Rod alignment

[swampbuggy]

I am understanding it more the harder i strive for answers and facts, Steve i agree with your last post, it adds up. Thanks Mark H.

[elwood]

google's your friend

http://www.hotrodsproducts.com/FAQs.aspx?ItemID=66

https://www.google.com/search?q=piston+ ... 80&bih=867

[MadBill]

Umm...here's a quote from that first link: "All crankshaft guided rods require thrust washers to support the rod from excessive side play."

Damn! How did I miss those on my last rebuild? And come to think of it, how do you install washers on the journals of a one-piece crank?

[modok]

I think some engine would adapt well to piston guided rods, but not all.
Like, a subaru, audi W, or, when you have two rods between mains, it might not work out right.

[elwood]

All in favor of piston-guided rods, raise your hand..

Umm...here's a quote from that first link: "All crankshaft guided rods require thrust washers to support the rod from excessive side play."

Damn! How did I miss those on my last rebuild? And come to think of it, how do you install washers on the journals of a one-piece crank?

nothing but snark?

the big ends are reduced to cause what would normally be considered excessive side clearance and the small ends are shimmed to control rod location on the crank.

[modok]

All about the context
That site has a picture of a three piece motorcycle crank on the main page.

[LSP]

Rods will oscillate front to back during overlap, the pin end of the rod will move over more than the rod side clearance "should" allow it to in some cases.

Think about what that dynamic misalignment is doing.

[Steve.k]

Wow. Now thats alot of movement. So that is putting a lot of side load. How did you determine this?

[modok]

Crank flex can cause the rod to be pushed sideways.

I don't think they naturally do that in most engines. You see the wear on the pin, hardly ever any wider than the bushing.

[Steve.k]

Hmmm very interesting. So if your rod is off to one side of piston pin already ( which a lot are) it could create side load on piston or between the two rods. That is something i did not know for sure. Very interesting guys. Thank you.

[LSP]

Wow. Now thats alot of movement. So that is putting a lot of side load. How did you determine this?

Experimented with varied rod small end to inner pin boss clearances.

Crank flex was mentioned, yes, that plays a role as well.

[blykins]

Rods will oscillate front to back during overlap, the pin end of the rod will move over more than the rod side clearance "should" allow it to in some cases.

Think about what that dynamic misalignment is doing.

Further proof that a rod is never centered on the wrist pin.

Just because a rod is centered when the engine isn't turning doesn't mean it's going to be when the engine is running. Rod side clearance can be .020-.025" in a lot of cases. Unless it's a piston-guided rod, the rod will move around.

Going to all of this marketing length to show that a rod is mostly centered when you put the engine together doesn't mean squat.

[midnightbluS10]

Umm...here's a quote from that first link: "All crankshaft guided rods require thrust washers to support the rod from excessive side play."

Damn! How did I miss those on my last rebuild? And come to think of it, how do you install washers on the journals of a one-piece crank?

They only sell 1 piece rods for multi-piece cranks, so it's assumed that people looking at other parts there and reading the literature are using the same stuff.

[Steve.k]

Rods will oscillate front to back during overlap, the pin end of the rod will move over more than the rod side clearance "should" allow it to in some cases.

Think about what that dynamic misalignment is doing.

Further proof that a rod is never centered on the wrist pin.

Just because a rod is centered when the engine isn't turning doesn't mean it's going to be when the engine is running. Rod side clearance can be .020-.025" in a lot of cases. Unless it's a piston-guided rod, the rod will move around.

Going to all of this marketing length to show that a rod is mostly centered when you put the engine together doesn't mean squat.

Ahh yes brent its not centered when running. But you missing the point. If its already over to far more side load on piston. Thats where the hp is saved. Very interesting. Thats why the boys who tested the rods seen gains. And nascar centers them so they cannot move. Very interesting indeed.

[blykins]

No sir, you're missing the point.

The "boys" who tested the rods are from Molnar. Let's see the dyno sheet and let's see the build sheet, identifying the rod length and rod weight in each engine that was tested. Let's also see a third party builder test them.

Your "Centralign" rods will never be centered with a running engine...................................which is the whole argument that Molnar is offering up. If you want centered rods, which goes along with their argument, then you need to run piston guided rods. Otherwise the rods are going to move. Piston guided rods are centered because if they weren't, the big end of the rod would be dancing all over the rod journal.

I can show you photos of other brands of rods in my engines where the rods are centered. If I were to use a "Centralign" rod with .050" offset in those particular engines, then they wouldn't be centered anymore................

There are so many logic holes in their marketing that it's beginning to not be funny anymore.