Lister 5/1 Diesel

Drawbar Trailer Design & Build

Designing & Building Our 6-Wheel Drawbar Trailer Page 24


The water heater is now re-installed and fuilly functional. We had three goes at getting the big O-ring to stay in place and seal, but eventually it went on and we could fill the system and test the pump and taps.

We fitted a new mains cable for the 240V immersion part, the original was only about 0.75mm and although electrically OK for 800W, it was a bit feeble mechanically, so a bit of 1.5mm three-core went in.

The 5-way terminal block on the right at the back is the 12V connections for the water pump and taps, NOT 240V mains! The heavy black and orange cables are the 240V stuff.

Access is a bit restricted once the shelves are in place above, but we don't need to get to it normally, in most caravans it sits under a bed or in a cupboard, it is the balanced flue type.

The bathroom is virtually finished, just the toilet roll holder to 'install' last evening and clean the tray and fit the shower mat. The two water pipes had their edges sealed a couple of nights ago.

The waste pipes go out under the chassis, and it is quite high off the ground compared with most caravans. The hand sink and shower tray go into a single pipe on one side, the kitchen sink has its own outlet on the entry door side.

I tried the Propex heater as well, but although we have lights coming on, there is no gas valve or ignitor activity, so we will take the cover off tonight and see if there is a reset button of some kind that may have tripped during shipping.


Resolved the heater pretty quickly, a quick voltmeter check at the terminals on the control box showed 13.80V (mains chargers are running) but the signal cables for the logic and ignitor boards were showing only 0.2V with no real change when the thermostat was turned up and down.

The control board carries the thermistor that senses temperature, an LM311N comparator to compare the set temp with the actual, a control relay and a couple of LED's.

The connections to the board are a little strange. Four wires come in from the control logic box on the heater plus two for 12V power.

These connect to the PCB by four screws which hold the ring terminals against the non-track side of the board, but go through the board into brass threaded bushes that connect to the track side of the board.

I cleaned the surfaces of the brass bushes and the back of the PCB where the contact pads were, then reassembled it all with a smear of Vaseline between the brass bushes and the PCB.

Once that was done, it fired up immediately and proceeded to go through its start-up purge sequence followed by a hefty click and then it lit up. Pleasantly surprised at the volume and temperature of the hot air coming out, the burner exhaust is by comparison much hotter but lower volume.

After shutting down we secured the outlet hose so that it blows into the area behind the cupboard and thus up into the living area. The fan runs occasionally to keep the burner body below a certain temperature after shutdown. Quite a decent unit. Another job done!


More jobs being done in the hot weather, but nothing major until this week when I got back onto the front LPG filler point. I had started out with zinc-plated steel piping, but changed over the 8mm copper with protective sheathing in black.

It is clipped up with rubber-lined P clips along the body supports which I drilled 4mm and tapped M5. The chassis gives it a bit of support and protection.

We also had the towbar off and repainted last week, before and after pictures:

I have taken off the 12S socket as we don't need it as the solar panels are doing all the charging we need. I have clipped up the wiring loom since I took the picture :)

And lastly our little Skrat, the stray that we found starving and injured in the engine tent back in February:

She has come on in leaps and bounds and is now probably near fully grown.


Been busy with the Ruston Dyno set, but got a few odds and sods finished:

Satellite receiver now has its own bracket and sits over the TV:

Also finished off the front filler feed to the LPG tank, and also got the BBQ point hooked up as well:

Just varnished the wood blocks that the tank is clamped against, so waiting for that to harden off before I put the stainless steel bands back on it. Also cut a piece of thick rubber mat to put under the tank to stop it fretting on the floor. The black band running right to left is the top of the chassis beam.


After a lot of faffing about with drills, I finally got the rear floor supports installed in place. To fix them to the cross-members I needed to use M10 inserts, which in turn needed a 12.70mm hole drilling. Just my luck that both cross-members had the weld seam downwards, and it was a bit tough to drill through.

These are to go under the 21mm honeycomb sections where they have no underfloor support. The engine and trolley started to bend the floor as we had changed the trolley but not taken into account the different wheel locations when the trolley and engine were on board.

Now we have full support all along the full length of the floor in the back under the checker plate runs.

I'll get some finished pictures later.


Pictures as promised, front followed by rear:

Each support spans the gap between adjacent cross-members in the chassis which were not loaded when we put the 6-wheeled 'Bomb Trolley' in there, but the newer trolley just manages to put both front and rear wheels over the unsupported floor.

Four X M10 bolts into threaded inserts. You can get a better idea of the height problem with the drills from the pictures. The cross member spacing is smaller at the back.

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