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Coupling/torque converter

Started by MakitaCS, December 11, 2008, 07:29:39 PM

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MakitaCS

I'm trying to figure out what a coupling's function is in a chainsaw.

Dolmar has 3900 rpm's for coupling speed on the 5100.

Does the coupling act like a torque converter on a tranny?

CT
CHEVYTOWN13

Rocky_J

I'm going to assume they are referring to the centrifical clutch. It's the parts on the crankshaft that ride inside the sprocket drum. 2 or 3 clutch shoes held together with springs. When the crankshaft spins, the centrifical force pushes the clutch shoes out and they engage the drum, spinning the sprocket and turning the chain. When the motor idles down, the springs pull the clutch shoes back and they disengage from the drum.

MakitaCS

A knockout as usual Rocky!

Cool beans :P
CHEVYTOWN13

MakitaCS

Would there be a performance gain/benefit from a polished crank? Maybe less wear and tear.

I'm just curious because the fella that blue printed my Chevy's L6 polished the crank
and explained that it wouldn't have as hard a time rotating through the oil in the pan
(in this case the oil/gas mixture).

CT
CHEVYTOWN13

sawguy21

Polishing the crank, were it possible, would be a waste of time in a 2 stroke. He is talking about the surfaces for babbit bearings but saws have ball bearings for mains and a needle bearing in the rod which normally is not replaceable separately.
old age and treachery will always overcome youth and enthusiasm

Brian_Rhoad

4 cycle cranks are polished because they run in oil. The counter weights on the crank will hold the oil that is running back into the pan because they have a rough cast finish. When they are polished the oil runs off quicker. 2 cycle engines don't have oil to run onto the crank. Rods and cranks are sometimes polished to remove microscopic cracks so they don't grow into a major engine catastrophie at high rpms.

Ironwood

Slightly off topic, but the latest Madsen's catalog had a good FYI on chainsaw clutches, about 4 VERY good pages worth. Sorry, the last one was fuel / oil issues, the PREVIOUS one was clutches.



              Ironwood
There is no scarcity of opportunity to make a living at what you love to do, there is only scarcity of resolve to make it happen.- Wayne Dyer

VT

Quote from: Brian_Rhoad on December 15, 2008, 09:36:24 PM
4 cycle cranks are polished because they run in oil. The counter weights on the crank will hold the oil that is running back into the pan because they have a rough cast finish. When they are polished the oil runs off quicker. 2 cycle engines don't have oil to run onto the crank. Rods and cranks are sometimes polished to remove microscopic cracks so they don't grow into a major engine catastrophie at high rpms.


Sorry, but thats not all  correct. Polished crank is the journal area that is finely touched only , same size bearings would still be used.(normal quick rebuilders practice and inexpensive)  If you were to polish the "WEB" area (counter weight) that would change the Balance as what it was meant for. 
Machined polished cranks are worked on after the balance is figured from the pistons and rods mass movement weight (huge money ) Say F1 cars etc..

Oil is used to suspend / support the bearing or keep it off of the metal of the crankshaft to the metal of the bearing. The thin film layer is needed to stop wear..
Oil in the oil pan is below the hight of the revolving crankshaft, and if it's a real fast RPM crankshaft 10 grand plus then they install drain ways to keep the excess drips away ,, then with a deep oil sump / pan or in real racing the run a dry sump.
They only do that oil return system on big dollar toys or huge ship diesels.


After a magnaflux shows any type of  microscopic cracks, then the part is junk, any cracks are not allowed. Micro or nano.

VT

MakitaCS

CHEVYTOWN13

VT

I have A LOT to learn Also , on this wood stuff.  :P

This is one of my trades, and I've been at it for years subs-ships-Helios .

http://auto.howstuffworks.com/

Remember this is old tech stuff ^^^ What i work on now is so misunderstood .

No worries VT.

MakitaCS

Cool site VT.

I was also turned on to this site. We were talking about the possibility of fuel injected chainsaws.

http://www.ski-doo.com/brphtml/skidooenginetech/en/Index.htm

Would be nice...

CHEVYTOWN13

VT

MakitaCS

Well , KISS is what most need to remember , Injection has been around for years , and it's only getting Very high tech.

Bosch ME9 system i know 2008 and later systems are way to stupid , and very costly. My saws are carb , my car is injected , but dependable , and so/so on costly, but still most have a hard time to repair it.

Kiss is Keep it simple slim


VT

MakitaCS

Rock on!

I hear you hometown. I can imagine being out in the woods and if the carb went and you had an extra carb or parts, it's all going to be cool.

Fuel injected, although would be awesome, would be tough to fix/diagnose out in the woods?

I have a crazy idea to use the module I use to tune the TBI on the L6 to see if the program will read the firings of the 2stroke on the chainsaw. I'm not sure how I'm going to do it, but it would be cool to see what the fuel delivery is, timing, what the ACTUAL rpm is for every single ignition firing(13,500, in some cases over 15,000 readings of data in one minute!). The ultimate in tuning. Not sure how much can be done with a carb though.

I will admit the L6 had more ponies when it had the Holley 390 4 barrel as compared to the 500 TBI carb it has now.

Less problems though...

¡Feliz año nuevo!

CHEVYTOWN13

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