Building an 84" Chainsaw Mill

[Yeastbeast]

G'day everyone,

as per the title, I need to get myself sorted for some big trunks. I have several to do in the 5-6' diameter range.

So far, I'm thinking an 84" bar would be the go (I believe that is the biggest available?)

I can manhandle the mill that I made, my 880 and 56" bar, but that is about the limit my back can handle I think. Given this is the case, I was thinking it might be best to accept that these logs are few and far between, and are going to be a two person job. Therefore, I was thinking a double ended bar would be the best bet, and run my 660 on the other end.

I'm also thinking sag might become a major issue over such a length, and I'll probably need to do something to correct that. I've read somewhere that a rare earth magnet over the center of the bar can counteract the sag.

If anyone can add some useful input/advice that would be great.

No reference for size in the photos sorry, but there's a couple of them...big bastards

 

[mdavlee]

Check with Madsens. They may have a double ended 84"

 

[Grande Dog]

Howdy,
I think you'll be way ahead by buying from GB http://www.gbforestry.com.au/store/chainsaw-products/chainsaw-bars/double-ended-bars-404 The dimensional weight of shipping a long bar would make the cost too extreme. Not knocking the brand, but that pile of that wood is a tall order for any saw.
Regards
Gregg

 

[Iron.and.bark]

Firstly the 2 saws have to run in sync, so an 880 and 660 would not run well together.

My 3120xp Runs a 72 and I can cut around 5 & 1/2 foot wide slabs. I use a modified Alaskan mk3 mill. Unlike bobl I don't use Sign rail (HD strutt). I use a aluminum solar panel mounting strutt (sorry can't find it in capral PDF I have). Vastly better feel, it is larger, thus provides larger log contact area and also balances the power head better. Will post a pic later today.

I will let bobl link his great magnet thread.

Otherwise perhaps consider the westfords mill system that another w.a. member has on here.

Oh and if you want a GB bar can prob get you a good deal

 

[Yeastbeast]

I was most likely going to get a GB. I bought a 56" off Laurie a couple of months back. I see they make a 87" double ender

Is the main advantage of the sign/solar strut that they are lighter? I was probably just going to use galv RHS like the other mill I made.

I was also reading somewhere that the powerheads didn't need to be alike? I thought an analogy may be pulling a bogged tractor out with two tractors linked with a chain. Both tractors contribute what they can, even though they aren't necessarily synchronized.

Do you have any sagging issues with the 72" bar?

 

[MGoodwin]

I have run my double end bar (60"with two 066's) with great success on about 48" maple.

I dont know where this idea came from that the saws need to be synced. When you are in the cut, they are each seeing a load. One saw is not impacted by the fact theres another motor pulling. Your prime RPM for an 088 might be different than an 066, but I would bet this delta is negligible. Thought I had a post earlier with the setup.

 

[skinnyd]

660 and 880 bar studs dont match either. you'll be better with 2 880s.

 

[Skeans]

Check with Madsens. They may have a double ended 84"

Madsen's use to stock 96" stihl and Husky bar, but you better be a good sized guy to use one. My 60" on my 395 is a bear to handle in the woods.

Sent from my SAMSUNG-SM-G890A using Tapatalk

 

[scheffa]

I run a 84" GB bar with an 880 and it does it no worries, sags a touch but nothin to bad. What's species are the logs

 

[scheffa]

Also the rails for our long mill are just 30x30 shs, I can run the mill on my own no worries

 

[Yeastbeast]

I run a 84" GB bar with an 880 and it does it no worries, sags a touch but nothin to bad. What's species are the logs

Also the rails for our long mill are just 30x30 shs, I can run the mill on my own no worries

They're redgums. You might be stronger than me, I could probably do it but I reckon I'd really be pushing it.

 

[Iron.and.bark]

I was most likely going to get a GB. I bought a 56" off Laurie a couple of months back. I see they make a 87" double ender

Is the main advantage of the sign/solar strut that they are lighter? I was probably just going to use galv RHS like the other mill I made.

I was also reading somewhere that the powerheads didn't need to be alike? I thought an analogy may be pulling a bogged tractor out with two tractors linked with a chain. Both tractors contribute what they can, even though they aren't necessarily synchronized.

Do you have any sagging issues with the 72" bar?

Here are the rails in the mills frame construction I use vs granberg ones. (Sorry wasn't reffering to how was mounted on the log) Being an extruded ally molding with an integrated locking system my whole rigidity has gone up and I get a better quality cut.

I have very little in the way of bar sag issues, but considering any larger slab should be milled at least 2.5" thick preferably 3" not a huge issue to me. There was a guy down here with a very large band saw mill and he unfortunately cut a lot of big timber to 2" cupping ment a lot of these had to be brought down to under 2m in length.

As for the 2 tractors pulling, it is more like 2 tractors jointly running a harvester off the pto shaft.

 

[Iron.and.bark]

I have run my double end bar (60"with two 066's) with great success on about 48" maple.

I dont know where this idea came from that the saws need to be synced. When you are in the cut, they are each seeing a load. One saw is not impacted by the fact theres another motor pulling. Your prime RPM for an 088 might be different than an 066, but I would bet this delta is negligible. Thought I had a post earlier with the setup.

Page 170 in mallofs exceptional book.

Though I agree on similar saws working fine together.

 

[scheffa]

Should be fine running one saw in redgum, that and yellow box are what I cut mainly and with 1750mm cut width I haven't had a problem as yet

 

[BobL]

Firstly the 2 saws have to run in sync, so an 880 and 660 would not run well together.

Nope, the saws do not have to be especially set up to run in synch - put any two saws together and provided they are able to get to the same rpm they WILL run in sync.
It's because they are connected by a chain it's like two pistons on the same crank so even if one piston is smaller it WILL still run in sync.
One piston might only be producing 6 HP and the other producing 8.5 HP but the total power will be 14.6HP

You may want to look at the HD Highway road sign railing material from Capral.
When I bought in about 5 years ago a 20t length cost about AUS$100 but I think it might be cheaper now.
Here it is alongside the GB rail.
.

 

[Iron.and.bark]

Nope, the saws do not have to be especially set up to run in synch - put any two saws together and provided they are able to get to the same rpm they WILL run in sync.
It's because they are connected by a chain it's like two pistons on the same crank so even if one piston is smaller it WILL still run in sync.
One piston might only be producing 6 HP and the other producing 8.5 HP but the total power will be 14.6HP

You may want to look at the HD Highway road sign railing material from Capral.
When I bought in about 5 years ago a 20t length cost about AUS$100 but I think it might be cheaper now.
Here it is alongside the GB rail.
.View attachment 457525

Sync - I used that word as it seems to be the "vogue" word used when describing running to saws in parrarell

Your first statement illustrates a fundamental of what I am stating. Eg my home lite c-9 running at 7000 rpm will not be happy with a 3120 doing 12000.

Also my solo 603 will do 12000rpm in conjunction with my 3120 but will self destruct in relatively short order.

Also if you look at machinery driven by tractor power takeoffs there is quite a lot of chain

As for HD strutt, in my first post in this thread I already stated I had compared it as well. Just personal pref, but I believe it is superior.

 

[Yeastbeast]

Sync - I used that word as it seems to be the "vogue" word used when describing running to saws in parrarell

Your first statement illustrates a fundamental of what I am stating. Eg my home lite c-9 running at 7000 rpm will not be happy with a 3120 doing 12000.

Also my solo 603 will do 12000rpm in conjunction with my 3120 but will self destruct in relatively short order.

Also if you look at machinery driven by tractor power takeoffs there is quite a lot of chain

As for HD strutt, in my first post in this thread I already stated I had compared it as well. Just personal pref, but I believe it is superior.

I get the point you're making, my thoughts would be run the 880 at 11,000 rpm (factory max) and also run the 660 at 11,000 (it's tuned to 12,500 at present). That way the 660 is just giving it a bit of help.

 

[BobL]

Your first statement illustrates a fundamental of what I am stating. Eg my home lite c-9 running at 7000 rpm will not be happy with a 3120 doing 12000.

Also my solo 603 will do 12000rpm in conjunction with my 3120 but will self destruct in relatively short order. .

I don't recall you mentioning either of those combinations - what you mentioned was and 880 and a 660, both relatively high revving saws with peak torque at about the same rpm (more about that later).

my thoughts would be run the 880 at 11,000 rpm (factory max) and also run the 660 at 11,000 (it's tuned to 12,500 at present).

The WOT rpms are largely irrelevant because at max rpm saws have little power and even less torque - it's what the two saws do under a back torque (cutting load) that matters. This can quite variable. Unless 4" diameter wood is being cut, for a 12000 max rpm saw it's not 12000 rpm, but anywhere from 7000 to 10000 rpm. So provided both saws can run in their cutting range they do not need to be identical to contribute to cutting.

Under serious loads the max cutting speed seems to occur when the chain is optimised for a cutting at RPM in between the max torque and max HP. On something like a 660 this is between 6500 (max torque) and 9500 rpm (max HP) which is where this saw normally operates best when milling.

I mention the point about chain optimisation because very few people even bother with this. To exaggerate this point the rakers can be set to 0.005"' so a 12000 max RPM saw might run at 11,900 rpm but very little wood is cut. Likewise the rakers can be dropped so much that the saw rpm drop below the max torque and the saw then bogs down.

Ideally the saws should have the same relative torque curve shape, so they deliver their max torques at the same RPMs. Then it doesn't matter if its a 50 cc saw paired with a 120 cc saw.

The max torques for 050 (7000 rpm), 075(7000 rpm), 076(7000 rpm), 880(6000 rpm), and 660(6500 rpm) are all within 1000 RPM of each other so all these saws would work fine together. With the 660 and 880 the full HP of each saw would bot be realised because they don't have an identical torque curves and their max HPs are not delivered at the same RPMs but they would still work fine together.

Tuning is another story.

 

[scheffa]

To not have any of the possible problems mentione above why not just run a standard 84" bar like I do with one power head and a sharp chain?? Works for me, half the fuel, half the oil, half the noise

 

[sawfun]

I know a guy who had to have a custom 10' bar made by Chain Bar Repair, so he could mill a giant oak. He uses double ended 090g's. I sold him the Stihls with a 36, 56, & 66 inch milling setup. He uses a magnet to help with the bar sag until the bar is in the wood.