New 2 Stroke Piston design

[Leafy]

So I came across a few yoututbe videos tonight about 2 stroke piston rings and it dials down to 2 concepts. 1, someone makes a piston ring that is lipped and has a piston dome which screws on to retain it so you can no longer catch a ring on too large of a port. What does that do for you? Exhaust port width can now equal cylinder diameter and no slipped rings. Whats the issue there? If you make such a port the transfer and exhaust will freeport when the wrist pin hole crosses them. Well someone else (mark atkinson) also makes pistons where the outside is full round and a wrist pin holder threads into the underside of the piston (side effect is that they end up being lighter and have better roundness at operating temperature.

So how abouts we make a piston that is basically a skirt with a female thread at the top and a dome which has the wrist pin holder. I cant seem to find the supposed patent that new zealand company has but I didnt look too hard, but even so a few of these to see if its worth anything isnt going to draw any attention. Hardest thing I can see is making a stepped ring like that, best I can come up with is find a very thick ring in the right diameter and carpet tape (or mag vise) it down in the mill to gently cut the step in it.

 

[Chainsaw Jim]

I believe they started doing that with the rings many years ago. I'm don't remember what this one came from, but I think it was an older homelite.

 

[Funky sawman]

I believe they started doing that with the rings many years ago. I'm don't remember what this one came from, but I think it was an older homelite.
View attachment 160559

I see that style of rings all the time in snowmobile engines. Also they use tapered rings

 

[Leafy]

I don't see the step that locks it into the piston so it can't fall into the exhaust port. Like the piston instead of having a rectangular profile should have an L shape.

 

[old guy]

My old Bultaco had L shaped rings, I believe they were called Dykes pattern.

 

[Chainsaw Jim]

I don't see the step that locks it into the piston so it can't fall into the exhaust port. Like the piston instead of having a rectangular profile should have an L shape.

It wasn't visible in your pics either. I looked again and noticed a higher resolution option. Now it makes a little more sense to have the screw on top, lol.

 

[Wonkydonkey]

Correct @old guy From the 2stroke tuners handbook

 

[sawnami]

Homelite used Dykes rings in Super EZ's.

Sent from my SM-N950U using Tapatalk

 

[Leafy]

No no, like this I wiped up real fast. See how the ring can't move more than like 10 thou off of the diameter of the piston so it can't pop into a really wide port and break? And see how the piston needs to split through the ring land in order to install the ring?

 

[Woodpecker]

No no, like this I wiped up real fast. See how the ring can't move more than like 10 thou off of the diameter of the piston so it can't pop into a really wide port and break? And see how the piston needs to split through the ring land in order to install the ring?

View attachment 160623 View attachment 160623 View attachment 160624

Like a reverse dykes

 

[cus_deluxe]

Idk, im just guessin that theres a reason that something from the 60’s isnt being used anymore...i would imagine that piston would have to weigh a ton. I dont understand the advantage, not to say there may not be one, but the only time youre gonna see a super wide port is on a high performance race/play type engine, and adding a heavy piston is not on the list of performance mods guys usually do. Maybe im missing the intended application.

 

[Woodpecker]

All the extra machine work/tooling this type of piston would require immediately sticks out as why this wouldn't be in a production saw. My guess is it would be too expensive for mass production.

 

[ManiacalMark]

A really wide port, in say a hot saw, it would be more logical to weld a bridge in the port seeing as it's going to be plated and probably bored over. A dykes ring may be ancient technology but it works. The 090 10 cube used a dykes ring piston.

 

[legdelimber]

Aside from the piston in the image looking to be cast iron.
This concept looks to be best suited to a low speed, long service interval industrial engine.
The skirt cut does look like it's for a reed induction, torque engine.

Was there any explanation of how the top is kept from backing off?
If you get a lot of different expansion rates, either from two different metals or just because it's a two pieces, I think the dome will loosen.
Or just the typical heat cycling of t handheld equipment would be a factor.

That's one heck of a tough spot to put a two piece item. Two piece things never transfer heat like a solid one.
Lots of people tend to shut hand held engines off with little to no cool down.
I can't imagine this thing liking lots of abrupt heat cycles.
Anyone else thinking of an eventual crack from not idling it until the piston wall/skirt is up to temp , at startup?
Or Shut it down without cool down and the skirt is in contact or lube wetted to cylinder walls, so it chills faster then the dome plug.

Now watch someone show where it's in a (step start) golf cart motor and running with no service issues. lol

 

[Leafy]

As far as I can tell both of the 2 piece piston designs were used in racing motorcycle. The linked images in the first post were for a lower class motogp bike. And Atkinson I believe road races, and his pistons seem to get way more even and less wear than 1 piece pistons.

It's not surprising no one has done this before, oems are never going to push porting this far and engine builders don't typically think on this level. And they're definitively harder to make than even forged pistons since you really need to machine the cutouts in the skirts with the two parts assembled because timing threads just doesn't work. But you can make them lighter because you've gotten rid of the thickest part of the piston and made a shorter wrist pin. It's really for hot saws it might not even be worth it without a pipe, but at least on piped 2 strokes you're going to be limited by blow down, and this piston would let you get more blow down than even a bridge port engine.

 

[cus_deluxe]

A dykes ring may be ancient technology but it works.

Not arguing that, i can see how it makes sense. I just dont see this as anything but a novelty item.

 

[flying pig]

Easily doable with modern piston tech. Look at many diesel pistons, steel crown set on an aluminum skirt. So why worry about threading it? Just use a press fit or bond it somehow like the diesel pistons are. Also for a high performance appplication when the ring is worn out you throw the whole assembly away and install a new assembly anyway. This is thinking outside the box for sure, and good on ya.

 

[Leafy]

Press fit is a great idea. I just assumed anyone here would rather turn some threads rather than turn something to within 4 tenths.

Wait you need to have the piston apart in order to install the wrist pin.

 

[EvilRoySlade]

@Leafy i know exactly what you’re talking about. I’ll look for the company info. They were a prototype design. The application was with an exhaust port that wrapped 180 degrees around the cylinder. They did it so the ring could not expand farther than desired diameter.

 

[Leafy]

I linked to the company that made the ring like this in the original post.