Multi Cylinder motors

Klipkopwildlife
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01 Jul 2013 14:05 #1 by Klipkopwildlife

Multi Cylinder motors was created by Klipkopwildlife

This is a serious question, in RC models we have twins, in line, 90^o, horizontally opposed, 2 stroke & 4stroke.
We have radials 3,5,7,9 cylinder, 4stroke.
I haven't seen a 3 cylinder inline, except in motor cars.
We have 4s, inline as well as horizontally opposed. I haven't seen a V4, except in cars.
Laser twins craftily use a piece of square bar to manufacture their 90^o V twins.
It seems to me that you could make an X4 from square bar, why hasn't anyone done it?
Second, why are radials always odd numbers of cylinders? No points to the person who says that the Wright Cyclone has 28 cylinders! Yes it does but each row has an odd number!

Do it now, you may never get another chance

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Ex-Member
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01 Jul 2013 14:55 #2 by Ex-Member

Replied by Ex-Member on topic Multi Cylinder motors

Four-stroke radials almost always have an odd number of cylinders, so that a consistent every-other-piston firing order can be maintained, providing smooth running

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old fart
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01 Jul 2013 15:44 #3 by old fart

Replied by old fart on topic Multi Cylinder motors

Probably so that you don't get 2 or 3 or 4 cylinders firing at the same time.

There is nothing like a dream to create the future.

Electrickery is the work of the devil.

Thanks: Klipkopwildlife

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Klipkopwildlife
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01 Jul 2013 17:47 #4 by Klipkopwildlife

Replied by Klipkopwildlife on topic Multi Cylinder motors

Both not bad answers, and I suspect very close to the truth. Now, why not an X4? It's much easier to make in a shed,and it's going to be smooooth! My thinking is this, Harleys are smooth, I don't understand why because the cylinders fire within 90^o of one another! Another two cylinders 180^o opposite will cancel out any other harmonics there might be.

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Quorneng
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01 Jul 2013 20:21 #5 by Quorneng

Replied by Quorneng on topic Multi Cylinder motors

A horizontally opposed twin will only be in perfect balance if the cylinder were exactly in line with each other which with a single crank shaft they can't be so they have to slightly staggered meaning there is a force trying to make the engine 'wiggle'.
An X engine with horizontally opposed pistons would have to have each cylinder staggered so would no better than a flat four as far as balance was concerned and a flat engine is much more stream lined.
Surprisingly with a balance web on each crank a 90 degree V twin can be as well balanced than a horizontally opposed flat twin hence their popularity in big engined bikes particularly as a V engine sits in a bike better than a flat engine.

You don't get perfect balance until you go up to a 90 degree V8 or a 60 degree V12 .

A radial is not bad but it does require a big crankshaft web balance weight and a complex master/slave connecting rod system to allow all the cylinders to be in the same plane.

Thanks: THE BLACKBIRD, blue123

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a4kskyhawk
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02 Jul 2013 01:10 #6 by a4kskyhawk

Replied by a4kskyhawk on topic Multi Cylinder motors

hi i may be wrong but the galloping ghost rc plane had a 3 Cylinder inline engine

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old fart
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02 Jul 2013 09:38 #7 by old fart

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Yes, it certainly did. :cheer:

www.kolmengines.com/HOME.88.0.html

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Electrickery is the work of the devil.

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barry
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02 Jul 2013 09:48 #8 by barry

Replied by barry on topic Multi Cylinder motors

klipklopwildlife.
Theres no reason one couldnt have a three inline .. early model aircraft had 3 cylinders . im talking back when guys used to build their own ..
It would be no different to a 5 cylinder audi .. google showed a few
I would think theres not many purely because of asthetics.. its nicer to reproduce what looked like a scale engine of the real thing ..

I like the harley comment .. smooth .. mine tries to jump out of its frame on idle , they do have awsome rubber damper mounts though...
Thankyou.

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CeeJayP
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Hi Peeps

02 Jul 2013 12:15 #9 by CeeJayP

Replied by CeeJayP on topic Multi Cylinder motors

there are several 3 cyl inline engines about, admitedly homebuilds no comercial ones that i know of, and i,m sure Phill at Fighteraces is currently working on a project for a new V4 engine from a German customer, i believe it will be available commercially eventually,
cjp

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old fart
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02 Jul 2013 12:42 #10 by old fart

Replied by old fart on topic Multi Cylinder motors

CeeJayP wrote: there are several 3 cyl inline engines about, admitedly homebuilds no comercial ones that i know of,,,,,,,

www.kolmengines.com/IL200.128.0.html ;)

There is nothing like a dream to create the future.

Electrickery is the work of the devil.

Thanks: Klipkopwildlife

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Klipkopwildlife
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02 Jul 2013 14:14 #11 by Klipkopwildlife

Replied by Klipkopwildlife on topic Multi Cylinder motors

Quorneng wrote: A horizontally opposed twin will only be in perfect balance if the cylinder were exactly in line with each other which with a single crank shaft they can't be so they have to slightly staggered meaning there is a force trying to make the engine 'wiggle'.

I'm under correction Q, but opposing twins are not slightly staggered, they don't have to be. There will be some 'wiggle' because you only get close to perfect balance when you get to a flat 4. Staggering is a feature of steam engines since, when you are at top dead centre (or bottom dead centre) when you inject steam into the cylinder it's going nowhere! The early railways found out the hard way, the designer reasoned that the chances of being at one or the other were infinitesimal! Several Flagship locos had to be towed out of stations very ignominiously!

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Klipkopwildlife
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02 Jul 2013 14:39 #12 by Klipkopwildlife

Replied by Klipkopwildlife on topic Multi Cylinder motors

barry wrote: I like the harley comment .. smooth .. mine tries to jump out of its frame on idle , they do have awsome rubber damper mounts though...
Thankyou.

Hog owner huh, I think I hate you already!

They do make a lovely noise though!

I accept the comment about windage on an X4, a flat 4 would be so much better. Since I've failed miserably to buy a multi cylinder motor on flee bay I was musing on the possibility of disappearing into the shed for 6 months or so to build one. I reasoned, for ease it would be so much easier to place 4 cylinders onto a piece of square bar, and of course the whole engine would be so much shorter that a flat 4 or an inline!

Do it now, you may never get another chance

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Klipkopwildlife
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02 Jul 2013 14:42 - 02 Jul 2013 14:45 #13 by Klipkopwildlife

Replied by Klipkopwildlife on topic Multi Cylinder motors

Quorneng wrote: particularly as a V engine sits in a bike better than a flat engine.

I take it nobody told BMW or Douglas?

Do it now, you may never get another chance

Last edit: 02 Jul 2013 14:45 by Klipkopwildlife.

Thanks: THE BLACKBIRD, old fart

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Eric
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02 Jul 2013 16:36 #14 by Eric

Replied by Eric on topic Multi Cylinder motors

Risking going off-topic, a steam engine is usually double-acting, in other words the piston is blown in both directions.
So - a two cylinder engine will be set up 'quartered', or - for every quarter of a turn of the driven wheel(s) there will be one piston at the top or bottom of the stroke, while the other one is mid-way. (Assuming you can have a top and bottom of the stroke, when the piston is moving horizontally!)
On really old single-acting, one piston engines, you could often see the driver giving the flywheel a shove, to get it to rotate, because the thing had stopped at the end of a stroke, in the 'dead' zone.

if you are calm and collected when all about you are going berserk - you've missed something important!

Thanks: Klipkopwildlife

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Mowerman
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02 Jul 2013 16:41 #15 by Mowerman

Replied by Mowerman on topic Multi Cylinder motors

I seem to recall that the V4 in the ford corsair needed a ballance shaft to keep it smooth.

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