Tow and Blow Frost Protection Background

Tow and Blow Frost Protection Background

Tow & Blow; the first truly portable Wind Machine; has been developed by NZ’s foremost expert in the Wind Machine industry.

Some 25 years ago after returning home to NZ from living in the USA for 8 years (where he studied the use of Wind Machines for frost protection); kiwi engineer Kim McAulay began importing US models into his home country.
It didn’t take long for Kim’s creative instincts to kick in for him to design his own Wind Machines. The “Frost Boss” is now well known throughout the world for its innovation. Kim sold “Frost Boss” 11 years ago.

But the giant of the Wind Machine industry couldn’t sleep!! He had learned so much during those 25 years, and he knew he could take all of the problems and issues that have emerged over time with Wind Machines and develop something that over comes them all. The Tow & Blow is now presented to you as the culmination of those years of experience.

The biggest issue that Kim identified was the inefficiency of the current machines. The inefficiencies came about for safety reasons. Wind machines had moved away from having their engines on top of their tower (only accessed by climbing the ladder some 30 odd feet up) to being ground powered. Large diesel engines mounted on the ground driving through clutch-es, gear boxes and long drive lines powered the fans. This wastes an enormous amount on energy, uses lots of fuel and is very expensive to maintain. Kim describes it “like pushing water up hill”.

An example of the power inefficiency is as follows:

  • A 4 bladed ground power wind machine advertised as 150hp.
  • The 150HP relates to when the machine is running at 2500 RPM, but the machine only runs at 1750 RPM.
  • At 1750 RPM it now leaves just over 100 HP at the fly wheel to use.
  • But we now have to send this power through a clutch; a right angle gear box; then up 30 odd feet of drive shaft, then through a 96 degree top box with rotation worm drive.
  • So now at the prop shaft we have about 70 HP available to spin the fan.
  • The open style fan is around 5 meters in diameter. This length on its own and the fact that it is un-shrouded creates an enormous amount of drag consuming a large % of the HP left over before giving any airflow for frost protection (most likely to be in the 40 HP range).
  • This now leaves only 30 HP of usable power for producing air. When we further reduce the volume of air by the fact that the fan blows against its own tower as it rotates, we calculate that the final result is 20 hp of useable power.
  • Remember we started with 150HP on the ground. This is not at all efficient.
  • Claims in published report to move 19 m/s of air. But this is only at one point on fan, being the point that blows directly over its own tower as it rotates. OPUS reports show the true velocity of air to be 12 m/s of air averaged across the blade. This still doesn’t take into account the loss of velocity and volume of air by the obstruction of the tower. The tests were all done in an unobstructed environment with no duct or shroud.

Now compare the Tow & Blow:

  • Velocity is 23 m/s of air (far greater than the big open fans using 150 HP ground powered engines).fan head half raised (1280x851) (2)
  • The Tow &Blow uses a 23.4HP Kohler Diesel liquid cooled engine, delivering power through a Brevini Planetary Gearbox.
  • The Impeller has a high performance composite fan with adjustable pitch for maximum airflow.
  • SHROUD:-The impeller is in a bell mouthed case/shroud that increases its performance by up to 95%. Aerodynamically designed to maximise airflow. Having a shroud is like turbo charging the fan
  • STRAIGHTENING VANES Air exits a fan in a spiral motion which causes the airstream to lose energy; the straightening vanes on the Tow & Blow take out the spiral motion and maximise the energy in the airstream.
  • It also blows unobstructed away from the machines tower.
  • It uses 5 litres an hour of fuel. Now we’re talking efficient!!