The Swedish Surprise

Owner: Anthony (Team Grecet Racing)
Description: "The Swedish Surprise" spindle drive, 4-stroke engine, custom frame scooter


The Swedish Surprise is powered by an original cast-iron single cylinder "Suffolk Punch" mower engine, around 75-100CC, 4-stroke, somewhere between 1.5 and 3.5 horsepower.

The wheels are 7" steel-hub, solid rubber tyred wheels, off a trolley of some sort. They are spinning (no bearings, just lots of grease) on a 1-inch steel rear axle, and a 10mm steel front axle.

The front fork is from a small child's bike. The handlebars are bodged together from the Suffolk mower bars. The frame is welded from heavy-duty 30mm box-section steel, in a fishbone arrangement, with a 7-ply, king size wooden grip-taped footplate.

The engine sits on a steel plate, attached to the frame by two steel hinges. This allow it to tilt from left to right.
The large grip-taped pedal on the left of the scooter tilts the engine to the right when pressed, and thus pushing the drive spindle onto the wheel.
The presence of the clutch allows the scooter to stop with the engine running. Starting from rest by engaging the clutch is possible but not recommended, since the rubber sheath on the roller wears thin quickly (but can be replaced)
The bit of frame that the clutch is attached to has broken off once before, but was welded back on a bit stronger.

The spindle is made from a soft steel bicycle trick nut. The grippy pattern on the steel soon wore off (due to the hard rubber wheels) so the trick nut is now sheathed in a tough 5mm thick rubber tube to give more grip in dry weather.
I tried grip taping the spindle but the tape just flew off in 5 seconds.
Total spindle diameter (with new rubber sheath) is approx 4 to 5 cm.

There are two bicycle brake levers on the handlebars. The left one controls the front caliper brake, and the right controls the throttle. There is a large grip taped clutch pedal at the front left of the footplate. Engine can be stopped by pushing down the springy stopper (situated on top of the engine) that shorts the spark circuit.

Performance - The bit you've been waiting for!
Minimum speed, clutch engaged: 4mph
Maximum speed: 16 or so mph
Stopping distance at 16 or so mph: 20-30 metres

The engine leaks oil, because the two halves are pushed apart slightly due to clutch operation.
The fuel gets spilt everywhere, because there is a hole in the filler cap to allow air to enter the tank.
The Swedish weighs a ton.
The Swedish stinks of petrol.
The brake is not as effective as I'd like
It's quite loud, but not as loud as most 2 strokes.
The 4-stroke engine isn't as powerful as I'd like.
It's very wobbly sometimes.
It won't stand up on its own. Needs stand.
It rusts.
The handlebar upright has broken once before, and I had to replace it with a solid steel bar.
The wheels will wear down
The rubber spindle sheath wears down

Advantages of the design
The large wheelbase and huge size of the footplate allow the Swedish to carry two people at once, but only up to 10mph.
The clutch allows it to stop with the engine running
The rubber roller sheath is replaceable
There is plenty of grip between spindle and wheel, and the amount of grip is variable
There's a reasonable amount of engine braking to aid stopping.
It's great fun!

Future improvements:
Just make a new, better vehicle.