I have sometimes wondered what it is that causes an engine to rotate in the desired direction - is it just because the starter spins it that way? After all, as far as a descending piston is concerned, the crank below could equally be turning in either direction.
I think I have worked it out in my mind - is it the camshaft operating the valves in the right sequence that means the engine cannot run backwards?
So if say on a very simple engine the inlet and exhaust manifolds were reversed, and the fuel fed in the 'exhaust', would it run the other way round?
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Yes, it runs that way because the starter pushes it that way. As you suggest if you turned it over backwards it would breath in through the 'exhaust' ports and out through the 'inlet' ports. It is unlikely it would run though, as the ignition timing would be all wrong (occuring after top dead centre rather than before) and the valve timing would be all wrong - inlet and exhaust valves are timed differently. On engines with belt or chain driven cams, driving the cambelt the wrong way would just load up the tensioner and further put the valve timing adrift (and most likely pull the belt off).
Most car engines rotate clockwise when viewed from the timing end - Citroen D is a noticeable exception AFAIK.
Were you thinking of trying it?
Richard
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I thought that was the difference between left and right hand cars.
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Were you thinking of trying it?
Not seriously! But I did just wonder if it might have applications in certain situations, as a way of reversing an engine without the need for a gearbox. Marine engines?
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It was utilised in a Villiers two stroke engine in invalid carriages back in the 70's ansl I think Hiekle 3 wheelers. Peter
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It was utilised in a Villiers two stroke engine in invalid carriages back in the 70's ansl I think Hiekle 3 wheelers.
Yes. I rember as a child my dad and a mate laughing about a car that had this feature.
Four foward gears, four reverse!
All the interesting things that happened in the world seem to have happened before I was born...
--
These are my own opinions, and not necessarily those of all Toads.
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When I first started work (many moons ago) we had a dumper truck that you used to start with a handle, well this one used to kick back at you and actually run backwards, with smoke coming from the air filter. It used to knock a bit, but got about 3 reverse gears and one forward gear!
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Yes, the Messerschmidt bubble car also needed to have the engine stopped and started in the opposite rotation to give reverse! I seem to recall that it was done by switching to a different set of contact breakers (i.e. points).
In the early 1960's I had a Prior Viscount scooter fitted with a 200cc Messerschmidt bubble car engine (still with electric start but with the reverse mechanism disabled). The engine developed only 10 bhp but was still a lot faster than my previous scooter, an LD125 Lambretta with about 5 bhp. I used to go to Santa Pod Raceway every weekend to help with its construction; this was about 30 miles away on winding roads and it took 1.1/2 hours on the Lambretta but only 3/4 hour on the Prior.
I've never met anyone else who has heard of the Prior Viscount. It was the successor to the TWN Contessa, another rare machine. The TWN had a strange engine (two pistons on one conn rod I think) and was a high quality scooter but the company collapsed and the remaining frames were bought by another German company called Hercules. Hercules fitted the Messerschmidt engine but this had to be mounted high to clear the bottom of the frame and this had two bad effects. Firstly, it made the scooter very top heavy and, secondly, it meant that the spark plug was recessed into the seat, a very few millimetres below one's bottom (I hope that doesn't fall foul of the swear checker!).
They had to change the name of the scooter for selling into Britain because 'Hercules' already existed as a make of push-bike, so they called it 'Prior' for our market.
An odd thing about this scooter was that the front and rear wheels were not in line. I had a very difficult time convincing MoT testers that it was designed that way. Another oddity was that it had three silencers mounted in a horizontal stack like a squashed 'S'. When these eventually failed, the cost of a new exhaust system was so incredibly expensive that I modified a Lambretta 200 LE(?) exhaust to fit. That was when I learned that exhausts are designed for a specific back-pressure and the engine won't run properly otherwise, especially two-strokes!
I also had lots of problems with the twin fuel tanks splitting. Before welding them, I would run my mum's vacuum cleaner on 'blow' through them for several hours to clear away the petrol fumes -- not recommended! It was a fun machine though and I would love to find another.
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Most Japanese engines rotate the opposite way to European ones. This is why the old Rover 200/400 had two underbonnet layouts, engine on the right with VW gearbox for Rover engined cars and engine on the left with Honda gearbox for Honda engines.
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The German Ford V4 of the 60/70's used to appear to run in the wrong direction because the fanbelt and timing pulley were mounted on the front of the balance shaft which ran in the opposite direction to the crankshaft.
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The DAF/Vovlo 340 rubber band gearbox technically had the capability to go as fast in either direction, although a different set of hydraulics engaged in reverse to stop you doing this...
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DVD
I heard of a muppet putting a 340 on its roof demonstrating the fast reverse feature!!
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Most Japanese engines rotate the opposite way to European ones. This is why the old Rover 200/400 had two underbonnet layouts, engine on the right with VW gearbox for Rover engined cars and engine on the left with Honda gearbox for Honda engines.
I conclude therefore that most Japanese are left-handed, otherwise in the old days they would have great difficulty using starting handles.
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A crankcase compression 2 stroke with piston controlled ports would happily run backwards from an engineering point of view. This is normally prevented on these by giving the cam which operates the points a shape which causes the firing point in reverse to be very early, preventing it from running. That's necessary as a backfire during starting could kick it into reverse rotation. However, with suitable ignition, running small 2 stroke marine engines in reverse was (is) an accepted way way of achieving astern operation.
Regards
John S
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In the old days, the Japanese didn't build cars, although they did assemble Austin 7s and other western models. All Japanese built cars would have had electric starters as standard. I've no idea why they chose to rotate the "wrong way".
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If Japanese engines rotate the oposite way, is there an exception to the diesels that are used in Land and Range Rover conversions.
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Used to be a common problem with the old BSA bantams. A rider could pull up at the lights or a junction, stall the engine and prod away at the kickstart until it started again - often with a backfire. A few revs, clutch out a bit sharpish for a quick getaway - rider over the handlebars, bike going backwards.
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serious question :
how do they make sure a wankel engine is going to turn the right way ?
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crazed
If you think about it, a wankel is like any 4-stroke and it won't run backwards - it relies on correct rotation to intake and exhaust via the correct ports. It isn't like a port controlled 2-stroke, which only relies on the piston reciprocating.
Regards
John S
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a wankel is like any 4-stroke and it won't run backwards
My old Allagro's engine used to run backwards when you switched off the ignition. Had to put it in forth and drop the clutch to stop it. When you did it, the car shot backwards unless you had your foot on the brake :o)
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Mk 2 Ford Escorts used to run on when switched off until they introduced a "dump valve". If the Allegro ran backwards, what was that called "run back"?
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Most Japanese engines rotate the opposite way to European ones. This is why the old Rover 200/400 had two underbonnet layouts, engine on the right with VW gearbox for Rover engined cars and engine on the left with Honda gearbox for Honda engines.
Hi
Sorry to drag this up again.
Doesn't having the gearbox on the left in right-hand drive cars prevent having to translate the footbrake movement from one side of the car to the other (which incures mechanical losses) like left-hand drive (i.e. continent) to right-hand drive (here and Japan) conversions do? Also you'd get away with a shorter clutch cable (less losses again).
Mike Farrow
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Pre-war, Bolinder (A Swedish engine manufacturer) made hot-bulb single-cylinder diesel engines that were fitted to canal boats. These (often) had no gear-box, so were reversing engines and relied on going backwards when reverse was required. IIRC, a shot of diesel at TDC did the trick. They were & are notoriously unreliable, and could be just as llikely to stall as to end up running in reverse!
www.christopher.j.brown.btinternet.co.uk/canalpage...m
describes one in action.
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Most Japanese engines rotate the opposite way to European ones. This is why the old Rover 200/400 had two underbonnet layouts, engine on the right with VW gearbox for Rover engined cars and engine on the left with Honda gearbox for Honda engines.
I thought all engines rotated in the same direction, the different layouts being a result of an extra transfer gears somewhere in the driveline.
Otherwise some engine families would not work in rear wheel drive cars and never heard of one going backwards with wrong engine fitted. Could be wrong off course
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Yes Jap tend to rotate ACW & everything else CW all looking facing the crank pulley. A common transplant a few years ago was brit engine/gearboxes into Honda S800s, Sprite being a common one, this resulted in 4 reverse gears & 1 forward unless the axle was turned upside down!
I believe that more modern Japs are now using CW rotation.
Jim
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>>unless the axle was turned upside down!
I don't understand that bit ??
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Turning the axle upside down puts the pinion on the other side of the crown wheel, so the final rotation is in the opposite direction.
You need to be aware of filler plugs and breather pipes if pursuing this option!
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CLiff,
Sorry, I'm having a blond moment.
How can you turn an axle upside down; which is essentially a tubular bar ?
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We are talking live axles here, so remove from car & remake mountings so left hub becomes right & vice versa. Input (pinion) faces forwards so this changes rotation of input.
Jim
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I believe that more modern Japs are now using CW rotation. Jim
Honda don't seem to be able to make their minds up at the moment, if the Civic is anything to go by - the 1.4 and 1.6 VTEC models rotate anti-clockwise, but the 2.0 i-VTEC ones (Type-R and Type-S) rotate clockwise. Not sure about the diesel.
Mind you, they make damn good engines whichever way they go, IMHO.
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>>My old Allagro's engine used to run backwards when you switched off the ignition.
Run on was caused by pre ignition. ie carbon red hot.those units once at stop had a tendancy to reverse direction under compression but it was only for a second or so.cam shaft wont allow run in reverse.
Was mech1
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Most Japanese car engines rotate anti-clockwise ? I've worked on a few Jap car engines in my time and in my experience they all rotate clockwise apart from Honda.
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Unless engine designs have changed.all motors with exception of two stroke.can only run in clockwise direction.it would need camshaft alterations.ie built in opposite direction to run.with the need for induction transfer to exhaust/inlet.
Was mech1
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A mate of mine used to swap the plug leads over on his Yamaha 125 twin motorcycle (about a 1970 model I think) and bump start it backwards. Great fun when he is sat there with it already running and somebody asks to have a test ride.
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You can start a four stroke by reversing the ht leads.bear in mind roughly.misfires will prevent from running correctly.please dont confuse 2stroke with four.question wasnt about this.point has I think been made on this.
Was mech1
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