Small Innovation With Big Impact - Cylinder Offset
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- เผยแพร่เมื่อ 21 ก.พ. 2024
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The "famous hudson hornet" has a bit of a story about this... as Smokey Yunick was the mechanic on it..
he wanted to offset the bores like this but they wrote in the rule book
"you can not offset bore the cylinders in the block from factory position"
so Smokey Yunick offset the crank in the block...😂 and moved the gearbox across aswell... always thinking 1 step ahead of the officials
That's genius.
The very first polytechnic course I did when I became a motorcycle mechanic ( about 40 years ago ) , involved stripping and measuring an old ( already old at that time ) Briggs and Stratton lawn mower engine . Those engines today would be perhaps 60 years old , and they had cylinder offset . I recall that because I had never considered the possibility and was questioning my measurements . I don’t recall the amount , it wasn’t enough to see with the eye , but it was there . I think 1 or 2 mm . Honestly , I’ve always thought it was a normal part of engine design since ( maybe they are pushing that offset further now ) .
It is indeed a normal part of engine design. A small connecting rod angle on TDC keeps the piston held towards one side of the cylinder, which prevents it from rattling in the bore as it changes direction. But that is, as you found out, only a couple of millimeters or so.
This "désaxé" principle was followed by top-class designers such as Henri Toutée. Hard to say who originated the idea, but it certainly dates back to the early 1900s. My 1934 Chenard et Walcker has slots cut into the lower cylinder areas to accomodate the bias of the connecting rods! The balance problem is probably why the forward face of the flywheel casting includes a hefty annular integral "balance" (?) ring. I was thinking about machining it off, but your timely explanation is making me re-think!
This "Offset Cylinder Design" was First used by the Rambler Car Company in 1908.
Other Designs are an, Offset Connecting Rod, shaped as 'b' or 'd' - where the "circle part" connects to crankshaft-conrod journal - the "Top of vertical line" to piston.
The connecting rods (con-rod) used in this Video are standard "I-rods" - centered equally to the con-rod journal and are almost exclusively used in engines.
Experiments with "b & d" conrods go back some 50yrs and both were found to create "Piston-dwell" at TDC & BDC, depending on - degrees of offset.
Patents for Offset Cylinder and b & d Con-rods have Expired, are now Public Domain.
Small amounts of cylinder offset were originally introduced many decades back to counter piston slap.
This is known as the desaxe design. It has been used frequently over the decades. The true endorsement of it's advantages would be it's use in racing engine design and offhand I don't know of one, although there must be, given the constant quest for advantage in racing.
Some air compressors use the offset for the compression stroke I've found too.
Don’t know if he was the first but smoky Yannick employed these principles in his early days of racing
Piston pin offset, pin height, rod length, all things to consider. Thanks for the cool video.
Great video!
Changes the mechanical advantage the connecting rod has against the crankshaft in the begining of the power stroke
it has always been there as part of a kinematic analysis! it was waiting to harness
Every flathead Ford v-8 had it plus offset wrist pins.
offset piston pin in v motors ! same thing ?
I have wondered about cylender cant and offset combined. Small amounts. Some of my questions are in the offset what happens with cam timing and duration ramp rates. Then, flame time and piston speed down the cylender.
Fuel flame speed. It seems in an offset torque would increase.
Cylender cant may also improve
Torque. It may also improve piston side load.
Just thoughts.
Cylinder....
So thinking about this, If you had a 90* V12 or 190*boxer engine, with offset cyls, its possible to counterbalance it completely with almost no weights.
Can you elaborate ?
In your animation the connecting rod hits the cylinder wall and the poison exits the cylinder at bdc
I have to wonder if you had a boxer engine with both blocks offset would it be balanced.
Same thought! :)
The air cooled vw engine has the pistons offset about 1.5 mm
We have used longer rods and shorter strokes in the past Over-square allows higher RPM and less piston slap. This is due to the angle of rod and piston is less.
I think this would be perfect for a boxer or flat engine layout :)
It would be very strange for a boxer. Because of the opposed cylinder layout, in order for both banks to have the correct offset one bank would be raised higher, and the other would be lowered. I feel like that would create problems with assembly and strength, and may make it harder to properly lubricate and cool the motor.
I think the offset technology can only be realized with an in line engine.
The fb20 has asymmetric connecting rods
when this offset would gain enough,all the engines would have been build like this,long ago.
but buildingcost,to overcome the specific needs for this style engine are probably higher then the gains.
How is the connecting rod going through the cylinder
Doesn’t this in balance the engine
Effects on a two cycle engine such as non symmetrical port timing , increased transfer velocity, effect of a longer stroke mechanical leverage, and a longer power cycle.
Maybe ring catching prevention too = bigger ports :)
Probably an easy mod to the jug if you drill for bigger studs idk about sealing the base
In my university this construction was called dezaxial pistons. I learned it 20 years ago. God knows when it was constructed. So its kinda old.
Connecting rod failure is almost always attributed to failure of the rod bolt & the rod bolt is under the most stress at TDC at the end of the exhaust stroke & at the beginning of the intake stroke… that’s when rod bolts break & an offset cylinder makes it even worse.
Yeah, you might make more power with a severely offset cylinder, but it comes at a cost of reliability.
Cylinder offsets are as old as the 4 stroke engine. And depending on the engines use, can be great, or a huge liability. When off throttle, with high compression ratios, it's not uncommon to break the piston or the rod, or both, with the severe rod angles on the up stroke in off throttle scenarios.
Yamaha uses offset cylinders in its 4-stroke, single-cylinder motocross bikes, and probably in some other models as well.
I thought that was in their outboard motors didnt know their bikes used it
@@B1g_Tarn I do a lot of translating work for Yamaha in Japan but I've only done a few outboard jobs for them. I'm headed over there next week and will ask my contacts there. If they're also using them in the OBs perhaps they're using them in most of their engines.
Toyota in the ‘90’s claimed to have cylinder offset in a concept car, it also had soft valve springs as the engine was designed to not rev past 4000rpm. I remember all this but not the concept car.
Sounds exactly like the Prius engine.
Seems like an off-center flat engine might be easier to balance that a V engine
The only reason you would do it is to reduce engine height. And you could reduce engine length if you stagger every second piston. Volkswagen VR5 and VR6 engines used it.
In offset engine, It might in turn produce friction during the compression cycle.
I expected to see more torque as the power stroke happens at a little more leverage from the crank.
شكرا
They have been offsetting the wrist pin for 50yrs or more. Same effect.
Yeah , but only by about 1.5 mm .
To counter piston slap.
Kind of similar, but not entirely the same benefits.
That work on Renault 12 since 1968...
Balancing these cylinder offset engines are a hell. Doubt it will be mainstream.
Could do an offset connecting rod instead of offset cylinders.
Toyota 2AR-FE has this setup.
But doesn't side loading and piston slap become and issue during the comp. stroke?
Yep. Especially in high rpm off throttle conditions.
lower pressure around 1/10 during the compression stroke so less side load and piston slap
what do you mean by lower pressure?@@suncitybooksgeraldton335
And I thought that i had a secret in the 1975 with ofset and longer rod converted a steet bike with a two stroke 7o cc engine 5 hp in more than 15 hp
Not for 2 stroke?
i was thinking the same
Norton tried this on their Manx race engines in the 50's and 60's. They couldn't even measure the difference.
"...in the 50s and 60s."
Is the VW VR6 engine offset pistons?
no way jose
Could this be done in an opposed piston diesel configuration
Yes. The visual aspect will look a bit odd, but that would have no operational impact.
Sweet jesus! A 13 min vid on desaxe cylinders but never once mentioning desaxe!
Very easy just make a zick zack 6 cykinder engine and it will be naturally balanced!
You referred to the crank *counterweights* as a "balancing shaft".
It confused me. I thought the counter weights on the crankshaft were primary (countering the weight of the piston and wrist pin going up and down or side to side in a boxer) and secondary forces were generated by the weight of the big end (essentially being thrown from side to side).
You never mentioned how much the offset is.
Looks like half of a piston ratio
Not a large number of mm.
I had thought about this in 1979 but couldn't figure out the implications on balancing...
Interestingly enough I thought about it as well once in 1976 then again briefly in the summer of 1981. I had intended to build a totally custom one off V12 engine to test things out but I forgot about it until this very moment thanks to this video. Time to get to work.
Opposite on the way up
My 1934 Massey Harris tractor engine has offset pistons! This is not new technology.
Has to be more friction on one side
Yes minus the power stroke though
@Eduardo_Espinoza of course ! Eve bettin 2 stroke do you think?
This is so far from new, it's ludicrous.
This tech is roughly a century old, SMH!
V configuration would look "special"
Yeah, like a VW VR6
@@wandamaddox7824 does only a half of the vr6 has this benefit?
Good point @Einimas
I do remember hearing it had issues with vibrations even though they call it the "compact inline 6"which is very ironic
Maybe they can make one side normal instead?
I think it is not offset like this video describes. It's weird in a different way.
VR banks are offset opposite of each other
All I have to say is " slant 6"
Just more rpm and less nm
Balance shaft? Please look up that term.
counterweight
@@Abigailrp Correct.
This is one of those ideas that net zero improvement over existing designs. But I'm pretty sure someone will give someone some money.
Offset cylinder have bad balance
This is nothing new. Nissan has this in some of there older vehicles with smaller displacement engines.
This was "innovated" several decades ago. Is this AI generated content ?
New??? Not so much.
This is nothing new....
Find a better description of an offset engine. This is clearly written by somebody who doesn’t have English as their first language and they’re using artificial voice.