Crankshaft Bearings: Types & Applications

Hello,

I need to manufacture two crankshaft bearings for a single-cylinder diesel engine. Can anyone tell me what material I should use?

RG7 (CuSn7Zn4Pb-7-C-GC) or GC-CuSn 12 (Gbz12) or something else?

best regards
flat-roofed

Hello,

flachfeiler wrote:

I need to manufacture 2 crankshaft bearings for a 1-cylinder diesel engine. Can anyone tell me what material I should use? RG7 (CuSn7Zn4Pb-7-C-GC) or GC-CuSn 12 (Gbz12) or something else?

I'm sorry, but I haven't read such a ridiculous question in a long time. It's like asking: "I want to buy a car, how many horsepower should it have?"
The material properties depend on a variety of factors, including specific bearing load, bearing dimensions, lubrication conditions, operating conditions, etc.
Without some initial information, you won't get a better answer.

Best regards, Uli.

Hello Uli,

Based on your first two sentences, I thought you didn't have a single coherent thought in your head. Then, with the following sentences, it got better, and it became factual again.

Since I don't have any training in automotive or related fields, I have to ask what might seem like a "stupid" question. Regarding the technical specifications, I can provide the following information:

Piston diameter: 110mm.
Engine displacement: 1280 ccm.
Maximum speed: 1500 RPM.
Power: 13 HP.
The engine is air-cooled using a fan.
Pressure-fed lubrication.
Storage compartment on the flywheel side: inner diameter 80mm, outer diameter 91mm, depth/width 39mm.
Front bearing: Inner diameter 80mm, outer diameter 91mm, depth/width 49mm.


best regards
flat-roofed

hello,

flachfeiler wrote:

Since I don't have any training or experience in automotive or related fields, I have to ask what might seem like a "stupid" question.

If you can manufacture such parts and correctly suggest the materials, then you have basic locksmithing knowledge. So, please don't pretend to be an unassuming, clueless person, but rather consult your reference book, which explains how to determine sliding bearing forces and the minimum material requirements. Otherwise, this is a broad field that involves many sciences, such as tribology ("Sommerfeld number"), materials science/dynamics (material fatigue strength), vibration technology (okay, still relatively simple to calculate for a single-cylinder engine), etc. I can't think of anything else right now .
In other words, I also don't know what kind of material you should choose .
I definitely wouldn't use GC-CuSn 12 (Gbz12); it absolutely needs to contain lead. At most, you could use it as a supporting shell and then cast it with a bearing material. But whether you want to go through all that effort, I don't know; that's something you usually do with steam turbines in power plants .
If I had to do something like that, I would ask an experienced engine mechanic (or, 30 years ago, the village blacksmith, who has since passed away). Practical tips are definitely more useful than theory in situations like this.

Best regards, Uli.

Just a thought: I recently heard that some backyard mechanics in this area used to solder bearings (using soft solder, a tin/lead alloy). I wonder how they got them round again – maybe with a tool for re-honing?

"These massive bearings for such a small engine look like they belong to a historical engine. Consequently, the bearing loads are very low. Why not simply use 80-series bearing shells designed for a modern diesel engine and fill the diameter difference with brass? Then you'll have a four-layer bearing that, with proper lubrication, should far exceed the remaining lifespan of the engine. Does the engine have a pressure-fed lubrication system?"

Best regards.
Christian.