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Con-rods lightening????

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Con-rods lightening????

Post by mrbeige on Tue Nov 24, 2009 3:01 pm

Right, just seen a build thread on another forum, where a guy had filed off some of the metal off the beam of a G60 rod. Surely this would reduce the strength of said rod?

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Re: Con-rods lightening????

Post by kevhaywire on Wed Nov 25, 2009 2:32 am

Depends where he filed I guess but I'd be more concerned about making them unbalanced!

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Re: Con-rods lightening????

Post by mrbeige on Wed Nov 25, 2009 4:13 am

Yeah I did think that too.

I'll try and find a picture later...

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Re: Con-rods lightening????

Post by mrbeige on Wed Nov 25, 2009 5:50 am

Ok, it seems that the process was done to get the rods all the same weight, which seems fair, but surely when you are talking about a complex shape like a con-rod, that is in a rotating mechanism, wouldn't you want to make sure that the weight at each end was equal for each rod, rather than just measuring the overall weight??

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Re: Con-rods lightening????

Post by dirtytorque on Wed Nov 25, 2009 5:55 am

mrbeige wrote:Ok, it seems that the process was done to get the rods all the same weight, which seems fair, but surely when you are talking about a complex shape like a con-rod, that is in a rotating mechanism, wouldn't you want to make sure that the weight at each end was equal for each rod, rather than just measuring the overall weight??

Yes,it is not just a case of making sure they weight the same.
I discussed this a few weeks ago with the engineering firm that did all my work.
Balanced means exactly that.
Balanced.

What application was the guy from vortex using the rods for?
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Re: Con-rods lightening????

Post by mrbeige on Wed Nov 25, 2009 2:03 pm

Found the pics.....

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Re: Con-rods lightening????

Post by VEEDUBBED on Wed Dec 30, 2009 8:55 am

I've never understood why peeps do this,what gain? i mean,ok if your dealing with a cast con-rod fair enough,you'd wanna get rid of the stress
raiser/cast mark running down the center of the rod but as the G60 rods are forged steel i don't see the need.
I've yet to come across a damaged/bent G60 rod,they are extremly strong buggers.
Even after polishing the beam you'd still be left with the balancing 'pads' on the very top of the rod,another possible stress raiser when revvin' to 8000+rpm but i don't see PG rods gettin near that rpm level.
Am i missing the point?.

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Re: Con-rods lightening????

Post by Yandards on Wed Dec 30, 2009 10:22 am

Can't see the point in removing stress raisers but I can see the point in weight matching followed by dynamic balancing.

You are never going to get an exact match but by getting it closer you should ensure a smoother running engine which reduces parasitic loses through inbalance.

You really want to get the rods, pistons and crank balanced as a rotating assembly, so you need to provide the block too. This way it makes it easier for the folks doing the balancing to match up rods and pistons without having to remove a lot of material.

I had a guy called Steve Smith from Vibration free do my flywheel, rods, crank and pistons, wasn't huge money at £185 and most of that was for lightening the flywheel. I went over to his workshop a few times, really good bloke and he has lots of interesting stuff over there he is only too happy to talk about. Used to do BAR Hondas F1 wheel balancing so has to be pretty good!

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Re: Con-rods lightening????

Post by JNLRacing on Mon May 17, 2010 1:58 am

You can lighten the rod that way without any strength issues as you are getting rid of surface weaknesses. In an ideal world in needs shotpeening afterwards for improved yield strength.
What I can tell you from that picture is that the rods will need balancing end over end again as they will no longer be in balance. It doesn't take a lot of material removal to make them out by 1 gramm.

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