Tangential Weight on Piston Rings 1

[PyrateODoc]

I am a quality assurance specialist who is not familiar with a new item I am checking. The item is a diesel engine piston ring which uses a compression spring on the inner diameter of the ring.

I have a drawing requirement that states, "Tangential weight when closed to 5.750 gage dia shall be 22.0/28.0 lbs". It also states that this is when ring and spring are compressed using a band type loading media having a calibrated circumferential length equal to 5.750."

Someone may have to break this down in some really small words for me, but I am trying to figure out what measuring tools and procedures I would use to measure "Tangential Weight (Load)".

The methods on the drawing states:

1. With expander installed, thoroughly lubricate ring with engine oil.
2. Apply tangential load to close ring gap.
3. Slowly release tension load until .020/.040 ring gap is achieved.
4. Read load 22.0 to 28.0 lbs

My understanding is this:
1. Squeeze the ring from the sides to make the diameter smaller until the two ends of the split in the ring touch.
2. Release the ring until the gap is .020/.040
3. The reading on the measuring device should read 22.0 to 28.0 lbs. This means that the force being exerted against a measuring device on the outer diameter of the ring should be between 22-28 lbs?

Do I understand this correctly and if so what would be the correct "measuring device" to use to measure this characteristic?

Thanks for any help in advance.

v/r

Todd

 

[ivymike]

"tangential tension" is a term used to distinguish one measurement technique from another common one called "diametral tension."

If you're drawing a free body diagram of the ring in the measurement device, the t.tension device applies force at the ring tips (at the gap) roughly tangential to the ring surface - picture a string wrapped around the circumference and tensioned. The d.tension device applies force to the sides of the ring acting normal to the surface - picture pincers squeezing the middle of the ring.

D.tension figures are typically a little more than twice the t.tension figures for the same ring, but the relationship depends on ring geometry and the young's modulus of the material.

try these guys for more info:

http://www.c-kengineering.com/files/tantenlt.pdf

 

[PyrateODoc]

Thanks, Ivymike. This makes sense because also on the drawing it states, "22.0 - 28.0 lb load (applied at 'X' and taken up at 'Y') required to close assembly to specified end clearance". I know you don't have the drawing, but "X" & "Y" are shown located at the gap of the ring on the print.

I got it now but is there a way to measure this without using the Tangential Tension Gauge you provided a link to?

Thanks for the quick response too!

 

[ivymike]

there's an SAE spec on how tangential tension should be measured - but I don't have the number handy. I believe it's included in the SAE piston ring manual (don't have a document number for that either).

http://www.amazon.com/Sae-Piston-Ri...=sr_1_4?ie=UTF8&s=books&qid=1217363776&sr=1-4

the SAE bookstore might...

http://www.sae.org/technical/standards/J1589_200806

http://www.sae.org/technical/standards/J1996_200806

http://www.sae.org/technical/standards/J1591_200806

http://www.sae.org/technical/standards/J2003_200806

 

[PyrateODoc]

Found the info in the SAE J1589. It is now also covered in ISO 6621-2. The SAE is available but has been superceeded by by the ISO. Thanks again!