Archive for the ‘Launch Days’ Category

 

Water Rocket Car MkXI – Launch Day

Even though it was a cold and slightly rainy winters day here, we were very keen to try out the Green Hornet with its new configuration, so we had a lunch day on Sunday afternoon.

The new rear end fins and low traction wheels were designed to make the water rocket car act more like a rocket for stability rather than a car, ie: The rear fins straighten the back of the rocket car. This means the rear fins need to overcome the friction of the rear wheels to effectively straighten the rear of the car.

Sounds good in theory .. time to try it out.

New Rear End of Water Rocket Car

Here is the video of the launch day. We managed only 2 launches due to the rain. We also had a father and his son on motorbikes stop to watch our second launch, that’s the noise you can hear in the background.

Results
Well we had partial success in that the launches were pretty straight, especially the first one, until there was any r/c steering input, as soon as the front steered, the rear of the car had no grip to follow and just fishtailed or did a 180 degree turn.  Obvious really after thinking about it, just like doing a handbrake turn in a normal car, …. On both runs we hit the gutter, we haven’t done this for a long time, even the r/c steering couldn’t control the cars direction when fishtailing.

Positives from the tests were the rear fins look to be working but we will need to put rubber back on the rear wheels, so we will see if there is enough force generated by the fins to straighten the car under thrust with the old wheels on.

The launcher updates worked great. The lightened chassis did work well as the car definitely accelerated quicker than the last revision.

We will keep working on it :)

Posted by on July 13th, 2010 Comments Off

Water Rocket Car MkX – Launch Day

The Easter break allowed a chance to actually do some work on the water rocket car and to upgrade the car to test some stability ideas we have been working on. These include

– outrigger rear wheels
– rear wheels rear of the nozzle
– larger rear wing
– bottle alignment guides

All of these design changes added a bit of weight to the car but we wanted to test for stability rather than just increase distance. What we were after was a straighter launch

We also had a small update to the launcher with the addition of a 20L container to hold 20L of water to hold the launcher down and reduce recoil. It also doubles as a good water supply for rocket fuel :)

Here is the video of the launch day

The longest distance recorded was 87m but that was uphill so over 100m on the flat isnt too much trouble even with the extra weight. We were happy with the results of the stability upgrades with the last 120psi run going straight up the middle of the road.

We will do some more work on this model before we build the next one, there are a few more things to test yet. Hopefully the next update wont take soo long

Posted by on April 12th, 2010 Comments Off

Water Rocket Car MkIX – Nighttime Launch

Before the details of the night time launch, a few modifications to the steering were performed. These included

– Reconfiguring the transmitter to reduce the travel distance of the servo, both left and right
– Adding a physical limitation to stop the front wheels from being able to turn to full lock

The overall effect was that the steering is not as sensitive. Here is a pic

Steering Update - stoppers

Steering Update - stoppers

A 7mm nozzle reducer disc was added to the nozzle and tested up to 60psi prior to launch. We also used for this launch 5 x 3L bottles of water for the weights on the launcher (approx 15kg)

Night Time Launch
One good thing about the new test track we have is that it is lit at night. So after making the alterations I decided to go by myself and give them a test. Here is a pic of the track. Its lit well enough to see the car but not really well enough for video. Here are a couple of pics,the light was a little better than the pic shows.

Test Track - lit at night

Test Track - lit at night

Water Rocket Car and Launcher at night

Water Rocket Car and Launcher at night

Launch 1 – 1000ml (foam) & 100psi
Unfortunately when the car was pressurized to 100psi it started to leak out of the thread side of the nozzle. We went ahead with the launch anyway and the rocket car went fine, distance about 77m. However trying to fix the leak on site just wasn’t happening, tried extra teflon tape, closing the nozzle tighter with metal grips … it still leaked. So we aborted that launch and just removed the reducing nozzle and pressurized again. No leaks ..

Launch 2 – 1000ml (foam) & 120psi
This launch was at 120psi uphill and the car went very well, it actually stayed within 1 cars lane width the whole way. I measured out at 107m by foot (no long measuring tape yet so just a personal record at the moment)

The launcher and equipment was moved up to the other end for a reverse run to see  if we could beat that distance with the slight downhill run

Launch 3 – 1500ml (foam) & 120psi
We added a bit more water this time and pressurized to 120psi again. The launch was pretty spectacular with a big looping fishtail going down the course. The rooster tail from the rocket spray made it hard to see where it was going at night so it may have been driver error that caused the fishtail :( … The distance was good though. 110m

Launch 4 – 1500ml (foam) & 120psi
Its a little hard to tell exactly what pressure this one launched at. I think it was 120psi but not sure. Halfway through pressurizing I heard the unmistakable click of a large relay going off … follow not long afterwards by the floodlights on the test track also going off … hmmm .. standing in the dark … thoughts of aborting were the way to go until I realized I could just turn the car around, point it down the track and put on the high beams … So did that and with the track lit pretty well, launched.

Again a big long looping fishtail down the course, made even harder to see with the rooster tail from the exhaust spray being lit up my the high beams headlights …. The car made it out to 98m which was ok considering …. packed up the gear and headed home.

We need to work on the leak with the reduced diameter nozzle to get the best out of this car. This should tame the fishtail

Posted by on October 23rd, 2009 Comments Off

Water Rocket Car MkIX – Launch Day

Here is the video .. more detail to come

Posted by on October 13th, 2009 2 Comments