Sintered con rods

John Murch · Post by **John Murch** » Tue Dec 08, 2015 3:47 pm

About 20 years ago, a well known producer of Bentlley (WO and probably others) produced con rods from a sintered material. I understand that this is akin to a form of casting. The preferable method is forging.
In the event of failure of these rods, it seems that they fracture rather than bend, the results to the engine can be catastrophic.
Do any of you engineers know more?

John

Christopher Carnley · Post by **Christopher Carnley** » Tue Dec 08, 2015 5:16 pm

Powder technology was developed during WW2 as a means of making small parts economical of material without machining.
The process involves the heating of (numerous) hydraulically mould pressed alloys, some mixed with graphite,and heating them in a controlled environment to fusing temperature. (Oilite too!)
Tungsten and other carbide tool tips are made this way.

The tungsten filament in lamp bulbs is made by pressing powdered wolfram in a mould,then pressing the formed bar at red heat and progressively drawing it out into the very fine wire, mechanically. There is a good UO film that show the details, in detail.
BMW were one of the pioneers of sintered connecting rods and introduced a means of fracturing the big end across the eye such that the parts were screwed up in the exact same position. The gears in your angle grinder are all made of sintered materials.
I have seen quite a few forged rod failures, but I do not know of any failures of correctly installed sintered rods.
Unless some one knows differently.

John Robins · Post by **John Robins** » Wed Dec 09, 2015 11:05 am

http://www.pickpm.com/intropm/intropm.asp?locarr=1

Follow the link through the narrative. I wonder how far the process has developed since 20 or so years ago? I don't think I'd be prepared to trust a sintered con-rod that was that old, not due to its age per se, but maybe the process wasn't so highly developed then, and especially in a WO block that would be hard to replace.

Christopher Carnley · Post by **Christopher Carnley** » Wed Dec 09, 2015 2:00 pm

Yeah, well that is what I said, without having to look it up!

The word is derived from "cinder".

John Robins · Post by **John Robins** » Wed Dec 09, 2015 5:02 pm

I thought that the additional information might be of interest, you haven't caused me to change my mind. I started by looking for GKN Bound Brook, but apparently they no longer exist under that name.

Christopher Carnley · Post by **Christopher Carnley** » Wed Dec 09, 2015 5:42 pm

Just joking, as usual.

However your article didn,t have the Bloxham process, that started it all.

Look in GKN, Sinter Metals, for the Forged PM (powder metallurgy) for your co-rods.

Still in these days, the Dutch have a judgemental, fat, hirsute old geezer, called Sinterklaas, who goes around with a dirty looking character called Swart Piet, and if you have been at all naughty during the year,you are rewarded with a cinder, or a carrot if you are lucky.

John Murch · Post by **John Murch** » Wed Dec 09, 2015 9:35 pm

Thank you Chris and John, all very interesting, I have been told of two cases of sintered rods failing in WO cars which effectively cut the engine in two.
Perhaps the older sintered rods are best avoided.

John