going to build a pipe for my 660

[timberwolf]

Brad, you thinking all out cut off head, external transfers, big carb? That nomans land between a work saw and a racer saw is a bit tough to deal with, hard to justify a saw to do nothing but cut 3 cookies fast. On the other hand it's hard to make much of a racer if you still need the saw to answer the call when stuffed in a 3 foot oak stump.

 

[2000ssm6]

Brad, you thinking all out cut off head, external transfers, big carb? That nomans land between a work saw and a racer saw is a bit tough to deal with, hard to justify a saw to do nothing but cut 3 cookies fast. On the other hand it's hard to make much of a racer if you still need the saw to answer the call when stuffed in a 3 foot oak stump.

Just build 2, one for work, one for fun.:hmm3grin2orange:

 

[Boogieman142]

Brad, you thinking all out cut off head, external transfers, big carb? That nomans land between a work saw and a racer saw is a bit tough to deal with, hard to justify a saw to do nothing but cut 3 cookies fast. On the other hand it's hard to make much of a racer if you still need the saw to answer the call when stuffed in a 3 foot oak stump.

I agree 100% on this one. I'd like to mess with my 660 but I need it for firewood as well, its kinda frustrating at times.

 

[timberwolf]

I'd like to mess with my 660 but I need it for firewood as well, its kinda frustrating at times.

Just build 2, one for work, one for fun.

Oh, the manifestations of CAD

 

[blsnelling]

Since I built the 440 with the 460 topend, I don't really need this 460 for a work saw. Thus the reason I'm willing to make it just a GTG toy.

I'm still thinking I'd like to stick with a cylinder I can port myself and then have the pipe built. I'm well aware that there are many compromises to be made and it would be spanked by a stock appearing alky saw on muffler. But I'm not into the race scene anyway I just want a fast GTG toy. To be honest, I'm not ready to drop $1K in mods on a toy saw either. I figure I'll do what I can to port the cylinder for a pipe and stick with that for now. I could always go back later if I wanted more and all I'd lose is the pipe. I'm sure someone would pick it up.

Got any tips for port timing on a piped 460 work saw? Exhaust at 90* too much? 95* too little? Anything different on the intake and transfers than a typical woods port?

 

[timberwolf]

90 (180) is likely where you would start for a serious pipe and could go wilder yet, but would depend too on what you can do to preserve compression and where you were going fuel wise.

Transfers need much more time area, plain and simple there is more charge to move in less time. Also having lots of blow down helps, more exhaust gass to deal with and again time is reduced by the increased RPM. Thats where extra transfers help.

A good piped saw on gas can keep alky saws honest, not going to beat them if they are on their game, but if you have good chain and cutting them alkyies don't need to screw up much to be beat by a gasser.

 

[breymeyerfam]

You get the right chain and sprocket on that thing and I think you'll have a real runner. It doesn't even sound like the same saw as last night. Got any Poplar or Pine around there you can put your square chain in?

when i'm setting up for the gtg here soon, I'm going to keep my eyes peeled for some poplar or cottonwood. I have a 40+ inch cottonwood thats down we could do some racin on...:monkey:

 

[wigglesworth]

I have a 40+ inch cottonwood thats down we could do some racin on...:monkey:

That's what im talking about!!!

 

[timberwolf]

40 inch cotton wood... that would make a lot of 8x8's and 10x10's :agree2:

 

[blsnelling]

90 (180) is likely where you would start for a serious pipe and could go wilder yet, but would depend too on what you can do to preserve compression and where you were going fuel wise.

Transfers need much more time area, plain and simple there is more charge to move in less time. Also having lots of blow down helps, more exhaust gass to deal with and again time is reduced by the increased RPM. Thats where extra transfers help.

A good piped saw on gas can keep alky saws honest, not going to beat them if they are on their game, but if you have good chain and cutting them alkyies don't need to screw up much to be beat by a gasser.

I don't mind running race gas. I wouldn't limit the build on fuel requirements.

I'll go with whatever popup the piston will allow. I've yet to tear it down and measure the crown thickness. It's currently about 175 with no popup.

Raising the exhaust will increase my blowdown, but raising the transfers is going to decrease it. Let's just say I put the exhaust at 180 duration. Where am I going to time the transfers and still have sufficient blowdown? 25* sufficient, putting the transfers at 115*? I see this is one of the compromises I'll have to make. I need lots of transfer, but need blowdown time too. Extra transfers are beyond what I want to do at this point.

 

[timberwolf]

This is the problem, 25deg blowdown is pretty marginal for a high rpm saw, 30 plus would be better, but hard to get enough time area on 2 transfers and get 30 deg of blowdown and keep compression up over say 175 with conventional piston and head on.

Now, if you went alky nitro and a bigger carb you might be ok to go lower compression and keep the head on. But again were into that no-mans land, it's usless as a work saw and not going to really justify a redone intake and big carb to still be a slow racer.

I think the better bet is to build a real strong work saw and put a pipe on it, if it's going to be a piped racer then forget it being anything but and go with a cut off head and the whole bit.

 

[breymeyerfam]

40 inch cotton wood... that would make a lot of 8x8's and 10x10's :agree2:

yep, but i have no mill or 40+" bar

 

[blsnelling]

This is the problem, 25deg blowdown is pretty marginal for a high rpm saw, 30 plus would be better, but hard to get enough time area on 2 transfers and get 30 deg of blowdown and keep compression up over say 175 with conventional piston and head on.

Now, if you went alky nitro and a bigger carb you might be ok to go lower compression and keep the head on. But again were into that no-mans land, it's usless as a work saw and not going to really justify a redone intake and big carb to still be a slow racer.

I think the better bet is to build a real strong work saw and put a pipe on it, if it's going to be a piped racer then forget it being anything but and go with a cut off head and the whole bit.

Let me clarify my comment on the fuel. I don't mind running race gas, but I don't want to go with alky. I want to keep this a gas saw.

Let me see if I'm getting this straight. Correct me if I'm wrong. For a strong piped work saw, I need at least 180* exhaust duration. Anymore than that and I'll likely loose too much compression without a 2-piece head. So 90* on exhaust port timing. I'll put a popup in the piston as tall as the crown thickness will allow.

It sounds like 30* would be a good compromise on blowdown, putting the transfers at 120*. 25* would be too little. Any more than 30* would limit transfer flow too much. It'll be critical here to make the transfers as wide as possible and blend them so that they'll flow as good as possible.

We haven't talked about the intake yet. Should it be any lower than a typical woods ported muffler saw?

 

[timberwolf]

I'd have to look at the numbers to see if you would be ok compression wise at 180 exhaust, intake will need to be longer to get enough charge in given you should be cutting up closer to a real honest 12k fully loaded pulling peak HP.

I don't know if you would be able to keep transfers at 120, that pretty low considdering the maximum width limit and RPM you want to get. It's possible to put external transfers on a jug without two piece head but one major PITA. Some guys go to finger ports, but I'm not big on that idea, seen too many screw up out of round and cracked jugs as well as poor runners that are slower than a good straight forward 2 port woodsport.

 

[blsnelling]

I'd have to look at the numbers to see if you would be ok compression wise at 180 exhaust, intake will need to be longer to get enough charge in given you should be cutting up closer to a real honest 12k fully loaded pulling peak HP.

I don't know if you would be able to keep transfers at 120, that pretty low considdering the maximum width limit and RPM you want to get. It's possible to put external transfers on a jug without two piece head but one major PITA. Some guys go to finger ports, but I'm not big on that idea, seen too many screw up out of round and cracked jugs as well as poor runners that are slower than a good straight forward 2 port woodsport.

So you'd rather have more transfer at the expense of blowdown? Oh the compromises! I'll wait and see what the TW modeling software comes up with I'd like to keep this with just the internal transfers.

I appreciate the help Brian. Hopefully others will enjoy the adventure.

 

[BobL]

Once guys starts playing with piped saws, especially the big alky-nitro saws and bike saws, safety gear is a MUST. I won't even start the things without chaps on. Watch the chain in this video, it gets thrown completely out of the rails, and the chain was tight. I've fixed the problem, but I was just lucky it was staying on.

It's not just big alky-nitro saws and bike saws that have this problem. I commonly see that degree of chain lift shown in your video when I start my stock 880 on my CS mill in dry case hardened Aussie hardwood with a 60" bar using 3/8 chain. What happens is the chain heats up way quicker than the bar (even before the bar is buried) and the chain quickly expands and because it is laying on its side the expanded chain can just fall off the bar which it has done on probably half a dozen occasions. The amount of expansion observed pretty well agrees with the theoretical expansion determined by actual measured temperature differences between the chain and the bar. When you're milling you're also standing right there in front of the chain. On big logs sometimes the chain is also above your waist line. Sometimes I think a vest made from the same material as chaps could be a good investment.

This is one reason my I made my mill out of ally so it doesn't damage the chain so much when it comes off. One way to minimize this effect is to buck six inches off the starting end of the log so it's not cutting into bone dry wood and just take it easy with the start.

BTW - Nice work on the pipe.

 

[parrisw]

It's not just big alky-nitro saws and bike saws that have this problem. I commonly see that degree of chain lift shown in your video when I start my stock 880 on my CS mill in dry case hardened Aussie hardwood with a 60" bar using 3/8 chain. What happens is the chain heats up way quicker than the bar (even before the bar is buried) and the chain quickly expands and because it is laying on its side the expanded chain can just fall off the bar which it has done on probably half a dozen occasions. The amount of expansion observed pretty well agrees with the theoretical expansion determined by actual measured temperature differences between the chain and the bar. When you're milling you're also standing right there in front of the chain. On big logs sometimes the chain is also above your waist line. Sometimes I think a vest made from the same material as chaps could be a good investment.

This is one reason my I made my mill out of ally so it doesn't damage the chain so much when it comes off. One way to minimize this effect is to buck six inches off the starting end of the log so it's not cutting into bone dry wood and just take it easy with the start.

BTW - Nice work on the pipe.

Ya, I agree Bob, Even my 394 with 33" milling does that somewhat. Although I've never had a chain come off milling!