Very cool engine

Wow! That *is* cool! I wonder if the rotating cylinder is prepared with a cross-hatch or an axial hone pattern?

--Winston

And this is to be "almost" as cheap as a 2-stroke engine???

In whose dreams? Somebody got paid off.

Wolfgang

"Ed Huntress" wrote ... : It's built by a British company, RCV Engines Ltd., and it's amazingly : simple. They've made available a 7-year-old SAE paper about it, with lots of : detail about the seals (for anyone who's followed rotary-valve engines over : the years, that's where most of the action is): : :

Correct me if I missed something but it appears that with the cylinder rotating and the piston not rotating there will be a lot more friction between the piston and cylinder. Furthermore, the piston rings will be spinning with the cylinder and against the piston. These ring/piston friction points will be difficult to lube and could be a serious reliability issue. Art

An older spin on the problem:

That was WWII, RSV's are even older than that:

Never heard of it, Bob

Hmm, just looks like a variant of the Aspin engine to me. Nice to see pre-war technology come back to life...

Mark Rand RTFM

There have been a lot of rotary-valve engines over the past century, but they never get very far in the competition with poppet-valve engines. This one looks particularly interesting. If they really have the seal and wear problems solved, I'd like to know more about it.

The one used in the little drone is interesting, too, because it's a 60cc spark-ignition engine that runs on JP-8 and produces 4.6 hp. I doubt if there's another commercially available engine that will do that.

-- Ed Huntress

Dunno. Rotary-valve engines usually have a sort of inverted cup in the combustion chamber, which contains the ports. There have been some other engines with the ports in a rotating cylinder, but I've never studied them in any detail.

They can produce a lot of power, but they usually have sealing problems and wear problems. That's why this one looks interesting. It sounds as if they've solved them.

-- Ed Huntress

Their Type 58 model engine is $209:

-- Ed Huntress

Apparently they've held up well in Honeywell's tests, and the fuel efficiency is much higher than a two-stroke. So the friction doesn't seem to be an issue in practice.

I've been reading about this engine in various places and the two reasons it seems to have been chosen are that it has a power-to-weight ratio close to that of a two-stroke, and it will run on JP-8.

-- Ed Huntress

I saw that in the lab and they flew it once at lunchtime a few years ago.

I'd really like to see one run -- not that you could tell much by watching it, but I'd like to see it anyway.

-- Ed Huntress

I think I disagree with your logic. Some of the reasons you use drones are because they are relatively cheap, and because they don't contain a human. That means you can get away with things that would be considered unsafe/unreliable in a manned aircraft... Plus, if the engines really are "cheap" they may not mind if they have to replace them after every 20 hours of operation.

I doubt if the drone is cheap enough to justify a "cheap" engine. And a quirky engine isn't likely to make it past Honeywell, who is betting on its performance and reliability for the sake of the nice government contract they have for the whole device.

So, while not having to worry about human life eases the demand for engine reliability, it's still up against all of that conventional competition, which is well-proven and reliable.

All in all, it looks like a situation in which the engine is being taken seriously by serious people.

-- Ed Huntress

Just like I would like to see the Napier Sabre engine running, just to say I'd seen one running, likewise the big four bank radial, or the 24 cylinder "W" Allison. Gerry :-)} London, Canada

The most impressive small engine I've ever seen run was a small turbojet in a RC model.

It turned something over 100,000 rpm and the harmonics were amazing!

sounded like something between a wailing banshee and the warning horn for the end of time.

Do they still use any pulse jets in models? I was around 6 years old, which would have been 1954, when I saw a control-line speed event with pulse jets.

I can still remember the pain in my ears and the vibration like it was yesterday. My God, those things are loud.

-- Ed Huntress

I remember one of those from when I was a child (middle of last century). They were *loud*. I haven't seen one since.

There are a few Jetex sites up even today. That's a slow burning solid fuel rocket engine. I've thought about playing with those. There are cheap enough - if you can get them.

But the jet was just plain eerie...

Jet-X engines were revived a few years back, and there's a new one out -- "Rapier" -- that is of different construction (it's not a cannister with naked fuel pellets, but more like an integrated rocket engine with the fuel in a cardboard tube, AFAIK).

A little bit of web searching goes a long way...