Water Rocket Car R/C Development

The last week or so we have been working on a R/C (remote control) addition to our water rocket car. There is much to learn it seems in the R/C world and we have been on a steep learning curve this last week. We assembled all the pieces we needed to get it working – these are

– Transmitter – Ours is a Futaba T2PH 29Mhz AM 2 channel radio transmitter (built in antenna)
– Receiver – A Futaba R122JE – 2 channel 29Mhz receiver with built in antenna
– A battery pack with a R/C connector
– A servo – we used initially a 46g servo which has 3.4kg/cm of torque

futaba transmitter

futaba transmitter

servos receiver and battery pack

servos receiver and battery pack

Initially we just did some testing of the R/C gear and this is really not too difficult to get working, 12 x AA batteries and some wires and we were in business, both servos were responding to commands from the transmitter.

In the research we did, there doesn’t seem to be a lot of talk about the range of these transmitters, so we tested what range we could get out of it. We did some testing by having one person hold the servo / receiver and battery pack and the other hold the transmitter and keep walking then every 10 steps or so turn the transmitter steering to see if the servo’s reacted. My other trusty assistant was keen to help out and would yell back “STILL WORKING” each time the steering was turned on the transmitter. We managed to walk 170m away up a hill and over the other side and it was still working, we didnt have line of sight and there was 2 large trees in the way and it was still working. We are not sure really how far it will go because we stopped the test there as I couldn’t hear the replies any more not that it wasn’t still working. So we are happy that the range of this transmitter will be fine for our present needs.

The steering was custom made – based around a simple 1 steering arm design connected to the servo. The steering arm is made of metal (steel) and can probably be replaced with something lighter like aluminum or carbon fibre but will do for the moment.The steering arm is connected to the servo via a single rod which has ball joints at each end. This allows the rod to stay horizontal throughout the servo’s circular movement

Steering Arm

Steering Arm

Each wheel connects to a wheel hub which pivots on a single connection to the body of the car. The steering arm is connected to the hub with a bolt and nut which is fitted loosely to allow movement. The nut is glued to the bolt so it doesn’t fall off and detach the steering arm

Wheel hub and steering arm attachment

Wheel hub and steering arm attachment

Here is the steering with everything attached. A second level was temporarily installed to hold the receiver and battery pack just for testing

R/C Steering Setup

R/C Steering Setup

Here is a video of the steering working on the bench. This was also our first attempt at a wide screen video … :)

We did some rolling tests of the water rocket car and had some success with it steering when it was rolling. The conclusion was that the servo is just not quite strong enough for our application. We have been doing some research and have a stronger servo in mind which has torque of 12.4kg/cm which should do the trick. Once this is ordered and fitted we will do some more trials and work up to full pressure tests ….

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This entry was posted on Wednesday, September 30th, 2009 at 12:47 am and is filed under Development. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

 
 

2 Responses to “Water Rocket Car R/C Development”

  1. George Says:

    Hi Todd,

    Very nice progress update on the car. I like what you are doing with it. :) Before you buy the stronger servo, you can double the power of your servo by halving the length of the servo arm. ie. connect your steering rod to the hole closer to the servo’s pivot point. This will increase the power but reduce the range of movement of your wheels.

    Since you are only racing in straight lines, the wheel deflection only needs to be a few degrees either side. You will also end up with finer control of the steering.

    Cheers

    – George

  2. todd Says:

    Hi George,

    thanks .. I should have thought of that .. I will give it a try .. I ordered the servo today before I read your comment … oh well … I do have bigger plans for the water rocket car so I dont think the stronger servo will go to waste :)

    -todd-