Vintage Thing No.117 - the SKR Imp-powered outfit

Stuart runs up the SKR outfit, which is not a 4x2 or a 4x4 but a 4x3.

This extraordinary device turned up at the Imp Club National Rally on the Sunday afternoon and completely distracted me form the awards ceremony. I saw this gaggle of people onbviosuly looking at something pretty low and then heard an engine start up.

That roll bar thing at the front is actually the frame that goes under the car/sidecar/trike to lift the wheels and allow it to be started

Imagine my surprise when I saw what they looking at. It pretty much defies description but here goes.

This is how you start it

It's a racing sidecar outfit with a Hillman Imp engine and transmission. Although it has four wheels the rear two are considered to be close enough to be considered as one. And of those four wheels, three are driven.

From the side, you can see the upright Imp engine. Note the SU carb and intake arrangements. Underneath the zorst cowling is also an Imp gearbox.

It was built by Stuart King and is still not finished although it has competed on many occasions. Stuart had with him another fellow who could also answer our questions. We needed both of them there to field all the enquiries. He said he'd been fascinated with what Stuart would do next for years and had become part of the team. Apparently, Stuart's workshop is full of things that didn't work, all hung up to remind him what had happened when he'd tried something.

The final result was described by some as mad, but in a good way.

I prefer differently sane.

Understanding the transmission took some doing and Stuart had to sketch diagrams for me.

The Imp engine is wet sump but it's a very small wet sump. The water pump is driven by a short belt from the nose of the crankshaft. The single SU carb is mounted on an intake gallery made out of solid aluminium.

The 875cc Imp engine and gearbox are mounted longitudinally on the right next to the driver. The left hand side driveshaft has gone and the box is blanked off. A much sorter shaft comes out of the right hand side and is mounted at its outer end on a plumber block. This shaft carries tow sprockets, one for the rear and one for the front.

Only the left one is powered. Note the swing arm, complete with eccentric adjusters to maintain chain tension.

The rear chain drives the left hand wheel on the rear swing arm. The right hand one was originally driven but the ensemble didn't handle well coming out of corners, so the right hand wheel now has a freewheel hub to make the SKR outfit shoot out of bends very nicely thank you.

Everything is so beautifully made

The front chain runs forward alongside the gearbox to another sprocket and shaft, which then transmit power, via another chain, to the front diff, which originally lived inside the Imp box but now enjoys a detached existence in a custom made residence of its own.

Front suspension adjustment is by eccentric bronze bearings on the upper wishbones. That orangey thing just to the left of the letter A is one of them.

Mini components are used in the front driveshafts and uprights but if the upper wishbones looked as if they've been carved from solid alloy plate, then that's because they have been carved out of solid alloy plate. Lower wishbones are Morris Minor and torsion bars run aft.

This is the battery position, which can also be augmented with lead weights to make up for an absent passenger for when the SKR is used solo. Note the sifbronze welding

All steel tubes were sifbronze welded, a technique for low temperature gas welding with bronze rods, originally developed for use on cast iron but subsequent used on virtually everything except aluminium. The frame of the SKR remains unpainted, possibly because work is still ongoing but also perhaps to show the quality of materials and workmanship.

This is possibly my favourite picture of the SKR. If you look at it in close up, you will see the right one is labelled "Slow" and "Fast" with arrows in the appropriate direction for the elimination of any doubt. On the left it says "A" and "R", for advance and retard and there's a cable that adjusts the distributor on the end of the cambox cover. Just left of this ignition timing twist grip is the upright gear lever in its fore and aft gate for changing between the two gears.

The controls are very simple. Steering is by an aircraft type control stick with two twist grips. The right hand one is for the throttle. So far so good? Take a deep breathe - the left one is for the advance and retard   mechanism because there are only two speeds operated by the large tee handle to the left of the steering column. When racing Stuart adjusts the ignition so that it doesn't bog down in the slower corners rather than change gear. This is effective enough to allow him and his intrepid passenger to get around the hairpin at Mallory Park.

This is the fuel tank, which looks like it's grown into place. Apparently it's very difficult to remove.

On the day, the SKR didn't tun for long. The water pump was playing up and when spun by hand sounded a bit gravelly. This was a shame for it would have been great to see this thing circulate round the rugby club and even better to see it race in the heat of competition.