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I Forge Iron

Motorcycle con rod


BeaverNZ

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Hey guys has any one had a go at forging single piece conrods for an engine I am buliding a dirt bike with a heavily modified engine and I am set on having a go at making my own. I know I could by one or have a machine shop make but thats not me. I intend to use a high tensile case hardening steel so I can get the needle roller positions hardened by carburising I have a rough idea of how to start but thought I would see if any one else has been down this track Cheers Beaver

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Sounds like a highly technical procedure there. For safety's sake with conrods, you would have to get it right!

Think you might be on your own with this one, mate. Let us know how you get on.

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I several things that you need to address.

How are you going to get the shape? Closed die, or hand forge and machine to shape?

What alloy? And why case harden when you can get steels that you could harden directly?

How are you going to control grain growth/direction?

Is there a commercially available rod available? 

Look for a needle bearing that has an outer race to eliminate the need for a hardened and honed surface.

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I reallise I may end up with a ventilated engine case if I get it wrong I have been doing alot of thinking about this one and I will use a EN36A or EN39B type of alloy the reason why is this what OEM conrods are made from and if you have ever wondered why single piece rods are copper plated is to mask where you dont want the rod to be carburised so it remains tough and not hard and brittle so just where it needs to be hard is where the needle rollers run. The hardeness reqiured is 60 rockwell. I have been experimenting with a sort of semi enclosed die made out of bissalloy 400 and the rod will req a bit of hand forging before hand. I cant use a roller bearing with an outer race though I had thought about it there isnt engough room and would add too much weight, yes I could get one made but I wish to do it myself if it was easy everone would be doing it Thanks for the replies and if you have any suggestions Im all ears Cheers Beaver

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