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Reading a degree wheel (pics)

Stumpys Customs

Stumpys Customs

Stumpbroke
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Jan 16, 2010
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5,203
Location
south central MO
I know this has been done before, but with the search bein the way it is I though I'd start a new thread. I'll go through how I set up & read a degree wheel. The saw it's on is a Husky 576xp without the base gasket installed.

I bought a 1/2' drill chuck from Harbor freight to mount to my wheel.




Find a suitable place to mount the pointer.
 
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Stumpys Customs

Stumpys Customs

Stumpbroke
Joined
Jan 16, 2010
Messages
5,203
Location
south central MO
I use a home made piston stop made from an old plug & a bolt.





Install the stop & turn the degree wheel both ways against the stop & right down the numbers. Add those numbers together then divide by 2. example 59+63=122; 122/2= 61. set the wheel @ 61. Double check by turning the wheel the other way to the stop. you should get the same reading on each side of the stop.

 
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ptjeep

ptjeep

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Thanks for walking us through this stumpy, Step by step with pics makes things much easier to understand. On the piston stop, does it matter where in the stroke it stops or does it need to be TDC?
 
Stumpys Customs

Stumpys Customs

Stumpbroke
Joined
Jan 16, 2010
Messages
5,203
Location
south central MO
Once I git the wheel zeroed remove the stop & move on to the ex port. Turn the wheel in the same direction as the saw is running. Shine a light throught the plug hole, look fer the piston to just barely clear the top of the port. Look real close & set it to where the top of the piston is even with the top of the port. look @ the wheel & record the number. I've got 104* ATDC (after top dead center)



Now we know when the ex port opens we need to figure the duration or the amount of time the port is open during a complete revolution of the crank. Multiply the opening number by two, then subtract that number from 360 ( amount of degree's in a complete revolution). That number is the amount of time in degrees that the port is open. So 104*2=208 360-208=152. The exhuast port is open fer 152* of the each revolution.
 
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w8ye

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I made my piston stop a random length to where ILAR.

You record where the piston stops in one direction and then where it stops in the other.

Half way in between these two is TDC.

I then move the zero point where to this is supposed to be in the right place.

Then I check again and the wheel should be on the same number in each direction.
 
Stumpys Customs

Stumpys Customs

Stumpbroke
Joined
Jan 16, 2010
Messages
5,203
Location
south central MO
Thanks for walking us through this stumpy, Step by step with pics makes things much easier to understand. On the piston stop, does it matter where in the stroke it stops or does it need to be TDC?

It don't matter @ what degree it stops @ just as long as you move the pointer to where it reads the same on each side of the stop. turn the wheel all the way to the right take a reading then to the left & take the reading then use the math to find where you need to set it at. Make sure the reading is the same each way before you remove the stop. If the reading is the same then yer wheel is zeroed on the crank.
 
Stumpys Customs

Stumpys Customs

Stumpbroke
Joined
Jan 16, 2010
Messages
5,203
Location
south central MO
A quick note about my pointer, the piont on it is not in the middle. It's on the left side of the wire. No real reason just the way it is fer now.

Lets move on to the transfer ports. They can be hard to see exactly when they open up. Some you can shine a light through the plug hole & look through the ex port to see when it opens. Others you have to do the opposite. You may also have to shine the light in the plug hole & look through the plug plug hole @ the same time. Just take yer time & try different angles til you are comfortable with the reading you came up with.
Basically the same as the ex port. Turn the crank the same direction as it runs till the piston is just even with the top of the port. record yer number & use the same math to find the duration fer the trans port. I've got 115* ATDC. SO 115 X 2 =230 360-230=130* of duration.
 
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Stumpys Customs

Stumpys Customs

Stumpbroke
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Location
south central MO
On to the intake. Keep turnin the crank in the same direction. Turn it past BDC (bottom dead center) till the bottom of the piston skirt is even with the bottom of the intake port. Record the reading. Now, on my wheel it reads a full 360 degrees. I have wrote the numbers on the wheel from 0-180 on that half of the wheel. I've come up with 106 degrees ABDC (after bottom dead center). 106 X 2=212 360-212=148* duration.
]


 
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Stumpys Customs

Stumpys Customs

Stumpbroke
Joined
Jan 16, 2010
Messages
5,203
Location
south central MO
Since this is a stratto saw I'll include the pics fer the stratto ports. Keep tunin the crank till you can see the port openin up. record that reading. I've got 82*. 82 X 2=164 360-164=196* of duration.


 
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AUSSIE1

AUSSIE1

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Using a torch to determine when a port opens can yield different no's when viewed by eye only. There are different ways that all work, torch, feeler strip, eye etc. Using a torch at the opposite side to your viewing can give the indication that a port is opening earlier than if you were to use a torch from the same side as your viewing. Personally I just eye every port as it opens and use a torch from the side I'm viewing. Sure a port may start to flow a tad before this but it gives baseline no's to work from for future reference. Some use a port map to set no's and I suppose when we quote no's, we should attach our method of measurement.

:cheers:
 
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