1/4 Scale R/C F1 about the upright

Here are our CFD links and discussions about aerodynamics, suspension, driver safety and tyres. Please stick to F1 on this forum.
firasf1dream
4
Joined: 18 Apr 2014, 21:26

Re: 1/4 Scale R/C F1 about the upright

Post

ChrisDanger wrote:Ah, right. That's hard to explain. It may be best to imagine you're sitting at the corner of the car holding the axle with a bearing in each hand (for a two-bearing hub). So I suppose you are the hub, and for now ignore the suspension and imagine you're fixed to the car. Now, with the car stationary, you have to only support the weight. You will have to apply a moment on the axle by applying radial forces on each bearing. There should be examples in Shigley of this type of arrangement, where the wheel is effectively applying a vertical force at the end of the axle equal to the weight at that corner. If you accelerate, and you're at a rear corner, you will have a radial force pushing the axle forwards, so the force on the bearing will still be radial but more horizontal now. Under braking this force will be radially backwards. Under lateral acceleration (i.e. cornering) you'll see some axial force as your tires push the car sideways and this force is transmitted by pushing the axle along its length, but also the radial forces will change too as the weight effectively changes.

Let me know if that helps.
thank you Chris for this nice explanation, so we can say the radial is due to weight or weight transfer and the axial is a force that sort of try to push the bearing out of the axial ?

and about axial it's just created on the corners ?

ChrisDanger
26
Joined: 30 Mar 2011, 09:59

Re: 1/4 Scale R/C F1 about the upright

Post

Yes, also any longitudinal acceleration will be transmitted via axial loads.

This is a simplified view though. Forces will spill over slightly when you factor in that the wheel +tire is not a rigid body, the tire forces are acting off the axles axis, and that the hub is moving in quite a complex manner with the suspension along a generally bumpy road surface.

firasf1dream
4
Joined: 18 Apr 2014, 21:26

Re: 1/4 Scale R/C F1 about the upright

Post

ChrisDanger wrote: This is a simplified view though. Forces will spill over slightly when you factor in that the wheel +tire is not a rigid body, the tire forces are acting off the axles axis, and that the hub is moving in quite a complex manner with the suspension along a generally bumpy road surface.


what do you mean by this :/ ?

ChrisDanger
26
Joined: 30 Mar 2011, 09:59

Re: 1/4 Scale R/C F1 about the upright

Post

Just that the forces are mostly in the directions I mentioned. This would be true if the everything was perfectly aligned with the principle planes, but a small amount of axial force will be present where you might expect only radial forces. This imperfect alignment may arise from static setup or changes due to suspension travel (like toe/camber etc.).

For example, camber would introduce an axial component of the weight force, and toe would for longitudinal acceleration.

firasf1dream
4
Joined: 18 Apr 2014, 21:26

Re: 1/4 Scale R/C F1 about the upright

Post

ChrisDanger wrote:Just that the forces are mostly in the directions I mentioned. This would be true if the everything was perfectly aligned with the principle planes, but a small amount of axial force will be present where you might expect only radial forces. This imperfect alignment may arise from static setup or changes due to suspension travel (like toe/camber etc.).

For example, camber would introduce an axial component of the weight force, and toe would for longitudinal acceleration.
ah ok, yes the change of camber and toe would introduce more stress on the connections
thank you Chris :)

ChrisDanger
26
Joined: 30 Mar 2011, 09:59

Re: 1/4 Scale R/C F1 about the upright

Post

It's more the direction of the force on the axle. The weight force would be vertical, but since camber offsets the axle from horizontal, if you decompose the vertical weight force into axial and radial components there will be a small axial component of this force, but the radial force will get smaller. (If you draw a free body diagram of the axle in this scenario you should see this.)

firasf1dream
4
Joined: 18 Apr 2014, 21:26

Re: 1/4 Scale R/C F1 about the upright

Post

ChrisDanger wrote:It's more the direction of the force on the axle. The weight force would be vertical, but since camber offsets the axle from horizontal, if you decompose the vertical weight force into axial and radial components there will be a small axial component of this force, but the radial force will get smaller. (If you draw a free body diagram of the axle in this scenario you should see this.)
ok Chris thank you will try it in a solidworks sketch block and move it around to see how it is affected, i will draw 2 forces perpendicular and see how it will be changed while i change the camber