Engine mounts and more

Right, refreshed after a week off and time for a bit of an update.


After the last update I did indeed get the motor and gearbox into the car where they remain now. It wasn’t as hard as I expected and it all slotted in beautifully as you can see from the pics below. A bit of 2×4 was used to level it up over the x-frame, ready for engine mounts to tack it in place.

This obviously isn’t the final fitting. Some holes need opening up to fit larger bolts, the welds need reinforcing (I may need a different welder – mine struggled with the 8mm steel), and it all needs trimming and painting. But this is good enough for us to begin the big game of Tetris that comes next: fitting all the components into the engine bay and making up brackets to hold them.

Motor and gearbox on crane
Motor and gearbox in position

Fuel-line removal

Before we got a welder anywhere near the front end, we needed to clear out the fuel lines. I jacked the car up onto stands again and my daughter and I got very mucky draining (not very well it turns out) the fuel lines and removing them along with the filter and any other gubbins (what even is that black cylinder next to the fuel tank?) This creates some nice space for running the future high voltage lines from the packs I hope to install in place of the fuel tank.

We haven’t removed the tank itself yet, just clamped the lines. But we did soak all the key nuts and bolts on the rear frame in penetrating oil in preparation. When it comes off, the whole lot is going to need a good clean up and a coat of paint at minimum. Diff mounts looked OK though on initial inspection, which I wasn’t expecting.

Engine mounts

We need to finish the mounting of the motor with a couple of struts to tie in to the old mounts on the cross member. Originally, I had planned to just do single struts at a diagonal from the front of the adaptor plate. But once the motor was in it became clear these might be quite awkward and uneven. Instead, having test fitted the inverter my daughter and I settled on a U-shaped bracket coming around the engine from the front plate that would allow us to do a couple of simple struts down to the engine mounts from its corners. Picture might make more sense.

This has the advantage of forming the base for the mounting brackets for the inverter and the high voltage junction box and maybe some of the cooling pumps. We set the height of the U to be right for the base of the inverter, allowing relatively easy access to the various connections – 35-way connector for i/o, AC input for charging, AC output for the motor, and DC input from the batteries, plus cooling in and out.

My daughter measured up and we cut three lengths out of 40mm box, as well as two plates from a length of 3mm strip that may once have been the mounting bracket for an IKEA float shelf. I don’t have a metal blade for my mitre saw yet so this was done slightly unevenly with the angle grinder. I think that might be a smart purchase. We tacked this all together but putting it up against the adaptor plate realised it was all a bit skewed. So instead we tacked the sides of the U to the adaptor plate as straight as we could and then welded the base piece across them. That worked a lot better.

Eventually the U will be bolted rather than welded on, but a few tacks will hold it for now while we measure everything else up.

The two circles I drilled out of the 8mm plate will form the base of the final two struts. Just need to mock up the struts themselves now to get the angles right. More cardboard engineering.

A very basic workbench setup
First part of mounting frame tacked in position


Our neighbour, Doug, dropped the coupler back round having machined down the rough nubs left from my cutting the centre out from the BMW clutch. Looks nice now. I’ll probably leave it with just a couple of welds for initial testing and then if it spins smoothly, put a seam on all the way around. If it isn’t straight enough he has offered to help me align the two clutch centres as he has the kit to do it on his lathe.

Coupler after a spin around the lathe


I chanced across a 2kw, 220v engine heater on Wish (later found it even cheaper on eBay) that might be a good alternative to my plan of sticking an electric heater core into the BMW unit. Certainly a lot less work! Does mean more water sloshing around but it will do for now and it might also be a way of warming up the batteries on a cold day. Plumbing will be interesting. Will have to step down the 350+ volts from the battery to drive it though. At least if I am to run it within specifications. Expect the heater element would be fine with a bit more juice but doubt the integrated pump would be happy.

HV Junction Box

I’ve been working on finalising the HV junction box. This is where the contactors sit that switch the DC supply from the battery to the inverter (and vice versa for charging). I have probably laid this thing out about 20 times before I finally took the plunge and started drilling holes in the mounting plate. Still it was only after I had drilled three holes that I realised the polarity matters on the contactors (they’re not just big switches) and so my planned arrangement wouldn’t work. So, two holes in the wrong places. It’s only cosmetic and I’m the only one who will see it but still annoying.

The other tricky bit about making up the junction box is connecting everything together. I figured I would have to make my own bus bars and so bought a load of 20mm x 2mm copper strip. Anyone with basic maths will realise this has slightly higher cross sectional area than the 35mm2 cables I’m using to hook everything up.

The only problem with this approach is that the contactors I bought are horizontally mounted while everything else is vertical, so my bus bars have to go through 90 degrees. I started by measuring out neat diagonals, scoring lines and trying to fold the bars along a couple of 45 degree lines to make a 90 degree bend, with a couple of other vertical/horizontal bends bringing it all back into a straight line. This worked OK but the finished result didn’t look great and it took a long time.

So, on my third attempt I just stuck the bar in the vice and tried twisting it with a big pair of pliers. The result: a beautiful smooth curve with hardly any work. You live and learn.

Only seven more to make…

Current state of junction box
Nice clean bend in the busbar
Earlier attempts at the busbar - not so clean

Engine: sold

The engine went off to Scotland this week to replace one with a terminal oil leak. Didn’t get that much for it (£110) but after it being listed for nearly a month I just wanted it off the drive. The buyer left me with some of the ancillaries to sell so that will get a few more ££s in towards the project. Still have the exhaust to go as well. If nothing else the cat should be worth a bit.

Even at that low price, the car now only owes me less than £500 plus transport, so I can’t really complain.

Next steps

While on holiday I updated my todo list for the project which spanned two pages before I got scared and stopped. But mostly focused on the big game of Tetris now: getting all the other components laid out in the engine bay and brackets/mounts made up for them all. I’d like to have that done this week so that I can pull it all out again for finishing and painting. While it’s out we’ll clean and paint the engine bay and probably give the front suspension a spruce up. Think one of the front springs is knacked so that will need replacing at the same time.

The big unknown remains batteries. I have an order in as part of a big group buy via the OpenInverter forums but it is not clear when or even if that will deliver. And I’m running out of time to get this car at least functional before my self-imposed deadline of the end of the month. So might just have to take the plunge next week and buy a small pack to get me going…

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