Category Archives: vehicles

Light hybrid car transmission

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Ultra-Light Hybrid

How far can a hybrid car be pared down to make the lightest, cheapest and simplest runabout?

Well, for a start the batteries should only be enough for the ‘key local services’ trip of under 25 miles; under 5kW.hrs then and under £1,000. And that immediately starts the benign circle of lightness where many components spiral down in weight and cost.

tiny car engine

cheap and light engine

 

The engine – This modified Honda GX270 engine can be picked up with one hand but still delivers 12hp, just like Fiat 500s and 2CVs of old. The engine connects to one end of a short power shaft via a lockable centrifugal clutch so the electric motor on the other end can start it.

The electric motor: Eg. The 7Kg Magnax motor is the size of a soup bowl and produces a peak boost power of 113hp. Our small batteries will considerably reduce this but even so the power will be adequate, especially if supercaps are used for acceleration. The motor also provides regenerative braking and two reverse gears.

 

 

hybrid car transmission

2 speed gearbox and differential unit

The transmission: From the power shaft two selectable gears drive the differential unit and the drive shafts. N.B. The gears can be replaced with chains and sprockets for a quick DIY version – just side plates without the cast housing.

Why two speeds? Some electric cars just have a single speed direct drive but having a low gear for hill starts and town pottering and a high gear for relaxed cruising is a necessary nod to the limitations of the petrol engine. A simple programmable logic controller matches gearchanges perfectly and more besides.

A cam driven pump on the drive shaft circulates transmission oil to cool the electric motor and the finned case dissipates heat from the returning oil without the need for a radiator.

With regenerative braking there is less cooling needed on the brake discs so they are moved inboard and neatly integrated onto the side plates. The petrol engine and the electric motor have to be spaced off to allow the brake discs to fit beneath them. The effects of this position change to inboard brakes are so profound that brakes are dealt with in more detail later.

The unit is completed by supporting the steering rack and some suspension as well. Super light vehicles need less unsprung weight; this solution is much better than in-wheel motors and brakes.

This tiny integrated unit is all there is to the powertrain. No wonder Silicon Valley, Dyson et al feel they can join the automotive fray – they can. When contracted out a package like this covers most of the engineering work leaving the new entrants to focus on their metier – control and electronic interfaces. Will car buyers want inexpensive light hybrids that run almost free and barely need a service? Maybe, but it’s the new breed of car makers that will first be attracted to this package.

Solar panels – Our low voltage batteries would be compatible with on-car solar panels. Between 200 – 400W trickling in all day is worth something like another 10 miles in the bank which is a huge increase on the standard range. This is only viable on light and low powered cars but makes for good marketing USP.

charging post for electric car

self docking car charger

Auto connect charging – Low voltage and low power enables safe charging like this. Drive up against the spring loaded prongs and the electronics check connections and allocate polarity. A vertical slatted grill on the car completes the connections but still allows air flow. No special accuracy is needed from the driver with last contact automatically controlled; just drive into your car port and press the ‘dock and charge’ button to let the car creep up and connect. An air blast dryer might be needed for wet days – hello Dyson.

 

complex panels made easy

Aluminium panels – Complex light panels can be made with a CNC machined ply and aluminium sandwich. Internal plugs with star washers feed heavy loads into the structure. Suitable for complex bulkheads, doors and in particular for battery boxes. Edges are peened over and ply machined away to leave hidden internal struts. Early Lotus F1 cars used a similar idea for bulkheads.

 

 

tube and mount for torsional rigidity

light but rigid bulkhead connectors

Light aluminium tubes between bulkheads give useful channels and torsional rigidity to the vehicle. The cast aluminium brackets have a slight internal taper at the ends. Tubes are glued then expanded a few thou with a pressed-in taper ring. For production it would be quicker and cheaper to swage (whack em with a hammer) the ends of the tubes.

 

 

Brakes

The day that cars were required to do an emergency stop with no help from our leg muscles was the day hydraulic brakes became redundant. Instead of using ever more complex interfaces with electronics the hydraulics should have been entirely binned.

With inboard brakes it is easier to go all electric with no particular size restraints. For example a 120mm diameter stepper motor driving an internal ball screw could easily push a brake pad onto a floating brake disc. With each ‘twist caliper’ mounted on a pivot, a load sensor can enable braking power to be calculated making these brakes particularly suited to autonomy. Actually, even calipers might be redundant; something more like a clutch assembly allows spring assistance (and a power free parking brake) and less power from the actuator. In other words the brakes are already on by default -like a clutch – and the actuator starts by forcing them off. Either way, all the usual features – EBS, ABS, yaw control, hill descent, handbrake, pad wear check, regen prioritising, LSD – are all easily accommodated.

I write this in frustration at the lack of affordable electric runabouts – likes and comments are welcome.

 

Amazing AirBnb driveable house

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It’s a house Jim but not as we know it

Planners usually allow you to build a pod within the curtilage of your house. This one follows the rules but it comes on wheels. So what’s the point of that? Well for a start there are no foundations to worry about, just a bit of hardstanding will do. Then there is the ability to drive it; an all electric 4×4 chassis enables you to go for a trundle, down to the pond to watch the sunset for example. Steering is done from the front or from outside.

With the front wheels turned to full lock the whole house can rotate to track the sun, making full use of the 4.8kW photovoltaic array. So yes, it’s all off grid and only needs to dock occasionally to empty some tanks and to refill others.

Design – To make it all really feasible the design is based on off the shelf parts. So the house part is a modified 20′ shipping container supplied from a specialist constructor. The chassis part is from a 110″ Landrover with all the steering, gearbox and axles – a simple electric motor to drive it (cheap 240V, nothing fancy). Wheels are small and fat from a lawn tractor.

The solar panels are offset to make a canopy over the front porch.

Is it worth all the bother? Absolutely, for rental to eco enthusiasts this is a thrilling bit of kit. Imagine their delight when their pod comes round the corner to pick them up and take them to some lovely spot – all filmed from various points to give them a memento of an amazing experience. You can charge a lot more for that than if you were just offering a shed (I think they call them shepherd’s huts these days)….. is this a self powered off-grid shepherd’s hut then?

If you want to use this on your piece of land you might put a 3-point hitch on the back and call it a tractor – great to sit in a comfy chair while you mow the lawn!

N.B. With proper PV panel dimensions this is a preliminary sketch to see what it might look like.

Part of the drama is the house slowly turning to face the sun 🌻 a few times a day.

12 panels, 4.8kW makes another 14% through tracking the sun so it’s effectively a 5.5Kw array. Makes a useful UPS with it’s batteries. This machine will easily run your heat pump so it’s going to solve your heating problem too – at least an extra £1,000 in your pocket every year from that. Once hooked up to your main house the power can flow either way so the mini-split heater in the driveable house will always be useable, even after prolonged dark winter days.

So, £3,000 worth of electricity, £1,000 heating savings and over £1,000 a week on Airbnb + sales of the book and the experience video. Compare this with a buy to let house and with a build cost of circa £50,000 it doesn’t seem so mad after all. You could get your money back in 2 years and then live off this thing.
Guests are filmed as the house arrives, they get in and drive away to the viewing spot where there is a facilities block along with power and TV hook-up.
 
There’s a nice design for the hook-up to the facilities block. Ask me for details when you build this.
 

 

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Fan car – Ring record threat

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There’s a good reason why fan cars have been banned in motorsport. Cars sucked to the ground will always produce astonishing cornering accelerating and braking performance but any disruption to the skirt contact with the ground – such as running over a kerb – is likely to see a very rapid accident under way. Of course, a car that literally scrapes along the ground can only be used on very smooth race tracks and would be impractical for the road. The engineers at Original Twist don’t entirely agree and think a new approach is called for. Here is the Original Twist fan car design. The usual idea is that flexible skirts on the car scrape along the ground to maintain a seal, the air pressure inside the skirt is reduced with a fan and the pressure differential forces the car down. The Original Twist idea deviates by separating the skirt from the car; an independent suction pad is held under the car and with its lightness and agility this pad is free to track the road contours even if the car is in more vigorous motion.

The suction pad is circular in order to keep the air bleeding edges to a minimum. A 60” diameter area with a 1 psi pressure drop will produce 2,800lbs of downforce; about the weight of a car then.

The suction pad is not directly attached to the car. Instead it rides on 4 small wheels like a circular go-kart which is towed under the car.

Fan car suction ring

Fan car suction ring

The skirt edge is held very slightly off the ground so there is no horrible scraping noise as you move along. The skirt is different too and employs hovercraft principles in reverse. Apart from the main extraction fan air is blown out of slots round the edge against the air that is trying to get in and that makes an inertial barrier. The blowing can be done with an extra fan in the nose of the car for example. The extractor fan probably won’t double up as the blower because the pressure/flow characteristics are different but it would be worth investigating. A concertina bellows connects the skirt edge to the underside of the car floor and the seal is complete. The skirt/kart is pressed lightly to the ground by the trailing links that locate it and although the relatively heavy car might be jumping and jiggling the skirt will tend to remain flat on the ground and unlikely to reveal a sudden and potentially deadly pressure change.

With an electrically driven fan the downforce on the car can be tightly regulated and as aero downforce comes with speed the fan speed can be decreased accordingly until eventually there is no need for it and the whole underkart can even be retracted. The retraction feature makes the fan car suitable for the road; a fan car that can cope with humps and farm tracks and then pop round the Nürburgring in 5 minutes has got to rewrite the book somewhat.

While all this is alluringly simple there is one complication. Cornering with 8 wheels instead of four is going to be out of this world but the kart wheels will need to be steered unless they are on castors. A supermarket trolley under the car won’t add much dynamically but a steered go kart, pushed down very slightly by the trailing arms, will make a major contribution to the cornering forces.

The potential for electric sports cars has been examined in

https://originaltwist.com/2015/11/04/electric-sports-car-2020/

but the main point is that all the performance extremes of current supercars, in terms of acceleration, cornering and braking , can be exceeded by a factor of two or more. That means forces on your body, and head, of over 2g. It’s like doing press ups with someone sitting on your back so you’d need to be immensely strong to try the brakes without a full harness seat belt on. Cornering and braking at the same time would see you clawing your way out of the passenger footwell.

Formula One drivers experience forces like this but now a moderately priced sports car will be able to deliver the same. Headline figures of 0-60 in 1.5 seconds and 120mph in around 3 or 4 seconds will reset the performance bar in a shocking way. A 5 minute ring time is technically possible – just a question of who and when?

Note: Suck is a concept for when the force of atmospheric pressure – or other – acts against an object with lowered pressure on the opposite side. Really there is no such thing as a sucking force; when you ‘suck’ on a straw it is atmospheric pressure pushing your drink into your mouth.

With any fan car it is the weight of the atmosphere above the car which is pushing it down.

Atmospheric pressure is 14.7 psi at sea level so this sets the theoretical upper limits of our skirt with a total vacuum on one side. That would be about 18 tons in this case so the 1 psi pressure drop that equals the weight of the car is not too much to aim for and might easily be exceeded.

Modern canal boat

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click to enlarge

click to enlarge

Introducing the Original Twist canal going house boat; in the style of a narrow boat only bigger, better and absolutely modern. As a living unit it presents an economical lifestyle choice. For around £160,000 you get very low cost housing and maybe some change left over for a holiday house, long ski breaks and other good things. A comparable land based house or flat would be twice the price because of the cost of land, a boat on the other hand effectively rents the river via the canal licence and avoids council tax. This one avoids energy bills too which is a good start.

A house boat might be small but as well as reduced outgoings there are some great advantages. You are never stuck anywhere you don’t like; if you need a change you can just cruise to somewhere else, maybe near a cosy riverside pub. River life can be like an aquatic pub crawl but without the driving. You’ll make more friends among the friendly and hospitable canal community too, especially with the most interesting boat on the water.
There is more scope for travel than just the English waters as you can get a tow across the channel to use the huge French network extending all the way down to the South of France where winters are not so harsh. Otherwise the house boat is an attractive proposition for a house swap so the whole world is your lobster.
It’s a tough life being retired!

The Original Twist Eco-house boat is all about, modernity, comfort and enough economy to make a modest pension go far. Many traditional boat ideas have been updated to achieve this.

Construction
Unlike a go-anywhere narrow boat ours is 10 feet wide and 55 feet long – we’ll forgo visits to a few stretches of narrow canal in exchange for a lot more room and the garage – yes that’s right, a garage.
The shell of the boat is normal steel but without the enclosing steel roof parts. The front saloon and the rear transom are full height steel as is the central bulkhead that separates them. The two open parts between the steel constructions are connected at roof level by tubular trellised ladder frames which run the length of the boat interrupted only by the central bulkhead. The open parts of the boat are then covered by 2 insulated wooden rooms made of plywood and foam panels (SIPS).which are factory prefabricated – complete with windows, pipes, wires etc. This makes the boat lighter, cheaper and better insulated.

The two central living spaces house the kitchen a bedroom and shower room, all with heated floors. Each has a large pop-up roof (just like on a camper van) to give a more spacious feel while being flattened whenever a low bridge is encountered. These roofs carry the solar panels and can tilt sideways in either direction to catch the sun – the simple mechanism to switch hinge points is activated by the flick of a switch – an air cylinder shoves a cradle from side to side.
The steel and glass front saloon is very light and airy with a door giving access to the front deck. Standard fan-coil units are turned on end to make a pair of powerful demisters for the huge windscreen and to heat the room too.
A flat sun deck on the roof of the saloon makes a great place to watch the world go by and as we shall see later the boat can be steered from up there too.
The steel rear transom accommodates the propeller shaft, engine mounts, rudder mechanism, a niche for the air source heat pump.  A tail hoist mounted across the back (like on delivery trucks) supports a light vehicle such as a Polaris RAZR side by side.  After adjusting the height the ramps are dropped and locked onto a nearby bank so one can drive off in style and comfort. What is life without wheels?  Because the hoist can be folded up, the length of the whole boat can be shortened to navigate some of the tighter locks. An awning can be extended over the vehicle and there we have it; the first house boat with a garage.

Eco-tech
The real point about eco-technomologicalness is to get along as cheaply as possible without damaging the planet. The 20 solar panels on the top produce a nominal 8kWp; a lot more than most domestic arrays and enough for the small air source heat pump and to charge the batteries for the electric hybrid drive system. The hybrid drive is almost identical to that on the Original Twist hybrid 3-wheeler found on this site; here with a Lynch motor and a Kohler water cooled diesel. The usual benefits of a hybrid drive are there; the batteries give a few hours silent cruising and the diesel can take over indefinitely. The batteries are mostly solar charged or sometimes diesel engine charged with the Lynch motor doubling as a generator. Many moorings supply electricity so the batteries can be charged on cloudy days. With the air source heat pump the heating will run cheaply and conveniently off connected electricity or the batteries.  So there are 3 sources of heating power; the PV panels, outside electricity and engine cooling . Most boat engines are cooled by river water but here a second coil in the heat bank uses the 60% of wasted heat to make hot water. There is no connection to the river or the gunk that blocks up the filters (boat owners nod knowingly here).
Heating is supplied by the little 2kW heat pump which delivers about 6kW. N.B. River water is not used as the heat source. See ‘Air source heat pumps in Southern Europe’ also on this web site. here
Notable omissions are a wood stove and any gas as there is no need for either. Cooking is all electric.

Controls
Control of all the lights, heating, entertainment and even the steering is done by i-pad and Z-Wave meshed radio modules which are cheap, reliable home automation items. Narrow boats are usually driven from the back, a bit like a bus driver standing on the rear bumper. We can sit at the front in the saloon and steer from there or from anywhere else within range of the wi-fi; perhaps the sun deck even from the nearby pub! The Z-Wave controller allows for plenty of home automation tweaks like lighting control, security and leak detection, all from anywhere in the world. Theoretically the boat can be driven from anywhere there is an internet connection.
Actuators to move things like the roof panels and the rudder are operated by compressed air which is cleaner and easier to maintain than hydraulics. An i-pad and Z-Wave relays makes child’s play of these things; even a simple dimmer switch allows proportional control of the rudder.  The motorised satellite dish also needs to fold into a recess in the centre section when a bridge is encountered.

Neat extras
To make the kitchen a great place for eating while admiring the view the picture window on one side tilts up and out and a table is pushed outwards to make use of the outside space. Once parked up an extending awning over a drop down side deck, complete with an extending Barbie unit, makes an outside cooking area.

Central dust extraction – The centre section houses a fixed dust extractor plumbed to outlets around the boat to make cleaning much easier.

With a boat like this life will certainly be rich and varied.

ECO-HIPPY – One who is sufficiently off-grid to live almost cost free.

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Honda GX200 in the Original Twist 3-wheeler

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A 270cc engine in a car! Surely we jest?

Honda GX270 - even smaller without the tank

Honda GX270 – even smaller without the tank

Well first let’s see what the engine is required to do. Remember the car is a light, range extended plug-in electric car with everything minimalised to save weight. Even the electric range is cut back to 25 miles to halve the usual battery pack; half the weight and half the cost. In normal use the car would do the school run or a shopping trip on battery power alone but with no range anxiety thanks to petrol back up. Most electric cars boast longer range but for the majority of journeys they have carried around a heavy stack of surplus batteries. It follows that for most of our short journeys we are also lugging round the petrol engine so weight is going to be a major consideration.
The main use for the petrol engine might come from a weekend run in the country with some fast roads thrown in. With the 20-40bhp electric motor for brisk acceleration and overtaking the 12bhp petrol motor is really just for cruising at up to 50mph. Bear in mind that the engine is charging the batteries when the car is stationary, at the lights say, so the available, combined power when on the move is higher than one might imagine.
The Honda GX engine range actually gives us the choice to go for a bit more power but with weight penalties. Thanks to the go-kart scene they can all be tuned for more revs and more power. The rev limiter is always removed and a stronger flywheel added.
The GX200 only weighs 35lbs and can produce a useful 9bhp. The Loncin Chinese clone version only costs around £250 and makes a good starting point.
Next up is the GX270. Weighing in at 55lbs this might turn out to be the sweet spot between power and weight. With the usual modifications and the bigger carburettor from the GX390 this engine will give a good 12bhp.
The GX390 is good for up to 20 bhp but weighs a back straining 69lbs. Only testing will tell if that is departing too much from the light and minimalist idea but it would certainly be good for breaking the speed limit on the motorway. One should bear in mind that the engine and the electric motor are mounted just ahead of the rear wheel and the aim is to keep the overall weight distribution just slightly front heavy.
The engine mounting plate on the Original Twist hybrid 3-wheeler will be pre-drilled to mount all 3 engines so the choice is there. We can also consider the Briggs and Stratton racing engine with all the right bits built in at the factory – it’s called the ‘Animal’.
No doubt some inveterate tinkerers will have a spare engine for tuning experiments and, who knows, in time there might even be a racing series.
It is the intention that the engine will be pretty much clipped on and able to be changed in a couple of minutes so concepts like service exchange engines, rented engines etc are feasible. With that in mind the little 35lb GX200 that fits in a shopping bag looks attractive.

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Hybrid 3-wheeler – structural panels

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Eco-car structural bulkheads.

light and strong

light and strong

 

Aircraft grade birch plywood stuck onto an aluminium sheet has been CNC machined away to leave struts for load distribution and pockets for plug inserts. Loads are distributed by the remaining integral struts.

 

 

CNC machined panels

A mirror image version will then be glued on top –wood to wood- and the outside aluminium edges peened over to leave a solid looking panel (but largely hollow inside) which will not only look good with complex curves but be very strong and light. Any big holes in the panel will have the edges peened over too. Peening can be largely automated with a CNC guided rotating roller head.
Heavy loads from components bolted to the panel are fed in via plugs inserted into machined pockets so that any through bolts can’t crush the wood structure when tightened. The plugs are fitted in pairs with a larger star washer in between so that the sharp edges crush into the plywood to give even more load transmission.
Being CNC machined, identical complex panels can be produced quickly and with minimal labour cost. It pays dividends to design complexity out of the car and into the panels. Padded leather panels, a headrest for example, can easily be bolted up to the bulkhead as can other trim items.

Front and rear bulkheads in our car will be connected by 3 aluminium tubes. They will be joined to the bulkheads by cast ally brackets where the tube end is expanded and glued by a tapered collar pressed into each end.

 

The picture here shows how a side panel wraps the tube to make an immensely strong beam affording maximum side impact protection and, of course, a nice wide arm rest as well. The folding is achieved by machining ‘V’ grooves through the plywood leaving the aluminium skin to be a bent hinge line. A more complex shape to the groove can make rounder corners too.
.
The inspiration for much of this comes from two great car designers. Colin Chapman made racing car bulkheads from opposed metal sheets with peened holes and edges for rigidity. Alec Issigonis with his Morris Minor design used a complex bulkhead to mount suspension, shock absorbers, steering rack, battery box, pedals and more. We shall do the same.
No doubt the car will be strong, stiff and light but there is more to an eco-car than that; it must come at an affordable price and these techniques get us there all in one hit. In fact the car is so simple that anyone with a modest workshop and access to a CNC router could make one. Maybe a good base for a schools project?
Ultra strong and light complex panels like these will have many other uses. Paired frames for a motorcycle and a gyrocopter immediately spring to mind. In higher volume applications the plywood core can be precut with a waterjet cutter and then glued between the precut aluminium sheets.

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Plug-OUT Hybrid car

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Plug-in Hybrid? Yes but what about a Plug-OUT Hybrid?

The Original Twist Plug-in Hybrid featured on this site has some useful components in it which can be used for many other purposes:-

12bhp petrol motor
20bhp electric motor
12kW.hr battery pack
Power shaft close to the rear luggage rack

We’re looking at such a hugely versatile mobile power house that it’s hard to imagine all the potential uses. I’ll leave that to you but here’s my first selection:-

Domestic UPS
A small inverter connected to the batteries will provide 240V a.c. which can power a house for hours. This feature will augment the battery pack that off-grid P.V. systems will have anyway.

Grid balancing
When electric cars go mainstream the grid will bid for their stored power via smart meters. A parallel hybrid will always be able to sell power when the price is right and still make the next journey.

Electric generator
The batteries can be kept topped up by the 9bhp petrol motor charging via the electric motor on the other end of the power shaft. Extended power cuts won’t be a problem.

Mobile power supply
The vehicle can deliver d.c. and a.c. power wherever it goes. The range of power tools that can be driven is endless and this will empower trades people and farmers alike.

Power shaft
It just takes an extra pulley on the power shaft to provide drive to anything bolted to the rear luggage rack. The picture here shows a compressor but it could be a lathe, a potters’ wheel, a wood chipper, a water pump ….. etc etc.
A rear p.t.o. is also easily arranged for light duty mowing, for example.

Camping
No problems with lighting and cooking when you go camping in a Plug-OUT Hybrid.

Go-Kart
The Honda GX petrol motor takes just minutes to refit into a go-kart and it’s already modified with racing parts to suit.

If ever there was an automotive Swiss Army Knife this is it.

Swiss Army Knife?

Swiss Army Knife?

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Original Twist hybrid electric 3-wheeler

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Original Twist 3-Wheeler

Original Twist 3-Wheeler

OK – so the next automotive era has arrived and all car makers now offer some variation of an electric car. However, despite thousands of people with free home-brewed solar electricity just itching to go electric there is nothing economically viable on offer. Here then is an attempt to define what would be a workable, even desirable, alternative.  A lot hangs on the price.
Anyone paying the London congestion charge could be paying an additional £2,000 a year.  If one spent £10,000 on a vehicle that was exempt it would immediately give a return of 20% on capital so that suggests what the lowest price might be and even double that would still be economically feasible.
Let’s set a price target of £10,000 – £15,000 and define what sort of attributes most users would want:
Safety – very strong with above average crash sustainability. Not like a Sinclair C5 then.
Seating – for 2 adults and a rear parcel-shelf seat for occasional use, children and baggage.
Range – a normal daily commute of a 25 mile round trip entirely on battery power.
Range – a small combustion engine to give unlimited extended mileage.
Parallel hybrid – both power sources used at once if extra power is needed.
Plug in hybrid – batteries charged at home or by range extender engine.
Performance – equal to or faster than normal traffic.
Luggage – similar capacity as any other small car and much better than a microcar.

The key to economical motoring is lightness so from the start let’s begin with a 3-wheeler with two wheels in front and one behind. At a stroke this dispenses with some heavy things like a differential, axle, and one back wheel with suspension, brakes and associated bodywork.
With some heavy batteries mounted low down between the front wheels there will be no stability issues.
The power train couldn’t be simpler. The rear wheel spindle is mounted in an ‘H’ shaped swing arm, just like a motorcycle, with a chain drive to a sprocket that spins on the same inboard spindle that the swing arm pivots on. This sprocket spins alongside 2 others whose chains run up to the main power shaft where dog clutches engage either one to give high and low ratio drives. The transverse power shaft has a push on drive coupling on each end to connect an electric motor on one end and a small single cylinder petrol engine on the other – it’s that simple.
The permanent magnet Lynch electric motor produces maximum torque from a standstill so there is no need for a clutch. It also doubles as the starter motor for the engine, a regenerative braking charger and can run backwards to provide reverse gear. Dispensing with a starter motor, alternator, gearbox, prop shaft, clutch and reverse gear puts more in the ‘saved weight’ account. Electric power is a useful 20bhp with 40bhp available in 5 second bursts. By comparison the original 850 Mini had 33bhp but weighed 70% more than our target of 7cwt.
The electric motor and the 10kW.hr battery pack is sufficient for general short trips of up to 25 miles and perfect for city traffic creeping while adding in the petrol engine produces lively performance up to 60 mph for bigger trips on the open road.
The slightly modified Honda 200cc GX petrol engine only weighs 35lbs and produces 9bhp; adequate for performance boosting, charging, range extending and even as a limp home device. It can be replaced for well under £500 (clones are £200) and after 5 minutes of unclipping could be left behind for servicing.
Maximum combined power is 49bhp to give a power to weight ratio of 150bhp/ton; it will be nippy.
Of course the design could have substituted extra batteries and an extra electric motor for the petrol powered assistance but the logic is that some petrol power enables the driver to set out on any journey with confidence.
With an Indian made Agni electric motor (very similar to the Lynch pancake motor) this car would make great third world transport with India to start with. Tata this is your new super-cheap world car!
A £100 programmable logic controller is used to control gear selection via the clutches and the potentiometer throttle pedal. Regenerative braking is controlled but limited if the rear wheel tries to lock up. The same idea also provides optional launch control and safer driving by restricting wheelspin.

3 power modes are selected by a dash mounted knob;
Electric
Engine +
Range.
The ‘Range’ mode uses ‘engine +’ to drive as normal but whenever the car stops, the engine revs up and starts charging the battery ready for the next burst of power. At the first touch of the throttle the engine disengages and the electric motor stops the power shaft to select first gear.

At the front end of the car a simple subframe makes a battery box with incorporated suspension mounts. A lightweight rack and pinion and unassisted brakes take care of steering and stopping; all very simple but maybe the biggest weight and cost savings will come from the novel bodywork or indeed from the lack of it.
Central to the strength of the car is the passenger cell made from 2 CNC machined aluminium sheet and plywood bulkheads all connected with 3 fat aluminium torque tubes and further panels in the same aluminium and wood sandwich. The complex bulkheads enable the suspension loads to be fed into the extremely rigid passenger cell as well as mounting dozens of other components. Design like this not only saves weight, cost and assembly time but the bare aluminium looks so good that there is no need to paint it.
A smaller stressed panel incorporates the dashboard where a matt carbon fibre like laminate sets off the Stack instrument panel and the selector knobs for power and varying the regenerative braking.
Behind the passenger cell there is no bodywork as such; a horizontal tubular hoop supports motorcycle panniers on each side of the back wheel and a top box over the top.
At the front a one piece moulding covers the battery box with a pair of wings over the wheels and partially down the side panels.
The narrow central roof panel is supported by two longitudinal roll cage bars which also provide hinge points for the gull wing window/doors. Similar to a Mini Moke (and the Mercedes SLS) there are no doors as such, just side pontoons.
To cut out the cost of regulations, crash tests etc the car will be sold as a kit car so customers will be expected to fit the engine and the wheels, perhaps with 10 minutes of help at the point of sale.
Can the price target be met? By raiding the parts bins for existing components and keeping it all minimal and simple the answer is yes. The result would be a characterful and useful eco-runabout with almost negligible running costs and at half the price of a Morgan 3-wheeler (with sales of over 1,000).
The Renault Twizy costs just £8,000 but battery hire costs £55 a month and it is hardly a useful all-rounder, and anyway similar mass production would make our car much cheaper.
This is just a sketch to hint at the full design. If you want to make one just let me know.

Tech notes: front suspension – wishbones but none sourced yet. MX5? Usual Cortina geometry from kit car uprights.
Rear swing arm – nice specials available for drag bikes at reasonable prices, just need a wide mounting to take side loads. .. easily made anyway.
Wheels etc .. 155×13” tyres at front … cheap and plentiful. 165×14” at rear.
Electric clutches … magnetic or dog clutches .. either would work … drag race air shifters?
A lock-up centrifugal clutch needed for the engine to provide limp home mode.
Roll cage; usual wide front and rear hoops connected by a close pair of tubes running from top of screen to rear and then down the rear bulkhead to pick up the engine/transmission plates. The rear frame extension is a loop of same width as the roof bars and provides a rear grab handle as well as support for top box etc.
The aluminium engine/transmission plates also provide swing-arm mounts, rear frame bracing and pickup lugs for the rear coil shock absorber units – a nice CNC machining exercise.
For a low car like this, gas-strut balanced self raising seats would be a nice touch to make getting in and out easier and the side pontoon height could then be higher for better strength and protection.
Rear corners of the passenger cell are fitted with sprung skateboard wheels to counteract any inadvertent tipping without damaging the bodywork. The Morgan F4 used to scrape the exhaust to the same effect (only tipping after C of G was raised with back seat passengers).

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260mph in a 3 wheeler!

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It’s in the pub car park, still hot and ticking slightly as it cools. It has a pair of wheels visible under some cowls outside at the front of what looks like a glider fuselage and a single, fat rear tyre can just be seen at the back. So it must be a vehicle of sorts, but the rear tail wing and the pair of jet engine cowls blending into the rear bodywork make it look like a combination of a glider and a Lockheed A-10 Thunderbolt (alias the Tankbuster or the Warthog). Unlike most cars this looks very military with matt grey paintwork and stenciled labels such as ‘Keep 2m clear when motors running’, ‘no handhold’. I just had to have a word with the owner.

Q: This looks more like a glider fuselage with two wheel pods on the front. Is it some sort of jet car?
A: It’s a very slippery and light 3-wheeler and yes the detachable canopy is from a glider.

Q: Does it have a jet engine then?
A: No it has a front mounted 600hp turbocharged 2.5 litre Subaru Impreza engine driving all three wheels through an automatic gearbox. The things like jet pods at the back are air intakes for the entrained exhaust powered water cooling. The brake lights are incorporated which gives the illusion of exhaust flare and sometimes the exhaust does proper flares too.

Q: Wow that must be pretty quick. I guess you could keep up with a Bugatti Veyron then?
A: It’s a close thing and really a battle for traction. Acceleration is about the same up to 120 mph with all 3 tyres trying to smoke but up to 160mph the computer controlled rear wing gives exactly enough traction to get the edge. After that we can flatten the wing and carry on to 260mph with the Veyron in our mirrors. We don’t need to compare ourselves this way though – it’s easier just to say that this is a match for the supercars but the quickest 3 wheeler ever. Although, having said that, we are working on the next version where the rear pods will partially fold in to give less drag and with that we are hoping for a few more mph.

Q: What about braking?
A: Backing off from 260mph gives 600bhp worth of drag. Slamming up the wing gives drag and downforce so we can pull 3G on the brakes – only a good idea with a full harness on though and it’s hard to hold your head up. In some ways the brakes are too good, especially at lower speeds, as there is always a danger of collecting all the cars behind you whenever you stop.

Q: Why isn’t the rear wing on straight?
A: The wing is computer controlled for downforce as well as lateral force, hence the sideways tilt. We literally fly round corners. It sounds silly but we park the wing sloping to stop people putting their drinks on it at the pub. The car always has a crowd round it and it was fun when the start up routine tipped all the drinks off the back but we thought glass on the road was a bad idea.

Q: So what made you build it then?
A: I heard about some Australian guys who had built a successful drag Subaru WRX and it struck me that the drive to the rear could just power one rear wheel and that would enable a streamlined plane-like body to be used. They were getting 600hp and the thought of that in something light and aerodynamic was too much to resist.

Q: So it’s a road car?
A: Yes it is used daily on the road and is easy to drive slowly. What really freaks people out is when we play a loud jet engine soundtrack on the stereo and the best bit about that is playing the sound of a turbine spooling down after parking the car. The main problem though is talking to people about it all the time.

Q: Oh – that’s me too I guess. Well thanks for the chat; will we be seeing any more of these on the road?
A: We hope someone will take up the design and produce the car albeit with a bit less power. The Thunderbolt was a spectacularly beautiful plane and its character should live on in a car.

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