Using engines with odd # of cylinders for SAE mount pumps

[jfriddell]

Gang,

I work for an irrigation dealership in South Texas. About three years ago, we matched several SAE mount pumps (from a very reputable manuf.) to 3-cylinder engines (also from a well established manuf.). They ran good for about 1.5 years, then we started noticing extreme wear, worn shafts, sheared bolts, etc. on these pumps. Shop work to replace damaged parts was futile as similar damage would again occur not long after repairs were made.

Both the engine manufacturer and the pump manufacturer have pointed fingers at the other. Pump not built sturdy enough, or engine doesn't run smooth enough were the common quotes. We've had our customers run the engines both fast and slow, but the same damage seems to occur.

I'm wondering if anybody else has had similar experiences. My company has given up on the odd cylinder engines and have gone strictlty to four's as our smallest power units. We've had some limited success with driveshaft and belt driven units, but prefer the SAE arrangement for compactness and safety.

Does anybody have any other suggestions on how to make these odd cylinder engines work well with SAE pumps or is it best to avoid them?

Thanks,

Jeremiah

 

[ccfowler]

jfriddell,

When using engines (4-stroke/cycle), there is an inherent problem/feature of output torque reversals between firings for all such engines of four or fewer cylinders. For even-firing engines of six or more cylinders, the output torque fluctuates but does not reverse in steady-load operation. (Five-cylinder engines usually do not demonstrate actual torque reversals, but the fluctuations can be relatively more significant than for six-cylinder engines.) The use of a relatively large flywheel can help to protect the load (irrigation pump system), but torque reversals are still torque reversals. In reality, the pump and the engine manufacturer are probably both right.

If fewer than six cylinders are involved, I would tend to stick to using V-belt drives, torsional vibration damping couplings, and vibration absorbing mounts. I've seen plenty of cases where three-cylinder engines seem to do a very good job of "shaking themselves apart" (repeated fatigue failures of "engine parts" such as mounting brackets, short life for coolant pump bearings, etc.) unless they are very heavily built.

There is nothing inherently "wrong" with engines with fewer than six cylinders, but their "features" and "characteristics" need to be properly and thoroughly taken into account.

 

[Artisi]

I think to blame the engines or the pumps could really be overlooking what the real problem is.

You stated that the equipment ran well for 1.5 years before you started having problems.
"They ran good for about 1.5 years, then we started noticing extreme wear, worn shafts, sheared bolts, etc. on these pumps. Shop work to replace damaged parts was futile as similar damage would again occur not long after repairs were made."
So - it was 1.5 year before before the problems started which seems to indicate that every thing was Ok up until this point -- you then experienced problems and even after repairs it is only a short period between failures - this would indicate that the problem was not remedied by replacing the damaged parts.
Question:--- What has changed after 1.5 years of operation ???

Question:-- what condition are the engines in???
Are they petrol or diesel fuelled???

I would, among other things, be looking for worn engine bearings, uneven injection or timing if diesel fuelled or ignition timing if petrol fuelled, unbalanced impellers (a used / worn impeller is unlikely to be still in good balance).
Trust this gives you something else to consider in solving your problem.

 

[Artisi]

A further thought to my comments of 2nd Sept. How have you made the connection between the engine flywheel and the pump shaft.