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Coffman engine starter (wikipedia.org)
58 points by zeristor on Nov 4, 2018 | hide | past | favorite | 15 comments

Fun fact: A not entirely equivalent, but comparable starter was used on the Titan II ICBMs and Gemini launchers, specifically the LR87-5 and LR87-7 rocket engines (which used a hypergolic fuel&oxidizer combination)

A simple (read: I don't understand it better yet) explanation is this: A starter cartridge was placed in the turbopumps of the engine, that ignited and spun up the turbopumps (technically, the turbine of the TPA which then turns the pumps), which then fed fuel and oxidizer into a) the gas generator to sustain operation, and b) into the combustion chambers. The cartridges burned for about a second, and you can hear the screeching sound they made in this launch video [1]

[1] https://youtu.be/E87deQMLHoQ?t=185

Cartridge starters are common on Jet engines too for cases where you need to get them started ASAP (i.e. military).

Fun fact: most airplanes have a smaller turbine used to start their larger ones. The ones that don't use a mobile turbine cart for the same purpose. It takes a lot of energy to get them started.

And if you're out of cartridges - a rope and a pair of felt boots save the day


Some thought or past experience has gone into that I'd say. Using the two boots in series to give a longer pull is pretty clever.

That was almost-standard in 1920s-1930s.

A rubber cord, a single felt boot (since most propellers were two blade), two-three men: one holds the propeller, others pull the cord. When they can't pull it any more, propeller is released.

Main problem was to warm up the engine in winter. For liquid-cooled ones that was done by repeatedly draining the system and refilling with hot water. I don't remember what they did with air cooled ones, maybe a blower of some kind, or just a blowtorch to the cylinders. There aren't many options on a snow field out somewhere in nowhere.

Brave. That could have been some really bad rope burns or worse if the rope got tangled.

These appeared in Flight of the Phoenix I believe.

The original, not the remake.

They sort-of appear in both, but in the original [1] they're explicitly mentioned and used to build tension, whereas in the remake [2] they're not mentioned explicitly, but the engine is started with one.

[1] https://youtu.be/IACjOvyx5hs

[2] https://youtu.be/wIPHWAwPxA0

According to the Wikipedia article linked above, it was included in the remake as well (I haven't seen it):

> The starter became famous as a plot device in the 1965 movie The Flight of the Phoenix, in which pilot Frank Towns (James Stewart) has a limited number of cartridges with which to start the makeshift aircraft's engine; this was also featured in the 2004 remake of the film.

B-52 jet engines can do cart starts as well.


The SR-71 didn't use a cartridge starter, but an AG330 cart with two V8 engines mounted in it to get the jet's engines RPMs up high enough to start.


"Some versions of the Rolls-Royce Merlin engine used in the British Supermarine Spitfire used the Coffman system as a starter."

But not all of them.

I wonder how tight the tolerances were on these engines?

When the U.S.A. entered WW2 it was Ford that tackled the problem of making aero engines en-masse. Ford took Rolls Royce designs that had been used for the war thus far (the U.S.A. being a late entrant) and realised that the blueprints provided were not fit for their purposes.

Until then Rolls Royce had been making each and every engine in a fairly bespoke way with the parts not exactly interchangeable between engines. Tolerances varied so fettling was always required. Ford fixed this and delivered precision engineering for a much better product.

Were the Rolls Royce versions of the engine the ones that needed the Coffman system with the superior Ford versions not requiring it?

That is my guess.

This was not the end of really-difficult-to-start engines though. Motorsport took it to a whole new level in the post war years.

Aero style supercharging didn't last for very long in the pinnacle of motorsport - Formula 1 - due to the thirstiness of the engines. Naturally aspirated engines (with the Ford Cosworth DFV) ruled the roost for many decades and then Renault came along with the turbo. This changed everything. However, to get the turbo to work precision engineering had to solve the problem of extremely high pressure gasses wanting to escape past the piston rings.

To fix this the pistons were made 'larger' than the cylinders. So at room temperature, with a cold start, there was no way for mere mortals to hand crank the engine. A very big starter motor in the garage was needed and only at operational temperatures with a little bit of thermal expansion could the engine run freely.

The flywheel was very light on these engines so only true drivers could keep these things from stalling, and if stalled whilst on the track, that was that, finito.

BMW made the most legendary turbo era engines, 1400 horsepowers in qualifying trim, with the engine having to be rebuilt after a handful of laps. The blocks for these engines came from their 4 cylinder road cars. According to legend the key ingredient for the strength of these engine blocks was urine and cold outdoor weather.

US built Merlins were made by Packard not Ford. The Ford factory in Manchester did make lots of Merlins too but they were to the Rolls-Royce design.

Wikipedia only lists the Merlin 32 as using a Coffman starter, as it went into naval aircraft maybe there was a requirement to be able to restart an engine in flight.

Thanks for that. Elsewhere on Wikipedia there is the Merlin XII as having this feature:


...beginning in 1939.

Ford - Manchester UK only got going in 1940.

I didn't realise that Ford in America turned down the job, that must have been Mr very contrary Ford for you!

I must have gleaned that 'fact' regarding the Rolls Royce blueprints being no good for Ford from the History Channel. I do wonder though about how much Ford thinking influenced Rolls Royce and their shadow factories elsewhere in England, where they did use relatively untrained staff to crank out the volume.

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