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Discussion Starter #122
4sfed said:
Does anyone have one of the suspect pumps (unused) and the ability to accurately measure the O.D. of the gear?


In its present condition I'm not sure how well the gears original OD can be checked - see attached picture - but the material can be evaluated and maybe root shape. I'll follow up with APC on Monday or Tuesday.

David OD
Laguna CA
 

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I don't have a gear, but if one is sent to me I can measure it.

I have 3 very accurate measuring systems at work (1 OGP CMM and 2 Keyence IM-7030t's)
 

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Research continues, Currently need an un-chewed-up version of this PARTICULAR pump. Contact Jim Steck or myself. We know what a real OEM cast and machined gear should measure in hardness and dimension. We know the failed gear is softer and material is being sent for analysis. We don't know the actual manufacturer of the failing pump, but the over-all machine work IS superior to the other after-market pumps, made who-knows where.
 

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THANKS JIM!!!!!!!!
 

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Research continues, Currently need an un-chewed-up version of this PARTICULAR pump. Contact Jim Steck or myself. We know what a real OEM cast and machined gear should measure in hardness and dimension. We know the failed gear is softer and material is being sent for analysis. We don't know the actual manufacturer of the failing pump, but the over-all machine work IS superior to the other after-market pumps, made who-knows where.

Gordon / Jim:

PM sent. I have an unused one that I will donate to the effort.
 

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This IS GREAT! Thanks!!!
 

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I received a call from the met lab with preliminary results this morning. In addition to the difference in hardness, the alloys are completely different. The failed gear is a copper/zinc alloy with some lead, while the OEM gear has nickel in it. Final analysis is still expected tomorrow.
 

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What we suspected Jim. That's GOOD! Now when you get a non-ruined one, do what I did and compare the rest. Gears and main-shaft seem good. I didn't check spring calibration, but did a rough wire diameter, # of turns and length, which was Ok. The piston was not cut as nice as mine. Did not test surface hardening, just replaced both with mine. The only obvious goof in body machining was the double drilled relief retainer cotter-pin hole.
1636758

Radial and axial clearances were generous, but would likely be Ok with 20-50 mineral base oil.
When you get the unused pump and take it down, call me or write with your findings. We will compare for build uniformity.
Thanks Jim!
Gordon
 

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Still waiting on the report from the met lab. The composition doesn't match the common SAE alloys . . . and that's understandable since the pumps are not made in the US. I did make some basic measurements. The O.D. is the same as an Alfa pump, but the minor diameter is smaller by almost one millimeter.
 

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I received the chemistry report today. As expected, the material is very different from the alloy used by Alfa. Unfortunately no standard alloy was found that exactly matched either sample. A few similar ones are listed for comparison in last three columns of the report. The new pumps have a brass (copper / zinc) alloy versus the OEM pump that used bronze (copper / tin). In addition to tin, the OEM alloy has a significant percentage of nickel . . . which makes it heat treatable and adds strength and hardness and a small amount of phosphorus.

According to my ASM handbook (American Society for Metals), C85400 and C36000 are general purposes brasses and C91700 is a copper/tin bronze typically used for gears. In general, bronze is used for bearings due to its combination of strength and wear resistance. Below I've listed some physical properties of the "similar" alloys. It's clear the manufacturer (of the gear) substituted an easy to machine brass for a wear resistant bronze.

Yield Strength
C85400 11-15 ksi
C36000 18-45 ksi (with extreme cold work)
C91700 32 ksi (with 1.5% Ni) Phosphor is added in small percentages to increase hardness.

Machinability (also an inverse indicator of wear resistance)
C85400 80%
C36000 100% (easiest copper to machine)
C91700 20%

What's needed is a way to identify the faulty pumps before they're installed. I've noticed that the OEM pumps had aluminum plugs in the cross passage for the oil pressure bypass, and one of the "good" tall gear pumps used a sheet metal cup (similar to a freeze plug). The unused pump from Spruell and the failed pump that was the source of the failed gear had a black hex socket threaded plug. Do all of the other failed pumps have the threaded plug?

OEM and New Gear Samples Chemistry Report.jpg
 

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All the failed pumps I've seen thus far had the black Allen plug Jim. However I've seen some others where the aluminum plug had been removed and replaced with a cad plated (not black) Allen plug.
 

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I'm still looking for a "home" test for the gear itself, but don't have anything yet. However, there are several "features" that appear to be consistent on the pumps with failed gears ...
  • The holes in the screen on the pickup are larger ... 2.0 mm vs 1.25 mm
  • Star lockwashers under the four nuts
  • The cotter pin hole is double-drilled
  • Black threaded hex socket plug on the bypass port
  • The reduced diameter of the gear is fully machined
In my opinion, the last one is most telling. The OEM gears are cast. The gear that I had tested was made from a wrought alloy (bar stock). Most of the factory pumps I've seen have an area on the gear that is did not completely clean up when it was machined. A raw cast surface is proof it is not made from bar stock.

1637798


At the moment, that's the best I have. I would like feedback from anyone else that has one of the failed pumps . . . do they have all the characteristics I've listed?

-jim
 
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