Peining Rear Mains

[Smitty]

When peining main bearings with an air hammer, especially the rear main. Do the mains need to be supported in a peining clamp while doing this? KRW clamp works great on the block but not so much on the rear main cap. I know the front and center caps are tinned as they are forged but the rear is most often (but not always) cast which requires peining. Pein the thrust faces as well...?


Steve

[Mark in MT]

The steel front and center main caps are not peened, this would likely cause micro cracks in the bond between the Babbitt and the cap. The Babbitt poured into the cast iron parts needs to be peened as it shrinks as it cools, pulling away from the block or cap. Peening stretches it back into place so that it will be supported and have good heat transfer. I also peen the thrust surfaces to keep them tight on the ends, if you don't the peening stretches the Babbitt lengthwise in the bearing, actually loosening the bearing material on the ends. Having a support on the ends is nice if you have a good clamp, but can be done without.


Mark

[redmodelt]

This is what I have picked up; Wilson didn't make a cradle for the caps as you would have gotten pre poured uncut caps from Ford. You can tin the rear cap. There are some that even clean and tin the blocks so it can be done. You would have to machine/make a cradle if you go the peening route.

[rotorwrench]

The size of the casting of the block is the big drawback to tinning. Warpage can happen from the heat it takes to tin. The block would be a crispy critter. The rear main is cast but it's not as large and warpage won't affect it so much. Folks have their own way of cooling things after the pour too. The bearings have to be machined after pouring anyway.

The casting has to be cleaned as well as practicable. There can always still be oils in the pores of a casting if not cleaned well enough. Cast iron is porous as hell.

A lot of the old peening tools were worked with just a hammer back in the day. Different folks use different methods. It largely depends on the way they were taught or how they evolved with their experience level in learning the trade. I wouldn't poo-poo anyone's way of doing things as long as it had good consistent results.

[Kohnke Rebabbitting]

The only time you need thrust support, is if you use a babbitt tool like Wilsons, using a Hammer to hit the tool with. That process, is very ineffective. Ford used the babbitt hammer, but it was run by a air, or an electric tool, which was very effective.

I have seen about 5 Model T's, with the rear Main castings busted off, and welded, from the babbitt Hammer. I remember the last one, was a very low mileage 1914 Touring. The babbitt Guy, didn't get to babbitt that one, after he busted it.

There were 2 Model A's, one with a corner of the rear main busted off, and one that was cracked, half way around the rear thrust.

The reason that a babbitt hammer in ineffective, they are trying to cover to much area, at once. When hit, it has to be many small hits, not 5 big, hard ones.

We use a air hammer, with 40 pounds air pressure.

You should not do the Radius, even if you know where t stop, it is best to stop about 3/16's, to 1/4, from the radius, I mark with a Blue line, which, you will see.

Peen down the bottom center once, and when you come back, cover 1/2 the unpeened bearing, and 1/2 the peened bearing. When you have went from middle, to top, on both sides, do the thrust at about 35, to 45 degrees, away from the shaft babbitt, on both sides.

Just remember your only moving the babbitt up to the the cast block surface, not through it.

The cast iron cap, we put in a large vice. The rear thrust gets a round disk, just so it misses the slinger area, and should stick out of the cap about, 1/4 inch. A vice Jaw pushes against it. The front thrust on the cap, has the Jaw push against it. clamp the cap tight, and peen the shaft babbitt tight.

Then, pull the cap, and clamp the cap , rear down, and peen the babbitt thrust on the front of the cap. we then put the cap in the vice, with no round slug, and peen the rear thrust.

Thanks.

Herm.

[dansluck]

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Very informative.

[Smitty]

Thanks Herm,
Big help, I appreciate it.


Steve

[Smitty]

Herm,
I will give the air hammer method a try again, last time even though pressure was set low I was unable to remove hammer marks in the Babbitt even after machining. When doing the thrust surfaces on the cap do you put a plate between the hammer and surface or hit directly on the thrust?
Steve

[Kohnke Rebabbitting]

Originally Posted by Smitty

Herm,
I will give the air hammer method a try again, last time even though pressure was set low I was unable to remove hammer marks in the Babbitt even after machining. When doing the thrust surfaces on the cap do you put a plate between the hammer and surface or hit directly on the thrust?
Steve

Nothing between the punch, and the Babbitt.

Use a 45 degree angle, away from the bearing.

The punch for the air drill, is 1/2 inch diameter, round, a smooth, rounded end.

40 pounds pressure, and DON"T, push to hard. If you don't have enough babbitt thickness, it might be a problem. We have enough babbitt thickness to set a .050 thousandths crank.

[Kohnke Rebabbitting]

Originally Posted by Smitty

Herm,
I will give the air hammer method a try again, last time even though pressure was set low I was unable to remove hammer marks in the Babbitt even after machining. When doing the thrust surfaces on the cap do you put a plate between the hammer and surface or hit directly on the thrust?
Steve

Our thrust is also is about .150-00 thousandths to much babbitt on either end, that is needed.

Herm.

[Smitty]

Ok, I was hitting the babbitt directly. My pouring bar is machined .040 under to provide for thicker babbitt. I seem to have plenty of babbitt on the thrusts.
The punch is same size as you describe, old air tool that has been rounded off on the end.
Steve