SOFT TOUCH

for la these are suspensions the fella can't get very far witha not if he's driving a rig [Music] but why are there so many different kinds can the choice of a suspension really influence an operator's total profit picture can it change his maintenance costs appreciably and what about air suspension or is that just hot air many Fleet operators are taking another look we'd like to consider some of these questions during the next few minutes especially the matter of air suspension let's begin by asking what a suspension is really for anyway the fact is if roads were perfectly smooth a vehicle would need any suspension at all but unfortunately roads can't be made that way and springless rigid suspensions aren't practical at speeds above a crawl the purpose of a suspension is to help iron out the bumps and irregularities in the road it attempts to do this by permitting the wheels to move independently with respect to the rest of the vehicle thus cushioning the jolts that would otherwise be transmitted to the vehicle chassis the cargo and the driver and passenger early suspensions were only partially successful in this regard Engineers have tried many different kinds of springs for suspending vehicles on their axles there were buggy style elliptical leaf springs more recent semielliptic spring Stacks coil springs steel torsion springs rubber in compression rubber in Shear combinations of rubber and helico springs and pneumatic Springs that float the vehicle on a cushion of air it is the most highly developed of these pneumatic Springs Firestone air ride Springs that we want to talk about we'd like to explain what they are what they do and why they result in improved more profitable operations the simplest kind of an airspring is a piston operating in a cylinder taking advantage of the inherent springiness of air as it is compressed such airs Springs actually were used on vehicles as early as the Civil War period but the Piston seals tend to leak and their friction adds too much harshness to the ride modern Firestone airsprings look like sophisticated balloons but they are actually highly engineered packages of compressed air designed to change their shape under Dynamic conditions in order to produce ideal spring characteristics just how sophisticated they have become is indicated by the fact that airs Springs have been under development for more than a century with a number of dead ends investigated along the way some of these efforts had no chance of working satisfactorily technology just had not matured efficiently others were released before attendant plumbing and Equipment were properly developed indeed there has been some justifiable criticism directed at air suspension trailers employing some of these early designs for the plain fact is that there is no magic in air unless an air spring as on this modern suspension is designed to take advantage of Air's unique characteristics modern air suspension began at Firestone about 30 years ago when inventor Roy Brown and his men set out to develop a Pneumatic spring that would take advantage of all the desirable properties of air his success can be measured by the family of more than 100 designs of airride Springs which Firestone manufactures today airs Springs that carry loads from a few pounds to as much as 15 tons a piece these are produced in fireston air ride plant at Noblesville Indiana using processes that have been developed over a period of 30 years these processes include calendaring cord bias cutting building and curing the airspring after curing or vulcanization bead plates generally are crimped over the ends creating a hermetically sealed assembly every air Rider assembly shipped out of firestone's Noblesville plant is checked for air tightness and proof tested at twice the maximum design load an air ride spring hardly seems strong enough to support a vehicle and in fact it doesn't the vehicle is supported by a column of compressed air enclosed by the flexible walls of the package which are made of oil and salt resistant synthetic rubber reinforced with multiple Plies of high tensil strength nylon type cord locked in place around metal bead wires the resulting assembly can withstand many times the operating pressure for which it was designed these are some of the reasons why firestone's modern air ride Springs have been so successful continuing development and evaluation in the physical testing laboratory is another but what do airsprings offer that more conventional spring suspensions don't air ride not only makes possible a much softer suspension but one that stays soft whether the vehicle is empty or loaded here is a simple experiment that dramatically demonstrates how air ride Springs can smooth out the bumps the pingpong ball container on the right is fastened directly to the axle the one on the left is on the isolated cargo side of the airspring you don't need an accelerometer to see the difference airide not only makes possible a softer suspension but one that stays soft whether the vehicle is empty or loaded compare these ride meter traces which measure the ride on two vehicles driven over the same road if you don't have this kind of instrumentation a fairly easy way to measure the softness of a suspension is to bounce it up and down at its so-called natural frequency and count the number of bounces in 1 minute the lower the number the softer the suspension and the better the ice insolation from Road shock if the result is over 100 bounces or cycles per minute the suspension will probably be hard on passengers if it is over 150 cycles per minute it will be hard on the cargo and the vehicle itself the problem with conventional Springs is that the natural frequency doesn't stay put everyone knows that most vehicles have a pretty good ride when they are loaded it is a rough empty ride that tears up the chassis and the maintenance budget especially when interleaf friction adds to the shark of high natural frequencies this becomes clear if we simply suspend a weight on a conventional spring with a heavy load the natural frequency is about 130 cycles per minute but as the load is removed the natural frequency goes up to 190 cycles per minute now let's try the same experiment with an air IDE spring under the heavy load the natural frequency is only 55 cycles per minute but with the heavy load removed the frequency still is only 59 cycles per minute comparing the resulting traces makes it obvious that the air ride spring shown on the right produces a much softer and more constant ride free from the harshness of frictional damping what this means is that with air suspension the cargo the passengers and the vehicle get the same soft ride under all conditions of loading and because destructive Road shock is eliminated tires last up to 60% longer as a result conventional Springs on buses are virtually obsolete since going over to airride in 1953 one principal bus operator has saved about $1 million per year in Spring maintenance [Music] alone many of these coaches have gone over a million miles on their first set of Firestone air rides that the passengers enjoy a softer ride is common knowledge that the coaches themselves last much longer is now an established fact similarly operators of tank trailers particularly appreciate the constant softness of air ride since tankers must operate empty about half the time and it is the empty tanker that is damaged by pounding over the road particularly the modern tanks made of lightweight Metals moreover no one knows that a leak has developed until it is too late then the tank must be emptied and flushed out before it can be safely welded meanwhile the trailer isn't earning any money while it's in the repair shop on Firestone air suspension an empty tanker rides as Softly As a full one and the tanks even aluminum tanks last much longer since they are cushioned from destructive Road shock fragile caros get to their destination without damage claims on air rides many shippers have found they can cut packaging costs the military services now protect sensitive electronic equipment and missile instrumentation on air suspension eggs shipped on air free from scrambling vibration candle grade A upon arrival and here are some passengers that appreciate the softness of air ride but their owners appreciate it even more cattle haulers have found that animals lose less weight when they travel to Market on Air Forces arrive actually fresh for racing drivers naturally are less fatigued do a safer job because air ride cushions the vehicle itself the whole structure can be made lighter this truck manufacturer saved nearly a ton of dead weight in its air ride tractor design adding the same weight to payload profit and not only does the vehicle chassis last longer there is evidence that air ride axles are actually easier on the road itself the softness and compactness of air suspension helped make possible this unique van with 35 ft of doors on a 38t trailer this same van has air rides in the fifth wheel section as well as in the suspension thus floating the entire trailer on air regardless of the kind of tractor used another special vehicle made possible by air suspension is this unique trailer which operates like a 40ft tandem on the highway but splits apart into two 20ft single axle units for local delivery and the fact that the axles are pneumatically coupled provides precise load Equalization without heavy mechanical interconnections by contrast a very different special airide vehicle is this three-wheel electric postal [Music] truck railroad air suspension today provides passenger Comfort on commuter trains and Rapid Transit cars and permits lightweight construction on these coaches on Air Force Radar trains air rides cushion electronic components let's take a minute to look over a typical air suspension system in addition to the air ride Springs themselves there are leveling valves with plumbing leading to a reservoir air tank that is filled by the air compressor after the air brake system is up to pressure to simplify things a bit the vehicle as we have seen is supported on Columns of compressed air enclosed by the airride spring packages as load is added to the vehicle the air is further compressed and the body sinks down opening the leveling Valves and admitting air to the Springs from the reserve tank as the pressure in the air Springs increases the vehicle body returns to its original height and the valves automatically shut off if the load is removed from the vehicle the valves open to the atmosphere bleeding off excess air pressure until the vehicle is releveled but the real secret of air suspension is that each time the vehicle is releveled it is this same ch change in air pressure inside the air ride Springs that also makes them softer or stiffer as necessary to compensate for changes in load thus retaining the same natural frequency the same ride under all conditions of loading but the leveling itself has advantages constant platform height is an obvious one the bed is the same same height no matter what the load and the bed remains level no matter where the load is placed on buses this means constant step height moreover because the vehicle does not sink down underload as it does with conventional Springs the chassis can be designed for constant overhead and Road clearances on a 35- ft trailer this can add 70 cubic feet of payload volume with the addition of manual valves other unique functions can be performed with this leveling feature using the air ride Springs as pneumatic jacks or actuators for example saves hours in moving heavy equipment this same sort of technique can be used to move the vehicle through tight vertical clearances such as loading aboard aircraft or shipboard because air balances the load between axles and eliminates friction airri Vehicles can achieve phenomenally good load Equalization an operator thus can load right up to the legal limit without risking a fine and trimmer controls can actually shift the load and adjust each axle to carry its maximum permitted capacity one question frequently asked by operators contemplating their first purchase of an air ride vehicle is what happens in the event of damage to some part of the air system modern air suspensions have a system of check valves which localize and minimize the effects of any such damage but Firestone air ride Springs also have a built-in safety feature if a spring should be deflated it merely settles down on the internal rubber compression bumper and the control and mobility of the vehicle remain unimpaired and if an airspring Ever requires replacement the job can be done in 30 minutes time as compared with 4 to 8 hours with other types of Springs to summarize then by overcoming Road shock and vibration air ride offers these advantages reduced operating costs through decreased vehicle maintenance reduced cargo damage increased vehicle life increased Tire life and greater driver comfort and safety air ride also means increased payloads because of reduced vehicle weight and increased cubic content as a result of leveling leveling also means loading convenience with constant or adjustable platform height pneumatic jacking and other special techniques that are afforded only by air suspension we have implied that not all airs Springs take advantage of the unique characteristics of air one way to be sure you are getting the benefits of modern engineering research and development in your air suspension is to look for this trademark [Music] for modern Firestone air rde Springs are indeed a soft touch to the operating budget as to the vehicle and cargo Firestone airide in fact has sired a whole new family of vehicles and has made possible suspension designs that Herald a new era in commercial vehical progress a [Music] [Applause]