this kind of work isn't always about practicality.

Here it is much later, mounted on the car, nobly protecting my expensive aluminum radiator.

Frame Painting

I ran out of shielding gas while doing the frame mods, so I started on the priming. I used a rust-converting primer, keeping it away from the areas that I still needed to weld. The primer goes on white but changes to a dark, blue-black as it dries. It contains tannins, which convert the rust to iron tannates, which are black and much more stable than the original brown oxide. For what it's worth, that's the official story; in any case, it makes a good primer for lightly rusted surfaces.

The conventional wisdom regarding rust-converting primers is that they will not cure unless the surface has an oxide coating. The previous photos show that most of the surface did have a light oxide, but some areas didn't. Nevertheless, the primer cured and adhered just fine everywhere. I certainly wouldn't try to use this primer on bright metal--for one thing, there's just no point--but the requirement of an oxide coating is not as severe as it sounds.

There are other options. In the past, I've used the Rustoleum primer designed for lightly rusted metal. It's a good product, but available only in white; then, every chip or scratch in the black frame shows bright white underneath, accentuating the flaw. Unless I could remove absolutely all the rust (and I'm not sure that's really possible), I would not use polyurethane or epoxy primers designed for auto-body use. Many people also like to have frames powder coated. In the past, I have experienced adhesion problems with powder coating, so I avoid using it.

With a new tank of welding gas, I completed the frame mods and I was able to finish the priming. The light areas on the frame are weld-through primer, which I had sprayed around the lower A-arm supports to prevent rust after media-blasting them. I left it in place; no reason not to. I also chased all the threaded holes with taps.

I gave the frame two coats of paint, three (or more) in places that might be water traps. I used Rustoleum semi-gloss paint, thinned approximately 15% with mineral spirits, a common choice for restoring the frames of little British cars. Painting the top side was easy; for the underside, I raised one end with my crane.

The final step was to coat the interiors of the frame channels with Eastwood's internal frame coating. I don't know if that was necessary, as the frame had already lasted 50 years in a rust-belt state without it, but it certainly couldn't hurt. Cleaning out all the dirt and mouse nests (which trap and hold water) probably did more to prevent rust than anything else could have.

Below are some details of the finished frame.