Free SLA Suspension Kinematics Program

[Sage M. Wolfe]

I haven't done FSAE (I'm involved with a different project), but last year I wrote an SLA suspension kinematics program that I thought might be helpful for some FSAE (or SAE Baja) teams. It's free, under the GNU Public License.

Unfortunately, I do not have a place to host the file. Zipped, with the user's guide, it's only 185 kb. If anyone wants a copy, send me an email. If anyone is willing to host it, that would be even better.

Now, if you already use Lotus or ADAMS or something, this program is not for you. It's not nearly that powerful. It's pretty simplistic, it only calculates parameters for a quarter of the car, and only for SLA suspensions. This program is designed for someone who knows the very basics of MATLAB and nothing else. Of course, you need some vehicle dynamics knowledge to make use of the results. It might be helpful, it might be a pain in your ass, I just thought I would offer it up in case anyone is interested.

Program inputs (all at ride height):
- Upper A-arm ball joint locations
- Lower A-arm ball joint locations
- Wheel center & middle of tire @ ground plane locations
- Tie rod inner & outer ball joint locations
- Suspension travel
- Brake bias
- Brake type (inboard or outboard)
- Suspension type (front or rear)
- Wheelbase length
- CG height
(The last 5 are only used for calculating anti- features, assuming rear drive)

Program outputs:
Scalars
- Caster angle
- (Mechanical) Trail
- Kingpin angle
- Scrub
- Spindle length
Plots
- Suspension position throughout travel (front view)
- Suspension positions in jounce (3D view)
- Camber curve
- Bump steer curve
- Roll center height (assumes symmetric jounce/rebound)
- Roll center location during cornering (assumes opposite motion on opposite side of car)
- Front anti-dive (if applicable)
- Rear anti-squat (if applicable)
- Rear anti-lift (if applicable)

The kinematics are calculated numerically. I believe the errors in calculated positions to be on the order of a few thousandths, but the precision can be adjusted by the user.

If you try it out, feel free to post your comments & such here. Don't worry, I won't be offended if you say it sucks.

[Sage M. Wolfe]

I haven't done FSAE (I'm involved with a different project), but last year I wrote an SLA suspension kinematics program that I thought might be helpful for some FSAE (or SAE Baja) teams. It's free, under the GNU Public License.

Unfortunately, I do not have a place to host the file. Zipped, with the user's guide, it's only 185 kb. If anyone wants a copy, send me an email. If anyone is willing to host it, that would be even better.

Now, if you already use Lotus or ADAMS or something, this program is not for you. It's not nearly that powerful. It's pretty simplistic, it only calculates parameters for a quarter of the car, and only for SLA suspensions. This program is designed for someone who knows the very basics of MATLAB and nothing else. Of course, you need some vehicle dynamics knowledge to make use of the results. It might be helpful, it might be a pain in your ass, I just thought I would offer it up in case anyone is interested.

Program inputs (all at ride height):
- Upper A-arm ball joint locations
- Lower A-arm ball joint locations
- Wheel center & middle of tire @ ground plane locations
- Tie rod inner & outer ball joint locations
- Suspension travel
- Brake bias
- Brake type (inboard or outboard)
- Suspension type (front or rear)
- Wheelbase length
- CG height
(The last 5 are only used for calculating anti- features, assuming rear drive)

Program outputs:
Scalars
- Caster angle
- (Mechanical) Trail
- Kingpin angle
- Scrub
- Spindle length
Plots
- Suspension position throughout travel (front view)
- Suspension positions in jounce (3D view)
- Camber curve
- Bump steer curve
- Roll center height (assumes symmetric jounce/rebound)
- Roll center location during cornering (assumes opposite motion on opposite side of car)
- Front anti-dive (if applicable)
- Rear anti-squat (if applicable)
- Rear anti-lift (if applicable)

The kinematics are calculated numerically. I believe the errors in calculated positions to be on the order of a few thousandths, but the precision can be adjusted by the user.

If you try it out, feel free to post your comments & such here. Don't worry, I won't be offended if you say it sucks.

[OspreysGoSWOOP]

I'll host it.

Send me a private message with your email address and I'll reply with instructions.

Always willing to help a fellow open source advocate and FSAEer