Fig. 1. Finished trailer all ready to take down the
road. This trailer was designed to be drawn by even the smallest auto.
An Easily Built Cabin Trailer
Let's Call It "TERRA CRUISER"
TIME was and not so long ago when trailers were heavy
and hard to handle, and they offered little comfort or convenience to their
owners. The changed demands of the traveling public, however, are adequately
supplied today by this easily built streamlined trailer. Adapted to construction
by homecraft workers, it is comparatively inexpensive, light in weight,
and due to its efficient streamlining adds an insignificant burden to any
auto. It has a distinctive appearance. It provides ample space inside and
is adaptable for travel anywhere, any time, with comfort, convenience and
In building the Terra Cruiser, SCIENCE AND MECHANICS has
had the cooperation of both the Hammer Blow Tool Company and Trotwood Trailers,
Fig. 2. "Terra Cruiser" is designed to take any
popular axle, such as the Trotwood "Step Action" shown above, made by Trotwood
The complete under chassis (axle, springs, wheels, Warner
electric brakes and controls), hitch, sink, pump, and beds were furnished
to Mr. Jackson through the courtesy of Hammer Blow Tool Company. The "Step
Action" axle was furnished by Trotwood Trailers so that Mr. Jackson might
design the body frame to fit either unit, as well as others which might
be desired. The basis of any safe and efficient trailer is the axle assembly,
and this trailer is not an exception. This particular part should be selected
carefully with a view towards not only easy riding qualities but the ability
to track surely and evenly at all speeds.
Fig. 3. Integral bracket castings are provided
for fastening the frame to the Tor-Q-Les Under Chassis, made by Hammer
Blow Tool Company.
Many cast off auto axles lack these necessary qualities,
and as most standard trailer axle assemblies are sold at low prices, there
is no reason to handicap one's Terra Cruiser with inefficient parts. Two
representative axle assemblies are indicated on the plans. Either type
is more than satisfactory, and as legislation is being expanded enforcing
the use of brakes upon trailers, the axle purchased should be machined
so brakes may be added at any time not only for conformity to the law but
also for super safety. The axle utilized on the Terra Cruiser is of 70-inch
tread width. This is wider than standard car tread, but will occasion no
difficulty as all roads are now smooth, and even those not so smooth may
be traveled with comparative ease with the broader, more stable tread.
The trailer will pull more easily in loose sandy soil with the wider tread.
To begin the construction, the material list of axle assembly parts should
be scanned closely.
Trailer Material and Parts List
With the various parts collected, the axle assembly and
wheels are set in place and the 1/4" x 2" x 2" x 9' lengthwise angle irons
bolted in place to the spring hangers. The center line of the wheels is
measured to square the axle assembly with the angle iron frame. These measurements
are indicated upon the plans.
The remainder of the axle frame assembly is quite simple
and consists of squaring the angle iron crosspieces with the lengthwise
pieces at the front and rear ends of wheel wells, as shown in Fig. 4, clamping
the pieces together temporarily and drilling for 3/8" bolts. Square the
frame parts and allow two inches clearance between each side of the tire
and crosswise angle irons and bolt these 1/4" x 2" x 2" angle irons in
place with 3/8" machine bolts. The ends of these angles receive and support
the wheel housings later.
Each end of the trailer frame is secured and reinforced
with a 6' 6" length of 1/4" x 2" x 2" angle iron, installed with flange
and bolted in place with 3/8" machine bolts as indicated in Fig. 4. Secure
all bolts with lock washers for permanent holding. The tongue is made of
two pieces of 1/4"x 2"x 2" angle iron, each 5' 6" long, bolted in place
as shown with a standard ball and socket trailer coupling adapted for use
with angle iron.
Fig. 4. Bottom view of angle iron frame, tongue
and coupler assembly. Detail shows how outside sills are mortised to receive
posts on side wall assembly.
Fig. 5. Close-up of finished trailer chassis after
1/2 " plywood floor has been attached. Wheel housings have also been attached.
Your frame will be improved greatly by welding all connections
where angles bolt together. However, this is not imperative if you do not
have access to welding facilities.
Floor and Wheel Housings
The trailer frame is now ready for the attachment of wood
body sills. All sills are cut from 2" x 4"'s, the center and outer sills
being of fir, pine, or oak, while the sills along the spring hangers consist
of a 2 x 4 ripped
in the center, each half fitting inside of the trailer angle iron, as shown
in the sketch at Fig. 6.
Fig. 6. Perspective sketch of trailer frame and
axle assembly. Details show sill strips fitted to angles, also composite
sheet steel and wood wheel housings.
Sills in contact with angle iron should be coated with
asphaltum paint before attaching, clamped in place, drilled and bolted
to angle irons with 1/4" x 2 1/2" carriage bolts. The outer sills must
be shimmed underneath with small pieces of thin hardwood to make all sills
even and level. Nail the shims to the sills to prevent moving. A straightedge
across the sills while attaching will insure a level floor. The entire
frame should now be coated with two coats of asphaltum paint for utmost
protection. Laying the floor is next.
This floor may be either 5-ply 1/2"
thickness plywood or 3/4 x 6"
tongued and grooved porch flooring laid cross-wise. The original was floored
with plywood, and this was laid with a seam down the center sill, while
the waste cut from the sides and wheel openings was used for the rear end
of the floor. Coat the underside of plywood with asphaltum paint, clamp
the floor in place and fasten to the sills with 1 1/2" No. 8 f.h. screws.
Let the flooring extend about three inches over the edge of the frame,
both front and rear ends.
The wheel openings are now enclosed as shown in Fig. 6,
and if the openings vary from the plans due to other axles being used,
adapt the wheel housings to the required openings. The wheel enclosures
are made with 3/4" x 6" tongued and grooved flooring, making the inside
of the enclosure solid and cutting out the outside for wheel removal.
Strips measuring 3/4"x 1 1/2" bind the ends of the inner
enclosure boards together and are fastened with screws to the floor at
the opening. The outer side of the enclosure is fastened similarly. To
obtain strong joints, coat the grooves of the boards with casein glue before
fastening, and before securing the enclosure to the floor, coat both adjoining
surfaces well with asphaltum paint. The tops of the wheel enclosures are
covered with galvanized sheet iron and screw fastened in place to the edges
of the enclosure sides.
Fig. 7. Side view of trailer frame assembly with
floor and walls in place. Names and positions of parts, together with their
arrangement are given.
With the axle frame assembly finished, coat the floor
with equal parts of linseed oil and turpentine, or if it is to be insulated
later, coat it with asphaltum paint. Before further construction work is
done, set up the trailer bed where it may be built without moving and block
it in a level position at the four corners.
Building the Walls and Side Frames
Constructing the sides is next. The plans indicate details
of these, and it is only necessary to lay the four sheets of plywood that
comprise the sides down on a flat space, as shown in Fig. 8. Then lay out
and mark the curved shape with the aid of a long thin batten sprung around
so as to touch all points and saw to shape.
Fig. 8. Layout of plywood sheets used to form
wall. Dimensions are shown for all curved edges and also openings. The
door is cut 25" x 5' 5 1/2" high, on right wall only.
One side will serve as a pattern for the other side. With
both sides cut, mark and cut out the window and door openings. It is important
before the framework is attached to remember that a right and a left side
are to be made with the framework on the inside of each as indicated clearly
by Figs. 9 and 10. The outer edge of each side serves as a guide to enable
the marking to shape of the 3/4" x 2" edge strips. Mark and cut the inner
edge parallel to the outer edge so that the strips will be two inches wide.
Lay out and cut the notches for the roof beams before fastening the strips
in place on the wall. Roof beams must be spaced accurately to receive the
48" widths of pressed wood. Every third roof beam is a 1 5/8" square beam,
to receive both edges of adjacent sheets. Coat these edge strips with casein
glue, clamp in place and fasten with 1" No. 8 f.h. screws, inserted from
the outside or plywood side. The fastenings are to be spaced about three
inches apart. With these border pieces in place around the edges of each
trailer wall, the 1 5/8" square framing is next cut to fit, coated with
glue on the side next to the trailer wall, and fastened with 1" No. 8 f.h.
Fig. 9. Left wall cut and assembled with posts,
frames and edge strips. Plywood batten strips must be fastened over all
joints on inside of wall.
The posts at the doorway should overlap the edge of the
opening 1/2" on either side, to provide a ledge for the door to close against.
The pieces of plywood cut from the door and window openings are saved for
constructing these parts later. A 2" x 4" should be attached temporarily
across each side of the trailer to reinforce the wall until braced and
fastened to the trailer floor.
Fig. 10. Right wall, showing changes for door
opening. Edging strips only are notched to receive ends of roof beams.
Notch both wall edge strips at one cut.
Attaching the sides to the trailer platform or floor comes
next. Set one wall in position so you can mark the exact position of the
notches on the sills and floor. The side sills and floor are notched to
receive the 1 5/8" square posts of side wall and then 1/4" x 4 1/4" carriage
bolts are inserted through the trailer side and sill with the nut on the
inside. Attach both sides similarly, although posts must be cut to fit
at wheel housings and doorway.
Fig. 11. Close-up of right side wall with all
posts, frames and edge strips. Wall must be braced with 2"x4" or heavy
board while mounting.
Fig. 12. Trailer chassis with left wall fitted
and bolted in place. Floor and outside sills have been mortised to receive
post. Bolts go through sill.
At each end of the trailer floor, it will be necessary
to attach filler pieces cut from 2" x 4"s so as to conform to the curvature
of the sides, providing a means of attaching the roof covering at each
end of the floor. Bolt the filler pieces to the frame and screw fasten
to the plywood floor, trimming the floor even with filler pieces. With
the two sides attached to the sills, plumb and brace the side walls together
temporarily with wood crosspieces and proceed to fasten the roof beams
in place. Pressed wood 1/8" x 48" x 84" is laid crosswise to cover the
Fig. 13. Rear view of trailer body before attaching
roof. Note arrangement of roof beams. Every third beam is 1 5/8" square
to receive both edges of joints.
As the sheets are 48" wide, this will allow a space of
three roof beams on 16" centers to each sheet. The roof beams are 3/4"
x 1 5/8" fir strips with a 1 5/8" square crosspiece at each roof joint.
The procedure to follow is to attach three roof beams and then a width
of pressed wood, notching the crosspieces halfway into edge pieces, coating
the joints with glue, and fastening with screws. The pressed wood is fastened
to the roof beams and the edges of the side walls with 1" No. 8 f.h. screws
spaced about three inches apart. Continue in this manner until the entire
roof is covered.
Fig. 14. Details of plywood door construction.
Note "sandwich" method of building a strong door. Provide weather strip to exclude dirt, rain, ect.
Square up and brace the sides in alignment while attaching
the pressed wood to in-sure square, even walls. Round the edges of the
pressed wood smoothly and prepare for covering. Fill all screw holes and
any irregularities with plastic wood or casein glue to which fine sawdust
is added, and sand all surfaces smooth. The trailer shell is covered with
heavy weight muslin cemented in place with any good grade of canvas cement.
Muslin 80 inches in width is tacked in place along one edge. The surface
of the plywood is coated with cement, and the cloth is pressed and smoothed
onto the cement with a block. Cover the sides first, then the top, lapping
the side material over the top and bringing the top material even with
the sides. As the cement has considerable body by itself, the use of heavy
canvas is not necessary, and heavy weight muslin is quite satisfactory.
Fig. 15. Details of window construction similar
to that used on the door. Note how curved border on frames accentuates
streamlined effect of trailer.
The surface of the cloth is filled by adding alcohol to
the cement and coating the entire cloth surface. When it is dry, sand smooth
and apply four coats of paste paint which has been thinned with turpentine.
Leave the final finishing coats until last. These should be enamel colors
of preferred shades. The roof should be painted with standard exterior
aluminum paint. (To be concluded in next issue)
Fig. 31. Parked in a favorite spot, with camp
gear safe and ready, assuring comfortable sleep. Note the variation in
color scheme from that shown in the first installment. Others may be chosen.
An Easily Built Cabin Trailer
Finishing the Interior
COMPLETE instructions for building the under chassis,
floor, walls, and roof of this cabin trailer were given in the July-August,
1940, issue of SCIENCE AND MECHANICS. Directions were also given for applying
the fabric covering. The construction of the interior fittings is completed
in this issue.
Fig. 16. Side view of completed trailer, showing
door and doorway construction. Full-size door allows easy entrance while
large windows provide ample light and ventilation.
Cover the inside edges of the window openings with 1/8"
x 2" strips of pressed wood. Cement the underside and screw fasten in place.
The windows are made like a sandwich with the outer shell of 1/4" pressed
wood, while the inner shell is the 1/4" plywood cut from the openings,
as shown in Figs. 14 and 15 in the July-August issue. Cut to shape as shown,
imbed glass between the shells with cement, and use 1/8" x 1 1/4" pressed
wood strips for fillers to retain and position the glass between the shells.
Fig. 17. Picture drawing of framework and facing
of "daveno" combination bed, with storage lockers for bedding and clothes.
Fig. 18. Close-up of partly finished "daveno"
bed with facing panel in place. Also shows part of the framing for galley.
Fig. 19. Completed "daveno" bed with cushions
arranged for day use as a davenport. Also shows corner of galley worktable.
Fig. 20. Three views of dinette table. Top may
be hinged to legs for folding away when using seats for extra bed.
Fig. 21. Framing for dinette seat.
Fig. 22. End view of dinette seat with framework
shown by dotted lines.
Fig. 23. Close-up of dinette made up for meal
times. Cushions have been removed to show construction. Ample space is
provided to seat four persons at once.
Fasten the window shells together with 5/8" No. 6 r.h.
screws. Trim the windows to fit the openings. Provide a 1/2" square stop
strip behind each window and attach hinges at the tops. Screens and frames
are provided to fit on the inside of the window opening with a window throwout
arm working through the screen frames to actuate the windows.
Installing the Door
The doorway is fitted with fillers, or knees, as indicated
in Fig. 10 of the July-August issue, and the door itself is then fitted
into place. Use separate or continuous hinges to hang door, and cover the
inside edges of the door frame with 1/8" pressed wood or plywood, the same
as was done with the window. Fig. 16 gives a good view of the finished
door and doorway.
Fig. 24. Front view of framing and corner detail
of galley, with space for stove and sink.
Fig. 25. Front view of galley panel, showing arrangement
of doors and drawers with hardware.
An auto type door handle is suggested for the door, although
a regular key lock may be used. If desirable for through vision, cut the
front and rear windows to line up with the windows of the tow car. Imbed
these in cement and construct as indicated upon the plans. The interior,
its fittings and arrangements allow a variety wide enough to be adaptable
to any purse or purpose. The windows and outside edges may be trimmed with
aluminum angle molding, and it does enhance the appearance of the exterior
to trim with 3/I6" x 2" half oval aluminum molding after the painting is
Planning the Interior
The interior arrangement shown in our plan is comparatively
simple and convenient and one that has been used for years with satisfaction.
The large seat at the rear is furnished with two cushions of the inner
spring type. One cushion serves as a backrest; the other as a comfortable
lounge, as shown in Fig. 19. The drawings and illustrations here shown
are full explanation of the method of construction.
Fig. 26. Close-up of framing for galley and cabinets.
Joints shown are made with T & G flooring strips.
When pushed forward over the lounge seat, the two cushions
form a double bed. The framework for all seats and cabinets is 3/4"x 2"
strip material with one edge rabbeted as shown in detail in Figs. 17 and
24. The outer face of all cabinet work is covered with 1/4" plywood. If
round corner doors and openings are cut in all cabinets, a more uniform
streamlined design, in keeping with the exterior, will be effected. The
breakfast nook sides and table are the only pieces constructed of 1/2"
thickness plywood, and incidentally, the table may be secured to the wall
with regular trailer brackets and a plywood leg or nickel-plated pipe and
floor flanges. The cabinet or galley contains all culinary and food storage
needs and is built as indicated. The top is covered with 1/4" pressed wood.
The galley is arranged to hold the regular two-burner trailer stove with
removable lids in one compartment, Fig. 29, providing a fireproof enclosure
when lined with sheet metal. The sink occupies the front top half of the
cabinet and is also fitted with a pump which is connected with a 5 to 15
gallon water supply tank with baffle plates and hand hole cleanouts.
Fig. 27. Close-up of galley and cabinets. Note
generous space for all galley equipment, food and staples, also ice box
This tank should preferably be located in the rear of
the trailer. For ordinary purposes a 5-gallon jug will suffice. The roof
ventilator is built over the stove to ventilate and carry away odors. Additional
leaves of 1/4" plywood may be attached to the end of the cabinet top for
greater working table space. The icebox rests upon the floor at the front
and is first lined with thick insulation material. Then a sheet metal container
is inserted to hold ice and perishables. A drain is provided through the
floor. Just to the rear of the doorway is the wardrobe, which is made to
hold all articles of apparel, Fig. 30.
Fig. 28. Extra locker space can be added above
galley, in the corner of the roof, if desired.
Fig. 29. Stove compartment with hinged door and
cover. Stove may be removed for cooking outdoors.
The wardrobe door is fitted with a mirror. Cup and glass
racks are provided over the cabinet. Roof lockers are built in as needed,
Fig. 28. Electrical wiring is carried in the walls. One dome light should
be supplied and a wall fixture on each side of the breakfast nook. A light
over the cabinet is a convenience.
Fig. 30. Picture drawing of clothes wardrobe,
showing plywood panel construction with strip reinforcements at corners.
Top fits against roof.
The wiring should be for both 6-volt and 110-volt current.
When parked at points whole this current is available, outlet plugs will
enable the use of electric irons, toasters, etc. Stop and tail lights are
fitted to the rear. Four red clearance lights are also fitted at the front
and rear to outline the exact width of the trailer. Many states require
two stop lights and a safety chain from the tow car to the trailer to insure
safety. After all the interior cabinet work is completed, for better insulation,
the inside may be celled with regular fiber wall board and all joints covered
with thin wood strips. The inside should be finished in a bright color
to aid vision. The cabinet work is stained or varnished in the natural
finish or painted if so desired. The floor is covered with linoleum or
carpet. When parked, parking legs at the corners will be of material assistance.
A retractable third wheel parking leg attached to the tongue will aid in
ready maneuvering of the trailer with the tow car absent. Striker plates
of galvanized iron should be fitted to the lower front part of the body
to reduce damage to the surface from flying stones.