rear twist axle
rear twist axle
(OP)
Can anybody tell what are the key structural compliances/attributes required in the concept design of twist axle.
What modelling tools are typically used to model the compliance/kinematics/stress as I usume Multi body simulation ( linear code) is not the appropriate because of large displacement.Any ideas/suggestions.
What modelling tools are typically used to model the compliance/kinematics/stress as I usume Multi body simulation ( linear code) is not the appropriate because of large displacement.Any ideas/suggestions.





RE: rear twist axle
Although using a linear FE code will give slightly incorrect results, essentially they are linear springs, so you'll get pretty close to the right answer.
Essentially you have two trailing arms connected by a torsional spring, and a bending beam (To give camber stiffness). The torsional properties of sections are fairly easy to calculate, and so is its bending strength.
Having said all that, I wouldn't design one for my own use. The fatigue issues associated with the welding of the beam to the arms are quite serious.
Cheers
Greg Locock
RE: rear twist axle
Do you think longitudinal and lateral compliance is also important for this type of suspension.What is the effect of these characteristics over the ride and handling. In other words what rear kinematic characteristics are most influential on R&H of the vehicle.
RE: rear twist axle
The difference may be negligible or significant, there's no easy answer. It all depends on what you want.
The longitudinal compliance is more of a harshness/road noise requirement, I think R&H mostly just work around it. One obvious problem is that you'll get significant steer if one wheel moves backwards with this type of susepnsion.
Lateral compliance, particularly toe compliance (ie toe per unit lateral force at the contact patch) is very important.
You also need to think about camber compliance and camber in ride and camber in roll.
I don't have set numbers for any of these, I work to vehicle level targets for the understeer budget, and specific manouevres, and some other tests, rather than having rules of thumb for each particular value.
However, basically if the ride and roll steer curves are out then you will have to be very clever elsewhere. Rear suspensions should be quite neutral, I think.
Cheers
Greg Locock
RE: rear twist axle
Due to large geometrical non linearity in the twist or bending of the centre beam do you think the complince should be taken at the maximum wheel travel, as compliaces comes out different at the start of the jounce and at the end of the jounce.
RE: rear twist axle
Camber compliance is the change in camber due to a lateral force at the contact patch.
Camber change in ride and roll is analagous to toe change.
I wouldn't worry about where you measure compliance, it'll only change slightly (I think) with suspension travel.
Cheers
Greg Locock