Ironhead connecting rod bearings

[brucstoudt]

Originally Posted by thefrenchowl

They might (just might...) fit OK on the ID and OD with a thou or two play, but will certainly crowd themselves on the PCD and won't turn freely...


Patrick

CPD? crank pin diameter?

[thefrenchowl]

Brucstoudt,

PCD is an engineering term in industry...

Pitch Circle Diameter...

Generally, refers to a diameter you can't easily measure without numerous calculations but is obvious as soon as you see a drawing of it!!!



Patrick

[brucstoudt]

copy that Patrick,thanks.

[Iron Mike]

Much like 22 O/S in place of the standard size 23 in another familiar Ironhead area.

[needspeed]

Of course connecting rod rollers and transmission mainshaft rollers both have a pitch circle, but rod rollers don't have the issue of increased running clearance when using oversize rollers like the mainshaft bearing does.

You can hone connecting rods and fit rollers to whatever clearance you want and you always use the same number of rollers as they are separated by a retainer.

Not so with the mainshaft bearing. Using the same number of oversize rollers increases the clearance unless you use one less roller.

[Rodburner]

My mistake. I did not see undersized rollers offered,the crankpin I listed the dim's for was not the pin that came out of the motor ,it was my newun.sorry for that bit of confusion.i believe the "old" pin was smaller on the OD.I am a fabricator by trade and reading mic's is taking a little getting used to.I'm getting some help from the machinists at work. I greatly appreciate all the input from everyone !!

[JB in NC]

Undersize rollers do exist. They were sold by Dixie Dist., and listed with H-D part numbers. By the way, Dixie supplied rollers to pretty much the entire aftermarket for years and years.

Now, when rebuilding rods, you need to lap or hone the races to make them round, and to remove the previous roller path. Failure to do this will result in edge-riding rollers and early failure.

I have used the undersize rollers frequently when rebuilding evo big twin rods that were "tight." That is a common problem not germane to this discussion. /he undersize rollers saved me extensive honing, and time is money.

Jim

[kitabel]

The diagram does not represent H-D crank-pins.
All H-D engine shaft rollers have cages (early big twin transmissions don't). What you showed resembles a Torrington (crowded needle) bearing (as 9057 used as an XL cam bearing) with no separators. Except for working clearance, individual needles will contact the next needle if too many are used. The total of all needle diameters must be less than the shaft OD + 50% of the roller diameter.

[thefrenchowl]

What I've shown is an illustration of a "PCD" that you can't measure directly with a vernier or micrometer...

My drawing is of a French bike crank pin/rod arrangement as found on 1930's 350cc Jonghi model TJ4.



Patrick

[Steve9]

Cool bike and build

Shifter there on the right?