The automotive trailer discussed here was built by Dmitry Pekarev. In general, he is still a quite young man — he is 25 years old. In their family, which loves to spend summer vacations actively, there is an old VAZ-2101 car and a “Kazanka” boat with a motor. However, there was nothing to deliver the boat to the water with. So father and son Pekarev decided to build a universal car trailer so that they could carry both the boat and some loads in an easily removable body. Unfortunately, Dmitry’s father soon died tragically. Nevertheless, the son continued the work that had been started and successfully completed it.
Dmitry PEKAREV himself tells how the trailer was built.
My father and I managed only to discuss the design idea, and even then in general terms. Therefore I had to find out myself what requirements a trailer must meet in order to be registered calmly with the traffic police, and to learn how series-produced trailers are arranged and what has been done in this field by DIY builders. As a result of my search I came to the conclusion that the simplest and cheapest design to manufacture would be one with a welded frame of round thin-walled steel tubes and a leaf-spring axle suspension with additional hydraulic shock absorbers acting as dampers of lateral oscillations.
1 — tow hitch (standard); 2 — strut bushings (St3, tube 33.5×2.8); 3 — bow bunk strut (St3, tube 21.3×2.8); 4 — bunks (St3, sheet s2 plus rubber); 5 — bow bunk brace (St3, tube 21.3×2.8); 6 — drawbar extension (St3, tube 57×3); 7 — drawbar (St3, tube 57×3); 8 — body; 9 — bottom bunk pads (rubber s10); 10 — fenders (D16T, sheet s2); 11 — bumper guide (St3, tube 33.5×3.2); 12 — handrail (St3, rod Ø8); 13 — signal lamp cluster, right; 14 — spring bracket (St3, strip s5); 15 — shackle (St3, strip 50×9); 16 — M16 bolts; 17 — spring (from Moskvich-412); 18 — wheel (from VAZ-2101); 19 — spacers (St3, sheet s5); 20 — U-bolt (steel 45, rod Ø11); 21 — shock absorbers (from VAZ-2101); 22 — license plate; 23 — strut (St3, tube 21.3×2.8); 24 — drawbar brace (St3, angle 25×25); 25 — longitudinal beam (St3, tube 42.3×3.2); 26 — cross beams (St3, tube 42.3×3.2); 27 — license plate light (from UAZ-469); 28 — bumper (St3, angle 35×35); 29 — M12 bolt (3 pcs.); 30 — flanges (St3, sheet s10); 31 — axle tube (steel 45, tube 48×3); 32 — U-bolt plate (St3, sheet s8); 33 — bottom bunk (St3, tube 52x27x2); 34 — insert (St3, tube 50×3); 35 — shock absorber bushing; 36 — washer; 37 — shock absorber mounting eye (St3, strip 50×6); 38 — shock absorber pins (M12 bolts); 39 — bunk strut (St3, sheet s2); 40 — strut support (St3, tube 48×2); 41 — lock U-bolt (St3, rod Ø6); 42 — plate (St3, sheet s5).
That is the path I followed. I welded the frame with the drawbar from tubes. The drawbar is made from a larger-diameter tube and consists of three parts: a standard tow hitch, an extension used when transporting the boat, and the drawbar itself, reinforced with braces. The mating flanges are geometrically identical to the hitch flange. They are welded to inserts that are fixed in the tubes against axial movement and rotation by two M12 bolts each.
The rear of the frame is fitted with an extendable bumper with all the necessary lighting equipment and a license-plate mounting panel. When the boat is carried, the bumper is extended beyond the transom board and is clearly visible to drivers of following traffic. The telescopic bumper guides are secured in the longitudinal frame beams with M6 bolts.
The boat is placed on the trailer onto the bow bunks located on the drawbar extension, and onto the main bunks attached to the front and rear cross beams of the frame with easily removable locks. (Incidentally, the body is connected to the frame in the same way.) Finally the boat is pulled down onto the bunks with special straps.
1 — wheel disc; 2 — centering pin; 3, 12 — dust covers; 4 — M24 nut (left-hand M24); 5 — washer; 6 — M12 bolt; 7 — bearing 7605; 8 — hub (steel 45); 9 — bearing 7606; 10 — axle; 11 — spindle (steel 45).
The wheel axle is a tubular axle into which the spindles are tightly pressed. Wheel hubs are fitted onto them through single-row tapered roller bearings of two sizes. The bearing assemblies are protected on both sides by dust covers. The axle is suspended from the longitudinal frame beams by Moskvich five-leaf springs. On cars and most trailers I have seen, the axle tubes pass above the springs, which is probably done to lower the center of gravity of the trailer–load system. On ours, however, it is under the springs. This was done because the “Kazanka” is a very light boat and the position of its center of gravity will not significantly affect trailer stability. At the same time, the raised longitudinal axis (which is also the drawbar axis), even with a fully loaded trailer, will remain horizontal at the same height as the tow vehicle’s hitch and, during braking, will not create a force lifting the rear of the car. Operation fully confirmed these calculations — while driving, the trailer’s presence is almost unnoticeable.
We had a failure only once — a shock-absorber rod broke. I analyzed the breakage and found a design error: the shock absorber did not have even a slight forward tilt. And it should. Because when the spring works, the mutual angles of the shock absorber and its pins change within limits determined by the elasticity of the rubber bushings. Indeed, that is how it is done on all combined suspensions (elliptic leaf springs plus hydraulic shock absorbers).
As for the body design, it follows the classic layout, where the basis is a frame with uprights of rectangular tubing, covered with duralumin sheets.
TRAILER SPECIFICATIONS
Curb weight, kg … 100
Payload, kg … 500
Load on hitch ball joint, kg … 30
Trailer dimensions, mm:
max. length with boat drawbar … 5040
with body drawbar … 3365
width … 1520
track … 1360
Body dimensions, mm:
length … 1900
width … 1150
height … 300
«Modelist-Konstruktor» No. 2’99, D. PEKAREV
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