PDA

View Full Version : Front Suspension Geometry: A First Try



cputnam
10-06-2008, 03:38 PM
Hey everybody

I'm a senior working with WPI's team. due to the way the previous FSAE teams here were structured, we have very little information to work off of, especially considering few of them have made it to competition. luckily thats changing now.

Since we are starting fresh this year, i'd like to get some feedback on our preliminary suspension design. i've studied the other threasd on this subject from the korean team so i've tried to cover topics already discussed there.

heres some specs first

Proposed Wheel base: 60 inch
Front track width: 48 inch
Rear Track width: 46 inch
Front suspension: SLA
Proposed Rear suspension: 4 link with solid axle
Wheel Size: 13 inch
Tire Radius: 20 inch
Ground clearance: >1.25 at full bounce

Steering geometry has not yet been added

here are the front suspension drawings so far.

Static
http://i486.photobucket.com/albums/rr222/cputnam58/suspension%20design/suspv2staticdrawing.jpg

1.25 inch bounce
http://i486.photobucket.com/albums/rr222/cputnam58/suspension%20design/suspv2125inchbounce.jpg

1.25 inch rebound
http://i486.photobucket.com/albums/rr222/cputnam58/suspension%20design/suspv2125inchrebound.jpg

2 degrees roll
http://i486.photobucket.com/albums/rr222/cputnam58/suspension%20design/suspv22degreerolldrawing.jpg

I put this together last night so its by no means final. just looking to get some ideas on specific things to focus on as we progress through iterations.

With the design we are going for, we are attempting something light in the rear with the ability to lift the inside rear tire in a turn. this is the main reason for the 2 inch difference in track width. One idea we are also pursuing to further this is to set up the front suspension for anti-squat, which could help the front end dive in a turn and further un-weight the rear. any other suggestions as to how to increase the ability to lift the rear tires?

Thanks for the help

cputnam
10-06-2008, 03:38 PM
Hey everybody

I'm a senior working with WPI's team. due to the way the previous FSAE teams here were structured, we have very little information to work off of, especially considering few of them have made it to competition. luckily thats changing now.

Since we are starting fresh this year, i'd like to get some feedback on our preliminary suspension design. i've studied the other threasd on this subject from the korean team so i've tried to cover topics already discussed there.

heres some specs first

Proposed Wheel base: 60 inch
Front track width: 48 inch
Rear Track width: 46 inch
Front suspension: SLA
Proposed Rear suspension: 4 link with solid axle
Wheel Size: 13 inch
Tire Radius: 20 inch
Ground clearance: >1.25 at full bounce

Steering geometry has not yet been added

here are the front suspension drawings so far.

Static
http://i486.photobucket.com/albums/rr222/cputnam58/suspension%20design/suspv2staticdrawing.jpg

1.25 inch bounce
http://i486.photobucket.com/albums/rr222/cputnam58/suspension%20design/suspv2125inchbounce.jpg

1.25 inch rebound
http://i486.photobucket.com/albums/rr222/cputnam58/suspension%20design/suspv2125inchrebound.jpg

2 degrees roll
http://i486.photobucket.com/albums/rr222/cputnam58/suspension%20design/suspv22degreerolldrawing.jpg

I put this together last night so its by no means final. just looking to get some ideas on specific things to focus on as we progress through iterations.

With the design we are going for, we are attempting something light in the rear with the ability to lift the inside rear tire in a turn. this is the main reason for the 2 inch difference in track width. One idea we are also pursuing to further this is to set up the front suspension for anti-squat, which could help the front end dive in a turn and further un-weight the rear. any other suggestions as to how to increase the ability to lift the rear tires?

Thanks for the help

cmeissen
10-06-2008, 04:16 PM
A lot of caster and a long spindle length in the front will also transfer weight off of the inside rear and outside front when turning. Making caster easily adjustable would be an easy way to adjust this affect.

cwojcik
10-08-2008, 08:27 AM
Won't lots of caster and scrub radius require a lot of steering effort?

J.R.
10-08-2008, 11:02 AM
You can offset the caster line to go behind the wheel center. Mechanical trail increases steering effort, not caster alone.