Youtube: how a radial engine works

[Mike Tomlinson]

Fantastic model of a 9-cylinder radial engine, shown operating.

Part 1:

Part 2:

[Davey]

I prefer the Rotary:

[richardmckenzie01]

That's the sort of art that I would like to see.

It really beats the Tracey Emin shit.

[NY]

Rotaries have always baffled me: how do you get your supply of fuel to the cylinders without leakage where the stationary fuel tank feed meets the rotating cylinder block. It's not like an electric motor where slip rings or a commutator serve the equivalent purpose with electric current: in the case of fuel, you need to prevent leakage.

What was the advantage of rotating the cylinder block? Was is mainly that the movement of the block though the air provides additional air currents over the fins and allows the cylinders to be air-cooled rather than water-cooled? Or was there any other advantage?

Presumably rotaries tend to be noisier because each cylinder has its own separate exhaust pipe - or if there is a common exhaust pipe it cannot have such elaborate silencer because of the need to balance and minimise the rotating mass.

Can rotaries be made to made with supercharging (ie a compressor to increase air intake pressure)? I suppose it's possible if the compressor is made to spin with the cylinder block. Turbocharging (using exhaust pressure rather than crankshaft rotation to drive the inlet compressor) could be "interesting" :-) In either case, you've got the problem of not being able to have a large (and therefore heavy) air reservoir to store boost pressure for cases where the throttle is opened on a slow engine and high boost is needed at a time when the engine can't yet generate it.

Is "rotary" the correct word for this type of engine, given that the word is also used to describe a Wankel engine which works in a very different way.

[Brian Gaff]

I'd have thought it was pretty obvious really. The oones I never understood properly were the Wankel engines with their rounded sided triangle in a round hole with a gear on the inside and three spark plugs.

Brian

[NY]

Yes: how does the increase in pressure in one "cylinder" space translate into rotational movement of the "piston" around the central shaft which then rotates? Definitely needs a moving model to explain how it works.

The "round hole" is not actually round but more like two semi-circles that have been split apart and a straight section inserted, to form a shape called an epitrochoid.

[Davey]

snip

The aircraft Rotary engine was invented before the Wankel, so to me it has the prior claim. As to the questions about supercharging etc, I have no idea. I just like the contrariness of having a huge mass rotating. I also appreciated watching Tractor Pulling in the US, where a machine with three Allison aircraft engines would be hauled to a stop by nothing more than earth. Try Youtube for 'Starting Giant Engines'.

[Mike Tomlinson]

En el artículo , Davey escribió:

Ooh, ta for the link.

[The Natural Philosopher]

No flywheel = lighter.

No aircraft engine ever used a silencer as far as I know. Some night fighters used some kind of flame baffles so they didnt show up at night.

I am sure it could be done, but tehre is no onterst in WWI style rotaryty engines at all, except tp power reproduction planes, and those are pretty faithful to the original designs

Rotary is applied to any engine where large parts of it go round.

The Le Rhone and Le Clerget's were there well beforer Wankel.

[Tim+]

I could be wrong but I think the carb would be mounted on a stationary part of the crankcase and then the fuel/air mixture was drawn up individual induction pipes to each cylinder

Just cooling IIRC.

Also had problems with huge torque reaction. It would significantly affect how quickly a plane could sharply bank to the right or left in a single engined craft.

As you say, turbocharging almost certainly not possible. No reason theoretically why they couldn't be supercharged but given that better engine designs were developed, not much point.

The term was in use *way* before the invention of the Wankel so I don't think it can be considered "wrong" in any sense.

Tim

[The Natural Philosopher]

And weight...

Er No . Not banking. Turning. Or zooming. Any yaw or pitch changes would case a reaction at right angles, so a rapid climbing or diving turn was likely to result..

Neutral in pure roll, but that wasn't something many pilots did in WWI.

Mostly controilled turns with the rudder.

[harry]

"Hush kits" are available for many aircraft. Usually they consist of a silencer and multi-bladed propeller.

Example

[harry]

ICE aircraft engines don't need a flywheel,the propeller provides this function. Some have a lightweight starter ring.

[Clive George]

You don't send fuel to the cylinders unless you have direct injection. So a rotary diesel isn't going to work, but a carburetted petrol engine as those old rotaries will be fine. The cylinders pull in fuel/air. Since it's suck rather than blow for that mix, any leaks will result in more air coming in rather than fuel leaking out, and that's easy enough to cope with by making the mix a little richer.

These would be plane engines, where the concept of silencer doesn't really happen :-)

Yes

Not a chance :-)

Turbos and superchargers have been used for years (pre-ww2), and don't use air reservoirs in the way you describe. Turbo lag is real, but the get rounds for that aren't air reservoirs, and the lag isn't terribly long anyway. Superchargers only need to work at the same speed as the engine (or rather proportional to) if you think about it :-)

[NY]

Ah, of course. For some reason I visualising the carb on the rotary part, but if it's on the static part, then a normally aspirated engine would suck the mixture and hence any leakage would be inwards, and air-only.

Do supercharged petrol engines compress the mixture, or do they compress the air and then inject fuel into the stream between compressor and cylinders? In other words, can you have non-fuel-injected carburettor super/turbo-charged petrol engines? Presumably for a rotary engine, as long as the supercharger is on the rotating part, it still sucks in mixture (so leakage will be inwards) and then compresses it after the leaky joint.

I hadn't realised that. I assumed that all charged engines had a reservoir, and that it was in the exceptional case of very hard acceleration from low engine speed (and hence low pressure) that the reservoir became exhausted, and that this was what caused turbo lag.

I've learned something!

[Clive George]

Yes, you can have super chargers and turbos on carburetted engines - they predate widespread use of fuel injection by quite a long time.

You can have the carburettor on either side of the blower too (with a super charger, not sure I'd want to try compressing a fuel/air mix with a hot turbo).

It would be interesting trying to arrange a supercharger on the moving engine. Probably theoretically possible, but not practical.

:-)

I'll let Peter Hill talk about the ways you reduce turbo lag - mostly it's about either keeping the turbine spinning or just using a smaller one which can accelerate faster.

[Brian Gaff]

That sounds like a disease of sheep! Brian

[RayL12]

I can fully see that.

I loved seeing that video. Mastery!

It was interesting to note the 2 circles that the piston heads described as they rotated around. As you watch the heads move as a whole, they describe an eccentric wheel; a weighting, which, is reduced by the actual counter weight he has on the shaft. Sadly, both are in the same rotation plane(Hicc!)and, additive. Good for engine momentum but, as you say, biased to control.

The 9 head rotary engine has a firing stroke that has a directional change every 80 deg, albeit, 40 degs per 720 deg of engine rotation.

Does this make for a smoother engine vibration?

I mean; if the engine block is being persuaded to follow a circular path, does this make for 3 virtual wheels that, between them form cushioned forces? Do these engines accelerate faster, smoother?

All the rotations of his model looked smooth.

...Ray.

[Vir Campestris]

AIUI the spark hits every other cylinder as they hit TDC. Two turns and they've all had one. The non-sparking one is a the end of exhaust / beginning of induction.

Andy