VegasJen

i have been trying to figure out for years now how an aircraft radial-type engine works. specifically the con-rods to crankshaft(?) and valve actuation. honestly, i haven't done any research into it because the forum is so good and diverse, it's almost like it's own little google search!
:cheers:

o.k. partially answered my own question.... http://travel.howstuffworks.com/radial-engine.htm
it doesn't explain valve actuation though. any thoughts on that? does it seem logical that vavle actuation for all 3,5,7,9 cylinders could run off just two eccentric lobes? how is the 2:1 ratio achieved?


[Modified by clutchdust, 10:45 PM 7/3/2003]

gkull

You should come up to my house in Sept. to the national air races. The Bear cats are the fastest. In a simple explaination one crank throw has as many rods as cylinders.

They take a old motor and end up with nearly twice the ci and run Methanol and N2O injection.

You would have a place to stay:)

Desertdawg

There was a great article written a couple of years ago in one of the Model RC airplane mags. It did a piece by piece tear down and explanation. But I couldn't find it.
Some great RC airplane radials have been for sale for years.



I also couldn't find any info on the cam and how it works, but this site seems to explain the radial pieces pretty good.
http://cincinnati.com/ageless/details.html

rainman69

There was a cool engine site I saw a few days ago...

Hm, can't find it. I'll look more later.

Chuck Harmon

If you think the radial engines are different, you should see a rotary (not Wankel) engine like the French used in their WWI fighters. The crankshaft was fixed, and the rest of the engine rotated with the propeller. Imagine seeing all those jugs spinning around! Eddie Rickenbacher flew one in his Nieuport.

Chuck

Kevin_73

Probably a single gear on the crank driving a 2-lobe cam for each cylinder.

Edit:
Nope, I was wrong.
Gear reduction, to a large cam ring.
Found this from your link: http://travel.howstuffworks.com/fram...om/curproj.htm


[Modified by Kevin_73, 3:06 AM 7/4/2003]

FEDX

The old radials were good engines,when I went thru aircraft mechanic school we worked on some of the Pratt and Whitneys.Its a master rod with slave rods attached to the pistons,and on the ones I worked on it had a large 4 lobe cam,best I remember. The rotary engines were strange as Chuck pointed out,as it had a fixed crank and the cylinders rotated around it.It also ran wide open,the pilot used a kill switch to cut it on and off as he flew.If you litsen to a older movie like Howard Hughes Hells' Angels,you can hear it cutting off and on.Old Rhienbeck Aerodrome used to have a Fokker Tri Wing still flying with a rotary engine in,dont know if they still do.

Twin_Turbo

A pic sayys more than a thousand words so I'll keep my mouth shut and:



And the valvetrain (1 cylinder)

ZD75blue

Heres my "list" if ya will...

Radials have an odd number of cylinders to keep the vibrations down, they are evenly spaced (down to the degree) apart.

They fire number two, then 4 then... continues, so that you get the spider looking crankshaft movements.

The engine case is mainly three parts, a center case like on a harley, with cylinders mounted to studs off the case. This center piece holds the crank, and guides the piston. On the back there is a cover plate, just to keep the motor protected. The front has a crank spline coming out of it feeding a camshaft thats gear driven, if i remember correctly she's turning at 6:1 (Dont quote me on this one)... and a gear reduction going to the prop.

The heads on top of the cylinders are large scale harley style... guys who build small scale will normally use a harley head, or a techumseh 10hp :crazy:

The ones that were on the WWII planes, for the most part were two deep, meaning they had a 9 on the front and a 9 on the back. The engine its self is a great design, but the turbo prop is more powerful by nature... which is why the funding for research and development for radials quit flowing in the mid 60's.





[Modified by ZD75blue, 8:30 AM 7/4/2003]

ZD75blue

Its a gear reduction to get it to turn at that speed
http://science.howstuffworks.com/gear-ratio.htm

WoodchuckH2

If anyone is interested and within driving distance of Lancaster, Tx (Dallas area) there is a Commemerative Airforce hanger at the Lancaster Airport. Its open to the public on Holidays, Sat and Sun. They have a decent little museum but the main attraction is a pristine Corsair, they fly it all the time. They also have a C-47 that flies over my house constantly. A couple of years ago they were flying the Corsair and a Zero together, its amazing how much difference there is in size, the Corsair is at least twice as big.

There is a fly-in every June and there are sometimes 40-50 WWII planes on the tarmac. In the museum is a cut-a-way of a small radial with a handcrank on the crankshaft, its great for getting an understanding of how they work.

There are Commemerative Airforce hangers all over the world and they have a decent website. And for those of you that have never heard a big radial running, its really cool, its not as sweet as a Merlin but its close.

VegasJen

hey chuck, i have seen those old rotaries. pretty wild contraption.
new question: how the heck do you control oil in one of those things? i'm thinking specifically about oil sitting in the lower cylinders. surely they can't just let oil gather inside the pistons and cylinders.
:confused:

VegasJen

ZD, i don't think i understand how your theory could work. from what i see, based on marcks GIF, no two pistons are at TDC at the same time. so how then could they fire in any manor other than sequentially? maybe i can see that i suppose, sort of... :crazy:
:confused:
i'm also going to assume for the sake of simplicity we're also dealing with a crank fire ignition system on these also(?).

FEDX

Oil control is a problem in the lower cylinders of a radial.After you run a radial,if you leave it shut down for longer than 30 minutes or so,you have to walk the prop thru and turn the engine over by hand.This is to make sure the engine wont hydraulically lock from the oil that seeps into the lowers,past the rings.If the engine doesn't pull thru cleanly or it was parked say overnight,you have to pull the spark plugs on the lowers and let the oil drain out.Failure to do so will quite often result in catastrophic engine failure,as the piston slams into the pooled oil with the valves closed something has to give :( .I personally witnessed it once on a Beech Super 18,single row Pratt and Whitney,had been sitting a while and they just hopped in it and tried to start it.As the engine began to turn over it nearly stopped,made a metallic clank,then spun right up and began running with a horrendous clattering then.It had broken a rod and the guy was trying to clear up the miss by revving it :eek: ,he ran it despite people signalling to shut it down.It wasn't the brightest thing I've ever seen,and it cost quite a bit of money,but at least I got to see the insides of it then.I was told that Buick or Chevrolet made a lot of the parts for Pratt during the war,the rods had the Chevy bowtie on them.As far as the ignition,I'm not sure if this is your answer but it was a magneto ignition system,and we used a buzz box to time th points in it.