Cad Software

[Joel]

Can anyone recommend some CAD software, that's readily available and falls within the usual Hoodie tight budget?

 

It needs to have the cababilty to specify wall thickness of materials and preferably show stress areas and the like - I'm thinking chassis design here.

 

I used SDRC Ideas many moons ago at uni, but I don't know if that's available to home users, and has probably long since been superceeded anyway.

 

Cheers,

Joel.

[Guest salty_monk]

I have AutoCAD 2002. Limited 3D though. I have an untested copy of Solidworks somewhere, must get around to testing it.....

 

Dan

[Snapperpaul]

Next time i am in Kosovo i will pick up AutoCad, i think it was 25€ last time i looked

[Guest Toejam]

Your looking at one of the more expensive packages to show stress analysis on parts. I've never done it personally, but it's not going to be easy I expect.

 

SDRC is mainly for surface modeling / rapid prototyping etc I think. I'd look to get Solidworks / Pro E or an advanced copy of Auto CAD (Inventor with mech desktop etc. I think might do it).

 

None of the above are cheap though !

[Swan Jnr]

sketch up from google is free, though it wont do the stress stuff. easy to use, 3d package, loads of support on the net.

loads of examples too. i had a play qwith it and its fairly easy to put a chassis of sorst together in a couple of nights.

 

for stress maybe it would be worth showing the plans to a chassis builder for his opinion, for a real world thought on it?

 

paul

[Guest Dan_Beeston]

Hey Buddy,

 

I've done some stress analysis using ProE/ProMechanica (got a copy around here somewhere), but it's a hell of a learning curve to get anything meaningful out of it! (especially the FEA stress stuff)

 

AutoCad or TurboCad can knock up pretty decent technical drawings (got both of them somewhere too!), but a bit of common sense is much easier to apply when working out whether a chassis is up to the stresses or not

 

A top-flight racecar chassis would not be designed without being fully FEA analysed, but you can bet none of the RH chassis ever were (or most other kit manufacturers either)

[Guest Paul Morgan]

Just downloaded Sketch up, looks Ok for a freebie.

 

Paul

[Joel]

I just stumbled across this website - the guy has designed from scratch a spaceframe chassis for a Morris Minor Race car. It's hugely impressive if you have time to go through all the pages

 

http://www.beardmorebros.co.uk/website%20p...assis_page1.htm

[richyb66]

Can anyone recommend some CAD software, that's readily available and falls within the usual Hoodie tight budget?

 

It needs to have the cababilty to specify wall thickness of materials and preferably show stress areas and the like - I'm thinking chassis design here.

 

I used SDRC Ideas many moons ago at uni, but I don't know if that's available to home users, and has probably long since been superceeded anyway.

 

Cheers,

Joel.

 

Got CATIA V5 on my laptop (purely for evaluation purposes), but it's what we use at work and is more than up to the job for design although I've never used the FAE side of it and don't know of anyone that does. Decent FEA packages are expensive and take ages to run due to complex maths involved in the calculations.

[andyparry]

I personally use Pro Engineer Wildfire 3 at work. It is probably the best CAD package out there for 3D design, but complex to use. Ironically, PTC the manufacturers give away a free eductaional version, which is identical to the full version, except that all drawings have 'educational version' across them which you can't remove, and you can't export , import or open files from the full version. It does however have the complete sheetmetal and Pro-Mechanica package included. However, I've done a 3 year mech eng degree, I've done the Mechanica training course, and I very much doubt that unless you have those two under your belt, that the results you come up with will bear anything close to reality. I struggle to use it as it is very complex. It's like doing ten page of calculus; you may have an answer, but it is probably wrong, and for a chassis, I wouldn't trust my own analysis! I personally would have to get one of the analysis team at work to verify the results.

 

The long and short of it is, don't bother!! If it were that easy, highly educated highly paid stress analysis engineers would be out of a job!

 

HTH

 

AP

[richyb66]

I personally use Pro Engineer Wildfire 3 at work. It is probably the best CAD package out there for 3D design

 

That's fighting talk that is - CATIA V5 is clearly better!!! Pro E is just a colour version of etch-a-sketch.

[Guest timswait]

Half the problem with the stress analysis is knowing what loads to apply to the model. For cornering and bump forces the suspension mounts act as the restraints, but the loads are applied by every part of the car as inertia. Trying to model crash behaviour is next to hopeless as you're looking at non-linear deformation and buckling of the space frame (I assume your thinking about a spaceframe?).

Having said there is something to be gained from designing it in 3D in CAD first. You get a good feel for the way the parts will fit together, often when you make something you look at what you've made and think "I should have done that differently, why didn't I think of that?" At least with CAD you can see it in 3D and see some of those points before you start cutting metal. I'm designing a pedal box for my car with Pro Engineer because it's a complicated area with the steering column, firewall, pedals and master cylinder to worry about, and I think my chances of getting it all to fit together first time would be pretty slim without designing it in CAD first.

There's probably also something to be gained from using the stress analysis tools provided you don't put undue faith in the results. If you constrain the rear suspension points and put a twisting moment on the front points you can get an idea of your design's stiffness in torsion, which is critical for handling. (torsional stiffness of the chassis should be at least ten times the stiffness of the suspension in roll) Also you can get a feel for which areas of the chassis are deforming more than others, so get an idea where to beef up.

There's a good book on spaceframe chassis design by Costin (the 'cos' in either Cosworth or Marcos, they were brothers, I can't remember which one wrote the book). It's quite old, it was written in the 60s, but for designing a steel spaceframe is gives good rules of thumb which haven't changed.

[Guest Ad_W2001]

I use ProE, but as mentioned above, without background knowledege of FE work and stress/strain calcs etc etc theres not much point. I have the educational version of ProE, which isnt free unfortunately, but its far far cheaper than the retail version. Paid £75 for it, which for the full program is damn good in my opinion. Maybe you could get it through a kid/friends kid whos at uni? Linky for all your cheap software but to purchase stuff you will need a valid student ID card to email a scan to them.

[Guest wildejon]

I use ProE, Catia, Solidworks, Solid Edge, Inventor, Unigraphics and Spaceclaim at work

I can safely say, none of them are the best! They all have the cool things they can do, depends exactly what you need it for really. Inventor, SW, SE and Spaceclaim are easier to pick up and run with I think but they don't have the functionality of the other two. Then again, I doubt anyone really ever uses everything the packages can do!

 

You ought to check out spaceclaim for knock up models quickly. Its being developed by the guys behind ProE. They are aiming for a non history based product, easy to use etc.

 

Not sure about FEA packages on the cheap. I've used a few but they were all really expensive!!