Full Circle Cranks

[Arrowhead]

I'm wanting to start building full circle cranks. What kind of filler material/epoxy should I use? Any pics, tips, suggestions would be appreciated.

 

[Modifiedmark]

I would use that blue polystyrene insulation because its light a Gorilla is cause its strong!

 

[Team FAST]

Billett steel. 4340 bar stock in normalized heat treat condition.

 

[Scooterbum]

What about matching up a crank from these guys. Been looking at this for awhile, just never enough time.
Could be less machine work in the long run.

Full Circle Crankshaft MAZZU.. | SIP-Scootershop.com

 

[Arrowhead]

I was going to machine a solid ring to wrap around the weight. I'm not sure what to use as a filler.

 

[torence 20]

maybe a dumb question but what would the advantage of doing this be? higher rpm?

 

[Jacob J.]

Hey Ed-

I got to check out a P-62 crankcase once that a guy had made a full-circle crank for, it was pretty trick.

He used Superweld and it seemed to work fine. He said it resisted the fuel well.

 

[heimannm]

The full circle crankshaft occupies more volume in the crank case, which means as the piston goes up and down there is a greater pressure differential resulting in a bigger charge into the combustion chamber.

I believe the old McCulloch's used epoxy of some sort, try looking through McBobaust's site McCulloch Chainsaws Downunder ................. for some information.

Mark

 

[CTYank]

Boosting crankcase compression ratio, while reducing crankshaft aerodynamic drag. What's not to like? (So long as it doesn't disintegrate.)

 

[Terry Syd]

Higher crankcase compression pushes the point of maximum delivery ratio of the transfers up higher in the rev range. Both the point of max torque and max horsepower end up higher in the revs.

Here is a webpage with a graph to illustrate the concept, its down about halfway on the page -

http://twowheelers.tripod.com/TTuning.html

 

[chainsawwhisperer]

I built a full cycle crank for a 10-10. I did it only as an experament to see if it would hold together, The saw was not ported. I used hardpaper as the backing and the ring around the crank, filled the whole works with epoxy then turned the crank down to the counterweight diameter and faced it to the width of the counterweights.
Not only did it hold together, It seemed to shift the operating rpm up a bit.
Jim

 

[Terry Syd]

I read one post (can't remember where) that the mod bumped the rev range up about 400 rpm on one person's chain saw.

 

[rupedoggy]

Does the 357 Husky come from the factory with a full circle crank?

 

[ndlawrence]

Does the 357 Husky come from the factory with a full circle crank?

It comes with crank stuffers.

 

[husq2100]

It comes with crank stuffers.

So does the K960, 372XT, and I think the new K970..... Here are a couple I have to fill:

 

[husq2100]

another view:

View attachment 228130View attachment 228131

 

[husq2100]

If it is possible to "bolt in" a 372 XT crank in a 372 XP, I would love to see a side by side comparison. That would mean, say for ease, to cases set up with oilers etc, But I would say to use the same cylinder, piston , intake, carb and muffler...all to lesson the difference in production tollerances.

 

[tree monkey]

[video]http://i155.photobucket.com/albums/s294/scottk66/dadssawparts001.jpg[/video]
autobody filler marglass

 

[logging22]

How about balance? If the filler material is a different density, would that throw off the balance?

 

[gink595]

I've got a P5000 crank that was stuffed, haven't tried it out but I have a P5000 cylinder coming from Canada. The crank was done by Marcel Vincent, I will be curious to try it.