spacemule
The Peanut Gallery
As I understand it, it's an L shaped ring that is placed at the very top of the piston to maximize compression. Has one ever been used in a saw?
dykes ring
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hoss
Addicted to ArboristSite
Yes they were used in a couple of the non thin ringed homelite 2100's and a few other brands and models.
spacemule
The Peanut Gallery
Did they use more than one ring?
hoss
Addicted to ArboristSite
All the saws with the dykes style ring that I have seen were single ring with the ring at the top of the piston. I don't have personal experience with them, but I have heard that they are pretty long lived rings.
It's not necessarily that the dykes ring makes more compression per se', it's that they seal better after the charge has fired. They were very popular back in the days of heavy karting and two-strokes dominated karting. The thin rings had a habit of breaking if the compression was too high and conventional rings were allowing a lot of blow-by in the high compression engines running heavy mixtures like 16:1. The dykes ring take care of several of these issues.
The downside to them is that they're more expensive to manufacture and they don't last as long as conventional rings.
The downside to them is that they're more expensive to manufacture and they don't last as long as conventional rings.
hoss
Addicted to ArboristSite
The downside to them is that they're more expensive to manufacture and they don't last as long as conventional rings.[/QUOTE]
This I did not know, but am glad to now. Thanks Jacob.
This I did not know, but am glad to now. Thanks Jacob.
From what I understand, in addition to the cost of the ring, the cost of machining the piston is higher (Jacob might have included this when he discussed cost).
Basically Space, as you probably know, the seal of a conventional ring is produced by the pressure of the charge pushing the ring down on the land, creating a seal that causes pressure to push against the back of the ring.
If piston acceleration is too high, i.e., great enough to overcome the pressures holding the ring in place, the ring will lift, losing the bottom seal, which means the pressure pushing the ring against the cylinder is lost. When the pressure is gone, the inertia of the ring will cause it to strike the top of the groove, leaving no pressure at all behind the ring, and no chance for a seal. During blowby, the combustion gasses then slam the ring back down onto the land.
With an L-shaped ring in an L-shaped groove, if the ring lifts, the top of the horizontal section is borne against the top of the deep groove, maintaining a seal that allows the cylinder pressure to push the vertical part of the L against the cylinder. The seal can be maintained during flutter, but the damage to the ring and lands is pretty much the same for both ring types.
Basically Space, as you probably know, the seal of a conventional ring is produced by the pressure of the charge pushing the ring down on the land, creating a seal that causes pressure to push against the back of the ring.
If piston acceleration is too high, i.e., great enough to overcome the pressures holding the ring in place, the ring will lift, losing the bottom seal, which means the pressure pushing the ring against the cylinder is lost. When the pressure is gone, the inertia of the ring will cause it to strike the top of the groove, leaving no pressure at all behind the ring, and no chance for a seal. During blowby, the combustion gasses then slam the ring back down onto the land.
With an L-shaped ring in an L-shaped groove, if the ring lifts, the top of the horizontal section is borne against the top of the deep groove, maintaining a seal that allows the cylinder pressure to push the vertical part of the L against the cylinder. The seal can be maintained during flutter, but the damage to the ring and lands is pretty much the same for both ring types.
Winn R
Rambling Wreck
Disappointments in life --
I was hoping this thread was about something in a tongue and explicit directions for use.
I was hoping this thread was about something in a tongue and explicit directions for use.
Disappointments in life --
I was hoping this thread was about something in a tongue and explicit directions for use.
Or a gay marriage thread.
Bill G
ArboristSite King
Homelite 2100 Dykes ring
I cannot speak to there longevity nor performance as I have not ran them side by side. I can say they are a bit different. I will try to post a picture of a Homelite 2100 dykes ring piston if there is anyone that is interested
Bill
I cannot speak to there longevity nor performance as I have not ran them side by side. I can say they are a bit different. I will try to post a picture of a Homelite 2100 dykes ring piston if there is anyone that is interested
Bill
Bill-
I've always been intrigued by that design. I almost got a .095" oversize dykes rings piston for one of my 101 kart engines years ago.
Bill G
ArboristSite King
Hello JJ,
The .095 would be a very interesting piston no matter the ring design
I really have no experience with the single dykes ring. They just seem real odd and bulky but I guess they had their place.Bill
Hello JJ,
The .095 would be a very interesting piston no matter the ring design
Bill
Bill- if you have an extra dykes ring piston for 2100, I'll trade a new Mac kart piston if you ever need one. I have a lot of Mac kart pistons.
lesorubcheek
Addicted to ArboristSite
Homelite used 'em on lots of saws in the early 70's timeframe, but appearantly they were not long-lived. The smallest EZ had 'em, along with the XL-113,114, and I think it was the XL-913 and 914 that also had 'em.
There was a previous discussion about the pros and cons of Dykes rings either here or on another forum a year or two ago. A point I remember being made either from an article or a poster was they had a problem with carbon build-up. With newer synthetic oils, this probably wouldn't be a problem anymore.
Dan
There was a previous discussion about the pros and cons of Dykes rings either here or on another forum a year or two ago. A point I remember being made either from an article or a poster was they had a problem with carbon build-up. With newer synthetic oils, this probably wouldn't be a problem anymore.
Dan
We had a top fuel engine that blew apart in my school. I remember it had extremely large aluminum rods adn thick pistons but I didnt think the ring lands looked any different on the piston but the rings werent there so its hard to say
Saw Dr.
Junk Collector
I can vouch for this. My Lawn Boy mower has this style of ring. I rebuilt it last summer and there was a mess of carbon between the ring and ring "groove" in the piston. All clean with new parts now, and running 44:1 synthetic. I pulled it down to have a look through the ports after a half season of mowing, and no carbon yet on the synthetic.
sawbones
Addicted to ArboristSite
here is the one used in Wayne Suttons 10 cube 090.
I think its 72mm. I took Wayne's saw apart just to get pics of the inside
but forgot to measure the bore.
I have no info on where this piston was made.
I think its 72mm. I took Wayne's saw apart just to get pics of the inside
but forgot to measure the bore.
I have no info on where this piston was made.
