Thursday, 17 January 2013

Finishing off the Generator Install

It was hovering around 0°C in London over the last few weeks, and when it hasn't been cold, it's been raining, neither of which are conducive to enthusiastic working. How I long for a heated workshop with a 4m roller shutter. Nevertheless I managed to don three jumpers and do some small jobs on the Jim, the first of which was to change the latch holding the generator locker shut.

In itself the job only took about 45 minutes, but the series of jobs leading up to it have taken considerably longer and were spread out over a couple of years! As you can see in the photo below, when Jim was passed into my care there was a sizable space on the nearside of the chassis that was not used for anything. The front section is used for the exhaust silencer, starter batteries, air dryer, and primary air tanks, but behind it was about 700mm of unused space.

Jim - An armoured Brinks Mercedes Atego 1823

On the offside, the space was smaller, and in it I fitted an auxiliary fuel tank, but on the nearside I decided to fit a generator; not in anticipation of regular usage, but more for use in emergencies to charge batteries, or run power tools. There are numerous things I would have liked to have fitted in the space including leisure batteries, a water tank or a storage locker; it is always best to keep the weight as low as possible on a vehicle to improve stability and handling, and so storing the 400kg  leisure batteries would have made sense. However, having a noisy, smelly combustion engine inside the living compartment made the least sense to me, and so the decision was made to fit a generator to the chassis.

I wanted to avoid buying a petrol generator, partly because the longevity of small petrol engines is not great, but mostly because I wanted to avoid carrying petrol around with me. Jim's engine runs from diesel as will the heating when I get round to fitting it, and so it made sense to me to use a  generator which uses the same fuel. The auxiliary fuel tank for running the heating and generator is around 250 litres in capacity, and so it also seemed rational to make use of it. With this decision made I set about looking for a diesel generator, small enough to fit between the nearside chassis rail and the side skirt.

I found several manufacturers of small diesel generators, designed for use in vehicles or boats which would have fitted. A few of them had remote starting, the ability to use separate fuel tanks, and a great degree of silencing. Unfortunately all of them were prohibitively expensive, and so I settled on a Yanmar engined plant generator, A Pramac P4500 which I got brand new, for about a third of its RRP. Below is a stock photo of how it looked when I bought it (I forgot to take any photos).

Pramac P4500 prior to fitting to Jim the overland motorhome

The space I have available is restricted in width by the side skirt-supports, in depth by the distance between the nearside chassis rail and the side skirt, and in height by the need for the generator to fit through the side skirt for maintenance. I fitted the largest locker door that would fit on the side skirt, and took a punt that I could make the Pramac generator fit.

Hatch fitted to side skirts to provide access to generator

The first thing I did to the generator was remove the fitted fuel tank, as with the generator plumbed into the chassis mounted auxiliary tank it would no longer be needed. This took care of the height issue and allowed the generator to fit vertically through the hatch that I had fitted in the side skirt, albeit with barely enough clearance to squeeze a gnats testicle down the gap.

To allow the generator to fit through the width of the hatch, more aggressive butchering of the brand new generator was required; chiefly, removing the tubular steel carrying frame. Most of the tubular steel frame is simply there to make the generator carryable and add a bit of job site protection, neither of which is necessary when the generator is permanently fitted underneath a truck. However the bottom side rails do add stiffness to the frame on which the engine and alternator are fitted, and so I had to weld in a replacement frame to retain the stiffness and give something to hold onto when the generator is removed for servicing. Even the smallest box section would have added too much height and width to the generator, and so I made a simple frame out of 1/2'' square bar.

With these modifications made, I welded a frame to be fitted to the chassis of Jim, on which the generator would perch. The frame was a two simple L shaped brackets, welded out of 75x50 box section, with an 8mm treadplate deck between them  (I had some left over from patching up holes in the floor) and gusset plates reinforcing the corners. The frame was duly bolted to the chassis and I thought that  my work was done.

Pramac P4500 fitted behind batteries, air drier and air brake tanks

Sadly, on refitting the side skirt to the truck, it became apparent that I had missmeasured the height at which the generator should sit, and with the clearances being so tight, the generator was now 40mm too high to squeeze through the hatch in the side skirt. You can clearly see the scale of my missmeasurement below.

Pramac P4500 fitted to overland motorhome chassis

If removing and refitting the side skirt wasn't such a pain, I would have left it as it was and accepted that to service the generator I would have to take the skirt off, but this would turn a 2 minute job into an hours work each time the generator was serviced and so I made the decision to redrill the frame to sit 40mm lower. Of course this meant I had to remove the side skirt again, lift off the generator (100kg+), unbolt the frame, and make the necessary modifications.

When I started this job, I had presumed that the modifications would simply involve redrilling the frame, welding up the old holes and cleaning it up, but as is always the way, it took far longer than expected. Having not foreseen the measuring mistake, and to make the frame neat, I had cut the tops off of the vertical sections of the L-frame a few cm above the top holes. When I marked out the new holes to be drilled, i realised that the top hole would be hanging over the edge of the frame, necessitating the lengthening of these sections. With an extra 40mm of steel welded to the top of the frame and the holes redrilled, I repainted the modified sections, refitted the frame and generator to Jim, refitted the side skirt and began to think about how I might celebrate the completion of another successful job.

Pramac P4500 fitted to overland motorhome chassis

 Predictably, my celebration was cut short as I realised that the rectification of one problem had created another, YAY! The single compression latch that holds the locker door shut, now fouled on the frame of the generator, sitting 40mm lower than it had. To avoid having to remove the generator, modify it's frame, and cut a slot out of the treadplate, I ordered two new latches and fitted them to the side of the door where they wouldn't hit the generator.

The keen eyed amongst you will also notice another change in the image above showing the repositioned generator. One of the consequences of shoehorning a large generator into a small space, was that once the hatch was closed, there was insufficient clearance for a plug to be permanently wired into the generator socket. Until I fit a remote start button, the generator needs to be started by opening the hatch and using the ignition anyway, and I so I could feasibly just plug an unplug the power cable as necessary. To save the additional hassle, I replaced the socket on the generator with a hardwired cable run through a gland on a blanking plate, and wired the power cable onto a junction box fitted to the truck. I made the wiring simpler by running the 12v power to the lift pump through the same conduit and junction box. It is easy enough to disconnect the generator for maintenance using a connector block in the junction box, but if I wanted I could easily retrofit a socket and use it as a trailing lead.

Pramac P4500 hardwired using blanking plate in place of 16a socket

The final job to patch up the hole for the old latch on the locker door is still outstanding, but with that exception, the fitting of the generator is now complete.

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