Water Rocket Car MkX – Thrust Alignment

Another small update today on the car. This update is to ensure that all thrust generated is directed out the back of the car and not slightly sideways. Removing any small sideways thrust vector ensures that all of the thrust goes toward propelling the car in the right direction and not fighting the tyres to push the car offline.

Thrust Vector Problem

The bottles are held in place with cable ties that need to be slightly loose under normal atmospheric pressure. At launch pressure (90-120psi) the bottles expand and then the cable ties hold the bottles tightly in place. If the cable ties are too tight at normal pressure they can break at launch pressure. Having the bottles slightly loose makes it difficult to know if the bottles are pointing where we want it too under pressure.

To ensure the bottles (and therefor thrust ) are pointing directly out the back of the car, two extra pieces were added at the necks of the first and second bottle. The extra pieces hold the bottles in the exact location and keep them aligned to a centre marker at the back of the car.

Bottle alignment guides - rear 2

Bottle alignment guide - rear

Bottle alignment guides - all 3

The bottles under normal pressure and launch pressure (hydrostatic test) now point directly out the back of the car.

These extra pieces add some extra weight to the car but we will fix that in a later design if this works.


This entry was posted on Saturday, April 10th, 2010 at 12:48 am and is filed under Development. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.


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