Metal selection

[jerrybilt]

Hello all,

Just some advice and tips from you before I go ahead and spend my " hard earned".

I am starting to build a hit and miss engine from a kit of castings but still need material to complete the job.

The issue is in the selection of steel for the crank shaft and conrod. My first thoughts was to michine these from 303 stainless as the end product will stay "bright and shiny". Is this a good idea or stick with mild steel? The crank will be of buitl up construction as this is well within my capabilities. Machining from solid bar stock is not,

Your thoughts will be much appreciated,

TIA,

Jerry.

 

[Tin Falcon]

what size engine is this ? power output? and will this be a working engine?


a small engine that just runs for fun at shows will not have a lot of stress on the crankshaft.

the first thing that comes to mid is 4130 standard aircraft grade alloy steel.

drill rod a possibility if you look for shafts from Master carr you get 52100 or 1566.

4140 is also a good option 4140 L is more machinable.

there is always trade offs and how you fabricate makes a big difference . if you are going to machine from solid go with 41L40 .

if welding 4130 is a better choice.


many options will work. and I am sure other advice /opinions will come forward.
Tin

 

[jerrybilt]

Yes this will be a working engine. I imagine it will not go above 1,000RPM
if one loads the engine I'm sure it will not put out more than 1/3 hp at the shaft
Engine capacity is 75cc ... 1.5' bore x 2 1/8' stroke
Each (of 2) flywheel weighs 3.0kg

The crankshaft looks like :

http://i1340.photobucket.com/albums/o729/JRW29/crankshaft_3139_zpsc0595af9.jpg

and the conrod looks like:

http://i1340.photobucket.com/albums/o729/JRW29/conrod_3139_s_zps0f648fe6.jpg

The plans said mild steel but I'm thinking bright and shiny.

Thanks for the time.