Hi, this is a weird question i was asked the other day and can't find the answer anywhere on the net. :ugh:

What is the firing order of the Pratt & Whitney R-1830 Twin Wasp radial engine on the DC-3.

Hope someone can help! :uhoh:

Thanx

I believe any radial fires in the order (for a 9-cylinder)

1-3-5-7-9-2-4-6-8

In other words the pistons firing follows the crankshaft round. Being a 4-stroke the crankshaft has to go round twice for each set of firing, and the firing order follows the con rod crank round.

It's for this reason there are always an odd number of cylinders on a 4-stroke radial.

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 f:mad:ers 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.

Thanx guys, it helps but this engine has a double row of 7 cylinders each. Would this be then 1Front 1Rear 3Front 3Rear 5F 5R ect. :confused:

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.

OK, I had completely overlooked the double row.

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.

Your at least partly right.

For 18 Cyl./ double row Engines:

Front row cyl. are counted as 2 - 4 - 6 - 8- 10 - 12 -14 - 16 - 18
Back row are 1 - 3 - 5 - 7 - 9 - 11 - 13 - 15 - 17

The ignition occurs in following order: 1 - 12 - 5 - 16 - 9 - 2 -13 - 6 -17 - 10 - 3 - 14 - 7 - 18 - 11 - 4 - 15 - 8 then 1 again....

There is a formula for the difference between cyl numbers, for the 18 cyl engine its 18/2 +2= 11. 1+11= 12, 5 +11=16....

The angle is 360/9cyl= 40 degrees plus 180 degrees for the second crankshaft offset. (220 total)

Cyl 1 to Cyl 12 is 220 degr., then its another 220 to Nr.5, 220 deg to 16 etcetc.

For 14 Cyl / double row:

Its analog for a 14 cyl eng. 14/2 + 2 = 9, so firing order is 1 - 10 - 5 - 14 - 9 - 4 - 13 - 8 - 3 - 12 - 7 - 2 - 6

This is out of a German 1959 book, called modern aircraft engines...


Edited for being too stupid (14/18 cyl)

All I can remember from my days in the old R1830 and R2000 sump oil is that the firing started with top centre and moved around the engine in a 120* increment.

OTOH, the firing order of the P&W JT 3D and RR Conways was much easier to remember!! :ok:

Just BTW, I thought the Twin Wasp series were 14 cylinder twin row.

Your at least partly right. ;)

For a two bank 14 cylinder radial (P&W R 1830 Twin Wasp) the order is 1-10-5-14-9-4-13-8-3-12-7-2-11-6 :ok:

WOW! Excelent stuff! Thank you. :ok: :ok: :ok:

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?

Best regards, Aerials

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.

Steve,
How about replacing the tail wheel shear pin !!
Good for a laugh:}

Re the firing order I was asked that question on my ARB P&W oral in Chancery Lane:eek:
The easy way to remember is in 3's
1,10,5 then decrease by 1
14,9,4
13,8,3
12,7,2
11,7,1

We had a 500 hour tappit check on the 1830 so you needed the firing order to bump the cam ring for the clearance check :)

The different vibration modes in the R-2800, causes and the solving thereof can be found at the bottom of the page on this link Piston Engines (http://www.enginehistory.org/engines.htm)

barit1,

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 @<hidden> 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. :ok:

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.

American horizontally opposed engines can catch out the unwary (or forgetful): the Lycoming No 1 cylinder is right-hand front but the Continental No 1 is right-hand rear.
Ground runs are interesting if you time the magnetos to the wrong cylinder. :confused:

I suppose this thread is as good a reason as any why turbine enjines dominate.

Piston aircraft engines , the big ones anyway seem to anon mecahancal engineer like me almost unworkably complicated -machining crankshafts for things like a DC7 or Stratocruiser engine must have been a nightmare and an incredible challenge for the machinists - no ultra precise computer controlled machines in 1953 I am sure

No wonder as a kid I seemed to see about one gently windmilling feathered engine a day as the big props roared out of LHR ( I grew up right next door) Mind you what a great noise they made and what a great sight at night
PB
Excuse the thread drift

Piston aircraft engines , the big ones anyway seem to anon mecahancal engineer like me almost unworkably complicated -machining crankshafts for things like a DC7 or Stratocruiser engine must have been a nightmare and an incredible challenge for the machinists - no ultra precise computer controlled machines in 1953 I am sure
Do bear in mind tha the largest output of the big piston engines took place during WW2, when they were assembled by, predominantly, women taken from non-engineering backgrounds, and put together in factories (in the UK at least) with restricted lighting and subject to constant risk of bombing.

The reliability of these complex engines in these circumstances is thus extraordinary - although looking at the Wright R-3350 fitted to the B-29 (and later Lockheed Constellation and others) the failure rate was such it was unusual for them to get beyong a few hundred hours. I believe the engines fitted to the B-29s used on the atomic bomb runs had been specially manufactured to enhanced tolerances and subject to much special testing before delivery.

i read many years back that HERMANN GORING knew the war was lost the first time he saw the build quality of the radial engine in a shot down B17.
he realised his economy (at the time-1942,he was still the head of the 4 year plan) could not afford a similar engine in a "disposable" aircraft!!!

As i remember it the mags we used [Bosh] I think ,had a "cog" type wheel to operate the points with a Red Dot on the master "tooth" we turned the engine till the points were open at the top of the master cam and adjusted this to 10thou +or_1 this was done in the hanger dock on check 2,3,and4s with all the plugs removed this was easier than the old 6in rule across the back and setting this to just opening using a timing light far to time consuming [they were both approved methods ] we were lucky except for DB, and XL [both EX Dart Daks ] B.E.A. modded our engine firewalls to have access panels fitted so setting up was a simple job not having to mess about with mirrors to see what you were doing.

DId the Stratocruiser engines have ignition analisers ?[pardon spelling]the thought of changing 28 plugs is too much to bear for a "MAG DROP] 14 was bad enough our Elizabethens Bristol engines had it and it gave you on a scope the "duff" plug or cylinder.:)

Correction - Wasp Major, 28 cylinders, 56 sparkyplugs. :ugh:

Not wishing to nit pick 28 pots, 56 plugs ,2per cylinder ,left and right hand mags each firing 1 plug per cylinder ,mag drop checked by switching each mag off in turn check rev drop is with in limits ,thus ONLY?having to change 1 bank of plugs , normal for most piston engines on ground run up check before take off but still the height of tedium for the engine fitter and the electrician as he had to do a H.T.Insulation check on the ignition harness as well ,quite a lively task when it was raining or when it was damp [kept the old Heart going with the shocks]:) Sorry when I said 14 I was talking about the Double Wasp

One short cut was to let the engine cool down and then start & run on the mag with the drop. After shutdown, the cold cylinder indicated the u/s plug or lead. Removing and refitting the cowlings was always a pain if you were doing the job downline without proper stands.

Hence the "Magic Wand" which was a thermocouple on a longish pole.

Start a cold(ish) engine and run for a couple of minutes, then touch the wand on each plug. With a bit of luck one or more will be cold and problem solved.

stevef is right about the "fun" of this stuff away from proper work stands!

Wasp Major, 28 cylinders, 56 sparkyplugs.
So, 4 engines on a Stratocruiser, 224 spark plugs. Goodness me, did they ALL have to be changed/spark gap tested on a check ? However long did that take ?

Though I had left B.O.A.C.to serve King and country [National service ]
before the Strat came in, they had a special section which all they did was service spark plugs, operated by Demented chaps, who to stop them escaping were chained to their benches. With a fleet of Yorks, Lancs, Connies Dc4M2s And the Strat they serviced 1000s of plugs per year plus of course all the lads car and motor bike plugs for a small fee.:ok:

WHBM,

It took about 5 minutes less than forever. When something like a Guppy dropped in with an engine problem a compression check on all 4 engines (wrong spec fuel - not 115/145 as required) was worth a couple of days for the engine crews. Then, of course, at least 1 plug would snap off in the cylinder head. Try to have a nice day!! OTOH, the overtime was usually welcome to us poor ground engineers!! :ok:

On our first Daks the points were accessed by removing a the cover on the back of the mag and then you had a 3 inch gap to the firewall with which to adjust the points with the aid of a mirror :ugh:

Later aircraft had a big panel in the firewall and you could adjust the points standing on the mainwheel
Luxury :}

Avionics.
Yes we had the dreaded plug bay and also a lifejacket bay
Both manned by errant apprentii :uhoh:

Then, of course, at least 1 plug would snap off in the cylinder head. :) (presumably :mad: initially !)

Could you drill it out without removing the cylinder ?

So glad "Got the T-shirt " enjoyed the good fortune of access to the mags from the u/c bay I thought the access panels was a BEA mod perhaps they were the Daks we sold later in the late 50s early 60s, did he have the missfortune as the P.W was a bit of an oil thrower to stand on the wheel and slip into a heap onto the floor scattering screwdriver and feeler gauges to the 4 winds? [I hope I wasn't the only one] :hmm:

On our first Daks the points were accessed by removing a the cover on the back of the mag and then you had a 3 inch gap to the firewall with which to adjust the points with the aid of a mirror

The Cessna 190/195 was even tighter - but Cessna designed the engine mount so the whole engine would hinge out on one side, and the mag covers & points were then easily reached.

Worst I ever worked on was the Howard DGA - about 1" clearance mags to the firewall. (There were firewall access covers, but they were useless because the rudder pedals were in the way. :ugh: )

We found the easiest & fastest way was to pull the entire firewall forward for easy access. :eek:

Then, of course, there was the B36. Wonder how long a plug change took.


After an excellent landing you can use the airplane again!

WHBM,

The technique my mob used was to bring the relevant cylinder to TDC, insert an air hose adapter into the good plug hole and set a relatively gentle air flow into the cylinder. This would, naturally, ensure that air was flowing out of the plug hole with the remains of the plug jammed in it - they generally broke off close to flush. It then remained for the poor victim to grind down a hacksaw blade to fit, jam the other end of it into a bit of scrap hydraulic hose so you didn't carve up your hand and cut to the TOP of the cylinder thread. Then make another cut about opposite and the final cut, very carefully, about 1/4 inch from one of the others. The master plan was to grab the small segment with long nose pliers and twist it out. After that it was fairly easy to grab one of the sides and gently fold it in a bit to enable the remains to be pulled out.

Should anything drop into the cylinder you had all the fun of a cylinder change and some terse words from the foreman. You could usually get away with a new Helicoil if the plug thread was damaged.

Ah yes, the Good Old Days with a few hours of smelly compressed air in your face and plenty of steel shavings to inhale, not to mention the contortions required to work on most cylinders using the usual crappy work stands. Thank heavens for jets!!

mustafgander you know you enjoyed it, all that lovely black oil ,the thrill of the slipstream in the hair [if you had any after removing broken plugs ]ajusting the vacum pump ,retrieving the engine bearer bolts and anything else you dropped from the mess in the drip tray , come on the jet boys had no fun at all. The odd pint of oil top up the to the max not 50 to 100 gallons [if the engine didn't use much oil there was something wrong ]also the up side was petrol was in the low thousands of gallons on the big birds and 100s on the Dak instead of the hours spent refuelling 747s one could take War and Peace to read whilst refuelling those . I know it's rose tinted glasses time but it could be fun ,we were younger then.

Avionics,

Yes done that ( Hence the name:O) Tyre skating !
We had a couple of ex BEA Daks so they would have had the Mag panels

How about the main pressure filter :} Good for an arm full of oil !!

Valve bumping for tappit check was always good for the odd skinned knuckles
Oh that colourful mix of blood and 100W :hmm:

Also hand starting the ones with Jack & Heinz ( not the bean people!) inertia stater was challenging.

Another Apprenti job was wire locking the push rod tubes:ok:

I guess half the things we did then would be banned by elf & safety now !:cool:

The kids today don't know they are born :8

Also hand starting the ones with Jack & Heinz ( not the bean people!) inertia stater was challenging. I guess half the things we did then would be banned by elf & safety now

As would starting with a rope wound around the prop dome and attached to a Jeep. :D

Who can forget hanging off the end of a six foot scaffolding bar when tightening up the prop nut because you didn't have a multiplier. And taking a sledge hammer to the prop dome spanner!
As for undoing/fastening that forward centre carburettor nut or locking the magneto attachment inboard nuts downroute on wobbly ladders when it's pouring with rain or blowing a gale...:{

I'm still doing it for a living. :)

Being part of a team restoring a C47 I asked our team leader what is the firing order of the R1830-92. He said "they" use the "minus 5, plus 9" method. Starting with cyl. number 1. 1 minus 5 = -4 (no minus 4 cyl.) therefore 1 + 9 = 10. Next 10 + 9 = 19 (no number 19 cyl.) therefore 10 - 5 = 5. Next 5 - 5 = 0 (no number 0 cyl) therefore 5 + 9 = 14 etc, etc, etc.

Looking at the rocker arm covers on both the R-1830 and the R-2800 engines, it appears they cylinders are in line so that 9 thrust strokes would be the case. I note in the cylinders are offset (front from the rear) on the 3350 and of course, it is quite visible on the 4360. However, finding other photos of the engine blocks show they are offset too. It is only logical, that this would be the case as rwo cylinders tandem would provide a lot of asymmetry. I feel sure engineers considered all of this.

Has anyone noticed a "motorcycle" radial engine; the 9 cylinder XR600? Assuming it was made by adapting existing parts like the cylinders of the old Silver Wing engine, a 2 cylinder V-twin, my, my. Can you imagine hearing those if they were put into production? Harley's 2 cylinder would finally be largely eclipsed as to running sounds, eh? Made by a New Zealander (can anyone remember the Clisby V-6 prototype when V-6's were not yet production items?); it and this engine are "Down Under's contribution to reciprocating engines.

http://thekneeslider.com/images/2009/03/xr600radial.jpg

Sadly, turbines have replaced recips but some will still pursue this for years and I find it fascinating.

Another interesting consideration of aircraft motors is the degree arrangement of the cylinders. 90 degrees like the V-8 of the OX-5 (and also the V-10's) and 60 degrees in the Packard Merlin. Add the W and X configurations of other motors and it gets more interesting. I am sure the physics of reciprocating engines dictates these choices and while I am new to the site and have not searched for it, I would be interested in hearing from knowledgeables about engine reciprocating mass/crankshaft pulsation-physics involved.

Another interesting discussion would be about "throw spacing" as in 90 degree throws of some four cylinder engines vs. 180 degrees found in some and I see it is also mentioned for high performance engines that yield the high-pitched sound as in Formula 1 race cars.


Alas, sadly, turbines seem to rule except to motorhead aficionados.

I recall from my balancing theory studies many years ago that radial engines had an odd number of cylinders because this was the only way to get the dynamic and harmonic forces balanced (plus of course a hefty floating counterweight on the crankshaft). An even number of cylinders could not theoretically be balanced. This balancing problem in turn created the required firing order.

It's more basic than that; in order to have an (approximately) equal firing interval, given a 4-stroke cycle, you always conclude that an odd number of cylinders is required.

For example - in 720° of crankshaft rotation, each cylinder must fire once (by the definition of a 4-stroke cycle). With 5 cylinders, the equal firing interval is 720/5 or 144°. So the cylinders spaced 72° apart satisfies this paradigm.

Note to the purist: Because of the master rod/articulating rod geometry, only the master cylinder fires exactly "on schedule". The other cylinders are either a fraction early or a fraction late because of the rotation of the articulating rod on the "knuckle" pin. The magneto cam is modified to match this.

Thank you for your replies. I understand the physics of a 4 stroke power delivery and the generated crankshaft pulsations in the operation of a radial engine and your good postings cemented my understanding of "odd cylinder requirements."

Though not mentioned specifically, it seems the considerations that apply to cylinder number and arrangement in a radial engine would also be a factor in the sixty degree cylinders of a V-6 & V-12 engine as opposed to ninety degrees for an 8 cylinder engine. Thank you both very much for the answers.

Interestingly, there was also the Allison V-3420,a 24 cylinder engine that was essentially, two V-1710s mated together, designed for the General Motors P-75 Eagle. It was built with its calling specifically for contra-rotating propellers (on the P-75) and was "cutting edge technology." It had been scheduled for the Lockheed XP-58 Chain Lightning but problems shelved it with the completion of one prototype. It seems our engineers surpassed the Germans on this one.

These aircraft were put forward to fill a need for a fast-climbing and high-flying aircraft to escort bombers in Europe. They were both dropped of course when the tides of war began turning against the Germans and in the Pacific, our B-29s were able to conduct missions unescorted because of their speed and operational altitude made interception almost impossible. Also the P-51 nicely filled the escort role in Europe once it was mated with the Packard license-built Merlin. It is a very interesting concept to read about and fortunately, literature about them exists and is available on the internet.