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Post by MCS on May 18, 2009 8:08:01 GMT -5
It's been kind of quiet on the board as far as saw topic go so I though this might be an interesting bit of information. What brought this to mind was a tear down of a Zip. Have you ever looked closely at the large end of a connecting rod from a Homelite saw When the two pieces are bolted together, they have to match perfectly or the roller bearings will have short life. When I was in a factory training seminar years ago, we touched briefly. Some of you may not realize this but to make this a perfect fit every time the cap is bolted to the rod, the rod is cast and machined in one piece. There are four notches cast into the complete rod - two on each side. After all the machining and the boring and tapping of the rod bolt holes is complete, the cap is broken off the rod with the fracture occurring at the cast notches. Since the rod is cast iron, it breaks with a rough edge so now every time the cap is attached, all the rough spots line up and the cap goes together with a perfectly smooth inside. ;D
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Post by lesorubcheek on May 18, 2009 10:01:29 GMT -5
That's some good stuff. I knew they did it, but often pondered why there wasn't a "better" way. The method does work well. Do all saws (stihl, Husqvarna, etc) use the same method, or has anybody came up with a different machining process?
Dan
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Post by OBR on May 18, 2009 10:13:22 GMT -5
I noticed that was how it was done as well. I can see how it works, but I'm with Dan in wondering if there is a better way. The auto industry does it differently in that the caps and rods are both machined, but then again they dont use rollers either. Interesting topic....
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Post by mikem on May 18, 2009 13:30:21 GMT -5
I noticed that was how it was done as well. I can see how it works, but I'm with Dan in wondering if there is a better way. The auto industry does it differently in that the caps and rods are both machined, but then again they dont use rollers either. Interesting topic.... Are chain saws mfg w/ roller bearings due to the higher RPMs and lack of direct lubrication ? I mean indirect lubrication to mean the bearing is not in an oil bath or has oil directly splashed onto the bearing.
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Post by OBR on May 18, 2009 14:34:27 GMT -5
Thats kind of what I'm thinkin mike. Is it the same way (rollers) in the bottom end of two-smoke bikes?? I dont know I only have machines with all four strokes ;D
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Post by RBW on May 18, 2009 15:05:16 GMT -5
I think all 2 stokes have roller bearings due to their lubrication, my question is why dont 4 stokes have them. The rods are made this way to reduce manufacturing costs. Auto rods were made with cross hatching (looked like heavy knurling) that aligned the halves which were then drilled/tapped/honed for alignment. Modern rods are made of sintered metal and some manufacturers went to the controlled fracture method for alignment.
It also makes each rod unique so the caps cant get mixed up.
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Post by MCS on May 18, 2009 17:23:08 GMT -5
I noticed that was how it was done as well. I can see how it works, but I'm with Dan in wondering if there is a better way. The auto industry does it differently in that the caps and rods are both machined, but then again they dont use rollers either. Interesting topic.... A better way That Zip I just pulled apart is probably pushing 50 ;D Too bad someone ran it without a race in the clutch bearing
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Post by OBR on May 18, 2009 19:43:06 GMT -5
Maybe better way isnt the way to phrase that
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Post by lesorubcheek on May 18, 2009 20:28:45 GMT -5
Maybe better way isnt the way to phrase that Yep, that's why I put it in quotes. "Better" just somehow doesn't seem like the right word. Dan
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Post by aviatur on May 18, 2009 22:30:07 GMT -5
I had to chime in with my 2cents worth here. I am also into collecting old aircraft junk as well as restoring antique airplanes. A few years ago, I was at a auction, and bought an old German Zundapp engine that was an inverted, 4 cylinder inline engine. When I took it apart, all of the lower end was roller bearings. It has 5 main bearings, and 5 cam bearings. It's a small engine, with only 122 cubic inches, but it develops 55 h.p. This was built in 1938 in a new Zundapp factory in Nuremburg, which was later bombed out. I imagine they would be too expensive to produce today, but they sure would last forever with todays oils, etc.
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Post by OBR on May 19, 2009 15:10:07 GMT -5
Hey aviatur, how exactly does the oiling work on an inverted engine like that?
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Post by aviatur on May 19, 2009 17:32:13 GMT -5
They use a "dry sump" system, which has two or three oil pumps. The first one supplies pressure fed filtered oil to all of the needed bearings, etc. The second and in some cases the third one scavenges the oil collected in "pockets" within the crankcase and returns it to the oil tank. Inside the oil tank there is a weighted pickup, just like in a chainsaw so it will pick up oil in any position, enabling it to lubricated at all times regardless of attitude. The bigger engines use more than one scavange pump because of alot more gathering spots in the engine, such as a two row radial engine. I hope I explained it good enough. Sometimes I know what I want to say, it's just getting this darned computer to do it!
Bob
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