How many inches per HP?

[gemniii]

Or Kw?

Has anyone developed a general rule of thumb for the power required to run X inches (or 2.54Xcm) of bar length, with 0.050 (why is it usually 0.050 instead of just 0.05?) and/or 0.063 SHARP ripping chain, full comp against Y inches of hardwood?

Example - my 4.7HP w/28" bar glides thru a 14" slab, bogs slightly on a 21" on red maple.
My 7HP w/28" bar glides thru an 18" on red maple haven't got a wider piece yet to see if it bogs.

Extrapolation indicates that I should expect "bogging" with my 660 if I try to cut over a 30" wide slab, and 36" will be a slow cut.
/edit - I'm about to buy a bigger bar, don't want to spend the extra $$ for a 42" if I have to get an 880 to use it.

 

[mountainlake]

Depends on how fast you cut. steve

 

[BobL]

There's no clear rule of thumb because cutting is not a constant process eg as soon as the cutters touch the wood they immediately start to go blunt. There are also a lot of other variables other than those you have listed eg Reducing the cutting angle allows even a small saw to gnaw way at a bigger log with minimal cutting - speed will be slow but it will do it. Likewise using skip chain will take the load of a smaller saw. A competent operator balances all these factors so the saw is not continually bogging down for a given task.

To answer your question you'd have to define an acceptable cutting speed for a given saw and specify the Janka hardness, fibre strength, and wood cleanliness, then optimize a chain to suit and see if the setup meets spec.

No CS is gliding through Aussie hardwoods over 40" in diameter. The operator optimizes their setup and takes what they can get and gets on with it.

All this is why we have so much to talk about in this forum, if it was entirely predictable and systematic we'd be discussing more about things like beer.

 

[SilverBox]

All this is why we have so much to talk about in this
forum, if it was entirely predictable and systematic we'd be discussing more about things like beer.

How come about 20 years ago the Fosters in the US came from Austraila in a big steel can. Now its in an aluminum can and at first it was brewed in canada, but now they brew it here in the US. It tasted better in the steel cans from Austraila.. ;(

 

[Andrew96]

I think it had more time to ferment during the boat ride. Aged fosters was better than fresh.
The water they used might have 'strange' (to us) minerals in it, I'm sure the hops were local. Either way....imported fosters is much better than domestic fosters. I like my Canadian though.

It's easier to run a high HP car down the highway than an underpowered one. No need to worry about the hills...just hit cruise and go. Severely under powered vehicles require more work (down shifting.. 4 ways on, concerns with how much stuff you take/tow). I'd say same with a saw. You learn to work with what have...more is always better.

 

[huskyhank]

snipped......

Extrapolation indicates that I should expect "bogging" with my 660 if I try to cut over a 30" wide slab, and 36" will be a slow cut.
/edit - I'm about to buy a bigger bar, don't want to spend the extra $$ for a 42" if I have to get an 880 to use it.

Go ahead and buy the bar and chains. Sounds like skip might be a good idea. And an oiler as I understand the Stihls don't have enough oiling capacity for a bar this long used for milling.

A full cut of 33-34" is what you'll have with a 42" bar. A 34" cut will be slower than the same gear on a 24" cut. The important difference is that you can make the larger cut. You can't do it at all if you don't have enough cutting width.

 

[headleyj]

Or Kw?

(why is it usually 0.050 instead of just 0.05?)

my guess here is consistency in decimal places since there's 0.063 and 0.058.

Typically the # of DP's (decimal places) indicates tolerance as well. A # with 3 DP's is going to have a tighter tolerance than a # with 2 DP's...atleast here at my place of employment and in my experience.

 

[BobL]

How come about 20 years ago the Fosters in the US came from Austraila in a big steel can. Now its in an aluminum can and at first it was brewed in canada, but now they brew it here in the US. It tasted better in the steel cans from Austraila.. ;(

Nobody in Australia with any sort of beer sense drinks fosters, well not for the last 20 years anyway. I think it is way more popular overseas than in australia.

 

[Andrew96]

Typically the # of DP's (decimal places) indicates tolerance

Bingo

 

[gemniii]

Nobody in Australia with any sort of beer sense drinks fosters, well not for the last 20 years anyway. I think it is way more popular overseas than in australia.

Since noone knows about inches per horsepower.

Fosters aluminum cans are useful

 

[mtngun]

I "need" a 120cc saw for 18" softwoods.

But I make do with what I have.

 

[discounthunter]

is the wood green or seasoned, soft or hard ,chain sharp or dull, chainsaw orange or yellow or green or red?


i do know it takes 67 licks to get to the center of a tootsie pop,give or take 52 licks.

 

[flushcut]

is the wood green or seasoned, soft or hard ,chain sharp or dull, chainsaw orange or yellow or green or red?


i do know it takes 67 licks to get to the center of a tootsie pop,give or take 52 licks.

The owl said it's three.

 

[discounthunter]

The owl said it's three.

who you going to beleive a cartoon owl or some posting on the internet? lol

 

[flushcut]

who you going to beleive a cartoon owl or some posting on the internet? lol

Well I saw it on tv it must be true.

 

[gr8scott72]

With milling, too much power is almost enough.

 

[woodsrunner]

Actually, I think this has been discussed here before. IIRC, Rail-O-Matic had a post somewhere back there in the mists of time about bar length and width of cut and hp. I don't know how accurate his info was, and I think it was presented as a general rule of thumb instead of actually data comparing various saw/bar combinations. I'll see if I can dig it up.

Scott

 

[woodsrunner]

Check out this thread and see if it answers any of your questions.

http://www.arboristsite.com/showthread.php?t=41818&highlight=rail-o-matic

Scott

 

[woodsrunner]

This is the thread I was really looking for. Check out Rail-O-Matic's post on page 2.

http://www.arboristsite.com/showthread.php?t=34747

Scott

 

[BobL]

This is the thread I was really looking for. Check out Rail-O-Matic's post on page 2.
http://www.arboristsite.com/showthread.php?t=34747
Scott

Railomatics recommendations are

67cc works best on a 24" bar with a cutting capacity of no more than 20"
80cc " " " 30" " " " " " " " 26"
96cc " " " 36" " " " " " " " 30"
111cc " " " 42" " " " " " " " 40"
125cc " " " 48" " " " " " " " 46"
140cc " " " 60" " " " " " " " 56"

But I still don't see how he can be that specific even with his ranges unless he defines an acceptable cutting speed first. My 076 (111cc) will manage a 55" cut in very hard wood - it will be slower than the 880 but it will cut it if the chain is optimized to the wood.