Welding Reinforcements To Steel Filling By Arthur W. J. G. Ord-Hume, EAA 8579 "Mirador", Rose Mead, Lake Sandown, Isle of Wight, England HE DESIGNER OF a light aircraft often calls for reinforcT ing washers or discs to be brazed or welded to a plate fitting to increase the bearing surface for bolts or pins

x-

which may pass through it. Such a fitting is illustrated in Fig. 1, the part depicted actually being one of the main joint plates between the wing and the fuselage of the French Druine Turbi two-place wooden airplane. This fitting also takes one of the landing gear struts.

Ilbte : This reinforcement is not shown on the plans but we decided to fit it.

Fig. 1. Discolored areas after welding.

Cracks

Mild steel disc one side only Fig. 1. Arrangement of fitting in question showing reinforcing discs.

This type of fitting is tricky to make and unless care is taken in welding or brazing the discs into place, cracks can develop which may be invisible to the naked eye. This is due to the irregular shape of the metal part and the fact that the circular area of heating cools unevenly by virtue of the fact that the heat transmission to the 'cold' part of the plate is not even. Some years ago, I made up four plates as shown in Fig. 1. Of these, only one was serviceable and the lesson I gained through experience will be of interest to many other constructors who may be ignorant, as I was, of this procedure. The first plate I made up was welded in the normal way. On cooling it appeared satisfactory and was sandblasted and cadmium-plated. After plating, the areas marked 'X' in Fig. 2 were discolored, indicating either loose scale or cracks beneath. I placed the fitting in the vise and proceeded to attempt to bend the welded ends. They snapped off — very easily. The metal had neatly cracked at each side to within about Vi in. at the centre (Fig. 3). 30

MAY . 1961

Fig.

3. Cracks visible after de-scaling.

I made up another fitting and this time examined it immediately after welding. The cracks, very minute, were there. The next step was to see if brazing had the same effect. This may be considered an unnecessary step to have taken if the cracks were due to a heating and cooling process, the result being identical whether braze or weld was tried. However, an important discovery was made which welding could not have readily shown. After brazing, the cracks were clearly visible. The braze, being very volatile, had followed the cracks and, after polishing to the bare metal, the cracks showed up bright yellow. This proved that the cracking took place

Tips On Vise Grip Pliers Q UITE BY COINCIDENCE, we received a news release and

a bulkhead, etc. Two pieces of sheet metal can be firmly clamped together for drilling, with little danger of their twisting out of alignment. When working around firewalls, tail surfaces, etc., one-man assembly is a cinch; clamp the tool onto the bolt head and put the bolt into its hole from inside the aircraft. Rotate the tool until the end of its handle binds on a nearby flange or projection, and then run the nut on from outside.

From member Hap Wilson, president of Chapter 17, Marysville, Tenn., we have the following tip:

Another firm, Precision Equipment Co., 4407 Ravenswood Ave., Chicago 40, 111., sells a gadget consisting of two common vise grip pliers which are attached to a base clamp by means of ball-jointed, adjustable arms. It looks approximately like the arms and jaws of a lobster. Clamped to the workbench, it will hold two parts in any desired position for welding or assembly. Price

a letter on the same subject at about the same time. Our friends at Cooper Industries, Inc., 2149 E. Pratt Blvd., Oak Grove, 111., sent the accompanying photo of their new PLJERENCH. According to their release, the tool is geared for a 10-to-l leverage ratio and has 100 percent parallel jaws. Selling for $12.75, it is quality made and the kit includes a variety of jaws and cutters.

"When buying any kind of vise grip plier, get the type which keeps its jaws parallel as it opens and closes. Instead of concentrated pressure, the load is distributed and the tendency of the plier or wrench to slip is much reduced. Such a tool also prevents localized marring of work. It will hold onto a nut in some inaccessible place while one man turns the bolt from the other side of

is comparable to the above-mentioned tool and details can be had from Precision by writing to them.

WELDING REINFORCEMENTS . . . From preceding -page

not only on cooling, but also during either the heating up or actual fusion process.

The final fitting was made up with the aid of two torches, one with a large nozzle and a 'warm' flame played evenly over the fitting and the other doing the actual welding. Because the rest of the fitting was tending to cool before the thicker, welded end, the first torch was kept playing on the metal during cooling, gradually being raised from the metal until the part was evenly black. An alternative method would have been to weld up the fitting whilst it was in a furnace or on a gas-jet. The effect here was to normalize the fitting during and after the welding process, allowing perfectly even cooling. The fitting was crack-detected and found entirely satisfactory.

Subsequent tests tended to show that kite-shaped reinforcing pieces were easier to weld or braze, the stresses set up being less severe in fusion and cooling. This does prove the need to consider carefully the

problems of irregular heating and cooling portions of comparatively large or thick masses of metal and also of close scrutiny of welding after cooling and before the

application of any form of protective treatment.

A

\

tfeld all round Fig. 4. This type of reinforcing

piece

make but it is easily welded and also

takes longer to

stiffens the

SPORT AVIATION

lug. 31