Questions about bearing shells .

[stragenmitsuko]

I would like to brain storm a bit about machining bearing shells for a vintage tractor .
New ones are no longer availale , the old ones ar worn to the steel backing and have way to much clearance .
Altough there are a few parts sharks that sell oversized shells , a full set of shells would cost way over a 1000$ for
a three cilinder engine . That imho is plain robbery .

So no alternative then , I'll have to machine them myself . I do like a challenge it'll be fun .

The originals have a steel backing and some red copper like material . Possably there was white metal
on the copper once , but I can't find any trace of it .
Possably the red copper is some bronze alloy , I don't know .
The shells the parts sharks offer are made of a lead/bronze alloy .
Max rpm of the crankshaft is 2200 , a slow running engine .
Both crank and conrod bearings are nominal 75mm ( abt 3 inch ) and 40 mm wide .
There's an oil pump that pressure lubricates both main and conrod bearings .

First I'de like opinions on what material to use :

My supplier has these materials availble :
Phosphor bronze
Cast bronze bushings
Selflubricating bronze
Various ali alloy's like 6060 etc .

The reason I'm adding aluminium to the list is that I visited a crankshaft shop .
They couldn't help me , but the owner showed me a set of aluminium shells that
were custom made for an alfa romeo race engine . He said they performed very well .

I seem to like the selflubricating and the cast bronze .
Both can be bought in bushings that are close to the sizes needed .


Pat
I will upload a couple of pictures of the original bearings tomorrow

 

[stragenmitsuko]

Pictures of the rod bearings and the main bearings .

The rod bearings are worn down to the steel backing ,and one
crank journal has a tiny bit of scoring .

The main bearings are also in pretty bad shape , but there's a reasonable amount
of the copperish metal left .

 

[Chiptosser]

You might want to get with a engine rebuilder to check for availability. Having the crank ground may give you more options of bearing sizes. Also line boring of the crank gives you more options.

 

[stragenmitsuko]

Yes I did contact several companys offcourse .
One of them makes crankshafts from scratch for vintage cars , tractor pulling etc .
He had an ordner full of bearing sizes , none of them was a match .

Only two options left :

Make my own , or pay close to 1000$ , and on top of that the crank
needs to be ground to the next size .

So I'm gonna give it a try , I have very little to loose have I ?
If it doesn't work I'll still have option 2 available .

I think I'll go with selflubricating bronze .
It's one of the softer bronze alloys , containing 10% Sn and 10% Pb .

 

[cds4byu]

I know a guy who has a company that makes custom babbit bearings. I don't know how much he charges or if they would work for your tractor.

I can give you contact information if you'd like.

Carl

 

[Basil]

It sure would be nice if you could find someone to rebabbit those bearings. Babbit will tolerate a degree of contamination due to the it’s soft nature which is one of the reasons it is used so widely. A rogue metal partial say will be pressed into the soft Babbit instead of wearing a mark into the crankshaft.

 

[Basil]

Just another way thought! Could you use a set of shells that is more readily available ie correct crank diameter or crank ground to suite and make half sleeves to fit between the new bearings and the engine case. This is sometimes the fix for a spun bearing that has oversized the crankcase.

 

[Drawfiler]

I have heard of people who can remetal your old shells here in the UK, this may be an option.

 

[Steamchick]

Hi Pat,
As I worked in Engine design "once, way back in the late '80s"... I have a few comments on bearing materials.
I assume the engine has a forged crank, not a cast-iron crank? - The material is important for bearing metal selection.
Steel shells of this design have complex coatings for the bearings, but that is just because the bearings when mass produced can use steel for the main volume of metal that makes the "strong" bit. So, you can make a bronze bearing shell - if your machining is good enough!
The surface would have been a fairly hard bronze (NOT the self-lubricating softer bronze!), cast onto the surface of the steel, and Broached to size (As a pair in a holder, you could finish by using a con-rod, and turned in a precision lathe).
To make the surface bronze, you can use a brazing technique to lay on a "tinned surface" of bronze. Using the correct metal and associated flux. I would use Phosphor-Bronze to re-surface the shells...
The difficult bit is that "commercial" bearings are coated (electroplated) with a few microns of Indium - to prevent acidic corrosion from the blow-by gases that emulsify in the oil and corrode the phosphor bronze due to electrolytic reactions versus the iron in the engine. If you cannot get bronze electroplated with INDIUM, then change the oil more frequently to wash-out the acidic old oil. (Modern oils contain zinc compounds to neutralise the acidity - until that is all used-up. Hence the service intervals are longer on modern engines (Oil additives plus less blow-by gas) but MUST be maintained as there isn't much reserve for exceeding service intervals!). Use a modern oil (SF/CC or better) - but of the correct (SAME) viscosity as the original oil.
Bronze is selected for engines with a higher bearing pressure - I.E. engines for diesel combustion, high durability, or racing, or high-performance engines that need forged crankshafts.
Aluminium alloy bearings are good for cast-iron crankshafts, as the silicon in the alloy has molecular hard nodules that polish the cast-iron surface. (According to the metallurgy and tribology engineers I worked with and Glacier Bearing experts). But if an engine had Bonze bearings you cannot simply fit Al. alloy replacements as they cannot take the loading and will suffer fatigue failures within the alloy. - You won't know until you hear a LOUD knocking from a failed bearing.
Also, I would NOT use white metal, as it simply will fail quickly due to the low hardness of white metal. It cannot simply replace a bronze bearing.
BUT please research the actual bearing shell dimensions versus catalogues of bearings, as many old designs exist as new shells simply because they were in "standard" sizes. (In the 1960s I had to manually browse the Vandervell catalogues for bearing shells of the same size as the old ones removed from over 30-year-old engines).
Hope that helps you decide what to do?
K2

 

[stragenmitsuko]

This is a very helpfull reply on the material choice .

Just like you suggest , I was gonna make a "fake" big end with a morse taper no5
so that it will fit the lathe spindle to turn to final size .

Is there a reason why you recomend phosfor bronze over selflubricating ?
I can still change my order
The selflubricating I'm talking about is not thesame as the sintered or oil lite bearing material .
It is a Cu / Sn / Pb alloy and has a hardness of 65 .

Good tip on the oil .
I doubt that I'll be able to elctroplate the shells .

thx
Pat

 

[Steamchick]

Hi Pat, The Tin-lead addition to the copper doesn't harden it much - but I am not a metallurgist so cannot be sure without checking. I suggest you do so.
Tin and lead are added to soften materials, usually, as far as I understand... ? - Check out the tensile strength and fatigue resistance compared to phosphor bronze in case I am away with the mixer!
Phosphor Bronze is used to harden and increase the strength of Copper. If the original bearings were bronze, then they would have been the "stronger" material of choice to resist fatigue. In a "higher duty" bearing. In real terms that probably means a hundred times more lifetime. So, if you want the rebuild to last, then you need Phosphor Bronze bearings replacing Phosphor Bronze lining of the steel shells.
If I were designing any engine for industrial use (like a tractor, that does 10s of times more hours running under load than a domestic car engine!) then it would have a forged crank and bronze bearings. (Even if the bronze is actually only <0.010" thick on the steel backing shell!!). Reason: The forged steel crank is much stronger than cast iron, consequently, to have a practical engine, the size of the crank is considerably smaller - strength for strength - compared to the cast crank. To get similarly suitable bearings (smaller for the same load or taking much greater loads for the same size) the design optimises on Bronze as the bearing material. It is a nice happy marriage that Bronze bearings suit forged steel cranks and softer (cheaper) bearings suit (cheaper) cast iron cranks.
But that is only my opinion.
Regards,
K2

 

[william_b_noble]

I still have some ingots of Babbit metal but I'm on the wrong side of the ocean. for older machines with babbit bearings, it's common to repour them yourself. there are books and books about this.

 

[Steamchick]

Some further information from the experts...

https://www.thomasnet.com/articles/metals-metal-products/all-about-bearing-bronze/
An extract from Vandervell Bearing materials catalogue:
https://btsecuresession.com/connellmarketing.co.uk/vandervell/materials/files/basic-html/page4.html
VP2 is a lead bronze material which is continuously cast onto steel strip. Casting and quenching conditions are controlled in order to produce a microstructure with vertically orientated
bronze columns. This gives the bearing material its superior strength increasing its compressive load capacity. When plated with lead indium it has become the favoured material for racing engines. The combination of a lead tin alumina overlay with VP2 improves wear resistance by a factor of two when compared with a lead tin copper overlay. In addition
the shaft conditioning properties are enhanced and fatigue resistance is improved.

===>> VP1 differs from VP2 in its reduced lead and increased tin contents, giving it a higher load carrying capacity. VP1 is used unplated in bush applications and overlay plated in very highly loaded half bearing applications.

VP3 is similar to VP2. It is supplied with either a lead tin copper or lead indium overlay.

Very high shock and load carrying capacity and high temperature resistance. Excellent for cup drawn seamless bushes such as tappet rollers and spring eye bushes.

A general purpose bush alloy. Good for high speed high load applications with very good compatibility and conformabilty without sacrificing strength. Good for applications involving
some foreign matter and/or misalignment. A good choice for components that will be ball indented or graphited.

VP10 is a very high strength lead bronze. It has excellent wear and corrosion resistance and its load carrying capacity and shock resistance make it ideal for small-end bushes.

SP can be used for bushes or, when plated with lead tin or lead tin copper, for half bearings.
Good compatibility and embeddability. Used unplated for bushes and thrust washers subjected to intermediate oscillating and rotating loads. Used for heavy duty bearings when plated.
SX is a sintered material similar to VP2 but with a higher tin content. It is used unplated in bush applications or with a lead tin overlay in half bearings.
(Glacier SY is the sintered equivalent of VP10).
Thin sintered material has a high load capacity and, when overlay plated, good conformability, embeddability and corrosion resistance.
A material designed to have excellent conformability, without an overlay, and for use in light duty bush applications.

I guess VP1 is what you want. - More research needed?
Glacier Bearing co, took over the Vandervell business around 1992 - if I remember correctly.

Reading this, my memory had lots of errors...!! except for the basics of Bronze bearings for forged steel crankshafts and Aluminium 20% Silicon used with cast iron crankshafts.
K2

 

[ajoeiam]

Hi Pat,
As I worked in Engine design "once, way back in the late '80s"... I have a few comments on bearing materials.

snip

Use a modern oil (SF/CC or better) - but of the correct (SAME) viscosity as the original oil.

snip

Hmmmmmmmmmmm - - - - same viscosity.

IMO that's a right royal rat's nest!!!

I've run into too many engines where there seem to have been designed for running in only a tiny range of environments.

So I'm supposed to use only a 15W40 oil and I want outside starting capabilities in low temperatures (say even the -30 range never mind colder)?
Or I'm using the engine in a more constant higher load situation than its original implementation (small car diesel now being used in a more industrial situation).
I've found that changing that lubricating oil viscosity actually was useful and without doing any testing - - - well I had lower oil consumption and I think better engine life. (I might start with the recommended oils for break in - assuming I could do that say in spring or early fall but I sure don't get tied to inadequate recommendations.)

(Went looking for modern oil classifications - - - - I'm so very out of touch - - - - SP- - - CK-4 and I find there is even a Diesel F category (API charts). - - HTH)

 

[Steamchick]

If the manufacturer says straight 50W viscosity, then 5W is only good at -30 degrees to freezing... but is good for starting in the cold!
Too high the viscosity leads to overheating bearings through lack of cooling oil passing through the bearing, and consequential oil film breakdown and wiping the bearing metal.
Too low a viscosity and the oil film is likely to break down at the point of max oil stress, e.g. point of max load on the firing stroke.
So the nightmare is finding the oil viscosity for your climate if not what manufactures advise.
Below -30 or over +50 is usually beyond their range of recommendations.
Multi grade oils are very good, for the first figure being the "Cold equivalent" viscosity, and the second figure being the " normal engine temperature equivalent viscosity" which is really MOST important for oil pump, oil flow, pressure, cooling and lubrication of bearings.
Manufacturers spend thousands of hours testing and proving their engines for optimum long life - as per the owner's manual final recommendations. Deviate from that at your own risk. That is all I can recommend having spent 4 years in engine design and testing....
But if you know better, I am willing to learn?
K2

 

[ajoeiam]

If the manufacturer says straight 50W viscosity, then 5W is only good at -30 degrees to freezing... but is good for starting in the cold!
Too high the viscosity leads to overheating bearings through lack of cooling oil passing through the bearing, and consequential oil film breakdown and wiping the bearing metal.
Too low a viscosity and the oil film is likely to break down at the point of max oil stress, e.g. point of max load on the firing stroke.
So the nightmare is finding the oil viscosity for your climate if not what manufactures advise.
Below -30 or over +50 is usually beyond their range of recommendations.
Multi grade oils are very good, for the first figure being the "Cold equivalent" viscosity, and the second figure being the " normal engine temperature equivalent viscosity" which is really MOST important for oil pump, oil flow, pressure, cooling and lubrication of bearings.
Manufacturers spend thousands of hours testing and proving their engines for optimum long life - as per the owner's manual final recommendations. Deviate from that at your own risk. That is all I can recommend having spent 4 years in engine design and testing....
But if you know better, I am willing to learn?
K2

Hmmmmmmmm - - - - in my experience - - - those design engineers test for what they think is the normal range of use - - - and that's the rub.
What is being designed for is not always the use case being considered.

Interesting point - - - - engines built to tight tolerances don't always like multi-viscosity oils. Was explained to me that the tight tolerances increase the shearing of the viscosity improving molecules (long chain of course) which is why it used to be not that unusual to find engines where use of a multi-viscosity oil was deprecated. Likely not true for most of the last 40 odd years but having run a couple engines and having tried different oils in them found that for heavy use in summer application (not high heat only to perhaps 27 or 28 C but also not cold) a 30 weight oil seemed to function far better than a 15w40 and that 30 oil was far easier to find than 20W50.

Or maybe the polymers used more recently as thickeners have improved. (A 15W40 oil is a 15 weight oil with additives that thicken the oil to function as a 40 wt oil at say 75C (dunno exact points) or better. )

Personally I have moved to a 'house oil' that is a 5W40 and if the suppliers were more on the ball I would have bought a 0W40. In engines that are not prone to oil consumption this, imo anyway, is a reasonable solution for most engines. (Also using an oil that is gas and diesel rated for that matter.) Why I want the 0W40 - - - the pour point of the two oils doesn't change much but the time for oil to move from the pump to all lifters is different. That reduced time increases engine life appreciably imo. (Have heard that over 90% of engine wear happens at starting. That's why large engines often (afaik) pressurize the lubricating oil 'before' starting.)

 

[kuhncw]

What make and model is this tractor? Just curious.

Chuck

 

[stragenmitsuko]

1958 Porsche diesel 3 cilinder .

Bought it a year ago , it had been outside sleeping for at least 10 years . .
Took us only 15 minutes to get the engine running .
Hydraulics worked , brakes worked , gearbox seemed OK .
So I started he restauration with high hopes .

But then, : cam shaft damage , lifters damaged , bearing shells worn to the steel backing , cracked cilinder head , tyres desintegrated when removing them from he rims , clutch is worn ......
And who knowes what other corpses wil be found .

Second picture shows he oil sieve . The root of all evil .

 

[DavidBC]

https://silodrome.com/porsche-tractor/

 

[HMEL]

I would like to brain storm a bit about machining bearing shells for a vintage tractor .
New ones are no longer availale , the old ones ar worn to the steel backing and have way to much clearance .
Altough there are a few parts sharks that sell oversized shells , a full set of shells would cost way over a 1000$ for
a three cilinder engine . That imho is plain robbery .

So no alternative then , I'll have to machine them myself . I do like a challenge it'll be fun .

The originals have a steel backing and some red copper like material . Possably there was white metal
on the copper once , but I can't find any trace of it .
Possably the red copper is some bronze alloy , I don't know .
The shells the parts sharks offer are made of a lead/bronze alloy .
Max rpm of the crankshaft is 2200 , a slow running engine .
Both crank and conrod bearings are nominal 75mm ( abt 3 inch ) and 40 mm wide .
There's an oil pump that pressure lubricates both main and conrod bearings .

First I'de like opinions on what material to use :

My supplier has these materials availble :
Phosphor bronze
Cast bronze bushings
Selflubricating bronze
Various ali alloy's like 6060 etc .

The reason I'm adding aluminium to the list is that I visited a crankshaft shop .
They couldn't help me , but the owner showed me a set of aluminium shells that
were custom made for an alfa romeo race engine . He said they performed very well .

I seem to like the selflubricating and the cast bronze .
Both can be bought in bushings that are close to the sizes needed .


Pat
I will upload a couple of pictures of the original bearings tomorrow

There are good engineering reasons for using babbit bearings. A babbitt bearing is quickly run in and provides a smooth surface. Babbitt bearings have the ability to conform to small misalignment of the crankshaft. Its an art to fix them or repour the babbitt. If other materials are used the shaft alignment becomes critical while the shaft is running. Given what you said about the racing engine and aluminum I would go back and talk to them in greater detail. But the last thing you want to do is restore that engine and then have it put a rod through the block. If the shaft is scored you may have to use oversized bearings. Now there are copper lead alloys that were used which were 45 % lead and 55% copper so its possible that could be the original composition. They were used for high bearing loads. Cant tell you specifically what to do but I do not believe that a bronze sleeve of any type will work well for you. There is a lot of load put on that engine and the part you are working on is going to take the brunt of it. Good luck with the rebuild and I hope you keep posting on the project.
HMEL