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Tornado
Basic Specs
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Series 4 |
Series 5 |
Chassis and Armour
The chassis is constructed almost universally with 1mm wall 1" box section
steel, welded together with a mig welder. Some key parts are made of thicker
wall (up to 3mm) material. 2mm thick plates are used for the front part of the
motor mounts. M6 bolts are used everywhere possible, except on parts of the
Series 4 pneumatics where M8 was required. The series 5 chassis is essentially
the same as series 4, but slightly wider, longer, and changed in shape at the
rear of the robot to keep the wheels in contact with the ground more.
For Series 4, the armour was 6mm polycarbonate (tuffak). We intend to stay at 6mm polycarbonate for series 4, but laminated with Titanium over critical areas. It is held to the chassis with M6 countersunk bolts, which screw into M6 plain nuts welded to the chassis. The access flap is held down using neodyimium magnets.
Drivetrain and Wheels
The first stage gearing uses steel MOD2 gears from HPC; a 12 tooth pinion is
fitted to the motor with a solid 5mm dowel pin, and the (machined and lightened)
48 tooth spur gear is bolted to a machined down go-kart clutch. This gives a
first stage gearing of 1:4. For series 4 the intermediate gear assembly ran on
the roller bearing contained in the go-kart clutch, which sat on a custom spacer
on a 17mm silver steel axle. This tended to move around during fights, and the
spacer wore very quickly, thus for series 5 we are changing to a longer axle
with a pair of bearings. Drive is transferred from the 16t clutch pinion to the
70t main drive sprockets via kart chain, giving a second stage gearing of
1:4.375, and thus the overall gear ratio is 1:17.5. An idler bearing is used to
ensure sufficent chain wraps around the kart clutch pinion, as it was found to
slip under stall conditions without it.
Our series 4 wheels gave us big problems (it was impossible to get the kart sprocket centred on the wheel), and are to be changed for series 5. Instead of the custom aluminium drive plate/custom machined nylon drive block/standard nylon kart wheel with integral bearing setup used last year, our new wheels use as many off the shelf parts as possible. The sprocket will be attached to a custom axle tube with a standard kart sprocket carrier, and this axle tube will use a pair of needle roller bearings on a 14mm silver steel axle. The wheel will be a standard nylon two piece kart front wheel, but without integral bearings, attached to the axle tube with a standard kart hub carrier. It will make the wheels much easier to build, and ensure the sprockets stay absolutely conicentric on the axle! As last year, tyres are racing go-kart (10" diameter), the type chosen to suit arena conditions at the event, obtained for free from kart tracks after the racers have thrown them out.
Radio Gear
The radio gear is basic and cheap; the 40MHz Hi-Tec Ranger III transmitter
coupled to the Hi-Tec 8 channel dual conversion receiver. The original 3 channel
single conversion receiver, along with the transmitter can
be modified to transmit and receive a full seven channels, and this was done
to all our radio gear (including spares). The standard 7 channel chips are used
on the circuit boards inside the units, just the extra channels are disabled! No
interference problems were found with this setup, provided we had a good aerial.
The aerial was made removable so it could be replaced if damaged, and did we
have to replace it! For series 5 we are looking at changing the aerial to make
it more robust.
Electronics and Speed Control -
Series 4
The Pulse-Position modulation signal from the modified receiver was passed to a
custom failsafe and decoder board. This checked that all elements of the signal
were correct, and we have suffered no runaways or loss of control. A custom
decoder system (using simple analogue and digital IC's, no PIC) converted the
control signals to operate the robot. The speed controller is a custom design,
using five 60 amp FETs on each leg of a pair of H-bridges, giving us 300 amps
capability. Building almost all of the electronic parts ourselves allowed us to
have fine control over the handling and dynamics of the robot, which is what
makes nearly 80kg of metal handle and respond like a good radio controlled kit
car.
The motors are the Bosch GPA 750W, the only modifications being a few welds to the casing. Power comes from three 12V Hawker SBS15 batteries wired in series to give 36V. Fork lift truck fuses (200A) are used to prevent fire in the event of a short circuit, and the removable link is made up from a pair of AMP automotive connectors, rated at 75amps each, giving us 100A continuous current capability.
Electronics and Speed Control -
Series 5
Again we will take the PPM signal from the receiver to a decoder and controller
driver box, but we hope to build proper PCBs and include all our circuitry on
one board. We intend to make modular speed controllers and build several
identical spares, given both our series 4 controller AND the half relays/half
FETs backup expired within the same week! The motors, batteries, and removable
link will be the same as last year, however the fuse arrangement will be changed
slightly (to save weight).
Weapon - Pneumatics - Series 4
The pneumatic system is based around a pneumatic ram obtained from an old
loudspeaker production line; out of the many available to us it had the largest
bore with reasonable stroke. Large bore piping was used where possible, along
with a fire extinguisher buffer tank and fast-exhaust valve. A single 5-port
valve is used to control the system, while gas is supplied from a pair of Oxygen
bottles via a custom regulator. Unfortunately we made an error on the high
pressure side, meaning we had very few shots, and thus the weapon was little
more than token.
(Taken from the Official Tornado Website)