Archive for October, 2009

 

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

Water Rocket Car R/C Development (continued)

This week we have been working on the development of the Water Rocket Car’s remote control steering and fixing a few smaller issues with the launcher.

RC Steering
We realized a more powerful servo was needed. Thanks to George for his suggestion of reducing the arm length to get more power out of the existing servo. We gave did try this but it still wasnt working well enough with the weight of the car on the wheels, it also seems to have centering issues on one side when the steering arm is connected that low. The new servo has worked perfectly since we have put it in so we will go with that, we can always use the other servo to release a parachute or pull a brake lever …  :)

The HITEC HS-985MG servo we are now using is an analogue servo which has 12.4kg/cm torque which is 3 times that of the previous servo. It weighs 62g which is a little heavier than the 46g of the previous servo, but has practically the same dimensions.

We have performed a few un-powered tests and the car seems to behaving well. Here is the video

Servo Mount & Second Level
We put together a stronger (metal) servo mount to secure the servo to the base of the car and secured the second level to the car with three screws.

New Servo Mount

New Servo Mount

The second level is to hold the battery and radio receiver above the steering arm. We decided to leave it this way to maximize space on the car for the pressure bottles. We have put a piece of wood between the first and second pressure bottles which will stop the pressure bottles from crashing into the servo or second level in case of a crash or under high acceleration.

Second Level for Receiver and Battery

Second Level for Receiver and Battery

The battery clip we had didnt have an on/off switch built in, so after rummaging through some electronic spare parts we made found a switch and soldered it  in-line so that the power can be just switched on and off without having to pull the power cable from the receiver. The switch is mounted just under the second level by the right front wheel.

Battery on/off switch

Battery on/off switch

Fliptop NoseCone
We also realized we needed some protection for the receiver and battery in case of a roll over. This was accomplished with a new extended nosecone. The nosecone is a “table tennis ball” nosecone we already had plus and extended section from another bottle. These are glued with PL Premium. The nosecone is held in place to the base by wire at the front, which allows it to flip up to access the battery and receiver without needing to take it off the car. The other end is taped to the last pressure bottle.

Fliptop Nosecone

Fliptop Nosecone

We also decided to paint the nosecone black … it looked a bit ordinary when it was clear with the glue and multiple bottles … it looks good in black. Any heat soak on the nosecone shouldn’t have a detrimental effect on the pressure bottles.

Nosecone in place

Nosecone in place

Front Bumper
We also needed better protection for the front wheels and subsequently the gears on the servo in case of a crash. We have seen from previous launches what a crash does to front wheels. We have fitted another section to the front to take the impact of a crash if the need arises. Better to sacrifice a piece of plywood than a wheel or servo. we will probably replace this with a front wing once its working properly.

General Fixes
There were a few things that needed fixing from previous crashes and issues.
– One of the front wheel bolts /bearings was bent, so we replaced it.
– The gardena quick connect had developed a leak and the 1 way valves inside them were sticking in the on position. This wasn’t allowing pressure into the bottle. When we pulled them out they had some rust on them, we decided to replace them both.
– We made a new holder for the launch string, have been meaning to do this for a while, it just makes it easier to setup and pack up the string to the launcher.
– We had a few stickers that came with the servo, so we added these to the car .. why not :)

Addition of string holder to the launcher

Addition of string holder to the launcher

Replaced Gardena Qucik disconnect for launcher

Replaced Gardena Quick disconnect for launcher

100m Here We Come
The only thing left to do now is a final pressure test for the nozzle, then head out to the test track to try some pressurized tests and break that 100m distance record we have been threatening to break for a while. Just need the weather to co-operate :)

Posted by on October 8th, 2009 Comments Off

Reducing SPAM with CAPTCHA code

Believe it or not we have been getting a lot of spam comments since we enabled our automatic translation service. Mostly Russian SPAM messages. We have filters that stop them from appearing on the web site but its a pain in the behind having to clean them up daily.

We have implemented a CAPTCHA code to the comments section now. You will need to enter the 4 character code when you submit a comment. This only takes a second to do and will stop all the automated SPAMbots from being able to add SPAM to our website.

Thanks for your support, we do love the comments .. so do keep posting …. just trying to get rid of SPAM

Now back to water rockets …… :) :)

Posted by on October 2nd, 2009 Comments Off