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

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. :)

Firing order of the P & W 1830
 

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.


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.

Engine Cylinders & Firing Function
 

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.

R-4360 Firing order
 

I read your post as to what would be the firing order of a P/W R-4360 and will post it for what it's worth today in the world of jets.

The order is read from left to right as for example A1-B5-C2-D6 and so on.

A B C D
1 5 2 6
3 7 4 1
5 2 6 3
7 4 1 5
2 6 3 7
4 1 5 2
6 3 7 4

Working with about 45 of these engines all our crews had to know the firing order to maintain and repair these "CORN COBS" as they were referred to.
The whys and wherefores are subtle and complex and it's too late in the morning for all of that___maybe later.
Hope that satisfies for now!

Cylinders and firing order
 

Info in conjunction with your post is that balance in the engine is important but the dynamic balancer takes care of that problem.
The rods except the master rod are articulated, and because they are, the magneto cam is compensated to address that issue.
The magneto cam compensation is actually cut into the cam and is slightly differernt for each articulated rod so that they will fire at the correct time to give the engine the proper peak pressure point (2-10 degrees after top dead center) and power overlap to continue the "flywheel effect" in the engine.

Cylinder location
 

The main reason the cylinders are offset is not for any real scientific or structual reason it was done for the purpose of cooling and the offset of them led to exposure to frontal cooling area with a large result.

Spark Plug Change
 

Usually a S/P change on the Stratocruiser took about 4 hours finishing about lunch time and there were 2 men on each engine. Same thing for a C-124 Globemaster and also on a KB-50-J.

I hope that the Mods take no offence to this. Google 'Aircraft Engine Historical Society' to find out more re engines.
Thread drift, the company that I worked for in the 1950`s had Super Connies. They did an engine run on #2 one night, flames were coming out of the intake and exhaust at idle power and take off power, but it seemed normal around 2000 rpm. Engine shut down and ignition timing checked, ran again with same result, this was tried many times. Eventually it was found that the fuel injection pump had two master splines instead of one, it was fitted 180 degrees out of sync.

When the makers give Murphy a leg up, do the riggers and fitters have any chance? :ouch:

Just an aside: It is nowhere writ in letters of fire on tablets of stone that the firing intervals must be evenly distributed around a circle. See H-D, Vincent, latest Norton, some Hondas etc.

After an excellent landing you can use the airplane again!

If you look at a radial engine of the double row type from the prop shaft end and see the cyls. in firing order number for at least the first five cylinders you will get a better understanding of the reason for the sequence of events of the firing order and very basically it will show the production of equal and opposing power strokes in the full cycle and will give you a look see at the degrees that is a set angle for each engine.
The R-4360's were referred to have four rows with seven banks of cylinders.
One comment on the thread talked of a double spline on the Bendix fuel injection
pump that could be put on 180 degrees out of time. I can asssure all that was never the case, all the injection pumps had only one master spline on the shaft and an indexing point of attachment and they were very particular to the R-3350 turbo-compound engine on the Super Connies.

We could always get plugs out- we were very careful to not break off plugs by using a torque wrench to remove and if the wrench clicked at the preset we would go to Plan B, which was warm the cylinder with a heat lamp then pack the
special plug socket with dry ice and 99 out of 100 out came the plug. Very seldom did we need the machinist skills.

Wright Aeronautical Engines:
R-570 5cyl. (J5 Spirit Of St. Louis) Whirlwind
R-790 7cyl. Whirlwind
R-975 9cyl Whirlwind
R-1820 9cyl. Cyclone
R-2600 14cyl. Double Cyclone
R-3350 18cyl Duplex Cyclone


Pratt & Whitney Engines:
R-985 9cyl. (L20 Beaver) Wasp Jr.
R-1690 14cyl. Hornet
R-1830 14cyl. Twin Wasp
R-2000 14cyl. Twin Wasp
R-2800 18cyl. Double Wasp
R-4360 28cyl. Wasp Major

This is pretty much how I got to understand some of the garble with engines.

Ahhh...I think you missed a Wasp. ;)

Allison V-3420
Just as a matter of interest, Kermit Weeks' Fantasy of Flight Museum in Florida has one of these.
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