Last week I attended the World Ag Expo held in Tulare, California.   I make it a point to attend exhibitions which challenge my legacy mind.   Although I grew up on a farm,  much has changed with the advent of Cesar Chavez and digital equipment engineering and GIS farming.

So I thought it would be an eye opener to visit the Ag Expo with my brother to learn more about modern agricultural equipment. About an hour into walking through the 1,600 exhibiters in the huge fair grounds I saw what looked like a 22 foot high upside down steel rocket nozzle.    This was farm equipment I knew nothing about – exactly why I had come to the show!

A younger fellow – in conversation with a possible sales client - seemed to be in charge of the booth.   I walked around the exhibit to try to make sense of it.   There was a control panel – but that was empty.  A couple of hoses went from the control panel to a 2.5’ diameter steel chamber at the base of the “rocket nozzle”.   There were two 5”diameter “piston” like parts out on a bench – I imagined that these were gas injection devices attached to cylinders at the side of the base chamber.  There were two spark plug wires going to each of the two cylinders. 

I asked the fellow in charge if the unit was mobile – because if there were hail threatening – wouldn’t you need to move the cannon around to protect different areas of the farm?  Mr. …..told me that the cannon wasn’t intended to be mobile.   The channel iron base of the cannon assembly was intended to be flooded with concrete to hold it in a permanent location. 

When I left the cannon booth I still wasn’t sure if the guy was a quack.   I  still didn’t know if there really was such a thing as a “hail cannon”. 

I asked my brother if he had ever heard of a “hail cannon”.  

Negative.

I pointed out that if the guy was a charlatan,  he was at least putting his money on the line for the booth.   

I didn’t understand at all how the cannon was supposed to work.   Planning on Googling the hail cannon at a later time, we went on our merry way through more of the Ag Show.

Low and behold, in the middle of the afternoon -  inside one of the huge tents which housed dozens of small vendors – we stumbled on a hail insurance booth.

Perfect.

My brother asked the hail insurance man (left in photo above) if an insurance discount was applied to those who had a hail cannon.   I’m not sure we got a straight answer to that question, but the insurance man did say that hail cannon’s do work.   He explained that during World War II, when the allies and the German’s were using large artillery against one another, someone noticed that the artillery shells caused clouds to break up. 

I think the hail cannon must be like a fellow who blows smoke rings across a room. The smoke moving across the room is real - because you can see the smoke.   Smoke rings moving across a room are not a shock wave (as explained in wikipedia in link in the next paragraph) phenomena,  smoke rings are the motion of a slug of air through a large body of static air.  

The hail cannon fires pulses of air - with repeated acetylene explosions - from the ground level up into the threatening hail cloud – both warming the cloud and dispersing it.   (This is my assumption only).  Here is more about hail cannons on Wikipedia.  

The insurance man said he lived in Northern California 3 ½ miles from  an Asian Pear orchard which had a hail cannon.    He said when the cannon was used it was very, very noisy – and he thought that the noise would become a limiting issue as more noise ordinances where imposed.   Some others believe that hail cannons prevent precipitation – and rain is the lifeblood of many farmers.

Hail nets over the orchard trees were another method of protecting the fragile fruit. 

So over the period of about an hour I went from never having heard about a hail cannon, to being a sort of expert in hail cannons.   Which was kind of exciting.

(Here is a photo of a hail cannon in an orchard  from NewtonFabrication.com,  Kingsburg, California, the hail cannon’s manufacturer).   You can see a New Zealand manufacturer here