Streamlined Trucks
4 years 9 months ago - 4 years 9 months ago #201410
by Lang
Replied by Lang on topic Streamlined Trucks
Air drag of course can be a useful tool.
Many people believe the round holes in the centre of canvas signs such as advertising or those big banners across the street advertising the coming town fair are to allow air to escape to reduce wind pressure.
Not so. As we said above, air passing over a sharp edge creates a vortex and large drag forces. With no centre holes the sign would bounce and flap as the air spilling over the edges created uneven vortices. By having focused, deliberate drag points by putting in holes it is the same as putting on anchor tags and ropes on the back of the fabric to stabilise the sign.
Ever wonder why a parachute has a hole in the centre? Same reason - it creates a focused drag point in the highest point by the air escaping, spilling over the hole edges and creating drag right in the centre to stabilise the chute. Parachutist have experimented with cutting holes in their parachutes to achieve a specific purpose such having the ability to track instead of just falling straight down. They get the same effect as somebody flying behind pulling strings to create drag in a certain direction.
Jet aircraft and drag car parachutes are a seemingly silly round ones full of holes, square or cross shape, how is that going to catch the air. It doesn't. The strange shape has as many edges as possible for the air to break away and spill over creating vortices and lots of drag.
Many people believe the round holes in the centre of canvas signs such as advertising or those big banners across the street advertising the coming town fair are to allow air to escape to reduce wind pressure.
Not so. As we said above, air passing over a sharp edge creates a vortex and large drag forces. With no centre holes the sign would bounce and flap as the air spilling over the edges created uneven vortices. By having focused, deliberate drag points by putting in holes it is the same as putting on anchor tags and ropes on the back of the fabric to stabilise the sign.
Ever wonder why a parachute has a hole in the centre? Same reason - it creates a focused drag point in the highest point by the air escaping, spilling over the hole edges and creating drag right in the centre to stabilise the chute. Parachutist have experimented with cutting holes in their parachutes to achieve a specific purpose such having the ability to track instead of just falling straight down. They get the same effect as somebody flying behind pulling strings to create drag in a certain direction.
Jet aircraft and drag car parachutes are a seemingly silly round ones full of holes, square or cross shape, how is that going to catch the air. It doesn't. The strange shape has as many edges as possible for the air to break away and spill over creating vortices and lots of drag.
Last edit: 4 years 9 months ago by Lang.
The following user(s) said Thank You: Zuffen
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4 years 9 months ago - 4 years 9 months ago #201411
by wee-allis
Replied by wee-allis on topic Streamlined Trucks
Back in the early 70s I was working for Lindsay Brothers in their Sydney depot when they fitted their very first roof air foil. Remember those small ones about a metre or so across? After a few weeks trial, I asked Tom how it was performing. His exact words were, "Gives us about a quarter of a mile per gallon extra."
Sad thing is, I can't remember whether it was on a KW or one of their first Louisvilles, which were coming on line about that time.
Sad thing is, I can't remember whether it was on a KW or one of their first Louisvilles, which were coming on line about that time.
Last edit: 4 years 9 months ago by wee-allis.
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4 years 9 months ago #201418
by overnite
Replied by overnite on topic Streamlined Trucks
Anyone remember “The apparition “, in NSW, many years ago from a converted Louie? Early streamlining at its best.
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4 years 9 months ago #201419
by Swishy
OF ALL THE THINGS EYE MISS ................. EYE MISS MY MIND THE MOST
There's more WORTH in KENWORTH
Replied by Swishy on topic Streamlined Trucks
OF ALL THE THINGS EYE MISS ................. EYE MISS MY MIND THE MOST
There's more WORTH in KENWORTH
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