Running Prototype Mild Steel Crankshaft

racecar builder

racecar builder

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Will mild steel do to machine a crankshaft and run the engine at idle and mid range for testing?

Vee twin and inline twin.About 50 cubic inches total.
 
Probably not, need to do the stress analysis if you really want to know. Harley?
 
They made millions upon millions of crankshafts out of cast iron, and I flogged some of them mercilessly without breaking them (broke rods, dropped valves, blew up pistons, but never broke a crank). Doing a stress analysis on a crankshaft is probably out of the question for most hobbyists, as you would need to do a dynamic analysis. The old engineering adage of "When in doubt, build it stout" may apply here, in which case I would recommend 4140 pre hardened. It's relatively cheap, machinable and strong and would give piece of mind. The inline twin would probably be less stressful as long as it has 3 bearings. A lot depends on how beefy the crankshaft is. Long spindly crankshafts without bearings between each cylinder or cylinder bank tend to be a problem anyway.
 
cjtoombs

Sent you a message.

If you are open to doing some machine shop work for us let me know.

We are in Desert Hot Springs and can get the work to you and back.

Can we skate by with something less than the chrome moly 4130?

We could run a compression release and just keep it barely running for what we're doing.

Have a good one
 
Well, you could always build it and find out.

I used to build highly modified Briggs & Stratton motors for kart racers and I have seen cast iron crankshafts break, sometimes quite dramatically....
When you say you're just doing some testing I kinda wonder what you'll learn if you don't push it hard. I still have my small engine dyno if you're interested in doing development work.

Here's a tiny picture of what we built.

RACEREADY_305.jpg
 
BTW, the billet cranks we used were made from 4340 Hardened Chromoly Steel and I've seen them break too. Now, there might have been some nitro-methane involved in that action....

I didn't build the cranks but I would assume they were hardened after machining.

www.arcracing.com

6586 Briggs 305 Crankshaft Stroker 2.637"

ARC Billet Crankshaft Briggs & Stratton Intek 305 Stroker OHV Animal 1" journal Crank gear
www.arcracing.com www.arcracing.com

John
 
Hi John

Another member told me our engines are like 'table top' engines.No load.

So we can get away with a lot.

Have to check shaking and things like valve timing first.

I am familiar with nitro.Hillborn nozzle changes as percentage of nitro goes up.

Our test engines just run on desert dune buggy 110 Sinclair racing gas.

Sent you PM.About karting too.
 
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