Saturday, September 3, 2011

Piston vs. Gas Turbine Engines: Reliability and Maintenance

Reliability:  In my recent searching through a number of aircraft engine related web sites, I came across numerous comments to the effect that gas turbines were more reliable in operation and went longer between routine scheduled maintenance cycles than piston engines.  I have no background in this area, so I only have this anecdotal information to go on.  But it does make sense, since a gas turbine has only one main moving part versus the dozens found in a piston engine.  Also, a gas turbine runs in a continuous smooth manner versus the intense internal pounding that a piston engine is subject to. 

Maintenance:  Any service and maintenance requirements for a 'bot's power source will be inherited from those same requirements for the harvester/tender as a whole.  So with this in mind... 

It would be a violation of the WID Rule  having to add an additional workforce to service the special repair/maintenance needs of a team of robots when there are already farm machinery mechanics on the payroll.

WID Rule, Corollary 2: Regarding operation, service and maintenance, K.I.S.S., since the workforce that will be responsible for these jobs in the future will be the same people that now operate, service and maintain the existing farm equipment.

First, the most likely place for a robot harvester/tender to break down will be out working in the middle of a field.  For this reason, field repairability is a must.  The way to meet this design constraint is to break a 'bot's design into modules that can be easily swapped in/out in the field by someone with a few hand tools and minimal experience.

Second, a field supervisor has enough to worry about already, making sure the crop is picked, packed and moved out of the field on time  The added responsibility of dealing with daily 'bot break-downs is not something they need.  Given that there might be anywhere from 10 to 20 'bots in the field at any one time, the mean-time-between-failure for a 'bot needs to be on the order of 200-500 hours, so that a field supervisor can expect to go, at least day-or-two, without having to deal with yet another 'bot breakdown.   

Lastly, most crops are seasonal.  The ideal situation is for the length of the farming season to coincide with the time for a harvester/tender's major services.  This way, the winter off-season, when most 'bots would be out of service anyway, can be used to do the tear-down and rebuild maintenance necessary to get the 'bots ready for the next season.  This implies a 2,000 to 3,000 hours run time for our 'bot's power source.  

In the end, I don't know if any of these requirements are accessible to either a piston or gas turbine engine.  So I have some homework to do for the future.

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