Archive for March, 2009

Started Construction of Tri-Bottle Cluster Booster

Sunday, March 29th, 2009

Now that I have finally come up with a relativly easy method of butt joing bottles, I sat down this weekend and made another two butt to butt joined sections. I have that it is extremely important to make sure that the holes in the bottom of the bottles are perfectly central, otherwsie the ridges on either bottle will not sit together properly. This will in turn mean that the actual centre of the bottles are not touching and thus your little piece of threaded rod, will not be long enough.

Now that I have 3 completed sections, I can start to construct the bottom half of our new rocket, which will be a booster cluster comprised of 3xrockets. For demonstration purposes I have held the 3 sections together with elastic bands.


You can see I have placed the staging mechanism on top of the boosters. There will probably be another section inetween them, which contains the electronics and parachutes for the booster section.

Pressure Switch – Part 4

Sunday, March 22nd, 2009

After trying many times to get a working air tight pressure switch using the brass components in the previous post, I decided that it wasn’t going to happen. So I set about trying something new.

I stumbled across this on the Yahoo water rocket forums:-

I decided that this looked like a very reliable method of making a pressure switch. The only down side is that it needs to screw onto the top of the bottle, this means that you need to join the bottles together by bottoms, instead of the normal top to bottom arrangement.

I am glad to see, as you can see below that the new switch works really well and there is no sign or any leaks. The switch operates at about 20psi, slightly higher than the previous design, but probably due to the slightly thicker rubber.

Pressure Switch Part 3

Tuesday, March 3rd, 2009

After a rather large break from building rockets I have started to start design and construction for the competition this summer. Whilst I was buying the parts to make more robinson couplings, I saw some other brass components which I thought could be used to make a working pressure switch.

Brass Components Brass Components

The micro switch is clamped onto the two flat brass circles shown above. A balloon is held in between these two brass circles. In theory when the pressure builds up in the rocket, the balloon should expand through the hole in the brass circles and press the micro switch.

The idea is to use the parts to make a pressure switch that can just screw onto a robinson coupling as shown below.

End of Bottle showing coupling Pressure Switch Attached to bottle

Good news first, it works, the micro switch engages at around 15-20psi. Only problem I am having however is the classic problem of making it airtight. After about 40psi there is a notable hiss of air leaking. I will continue to work on it, using some rubber washers and sealent to try and make it air tight.