Pouring the main bearings on the 5HP Alamo

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The old bearings were melted out as they were worn low.

A precision tool was made to locate the bearings on center, both vertically and horizontally. The discs are a thou clearance to the bore and will slip in each end of the cylinder.

Here the centering fixture is in place in the bore. The small screws are just to give you something to hold on to, to position the discs in the bore.

And a view from the other end.

Here you can see how the fixture will hold the dummy shaft that the babbitt will be poured around.

Dummy shaft in place.

This bar accurately locates the dummy shaft the correct distance from the cam gear. Actually I added .010 to the standard diametral spacing to account for future wear in the bearings for years to come.

The end caps and collars have been added. The end caps (along with the spacer shims) will determine the total bearing width. The sliding collars will be moved up against the frame and will form the outside of the bearing that is outboard of the saddle. These will be sealed with Babbitte Rite.

Here is a close-up of how the end cap and collar will work.

Here the spacer shims have been added. They are the same width as the mains on the crankshaft are wide. The notches on the end allow the sliding collars to slide up tight to the frame saddles.

A close-up of the shims. It's pouring time!


The upper caps were poured first.

Here the offside upper cap is being readied for pouring. The Babbitt Rite is in place and preheating has begun. Last week on the list was a discussion of cooler temperatures for the engine parts so I decided to try this. Using an IR gun the cap was 230-250 F when the babbitt was poured in.

Hmmm, this didn't work too well! The cooler temps might have worked had I used a larger ladle, but it was all I had. These bearings are 7+ pounds each and it takes 6 or 7 ladles to fill one. So this was melted out and we start over.

This time the cap was heated to over 500 F and the result was much improved. This is immediately after removal with no cleanup.

The onside cap was done the same way.

Preheat the shaft and end caps.

Preheat the cap.

Quickly bolt the cap in place, install the Babbitt Rite, final heat to 550 F, and pour the babbitt. Note the old greaser lower half. The was heated extra hot and serves as a riser to keep feeding metal as the babbitt solidifies. Note the babbitt coming out the vents at the upper corners of the bearing. Proof that the bearing is filled.


Now its time to do the lowers:

The same shims that were used to seal the uppers from the lowers were reused to pour the lowers. But note the slot cut in the upper shims, into which the babbitt will be poured. The shaft, underside of the shims, endcaps, and collars were sooted. Notice the soot has been cleared away around the slot. Here pieces of Babbitt Rite will be stuck after preheating to create both a funnel and a riser.

Here preheating of the saddles and everything that will have babbitt poured against it begins. The target is 550 F. In the background the babbitt pot roars bringing the metal up to proper temperature.

The babbitt is hot enough as a wooden stick chars and ignites when dipped. I'm pouring the off side bearing.

The onside is up to proper temperature and the Babbitt Rite funnel/riser has been stuck in place. Notice the one on the offside failed and spilled babbitt :-(

Pouring the babbitt in the onside bearing. A bigger laddle would help!

This is how the funnel/riser was supposed to work. No leaks!

All the pouring fixture has been removed and the risers filed flush with the cap bed. I'm real pleased with how these turned out. Yes, it is a lot of work to make the special fixtures to pour the bearings. But this makes for easy scraping and fitting of the crankshaft!


This makes for a leisurely Sunday's work after yesterday's intense pace. Here the crankshaft is being fitted and the bearings scraped as necessary to give good fit. Actually the only scraping required was on the outside edge on each side. A radius was cut on the inside edge and the crankshaft fit right in with only a couple of hours of work.

Here is a close-up of the off side bearing. You can just barely see the 45 chamfer cut in the upper edge. This builds the pressure wedge for the lubricant film. The chamfer stops about 1/2" from each end. It's not done on the lower side as the crankshaft doesn't turn that direction.

Permanent shims will have to be cut for the caps, but other than that these bearings are done. Whew, this is a great ending to a great weekend!

The flywheels spin effortlessly :-)

That's all folks!