Pre Unit Triumph piston rings

[tractorman]

I am rebuilding an old Triumph engine. Fitting replacement rings, a note in the package states "fit taper ring to the second groove". My previous experience had been to fit taper rings to the top grove. So had a look in my old Triumph workshop instruction manual [no11 1945-55] and low and behold it states "5T and 6T second ring tapered, T100, T110 and TR5 top ring tapered"

I know the 5T and 6T are in a state of lower tune, cams and compression ratio but what is the reasoning behind the taper ring change of location?

[rogerwilko]

There is absolutely no logic with this statement( The manuals i mean).If the taper is on the inside of the ring then put it on the top. If it has an outer step then in would be facing down as a second  ring to act as a secondary oil scraper.Perhaps others will chime in here i hope.

[twolitre]

This link may give an insight into piston rings and many other engine parts and workings.
It mentions taper rings, but does not suggest to which ring groove they should be fitted. There does not seem to be much logic in fitting them to the top groove though.
I have always regarded stepped rings as solely ridge dodgers and that is is usually what they are called. The idea is that they will not cause a tapping noise (or break) by hitting the wear ridge in the cylinder when re-ringing used bores.
 
http://www.howautowork.com/media.html

Jim.

[rogerwilko]

I think i have my wires crossed regarding tapered rings. I was talking about an inner chamfer on the ring not the taper on edge of the ring. My mistake.I forget which way that taper faces but logically the wider to the upper side, or it would act as a pump.

[tractorman]

thanks to both Twolitre and rogerwilko, I have read-up on rings and understand the ridge dodger basis for top taper rings and help for the scraper ring for taper on the second ring. But as you have said where is Triumphs logic with the difference in taper ring location for the different models

The bore was in tolerance and I just used a glaze buster, so no real ridge at the top, in fact as I have read, a miniscule depression is actually evident where the ring changes direction from up-stroke to down-stroke. So fitted taper in second groove to assist oil scraper.

I WOULD STILL LIKE TO KNOW TRIUMPHS LOGIC, ANYBODY OUT THERE WITH AN ANSWER !!!

[tractorman]

Hi, just had a thought, What I have quoted comes from quite an old Triumph manual. If you guys have a later edition, I would be interested to know if the same comment is made or whether they have changed their stance

[twolitre]

thanks to both Twolitre and rogerwilko, I have read-up on rings and understand the ridge dodger basis for top taper rings and help for the scraper ring for taper on the second ring.

I still think you are mixing up a taper ring and ridge Dodger.
The ridge dodger is not tapered, but has a "step" on the outer edge which is fitted "step" upwards so that the effective top edge in contact with the bore is about 2 - 2.5mm lower than the top edge on the original un-stepped ring.
That way the edge of the ring cannot touch the wear ridge. It will of course,over time, make a new wear ridge.