Paragon Builder
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?????
Ok, that sounds like you might want to increase from stock?
How do you figure out that fine balance?
Reducing Squish on a Poulan Clamshell
- Thread starter Chris-PA
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Ok, that sounds like you might want to increase from stock?
How do you figure out that fine balance?
Chris-PA
Where the Wild Things Are
I have read that, but I'm not sure what the mechanism for it would be. The only thing I can think of would be in the mechanical resistance as the case build pressure - but you can control that by reducing the case compression angle. Hey, it's an experiment!
Well, I haven't got one! Actually, this has mostly been playing around to stave off cabin fever, but as it turns out it's been surprisingly easy. Enough so that playing around with fitting other pistons seems like it would be a hassle.
Hedgerow
HACK
There is a case volume/displacement ratio, but that one is above my pay grade... Successful platforms have been built on both extremes though..
Chris' platform/case volume, is rather tight already, so it will be interesting to see what the stuffers do to the useful operating rpms..
Paragon Builder
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Ok great! I'm absorbing as much of this as I can.
drf255
BAD CAD
Great Job Chris.
Paragon Builder
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Love your avatar!
LegDeLimber
Addicted to ArboristSite
Any chance of carving out a step in the flat face of the pan, where the radius meets the corner?
I'm thinking of a having a tab on the end of that insert and the tab being captive between the pan and the cylinder base, when they're assembled.
Of course that would mean a redrawn & printed insert.
If the insert rolls up while the motor's at full throttle, I'm kinda envisioning a
"How to straiten your Clam-Crank" project.
Not wishing bad weather on anyone, but these cabin fever, Marbruary projects
that come out of it, are some interesting/entertaining reading.
I'm thinking of a having a tab on the end of that insert and the tab being captive between the pan and the cylinder base, when they're assembled.
Of course that would mean a redrawn & printed insert.
If the insert rolls up while the motor's at full throttle, I'm kinda envisioning a
"How to straiten your Clam-Crank" project.
Not wishing bad weather on anyone, but these cabin fever, Marbruary projects
that come out of it, are some interesting/entertaining reading.
mp5n
ArboristSite Operative
Chris,
What was the squish before you started? On another note I want your calculator! Is it a 11C or 15C?
What was the squish before you started? On another note I want your calculator! Is it a 11C or 15C?
drf255
BAD CAD
Why not just buy a real saw?
Hedgerow
HACK
At this point, it's not about the destination...
It's about the journey..
It's about the journey..
Chris-PA
Where the Wild Things Are
Good thinking - I tried to do something similar, in that there is a 1mm radius on the edge of the cap, and the same on the edge of the cylinder. I originally drew it with a bump there to try to lock in to that seam, but the printer prints with a 0.35mm string and it just wasn't giving good enough detail on a geometry that small. Then too, with the PETG material and the thin wall that piece is not stiff enough to lock in well anyway. So I'm just going to JB Weld it in - there is no force on it other than vibration.
It was 0.040". That seems to be pretty typical for this series of Poulan.
It's an 11C and you can't have it! I've had it since college - I was staggered at what they go for on eBay. I have an app for it on my iPhone.
Seriously? Why does it bother you? It's a cheap 20 year old saw that will already embarrass many more expensive saws, what's not real about it?
Exactly, thank you for getting it!
Hedgerow
HACK
I am sure I have seen them somewhere else before, but what did the transfers look like on that model?
LegDeLimber
Addicted to ArboristSite
Need the fluid and gas engineers to weigh in with some jargon here!
Tight as you're swinging the crankweights to the insert, at 9 thou or so,
There's going to be a pretty surprising amount of drag against the inserts, imposed by craknweights.
I expect there a strong pressure wave just infront and between the weights and insert
and Then a negative one, just behind them, as things are spinning.
lots of dynamic load changing will be happening, IF and I say IF i'm thinking correctly.
Tight as you're swinging the crankweights to the insert, at 9 thou or so,
There's going to be a pretty surprising amount of drag against the inserts, imposed by craknweights.
I expect there a strong pressure wave just infront and between the weights and insert
and Then a negative one, just behind them, as things are spinning.
lots of dynamic load changing will be happening, IF and I say IF i'm thinking correctly.
Chris-PA
Where the Wild Things Are
This is an earlier one I did, but transfers are the same:
They did change the shape in later years.
There should be 0.018" to 0.020" clearance to the filler.
I think there should be a pressure wave in front of the big, flat counterweights of this saw, which was the subject of this thread: http://www.arboristsite.com/community/threads/clamshells-transfer-shape.232407/page-2#post-5194065
It is a secondary reason I'm filling in that gap at the bottom of the engine, to help build pressure before the transfers open. Of course I cannot get rid of the big slot in the middle where the rod goes - though I have tried to figure out what I could do there too!
tree monkey
Addicted to ArboristSite
1.2 to 1
Chris-PA
Where the Wild Things Are
Well, I'm a total idiot - I blew it! See the nice bevel on the counterweights - and the total lack of a bevel on the boss on the other end:
I was test fitting prior to gluing them in, and of course it isn't going to work - not without bevelling the boss. A matching bevel won't quite get into the pin hole, and it's pretty wide, so I'm considering it. I have no way to know how much it will weaken the crank or how much margin it has. Then again it's an old cheap engine.
I was test fitting prior to gluing them in, and of course it isn't going to work - not without bevelling the boss. A matching bevel won't quite get into the pin hole, and it's pretty wide, so I'm considering it. I have no way to know how much it will weaken the crank or how much margin it has. Then again it's an old cheap engine.
LegDeLimber
Addicted to ArboristSite
What, maybe 3/4 of the way, or better, to the pin?
Just remember to cut it in the lathe and don't file or sand it axially.
Don't want the really badly oriented stress lines that would create.
Just remember to cut it in the lathe and don't file or sand it axially.
Don't want the really badly oriented stress lines that would create.
