The answer will vary widely depending on the type of suspension used and the specific details of its implementation in the vehicle in question.
By the way, a 6 inch high step bump encountered in normal street driving is HUGE. Tire-blowingly and rim-bendingly huge. Driving-straight-into-a-kerb huge. Many, perhaps most, cars don't even have 6 inches of total suspension travel available in compression (measured from static ride height). Many don't have 6 inches of ground clearance underneath to the chassis.
Repeat question, with more information provided and with more plausible circumstances.
A watts link with the ends at the body might not experience significant roll centre migration in those circumstances, and I suppose one could arrange a short long arm setup to get close. But... why would you want to?
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
We are using double wish bone for Baja SAE 2014 event..can you help with some geometry like the change of roll center for 6" bump?and what is the difference between symmetrical and Asymmetrical bump?
Longer arms will give less instant center movement. If you make a scale drawing of the basic suspension elements, you can work out where the instant centers are.
A question that you need to ask yourself, is whether the migration of the instant centers is a relevant issue, and why.
Suspension designs that give relatively little or no instant center migration: Pure trailing arms, double trailing arms (traditional air-cooled VW front suspension), twist-beam axle as seen on the rear of many cheaper front-drive cars, solid beam axle with appropriate locating linkage, Ford Twin-I-Beam. If you are fixated on minimizing roll center migration, ask yourself why variations of multi-link and MacPherson strut have almost entirely replaced these types of suspensions in just about all performance cars and trucks (granting that trucks generally use solid rear axle for other reasons), and why those types of suspension designs are not used in the front of professional off-road race trucks (Baja, CORR, etc), despite multi-link and MacPherson generally having much greater variation of instant center height with suspension movement.
Can anyone say the point to mount our Fox suspension with respect to the Motion ratio of 6inch bump and 4"fox compression? How to determine the mounting point on A-armand the mounting angle?
Come on! Get up and sit down with your CAD system and start doing some engineering! You want the folks on an internet forum to design this competition vehicle for you. I think that it is time for your group to start doing some thinking and designing on your own.
"A3.6 Violations of Intent -
The violations of the intent of a rule will be considered a violation of the rule itself. Questions about the intent or
meaning of a rule may be addressed to the Baja SAE rules committee, Technical Inspectors or SAE staff."
"A6.1 Student Created
The vehicle and associated documentation must be conceived, designed and fabricated by the team members without
direct involvement from the professional engineers, faculty or professionals in the off-road and racing communities.
ARTICLE 4: INDIVIDUAL PARTICIPATION REQUIREMENTS
A4.1 Eligibility Limits
Eligibility is limited to undergraduate and graduate students to ensure this is an engineering competition rather than a
race. Individual members of teams participating in this competition must satisfy the following requirements:
A4.2 Student Status
Team members must be enrolled as degree seeking undergraduate or graduate student in a college or university. Team
members who have graduated during the last seven (7) month period prior to the competition remain eligible to
participate.
"In brief – Faculty Advisors may not design, build or repair any part of the vehicle."
