Chassis and Drive Train

The Chassis is built entirely out of 3mm thick 25mm square steel box section. It is a MIG welded ladder frame construction providing the superstructure for supporting the 6 wheels, 3 down either side as well as providing the mounting for the gearboxes and motors. To put this strength in perspective, Tornado is made from mostly 1mm wall thickness steel. The robot actually has sloping sides and thus there is another horizontal run of box section outside the bounds of the photo above.

The wheels all sit on EN24 solid steel axles 20mm in diameter. They are supported at both ends inside the chassis section in steel bushes. The front two pairs of axles are stationary. The wheels are custom machined aluminum hubs with a carboxylated nitrile rubber tyre bonded onto them. The hub then contains two large bearings which allow the wheel to rotate on the stationary axles. EN24 steel 3/8 pitch sprockets take the power from wheel to wheel as you can see in the picture above. All drive train components are through hardened EN24.

The rear wheels are driven directly from the gearbox on a keyed 20mm EN24 axle. Each rear axle is supported by 4 bearings, themselves contained in solid blocks of steel roughly 80mm high, 25mm wide and 30mm long. Drive is then taken from the rear axle through the wheel and sprocket onto the free-wheeling front wheels. Following trailing at Robot Wars Extreme we are looking at replacing the rubber compound on the wheels with something even more grippy. There are a number of options we are exploring including quartz impregnated Vulcalon and spiked wheels.

The motors that we are using are Lynch LEM130's. They are 130mm in diameter and at 36v and our current limit will produce a peak power of 8.8hp each. They have been strengthened in the factory for our use and can be run at 48v in Battlebots should we choose. The motors are clamped into place on the gearbox plates to ensure they don't move during the high impacts that are caused during driving. The end of the motor shaft is supported in a bearing on the far gearbox plate to avoid having the shaft cantilevered. This then drives through again an EN24 through hardened gear a single stage reduction, and then on to the rear wheels which are driven directly through a keyed 20mm steel axle.

Using the LEM130's has enabled us to be far from a boring passive wedge. The robot hits its top speed almost instantly allowing it to fly around the arena and strike opponents before they have realised what is happening. Compared to Growler by competitors, interviewers and crew alike, its certainly great fun to drive around the arena power sliding about ! The only problem is that there is so much power that once the wheels start spinning they soon (takes about 1 second) start to produce plumes of white smoke. It looks very impressive when it does it (as long as you realise its not the robot on fire !), but is irritating for the driver !

For a video of the drive train being tested at the Kettering Live Event - click HERE (.mov format 2Mb in size)

Upgrades for Robot Wars Series VII

By moving to stronger materials we have been able to drastically reduce the weight of components whilst keeping the same strength. Our EN24 gear train has been replaced with a case hardened EN36 gear train - keeping the same ratio, and just losing weight as a result. Likewise we have replaced some solid steel bearing supports with 7075 aluminium.... 7075 is used extensively over Storm II now to reduce weight. The wheels which did run on 20mm solid steel axles now run on a mixture of 6-Al-4V titanium axles for the main drive, and 7075 Aluminium for the rest.

The 6082T6 wheels have been replaced with super light 7075 CNC'd wheels and the rubber which we ran at Extreme II which was far too hard (stripped the paint of surfaces) has been replaced with a 60 Shure Vulcalon - its very very grippy and resists oil and wear very effectively, very very suitable for running on robot wheels

On the right you can see a CAD model of the rear drive wheels. Machined out of solid 7075 aluminium, they carry as 20mm 6-Al-4V (Grade 5) titanium axle with a 6mm keyway. These wheels are directly driven off the gearbox and the sprocket attached transfers power to the middle and front wheels

Contrary to speculation we havn't moved away from LEM130's for drive, the power to weight ratio that they offer is just too good. They are three times as efficient in a power to weight sense as an Etek for example. They only weigh 3.2Kg and in Storm II deliver around 9hp each [peak]. The gearboxes have been totally re-made in order to create the space inside the robot for Storm II's primary weapon.

We were lucky that when we first built Storm II everything (whilst all designed in CAD) was just thrown into the box, meaning that there was plenty more optimisation of space and weight to be done in order to fit in the weapons system.

If there's one thing that Team Storm have learned, its the importance of testing a design, and not rushing into a solution. Previously we have been very quick to jump to a solution because it seems like the right thing to do at the time. Now we try to take a far more considered view to Storm II (which we have declared a 'no bodge area'.... you'll be hard pushed to find any gaffa tape in Storm II these days !

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