HHWRSA

Since we have been concentrating on water rocket cars for the last 6 months, our vertical water rockets have been collecting dust in the garage. So this weekend we have upgraded to launcher so it can be used for horizontal as well as vertical water rockets. This way we can launch the water rocket car as well as our vertical water rockets on the same launch day.

To achieve this we have  added an extra splash guard on two hinges which are fixed in the horizontal position by 2 bolts. We will replace the nuts with wingnuts to allow easier removal.

Extra Splash Guard on hinges

The extra splash guard has a slot cut out for the launch string to feed through in horizontal launch mode.

Splash Guard slot

Here is the launcher in the horizontal launch mode with its height adjustable gardena quick connect.

Launcher in Horizontal launch Mode

A support rod was cut and bored through the centre to allow a bolt to fit in it. A correct sized nut was then countersunk and apoxied into the top of the support rod.

Support Rod with nut embeded

The support rod clips onto the launcher when not in use

Support Rod stored while not in use

When the two botls are undone from the bottom of the launcher and the splash guard is moved to the vertical position, the support rod fits into a 22mm countersunk hole in the underside of the splash guard. A screw then holds it solidly in place. Here is the launcher in vertical launch mode.

Launcher in Vertical Launch Mode

The launch string is moved to  accommodate the vertical launch through a 90 degree bend.

Launch string moved for vertical launch

It takes only a couple of minutes to swap from one launch mode to the other. The 20Litre water container is used in both modes and keeps the launcher firmly in place.

Due to the extra length of our new “Green Hornet” water rocket car, we need to do some updates to the launcher. The updates needed are

- Lengthen the distance between the quick release and the launcher
- Make the quick release height above the ground variable

We have different rear wheels on the Green Hornet which has changed the height of the nozzle above the ground. The old launcher was setup with the quick release at a specific height to match the rocket car. So as we try these wheels and experiment with other lighter wheels, we need to be able to quickly adjust the height of the quick release.  Its important the quick release mates well with the rocket nozzle otherwise it will leak under pressure

Launcher Mated to the Green Hornet

As can be seen from the pic above the length of the hose to the quick release has been increased by about 30%. There is plenty of space between the new rear wheels and the launcher. The hose is kept rigid by being cable tied to a steel rod under the pipe.

Launcher hose strapped to steel rod

The steel rod is bolted to the movable section of the launcher.  The heads of two hex bolts (ready for 4 when I find another 2 bolts) run in metal channels (old curtain rod) up the face of the splash guard. Wingnuts on the bolts enable the movable section to be positioned and tightened at the location required.

Closeup of movable section of launcher

A hole was drilled in the movable section and a channel cut out of the splash guard for the launch string to be fitted. The launch string will work freely at any height.

Launch string groove

Here are a few more pics of the launcher mated to the “Green Hornet”

Launcher mated to rocket car

Another pic

Close up of mated quick release connection

The launcher and the new rocket car are finally ready for a launch day. We also have three reinforced bottles almost ready to swap in if hydrostatic testing goes well.

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

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

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

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

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

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

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