The official CT Autumn GTG (07 November 2015)

[drf255]

Next idea...an easily variable flywheel...set timing with a set screw.


Engineers



Go!

How about mounting with a planetary gear, a stop, and two centrifugally activated weights to advance timing with rpm.

 

[MustangMike]

The coils already advance timing with RPM, even the non M-Tronic saws. We are just adjusting the "range".

 

[MustangMike]

www.arboristsite.com/community/attachments/curve-jpg.326453/

 

[Mastermind]

All great ideas start with some brainstorming. Y'all are all over that part.

 

[mdavlee]

Adjustable timing gear like a Bosch p7100 pump would be cool. It would add weight to keep the crank going.

 

[Paragon Builder]

What about slotted coil holes with an adjustment similar to a chain adjuster? Loosen coil screws, turn adjustment screw a bit, lock it down, test and repeat.


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[Derf]

I would be careful about cutting the cast key on the Husqvarna flywheels. The way Husky makes them is fast and cheap to cast the key into the flywheel, to properly do it would be to cut a key way in the flywheel and a key way in the crank shaft and secure them with a steel key. At the GTG someone mentioned the aluminum key built into the flywheel can sheer off and then you're screwed. I have suggested that if you ever have your flywheel off to put a punch on the backside where the key is so if it ever does sheer off you can cut a new key way where it needs to be. Without some kind of mark you really are just guessing. But at least you can buy used flywheels for cheap on eBay.

I have access to key stock at work. I make lots of key ways and keys on shafts. If I were to do an adjustable key, I'd have a 3/16" key way in the crank shaft, and a 1/16" key way in the flywheel. I'd use 3/16" steel key stock that would fit the crank keyway, and machine the top half of the key on a mill to be 1/16" wide for the flywheel keyway. I'd make a couple, one with the top half on the left side, one centered, one of the right side. I'd play with it a bit to figure out how much advancing I can get to improve performance. I don't know that I would ever mess with changing the timing once I set it to where I want it. As has been mentioned, the coil advances timing anyway (all saws, not just Stihl), the key just affects the range of auto adjustment.

 

[Homelite410]

The only time I have ever sheared a key was when I didn't torque the but tight enough.

 

[MustangMike]

My 362 had the attached key, like a husky. The key is just a guide, after the flywheel nut is tight, it does not hold anything. I filed it with a triangle file, not the best, but it worked. The timing was advanced on the 362 at the GTG.

 

[Derf]

The only time I have ever sheared a key was when I didn't torque the but tight enough.

Saying it isn't likely and than saying it has only happened to you once doesn't convince me that it's a great design. By your comment, you can see that it's possible to do, by accident or whatever. It may be that the key just acts as a guide and the friction fit of the crank shaft and flywheel locks them pretty well. Just offering up words of caution; take heed or ignore them, it's up to you.

 

[drf255]

So you guys are saying that all factory coils have automatic advance built into them?

 

[Mattyo]

Saying it isn't likely and than saying it has only happened to you once doesn't convince me that it's a great design. By your comment, you can see that it's possible to do, by accident or whatever. It may be that the key just acts as a guide and the friction fit of the crank shaft and flywheel locks them pretty well. Just offering up words of caution; take heed or ignore them, it's up to you.

I have quite a few saws in service today with 12 awg romex copper as a key...when the built-in key sheers, take a round nicholson file or dremel and grind out where the key was to make a recess. then put a piece of romex in there and voila! a key. in this case the key is simply a positioner, so it does not need to be particularly robust. copper works nice


and yes, this is of the poorer designs choice by husky imho

 

[Mattyo]

in order to make an adjustable flywheel, it seems to me that the tapered piece and the fins would need to be seperated. perhaps on a lathe... take 2 flywheels, turn one down to say 1.5" diameter so only the taper is remaining, then take another one and cut out the tapered area entirely... it becomes a circle within a circle, then add set screws ...maybe some degree markings and you're good!

 

[Mastermind]

Stihl and Dolmar both use cast in keys in many saw as well.

 

[Mattyo]

so its a uniformly bad design .... lovely

 

[Mattyo]

my 394xp uses an actual key... LOVE IT... makes life easier far as I can see.... except when that key goes flying across the room or drops on the floor...then its time to start throwing things or have a drink

 

[Mastermind]

I'm gonna say they are all looking to save a buck on a part....no surprise there. lol

 

[MustangMike]

So you guys are saying that all factory coils have automatic advance built into them?

I think all but the real old time saws have it, but there should be people more knowledgeable about it than me. ANYONE???

Randy, do you know???

 

[Mastermind]

It's more like an auto retard.

The timing is retarded at low RPM for starting. Then when RPM increases it goes to a preset timing setting. Normally 27° or so.

 

[drf255]

At what advance does power at high rpm begin to fall off?

I went an extra .005 on my 260 and picked up extra rpm.