Scot Costello
02-26-2003, 06:18 PM
Anyone care to comment on my methodology for assessing wheel bearing loading?
Sorry for the long windedness, I can't figure out how to post an image with a website. So I have to describe verbally
GEOMETRY
Using an inboard single row deep groove ball bearing (radial + thrust bearing, pinned support condition) and outboard needle roller (radial only, horizontal roller condition). 50mm bearing centres with hub cantilevered 42mm from centre of outboard bearing.
Wheel offset +53mm and 290mm loaded radius. Gravity loads at wheel act to increase moment at the cantilevered end of the hub on the outside wheel under cornering.
http://www.formularpi.com/upload/wheel_bearing_model.jpg
LOADING
LC1 = maximum static corner weight (1770N)
LC2 = maximum dynamic corner weight (3G cornering)
LC3 = maximum lateral force (3*LC1 acting laterally)
LC4/5 = LC2 +/- LC3 for maximum effect
LC6 = 5*LC1 shock load
OUTCOME
I'm getting some massive dynamic radial loads (in the order of 30kN/bearing under LC4/5) Don't forget that my project isn't FSAE (closer to FVee in scale)
Is there something flawed in my approach/logic?
As it stands based on basic dynamic capacity I am needing bearings with 90-100mm OD (40-40mm bore) which are getting damned heft (like 1.8kg for a single ball bearing!) An OE bearing pack from a WRX only has 27kN basic radial capacity to start with and this is the hub/wheels that I am looking at (granted you're not going to see a WRX at 3g lateral but we are talking about some factors of safety here)
http://www.formularpi.com/upload/wheel_bearing_assy.jpg
TIA
Scot
[This message was edited by Scot Costello on February 26, 2003 at 11:40 PM.]
Sorry for the long windedness, I can't figure out how to post an image with a website. So I have to describe verbally
GEOMETRY
Using an inboard single row deep groove ball bearing (radial + thrust bearing, pinned support condition) and outboard needle roller (radial only, horizontal roller condition). 50mm bearing centres with hub cantilevered 42mm from centre of outboard bearing.
Wheel offset +53mm and 290mm loaded radius. Gravity loads at wheel act to increase moment at the cantilevered end of the hub on the outside wheel under cornering.
http://www.formularpi.com/upload/wheel_bearing_model.jpg
LOADING
LC1 = maximum static corner weight (1770N)
LC2 = maximum dynamic corner weight (3G cornering)
LC3 = maximum lateral force (3*LC1 acting laterally)
LC4/5 = LC2 +/- LC3 for maximum effect
LC6 = 5*LC1 shock load
OUTCOME
I'm getting some massive dynamic radial loads (in the order of 30kN/bearing under LC4/5) Don't forget that my project isn't FSAE (closer to FVee in scale)
Is there something flawed in my approach/logic?
As it stands based on basic dynamic capacity I am needing bearings with 90-100mm OD (40-40mm bore) which are getting damned heft (like 1.8kg for a single ball bearing!) An OE bearing pack from a WRX only has 27kN basic radial capacity to start with and this is the hub/wheels that I am looking at (granted you're not going to see a WRX at 3g lateral but we are talking about some factors of safety here)
http://www.formularpi.com/upload/wheel_bearing_assy.jpg
TIA
Scot
[This message was edited by Scot Costello on February 26, 2003 at 11:40 PM.]