9 replies to this topic

[Greg Locock]

So at some point I read that some hotrodders were using plain bearing in plain bearing mains or big ends. These were known as double slippers.  That is you have a conventional bearing with a very large clearance, and in the gap you stuff an extra bearing shell, giving you two low speed oil films rather than one high speed oil film. Or for the cynical, if one seized you still had a bearing.. 

 

Did I make this up?

 

If not anybody have any pictures or other information?

 

Bourke even mentioned a triple slipper.

[kikiturbo2]

something like this?  Looks like double sided bearing floating between the rod and crank:

 

https://www.motortre...8-982-404-28-1/

 

 

On a similar note, it sounds like turbocharger floating bearings...

[Magoo]

Yes, floating rod bearings. Used on production Ford flathead V8s from 1939 to 1948. Adapted to other engines by hot rodders who were familiar with them for some years after that, as shown in the article kindly shared by Kikiturbo2. 

 

A lot of bother for negligible results. 

 

On the Ford V8 the rod bearings were conjoined, one bearing for each crank throw. 

[kikiturbo2]

Speaking of rod bearings I always fondly remember a visit to a big bearing manufacturer in austria (I was working as service and application engineer for a electron microscopy company) and finding a piece of titanium rod big end that had the bearing material applied directly to titanium... no bearing shells present...  Everyone in the lab was quite proud but would not say anything further than "motorsport"..

Edited by kikiturbo2, 22 October 2024 - 13:07.

[Magoo]

I don't know why metal-sprayed bearings wouldn't be commonplace in F1-caliber stuff, maybe they are. 

 

Back when I was a tot I saw many smaller engines with die-cast aluminum connecting rods that ran directly on the crankshaft, no bearing. In back-alley garage lore they were said to be lynite (~5% Cu) but I don't know if that's true. 

 

For Model T Fords in racing there were replacement aluminum connecting rods of lynite or aluminite. The lynite rods were babbitted, which required some kind of tinning process on the rod. The aluminite rods ran without babbit or bearing and worked better, allegedly. 

[PJGD]

Ricardo were pushing slipper bearings like this back in the 1920's, particularly for aero engines.  Bristol used them for a while in the 1930's but eventually went over to conventional conventional shells for the master rod.

[GregThomas]

The designer who popularised this type of bearing for big ends was Ernest Henri in the 1920's.

His Peugeot and Ballot Grand Prix cars set the direction we still follow. Twin cams and four valves.

But his floating bush big ends were a dead end. The straight eight Ballot was limited to 3500rpm

by the design of the big ends.

Ref - The Grand Prix Car vol one By L H Pomeroy.

 

On another - motorcycle - forum this topic came up in discussion with a Royal Enfield owner/enthusiast

Royal Enfield used the floating bush big end in their 350 and 500 singles right up to the manufacturing

going to India. The guy mentioned worked at the time for HRC in Japan.

I suggested he leave a drawing of the RE bigend - and one of a turbo bearing section - on the desk of

the chief engine designer. In the hopes that the thought of a 100,000 plus RPM big end might sidetrack

the might of Honda for a week or two....

Sadly he wouldn't do it.

[Sterzo]

The designer who popularised this type of bearing for big ends was Ernest Henri in the 1920's.

His Peugeot and Ballot Grand Prix cars set the direction we still follow. Twin cams and four valves.

But his floating bush big ends were a dead end. The straight eight Ballot was limited to 3500rpm

by the design of the big ends.

As a non-engineer, I can see that the complexity would outweigh the benefit, but do we know why the slipper bearings were actually less effective than plain ones? Is it something to do with having to achieve oil flow to two gaps instead of one?

Edited by Sterzo, 10 November 2024 - 12:52.

[GregThomas]

As a non-engineer, I can see that the complexity would outweigh the benefit, but do we know why the slipper bearings were actually less effective than plain ones? Is it something to do with having to achieve oil flow to two gaps instead of one?

 

Yes. If you're feeding oil via the crankpin then the first set of surfaces gets well lubed and the outer set starves.

Which, given the relative rubbing speeds, is the wrong way round.

 

Plus actually cooling the floating bush is difficult as there is no real physical heat path available.

 

The same setup in a turbo bearing housing can be flooded with oil to carry the heat away.

 

Royal Enfield kept using it as much from habit as anything. If the oil was kept clean their low powered singles lasted as well as anything else.

[gruntguru]

I don't see cooling as a big issue - especially with lubrication feed from the shaft rather than the housing (turbos feed from the housing). Oil flowing outwards from the shaft benefits from centrifugal force.

 

Turbochargers need floating bearings to damp the oscillations arising from oil whirl - a phenomenon common to lightly loaded, high speed shafts. Big end journals do not fall into this category. The downside I see is the extra clearance (essentially double), combined with heavy oscillating load and reduced relative velocity (essentially halved).

Edited by gruntguru, 10 November 2024 - 22:02.