Archive for December, 2010


WordPress iphone client

For our record attempt we would like to put live updates on
our website. We have been testing the iPhone client for a while but
it has had bugs for self hosted sites like ours. So this update
looks like it is working, as I guess you can read this post :) This
post was written and published all from the iPhone. Pic of me in
the office as a test …. Happy holidays to everyone :)

Posted by on December 23rd, 2010 Comments Off

Air Compressors

Our next water rocket car design is coming along nicely and it is already obvious that it will take way too long to pump up the bottles  with just the  hand pump. Getting the three bottles on  MkXI car up to 140+psi pressure takes a lot of effort so a lot more bottles will be a lot harder :( ….. So we  are looking at alternatives.

Here ebay is our friend to find second hand compressors  to try out.

The first compressor is a 12V compressor for 4WD tires. This didnt appear to be an el cheapo one.

Truck Air 275 - 12V Compressor 275psi

This compressor has a small fan to cool the compressor built in and will run from a 12V lighter port. We cut off the normal car tyre connector and fitted a female nitto quick release air hose connector so we could connect it to the high pressure hose and the launcher.

First we tried 1 x 2L bottle with no water and tested how long it would take to get the bottle to 120psi. Unfortunately after about 6min it only managed to get the bottle to 90psi and it cut out a few times in the process. Also its very loud for a small compressor.

Next we tried the 3 bottle stack with again no water. This time the compressor only managed 60psi before it would cut out.

While this might be good for 4WD tires at 35psi, its no good for water rockets ..  We need to crank it up a notch or two ..

Next on the list is to try a stronger air compressor with its own power source for taking to launch sites .. so we managed to find this petrol powered air compressor, again on ebay, again for not very much $$.

Pilot K17P 5.5HP Petrol Powered Dual Piston Compressor

This compressor has been decoupled from its air tank, which is what we wanted, but its still heavy ~40kg. Its in good working condition and the engine and compressor seem to work well.  There is plenty of power in the reliable 5.5HP Honda engine. We are in the process of adding a gauge and quick release coupler plus a manual safety valve, the compressor needs an oil change as well.

It already has a engine cut out which we manually tested and it cuts the engine, just not sure at what pressure yet. There is a air line from the top of the compressor pistons to an air ram connected to the engine throttle.

Air lines from the top of the pistons

Air ram connected to engine cut-out

The compressor is rated at 145psi and it has dual pistons.  It also needs a cage for the flywheel and a set of wheels, but if it gives the pressures we are after then we will add them.

We will post updates after our next series of tests. This compressor isnt for our current car so it wont effect our launch attempts using that car.

Posted by on December 8th, 2010 1 Comment