having recently watched the THE FLIGHT OF THE PHOENIX recently( the proper one starring jimmie stuart), i get the impression its cylinder 1-long wait-cylinder 7-another long wait-cylinder erm 9, then all the fers at once oh, i think the engine in th PHOENIX might be a wright r 2000!!!!
All radial engines have odd number of cylinders on each row so that the firing order can be every other cylinder. i.e. 1-3-5-7-2-4-6. However I remember reading a paper presented to the RAeS titled "By The Application Of Power". In this paper a 32 cylinder 4 row radial built by Allison (I think) was mentioned. I don't know how the firing order would have worked.
The cylinders on a double row are counted from the top as 1(R)-2(F)-3(R)-4(F) alternating between the two rows, and so on around the engine. The firing order needs to alternate between the rows and therefore 1-3-5- and so on isn't possible. I think it is: 1-10-5-14-9-4-13-8-3-12-7-2-11-6, alternating even (front row) and odd (rear row) cylinders. I could be wrong though.
Given the mechanical arrangement of the connecting rods, each row will do that described above, it's just how the two rows are interleaved with each other.
I have to say I don't actually know the answer to this supplementary point so will leave it to others. What Jhieminga writes looks right. The shape of the crankshaft will give the answer. It would be interesting to know the firing order for the R-4360 (four row) as well.
I have looked up in my c47/DC3 ex USAAF manual and can confirm that the firing order was1,10,5,14,9,4,,13,8,3,12,7,2,11,6.. I worked on the Dak for about 3 years in the mid 50s for B.E.A. and enjoyed every minute once you had the right tools they were very easy to work on.
This became a major issue in the development of the R-2800 - well documented in "No Short Days: The Struggle to Develop the R-2800
"Double Wasp" Crankshaft" by Kimble D. McCutcheon.
The second-order effect of ignition timing (due to the geometry of master rod and articulating rods, some cylinders fire a bit early, some a bit late...) causes large torsional vibratory loads within the crankshaft. Several engines came apart during development!
Please indulge my passing interest in this thread, perhaps my questions are relevant and will help someone else.
Firstly. Which is designated the Number One cylinder? I would hazard a guess that it is the one at 12 o'clock, but are there any engines that don't have one in this position? How is No 1 ascertained in that case?
Secondly. In which direction is the crankshaft viewed for the purposes of finding the second and subsequent cylinders?
Cylinder numbers are as viewed looking forward. The rear cylinders are odd numbered and the front even numbered. No 1 is rear at twelve o'clock as Aerials suggests. A handy mnemonic for identifying which magnetos serve which cylinder spark plugs is: Right (5 letters) = Front plugs (5 letters again) and Left (four letters) = Rear plugs (four letters). I agree with Avionic Type about the 1830 being (relatively) easy to work on (as is the DC3 airframe although rigging the ailerons can be time consuming as there are no control stops - the ranges are governed by cable adjustment). I'm not a lover of the R2800 though.
As far as I remember the P&W radials used a "compensating cam" in the magneto to open the points and fire the plugs a calculated (and ground on the lobes) bit "too early" or "too late" just to allow for the fact that the pistons attached to articulating rods arrived @ TDC a bit earlier or later than a theoretical engine without articulating rods.
Ah yes, the Good Old Days with the Timerite stuck in #1 cylinder attempting to get the lights to wink on both mags together!! Who can forget the magic wand to find a crook (cold) plug?? Not easy to get the tip on the aft plugs of the rear row, especially the 28 cylinder nightmares we had come through from time to time.
Exactly right, mustafagander. Although I worked on no recips larger than a R-985, the magneto cam was offset as you describe.
However the valve pushrods were all actuated by the same cam ring, and thus enjoyed no such compensation. I suspect this mismatch between valves and ignition is the cause of the peculiar "loping" sound of a single-row radial at idle.
As an apprentice I worked on Bristol Hercules and R2800's mostly in the workshop. I think British engines' cylinders were numbered viewed from the front (American engines rom the rear) so you had to note the nationality of the engine when deciding which was cylinder #9 for instance or you could be embarrassed.