Is bike suspension suitable for E Baja vehicle?

It’s better to use fox or Polaris suspensions designed for ATVs.

Most probably there would be a need of 6 Inch play in the wheel and considering the motion ratio of 0.6 there would be a need of 10-inch play and therefore no bikes are designed to this spring compression. You can use bike suspension like Yamaha FZ, KTM duke series, and RE Himalayan mono-shocks but that doesn’t justify the purpose of the vehicle and also bike suspension eye to eye length is very less so it would create a problem.

Fox offers a discount for Baja students in the form of sponsorship at will help teams economically as well.

Camber: What Is It And How much you should keep?

While the eye-catching tuning phenomenon known as “demon camber” or “hella flush” doesn’t provide much in the way of performance – in fact it hurts it – its extreme styling brings the viewer’s eyes into relation with the concept of camber, something which evades casual drivers and even a few petrolheads.

dsc_0664

With its wheels mounted strangely, as if the suspension were broken, this car’s unconventional stance makes for strange reactions from both the layman and the enthusiast alike.

In learning a bit about how camber works, its role in tire wear, cornering performance, ease of adjustment, and the limitations various suspension designs have when it comes to camber, any car’s handling can be quickly optimized for a reasonable cost.

Wheel Camber

What is Camber?

Camber is the angle at which the wheel and tire stand relative to the road – assuming it is perfectly flat. The easiest way to envision what camber looks like is to view the wheel and tire head on. When stationary, the tire maintains a static camber angle, whereas when the car is cornering, due to body roll, the contact patch is reduced. In order to counteract this effect and have the greatest amount of tire on the road while cornering, camber settings must be taken into consideration and adjusted accordingly.

While conventional thinking might lead one to believe that the wheel is perfectly perpendicular to the road on which it sits, it is often intentionally tilted slightly to counteract the forces imparted on it by cornering. If the top of the tire is leaned in closer to the center of the car, that particular wheel and tire exhibit what is called negative camber. Positive camber, on the other hand, has the top of the wheel pointed outwards. While this article delves into the merits of negative camber, there are benefits to some positive camber in racing as well. However, this situation is typically isolated to circle track racing where cars run on banked race tracks.

How Does it Work?
Negative camber is the characteristic generally desired in performance driving. When we use the term, we’re referring to static negative camber. That is, the wheel and tire should exhibit some negative camber while sitting. When you barrel into a corner, the laws of physics have you, the wheels, and the tires pushed toward the outside of the corner.

Tire-Camber-CorneringWhen the wheels and tires are pushed outwards and the car’s body rolls, the contact patch, or the area of the tire which comes into contact with the surface of the road, diminishes significantly as it rolls over onto its outer shoulder.

Negative camber is implemented so that when the car is cornering and the wheel is rolling over and gaining positive camber (from body roll, not suspension travel), the static negative camber should correct whatever effect leaning and lateral load have on the wheel and tire; resulting in a near-upright tire and the greatest possible contact patch.

Simply put, negative camber helps counteract the natural tendency for a tire to roll onto its outer shoulder while cornering, keeping the contact patch squarely on the road while cornering allow for more grip and higher cornering speeds.

There are some reasons that your car likely did not roll off of the showroom floor with optimum camber for the track. Too much negative camber causes the car to tramline; or follow cracks or imperfections in the road, and also have an excessive sensitivity to the road’s crown (an engineered 1 to 2 percent curve that promotes water drainage on roads). It also isn’t very friendly to tires, causing them to wear at a significantly higher rate. As a general rule, a car that’s sole purpose is commuting should have minimal negative camber – unless you don’t mind replacing tires regularly.

The trade-off present with adding negative camber is that it often reduces the initial turn-in of the car somewhat. Static negative camber places a smaller percentage of the tire’s carcass on the road when moving in a straight line and consequently, when the tire hasn’t been leaned over completely – at the entry of the corner, for instance – there may be a sense of diminished grip until the car is “loaded up” and the contact patch is widened.

sucp_1004_12+muscle_car_alignment_basics+tire_temp

An infrared thermometer is a useful tool for assessing whether a camber setting is working well for the car. However, tire temperature rapidly cools so readings need to be taken as quickly as possible after a session.

 

How Much is Too Much?

How much negative camber do you want? It depends on what kind of suspension setup your car has. Cars with MacPherson struts need a significant amount of static negative camber because they have only a moderate camber gain under compression, when compared to a car with unequal-length control arms. When combined with the effect of body roll, the end result is usually less negative camber than desired, therefore requiring the addition of extra static camber. Cars with unequal length A-arms or multi-link suspension do not exhibit this shortcoming; they’re engineered to have a faster, more progressive rate of negative camber gain during cornering.

Determining what camber setting yields an evenly-applied contact patch can be done through measuring the heat at the inside, the center and the outside of the tire’s contact patch. By using a thermometer one can determine if one side of the tire is being worn more or less than the other. Generally speaking, the inside of the tire should be 10-15 degrees hotter than the outside, depending on the track and the temperature measuring points. If the inside is exceedingly hot and wearing faster than the outside, there is too much negative camber. When this is present with the front wheels, the effect is diminished braking capability, poor turn-in and pronounced mid-corner understeer. When the rear tires exhibit too much negative camber, the effect is oversteer and a reduced ability to accelerate cleanly out of corners.

The opposite, excessive positive camber, shows up as a reversal of the aforementioned temperature spread. The outside is excessively hot and wears much faster than the inside of the tire. This leads to understeer mid-corner after the car has made its initial turn, and is usually the result of too much roll. It is because of this that excessive roll must be limited with anti-roll bars.

How Do I Adjust Camber?

Double_wishbone_suspensionTo make adjustments to a MacPherson-suspension car, adding camber plates is a safe, easy and cost-effective way to doing it. Camber plates use an adjustable top mount which relocates upper shock mount to a retainer plate which slides laterally on a grooved track. Because the strut attaches directly to the hub, adjusting camber from the top mount is possible. Simply slide the adjuster toward the center of the car for increased camber or outward for less.

This is an attractive approach to adjusting camber especially if you autocross/track your car and want one camber setting when battling the clock, and another when driving home on the freeway. The addition of camber plates also spruces up the appearance of your engine bay.

Camber bolts are another cost effective way of adjusting camber easily. Camber bolts are eccentric, meaning they have an off-centered lobe which alters the horizontal position of the knuckle slightly from the strut, therefore changing the camber angle. Camber bolts are also referred to as “crash bolts” because they are used to align cars which have been bent in an accident. Due to their design, they’re thinner than standard bolts and can be weaker. For that reason, it is important to make sure camber bolts are of high quality and sourced from a reputable manufacturer.

supra-cage-134

Here is an example of an adjustable upper control arm. Notice the heim joints at the mounting point. These can be screwed out or in which can effectively pull the top of the tire in or push it out.

For cars with a multilink or unequal length A-arm setup, the shock/strut does not directly control camber. In order to change the camber on cars with these suspension setups, one of two things needs to happen. One, the mounting points of one control arm need to be moved; this is often accomplished on factory suspensions by rotating an eccentric bolt that carries the control-arm-to-chassis mounting points. Or two, the length of one (or both) of the control arms need to changed. Be warned that altering the length of either of the control arms significantly will affect camber gain during suspension travel in addition to static camber.

If the car in question doesn’t have an adjustable upper control arm or upper control arm mounts provided from the factory, nor is there an aftermarket adjustable upper control arm, sometimes shims can be used behind the control-arm-to-chassis mounting point to adjust the camber – this is often the case in older vehicles.

Conclusion

For anyone seriously considering the performance potential or their car, camber is something that should not be overlooked. The feeling of increased grip and poise mid-corner is something that is sure to plaster an ear-to-ear grin on anyone’s face. Because most street cars are not designed with the race track in mind, their camber settings are somewhat conservative to ensure even tire wear in normal driving conditions.

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Minute camber adjustments can make a standard car significantly more agile. As we’ve learned, when considering suspension adjustments it’s important to take into account your suspension design, but more importantly; use a scientific approach to determining what kind of camber is appropriate for your car. Though adding some negative camber will allow for higher cornering speeds and a more progressive feeling at the limit of adhesion, it can lead to premature tire wear, whereas improperly adjusted camber can result in instability and reduced traction.

Don’t let that prevent you getting out there and experimenting; it’s fun and educational. One parting suggestion: don’t forget to see if your tire provider will sell in bulk.

Dynamic Analysis of the Transmissibility of the Rear Suspension of a Mini-Baja Vehicle

This work presents a dynamical analysis of the transmissibility of an off-road vehicle rear suspension, which was developed in CEFET-RJ for the Mini-Baja / SAE-Brazil competition. A finite element model was developed to identify the critical points of the structure. Afterwards, electric strain gages were bonded at the most critical points to measure the dynamic strains due to an impact load. Accelerometers were bonded before and after rear suspension system to measure the main transmissibility characteristics of the suspension. The data obtained through an A/D converter with instrumentation software was used to evaluate the transmissibility of the rear suspension and other important dynamic characteristics. Finally, a simple twodegree of freedom model was developed to study the behavior of the rear suspension and the influence of the main parameters in the transmissibility of accelerations and
loads to the structure. An estimate for an optimal suspension adjustment was obtained with this simple model. The results obtained with this methodology indicates that it can be used as an effective tool for the design and improvement for Mini-Baja vehicle, as the designer can work with more realistic loads.

DOWNLOAD – Dynamic Analysis of the Transmissibility of the Rear Suspension of a Mini-Baja Vehicle
SAE White Paper

How Suspension Coils / Springs are made ? Raw materials & Design Explained

I’ve noticed a lot of colleges are running air shock’s instead of coilovers, this shocked me because in a fullsize vehicle air shocks tend to over heat easily at high speeds, thus loosing their valving and tending to raise the ride height, because of this there only really recommended for rockcrawlers.

what advantages are there to running an air shock over a coilover?

First off, they weigh nearly nothing. A fox float weighs 2.1 lbs, an evol ~4 lbs. In a lightweight vehicle application like Baja, they seem to dissipate heat quickly enough to be consistent over an endurance race.

Secondly, they can be fully adjusted with a mere hand pump and a few finger twists. This is partly laziness, in that we don’t have to go out and collect all of the right springs for every occasion, but it also allows us to adjust everything within two minutes. This is quite useful when ideal suspension settings are different for maneuverability and suspension courses. We can also adjust to driver preference on the endurance race.

Finally, in the case of fox shocks at least, we don’t need external bump stops. Evols progressively increase in pressure enough to prevent bottoming out anyways.

The real disadvantage of air shocks is the cost so far. As long as you have enough air in your Floats, bottoming out willn’t appear to be a problem. In many cases your throttle might stuck right before a jump causing us to get some massive air and bottomed out the front suspension so bad that it can snap the a-arm upward.

You can also opt for Polaris OE (Fox) shocks off of the RZR . They rock, just have to get softer springs for them. Also,

Raw Materials

Steel alloys are the most commonly used spring materials. The most popular alloys include high-carbon (such as the music wire used for guitar strings), oil-tempered low-carbon, chrome silicon, chrome vanadium, and stainless steel.

High strength steels for automotive applications like suspension coil springs and engine valve springs are alloyed with high amounts of silicon because it confers increased strength and hardness (solid solution hardening), higher sag resistance (resistance to load loss, resistance to stress relaxation) and temper resistance (resistance to softening during tempering and stress relieving). Contemporary spring steels are quenched and tempered to very high strength (1900-2150 MPa, 53-57 HRC, 560-640 HV).

Other metals that are sometimes used to make springs are beryllium copper alloy, phosphor bronze, and titanium. Rubber or urethane may be used for cylindrical, non-coil springs. Ceramic material has been developed for coiled springs in very high-temperature environments. One-directional glass fiber composite materials are being tested for possible use in springs.

The Manufacturing Process

The following research papers focuses on the manufacture of steel-alloy, coiled springs for BAJA Suspension

Download:

Design and Analysis of A Suspension Coil Spring For Automotive Vehicle

Optimum Design and Material Selection of Baja Vehicle

Baja Project ‐ Suspension Design Methodoly from BAJA Tutor

Designing an Independent Rear Suspension for Baja SAE Vehicle

SAE Mini-Baja – Suspension and Frame Design

Design of Helical Coil Suspension System by Combination of Conventional Steel and Composite Material

 

 

 

OFF-ROAD SUSPENSION DESIGN: Ride and Handling of BAJA Buggies (Off Road Suspension Design Book 1) (English Edition)

This Book consists in a definition and analysis of BAJA suspension geometry to an off-road vehicle. The suspension selection is accomplished through the study of its geometric characteristics to design its dimensions and position of installation in the vehicle according to the expected behavior. The current suspension of the vehicle, on the front and rear axles, is analysed for understanding its dynamic behavior. The vehicle in analysis is a “Mini-Baja”, off-road prototype, which is used to run nationals competitions between engineering colleges.

After Completion of this book, you are eligible to apply for a copy of MSC ADAMS Car. The competition guidelines will be updated in the first week of April 2016.

Suspension should be designed in a way which would help in making a vehicle provide
resistance to all impact loads. The compatibility of the A-arms and 3-link suspension with the detailed parameters can produce exceptional results in the graphs of camber and caster variations , toe angles ,Ackermann geometry , proper flow of forces from chassis to ground, bump steer and shock absorber characteristics. This ensures that the off-road vehicle would improve its perceived quality of its dynamic performance and would provide good driver satisfaction in concert with excellent vehicle packaging. The same
design could be used in other off-road vehicles like Forest Rangers, Military Cars and Trucks, even in many Passenger Sports Utility Vehicles with slight variations as per the vehicle specifications and usage.

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Book details

  • Format: Kindle Edition, Digital Edition
  • File Size: 6134 KB
  • Print Length: 56 pages
  • Simultaneous Device Usage: Unlimited
  • Publisher: Avinash Singh; 1 edition (7 March 2016)
  • Sold by: Amazon Digital South Asia Services, Inc.
  • Language: English
  • ASIN: B01AVHGUSC
  • Text-to-Speech: Enabled
  • X-Ray:
  • Word Wise: Not Enabled

Using swingarm angle, chain pull and antisquat to maximize traction.

Figure 1: A typical sportbike layout, showing the relationship of the chain run and swingarm. The red arrows show the three forces that affect anti-squat: driving force, chain pull, and weight transfer.

As sportbikes become more and more powerful, rear-end geometry plays a greater part in determining how well that power gets to the ground. Some production bikes now have adjustable swingarm pivots, which is one part of the equation, and while the pivot height–which can be used to change the swingarm angle–plays an important role in antisquat geometry, there is much more to consider.

The reasoning behind antisquat is as follows: When you get on the gas exiting a turn, that acceleration results in weight transferring to the rear wheel, commonly called squat. While a certain amount of squat loads the rear suspension and improves traction, too much can unload the front wheel and have you running wide on the turn exit–or worse. Today’s literbikes can easily transfer all their weight rearward (a good thing if you’re into wheelies), and left unchecked, that weight transfer would spell disaster on turn exits. How much weight is transferred under acceleration is dependent on the wheelbase and the relative position of the bike’s center of gravity. To stop the rear suspension from squatting too much, a certain amount of antisquat–working against that weight transfer–is desirable.

Figure 2: The three forces all act on the swingarm at the rear axle; and their moments about the swingarm pivot can be calculated. As the rear suspension compresses, the geometry of the force diagram changes-sometimes significantly. Note that while the chain pull always creates an anti-squat tendency, the driving force torque changes from anti-squat to pro-squat as the suspension compresses and the swingarm passes horizontal.

There are two forces in the rear end that can be utilized–and even tuned–to nicely counter that weight shift. One is the driving force, or thrust, that pushes the rear wheel forward. Because the swingarm is at an angle to the ground, a portion of that forward thrust acts to lift the back of the bike–much as you can push horizontally on the bottom of a ladder against the side of a building to raise the ladder more. Like the ladder, the greater the angle of the swingarm, the more force is transferred into lift.

The second force that can be used is chain pull, which also acts to extend the suspension as it tries to pull the rear wheel in the direction of the top chain run. This force’s magnitude is dependent on the relative sizes of the rear tire and rear sprocket, and its direction is determined by the sizes of the front and rear sprockets. Weight transfer manifests itself as the ground pushing upward on the rear wheel–compressing the suspension–and all three forces are proportional to the amount of acceleration. Figure 1 shows a typical sportbike rear end and the three forces (weight transfer, driving force and chain pull), with the lengths of the red arrows representing the magnitude and direction of each.

Figure 3: The three torques plotted against suspension travel. The chain pull has a much greater influence than the driving force moment, showing how sprocket selection on a big bike can drastically affect handling.

We can make some assumptions to isolate the forces that act on the swingarm and, using some measured dimensions–from a Kawasaki ZX-6R, in this case–calculate the resulting torques that are trying to rotate the swingarm around its pivot. The force diagram in Figure 2 shows that as the suspension is compressed, the three forces move in relation to the swingarm pivot, and while the magnitude of each force does not change, its orientation–and hence the applied torque–does. Figure 3 shows a plot that represents the three torques against the suspension’s travel for a typical sportbike, with a positive value representing a torque that is trying to extend the suspension–antisquat–and a negative value representing pro-squat.

To consider the overall squat tendency, it’s convenient to express the total antisquat in terms of a percentage of the pro-squat weight transfer. In a practical sense, a value of 100 percent means that when you get on the throttle, the antisquat will nicely offset the weight transfer and your suspension will neither compress nor extend–and that applies for any amount of acceleration. A value greater than 100 percent indicates the suspension will extend proportional to the amount of acceleration, and vice versa for values less than 100 percent. Taken to the extreme, zero percent is the point at which there is no antisquat–the suspension is free to compress under any weight transfer. Graphing the antisquat percentage in Figure 4, we see that the overall tendency is toward less antisquat (or, rather, pro-squat) as the suspension is compressed, with a neutral value at approximately 30mm of travel.

Figure 4: Anti-squat expressed as a percentage of the pro-squat due to weight transfer. 100 percent indicates the anti-squat forces nicely offset the weight transfer, and the suspension will neither compress nor extend under acceleration. Note that squat tendency for this ZX-6R is neutral just at the value of suspension travel that corresponds to rider sag.

We know what you’re thinking now–that the farther down you go in the travel, there is pro-squat pulling the suspension down even farther. Isn’t that backward to what you want? In a nutshell, yes–you’d ideally want more antisquat farther down in the suspension travel, and this is one reason why most suspension systems have rising rate built in–to offset the increasing pro-squat. The ideal motorcycle would have either a constant squat tendency for the full suspension travel (a flat line), or a curve that rises the farther into the travel you go. That, however, would require a layout presenting more problems than it would solve–the swingarm pivot would have to be in front of the countershaft sprocket, for one.

At some level of squat, there is an acceptable balance of additional weight on the rear end for traction and sufficient weight on the front end for steering. Keep the amount of squat in that zone and life is good; stray too far in either direction and you’ll be fighting your bike. Knowing the forces involved in a common sportbike layout, we can look at some of the variables that affect antisquat and see how sensitive it is to certain changes.

Figure 5: A long swingarm flattens the anti-squat curve significantly, which broadens the “sweet spot” at which traction can be maximized and lessens the need for a progressive suspension linkage.

Figure 6: An adjustable swingarm pivot makes changing anti-squat possible without affecting ride height. Here, you can see that a small change in pivot height has a large effect compared to changing swingarm angle using ride height.

Figure 5 shows one way to approach the ideal flat antisquat curve–by increasing swingarm length. This is one reason manufacturers work so hard to make swingarm length as long as possible within a given wheelbase. Figure 6 shows what effect raising the swingarm pivot or raising the whole bike on its suspension has. Both change the swingarm angle, a big factor in the amount of antisquat, but you can see that a small change in swingarm pivot height can have the same effect as a drastic ride-height adjustment.

Figure 7: Because chain pull affects anti-squat, a gearing change can make a huge difference to traction and handling. Note that changing to bigger sprockets that have the same gearing ratio has little effect on anti-squat-the greater angle of the chain (which increases anti-squat) is offset by the reduced force (which decreases anti-squat) due to the larger sprocket.

Figure 7 shows the effects of different gearing selection; in general, a smaller front sprocket or larger rear sprocket increases antisquat, but changing sprockets while keeping the same ratio has little overall effect. Note that a minor gearing change can affect antisquat just as much as changing the swingarm angle, and the ramifications of such a change should always be considered, especially when dealing with a powerful bike.