When is a Boxer engine not a Boxer engine?

[grober]

Came across this article courtesy of JALOPNIK. Poses the question When is a boxer engine merely a 180 degree V engine. Well its all to do with the crankshaft and pistons

time to read that Jalopnik article! enjoy

https://jalopnik.com/its-time-you-knew-the-difference-between-boxer-engines-1825246413

 

[moonloops]

180 degrees is flat so what's the question?

I thought boxer was horizontally opposed unlike the other which shows each pair of pistons working together?

 

[Deleted member 131833]

So the thrust on adjacent pistons is 180 degrees opposite rather than being in same direction?

 

[moonloops]

So the thrust on adjacent pistons is 180 degrees opposite rather than being in same direction?

Correct I think ?

 

[190]

Each half of a boxer engine has perfect primary balance as the motion of each opposing piston balances the other. There is a small rocking couple because the cylinders are offset by the short distance between the crank pins which does produce a small amount of vibration.

The flat engine has the same primary balance overall as one pair of pistons balances out the other pair but the rocking couple must be much bigger than a boxer engine because of the greater distance between the pairs of cylinders so there would be more vibration.

My 1979 BMW motorcycle has a twin cylinder boxer engine which is basically one half of a 4 cylinder boxer. It's very smooth. If you tried to make a twin cylinder engine that was half a 4 cylinder flat engine it would only have the balance of a single cylinder engine and be quite rough.

 

[markjay]

My Alfasud 1.3ti had a boxer engine. And a fine engine it was...

The main benefits are less vibrations and lower centre of gravity, I'm told..... also it allows for a more sloping bonnet where the design requires it.

 

[grober]

A little more on that Steyr 50/55 engine mentioned in that article- its not so unrelated to Mercedes as you might think.

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the crankshaft

there's a mammoth but fascinating rebuild thread on a 1939 Steyr type 50 here for those addicted to such things
VWVortex.com - 1939 Steyr Type 50 assembly thread

 

[219]

..... it allows for a more sloping bonnet where the design requires it.

Didn't quite look that way in the Beetle , with all the tinware attached to it for cooling ...

 

[Petrol Pete]

So are we saying the flat 12 cylinder 180' Ferrari engines were boxers ?

 

[grober]

That Jalopnik article certainly asserts that. This diagram of the 512BB FLAT 12 engine appears to back that up with crank pins appearing to share adjacent conrods-witnessed by the twin oil feed orifices to feed the conrod bearings?? God knows what the balance dynamics are of a multi cylinder engine like that are like as opposed to a simple 4!
Again it may primarily be an engine packaging issue rather than one of balance?

 

[Doodle]

My 1979 BMW motorcycle has a twin cylinder boxer engine which is basically one half of a 4 cylinder boxer. It's very smooth. If you tried to make a twin cylinder engine that was half a 4 cylinder flat engine it would only have the balance of a single cylinder engine and be quite rough.

Although the flywheel does make them wobble quite alarmingly at standstill if you blip the throttle

 

[st13phil]

My 1979 BMW motorcycle has a twin cylinder boxer engine which is basically one half of a 4 cylinder boxer. It's very smooth.

The smaller air-cooled BMW Boxers were, as you say, very smooth but by the time they'd stretched the motor to 1000cc in the R100 it was getting pretty lumpy. A good friend of mine had a 1958 R60 and that really was super smooth - much better than the later bikes with bigger cylinders and lighter flywheels.

 

[Stratman]

I had an R75/7 which was nicely smooth at road speeds but the rocking couple certainly made itself known at idle. The sidestand held the bike about 0.0001 degrees off vertical and when I first bought it I'd pop it on the sidestand while I opened the gate only to find it on its side when I turned round again. I suppose that's why their main stands are prone to wear, getting the amount of use they do.

 

[190]

The great thing about BMW flat twins is they generally get smoother the faster you go. Mine is turbine smooth at 4000 RPM. Compare that to an old British twin like my 75 Bonneville which vibrated more with increasing revs making sustained high speed uncomfortable to say the least. BMW's may not be fast but what they do, they will do all day long.

I rarely use the side stand and have built up the worn centre stand stops with weld to make it work properly.

 

[MercedesDriver]

Came across this article courtesy of JALOPNIK. Poses the question When is a boxer engine merely a 180 degree V engine. Well its all to do with the crankshaft and pistons

time to read that Jalopnik article! enjoy

https://jalopnik.com/its-time-you-knew-the-difference-between-boxer-engines-1825246413

I just wish there were an internet and Youtube when I learned about these staff. I've found this video on the subject.

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