Timmi's Water Rocket Car - 2.11.2003

This is the original toy truck with the destiny to serve as a carrier for water/air jet propulsion.

Here is 8 year old Tim, proudly presenting our rocket vehicle. It is the chassis of  the truck above, enhanced with a 1 liter coke bottle, cable-tied to the back. We asked the Pink Panther to be test pilot.

The car was operated with a Gardena type launcher. A regular bottle cap was glued into the grey Gardena bit. The plain Gardena nozzle (8 mm, right) was reduced to 3.5 mm with a wooden reduction (left), made on my Unimat lathe (description here).

The technical crew, building up pressure. We used only low pressure, being so close to the vehicle. The launch was triggered with a string, off-axis to the exhaust jet.

The biggest problem was to keep the car driving on a straight line. The wheels are made from some hard plastic. The car was always skidding all over the pavement, mostly turning over several times, driven by the vast water jet force.

The first remedy was taping stones into the car front (see picture). Did not help much, except making the car heavy and slow.

Our second remedy was a rubber "coating" for the wheels: an old bicycle tube was cut into 2 cm wide strips. They covered the wheel surface well (partly removed for the photo). This increased the surface friction by much.

The rubber coated wheels were not sufficient either. So we drilled holes into the bumper bars. Then we threaded a string through the two holes (back hole shown here) and tightened it close to the ground.
The visible filings around the hole and on the trailer pin developed after some 5 starts.

The complete launch crew:
niece Clara (on  unicycle), nephew Tim (holding WR car), wife Susanne (holding guide string), husband Ulrich (holding wife).

This animated gif shows one of the launches. Tim enjoyed pulling the start rope. Clearly visible are the wild direction changes right after start, in spite of the tightened guide string.