[SEL] Re: Pinned Rings - Problems or Not?

Curt curt at imc-group.com
Tue Apr 19 08:41:48 PDT 2005


Arnie and Bill,
After digesting what both of you have written so well, you have helped 
me answered a question I have had for a long time. That is, why did the 
engine manufactures make the ring gaps with an approx. 45° angle instead 
of butt ends? Bearing in mind what you have both written, to solve the 
strange wear pattern that a pinned ring in conjunction with a butt end 
gap would create, the solution was to make the gap on a 45°. This 
assured the ring was wiping completely around the cylinder and would not 
leave an unworn ridge down the length of the cylinder. Seems kind of 
obvious now, but until I digested both of your points I had never put 
the pieces together enough to realize that one was a function of the other.
Curt Holland
Gastonia, NC


Arnie Fero wrote:

>Hi Bill,
>
>Allow me to offer up a technical term on this line of reasoning.
>Bullshit.
>
>The problem with the two examples offered; namely a wristpin that pokes
>out and wears a groove in the cylinder wall and a stuck piston ring
>producing abnormal cylinder wall wear, is that neither one represents what
>happens with normal pinned piston rings.
>
>A normal ring makes contact uniformly with the piston wall and the oil
>film based on the amount of "spring" that the ring has.  A stuck ring
>can't move away from the wall, neither can the wristpin.
>
>My 4 hp Robertsonville (a 4-stroke engine) has pinned rings.
>Take a look at...
>http://www.oldengine.org/members/arnie/Piston_Rings/rings_1.jpg
>http://www.oldengine.org/members/arnie/Piston_Rings/rings_2.jpg
>http://www.oldengine.org/members/arnie/Piston_Rings/worn_rings.jpg
>
>As you can clearly see the rings are BADLY worn (not stuck).  The cylinder
>wall had no indications whatsoever of any abnormality caused by the "ring
>ends" even though the rings are pinned.  BTW I kept the pins when I
>replaced the rings.
>
>My two cycle Bessemer half-breed also has pinned rings, a lot of ring and
>cylinder wear and no indication whatsoever of "ring end" effects.
>
>Engine builders dropped the idea of pinned rings in 4-stroke engines for
>one reason only.  The added cost was not offset by any performance
>improvement.  Not because it caused problems.  We obviously don't see
>problems in our two-stroke engines with pinned rings.
>
>See ya,  Arnie
>
>Arnie Fero
>Pittsburgh, PA
>fero_ah at city-net.com
>
>On Fri, 15 Apr 2005 bill at antique-engines.com wrote:
>
>  
>
>>You'll wear a ridge where the ring gap is.
>>http://www.sacskyranch.com/piston_ring_rotation.htm
>>
>>One way to show rotation is to disassemble an automotive engine - and look
>>at the spot where the top ring lands in the cylinder at each TDC - if
>>there was no rotation, you should see where the ring end gap left an
>>unworn area in the cylinder, but you won't unless the rings were stuck.
>>It's worn all the way around.
>>
>>    
>>
>>>bill at antique-engines.com wrote:
>>>
>>>      
>>>
>>>>On a 4 stroker it's normal and preferred.
>>>>
>>>>        
>>>>
>>>Please elaborate. Why is ring rotation preferred as opposed to being
>>>pinned in place?
>>>Curt
>>>      
>>>
>
>_______________________________________________
>SEL mailing list
>SEL at lists.stationary-engine.com
>http://www.stationary-engine.com/mailman/listinfo/sel
>
>
>  
>




More information about the sel mailing list