A little movie trivia?

[svejkovat]

Having an argument with a couple of others around here about a segment in the movie "The World's Fastest Indian".

For anyone unfamiliar, the guy is a garage mechanic in New Zealand in the '50s. He has a pet Indian motorcycle that he keeps tinkering with make it faster. In the movie, he's shown casting replacement pistons for it with scrap aluminum, using a coffee can crucible and hand made molds on his garage stall workbench.

We seem to be split on this, none of us having an real metallurgical background. Is this hokum? Is it possible to accomplish something like this with such rudimentary tools, install such "home brewed" pistons in a 1950 era Indian motorcycle engine, and then run it at 190mph at the Bonneville salt flats?

I'm a disbeliever. Am I wrong?

 

[MikeHalloran]

Bert Munro was featured in HRM several times.
So far as I know, the story is true.

The manufacturer of Indian motorcycles was pretty much gone by 1950. I think Bert's Indian was a 1920 model... which had had pretty nearly all its parts replaced.



Mike Halloran
Pembroke Pines, FL, USA

 

[MikeHalloran]

Oh. I don't think anyone would pour molten aluminum on a workbench. The story was usually written that he cast his pistons 'in the ground', which is much safer.



Mike Halloran
Pembroke Pines, FL, USA

 

[MikeHalloran]

Sorry, I spelled his name wrong.

http://en.wikipedia.org/wiki/Burt_Munro

Mike Halloran
Pembroke Pines, FL, USA

 

[redpicker]

No Hokum, Kemo Sabe.

Actually, aluminum is one of the easiest metals to cast. While producing a specific alloy with such a set-up might be difficult, I believe in the movie he was just metling down used pistons which would not require any alloy additions. The melting point of most aluminum alloys is around 1200F (well, I guess that would be around 650 C in Australia), which can be easily done with the equipment shown in the movie.

Great movie, IMO.

rp

 

[swall]

I did something like that when I was in college, working on my metallurgy degree. I cast a couple of finned exhaust clamps from aluminum casting scrap obtained from a scrap yard and melted in a crucible made from a piece of 4" dia. steel pipe with a piece of sheet welded to the bottom. I used an oxy-acetylene torch for the heat and the molds were made from plaster of paris.So, yes, it is doable--you can even buy hobby foundry kits for this.

 

[svejkovat]

But was he running 'home brewed' pistons at Daytona in a '40s era two cylinder hopped up sufficient to push a bike upwards of 200mph? (as the movie suggests). My hunch is that, despite the fact that the original molds seem to exist, that he eventually must have come up with some NOS (new old stock) originals. The parts were out of production, but it was a fairly popular bike, and not really that long out of production. The likelihood of pistons being available at the time was actually pretty good.

Not to put too fine a point on it, (for some reason this subject really gets mr. munro's fans agitated) but I'm still left wondering a little at the possibility of a little mythmaking in action here.

The possibility of casting a 'object' out of molten aluminum alloy seems entirely reasonable to me. I suppose given slightly more robust materials you could cast belt buckles and other doodads on your workbench out of more exotic titanium alloys. But a turbine replacement for a modern General Electric passenger jet engine?

The thing that troubles me still is, while a piston for a two cylinder motorcycle engine is a far cry from a jet engine turbine, there has to be some point where you have to wonder at the feasability of accomplishing something like this. An aluminum case cover? Perhaps. Front end clamp for the fork braces? Sure. Connecting rods and pistons? Hollow pistons with relatively thin skirts? All the internal dimensions to accomodate the con rod and bearing. Sufficient grain integrity and dimensionality to withstand the enormous stress, vibration, and near 1000 degree conditions inside of a '40s era two cylinder engine that has been modified to push a bike up 200mph?

I don't doubt any of Munro's accomplishments. He probably even ran such home brew pistons at one point, for short durations on his back roads. I only wonder if we're not getting a little bit of dramatic glossing over here to spice up his reputation.

 

[svejkovat]

Case covers, Fork clamps, or indeed as you were able to produce, exhaust clamps.

From what else I've gathered, he eventually produced his own jugs out of cast iron pipe! Now he has the option of boring the pipe to fit whatever pistons are at hand of nearly the same dimension. Even New Zealand in the fifties would have offered some plentitude of second hand pistons to fit the bill.

This is a minor obsession only because this sort of dramatic license irritates me. It never takes much real research to peel away the accreted myth of the Edisons, Lindbergs, Guevaras, Jeffersons, Fords, etc. All extraordianry men. So why do we insist on gilding their accomplishments?

And I'll go away now. This has gotten pretty off topic for this forum. But thanks very much for the responses.