Triple gear pins OK?

[Steve Jelf]

In my 1923 touring a triple gear bushing seized and spun the pin, which wallowed out the hole enough to make the pin and the gear wobble. So I'm using a "new" flywheel.

This morning I blasted the pins clean and measured them. They're mostly a perfect .675" but near the outer end they have from .001 to .0015" of wear. The transmission book says up to .005" wear is OK, but how about when it's not uniform over the length of the pin? Are these OK to use?

[speedytinc]

In my 1923 touring a triple gear bushing seized and spun the pin, which wallowed out the hole enough to make the pin and the gear wobble. So I'm using a "new" flywheel.


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This morning I blasted the pins clean and measured them. They're mostly a perfect .675" but near the outer end they have from .001 to .0015" of wear. The transmission book says up to .005" wear is OK, but how about when it's not uniform over the length of the pin? Are these OK to use?

Pins wear on the load side. Turn them around 180 degrees. Surface is unused. Added benefit, extra clearance for oil to get in.

[Dan Hatch]

If you blasted them the surface is now too rough to use for a bushing. They need to be smooth as glass.
The ones sold by most vendors will not work as delivered, must be polished. If not polished they will eat a bushing out or lock it up. Read Herm’s thread about building transmission.
Dan Mceachern pins are best. This is just one mans opinion, what’s the saying “Your mileage may vary “. Dan

[John kuehn]

I think the triple gear pins ought to be really slick and have a polished finish. I wondered about that when I saw the blasted finish on the pins. A blasted finish would cause the bushing finish to start wearing since it’s a softer material. The wear on them isn’t enough to worry about in my opinion.
When they are worn very little I would ream the bushings to fit the pins and be done with it.

[Dan Hatch]

One more thing, if you knock them out, will not be tight when you put them back in.
Replacement pins should be larger than original pins where they fit flywheel.

[speedytinc]

Oops. I missed that you blasted them. Sand? they are no good now. Light bead blast? May be able to lathe polish them, but they would have to press back in tight. Not worth the risk. Get some new pins.
Use a PRESS to remove & install them. You certainly know to press them out from the gear side, not push them thru. Install bolts into the 4 closest pins threaded holes to prevent a crack from the pin hole to the bolt hole.

[Scott_Conger]

Being that this is a plain bearing, a 32Ra finish would be fine and pretty much preferable. This surface finish will hold micro-reservoirs of oil once supplied by the spiral groove in the bushing

The very longest life plain bearing would have a 16-20 Ra finish (closer to polished). This is in theory and not sure it is applicable in this particular setting.

Understand that surface finish is a science and you can have a polished surface which is rougher than you'd think on surface finish scales. Surface finish is a function of RMS peaks/valleys plus wave form. Selecting different cutoffs for the measuring equipment will give different results, so there are standards applied to control the length of cutoff for different applications. In the world of surface finishes, a polished surface may not necessarily be the smoothest...it all depends on the method used to accomplish the finish and the number, type and size of occlusions left after polishing.

A sandblasted finish in no way resembles a finish that you'd want to use. That said, given that the dimension is (I assume without consulting a drawing) nearly at standard size, then it might be possible to apply a finish to the pin which would bring it down from the rough finish it is now, at the expense of some diameter. However, removing the pins from a cast iron hole and replacing them is an entirely different story with it's own pitfalls, unrelated to surface finish and the scope of the question posed.

[Dan Hatch]

Another note about pins. Dan’s pins have the shoulder that Ford pins do. They are the only reproduction pins that do that I know of. This keeps the pins from coming out the gear side of the flywheel. I have not seen this, but have heard of it happening.