Death in the Stihl family

[Tzed250]

Belgian, I see your point, but saying that the rod is weak does not make it weak. Stihl probably sells more 180s than some companies total production. More units in the field yields more chances at a rod being bent during maintenance.

People, especially homeowners, want lightweight saws. That weight loss has to come from somewhere. If the rods are failing in use then maybe it is a bad design. If the rods are failing during maintenance, but only some of the time, then it points to incorrect method. Some might say "Stihl should make the rod so it will never bend", and that is fine, but then the weight penalty must be fine too.

Brad is not a proffesional OPE tech, nor a mechanical engineer. It is his opinion the MS180 rod is weak until hard data is shown to back up the claim.

 

[belgian]

Belgian, I see your point, but saying that the rod is weak does not make it weak. Stihl probably sells more 180s than some companies total production. More units in the field yields more chances at a rod being bent during maintenance.

People, especially homeowners, want lightweight saws. That weight loss has to come from somewhere. If the rods are failing in use then maybe it is a bad design. If the rods are failing during maintenance, but only some of the time, then it points to incorrect method. Some might say "Stihl should make the rod so it will never bend", and that is fine, but then the weight penalty must be fine too.

Brad is not a proffesional OPE tech, nor a mechanical engineer. It is his opinion the MS180 rod is weak until hard data is shown to back up the claim.

TZ, I think your post is the answer to this whole issue, even before the Master has brought the Light. Good post.

 

[fredmc]

Belgian, I see your point, but saying that the rod is weak does not make it weak. Stihl probably sells more 180s than some companies total production. More units in the field yields more chances at a rod being bent during maintenance.

People, especially homeowners, want lightweight saws. That weight loss has to come from somewhere. If the rods are failing in use then maybe it is a bad design. If the rods are failing during maintenance, but only some of the time, then it points to incorrect method. Some might say "Stihl should make the rod so it will never bend", and that is fine, but then the weight penalty must be fine too.

Brad is not a proffesional OPE tech, nor a mechanical engineer. It is his opinion the MS180 rod is weak until hard data is shown to back up the claim.

It doesn't take an "OPE tech" to figure out something is weak. Chainsaws and other small engines are simple, not rocketry. I've seen the same kind of rod bent on poulans. $hit happens!

 

[Bowtie]

I was working on an 028 Super yesterday, cleaning it up in prep for the new piston. I noticed it has a sort of similar rod, but not exactly. I didnt measure the dimensions at this point, but I assume its larger, and of course it is not a single "beam", but splits into two beams going to the small and big ends, and is a single in the middle.

This is different from most other rods, and is an older design. Interesting.

 

[fredmc]

I was working on an 028 Super yesterday, cleaning it up in prep for the new piston. I noticed it has a sort of similar rod, but not exactly. I didnt measure the dimensions at this point, but I assume its larger, and of course it is not a single "beam", but splits into two beams going to the small and big ends, and is a single in the middle.

This is different from most other rods, and is an older design. Interesting.

I'm convinced that ALL of the manufacturers have loose tolerances and use inferior parts from time to time.

 

[2000ssm6]

I'm convinced that ALL of the manufacturers have loose tolerances and use inferior parts from time to time.

Excluded= Stihl MS180.

 

[blsnelling]

Claiming the rod is weak means you have entered the realm of the Mechanical Engineer. Please provide empirical data (tensile strength,yield points, etc.) for the MS180 rod, as well as the rods from the other saws that compete in the same market segment.

No Data=baseless claim.





.

It doesn't take a mechanical engineer to know that the flat steel rod in a 180 is weaker than the beam shaped forged rod in saws like the 3800. Also, I never said the 180 wouldn't hold up for most of its useds. Matter of fact, I said the opposite. I have never damaged a rod in any saw besides a 180. And it has nothing to do with weight savings. Other saws in this class, like the one mentioned above, are using forged rods.

 

[FATGUY]

I think Fredmc is right. You get what you tolerate. If we demanded more, we'd get more.

 

[FATGUY]

It doesn't take a mechanical engineer to know that the flat steel rod in a 180 is weaker than the beam shaped forged rod in saws like the 3800. Also, I never said the 180 wouldn't hold up for most of its useds. Matter of fact, I said the opposite. I have never damaged a rod in any saw besides a 180. And it has nothing to do with weight savings. Other saws in this class, like the one mentioned above, are using forged rods.

The weight savings for the entire saw are negligable. I think these rods were made that way as a means of a cheap power gain. (even the smallest weight savings in the reciprocating assembly produces substantial performance gains)

 

[Work Saw Collector]

I can't argue either side, but do want to say it's going to be a long week.

 

[litefoot]

Seems to me that the greatest pressure a MS 180 rod has to withstand is not in operation, but in disassembly/assembly. What is that, 20 ft/lbs of torque? Shouldn't require an I-beam for that. I'd say Stihl knows that 90% of the 180's needing a new top end will probably get tossed, so they don't expect these saws to ever get subjected to these pressures...except by the loonies here, of course.

 

[Tzed250]

The weight savings for the entire saw are negligable. I think these rods were made that way as a means of a cheap power gain. (even the smallest weight savings in the reciprocating assembly produces substantial performance gains)

This is a false statement. A change in weight of the reciprocating assembly only changes the rate of acceleration of the system, not the max power it will produce.

 

[edisto]

Some might say "Stihl should make the rod so it will never bend", and that is fine, but then the weight penalty must be fine too.

It doesn't seem that the rod design in question would be lighter than a comparable I-beam design...just less expensive.

 

[fredmc]

This is a false statement. A change in weight of the reciprocating assembly only changes the rate of acceleration of the system, not the max power it will produce.

IMO the reason they use a stamped steel rod is COST. Same reason poulans and homelites have them....COST. Forged parts cost more period. I've bent the cheap things just trying to push the piston pin out. And then lets not forget about heat, getting them hot enough to be blue has to make them softer. so on and so on....

 

[FATGUY]

This is a false statement. A change in weight of the reciprocating assembly only changes the rate of acceleration of the system, not the max power it will produce.

I stand corrected.

 

[04ultra]

Anybody ever run one with the chain brake on with the saw on high idle ???

Never seen a home owner bend a rod . Burn up a case thats a different story...



.

 

[Tzed250]

IMO the reason they use a stamped steel rod is COST. Same reason poulans and homelites have them....COST. Forged parts cost more period. I've bent the cheap things just trying to push the piston pin out. And then lets not forget about heat, getting them hot enough to be blue has to make them softer. so on and so on....

I totally agree with you. The whole saw is cheap. It is built to a price point. Stihl could spec a Pankl forged titanium rod, but I don't think the customer would want to pay the $350 difference.

If the rod does not fail in service, and does not fail during maintenance if the correct methods are used, then it is a sound design.

 

[blsnelling]

If the rod does not fail in service, and does not fail during maintenance if the correct methods are used, then it is a sound design.

I agree with you to a point. But if the competition can put a forged rod and vertically split mag case in a $250 saw, so can Stihl. My only point is that the Stihl rod is weaker than it needs to be, requiring extra care to be taken to keep from destroying the engine.

 

[fredmc]

Absolutely they are what they are. Loaner saws if you ask me.

 

[04ultra]

Why doesnt the 335/338/339 use a better design instead of the ...Clam Snelling design ????

Why does Husky use plastic lower crank cases??? Why do you see so many referb saws made by Poulan ???