Archive for October, 2008

 

New Hand Pump

After the demise of our foot pump at the last launch day, we needed to get a new one. We decided to look for something that would reliably pressurize to 130-150psi. After looking at 12V compressor options we have initially settled on a hand pump. We took delivery today of a TOPEAK Joe Blow Ace Bike pump.

This pump has 2 pressure chambers and a switch on the top which can be set at 60psi, 120psi or 200psi. In the different configurations it switches between the chambers to allow a lot of volume on the low pressure selector or a small volume but high pressure when choosing the high pressure selector. This should allow us to pressure up to 60psi quickly, then switch to the 120psi selector to get the pressure up from there.

The pump has 2 foot rests, a hand rail, the pressure selector switch, 2 long pressure cylinders, about a 1 m hose (looks like 6mm or 8mm) and a pressure gauge up to 260psi.

Here are some pics of the pump.

TOPEAK Joe Blow Ace Pump

TOPEAK Joe Blow Ace Pump - Side View

Front View

Front View

Pressure Selector Switch

Pressure Selector Switch

Pressure Gauge

Pressure Gauge

The unit is surprisingly big, standing at approx 70cm high and when the handle is fully extended goes up to about 1.4m. Here is a pic with the handle extended, you can see both cylinder pumps clearly

Handle Extended

Handle Extended

Posted by on October 25th, 2008 9 Comments

Website Optimization

In an effort to speed up the website I have resized all the pics to be 800 x 600. This will mean that when you want to click on a picture to see a bigger version for more detail you wont have to wait so long for it to download.

Any picture in any of the posts is clickable. To see a bigger version just click on the pic to load the bigger version, hit your back button to go back to the page.

Posted by on October 25th, 2008 Comments Off

Launch Day 10

Launch Day: 10
Date: 19/10/08 Midday
Location: Montview Oval
Rockets: H2

This launch day was again to test the dual parachute deployment system. A lot of ground based testing was performed prior to the launch day on the launcher, the pressure bottles and both parachute modules, all was in readiness for launch day.

The pressure bottles were fitted with both the drogue and main chute modules and the Large Dummy PPNC nosecone was fitted. The new revision of H2 weighed in at 333g and was exactly 100cm tall.

H2 prior to launch

H2 prior to launch

The conditions were hot with almost no wind when we arrived so we setup quickly. It was a good decision to go to the park on a Sunday instead of a Saturday as there was only us and 2 guys flying remote control planes. We just had to make sure we co-ordinated the launch with them so we didn’t chance knocking one of out the sky … :)

We had set the drogue release at 3.4 seconds and the main at 5.75 seconds. These figures were based on a projected height of 250ft (simulator) and an apogee at 4.06 seconds (simulator) with a launch pressure of 110psi and 800ml of water.

Here is the result of launch 1

As you can see we were partially successful. The elastic band didn’t release from the timer on the drogue chute but the main chute deployed as intended and we recovered the rocket successfully.

We made some minor modifications to the drogue timer and setup for another launch. All was going well until a bit of wind picked up and the rocket started tilting over at about 15 degrees. The pressure at this stage was about 80psi, we stopped pressurising and waited for the wind to die down, unfortunately it didn’t, we decided to abort but it was too late, the rocket tipped over further (away from us) and the gardenia on top of the launcher gave way. The rocket took off like a ground hugging cruise missile. It went approx 40m horizontally before touching down and skidding another 15 or so metres.

When we reached it, the drogue had deployed (at least that worked), one of the fins had broken away from the RFA, the upper modules were full of dirt and the top of the dummy PPNC had popped out. It looked ok, we gave the timers a quick test and they seemed ok as well. At the launcher the top gardenia fitting had come away.

All these items we fixed onsite within about 20 minutes, cleaned the wrocket up and filled for another launch. We waited until there was no wind before placing the wrocket on the launcher and pumped quickly to fill it before the wind picked up again. At 100psi the foot pump broke (internally) so we launched at 100psi, the timer settings the same as the first launch.

Flight 3 crashdown

Flight 3 crashdown

Unfortunately none of the chutes deployed, they didnt even look like doing so.  IT looked like the main chute door was open  but the crash may have caused this and the drogue door was closed. With the wrocket unflyable, the pump broken and the temperature quite high we decided to to call it a day.

Things we learned

  • We need a launch rail … our wrockets are getting taller and they have a lot of surface area for the wind to act on. So for safety’s sake we will build a rail.
  • The reliability of the side deploy is not good at the moment but we will persevere. Its possible the cruise missile crash loosened the timer attachments enough for them to fail on our last launch.
  • Our preflight testing of the pressure bottles was worthwhile, no leaks were encountered.
  • We may look at a 12V pump to replace the foot pump

Posted by on October 22nd, 2008 2 Comments

Accurate Water measurements

Our measuring of water fill on launch days are not as accurate as they should be, they are probably with 50ml at best. Easy solution to this was to get a 1.5L bottle and mark on it the exact water levels for different water volumes. Having accurate scales makes this much easier.

First put the empty bottle and funnel onto the scales and reset to zero. This negates the weight of the bottle and funnel so that the scales will only show water added to the bottle. Pour in the water to the desired levels and mark off on the bottle.

We usually use 700ml and 800ml for our 2.5L rocket so we marked these plus a couple of others.

Water Fill Bottle

Water Fill Bottle

Posted by on October 20th, 2008 Comments Off