radial engine help

[wilbur1]

Does anybody have a blow up of a radial eng. Always wondered how the valve timing worked. Or maybe some spec on the camshaft. Thanks

 

[red admiral]

Push rods for most of them although the sleeve valve engines used a complicated geartraing. You run a big circular cam ring off the crankshaft with the pushrods on separate shafts that then run up to the cylinder head.

 

[wilbur1]

so as the crank rotates it also has lobes to open and close the valves? it seems like it would take forever to let exhaust out or intake in... still confused

 

[Arsenal VG-33]

It's quite fascinating to understand how they work. I found this very short clip on youtube of a cut-away radial to demonstrate it's operation:


View: https://www.youtube.com/watch?v=4hWZ40120BQ


Also, it's important to distinguish radial from rotary, such as the early Gnome-Rhones. On rotaries, the whole engine spun around taking the prop with it. Rotary fixed crank, Radial fixed cylinders. Here is one example of a rotary:


View: https://www.youtube.com/watch?v=R_JMGO5NzuI

 

[red admiral]

http://www.pilotfriend.com/aero_engines/images2/56.jpg

This picture should make it easier to understand.

 

[wilbur1]

Thank you very much! As an engine builder i like to look at differant designs and see what the engineers were up to, being thst a lot of the auto industry is so far behind the aviation its cool to see this stuff.

 

[HoHun]

Hi Wilbur,

Red's diagram shows all the important parts of the valve train. Some additional information: the cam ring typically rotates at half the crankshaft speed for a four-stroke engine, and that you have two cam rings per row of cylinders (one for the inlet, one for the outlet valves).

Regards,

Henning (HoHun)

 

[wilbur1]

thank you guys, I was just talking to my buddy, turns out hes a pilot and is going to take me to shop that builds nothing but radials. I try to find his top secret plans and let you know. lol Bill

 

[Elvis]

Wilbur,

If you happen to see this, you might also be interested in checking out W.O. Bentley's autobiography, "My Life and My Cars".
IIRC, he goes into some depth about Radial engines, in the section about "The Aero Engine".


Elvis

 

[wilbur1]

thanks elvis i will check it out

 

[YakMan]

Hi Guys,

I know this is an ancient thread but I am a newbie and doing the rounds of all the posts that particularly interest me. I build Russian radials and I saw this and had to put you right:

Hi Wilbur,

Red's diagram shows all the important parts of the valve train. Some additional information: the cam ring typically rotates at half the crankshaft speed for a four-stroke engine, and that you have two cam rings per row of cylinders (one for the inlet, one for the outlet valves).

Regards,

Henning (HoHun)

In a four-stroke in-line engine with a camshaft, yes it rotates at half engine speed but look at the gears on the graphic above - no way is that running at as much as half engine speed! No, radial cam drums or cam discs as the Russians call them rotate at one eighth engine speed. All radials have an odd number of cylinders per row, as you know, and the cam discs have four sets of lobes if they rotate in the same direction as the crank or only three sets if it rotates in the opposite direction depending on hte reduction gear set up. If you want to see it working have a look at my You Tube video by "revodes 21"

Thanks

John the Yak Man

 

[R Pope]

I have a Jacobs radial all disassembled out in my shop. The cam ring is driven by a planetary gearset that looks a lot more complex than it really is. Sorry no scanner so I can't put up any pics.

 

[msxyz]

Let X be the number of lobes on the camshaft ring and Y the number of cylinders; R is the gear ratio relative to the crankshaft

For cams running in the opposite direction to the crankshaft

X = ( Y - 1 ) / 2 and R = Y-1

For cams running in the same direction to the crankshaft

X = ( Y + 1 ) / 2 and R = Y+1