Off road suspension design

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Off road suspension design

For the amateur car designer, there are many tools available today that make designing a car easier. From creating an accurate model of the car and every nut and bolt in it in 3D, to the design and simulation of critical aspects such as the chassis and suspension, software programs have become commonplace to amateur car design. Designing a vehicle is a process that is rarely laid out in books—many books cover parts of design, but not an overall process.

To make it easier for designers, we created a design process for each of the four unique types of car project. This template will enable you to draw out using a computer or pencil, your vision for your car. All of these tools are available as a free download. Parts can be created to exact scale and off-the-shelf parts can often be downloaded from the internet saving you time in creating them. There is a learning curve to solid modeling, but the reward is in the efficiency with which your design can be changed as needed.

Depending on the software, it can provide ballpark to high-precision data about the lift, drag and flow around aerodynamic parts, enabling comparison of parts like wings, spoilers, airdams, etc. CFD can also be used to model the internal flow of air within the body of a vehicle Like through ducts and also to model flows of other fluids like water.

With software with this capability, the software usually handles the setup of the flow problem based on the 2D or 3D model and flow conditions you provide. Some FEA software integrates with solid modeling software, which if you take the additional time to learn the FEA add-on, will enable you to very quickly analyze your vehicle without leaving the modeling software.

Today, these packages model almost every conceivable suspension system. View suspensiuon design software. Other kinematics packages focus more on general physics. View Kinematics software. ProjectLibre open source project management software. Whether working alone or in collaboration with others, having software to help manage tasks is very useful. Race car design and construction involves a lot of tasks in a given order.

Numerous collaboration and task-oriented project management software packages are available, with many being free. OpenOffice Draw, a Microsoft Visio alternative. Software that we thought might be useful goes in this category. General tools to help you day to day and preferably free. The two major freeware office suites that compete with Microsoft are included because they both include a Microsoft Visio-style drawing program in addition to the usual word processor, spreadsheet and presentation software.

View miscellaneous software. Race Car Design Tools. Car driver stencils. FreeCad 3D modeling software.

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EasyCFD flow simulation output of a car. Structural analysis of part in Autodesk FEA. Susprog3D suspension design. CarSim by Mechanical Simulation.A good suspension system is key in any type of automobile, but especially in off-road applications. Whether taking a vehicle through a slow crawl over rocks where wheel travel and articulation is very important, or through the whoops which was our case with Project Storm Trooper.

This project is being built into a prerunner that will eventually be able to hit whoops at high speeds in the desert. We already let the cat out of the bag when we showed you our suspension being installed on the truckbut how did we do it? We will explain what went through our heads in designing the kit and ultimately installing it on the truck. Having a solid plan is just as valuable as the materials being used. Ours centered on making a prerunner, a vehicle that is supposed to replicate an off-road race vehicle and allow teams to pre-run the course with creature comforts.

Prerunners are meant to replicate race vehicles. They can have either I-beams left or A-arms right.

Suspension 101: Pick the Right Setup for Your Ride

Prerunners use A-arms or I-beams to be able to create the type of suspension travel needed to handle the desert. The setup leads to a stance that is undoubtedly recognizable — a wide front end. The wider track width allows for improved dynamic stability. We see it all the time, the guys that only widen the front and leave the rear stock. To truly improve stability, both the front and rear of the vehicle needs to be widened, which will happen for Storm Trooper when we install our Currie Enterprises F9 housing.

For our project, we decided to increase the track width 4. The longer control arms allowed for increased wheel travel as well. We were aiming to get around 17 to 20 inches of wheel travel. The kit that was on the truck cycled 10 inches of travel, which got the job done, but was not where we wanted to be. We also knew that we wanted to run both rod ends and uniballs to increase strength and durability.

We would use Delrin bushings for the lower control arm, while we went with FK Rod Ends for all our spherical bearings and rod ends. The body and race are steel alloy, that has been heat treated, zinc plated, and chromate treated. The uniballs we went with are made up of similar materials. We used the PTFE-lined rod ends on both our upper control arms and our steering. Pictured above are our machined T6 aircraft grade aluminum tie rods.

The quality of the products we would be mating with our fabrication would give us one less thing to worry about while flying through the whoops in the desert.

off road suspension design

All we had left to do was drag out the metal and get to work. A vehicle is only as strong as the materials used in creating it, and even more important with creating components that will see extreme abuse off-road. With all the terms that float around online, we will break down the basics of what you need to know before heading down to the local metal supply yard.

The two biggest names tossed around are mild steel and chromoly. Each has their advantages and a price tag to go along with it. The increased benefits do come at a higher price which can be double the cost of mild steel. Knowing the proper way to use the selected materials will make sure that you do not break anything in the dunes. It can be easily found at all local metal supply yards and in a wide range of thicknesses. When chromoly is MIG welded it compromises the metal properties and will not pass an inspection under most sanctioning bodies.

When it comes down to it you need to select a material that will fit the end goal for the vehicle as well as what will fit in the budget.Most probably there would be a need of 6 Inch play in the wheel and considering the motion ratio of 0.

You can use bike suspension […]. Instructions : Extract the Zip File. With its wheels mounted strangely, […]. 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 […]. 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 […]. 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. We will help you to get products delivered in subsidized rate. Is bike suspension suitable for E Baja vehicle?

Get the latest career updates from Baja Tutor delivered in your mailbox.Last month we started an in-depth look at the benefits and detriments of a four-link suspension. We touched on how a four-link will reduce the number of variables down to just the spring rate and shock valving.

In addition, a four-link is expensive to do right, and this second installment will hopefully take you from the drawing board to the garage floor. There are many different link configuration possibilities, but for this discussion we'll stick to a basic four-link where the upper two links start at the frame and converge at the top center of the rear axle.

The lower two links will also run from the frame to the outer ends of the axletubes. A three-link is similar, but the upper links are replaced by an A-arm with a single joint at the top of the axle. The three-link setup puts that upper axle joint under greater side loads than the upper two links of a four-link, but it is a viable alternative.

Also, suspension builders will argue till the cows come home about what works best, but what we have done is discuss with some of the top desert-race suspension builders how to get you started on a four-link. This design is just a launching pad, and you will need to spend a fair bit of time dialing everything in.

In addition there are many excellent books available to learn more about suspension design. Though some of these books are pretty heavy, they do help explain the theories behind four-link suspensions, but mostly when applied to street cars and not off-road vehicles.

To truly explain a four-link, we would need this entire magazine and a few engineering degrees, and even then there would be things that would be missed. This, however, should be enough to get you started. Just take your time and enjoy the process, because if you don't have the patience to adjust and rebuild your suspension until it works just right, then you should stick to leaf springs.

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The first step in building a four-link involves a tape measure and some graph paper. What you are going to do is figure out the angle of the links and their mounting locations. This will in turn give you an idea of where to start building your four-link.

From there you can fine-tune it. Park the truck on flat ground and measure your wheelbase and the tire size you will be running. Plot the axle centerline points on the bottom half of the graph paper as if you were looking at the side of the truck. Now draw the framerail as it sits above the axle centerlines. This should be where you expect the frame to sit above the axle if you have not yet lifted it.

If you know the height and location of your center of gravity of the sprung weight, plot that as well. If not, estimate it by measuring from the top center bolt of the bellhousing to the ground. You may need to add the height of the expected lift if the truck is still stock.

Now plot a point on the front center of the rear axletube. This will be your lower link mount. Some people mount this above or below the axletube, but we have found that the important part is more the difference in height from the upper-link mount.

Suspension 101: Pick the Right Setup for Your Ride

If your truck is going to be very tall, you may want to put these links on the top of the axletube. To find the upper-link axle-mount point, multiply the tire diameter by 0. Use that number as the distance in inches that the upper link will be above the lower link at the axle. If you were running inch tires, you would want the upper links to be mounted 9 inches above the lower-link mount. You will most likely be mounting the links 8 to 11 inches apart.

The farther apart you can get them right now, the better, as this will help control the leverage of the tires and fight axlewrap. The limiting factor will most likely be the bed of the truck. Continue by plotting the upper- and lower-link axle-mount points.

If this is getting confusing, then you are normal; if it's clear as a bell, you may be a bit too smart for your own good.Through my searches for suspension design book written from an off-road perspective, I've come to the same conclusion as RonGeorge: there aren't many. I thought I would just check and see if anyone had found the holy grail. I did the suspension design on our car for my senior design last year. This year I will be entering Grad school, and would still like to help out with Baja It's just too much fun.

When I did the design last year I went off of intuition and some advise from a Formula guy. Since then I have taken a vehicle dynamics course, but suspension and handling weren't covered very well. I'll check out the books and links that have been suggested.

I can't imagine doing any of this by hand!!! Search, then go buy then entire Carroll Smith Series including the fastners and plumbing, four books total. New Posts. Members Profile. Post Reply. Does anyone know of any good off-road suspension design books? The number of books written properly from an off-road point of view is little. But perhaps there are common threads that carry over from road to off-road.

I have not read this book so I can't give you a review but people like his style of writing, which falls somewhere between reading an ASME Technical Journal and an opinion column in a newspaper.

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For instant gratification, you can watch this Youtube video about suspension basics and alignment and browse through the multitude of suspension arrangements in neat images here. The Carroll Smith books are a good starting point to learn the basic terms for suspension, but Smith was an open-wheel asphalt kind of guy, so most of his caculations don't relate very well to the off-road world.

It is fairly entertaining reading however, as dry technical writing goes anyhow. An old team leader from GT once wrote a short design manual on suspension design, and what you are talking about, I'll see if he'd be willing to post it in the file sharing area for folks to browse through. But I have to disagree with GT Steve on the relevancy of asphalt-centric books to off-road suspensions: Vehicle dynamics are vehicle dynamics no matter what surface you're running on.When it comes to truck suspension, many four wheelers see it only as an instrument to fit the desired tire size they want under their truck.

Once you factor in the limits of the hard parts you are using, the laws of physics will dictate what the final design becomes. The specialized off-road racing vehicles that Craig Hall creates may not look like your truck but they use the same basic suspensions designs found on production vehicles. In its most simple role, your suspension needs to hold your truck up and keep your tires planted on the ground. There are several ways to get that done but each has strengths and weaknesses.

You cannot compare factory suspension designs without talking a little about caster and camber. Caster angle is built into the front suspension so the steering is more stable and will return to center. Camber is the angle of the tire to the road — negative camber is when the tire leans in at the top and in contrast, positive camber is when the tire to leans out at the top, seen below.

Old Faithful, The Solid Axle. A solid axle is just that, an axle that runs from one side of the vehicle to the other. The entire axle moves as the suspension cycles. It is still coveted by hardcore four wheelers. The reason this design has survived for so long is because it does double duty as leaf springs suspend the vehicle and locate the axle.

Attached solidly to the axle with U-bolts, the leaf springs run parallel to the frame. The springs are mounted to a solid perch on one end and a shackle that pivots on the other end. When the axle hits an obstacle, the leaf spring compresses getting flatter and longer, the shackle allows the spring to move without binding. The more they compress, the higher the spring rate rises.

By varying their width, length, arch, thickness and number of leaves, they can suspend anything from a Suzuki Samurai to a cement truck. They work best with a shock that has the necessary damping to control the springs in rebound. Leaf springs are large and they need space to work.

off road suspension design

Some solid axle designs use coil springs instead of leaf springs. The suspension members need to locate the axle while also allowing it to move. The radius arm design uses two arms that run parallel to the frame. A track bar runs from the frame to the axle perpendicular to the radius arms to keep the axle centered on the frame.The off-road truck Sometimes referred to as a "Trophy truck" is a specialized off-road racing vehicle that resembles a pickup truck.

The off-road truck is characterized by a tube frame chassis with a high horsepower engine mounted at the front which drives either the two rear or all four of the wheels. The suspension is built with long travel and is relatively softly sprung to absorb large bumps, dips and jumps the truck travels over at high speeds. The chassis is covered with composite bodywork and usually uses the space normally associated with a pickup truck bed for the storage of spare tires and support equipment. Racing events are held on dirt roads and on desert, wooded, and other natural terrain with the most well known races happening in the Mexico Baja and Africa i.

off road suspension design

The Paris-Dakar. Due to the scratch-built nature of off-road trucks, the designer should be knowledgeable in handling, chassissuspension, powertrain, aerodynamic and safety design. These six major areas of the truck design work as an integrated unit and the designer must have an understanding of how changes to one area affect the others.

Much of the design work is iterative, meaning re-designing areas based on new changes to another area. After the iterations are completed, the design will be complete and optimized. Because of the varied environments where off-road trucks can operate, knowledge of the terrain is important to ensure the vehicle will handle the demands of the surface and speed.

Suspension: Maximizing the contact patch of the tires with good suspension geometry is of key importance. Because of the long suspension travel there can be significant camber change.

Some camber may be of benefit in cornering, but excessive camber will likely mean less traction.

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With a soft independent front suspension, body roll can be controlled through anti-roll bars. Suspension, wheel and tire weights Unsprung weight affect the compliance of the suspension, which in turn affects handling, so keeping all these components as light as possible is an advantage. However, due to the requirement for durability over many miles of rough terrain, it is also difficult in practice. Springs and dampers shock absorber must be matched to the suspension geometry and calculated forces.

Independent suspension a-arm lengths are usually very long mounting almost at the lateral center of the vehicle to minimize camber changes. The suspension pickup point locations impact the chassis design. Chassis : off-road truck chassis are built using spaceframe design to minimize weight and maximize structural rigidity for predictable handling.

Designing torsional rigidity into the chassis will avoid twisting the chassis and any undesirable handling behaviors that result.

Offroad Racing Truck

Powertrain: Weight distribution is heavily impacted by engine position, and both front and mid-engine designs have been created. Intake, Cooling and exhaust need to be considered in relation to chassis design, bodywork and aerodynamics, especially when operating in hot, sandy environments.

Aerodynamic: Gains in the reduction of drag generated by an off-road truck might be significant enough especially on long high-speed stretches to consider shaping of bodywork to reduce drag. Cooling and exhaust might also be incorporated into such a design. If you intend to race under a sanctioning body, always read and understand the regulations of your chosen racing class before designing or building any race vehicle.

Learn the basics about race cars and race car design from our free online knowledge series. Download our free race car design aids to assist you designing your race vehicle. Ensuring the chassis is dimensionally accurate and straight is important as flaws in the structure will create handling issues via misaligned suspension. The use of a solid, flat and level build space is important.

Having sufficient space for the chassis and bodywork construction is important, as a cramped workshop can be difficult to work in. The tools to fabricate the chassis and bodywork can add considerably to the cost of your project if you don't already have a workshop, but borrowing or renting items is also an option.

Many suspension and powertrain components for an amateur-built off-road truck can be sourced as off-road aftermarket parts. This will lower the overall cost. The spaceframe chassis design of these vehicles means their weight is considerably lighter than a production truck.

So for instance, suspension components originally designed for a full-size pickup truck will likely be very durable. Because the off-road truck is scratch-builtthere will be significant effort in design and construction.

The off-road truck has the largest, most detailed chassis of amateur-buildable vehicles and the largest suspension and powertrain.


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