This paper addresses the design of a fourlink rear suspension for a drag racing motorcycle to provide anti squat, which increases rear tire traction, thereby improving vehicle acceleration performance. The suspension system is a device connecting the body with wheels. At the cad model was analyzed parameters as roll center, suspension sizes arms, scrub radius, anti squat, anti. Antisquat is the suspensions mechanical resistance to compression due to forces from the engine. The drastic increase in anti squat was caused by the installation of a ladderstyle anti wrap bar. Apr 28, 2010 if you design the suspension around the middle ring your are going to have too much anti squat and too much pedal kickback in the granny. Design and analysis of suspension system for an all terrain vehicle shijil p, albin vargheese, aswin devasia, christin joseph, josin jacob abstract in this paper our work was to study the static and dynamic parameter of the suspension system of an atv by determining and analyzing the dynamics of the vehicle when driving on an off road racetrack. Antisquat and antipitch geomatry vehicle dynamics engineering. I think the point of the article is to make it simple because anti squat is a term that gets thrown around, but is seldom quantified, kind of like that bike feels balanced or the short. Squat is a term used to refer to the amount the car tips backwards under acceleration.
Free body diagram for calculating antisquat of independent rear suspension. Motorcycle rear suspension worcester polytechnic institute. For anyone interested in analysing alternative front ends we have some stand alone software which may be of interest. Aug 03, 2017 the 2play suspension design works as a system. Sag can go from 25% to 35% when you are climbing, so as can go from 100% 3218 25% sag to 120% 2232 35% sag instead of going to 150. Jul 15, 2019 this anti dive is the exact opposite of anti squat. Anti squat is a term for suspension engineers to determine how much the suspension mechanism itself is resisting suspension compression. Putting closer to 80% in the car will still provide minimal movement to acquire most of the benefits of having the geometry but will also provide the driver with the feedback they need. Design and optimization of formula sae suspension system.
Suspension design theory and antisquat behavior arts slo. A rear suspension aft lateral link was selected for ssat model validation lu et al. One of the most common questions we get about suspension setup and tuning is how 4link geometry affects the performance and handling of a vehicle. Effects of anti squat antisquat as can limit the amount of compression in. Outline in chapter 2, the background information which is necessary to develop a suspension is provided. As sportbikes become more and more powerful, rearend geometry plays a greater part in determining how well that power gets to the ground. Pdf the focus of the paper is on designing a suspension system for a medium downforce small. Ideally, the anti squat value would increase as the suspension travel increases, giving the suspension additional anti bottoming resistance as it approaches maximum stroke. Geometric design of independent suspension linkages deep blue. Anti squat suspensions are used to reduce body squat by altering the rear suspension so that the forces resulting from accelerating pass through the control arms and suspension. Anti dive is a suspension parameter that affects the amount of suspension deflection when the brakes are applied. Discussion paper effect of antisquat adjustment in solid. The fsrte02 chassis and suspension design had to be feasible, makeable and completely finished.
Pdf influence of antidive and antisquat geometry in combined. The vehicle model is employed to study the effect of these features upon combined bounce. This extra extension can be used to counteract that extra vertical load. Chassis and suspension design fsrte02 materials technology. From my discussions with a couple of engineers who work at certain companies, the combo of a wide range cassette on the back and the extra freedom of design allowed by being 1x exclusive means that for longer travel am bikes norco range, santa cruz nomad you actually have a wider anti squat range for 1x11 than you would for 2x10. Over 100% of anti squat as means suspension will extend under acceleration.
Jul 01, 2000 anti squat is a transient vehicle suspension parameter which can dramatically affect tractive effort available at the motorcycle drive tire. Evaluate designs and select the three best candidates. Abstract the paper explains design methodology and flow in a suspension is one of the most vital subsystems of an automobile. What is anti squat and pedal kickback pole bicycles. If the inner hingepins are flat parallel to the ground or have no angle, then the vehicle has zero degrees of anti squat. Simulation of effect of suspension geometry on rollover, squat and. The calculation of anti squat is similar to that of anti dive.
The 4link calculator lets you input, view, save, analyze and compare your 4link rear suspension geometry. Unfortunately, this is not the case, and due to the changes in geometry as the suspension compresses, the anti squat angle and percentage typically decrease as suspension. Calculate antidive, antilift, and antisquat percentages for inboard brakes, outboard brakes, independent suspension, and solid axle suspension. So, continuing the topic today i would be writing about how to design effectively suspension systems so that you could probably get out the desired performance of the vehicle. When we tune anti squat, we refer to the angle of the inner hingepin as it relates to the ground. Now anti squat is perhaps the most bandiedabout term in mountain bike suspension. Anti squat is only one of many considerations that goes into a suspension design, a point i tried to make in my answer of how to design as in a frame. Analysis of pedal efficiency antisquat analysis of progressivity leverage ratio analysis of braking antirise analysis of axlepath, kickback and chaingrowth 5 graphs for antisquat, antirise, chaingrowth, axle path and leverage ratio.
Anti squat is the reaction of the rear suspension to the chain force. Design, analysis and optimization of suspension system for an. Through video motion analysis of a prototype vehicle before and after the proposed design. At initial condition 0 mm bump travel the value of anti squat is 50%. May 29, 2017 whenever accelerated, vehicle has the tendency to pitch up i. Jan 27, 2005 related to trailing arm design is the link setup, and squat vs anti squat.
This does not infer that there is little or no weight transfer to the back wheels. The same logic goes for anti squat as anti dive and some. The basics of anti squat, anti dive, and roll center. Design, analysis and optimization of suspension system for an off road car. Jul 29, 2015 anti squat suspensions are used to reduce body squat by altering the rear suspension so that the forces resulting from accelerating pass through the control arms and suspension linkage rather than. This means when power is applied to the rear suspension, the force of the engine is being applied to the links instead of the body of the car. Does the usual rule that limits the available anti squat in a i. This means that the design of the suspension plays a role, but also the position and direction of the chain. The main reason for the difference is due to the different design goals between front and rear suspension, whereas suspension is usually symmetrical between the left and right of the vehicle.
Under 100% as means tendency to compress under acceleration. On the beneficial effects of antisquat in rear suspension. Suspension debate about antisquat ridemonkey forums. The vehicle model is employed to study the effect of these features upon. Addressing anti squat and using it to improve suspension design is now a. Antisquat does not change the steady state value of the force at the tyre contact patches during acceleration. S197 mustang, instant center, anti squat, suspension. With 100% as suspension wont neither extend nor compress. Design of a suspension system and determining suspension parameters of a medium downforce small formula type car article pdf available in matec web of conferences 124. In this paragraph calculations will be made for the suspension ratios, the corresponding. When building a 4link suspension, the lengths of the links, their positioning, and the angles at which they are mounted, will all determine how the suspension affects the vehicle chassis under acceleration, braking, and cornering.
Rear suspension that features anti squat geometry optimizes a cars ability to apply acceleration force to the road surface. Volume 1 suspension optimization of student formula race car. That is, if the instant centre of the rear suspension lies anywhere on this line, the car will have 100percent antisquat. It happens because of change in inertia, in a similar fashion that pushes us into the seats when we accelerate. Anti squat is a characteristic that can be designed into a suspension to counteract the natural squat forces. The vehicle suspension geometry showed excessive anti squat and very low antidive properties. When this force is applied through suspension with 100% or greater anti squat geometry the rear of a car pushes up rather than squatting down under power. Part of the reason for the bugyfication is to help the fj climb better last year, it was hampered by too much rear weight, but alot of it was too much anti squat in the suspension, and the resulting hop. Antisquat is suspensions mechanical resistance to compression due to forces from the engine when on a bicycle human is the engine. By raising the front of the hingepin or lowering the rear, you are increasing the degrees of anti squat.
When designing the geometry, it is important to keep in mind that designing is an iterative process and that compromises will be inevitable. Design of a suspension system and determining suspension. May, 2016 intuitive explanation of anti squat with real demos and examples. An anti squat of 0% means that chain plays no role in preventing bob in the suspension. To provide isolation from high frequency vibration from. Over 100% of antisquat as means suspension will extend under. Design and development of the ure06 rear suspension. So, today we are going to cover one of its aspects that are anti squat and anti dive geometry or if combined then called anti pitching geometry. When designing the suspension of an outboardbraked front wheel, designers establish this brake dive behavior by choosing the antidive coefficient 30.
The advanced inputs for this calculation instant center positions and cg height can be easily calculated using the calculations in speedwiz. Design, analysis and fabrication of rear suspension system. If the anti squat percentage is more than 100, it means that the drive force is greater and will actually extend the rear wheel outwards and unload the shock. All kinds of forces and movements between the wheels and the ground passes to the body through the suspension. Is this by design, or just a result of that much power.
Determine suspension system requirements and specifications. Bearings are pressed into the frame and then the linkage presses tightly into the bearings from both sides. Leaving the 3 vs 4 links out of the picture i notice a lot of the trucks tend to lift the front end under throttle. Why dave weagles mtb suspension designs are so prolific. Definition of anti squat automotive suspension engineering. Computer program to simulate and analyze rear suspension 4link setups for instant center, pinion angle and driveshaft angle change, anti squat %, and more for drag racing.
In order to measure your anti geometry, the side view swing arm for your front and rear suspension systems must first be established. This will calculate numerous parameters such as anti dive, rake and trail variation etc, etc. The suspension system comprises antisquat and anti dive element. Therefore it is often best to design some squat and some dive back into the suspension system and not run 100% anti geometry unless the aero dynamics dictate so. Understanding mtb suspension a comprehensive guide to. Thus, traction is directly controlled through adjustments to the suspension system. These parameters were considerably improved by simple. This paper addresses the design of a fourlink rear suspension for a drag racing motorcycle to provide anti squat, which increases rear tire traction, thereby improving vehicle acceleration. Anti squat, dive and lift geometry suspension secrets. Camber angle, toe angle, tyreroad contact point motion, anti squat percentage, anti rise percentage. The upper chainline is key in the design of suspension. The forces are just applied in the opposite direction since its on the front end of the vehicle and happens during deceleration.
Pdf design of a suspension system and determining suspension. Just like anti dive in the front suspension, there can be anti lift in the rear suspension that reduces rebound travel under braking. This is effected by the suspension geometry and its relation to the cog center of gravity. Design and manufacture of an adaptive suspension system. So while the alloy frame members appear a touch on the wispy side, lateral stiffness is impressive. The suspension geometry was obtained by using instantaneous centre method so as to have minimum plunging of shafts. The suspension system comprises antisquat and antidive element. Derailleur shifting is the standard on todays bikes and all gear combinations have. The method presented here graphical method for anti squat is not valid in some specific bikes, such as bikes where the. The rear suspension, anti squat and attitude calculations will still apply. If the as curve is not flat you can compensate the change in the gears. In this article well cover what we consider to be the three most important elements. Anti dive and anti squat they can be thought of as the counterparts for braking and acceleration as roll center height is to cornering. Raising the anti squat percentage above 100% means that we extend the suspension slightly with the extra anti squat force.
681 1322 923 1202 113 206 1051 316 1425 906 525 209 22 1619 1156 767 462 1181 1088 769 1263 1342 120 1371 8 893 285 1308 121 769 1391 1216 19 1251 858 248 390 54