Technical advice please

[TDW]

First off, hi all.

I am looking for a bit of information, I am (as part of some uni work) looking to perform FEA studies on the lower control arm of a push rod suspension system - something I am happy to do all day long. However I need to calculate the loads acting on the arm. Whilst I am happy using the software hand calcs and this sort of stuff has never been my strong point.

Would anyone know just how I would go about this, essentially I am working with a vehicle mass of around 350kg, cornering at 0.5G and braking at 3.75G

Any help would be greatly appreciated - Thanks.

[Lycoming]

Are you having difficulty with calculating load at the contact patch or resolving the loads in the individual arms?

[pwlucas]

First off, hi all.

I am looking for a bit of information, I am (as part of some uni work) looking to perform FEA studies on the lower control arm of a push rod suspension system - something I am happy to do all day long. However I need to calculate the loads acting on the arm. Whilst I am happy using the software hand calcs and this sort of stuff has never been my strong point.

Would anyone know just how I would go about this, essentially I am working with a vehicle mass of around 350kg, cornering at 0.5G and braking at 3.75G

Any help would be greatly appreciated - Thanks.

You should really know how to do the hand calculations before you do any computer analysis. How do you know the values you are using or get are correct? Seems like a common mistake among new engineers.

[Tim.Wright]

Fun fact... the boring (and extremely simple) calcs for finding the boundary conditions is the engineering part.

The software operation for FEA is monkey work which large companies typically farm out to engineering labour camps (I'm not joking).

Draw a f.b.d and do some engineering f.f.s... Its first year statics...

[Tim.Wright]

P.S. Thats a very strange loadcase. How did you come up with that? What is the vertical load which seems to be missing??

If this is FSAE (I'm guessing based on the vehicle mass), braking at nearly 4g seems a bit optimistic to me. Unless this already includes a safety factor. In fact, do you have any idea where these numbers come from? That would be the first clue as to where to start.

[Greg Locock]

Yes, free body diagram is the answer.

As to loads, many track cars and I dare say some road cars have been designed using 3 2 1, that is 3g vertically, 2g longitudinally, and 1g laterally, at the contact patch. Those need to be adjusted to account for the performance of your car, and again for the likely usage. For example, those loads are not high enough if you intend to kerb the car on every lap.

[-Felix-]

well, 350kg seems much too heavy for an FSAE for me. Should be more like >200kg. But if it is, 1.5g lateral and 2g longitudinal would be a more appropriate load case.