The platform scale was once to be found on every railway station, farm and
feed store in England.  From letters on the list it was also common in the
Americas.  Made of steel and cast iron, operated by a series of levers, no
springs, it is practically indestructible and is ideal for the beekeeper.  
Now largely replaced by more modern devices they can be found rusting away
in old barns and scrap yards.  Over three years I picked up five at prices
from five to twenty five pounds.  In each case the mechanism was perfect
and after stripping and cleaning they all responded to less than a four
ounce change in weight.  When found lthey are usually without the weight
pan and weights but a pan is easily fabricated.  The beam is graduated from
zero to twenty eight pounds so a 28lb weight can be accurately made from a
small canister filled with lead chips or shot from cartridges.  The weight
is approximately four and a half ounces so one needs an additional 9oz,
18oz and 36oz to complete the set.   
The beam mechanism needs protection from the weather.  Mine are all in a
beehouse so no problem.  The hive stays on the platform all the year round.
 In winter it is a good indicator of consumption.  In the morning in summer
it will indicate the rate at which foragers leave the hive.  Foragers leave
with a minimum of food and weigh around 4500 to 5000 to the pound.  Zeroing
the scale at seven in the morning I often find a weight loss of three
pounds or more by nine oclock,  thus indicating that some 15000 bees are
already on the wing.  A heavy nectar flow during the day is followed by a 
three to three and a half pound drop during the night, indicating the
evaporation of one to two pints of water.
In my part of the world nectar flows of any consequence occur from early
May to mid July, a mere two and a half months.  Monitoring hives daily
shows clearly that flows are usually of short duration and are largely
controlled by the weather.  Our weather is very fickle so one day can see 
an intake of fifteen pounds of nectar and the next day nothing, due to
sudden heavy cloud or rain.
With such a short interval for nectar the loss of a  swarm in May is a
disaster.  Thus for me the art of beekeeping is swarm prevention, the
selection of queens for non-swarming, frequent re-queening and the
maintenance of a strong foraging force from late April to July.
                                                        Sid P.