7 or 8 pin
- Thread starter Ironworker
- Start date
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cus_deluxe
Commie Satan turd
I put an 8 pin rim on my 272 w a 20" bar and chisel chain and it was very grabby and tended to bog the saw down. With 7 pin rim and 20" bar its a lot more fun to cut with.
It takes a strong saw to run a 8, even a 20" bar with a sharp chain.
cus_deluxe
Commie Satan turd
Ive always heard dont even consider it with less than 85-90cc's ported or not. I like to learn for myself haha
Adirondackstihl
Flyz, Fuel & Fotos
More torque = 7
Throw the 8 in the trash
Throw the 8 in the trash
Ironworker
Addicted to ArboristSite
7 pin it is, thanks guys
Deets066
Firewood hack
I skip the 8 and go straight for the 9
I do too..........on my ported 084I skip the 8 and go straight for the 9
Deets066
Firewood hack
404-8 on the ported 088
3/8-9 on the ported 066 (20-24 bars)
3/8-9 on the ported 066 (20-24 bars)
Ironworker
Addicted to ArboristSite
There's a 9? This just got complicated. I have a ported 2188 that I run a 24", would I be better off with a 9 pin?
No way. You're pushing it with an 8, unless cutting small wood.
GPX433Todd
Small Engine Addict
Deets066
Firewood hack
If your doin any falling stick with a smaller sprocket, when I'm bucking firewood at my shop I'll try out different chain and sprocket combos
Ironworker
Addicted to ArboristSite
No falling here, I'm done doing that, firewood hack primarily, if Ironworking hasn't killed me yet, I ain't gonna let a tree do it
Deets066
Firewood hack
Madsens has big rims, but ya a couple and try em out. That Jonny might pull a 9 with a 20" bar if the rakers aren't to low
Swamp Yankee
Addicted to ArboristSite
Franny K got it.
Let's do the math.
HP= Torque X RPM / 63025 torque value in inch-pounds force, 63025 is a constant based on units or
Torque(in-lb) = HP X 63025 / RPM
A saw producing X hp at Y rpm, the torque is fixed.
For example if a saw is producing 5 hp at 9000 rpm if you plug the numbers into the equation
Torque = 5 X 63025 / 9000
= 35 inch-lb
Torque = Force X distance Force in pounds, Distance in inches (Feel free to pick your own units)
(I don't have the radius for 7 and 8 tooth sprockets, so we'll wing it. Actually I do, just to lazy to go downstairs and measure sprockets)
For a given torque, as the radius of a 7 tooth is smaller than the 8 tooth sprocket, more force is transmitted. The trade off is the circumference of the sprocket is larger on the 8 tooth so each rotation of the sprocket advances the chain a longer distance.
Circumference = 2 X π X radius
In short, you're trading force (lbs) for more inches of chain moved per revolution for a higher chain speed at a fixed rpm. This is why a saw with an 8 tooth may cut great in Eastern White but bogs in Shagbark. The force is not with the chain. (bad pun)
The long and short is an 8 or 9 tooth sprocket has a higher chain speed than a 7, but gives up force generated.
Exact same principle as a winch. Max. line pull is on bare drum, but the wire rope speed is less.
May the "Force" be with you.
Take Care
Let's do the math.
HP= Torque X RPM / 63025 torque value in inch-pounds force, 63025 is a constant based on units or
Torque(in-lb) = HP X 63025 / RPM
A saw producing X hp at Y rpm, the torque is fixed.
For example if a saw is producing 5 hp at 9000 rpm if you plug the numbers into the equation
Torque = 5 X 63025 / 9000
= 35 inch-lb
Torque = Force X distance Force in pounds, Distance in inches (Feel free to pick your own units)
(I don't have the radius for 7 and 8 tooth sprockets, so we'll wing it. Actually I do, just to lazy to go downstairs and measure sprockets)
For a given torque, as the radius of a 7 tooth is smaller than the 8 tooth sprocket, more force is transmitted. The trade off is the circumference of the sprocket is larger on the 8 tooth so each rotation of the sprocket advances the chain a longer distance.
Circumference = 2 X π X radius
In short, you're trading force (lbs) for more inches of chain moved per revolution for a higher chain speed at a fixed rpm. This is why a saw with an 8 tooth may cut great in Eastern White but bogs in Shagbark. The force is not with the chain. (bad pun)
The long and short is an 8 or 9 tooth sprocket has a higher chain speed than a 7, but gives up force generated.
Exact same principle as a winch. Max. line pull is on bare drum, but the wire rope speed is less.
May the "Force" be with you.
Take Care
GPX433Todd
Small Engine Addict
So this seems like a good place to ask this. I have an 8 pin on my 056 Super and a 25 inch bar. Is we thinking I should switch to a 7 pin for more fun 'er no?
Numa, I have tried 8s on my ported 77 cc saws, and I always end up encountering a situation where I wish I had the 7 pin on them. They can be fun in softer wood or with a lighter touch, but I like to be able to used the dogs in hardwood, and the 7 just seems better to me. With either pin, the most important thing is that the operator keeps the saw near it's optimal operating RPMs.
IMO, the 7 pin cuts just about as fast, and is just harder to slow down.
And for those who want to get real technical, you will loose a bit of power due to the additional friction of the higher chain speed with an 8, the the 7 is more efficient.
IMO, the 7 pin cuts just about as fast, and is just harder to slow down.
And for those who want to get real technical, you will loose a bit of power due to the additional friction of the higher chain speed with an 8, the the 7 is more efficient.
Deets066
Firewood hack
You would have less chain speed with a 7, I personally think an 056 with a 25" bar would benefit from an 8
