[virkdoc]

Shucks my cylinders are not INLINE

Lol this is gotta be so funny.....so i have the touratech support bars on my 2018 GS Adv and somehowwww my right foot always fouled with it.....
I look down one day and lo and behold the right cylinder is a little behind the left cylinder.....I know I know there has to be a scientific explanation to it....so Im not worried...just wondering how many of you have noted it!

 

[JetSpeed]

Not sure how scientific the explanation is but the reason for the offset is simply that the connecting rods for each piston have to attach to the crankshaft in different locations so as one pushes it pulls the opposing the piston.

 

[judgedelta]

Envisioning a 2 cylinder crankshaft in my mind, I can now see why they must be off-set. I had ordered some support bars for my crash bars and found out that weren't the same length, but I didn't know why. I am grateful to engineers (when stuff works) but I couldn't be one.

 

[BMW]

First noticed this with my '96 Valkyrie. There is a reason as Jet explained, but it looks silly. Those same engineers could easily fix this by adding some covers in front of one cylinder (or row of cylinders) and behind another. With water cooling, it should not be a big problem. But this would unnecessarily take space and add mass.

 

[Houdini]

.... a simple diagram.

 

[Advart]

Interesting. I never noticed or thought about it till now. In my head they were completely opposite from each other but my logical mind knows that can't be the case.

 

[chaostrophy]

Interesting. I never noticed or thought about it till now. In my head they were completely opposite from each other but my logical mind knows that can't be the case.

Motors with a forked con rod have been made, I think. Not worth it.

Sent from my Nexus 6P using Tapatalk

 

[marc]

A forked con rod on a motor with opposed cylinders would have one piston at TDC and the other at BDC at the same time. The vibration of two pistons swinging back and forth together would be unbearable. One of the advantages of the boxer motor is that the pistons counter balance each other.

Harley's have a forked con rods.

 

[saughblade]

The offset cylinders create what's called a "rocking couple," in which the engine wants to twist a bit in the horizontal plane. It showed up mostly as a bit of buzzing in the bars at certain speeds. Starting with the Hexhead motor, BMW added a balancer shaft to damp this movement. Here's a pic of the Hexhead/Camhead balancer:

The top gear is on the end of the crankshaft. The shaft in the middle runs inside the shaft that drives the two cam chains. Notice that in addition to the counterweight on the rear end of the shaft (the circled item), the gears that drive the balancer also act as counterweights, exactly 180 degrees opposite the rear weight. This creates a rocking couple exactly opposite the one created by the offset cylinders, and (almost) removes that last bit of vibration from the boxer motor.

The system in the LC motor is similar, but I don't have a picture of it immediately at hand.

Isn't mechanical engineering fun?

 

[marcimark]

This explains it very nicely.

The cylinders can't be exactly opposite each other!

https://www.autoevolution.com/news/there-s-a-big-difference-between-a-boxer-and-flat-engine-85305.html

 

[BMW]

ICE vs. Electric

Internal combustion engines are a smart and intricate way of using fire (heat) to get them working. They are kind of disappointingly primitive in their basic principle. On the other hand, electrically driven motors have more elegant working principle. You do not see anything, and yet they are rotating "for no apparent reason". But in spite of this kind of impression, I believe I would not like to ride an electrically driven motorcycle.
Which means that I am a primitive creature, I suppose. Fire is simple. It cracks. It makes me feel good.

 

[Pterodactyl]

............The cylinders can't be exactly opposite each other!

Well, not exactly accurate. There is at least one example in which two opposing pistons share the same journal on the crank. One piston is connected to the crank at two points that are separated by enough space to allow the second piston to connect between them. This makes the piston directly opposed to each other. I cannot find a link to a picture. It certainly is not a common design and evidently not a very good or practicle one either. Radial engines generally have 3 to 9 pistons using a master rod and multiple articulating rods connected to a hub. So the pistons all on the same plain and opposite each other.

 

[marcimark]

Radial engines generally have 3 to 9 pistons using a master rod and multiple articulating rods connected to a hub. So the pistons all on the same plain and opposite each other.

But this is not about Radial engines, it is about a Boxer engine
I personally never have seen the design you are talking about, which doesn't mean it is not around.
It must be very uncommon and not practical, otherwise we would see it on our bikes