Sandrail Chassis Design in AutoCAD (Solidworks)

[TheDudeWhoWantsToBuildACar]

Hello,

 

I am a Mechanical Engineering student with a massive interest in vehicle engineering. I have not gone into any details about automotive engineering as I'm only starting my second year. However, I want to build a car anyway, I have the materials and the tools. I only have one small problem. I have never designed a sandrail before and I need to get my design in a CAD program (Solidworks) so I have one simple question.

 

How do I design a sandrail in Solidworks from some rudementary sketches?

 

I only want to focus on the frame itself, It needs to fit an LS-1 and I am placing it in the front as opposed to the normal rear engine placement to make room for the LS-1's transmission. I am not worrying about the engine mounts, brackets, suspension placements, and their mounting points. JUST THE FRAME, I will figure the rest out later but I need a platform to figure those things out on first.

 

If anybody here has experience designing sandrails in CAD, can you point me to where I need to start? Any and all information is greatly appreciated. Thank you!

 

 

[TheDudeWhoWantsToBuildACar]

Well I figured it out anyways, For anyone that just happens to find this forum looking for the answer to the same question I will tell you what I have learned. This will be specifically for a double wishbone suspension racing car, no offloading knowledge yet. I will not go into any detail into the terms used, your not dumb; you know how to read a book and use google. I will give the names of good books to read about suspension geometry that will teach you.

 

Step 1: Pick your tires. You want the widest possible tires with a good sticky compound.

Step 2: Pick your rims. 3 piece rims offer good flexibility when changing wheel offset which is important. generally you want the biggest rim that will clear the brake calipers and rotors. Nothing less and nothing more. Just enough to clear the components is just right. This will also determine the diameter of your tire.

 

Step 3: Now that you have a rim and tire for your car, find out what bolt pattern your rim has, that will determine what hub you will use. It could even be that you choose the hub before the rim. Say you use a rim for with a 5x120 Bolt pattern, well the C5 corvette has the same bolt pattern, and has good aftermarket hubs, plenty in scrapyards. use C5 hubs. (this also forces you to use C5 CV Axles since the splines will match up with the C5 Hub. Unless you want custom axles of course.)

 

Step 5: Congrats, you know have a tire, rim, and a hub to join those two to the knuckle; Now it gets very complicated and is to much to explain in a forum post. But you need to figure out where your knuckle ball joints will be located. You do this be determining your King Pin Inclination. Lets use 8 degrees for example. It is also an advantage to put your knuckle within the wheel rim. Your ball joints will be located on a vertical line tilted by 8 degrees within the rim.

 

Step 6: You now have ball joint locations and everything you need to finish your geometry. Choose a point off in space say 60inchs from the outer edge of the right tire. This is your swing arm length. Now its time to play connect the dots. Draw straight lines going from the ball joint locations ON THE LEFT SIDE all the way to the RIGHT SIDE swing arm point you've chosen. There is where your upper and lower controls arms are located along those lines. Repeat this step for the opposite side.

 

Step 7: That's it, now you have suspension geometry, now you begin to design your frame. It is far from perfect, but this will get you in deep enough to see how things come together, from there you can learn more and start making sense of it all.

 

There is a lot more that goes into this, I have only barely explained front view geometry, there is a side view geometry as well. These books will give you a better explanation on how to turn a pile of scrap tubes into a car.

 

They are the sacred texts.

EDIT: Before you read these books, you must sit and listen to this song just before you open the book and begin reading. Because that is what finding these books was like to me.

 

1: Race Car Vehicle Dynamics - By: William F. Milliken and Douglas L. Milliken

2: Chassis Engineering - By: Adam Herb (This is my favorite and would recommend this book above all others.)

3: Chassis Design - By: Maurice Olley

4: Racing and Sports Car Chassis Design - By: Michael Costin and David Phipps

Edited August 26, 2023 by TheDudeWhoWantsToBuildACar