084 milling saw .... er, I mean, PROJECT saw

[RiverRat2]

Retest with 7 pin rim.

0.87 inch/sec with 7 pin vs. 0.82 inch/sec with 8 pin.

Speed in cut was still only 7000 - 8000, though, and it still required a light touch to avoid bogging.

I tried leaning it out a bit more, and it sounded perfect to my ears, but there was no speed improvement.

For some reason it just doesn't want to rev in the cut. I'll try pulling the muffler screen and retesting. Can't think of any other simple fixes at the moment.

How wide a piece are you cutting?? never occurred to me to time the feet per second being made but I tached the Aggiewood butchers 084 that made about 170-175 PSi around 8200-8500 rpm in the cut on a oak slab just over 49" wide @ the first TX GTG several years back
[/IMG]http://www.arboristsite.com/attachments/chainsaw/183456d1304996974-inthacut084gtg-jpg [ATTACH]183456[/ATTACH][ATTACH]183457[/ATTACH][ATTACH]183458[/ATTACH]

Brad can You immbed these???

 

[parrisw]

How wide a piece are you cutting?? never occurred to me to time the feet per second being made but I tached the Aggiewood butchers 084 that made about 170-175 PSi around 8200-8500 rpm in the cut on a oak slab just over 49" wide @ the first TX GTG several years back
[/IMG]http://www.arboristsite.com/attachments/chainsaw/183456d1304996974-inthacut084gtg-jpg [ATTACH]183456[/ATTACH][ATTACH]183457[/ATTACH][ATTACH]183458[/ATTACH]

Brad can You immbed these???[/QUOTE]

Well, my name isn't Brad, but here ya go!

[IMG]http://www.arboristsite.com/attachments/chainsaw/183456d1304996974-inthacut084gtg-jpg

 

[RiverRat2]

Well, my name isn't Brad, but here ya go!

Thanks Will!!! that will be fine,,, How did ya catch those Prawn @ Sannich Inlet BTW???

I stand corrected on the wood size it was a smidge over 42"

 

[parrisw]

How did ya catch those Prawn @ Sannich Inlet BTW???

"

answered in other thread. Trap BTW.

 

[mtngun]

What were the stock numbers?

Stock had 133 intake duration. No mods to the exhaust or transfer timing.

RiverRat, my cant is 12 1/4 wide. It's actually easier to bog a milling saw in a narrow cut than in a wide cut, because you can apply more pressure to the kerf and make the teeth bite.

At this point I'm a little perplexed. I'll try removing the muffler screen, and see if that buys much. My only other idea is to increase the intake timing another 5 - 10 degrees -- I'd do it by porting the piston, not the jug -- but I want to rule out the simple stuff first. Maybe I'm overlooking something, or maybe it just needs more run time.

 

[Mastermind]

Stock had 133 intake duration. No mods to the exhaust or transfer timing.

At this point I'm a little perplexed.

That seems like a lot of exhaust duration stock.

I'm just waiting to see what gives. Milling has a certain interest to me. Thanks for sharing this build and the results here.

 

[mtngun]

That seems like a lot of exhaust duration stock

Yes, pretty typical for a big Stihl though. Not sure what Stihl was thinking on the stock intake timing -- perhaps deliberately low to discourage over revving ?

 

[Mastermind]

Yes, pretty typical for a big Stihl though. Not sure what Stihl was thinking on the stock intake timing -- perhaps deliberately low to discourage over revving ?

This altitude thing has me at a loss.

I'd be very apprehensive about increasing the intake duration, but then I tend to use much lower numbers than a lot of other folks use.

 

[mtngun]

I'd be very apprehensive about increasing the intake duration

Me, too. I'll save that for last, and try the easy stuff first.

Then again, I could always make a 2-piece head. That oughta perk it up.

 

[parrisw]

All the milling Ive done, I did it with a stock 394 and it worked very well. Haven't done it in a couple years though. Way too little time.

 

[Hddnis]

Me, too. I'll save that for last, and try the easy stuff first.

Then again, I could always make a 2-piece head. That oughta perk it up.

I vote you make a 2-piece head.



Mr. HE

 

[Mastermind]

This issue of low compression pressure (not ratio) has been on my mind a lot since this build and the results were posted. I have a friend who drove an old hot rod coast to coast many times. He told me at high altitude that car ran pitifully. On his first trip he changed jets to no avail, and even replaced the carb at one point.

I enjoy finding a new problem, studying it, and finding a solution. This is a good one. mtngun mentioned a two piece head, at first glance that seems like a good idea, raising the combustion pressure. Air/fuel ratio is adjustable to a point, but could the carb just flat out be too large??? Just thinking out loud here... At the altitude the saw is at the air is thinner, could that cause a smaller venturi to be more effective???

 

[mtngun]

Retesting the 084 with the muffler screen removed. 7 pin rim, 3/8 chain, 36" bar, the usual 12 1/4" wide ponderosa cants.

First up, a WP milling chain that had been converted to Granberg style, and all teeth ground 40/10/10.

Average speed 0.99 inch/sec, average RPM 9000

Next, a WP milling chain with the conventional 60/10/10 grind.

Average speed 1.02 inch/sec, average 9000 - 9500 rpm in the cut.

That finished one cant so I had to switch to a different cant for the next test. Same width, same species, and same age, but still, it's a natural product with natural variation.

A WP milling chain ground 40/0/2, the same chain used at the beginning of my 084 testing.

Average speed 1.80 inch/sec, average 9300 rpm in the cut.

Conclusion: removing the muffler screen definitely let it rev faster in the cut. The muffler screen was a bottleneck. Not sure what I'm going to do about that long term, because starting forest fires is frowned upon.

I'm still mulling over the idea of going back into the jug and increasing the intake duration from the current 155 to 160 degrees, and maybe raising the transfers a degree or two as well. It would lose power below 7000 rpm but gain power at typical cutting speeds. I'll think about that for a while.

 

[RiverRat2]

Make another small port with a husky deflector and run screens????

 

[mtngun]

Make another small port with a husky deflector and run screens????

That would work great on a felling/bucking saw, but a milling saw needs the exhaust exiting to the right side (toward the ground when mounted on an Alaskan mill).

It may be possible to put a deflector on the front cover, and point it to the right. There may be some clearance issues with the Alaskan, though. Will have to look it over carefully.

 

[parrisw]

That would work great on a felling/bucking saw, but a milling saw needs the exhaust exiting to the right side (toward the ground when mounted on an Alaskan mill).

It may be possible to put a deflector on the front cover, and point it to the right. There may be some clearance issues with the Alaskan, though. Will have to look it over carefully.

Just do the old pipe muffler mod, and point in any direction you want, and put a screen on it.

 

[mtngun]

I couldn't resist tweaking the jug a little more.

Intake duration increased from 155 to 162 degrees (279 atdc)

transfers raised to 20 degrees blowdown (they're actually tapered, 22 blowdown on the exhaust side and 18 blowdown on the intake side).

Port timing was measured with a port map, not a degree wheel. Could be a couple degrees difference, especially on the transfers, but I'm not concerned about it. I trust the port map more than the degree wheel on transfers.

Here's the cant currently used for my speed tests. The sapwood has "blued," which I think is the equivalent to spalting. The previous cut -- 1.8 inch/sec -- was 100% sapwood, which may explain why it was so fast.

Today's cut was about 50% heartwood. Soooooo..... the wood may cause more speed variation than the saw mods. :msp_confused:

1st cut -- 1.5 inch/sec (9000 - 9500 RPM)

2nd cut -- 1.5 inch/sec (9000 - 9500 RPM)

3rd cut -- 1.85 inch/sec (8800 RPM, deliberately pushing harder, and more sapwood on this stretch)

Average -- 1.62 inch/sec

I'm not going to draw any conclusions from this speed test because I don't trust this particular cant. My seat of the pants feeling was, I couldn't honestly feel a difference in power.

MOTA thinks it should have gained about 0.25 HP at 9000 rpm.

Red is today's as-built.

Blue is the previous as-built.

 

[thedave1986]

Any chance you sill have the port map photo somewhere? I'm designing a expansion chamber and that would save me a ton of time. Thanks!!!

One minor streak on the exhaust side. Rings are stuck in groove, probably due to rust and just sitting idle for years.

Minor scuffing on intake side, prolly sucked a little sawdust. Some wear high up on skirt. Bottom of skirts measured 59.91mm - 59.94mm, top of skirt 59.86mm with wear mostly on intake side. A 0.003" feeler gage will barely fit between skirt and cylinder wall.

Paint was peeling from inside crankcase. I think the seller squirted some kind of cleaner in, it may have damaged the paint. The red stuff on the counterweights is rust. Looks like the bottom end will have to come apart if for no other reason than because it is filthy ! ! ! Good call, Erick.

After wiping my finger across counterweight -- gritty rust !

Small end and big end bearings seem OK and relatively free of rust. Not sure about crank bearings

Cylinder looks great. Plating seems to go all the way to the top.

Other specs:

13 CC ZSCV
0.037" - 0.039" squish (as best I could measure thru the plug hole)
80 mm con rod length
25 mm piston deck height
47 mm piston overall height
3.4 mm (0.135") top land
7.8:1 UCCR ..... huge, huge combustion chamber

There is a typo on the port map -- height of exhaust port is actually 17.3 mm, not 11.7.

As you can see on the port map, the intake port has a partial bridge. Does anyone know what that bridge does, because there is no ring locating pin at that spot. ? ? ?

I didn't bother with a degree wheel, but now I wish I had, because these port map calculations are weird. Maybe it's just because it's late at night and I'm tired and made some goofy error, but I ran the numbers through two different timing calculators and both gave the same results.

167 degrees exhaust duration (Stihl really likes that radical exhaust timing)
133 degrees intake duration ? ? ? huh
21 degrees blowdown

I'm thinking a pop-up piston is needed to compensate for the humongous combustion chamber. Even with a pop-up, UCCR will only be about 9.5:1, which is fine for a milling saw.