The challenge: build a fire-fighting ship to put out a blaze on an island in the middle of a lake.
Oops! Robert and Cathy’s garden sheds are on fire and the teams have to race to see who can put out the blaze first! An added problem is that the sheds are on a small island in the middle of a lake. So each team must build a fireboat that will carry all the members plus a water pump (motor or hand-driven). The first to extinguish the flames and land on the island will be able to retrieve a flag and then race to a finish line to win the Scrapheap Challenge trophy.
Dick, Bobby and David Strawbridge (lieutenant colonel, major and captain respectively) are three brothers from Northern Ireland. They were blasted out of Scrapheap Challenge last year by the Chemical Brothers in target practice with their home-made cannons. The three soldiers, who have seen action in many of the world’s trouble spots, returned this year to defend their honour – and did so decisively against the Mothers of Invention in the last quarter final (bridging machine) and against the Techno Teachers in the second semi-final (giant mower). Have they learned anything from their previous forays into the wacky world of Scrapheap Challenge that will help them now?
Jeff 'DP' Del Papa, George 'Geo' Homsy and William 'Crash' Yerazunis make up the NERDS – the 'New England Rubbish Deconstruction Society' – Scrapheap’s first international entry (they all hail from Massachusetts in the US of A). Check out the NERDS website for their 'Tactical Rules for Scrapheap Challenges' – their advice to prospective contestants.
The NERDS won the first quarter final against the Dipsticks, when they triumphed as latter-day James Bonds with their 'diver tow' mini-sub. They went on to win against the Beach Boys in the great steam-car race semi-final. Every challenge they've tackled has involved water – will that help them now to cross the lake and achieve victory?
Stephen Riley (NERDS) is a Vickers Aerospace senior project engineer. Born and raised in Cambridge, he also went to university there, studying mechanical engineering. After a stint with SK Bearings in Cambridge, making bearings for bridges, he moved on to Hayward Tyler in Luton. Here he was involved in the manufacture of water centrifugal pumps for power stations. Four years ago, he moved on to Vickers in Portsmouth, where he designs hydraulic pumps for civil and military aircraft. As well as renovating his house, he plays cricket for Liphook Cricket Club and indulges himself with golf and fishing. 'I've never done anything like Scrapheap,' he says, 'although some would say that every pump I've been involved with is a load of rubbish!'
Ian Macrae (Brothers in Arms) is production and service manager at Johnson Pump International in Crawley, West Sussex. Ian has always been practical-minded, fixing lawn mowers, bikes, cars and motorbikes ever since he can remember. He left school at 16 to take up a four-year apprenticeship with a local engineering firm that manufactured pumps, and he's been 'in pumps' ever since. As an apprentice, he gained his milling, turning, welding and fitting skills, and followed this up with a formal engineering qualification. He was a technical sales engineer for 10 years, when he learned the difference between theory and practice. Nowadays he has a more managerial role, but his practical skills are still in demand as he is responsible for a workshop and service team.
Trevor Benjamin started work as a research chemist in heavy organic chemicals, but by chance became involved in pumps with an elegant screw pump by Holman Compressors. Joined Godwin Pumps when they had an embryonic design of a heavy-duty civil engineering pump that eventually became a world bestseller. Briefly became director of an aircraft re-fuelling pump company before joining SLD Pumps Ltd, the UK's largest pump-hire company, as sales and technical director. He has recently retired.
Jerry Leonards, who has been in the fire service for 25 years, is now divisional officer and superintendent of the Hampshire Fire and Rescue training centre. He used to work in the commander training department, but now has a teaching supervisor role.
An elementary test.
The two best teams that Scrapheap Challenge 2000 has to offer have to battle fire and water if they are to become champions. In one of the most difficult challenges so far, they must build a fireboat to extinguish the flames of a burning waterside building and retrieve a flag, before racing home to victory.
The NERDS, veterans of Mini-sub and Steam Car, face the Brothers in Arms, whose credits include Bridging Machine and Giant Mower, as well as captain Dick's achievement of having competed in all three series so far.
Blinded by science.
Both teams get down to it as if they were born to this sort of thing. The Brothers are a little confused when their expert Ian blinds them with science when describing what sorts of pumps they could plump for. Apparently they could choose either centrifugal or positive displacement varieties. Dick translates this into language his brothers will understand: spinning or piston pumps.
They go for the piston pump. The plan is to convert a car engine into a pump powered by a second engine. For propulsion, they will use the pump's output as a water jet, and for a hull, they will chop the top off of a van. This is what the Navy Blues did in Amphibious Vehicle in Series 2 … but with less than spectacular results.
The NERDS decide that centrifugal is the way to go. It is possibly the harder of the two options, but with the potential of being much more powerful – if they can get it right. They need to scavenge oil drums and a four-wheel-drive vehicle. It sounds like the same recipe that the Bodgers used for their winning amphibious vehicle in Series 2 (you know, the one that beat the Navy Blues!). Can the NERDS reprise the Land Rover's winning role for the fireboat challenge? Only time and some brute thought on the part of the team will tell.
Unfazed.
Expert Stephen Riley is called over: 'Steve, we need your mass!' shouts Jeff as the NERDS struggle to ballast a quad bike enough to pull a stricken Land Rover. The Brothers in Arms use their expert Ian for more cerebral purposes: he helps them figure out how to join two engines to form the perfect pump. They will need to scavenge a pair of engines and a van. The van roof they settle on does not look in the least bit shipshape – the sky is clearly visible through it. This doesn't faze the soldiers. They make short work of removing it with the reciprocating saws.
For all their computing power – Cathy has taken to referring to Geo as the 'human calculator' – the NERDS still manage to crash the Land Rover into the set on the way in. Maybe it was the discrepancy between UK and US measuring units that had them foxed?
The NERDS' impeller must spin at about 3000rpm so it has to be perfectly balanced or it will tear itself apart. The Brothers in Arms hope to squirt about 100 gallons a minute if everything goes to plan. Fire and rescue training officer Jerry, who is today's judge, points out that this is about one-tenth of the approximately 1,000 gallons a minute achieved by the professionals! Nevertheless he has his money on the Brothers as he reckons their design is simpler and therefore easier to implement. Less specific tolerances are required for the Brothers' machine, but he notes, they will have to unseize their engine if they are to pump even a drop.
Joined at the hip.
The NERDS chop the roof off their Landy to shed some weight – crucial if it is to be buoyant. They take it to the weigh-bridge, but to their dismay, it still weighs 1,560 kilograms (3,440lb). Half the day is gone, and the NERDS still need some flotation and to lose more weight off their vehicle. As for the Brothers, they are unable to free the pistons in their old engine and so need a new one.
Geo has a plan: 'Let's abbreviate the whole vehicle!' he exclaims. This is NERD-speak for chopping off the whole back of the car. So they get to work, but still manage to crash into the set on the way out with their surplus rear end.
Luckily for the Brothers, Bobby manages to find an engine that is better than their last one. The new plan is to swap their roles: the new engine becomes their drive mechanism and the old drive engine becomes the pump. This leaves them with one small problem, however. Their new engines aren't a pair at all. They are different sizes and makes, so joining them at the hip won't be easy, but at least they might work!
Ominous sign.
Geo has misgivings about the critical tolerances of the NERDS' impeller, which has to rotate at 50 times a second. Cathy comments that, since he isn't given to worrying, this could be an ominous sign.
The Americans have collected 12 oil drums that they intend to weld into water wings for the heavy Land Rover. The Brothers in Arms now have the two engines bolted together, but the whole thing is about 9 feet (2.5 metres) long. With some assistance from Cathy, captain Dick measures their hull and it too is 9ft long. 'Will this be a problem?' asks Cathy. 'No way,' replies Dick in true bodging fashion.
Their real problem is that they have to slow down the pumping engine so that it doesn't create a vacuum instead of pumping water. It has to remain powerful enough to pump a fair distance, though. The Brothers have to get to know their gear ratios in order to cut 1500rpm down to about 300. They also fit non-return valves to stop the pump engine from sending water back the way it came.
Both teams make paddles – just in case. With a few minutes to go, it doesn't look like either team will make it in time. But – you guessed it! – in true Scrapheap style, everything comes together in the last few seconds, including Geo's precious precision centrifugal pump.
Transatlantic tussle.
Whether the Scrapheap Challenge trophy will go on a weekend break in the UK or on a fly drive to the US of A is anyone's guess as the teams line up at the start.
The pyrotechnics are set, as are the teams, despite the fact that the Brothers' boat has sprung a leak or two. Their reaction is to laugh it off, aided and abetted by Robert. After all, a bit of water can't stop the army in its tracks, can it?
Turning on the waterworks.
The NERDS test their hose, and it's absolutely fabulous, shooting a giant plume of water out across the lake. Geo's work has paid off in spades. The Brothers have a lesser pump but brute force and ignorance in equal measure on board, according to Robert and the judge. It is soon obvious that the NERDS, while creating the super pump, have given little or no thought to manoeuvrability, whereas the Brothers' craft is far lighter and thus easier to paddle into position.
The action heats up.
Their heavy vehicle holds the NERDS back once the race is under way, and the Brothers snatch an early lead. However – and incredibly – the NERDS' pump is propelling their craft so well that they have little need to paddle. If the Brothers are able to reach the fire quickly, their weedy pump will be able to extinguish the flames before they really take hold of the timber hut. They do indeed reach the fire first, but it takes them an age to put it out. The NERDS, meanwhile, have caught up and put their fire out in a matter of seconds as their super pump makes short shrift of the conflagration.
The teams flag
The race for the flags is on. The NERDS send Jeff for theirs, but he can't get the box open, which means that he has to drag it to the boat. All the while, the Brothers are catching up, and their brawn comes into its own as Dick races to the smouldering hut. He grabs the flag and powers back to the boat and they're away. The NERDS, stuck in the shallows, surrender their lead to the army team. The lead changes twice more during the race, but it's the British Brothers who turn it on in the home straight to romp home ahead of the Americans.
So the Scrapheap Challenge 2000 trophy stays in Britain, care of the Brothers in Arms. But how will they fare next week against last year's winners, the Megalomaniacs, in the grand final? Tune in to see.
The challenge: build a fire-fighting ship to put out a blaze on an island in the middle of a lake.
Positive displacement (piston) pump.
Pros.
Cons.
Pros.
Cons.
What are the chief requirements when putting out a fire?
A mechanically powered pump with high pressure rather than a high flow rate.
What is a pump?
A machine used to transport, raise or compress water, using tubes or other machinery. Water pumps have a large range of pressures – from a fraction of a pound to more than 10,000lb per square inch (psi). Originally used to lift water from wells and later from mines, by the 20th century there was a proliferation of pump types for all kinds of uses, from water supply and sewage pumping to pumping oil through pipelines and fire-fighting.
What is the best type of pump to use?
That depends. The two main types are positive displacement pumps and centrifugal (retro-dynamic) pumps. Both have advantages and disadvantages when it comes to being mounted on a craft and then being used to put out a fire.
What is a positive displacement pump and how does it work?
Piston pumps are the commonest examples of these and work by using suction created by a vacuum to draw water into a closed space. Operated mechanically or by hand, a handle is attached to a piston inside a pipe. Lifting the piston creates a partial vacuum in the pipe and water is drawn up, through the pipe and into a chamber in the pipe. A one-way valve closes after water is pumped into the chamber; this keeps the water from flowing back down. More and more pumps of the piston pull more water into the chamber, which then produces a jet of water out of the other end. To raise the pressure, the power or torque must be increased.
The Archimedes screw, invented over 2,000 years ago, is an early version of a positive displacement pump. When a corkscrew-shaped mechanism within a pipe is turned, it pulls water upward. Prior to the invention of engines, this type of pump was powered by humans and animals.
Other examples of positive displacement pumps are diaphragm pumps, peristaltic pumps and rag-and-chain pumps.
Positive displacement pumps are very efficient and deliver virtually all of the water that is pumped through them. But their engines need to be accurately married and the tight tolerances of the engine mean that the pump has a limited life.
What is a centrifugal pump and how does it work?
This uses 'rotating impellers' – motor-driven propellers – that create a flow of water as they turn. The blades are immersed in the water to be pumped. As the impeller rotates at up to 1,500 revolutions per minute (rpm), water enters the pump near the axis of the blades and is swept out toward their ends at high pressure. Water is continuously pumped without the use of valves.
Axial flow pumps are another type of centrifugal pump. In these, the flow goes in the same direction as the shaft. They have high flow rates and low pressures.
Radial flow pumps are another sub-group. They have curved veins welded to a flat, solid disc, and on top of this is placed another flat disc with a hole in the middle. Water coming through this hole hits the spinning veins, which forces the water perpendicular to the direction of the shaft. Radial flow pumps have low flows and high pressures.
Useful pump facts.
This is the process based on a floating four-wheel-drive vehicle using one of the rear wheels for the pump – the other three wheels are the propulsion and the steering.
Boat: propulsion wheels.
This is to fix the suspension on the three propulsion wheels so that they are at the normal clearance to the wheel arch. This is to allow the pump wheel to be set lower, while the propulsion wheels dip 5 centimetres (2 inches) into the water.
(1) Have the vehicle resting normally or jacked up and supported on the suspension link to allow easier access.
(2) Strap up the suspension link to prevent the spring extending when the weight of the vehicle is removed from the wheel. The way that we do this depends on the type of suspension system.
(3) Do this for the three propulsion wheels but not the pump wheel (rear offside).
Crises.
Cannot find a way of fixing the suspension. If necessary, wire or cable could be used but might not be very secure.
The remainder of the boat activity is done after building the impeller (below).
(4) Take the three propulsion wheels off and remove the tyres.
(5) Cut 12 pieces of plate that fit the interior profile of the wheel rim.
(6) Weld four plates per wheel into the rim.
(7) Clean up welds.
(8) Refit wheels.
Equipment and tools.
Boat: structure.
(1) Make a rectangular frame 1 x 3 metres (3.3 x 9.8 feet), to take eight oil drums in two rows of four (the axes of the cylinders parallel to the 3m dimension). The four drums at the corners will stick out a bit.
(2) Lay out the eight drums, repair any holes or fill with foam and fix together with rope. Sit the frame on top of the layer of drums.
(3) Weld drums to frame, ensuring the welds are watertight.
(4) Depending on the actual section size of the rolled hollow section (RHS) and the vertical distance from the jacking point to the bottom of the wheel rim, weld four short vertical columns (25 centimetres/10 inches tall) to the top of the frame. They should be spaced to coincide with the four-wheel jacking points and placed so that the centre of the 3m dimension coincides with the centre of gravity of the vehicle.
(5) Weld two cross pieces (4m/13ft long) for outriggers to the top of the columns (at right angles to the 2m dimension).
(6) Lift the frame against the underside of the vehicle and weld to the jacking points of the vehicle structure.
(7) Weld a barrel to each end of the outriggers so that the centre line of the barrels is about 20cm (8in) below the jacking point height.
Notes on flotation.
8.45 barrels at 205kg (450lb) displacement per barrel. Have eight underneath and four just touching the surface. In practice, the four on the surface (on the end of the outrigger) could be partially filled with water to ensure the correct floating height.
Equipment and tools.
Pump: impeller.
This activity is to be performed after fixing the suspension on the three propulsion wheels but before building the raft structure. The impeller can be fabricated using the existing brake rotating parts and some blades made from rolled hollow section.
(1) Jack up the vehicle as high as possible. This is to allow the support structure of oil drums to be built underneath.
(2) Remove the rear offside wheel. If it is a disc brake, remove the calliper from the disc. Preferably we should remove the caliper altogether, but the hydraulic hose must not be cut, otherwise the brakes on the other wheels will not work. This brake can be used when we are firefighting (i.e. not travelling) to lock the three propulsion wheels and supply all the power and higher speed to the pump.
If it is a drum brake (which is more likely), open it and remove the hydraulic piston (leaving it attached to the hose or plug the hose). Leave the cable from the handbrake intact (if there is one) but disconnect it from the rear nearside wheel. When propelling forwards, the handbrake could be applied to ensure that all the power goes to the propulsion wheels. When firefighting, release the handbrake and apply the footbrake.
Note that some four-wheel-drive vehicles use a different method for the handbrake, which locks the prop shaft. In this instance, we will not use the handbrake; we will rely on the pump to take enough torque that the wheels are also driven.
(3) Start the engine and drive the wheels in top gear at 40mph. Measure the speed of the pump wheel. Apply the footbrake and record the new speed for the pump wheel. I think the wheel will travel forwards at four times normal speed. Record the speed on the speedometer when the impeller is rotating at 3,000rpm (should be around 55mph). This will be the design speed in operation.
(4) Cut pieces of RHS to form a cross on the disc or drum. These are the impeller blades. Depending on the diameter of the disc/drum, the sections may protrude beyond the outer diameter. Make them as symmetrical as possible.
(5) Cut a piece of plate, equal in diameter to the span of the RHS pieces. Cut a 10cm (4in) hole in the middle. Weld it to the RHS cross to form the front shroud of the impeller.
(6) Adjust the suspension on this wheel to set the impeller as low as possible.
Crises.
Equipment and tools.
Pump: pump case.
We are going to make a roughly circular case that fits around the brake/RHS-welded assembly.
(1) Cut two discs of steel plate 2.5cm (1in) larger in diameter than the tube OD.
(2) Cut a 10cm (4in) diameter hole in the centre of one disc. (This is the front plate.)
(3) Cut a hole large enough in the second plate (back plate) to clear the stationary part of the brake drum or the bearing on the brake disc.
(4) Cut the back plate in half across the diameter to allow it to be fitted around the back of the impeller assembly.
(5) Weld the halves back together.
(6) Weld the back plate to the suspension strut. Make sure that it is parallel to the front shroud of the impeller.
(7) Add other strips of plate to connect the back plate to the structure of the vehicle to add stiffening and support.
(8) Cut the length of the 25-35cm (10–14in) tube so that it is slightly longer (1–2mm) than the distance from the back plate to the front shroud.
(9) Cut an oval hole in the wall of the tube, the minor diameter of the hole being just less than the length of the tube. This is the outlet.
(10) Grind a piece of 5cm (2in) pipe to fit the OD of the pump case over the outlet hole. This pipe should be roughly tangential. Weld into position.
(11) Weld the large tube to the back disc, making sure the discharge pipe points the right way with respect to the direction of rotation.
(12) Start the engine and drive the impeller. Ensure that it does not rub.
(13) Tack weld the front plate to the tube to enclose the impeller. Again run the engine to check it does not rub. If it is all right, complete the welding to the top plate.
(14) Cut an angle on the end of the 10cm (4in) pipe.
(15) Weld the pipe to the top plate with the pipe angled down. This will keep the suction below the surface of the water to prevent air being sucked in.
Crises.
There should no problem cutting the plate as it can be flame cut and the accuracy is not particularly important. Welding the back plate to the strut: the pipe should not be galvanised or the welding will not work.
Equipment and tools.
Pump: discharge pipework.
(1) Continuing from the outlet pipe on the pump case, weld sections of pipe using the outrigger as support to bring the delivery up close to the rear offside passenger seat.
(2) Attach a hose to the end of the pipe (I am not sure how yet). The water jet will be directed by the team member and may be used for steering, propulsion and firefighting.
Equipment and tools.
Regarding the question of building a suitable vessel from oil drums or using a hull, my main concern is the stability of a raft. With two men pushing and pulling the handles of a pump and two men trying to direct the hoses, I think a hull of some suitable size is preferential.
The cylinders.
The two cylinders of the pump should be made from good-quality seamless tube in steel and not stainless steel. Anticipate needing at least 4 metres (13 feet).
Each cylinder needs to be approximately 1.5m (5ft) long. The bore of each would ideally be 100–125 millimetres (4–5 inches). I don't consider it practical to machine the bore of the cylinders, so we need to find reasonably new tube in good condition.
We should weld two pivot points opposite each other near the top of each cylinder. This is to allow each cylinder to pivot in relation to the crank action that operates each piston rod. In addition, we need to cut a hole in the side of each cylinder and weld a pipe stub on to it. This will form the basis of the discharge port. Ideally, we will use smaller bore pipe for this. The top of each cylinder will be capped off with steel plate. This needs to be the same thickness as the wall thickness (schedule) of the tube.
Into the top of each cap plate, we should weld in a gland. We should be able to make these from scrap steel found in the yard. In addition, we should weld two steel studs to the top of each cylinder cap to use as anchor bolts for the gland follower (again easily made from scrap materials) to form the basis of the seal.
Machines needed for this operation:
The pistons and rods.
The pistons should be made either from flame-cut plate or pre-made pipe flanges. For flame-cut plate, we would need at least 0.5sq. m (5.4sq. ft) of 1.25cm (0.5in) thick plate. For flanges, we would need PN16 (or BS4504, table 16) 20mm. Ball valves on the piston need to have a diameter in the region of 1.25–2.5cm (0.5-1in). Ideally they need to be made of solid rubber or a type of thermoplastic.
The pistons themselves would be welded to the piston rods. These rods need to be made from solid steel rod 2.5cm (1in) in diameter. We shall need approximately 5m (16.5ft) of this. We need to make various pivots and hinges for the crank mechanism from offcuts of pipe and rod.
Built into the pistons will be the wire cages to contain the ball valves. These cages will be made from a suitable rod or wire, which needs to be 4-5mm in diameter, and will be welded to the tops of the flanges, over the top of the balls in place. We may decide to drill the flanges right through in order to sit the cages in, and tack weld from the bottom.
The rods will need to be sealed in the piston cap by some sort of gland fabricated from scrap. The packing that goes in the gland will take the form of hessian rope or yarn.
Machines needed for this operation:
The frame and crank.
The frame needs to be fabricated from 5cm (2in) box section steel and angle iron. The detail of such a frame will be finalised on the day. I would suggest at least 10m (33ft) of box section and 6m (20ft) of angled steel.
Tools needed:
The non-return valve.
The non-return valve may be a little tricky. I think that we may have to make this up as we go along. It can either be made as a rubber flap or a ball valve.
The connections, hose and nozzle.
Connections from the hose to the pump can be made with simple self-fabricated hose tails and jubilee clips. The hose to each cylinder will, however, need a nozzle fitted into the end to create a jet. This can be made from scratch. We may have to make several to experiment with in order to get the best results.
Tools needed:
Fire Service International Ltd.
www.fsiuk.co.uk
Advice and tips on fire and firefighting for a comprehensive range of situations. Also details of courses and training in fire safety risk assessment.
Sheldon Fire Station.
www.thefireservice.co.uk
This site by a West Midlands fire station (linked to the Fire Department WebRing) gives some interesting local history and a wide range of information about the fire service, including a kids' corner, links and an on-line survey.
Ninety Years of Dennis Fire.
www.dennisfire.com/pages/history.html
Dennis Fire of Guildford, Surrey is Britain's oldest vehicle manufacturer. This part of their website has loads of photographs of old fire engines – just the thing for fanatics!
Los Angeles Fire Department Historical Archive.
www.lafire.com
Archive offering photos, maps, articles, reports and records from the era of horse-drawn fire engines to today's world of motorised apparatus.
Centrifugal Pumps.
www.pumpline.com
Technical information on centrifugal pumps, plus a complete range of resources for pump installation or maintenance.
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