1948 Solar-Powered 8N Ford Tractor


     The 8N tractor is the fourth in a series of test vehicles built to explore the viability of self-produced electrical energy for agriculture and transportation in a post-fossil-fuel, sustainable future.

     The 8N is a much larger, more powerful, and heavier tractor than the Farmall Cub.  It could do considerable work for commercial or co-op farming without the complexity and the 20% of crop land needed for biofuels (horses and diesel).

8N Specifications:

(also 2N or 9N Fords)

Weight: original, 2500 pounds ... with batteries, 3700 pounds.

Battery Pack: ten DEKA 9C12 220Ah, 12-volt industrial batteries weighing 128 pounds each and rated for two hours at 75 Amps (150 Ah).  Four batteries over offset left rear wheel, the rest in front.

Gearing: This is the critical issue.  Tractors need low speed torque which can only be provided by high current in electric motors.  The Farmall Cub uses a 1.6:1 tooth-belt drive to achieve ample torque.  The 8N with direct (L-91 advanced) motor drive requires the extra low ratio of a Sherman transmission to decrease current and over-heating in the controller and motor.  Future work will be directed to adopting a tooth belt reduction drive, which can be used in all N-series Fords without Sherman transmissions.

Work Capacity: The Ford 8N requires almost 5 Hp just to energize and move itself in soft ground.  An additional 7 Hp is required for maximum continuous work like 16-inch plowing or double disk harrowing in new ground at 2 mph.  The total of 12 Hp (about 9 Kw) requires 75 Amps.  This can be supplied by the 1300 pound battery pack for two hours. (18Kwh or equivalent to 2 gallons of gasoline).  This output will plow or harrow ½ acre in two hours.

Recharging: With 75 Amps out and about 5 Amps in (in direct sunlight) it does not make sense to carry the array on the 8N.  It requires 30 Amps (six times direct sunlight) just to power the tractor.  It would require 15 hours to recharge the batteries with two 4-panel arrays (10 Amps times 15 hours equals 150 Amp hours).  A full-wave bridge rectifier will recharge at 10 Amps if grid power is available.

Cost: Used tractor $2000, batteries $2000, drive system and labor $6000.  Total $10,000, exclusive of panels, which may be on the house or tractor.

          Just as with transportation, dilute solar energy cannot possibly directly supplant fossil energy for agriculture.  However, it is far better than nothing and can work synergistically with other home power requirements.   The purpose of this work is not to sell solar power, but instead to show how few and feeble are our options in the fast-approaching fossil-fuel depleted future.


Serious Agricultural Power including 3PT CAT I Hydraulics and 540 rpm PTO