EEVblog > The AmpHour Radio Show

#591 Olive a the world


of all the topics to wander into the weeds about! farm tractors!

You guys need to get an engineer from John Deere on your show. : ) sorry, I don't know any : (

A 50hp - 90hp tractor is tiny.  In the 1980s our field work tractors were about 75 kW [100hp] and those were smaller than some neighbors had and are not what you will find working fields today.

of course everything is relative.  Tractors are 'heavy' and 'powerful' from my point of view.  Here are some main points.

- Tractors have Diesel engines and these are good for delivering a flat torque curve vs RPM.

- of course the gearing is for relatively low speed.  Our highest road speed was probably 20 mph [32 kph] but today's tractors have higher road speeds.

- Tractors can probably do near 100% duty cycle.  The 100hp rated tractor might pull near that all day long when pulling a chisel plow, for example.  You might compare this to the hp rating of a car engine - but the 200hp car will only reach that for a freeway pass burst and normally use much much less going down the road.  I don't know the regulations about the hp rating on cars but it just seems you are not going to be able to load a Honda car engine to 200hp all day long.

The weight of a tractor is important so I am just guessing a battery powered tractor would be a bit of a challenge.  Tractors are heavy to the extent they need to do the job without breaking the frame but past some point there is an issue of compacting the crop soil too much.  That is why some tractors have tracks to distribute the weight over more area.

here is one that is 346kW rated

It would consume the energy in a Tesla car battery in less than an hour - as fast as 17 minutes or more likely about 1 hour since many tasks don't use full load continuously.  With a more modest row crop tractor maybe you would get 1.5 hours which of course is nothing compared to the required work day.

The topic of electronics on ag equipment is an interesting one, I don't know a ton about that but I know our family's 70-80's vintage tractors barely need electricity and they are still useful today, if a bit small for a real farm.  The battery is there for the starter, the lights and the radio.




I grew up on a small dairy farm in Wisconsin USA, hundreds of engineers of my generation were raised this way and most of these small dairy farms are now gone and the land switched to cash crops or merged to bigger dairies doing things a totally different way.

The main tractor on our family dairy farm was a 2940 John Deere, we used it for so many things.  It was purchased in the very early 80's as new and it is still on our farm today, no worse for the wear.  Diesel tractors are very simple and robust and just last.


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