From: cohill@vtserf.cc.vt.edu (Andrew M. Cohill)
Newsgroups: comp.human-factors
Subject: Re: Very poor human interface on Kubota tractor
Keywords: tractor controls
Date: 13 Apr 92 13:37:03 GMT
Organization: Fire in the Mountain

In article <j!sjabh.nagle@netcom.com> nagle@netcom.com (John Nagle) writes:
>
>       The manual for current model Kubota tractors indicates how bad
>things can be outside the computer field.
>
>       Braking involves two pedals and a lever.  The pedals apply brakes 
>separately to the left and right rear wheels.  A latch allows locking both 
>brake pedals together.  

I'm not trying to justify the design, but every tractor I've ever used
works this way.  At least they are consistent with traditional design.
Tractors would be a lot harder to use if you could not brake the wheels
separately.


>The lever operates the parking brake, but to
>operate the parking brake, both pedals must be latched together and
>depressed, the parking brake lever pulled, and the pedals released.

This sounds like a safety feature to me;  it is very unlikely that you
will accidentally engage the parking brake while reaching for one of the
the many other levers on a tractor that control, for example, the front
or rear hydraulics or the 3 pt. hitch.

>cautions that failure to lock the pedal latch before operating the tractor
>on a road may result in tractor rollover if brakes are applied
>asymmetrically.

Tractors are dangerous pieces of equipment.  If this worries you, don't
use them.

>
>       The key switch offers "pre-heat", "stop", "run", and "start"
>positions, this being a Diesel.  The manual states that turning the key to
>"stop" will usually, but not always, stop the engine, and a separate
>emergency off pull switch is provided if the key doesn't work.

If you are going downhill with a heavy implement attached and you turn
the engine off, the weight of the equipment (through the transmission)
may well provide enough compression to keep the engine running.  The
emergency off switch is a nice touch.

>        A lever is provided to lock the rear differential.  The manual
>warns that tractor rollover may result if the tractor is operated on a
>road with this lever engaged and a tight turn is attempted.

Differential lock is a very useful feature, and if misused or
misunderstood, very dangerous.  They are merely warning you about this.

>        This tractor has four-wheel drive, but no differential in front.
>The manual warns that tractor rollover may result if the tractor is
>operated on a road with four-wheel drive engaged and a turn is attempted.

Tractors are inherently dangerous.  It sounds like Kubota knows that
some of the people that buy their equipment are not familiar with this
fact, and try to point that out.  Ergonomics is not about *eliminating*
risk, it is about minimizing it.  A tractor that is completely safe to
use would also very likely be unusable by most farmers.


Andrew Cohill
(an HF person with many hours in a tractor seat....)


-- 
|          ...we have to look for routes of power our teachers never       
|              imagined, or were encouraged to avoid.   T. Pynchon          
|                    
|Andrew Cohill        cohill@vtserf.cc.vt.edu            VPI&SU                                                  
Newsgroups: comp.human-factors