How Star Motors Work: Explained & Simplified.

Hello everyone!

It's a bit off-topic, but I've been wondering for a long time what the crankshaft looks like in, for example, a 12-cylinder radial engine.
I've asked many people, but they're all wondering the same thing, and no one has been able to answer the question yet.

So? Does anyone know anything?

is actually quite simple:

The KW (keyword) looks like it comes from a single-cylinder engine.

Here's what the connecting rod looks like:

http://www.pe.tu-clausthal.de/AGBalck/vorlesung/server/kolbenmaschinen/img_7528_g.jpg


It was common to have 5, 7, or 9 cylinders per engine, so multiple engines were often linked together in a row to achieve the desired number of cylinders.
Then the crankshaft is extended accordingly.

By the way, there are also star motors that don't have a crankshaft. In those, the pistons move along a type of eccentric mechanism.

Also, take a look at this as well: http://www.fh-friedberg.de/users/zima/konzept.html

especially the section about the Russian 56-cylinder diesel star engine will be of interest to you .

CU Gremlin.

To be completely honest!

I still don't understand anything.
'So, these are the nine connecting rods from the star-shaped engine? And the crankshaft sits in that hole in the middle? In which direction do the pistons push? Up and down, right? The cylinder principle is the same as in a straight engine, isn't it?'

Not quite. The KW (likely referring to a component) is located in the hole in the middle, and this hole describes a circular path during operation.
The firing order in a radial engine is either clockwise or counterclockwise, and it is not staggered like in an inline engine.

So, if I understand correctly, all the cylinders fire sequentially, which creates a circular path for the piston. Is this circular path comparable to the movement of a piston in a single cylinder of an inline engine?
If that's the case, then I see! / If that's the case, then I understand! / If that's the case, then aha!

So, this 9-cylinder engine fires 9 times in one crankshaft revolution, and there is 'no' moment of zero torque during that revolution. This should mean a huge amount of torque, right?

Exactly!

That's why the article about the engine with 56 cylinders is so interesting for us diesel enthusiasts: TORQUE instead of spoilers! }

Aircraft engines require a lot of torque, especially when equipped with variable-pitch propellers. Furthermore, this design is extremely space-saving in aircraft.

Hi,

Quote:

... then all cylinders fire sequentially ...

I think there's something wrong with the ignition timing!
If it's a four-stroke engine, you need two crankshaft revolutions for each of the four strokes. If each cylinder fires in sequence (1-2-3-4...), then the next revolution will be one without a power stroke.
As far as I remember, the cylinders fire with a gap of one cylinder, so it's 1-3-5-7-9-2-4-6-8... This means that one cylinder is always skipped during the ignition process. That's also why the cylinder numbers are odd.

I hope I have expressed myself clearly enough.

Quote:

So, this 9-cylinder engine fires 9 times in a single crankshaft revolution, and there is "no" moment of zero thrust during that revolution.

No, it ignites 9 times per two kilowatt-hour cycles.

To be completely honest!

I still don't understand anything.
Here are the nine connecting rods from the star engine? And is the crankshaft located in the hole in the middle? In which direction do the pistons push? Up and down, right? Is the cylinder principle the same as with an inline engine?


Exactly. You should only consider one cylinder here. Then you have a single-cylinder, four-stroke engine. The star arrangement doesn't change the fundamental principle.

If it's easier for you to visualize, consider two cylinders as a V-engine (without any offset in the crankshaft).

The torque of radial engines comes from, on the one hand, the short ignition intervals (which is true for any multi-cylinder engine), but mainly from the displacement. Radial engines are often characterized by long strokes and have a large displacement. This is why they operate at low RPM but produce a significant amount of power.

CU Gremlin.

I think I understand the principle now.
You have helped me a lot. Now I can finally sleep again .

It's always fascinating to see what you're all able to answer.
Amazing community!!

The crank mechanism is now clear.

But what is the valve drive like in a radial engine? 9 camshafts? } Are they located at the bottom, because the pushrods are visible? } And how are they driven? Probably not by a timing belt. }

mcgregg

Hello,

The valve actuation system is quite simple. You only need an intake cam and an exhaust cam. Nine pushrods run on each of these cams. The only problem is that the cam must only rotate at half the crankshaft speed. In my opinion, this is achieved using a planetary gearbox.

Piston aircraft engines are designed to operate at low speeds, typically below 2000 RPM, due to the limitations of propeller speed. This allows for a relatively large displacement per cylinder.

A common problem is also the increased wear on the cylinder walls of the master piston, which is the one that is rigidly connected to the main connecting rod.

Best regards,
Christian.

mcgregg wrote:

The crank mechanism is now clear. But what is the valve drive like in a radial engine? 9 camshafts?

Are they located at the bottom, because the pushrods are visible? } And how are they driven? Probably not by a timing belt. }

mcgregg}

Hi Chris,

chris11 wrote:

... You only need an intake cam and an exhaust cam. ....

It's not quite that simple! Because the firing order is not sequential (see my previous post), and the cycles are always offset by one cylinder, you need two intake camshafts and also two exhaust camshafts. On one pair of camshafts are the odd-numbered cylinders, and on the other pair are the even-numbered cylinders. The drive is accomplished via a planetary gear system.

That's right. Or, you could divide the crankshaft speed by 4 and add 2 degrees of offset to the camshaft.

There were already quite impressive constructions before jet aircraft became dominant.

z.B. http://www.chez.com/pullinghue/rdzwesda.html

Here's the translation:

z.B. http://travel.howstuffworks.com/radial-engine2.htm

Here, you can see how it works

Bertil wrote:

chris11 wrote: . Best regards, Christian. Hi Chris, ... You only need an intake cam and an exhaust cam. .... It's not quite that simple! Because the firing order is not sequential (see my previous post), and the cycles are always offset by one cylinder, you need two

intake camshafts and also [/url]two} exhaust camshafts. On one camshaft pair are the odd cylinders, and on the other camshaft pair are the even cylinders. The drive is accomplished via a planetary gear system.}}

That's the Russian diesel, isn't it?

which is mentioned in the article I linked and which was also built with a 56-cylinder engine.

Take a look at the Bristol slide valve engine and its control system.
http://www.fh-friedberg.de/users/zima/konzept.html

A Swiss watch with an automatic movement and chronograph is like kindergarten in comparison .


By the way (staying on the topic of the site):

Everyone knows the star principle in common-rail diesel engines .

-> high-pressure pump = 3-piston radial pump.

CU Gremlin.

Hello,

also das mit den 56-Zylindern kommt mir komisch vor. I have.
During my training, I learned that a star motor always has a...
'Each engine has an odd number of cylinders per row. I'm only familiar with engines like that.'
According to that, the 56-cylinder engine would be an 8-pointed star engine with 7 cylinders.
To be a wreath - that's a really long drum!

By the way, there were also some very interesting developments during World War I.
by Gnome Rhone. Clerget or Oberursel - a so-called rotary engine.
'The crankshaft was attached to the aircraft's frame, and the engine block was also connected there.'
mit Zylindern dreht sich. Gemischführung über die hohle Kurbelwelle. Dhe
The propeller was screwed onto the motor block.

Hi Jürgen,

Jürgen wrote:

...also das mit den 56-Zylindern kommt mir komisch vor. I have. During my training, I learned that a star motor always has a... "Each engine has an odd number of cylinders per row. I'm only familiar with engines like that." According to that, the 56-cylinder engine would be an 8-pointed star engine with 7 cylinders. to be per wreath - a really long drum!

You are absolutely right. By the way, it's even a turbo diesel engine, which means this thread is no longer strictly on topic .

Quote:

The BUGATTI MARINE 56 Cylinder Series Radial Aluminum engines boost up to 3970kW or about 5320HP. The world's highest power-to-weight ratio diesel engines feature a four-stroke radial configuration with seven blocks of eight cylinders each, inclined at 51º25'43" to each other, and utilize direct fuel injection, turbocharging, and intercooling. The BUGATTI MARINE 56-cylinder series shares the same 160mm bore and 170mm stroke as the 42-cylinder series, but with an additional two cylinders per block (eight instead of six), resulting in a total displacement of 196 liters. They operate quietly and smoothly at 2000 RPM. The moderate operating speed provides a service life of up to 4000 hours before the first overhaul and up to 10,000 hours before a major overhaul. Like all BUGATTI MARINE diesel engines, they can burn diesel or clean fuels such as biodiesel or LNG (natural gas), for an environmentally friendly propulsion system. The 56-cylinder series has a low fuel consumption of 225 g/kW-h.

SOURCE: http://www.yachtboutique.com/BugattiMarine/Engines.htm

To top it all off, this thing is also available as a 112-cylinder engine (2 x 56 cylinders)!