How far can design progress beyond aesthetic w/out materials? 4

[Silito]

In developing something so multi material intensive as go-carts and other limited capability recreational vehicles, how far can the design process progress beyond meer aesthetics before the need of a prototype becomes completely necessary to proceed? Can rough designs for the engine, chassis and other components be at least somewhat realized without the phsical materials (if only the designers are available and not the facilities initially?)

Thanks so much for everyone's time.

 

[TVP]

Silito,

Detailed design is performed every day on complex items like automobiles, airplanes, military vehicles, etc. using intuition, past experience, advanced computer simulation (finite element analysis, computational fluid dynamics, etc.), and 3D computer modeling, without having physical prototypes. Of course prototypes are useful and will always serve a purpose in proper engineering design and development, but they are not required to create initial designs beyond mere aesthetics. Engineers with the proper background, experience, and tools can create "rough" designs for your proposed vehicles.

 

[NickE]

Personally, as a Met/Mat Engineer, who is also involved in automotive R&D; I think that material considerations should be considered from the get-go...


As far as design, I would say that I wouldn't even try to build a prototype without complete models on the computer. Heck modern 3-D packages such as Catia/UniG/Etc... will allow you to completely design each individual component, perform simple functional testing, probably allow tolerance stackups to be figured, allow the designer to check for maintenance interference issues, and provide bodies for Raytraced sales images... So theroetically the entire vehicle could be designed and tested on the computer before Part1 is made.

I also think that anyone who is generating custom componentry such as engines/transmissions should probably protoype and test very completely.

Of course there are thousands upon thousands of variations that you could implement, focus is key here, dont get too caught up in the trees, otherwise you'll get lost in the forest.

I would use as much off the shelf (grainger/McMaster/etc..) componentry as I could. Taking something from Idea to Product that Works can be very $$ and time consuming.

I would also have real engineers working with the design team, the most beautiful design isn't going to work if its unmanufacturable.

Then of course you have to consider quantity, how many per year are you expecting to sell? If each is custom then there is a definate limit to how many can be made. If you want to make 1,000,000 a year though there is a whole new world of things to consider: process, assembly, and supply become very important.

What sort of defect rate do you expect to hold? 100ppm is generally OK for automotive, but not easy in any way shape or form.

good luck

Nick
I love materials science!

 

[Silito]

Honestly, I really appreciate your posts, they were extremely infomative, thanks so very much for spending the time to reply in detail.

 

[GregLocock]

It depends a little on what you want from the final product - for instance it is still quite difficult to trade off rough road durability vs light weight. If you can afford a few extra kg then a robust design won't need prototyping.

By the time OEMs build prototype cars they will already have a good handle on performance, handling, ulitmate grip, aero, durability, crash, noise, ease of manufacture, and so on from their computer models. There are some things that cannot be predicted accurately of course, which is one of the reasons why prototypes are still necessary.

However in terms of cost and speed it is a good idea to build an early prototype to prove out the mechanicals, and then a later one.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[DKirkham]

I would not even consider making a go cart (let alone an engine or just about anything else) without COMPLETE, DETAILED CAD drawings. With good software, you can see interferences, clearances, and all sorts of other things you will never foresee if you just start building something.

When we made this car, we had COMPLETE CAD drawings. We would have sunk without them.

Then, as you go further down the road on the build and want to change things, it is just a simple tweak in the computer.

CAD design is NOT just for aesthetics. It is a powerful tool to make the parts you want, correctly, the first time. If you have the extra dough, then I would consider an FEA add on as well to your CAD program. You would be amazed at how aesthetically pleasing a round of Cosmos can make a part on its own (and make you slap your forehead for being so dumb).

Once I had complete a complete CAD model, then, and only then, would I start a prototype (unless you like grinding and cutting things apart).

Here is the thread. Everything was modeled--engine, body, transmission, differential, wheels, bolts, calipers, tires, seats, etc.

http://clubcobra.com/forums/showthread.php?t=85278

http://www.kirkhammotorsports.com

 

[ornerynorsk]

Form follows function. You only get into trouble when you try to reverse this procedure.