My new +020 VH piston arrived today from Club Spares. At first sight it appears to be an exact copy of a Heplex 10503 as promised however it has a Cords type three-part oil ring and much thinner compression rings (1.14mm).
1) Unlike cast iron oil rings that have quite a bit of outward spring to maintain contact with the bore, the Cords oil ring seems to have a very small free gap and thus offers virtually zero outward pressure on the bore. Is this normal with these 3-part oil rings?
2) Is 1.14mm a standard ring height (as opposed to 1/16) and does the club intend to stock ring sets for these new pistons?
As far as I know Allan does intend stocking spare rings so the size doesn't really matter but you would have to ask him.
I have supplied and used Cords rings without any trouble, as always there are some people that do not like or trust them but you should ask them for first hand knowledge of the problem and like the people who bad mouth modern pistons the answer is inevitably "my mate down the pub said".
Roger Gwynn, Membership Secretary, curator of the Machine Register and the works drawings. Director of Draganfly Motorcycles, Craven Equipment and Supreme Motorcycles mostly retired.
The cords type oil ring is common on modern engines that I am used to and from what you mention there is nothing to be of any concern.
Be careful when installing the expander ring, on some
Pistons the orientation matters (whether the expander spells ‘w’ or ‘m’) because dependent on the location of the drillings in the piston, the expander can get caught and causes excessive oil consumption.
Rob
Rob Jameson
AOMCC Member Number 4068
1957 Ariel VH
1954 Ariel KH
1948 Ariel 4G with 1920's Ariel Sidecar/Triumph Chassis
AOMCC Twin Spares Organiser
Cords are a "dished" STEEL ring and where the number used is 3 one segment will be sealing on the outside of a ring land. If the piston has a degree of slop the sealing will run off the ring land edge and not be effective. The precise fit vertically, provides the outward sealing force and it considerable. Sometimes the excess friction will be quite noticeable in larger motors and they don't tolerate much TAPER in the bore or ring land wear. I haven't seen any " proper" cords rings for a long time. The most common oil ring these days is a three piece affair with two thin non dished chrome-steel rings with a segmented expander which has it's ends abutting to provide the outwards force. Ariel didn't use any oil rings in the singles till the bigger pump came out about 1949. ALL oil rings cause a fair bit of extra friction=s heat and power loss as well. Nev
What clearance is recommended for these club pistons?
I purchased one not so long ago , it arrived , with no info re clearance .
Thanks for any help / info
Andrew
Roger Gwynn, Membership Secretary, curator of the Machine Register and the works drawings. Director of Draganfly Motorcycles, Craven Equipment and Supreme Motorcycles mostly retired.
