Lister 5/1 Diesel

Drawbar Trailer Design & Build

Designing & Building Our 6-Wheel Drawbar Trailer Page 1

In 2009 we attended the Essex Country Show at Barleylands near Billericay in Essex. We took our Ruston 1ZHR on its normal trailer, and because we couldn't take the caravan, we had to take a tent to sleep in overnight. It was an interesting experience! We had camped many times over the years, and still had all of our kit from the trips to Spain, but our ages were starting to tell, and we both talked about something better.

Ruston 1ZHR On Original Trolley

Various ideas were discussed, and I took some time while watching the engine at the show to think about what we could do. It was close enough to drive back each night if we wanted to, but other shows were not so convenient, and there were other considerations such as showers and toilets. Of all the shows we attended, only Nuenen provided decent showers and toilets for exhibitors, at all the other places you either brought your own or had a wash out of a bowl, in water heated in a kettle, it was that bad!

The following year we stayed in a hotel, and things were starting to gel in terms of what we needed, but we still hadn't really got the impetus to get started.

That summer, one of our Stationary Engine Forum members started a discussion on the subject of a drawbar trailer, and that was what got us off on the road to building our own. I had some sketches that I had made, and over the next few months I started to form a vision of what I wanted and started to draw it out properly. We have a CAD system available at home, so it wasn't long before I had produced a set of outline drawings of a 6-wheel turntable drawbar trailer, with housing for the engine in the back half and living accomodation for us in the front.

What we built is shown in the picture below, photographed at the Hook of Holland on its return from Nuenen after its maiden trip.

15/09/10

We started with a concept outline drawing, fixing the main dimensions, getting a feel for the mechanical layout and sorting out how much room we had available for us to live in. Another thing that was affecting what we were doing was impending leglislation in the UK for trailers. We understood that all trailers would need Type Approval, to be compliant with EC regulations, and that included home-built as well as commercially built.

We had at that time already bought new axles, wheels and tyres for a new standard 4-wheel trailer, so we had the basics already, we just needed to buy an extra axle and wheels. The body we thought could be done by a local coachworks, but we were to be disappointed on that score.

24/11/10

By November 2010 we had started to buy the parts needed for the construction, a 3.5tonne trailer coupling, the extra axle and so forth. The design of the chassis was well advanced by now, the front axle pivot having taken a fair bit of time to think through and draw up, and the chassis components were starting to be weighed as we added them:

We hadn't thought much of what was going to go in the front as yet, but around Xmas 2010, we started looking out for kitchen bits and pieces, plus we wanted a fridge and toilet. While these were available commercially, they were fairly expensive if bought new, and we were looking at secondhand caravan components to keep the costs down.

We found an ideal kitchen assembly, but it was in Perth in Scotland! Nonetheless we had to go to Inverness with the trailer for our company, so we called at Perth on the way back and collected it. Later on we were to sell this set and buy something else......

25th November 2010, we ordered the steel, half a ton of box section from Parker Steel, delivered to our metalbashers who are going to weld up the chassis. I hoped to be there as well, getting my hands dirty and perhaps getting to grips with our own 260amp MIG welder, it would be a useful bit of experience for me, and our youngest son, Philip, who was already proving to be very handy with the welder.

Cost with VAT and delivery was 616.08.

75 X 50 X 3mm - 2 lengths Floor cross-beams
120 X 80 X 5mm - 2 lengths Main chassis rails
100 X 100 X 4mm - 1 length Stiffeners, one each end and two at the step in the frame
100 X 50 X 5mm - 1 length Drawbar and axle frame for the front

All the while, the Forum discussion was going on, with loads of input from interested members, so I had plenty of advice and thoughts on the subject!

12/01/11

The front axle centre pivot took some thought. It had to carry the weight of the front of the trailer, while doing the steering as well, plus braking. Traditionally it is usually a ring thrust bearing, bolted or welded to the chassis and axle, but we found the costs to be very high, and so we looked at an alternative. We finished up with a vertical steering pivot, carried in three large bearings bolted to the chassis. Two of the bearings would carry the radial thrust of the pin and a third would carry the vertical or radial thrust. Fortuitously, we found the two large pillow-block bearings on ebay, and the other thrust bearing came from a bearing supplier.

The steering pin was housed in the axle pivot frame in a circular housing, bolted to a heavy box-section housing that carried all of the loads on the axle:


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