Slippery Strana's Shell

The Shell - or 'Hood' or 'Lid' or 'Top'
The shell was the part of the robot that would define it. Nothing less.
Whatever form the shell took would BE the robot as seen by everyone but ourselves.

Our first shell was going to be made of clear or slightly smoked polycarbonate - you know - that bullet proof material that protects bank clerks. We got very excited (alright, I got excited) at our first attempts to design and buy it. Faxes flew here and there and we wondered which side of £100 the bill would be. Unfortunately (or with hindsight, thankfully), the moulding company that was to bend our masterpiece into shape went bust, luckily before we had sent them any money!

We looked hard and fast for some alternative, but the likely companies were all way up country somewhere. It was looking bad for our robot top, and hence also for our chances of actually fighting any battles.

The Rescue
Then - to the rescue came Matrix Mouldings of Bristol, introduced to us by Jeremy's Dad Steve. Steve had been speaking to one of the Partners of Matrix Mouldings, Peter Finch, and he offered to look at our specifications. He felt sure his crew, Wiz, Charlie and Justin could help us out.

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A tentative 'phone call soon confirmed this. 'A robot eh?. No problem'. In fact they were keen to help and Peter Finch invited me along to discuss possible sponsorship (which was eventually successful of course).

So I popped into their offices in Bristol with the bare Slippery Strana to discuss sponsorship and to make some measurements, and in a short while Wiz and Charlie (their Charlie) and I were discussing things like continuous-fibre glass cloth, resin curing time, resistance to penetration, and even the bullet-proof vest material, KEVLAR. Very exciting.

Go Make A Mould
We agreed that Slippery Strana's shell was not going to be a trivial job, so Wiz and Charlie asked us to make a mould from chicken wire, in the shape we needed, and they would apply layers of resin impregnated glass cloth, of "an appropriate specification", onto our mould. So off we went to the hardware shop to buy some chicken wire.

One evening soon after, Charlie and I sat down to 'make a start' on the mould. However, to our great delight we finished the whole thing in about three hours. A chicken wire 'shell', bent into shape and tied together with wire.

A Video Diversion
Our completion of the mould proved to be excellent timing, because we'd been obliged to say sorry to TV21's invitation to attend rehearsals in London. In lieu of this, TV21 asked for proof of our progress, and would accept a short video of the nearly finished Slippery Strana 'in action'. Well now we had something to show TV21. We taped plastic bin-liners around the chicken wire, and although Slippery Strana was still weaponless, it now had a shape !

Again, friends to the rescue - we arranged a 'show' for a video recording session by another of Steve's friends called Peter. Peter and Sally and their son Jolyon kindly gave their time and a video cassette to the Slippery Strana cause. It happened to be a miserably wet day but we didn't care because Slippery Strana had a lid. Charlie showed off his prowess on the radio control, dodging the rain puddles and weaving between our two volunteer 'obstacles', 7 year old Alex and Jolyon. I can't remember who held the umbrella over Peter's head !

Delivering The Mould
A couple of days later, after (our) Charlie and I tweaked and refined it a bit, I delivered the chicken-wire mould to Matrix Mouldings. Charlie and Wiz took measurements of the skeletal Slippery Strana so that we didn't have to leave the robot with them. They also asked lots of other questions - like where we might drill holes, and how we might secure the shell to the robot etc., etc..

Lots and lots of details were exchanged - except one !

How Heavy ?
My fault - I take all the blame. In my discussions with Charlie and Wiz, they certainly asked about the weight, but I had not imagined that a glass fibre shell would take us past the Lightweight Class limit of 22Kg, so I had dismissed weight as a parameter. Oops ! The skeletal Slippery Strana, with that steel angle-iron rim of which we were so proud, already weighed about 14Kg. Add our proposed pair of weapons at 1Kg to 2Kg each and we had left Charlie and Wiz just 6Kg to 8Kg in which to build a shell. Rather optimistic with hindsight.

Charlie and Wiz promised to deliver a shell of unquestionable strength - and by heck they did ! Between their acceptance of our mould and delivery of the finished shell, Charlie, Wiz and Justin (who added the kevlar) had applied layer after layer of fibre to our mould. The finished shell weighed around 10Kg, which when added to our existing 14Kg, made the robot 2 whole heavy Kg over the limit. But boy, was it strong. When we added our 2 spike-weapons to the equation, Slippery Strana was really overweight.

Slimming Down
The easiest way to remove 2Kg would be to take off our carefully-crafted angle-iron rim, but we considered this to be essential armour. So we kept re-thinking of other ways to lose weight. Perhaps we could cut holes in the heavy shell ? But then, what type of holes ? Large holes would let in the enemy; small holes wouldn't. But how many small holes ?

Given the weight and average thickness (a trade secret!) of our new shell, I calculated that a 1cm diameter hole would take off only 1 gram of weight, so to remove 2Kg we would have to cut 2000 holes ! This wouldn't leave much shell behind. So we scrapped the 'hole' idea.

Sadly then, we had to sacrifice the angle-iron rim. However, our new super-strong shell was really much tougher than we anticipated, so provided we fixed the shell down securely, Slippery Strana could in fact be sufficiently armoured with only the shell and the MDF base.

Just Add Spikes
A major bonus was that the new shell was rigid enough to carry our weapons, bolted straight through the wall of the shell. In fact the shell-wall-mounted spikes were far stronger than the original welded spikes. Click here to read more about these tailor made tangs.

Tough Tools
We had been warned by Matrix Mouldings that we would need special tools to cut through and drill our finished shell., especially as it contained (secret quantities of) the bullet-proof-vest material KEVLAR. In we went to the specialist tools shop, and out came the credit card. We soon had a couple of cobalt steel drill bits and one tungsten-edged 'riff' jigsaw blade.

Noise Pollution
We had all the necessary protective gear - ear defenders, goggles, breathing masks, gloves and overalls, so all we needed was a 'workshop' in which to make loud, long, socially unacceptable noises. Well we had no proper workshop. So in the following few days, we toured between Charlie's parents' garage, garden and hallways, thumping, cutting, grinding and drilling, generating much noise and dust.

Although very few of Charlie's neighbours will read this, we hereby thank them for their kind understanding and tolerance of the long and terrible noises we made during those otherwise lovely summer evenings.

Careful With The Kevlar
When we drilled the lid for its securing bolts, the kevlar lived up to its reputation of being nearly impenetrable. We had to take it very slowly, with carefully judged pressure and speed, so that the cobalt steel bit could cut progressively through it. Our powerful electric drill stalled to a dead stop more than once. (But no harm was done, thanks to our careful control of the work and to Charlie's careful grip and stance.) (Yep, Charlie did most of the drilling.)

Next came the trimming of the shell. It was generously deep, so we could afford to take a few centimetres off its bottom edge, checking as we went that the roof of the lid stayed clear of the top of our tyres. This cutting job was guaranteed to make a lot of smelly noxious dust, so we did it out in the fresh air of the garden. The riff blade worked wonderfully, and cut steadily through the tough shell. Remember that the shell began as a chicken-wire skeleton, so the riff blade was cutting through steel wire as well as through glass fibre, hardened resin and occasionally kevlar.

Eventually, we had the lid nicely streamlined, holes drilled, steel rim reluctantly removed and weapons attached. We'd been weighing Slippery Strana regularly to see how close we were to the 22Kg limit, and now it was time for a serious weigh-in.

A Healthy Robot
To be certain our now-complete Slippery Strana was below the 22Kg limit, we looked hard for a set of scales with which the TV21 judges could not argue. Where better than the Fitness rooms in Bath Sports Centre ? So off we went with coins in hand, causing raised eyebrows as we shuffled through the Sports Centre Foyer with our heavy spiked 'thing'. But the staff chuckled their acceptance when we mentioned Robot Wars.

We set Slippery Strana carefully on the foot-pad of the state-of-the-art digital scales, only to be asked what gender the robot was !!! We had tried hard not to classify our creation as male or female, but Charlie opted for 'feminine' and in a moment we had 'her' printout.
We hereby declare Slippery Strana to be gender-neutral again !

Speak Your Weight

As we entered the battle on 20th August 1998, Slippery Strana was a teensy bit heavier and weighed in at a very healthy 21.6Kg.




Slippery Strana Home



The Name

The Speed



Amazing Shell

A Good Fight

Page updated on 7th December 2000