A quiet day at work, so I've been thinking about the use of plastics in car engines. We now have plastic manifolds, cam covers, throttle bodies and much more, so why not go all the way and mould the engine block and cylinder head in plastic, with metal inserts in the appropriate places? (combustion chambers, cylinder liners, bearings and thread inserts) Cheaper, lighter, won't corrode, lower heat loss, and there must be a plastic out there that would be suitable.
Anyone know whether this is already being worked on by any car manufacturers?
Richard Hall
bangernomics.tripod.com
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Richard
I suspect the main problem would be one of strength and stiffness, assuming the temperature limitations could be met. To match the stiffness of a cylinder block and head, given the applied loads, would require enormously thick plastic castings, negating any benefits of lightness, and creating size problems. Not practical I fear.
Regards
John S
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Some parts of some engines have been made using ceramic materials but I don't think they ever went into production cars. A good idea for weight/performance but perhaps problems of cost and longevity? Another idea like four wheel steering which seemed to have merits but has not been universally adopted.
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I remeber meeting a Ford R&D guy in the early 1970s who was working on a project for plastic gearboxes. It obviously never came to fruition, altho at the time I believe they were running prototypes. I guess it may only have been outer casings, but somebody out there must have been at Ford at that time.
pmh (was peter)
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There was also a plastic engine developed by Ford around the same time;it worked but was not very durable.
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Plastic (e.g. carbon fibre) engines have been the subject of several patents, though not from the established engine companies. As has been said, there is no way a plastic cylinder block can be rigid enough, even with inserts.
Cast metal blocks do have a severe limitation. Only the bores and mountings need high strength location, the walls forming the water jacket could be far thinner, say 1mm thick. The trouble is you can't sand-cast walls this thin as part of a cylinder block so they end up thick and heavy. Several engine companies, notably Honda and Perkins, have filed patent applications on answers to this.
One answer is to form the cylinder block like the letter A where the apex supports the top of the cylinder and the base carries the engine mountings. The sides of the A are comprised of an open lattice which can be covered with lightweight panels to form a water jacket or whatever else is desired. This is a very simplified description of the Honda and Perkins thinking, though the Perkins patent applications in particular go very much further than this (far too complex to describe here!).
Ceramics have had a lot of attention in the engine design field and I don't think we can write them off just yet. I haven't been directly involved in this work but I believe that durability (freedom from cracking) and bonding are the main obstacles to be overcome.
For example, the combustion chamber of direct injection diesel engines is usually located in the crown of an aluminium piston and the edges of the chamber get very close to melting point at times. This, and other thermal transfer problems, constricts the freedom of design in this very important area. Ceramic combustion chamber liners could solve these thermal problems but it would be disastrous if they came loose or broke up. Likewise with valve seats where bits breaking away could destroy both the engine and the manufacturer's reputation!
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Oops! I've just read ic's posting and I do now recall that Ford filed a patent application for a plastic engine. I believe that this was the only one on the subject from a recognised engine manufacturer - but I could be wrong!
As ic indicates, I think Ford's plastic engine trial was long ago (in the 70's?). Cylinder block stiffness has become even more important since then because it plays a vital part in the control of emissions.
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Modern cars seem to have got the materials the wrong way round in some areas.
Bits like door panels and wings which could be plastic, take a knock and spring back into shape, are made of metal.
Bits like bumpers, which need to take a knock without deforming, are made of plastic which falls to pieces.
Or am I missing something?
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Plastic bumpers are to do with low speed impacts with pedestrian legs etc.. l think. (Remember the debate about bullbars killing at 12mph etc..?) Something stiff might cause more damage to both the hit thing and the car's chassis as this energy is then displaced to somewhere else. I don't know why door skins/wings aren't plastic though, although they are on some sporty cars, (fibreglass etc..) so may be its a mass production cost issue.
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What happened to memory metal (the stuff you could heat up and it would remember what shape it was before you bashed it)? Did the Worshipful Company of Panel-beaters and Dent Extractors fight a rearguard action to veto it, perhaps...?
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The Ka has plastic bumpers front and rear and also made up of 3 pieces so if damaged could be replaced easily and cheaply.Most Ka are now ordered with painted bumpers-only the basic model is unpainted-people are not interested in the repair and money-saving side of it.
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See this link... my sister has driven one of these Saturn SL2 cars in boston for 5 years and 100,000 miles without any dents,,, you can hit their bodies with bats and rocks etc with no dents
and the engines look like painted stirofoam due to the lost foam casting process used
www.saturnbp.com/
Randolph Lee
Nantucket Island, U.S.A.
I live in my own little world, but it's ok, they know me
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"We now have plastic manifolds, cam covers, throttle bodies and much more"
I don't think so.....anybody here experienced throttle body distortion on their Rover car?
Makes the engine revs hang when very hot due to barrel distortion, which holds the buterfly slightly open.
Now cured by a metal body :-)
Plastic Inlet manifolds warp and melt when the engine overheats, too
MG-Rover Questions? Click on www.mg-rover.org
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