Enhancements

Ideas for modifying a rampaging chariot

The rampaging chariots guild created the rampaging chariots that you have built to interest you in engineering. Now it is your turn to engineer some modifications of your own!

If you are unsure about anything in this guide, or you have an idea for your own modification but are unsure if it would be allowed then please contact the guild. Any modifications that are judged to be unsafe on competition day will not be allowed so please avoid disappointment and get in contact. Don’t worry; we won’t pass your ideas onto other teams.

Remember the most important thing is to have fun!

Basic improvements

Create a lid for your chariot to improve its looks in competition

Could you make your robot have an interesting theme?
Could this be based on something special to your school, ATC Sqn or club?
What materials will you use?
How will you make sure that the removable links can still be accessed quickly without the need for tools?

Estimated cost: Materials - £10

Create a fixed scoop to allow other robots to be lifted up

Can a scoop be added to the front of the chassis without drastically modifying the chassis design?
What materials should the scoop be made from?
Should the scoop be flat, curved or two or more large forks?
What are the advantages of each design?
How best to implement the design?

Estimated cost: Materials - £10

Prevent the robot running out of power during competitions

The NiCad batteries supplied are 18v and 1.2 Ahr. These are fine when brand new, but deteriorate significantly over time. Our Science Festival Rampaging Chariots are fitted with 18v 8Ah Sealed Lead Acid Accumulators which last much longer.

Either connect a 12v and a 6v Sealed Lead Acid Accumulator in series to obtain 18v, or connect three 6v ones in series. The batteries must be capable of delivering a high current so some security system batteries are not suitable. The batteries must have a similar specification (and normally the same make) to avoid incompatibilities when connected together. Three similar 6v batteries are technically the best configuration, but the 12v + 6v is cheaper overall and works fine.

Remember you will need a charger for the batteries. A stabilised Laboratory power supply capable of delivering up to 24 volts is recommended. The recommended ‘Bulk’ charge current should be 10% of the Amp-hour rating of the battery. This means an 8Ah battery will charge at 0.8 Amps for about 10 hours.

In practice a high current battery can be charged at a higher current. I set my charger at a maximum of 20.7 volts and a maximum of 2 Amps. The battery starts off charging at 2 amps and as it fills up the current gradually reduces to about 100mA when the battery is fully charged.

Due to the high current capability of this battery (which can melt screwdrivers) I recommend you insert a 20 Amp car type fuse in series.

The batteries cost £20.70 for the 12V model (order no. 18-1104) and £13.70 for the 6V model (18-1100) from Rapid Electronics. They also do an educational bench power supply that is great for this purpose and other things - order no. 85-1705, cost £69.

How are you going to fix the batteries to the chassis as they are quite heavy?
How are you going to connect two boards to one battery including a safety plug/link?

Estimated cost: Materials - £ 35

Intermediate improvements

Modify the shape of the chassis to allow it to be better suited to the competitions

What are important attributes that a robot must have to win a competition at the Scottish Robotic games?
Look at various different shapes. What are the advantages and disadvantages of each, i.e. box, wedge, circles, triangles etc?
Once a design is chosen should you make a neat scaled drawing and then make the new chassis out of cardboard to test if the components will fit? Or jump straight in with new materials?
Analyse the new design, is it suitable for the Scottish robotic games? Will it stand up to the rough and tumble of the competitions?
What will you do if the new design has a flaw?
How will you manufacture the design?

Estimated cost: £20 for new materials

Create a passive (unpowered) movable scoop to allow other robots to be lifted up

Can a scoop be added to the front of the chassis without drastically modifying the chassis design?
Look at the football guides, could an axle be run through them with a scoop attached?
What materials should the scoop be made from?
Should the scoop be flat, curved or two or more large forks?
What are the advantages of each design?
How best to implement the design?
Remember the maximum protrusion in front of the main chassis is 50mm

Estimated cost: Materials - £15

Make an LED display on your robot

What makes LEDs special when wiring them up? Hint – positive and negative terminals and safety resistors.
Would you be able to spell out your School initials, ATC unit or club name in LEDs on your robot?
How many LEDs would you require for your design? Remember you don’t have to think huge, a small display can be just as effective.
How would you wire the display into your robot so that the display lights up when you connect your removable link?
Please be aware that any LED displays must not flash or use exceptionally bright LEDs for health and safety reasons.

Estimated cost: LEDs and resistors - £5, Breadboard - £2

Advanced improvements

Convert the Rampaging Chariot to 4 wheel drive

How can you connect the wheels on each side mechanically?
How can you ensure the motors are fixed firmly enough to the chassis so that they transfer power to the other wheel without bending out of line?

Estimated cost: Connection chains/cogs/belts/wheels - £30 depending on method

Make tank tracks to give increased grip

How do tank tracks work and how do they stay on a tank?
How will you make the tracks? For example, pulley belts with a groove carved into the wheels of the chariot, tracks from toy models etc.
What method will you use to design the tracks?
How will you manufacture the tracks and associated parts and what materials will you use?

Estimated cost: Large rubber belts - £15 or Model tracks - £100

Create a powered movable scoop to allow other robots to be lifted up

Note – Any powered scoops MUST follow the rules below or they will not be allowed to compete
The scoop must only be powered by electric means, e.g. a motor attached to a threaded rod to work as a linear actuator. No pneumatics, hydraulics or other methods will be allowed.
The scoop must have a safety break in the circuit to allow the scoop to be completely isolated.
The robot must be fitted with a non flashing LED indicating if the scoop is active.
If you are unsure about your design then please get in contact with the rampaging chariots guild to avoid disappointment at competition time.

Can a scoop be added to the front of the chassis without drastically modifying the chassis design?
Look at the football guides, could an axle be run through them with a scoop attached?
How will you power the scoop?
Research linear actuators, how could you make one and fit it into the robot?
What materials should the scoop be made from?
Should the scoop be flat, curved or two or more large forks?
What are the advantages of each design?
How best to implement the design?

Estimated cost: Raw materials - £15, Drill motor - £10, Threaded rod - £2