There were many points to be considered before making a start, and the question of tools was first carefully reviewed, and it was decided that my ordinary set - very ordinary - should meet the case, this consisting of one household saw, one hacksaw, various chisels, spanners and screw drivers, one small vice, one 4 -in. cramp, and all the usual odds and ends that are accumulated by the average handyman.

The Axle

The idea, after thinking over all the likely difficulties, grew into realization and forthwith a suitable axle unit was selected from a local car dismantler. There were so many different types and sizes of axles to choose from that the first visit to the dismantler's was somewhat bewildering. The points to consider were: (1) Extreme solidity; (2) Efficient braking and easy brake operation; (3) Wheel base; (4) Spring base, that is, distance between each spring; (5) Wheel and tire sizes.

Perhaps the spring base is of major importance, as in view of the very considerable overall width of the caravan, the springs should be mounted as wide apart as possible.

The average car front axle has a very narrow spring base, apart from which there is always some difficulty in locking the swivels, and as a scrap unit is probably in a worn condition the swivels would perhaps be very slack. 
This latter condition would naturally be very undesirable, and for these last two reasons it was eventually decided to make use of a rear axle assembly and one preferably with underslung springs.

The efficiency of the brakes on the average car rear axle may, up to a point, be taken for granted, but large -diameter brake drums are useful as the amount of effort at the brake lever is not very great. With regard to wheel size, there is never very much choice, but an average may be regarded as 19 in. with a low-pressure tire size 27 x 440 (or 450 x 19).

After a great deal of searching, I was fortunate in finding an old Riley (which had been very badly damaged at the front of the chassis, the rear axle, rear wheels and springs being apparently in quite sound condition. The rear axle and springs seemed adequately to fulfill the requirements under consideration, as the spring base was 37 in. center to center, wheel track 4 ft. and spring camber 7 in. approximately. A few days later, when the car was dismantled, I purchased the complete rear axle assembly, rear wheels and springs, and then proceeded to make due alterations to adapt the unit for use in the caravan chassis.

In doing this, the chief trouble lay in the fact of the propeller shaft being enclosed by a long torque tube, but as the tube at the forward end was already damaged, and in any case the propeller shaft, bevel pinion and other parts were not required, I decided to cut the crown gear housing short. On dismantling the differential and axle, it was found that the brakes were in quite good condition, apart from the camshafts being rather badly rusted, but it was not a difficult matter to put the brakes in really very good order by cleaning and greasing the camshafts and roughing up the brake linings.

The next step was the stripping of the differential assembly, which was rebuilt with the crown wheel left out, only the differential box and pinions remaining so as to provide a center bearing for both axle shafts. The nose of the crown gear housing where it had been cut short was blocked up with a plug of hard wood, and in finally fitting up the cover plate a quantity of grease was put in the axle casing. The results of this work were very gratifying, as the differential had an extremely smooth movement, the braking seemed efficient, and the unit was undoubtedly very solid.

Road Springs

For the time being I had to return to the work on the axle unit, and took off the road springs for examination. Apart from being somewhat rusty, they were quite sound and their camber seemed to be just suitable to give clearance to a straight chassis side member. Some provision had to be made for the axle unit to take the torque resistance when braking, and as separate torque rod or member would only have involved extra weight and unnecessary work, I decided to dowel the springs to the axle case, using the existing spring dowel pins and letting down the spring platform to grip the machined surface of the axle case. Apart from drilling the axle case, which gave tremendous resistance to my comparatively crude tools, there was no difficulty in doing this, although naturally great care had to be taken in drilling the dowel positions at the exactly correct point on the circumference of the axle case.

Making the Chassis

The undercarriage assembly having been completed, the chassis members were prepared for fitting. The longitudinal members were 12 ft. 3 in. by 2 in. by 3 in. ash, cut to length and planed on each face, and the cross members were also of 2 in. by 3 in. ash, 6 ft. long. Two center longitudinal members were selected and were strengthened by bolting to the 3 in. face, a strip of mild steel 1 1/2 in. by 3/16 in. for practically the whole of their length. It was decided to mount the axle a little behind center of the chassis in order to make the caravan slightly nose heavy, and so add to its road -holding qualities. Accordingly, a point 9 in. behind dead center of the center longitudinal members was duly marked, and the axle offered up, thereby giving the location of the front shackle. This was made by welding a strip of 1 1/2 in. by 3/16 in. mild steel to the inside of an inverted spring shackle. (See Fig. 1.)

The flooring was made of 7/16 in. tongued and grooved weather boarding in 6 ft. lengths, each length being screwed down across the top of each chassis side member. Special care was taken in fitting the floor boards to strengthen the framework against twist or distortion such as would be involved under normal road conditions. In the center of the flooring the boards were reduced to 4 ft. width to clear the road wheels which protruded above the height of the chassis members, leaving an aperture 30 in. by 24 in. on both sides to form a raised wheel arch which was built later. Each length of boarding, before being finally laid down, was well soaked in creosote, the top surface being left white so that the inside color scheme could be decided upon later.

At a distance of 36 in. behind the extreme front cross member and slung underneath the side members was bolted-up another cross member to carry the back end of the trailer bar. For both trailer bar and extra cross member, similar-sized timber was employed 2 in. by 3 in., and the trailer bar before fitting was strengthened with a strip of 11/2 in. wide steel bolted to its side. The trailer bar was attached to the front of the chassis cross member by means of a 1/2 in. steel bolt with large steel washers and a split-pinned nut, the rear end of the bar being similarly treated.

Bodywork

In view of the necessity for minimizing the total cost of the caravan it was decided to make use of ordinary commercial 1/8 in. plywood which is obtainable in a stock size of 5 ft. square sheets. The timber for the body pillars was next ordered in 7 ft. lengths of 1 1/2 in. square, rebated 1/4 in. on one face, 1/8 in. deep (see Fig. 6) for taking the end surface of each sheet of plywood. The two front side pillars were, however, of a stronger material, 3 in. by 1 1/2 in., and similarly rebated, the extra strength being considered necessary to take wind resistance and other similar forces normally met under travelling conditions.

It was now possible to complete the paneling of the caravan sides and accordingly the space between the curved roof rail M and the lower side rail J was filled in with plywood sheets, the top edges of which were cut to fit flush with the top of the curved rail M and, incidentally, the center panel top bracket was removed and refitted to clamp the sheeting between itself and the pillars. Although it would have been possible to have covered the roof framework with the waterproof material already obtained, it was thought that the inside finish would not be very satisfactory, apart from the obvious difficulty of fitting the material smoothly, and so it was decided first of all to cover the roof with plywood sheets similarly to the body sides. As the overall width of the roof was 5 ft. 9 in., a center rail had to be fitted through the length of the roof so that the roofing could be made in separate panels. This rail was obtained as a 12 ft. 6 in. length of ash 2 in. by 1/2 in. and was quite easily fitted, its curvature being almost identical with that of the side rails. The extremities were screwed directly to the roof end cross rails, and the center roof cross rail was recessed 1/4 in as an added steady, the joint of this being glued and screwed. The roof behind the center pillars was covered in by two separate sheets 5 ft. in length and approximately 2 ft. 10 in., and as two more sheets of plywood cut similarly did not entirely cover in the front end of the roof, an extra roof cross rail was made and fitted at the point marked N in Figs. 8 and 11. The roof covering was then completed by filling in the two comparatively small spaces at the front.

Waterproofing the Roof

After the outside roof paneling had been thoroughly dressed with primer, it was covered with a single piece of waterproofed hood material, similar to that used on cars, obtainable in 6 ft. widths and in several different colors and shades. The color scheme decided upon was two shades of green with cream uppers, and we were fortunate in obtaining a material of a suitable shade of green. The material was merely stretched from end to end of the roof and then drawn from side to side, and when finally, it was perfectly smooth all over the roof it was tacked down. The lower edges were left for the moment, as it was thought better to allow the weather to take effect on the material before finally cutting off and fitting the roof guttering. In order to protect the lower edge of each body panel, angle strips of aluminum beading were fitted between the pillars and bedded snugly against the plywood and the underside of the chassis side members, a little putty being spread along the inside of the aluminum beading before finally tapping down and pinning in position (see Fig. 15). This angle beading was also used to protect the edges of the front window bay and the edge of the plywood up each corner pillar.

The body shell being completed, the positioning of the windows was decided upon and a window frame made for the front. For all the windows planed deal 1 in. square rebated 1/4 in. by 3/8 in. (Fig. 16) was used, the window frame corners being jointed in the orthodox manner. The glass, after being cut to size, was bedded down into the window frame with putty and secured by strip 1/4 in. round beading (Fig. 17). Similar beading was also used as weather strip for the inside of the window aperture.
 

Figure 10. Method of joining the front corner pillars.

Windows

Working from the inside of the caravan, the side windows were marked out on the paneling, making a window aperture of 30 in. by 20 in. After cutting out this space with a hacksaw blade on an improvised handle, a frame was built up around the inside, 1 in. square deal being used and the window side pillars being jointed into the side rail. The lower rail of the window frame was extended to the inside of the front and center body pillars, making a waist rail above the seating position. This rail P was screwed on to the pillars mentioned and was also pinned and glued to the outside plywood.

A corresponding window was made to suit a similar operation carried out on the opposite side. The offside rear window was made up on identical lines, the aperture size being 20 in. by 20 in. On the outside of each window aperture strips of lath wood were fitted to form a window frame, and these strips were glued to the plywood and screwed through the plywood into the window main framework, thus giving added strength and also protecting the raw edges of the plywood where cut. In fitting these outside strips, similar strips were used to finish the joints between the lower sheets of body paneling and the top ones, and as a special precautionary measure any slight space between the two sheets of plywood was filled in with either red lead or putty before fixing, gluing and screwing the strips. To improve the outside appearance and also help to keep the window hinges watertight, louvres of sheet aluminum were made and fitted over each side window.

All the outside paneling and pillars next received their first coat of paint, and a line was drawn on each panel approximately 38 in. from the lower edge of the chassis side members in order to divide the cream uppers from the green lowers. The door was made in two sections, the top of the lower half coinciding with the color dividing line. Each door section was built up of a separate frame covered on the outside with a sheet of in. thick plywood, a Yale -type lock being fitted to the top door, along the bottom inside edge of which was fitted an overlapping strip to hold the lower door closed. Bolts were also fitted to the lower door.

The wheel arches were made up of boarding 10 ft. in width and cut as shown in Fig. 16. These pieces were then screwed directly on to the chassis side members in pairs, and a strip of sheet metal covered the top of the wheel arch boards, being pinned into position and bedded down into putty. The extremity of each strip of sheet metal terminated underneath the floor boards, to which it was pinned and made watertight.

The framework of the beds was next built, using 1 in. square deal and making as much use as possible of the already assembled body pillars. The width of the beds was decided at 24 in., and the height from the floor 16 in. It was thought that a concave base for the mattress would improve the comfort and, accordingly, each bed top rail was planed off on one edge to which the plywood was fitted as shown in Fig. 18. In the 6 ft. length of the top bed rail three supports of 1 -in. square were screwed to the underside and three similar struts were placed crosswise between the two top bed rails.

Plywood panels were then cut to fill in the 6 ft. length, the edges of the plywood being glued and screwed as previously. One half of the bed side had a fixed plywood panel, the front half being covered in with a sliding portion, the slide rails consisting of a length of 1/4-in. round beading screwed to the caravan floor, and a length of aluminum angle bead screwed to the top rail. The rear bunk was built up on similar lines, with the sliding panel on the nearside.

The whole of the inside next received its first and second coats of cream paint and all the body side rails, roof cross rails, roof center rail and window frames were picked out in green. It was decided to have a folding table with the fixed portion 12 in. long screwed to the underside of the front window cross rail, and strengthened by separate angle pieces attached to the center front pillars. The folding portion 28 in. long and 20 in. wide, the same as the fixed portion, rested against the same pillars when not in use and was held in position by a clip. When the table is raised a folding leg is dropped on to a catch fitted to the caravan floor. The floors and bunks were varnished stained and the table taken down for French polishing.