If I decide to build a custom chassis for a different donor car, what parts would I need to measure in order to correctly asses the size of my chassis. I already have some good ideas, but what else?
Engine
Transmission
Steering Rack
Driveshaft
Size of Driver/Passenger
Rear End
Radiator

What else?

Wheels, uprights, coilovers, seats, battery, pedal box, master brake cylinder, handbrake?

I don't think wheels would affect my measurements at all... also, what are uprights? (I'm an American ) Also, coilovers would only effect ride height, so that shouldn't effect it. I forgot about adding the seats and pedal box, thanks. The battery and Mastery Brake Cylinder will be up against the firewall so I shouldn't need to worry about the sizes of that. Also, the handbrake is connected to the tranny, so I shouldn't need measurements of that. Anyone else?

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Originally posted by Louis M
I don't think wheels would affect my measurements at all... also, what are uprights? (I'm an American ) Also, coilovers would only effect ride height, so that shouldn't effect it.

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Originally posted by Louis M
Also, coilovers would only effect ride height, so that shouldn't effect it.

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Originally posted by 9904169
all I'm saying is i would bear them in mind, as you dont want to leave yourself having to buy anything too extreme, as the funny sizes normally cost a whole lot more too.

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Originally posted by 9904169

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Originally posted by Louis M
I don't think wheels would affect my measurements at all... also, what are uprights? (I'm an American ) Also, coilovers would only effect ride height, so that shouldn't effect it.

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I'd disagree, as depending on your engine height, it is farily important to work out how much room you will have to play with underneath, rather than cringing every time you drive over a grain of sand and worrying about your sump.
Also, handling will suffer as a result if ride height is very high, and vice versa.

It could work out you will need 20 inch wheels with 17 inch shocks to get the thing moving.

what am I saying, 20" wheels is small for an american?

all I'm saying is i would bear them in mind, as you dont want to leave yourself having to buy anything too extreme, as the funny sizes normally cost a whole lot more too.

cheers
Mark

[Edited on 11/5/04 by 9904169]

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Being slightly facetious shorten the wishbones, either narrower track or wider body. Or wind up the pre-load and sacrifice ride quality and droop handling. Or move the top coilover mounting point (easier said than done), the list goes on

You could also move the coilover wishbone mounting point towards the car, but that is not a good idea (see thread on wishbones bending and you will notice that this can put some bending moments onto the wishbone in a less than adequate place not wishing to teach granny to suck eggs).

Sorry shitty day

[Edited on 11/5/04 by Digger Barnes]

[Edited on 11/5/04 by Digger Barnes]

however, that wouldn't affect the sizing of the chassis... correct? that's all i'm working on right now... hammering out the chassis and building it on cad

Upright = what we call (inaccurately) a spindle.

In Brit-speak, there is a spindle also, which is the jobby-do that the wheel hub rotates on. As we call that a spindle also, US Locosters have generally adopted "upright", here and on the Yahoo NA list, too.

the only parts you really need to measure are wheel parts (for working out suspension geometry), engine, tranny, and differential/rear axle. Pretty much everything else can be added on a design-as-you-go basis.

I recommend reading through back posts in 'Chassis' and 'Running Gear' sections to get a handle on the key design issues.

Pete

Good call Pete.

It can all be a very contentious issue this design stuff. But be aware if you are deviating from the book design there is a large amount of information that you will need to digest and understand before cadding up the ‘final’ design. That is if ride quality or performance or even just predictable handling is important to you.

But if it is going to be very similar to the book dimensions then don't worry it will all work out (so I am told).

BTW it will affect the chassis design (by how much depends on how different your donor bits are).

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Originally posted by Louis M
I don't think wheels would affect my measurements at all...

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Also, coilovers would only effect ride height, so that shouldn't effect it.

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I forgot about adding the seats and pedal box, thanks. The battery and Mastery Brake Cylinder will be up against the firewall so I shouldn't need to worry about the sizes of that.

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Also, the handbrake is connected to the tranny, so I shouldn't need measurements of that.

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Anyone else?

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Yep all that too

Just a thought, but if you have no idea how wheel sizes, suspension geometry, weight placement or packaging effect the overall package of a vehicle (probably not going to be moving at neglibable speeds), then perhaps it would be best to a) do a lot more homework on vehicle design prior to even touching autoCAD, or b)sticking with a book (or close approximation thereof) for the first time around and then deciding what needs changing. Afterall, it has been pointed out a few times that once everything else has been done, fabricating a new chassis is a relatively easy assignment. I've done mine in under two weeks working on it part time. But, best of luck to you, Cheers!

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Originally posted by Louis M
however, that wouldn't affect the sizing of the chassis... correct? that's all i'm working on right now... hammering out the chassis and building it on cad

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Oh, I did forget to mention I spend about three months designing the new geometry and FEA'ing the chassis prior to cutting the first steel. So I guess that means the chassis took 3.5 months. Well, have to draw the line somewhere, as I'm sure I spent a few months thinking about it before I put it on computer. Cheers!

alright, so start w/ the suspension, then build your chassis around it... k thanks.

Sorry if I sounded a bit rough.
There is a lot of information on suspension design on Internet. The degree of simplification vary and can be confusing, some information might even be wrong. The “absolute suspension design” is the one that make YOUR car respond the way YOU like it to.
Don't forget to check that you can buy or modify parts to fit your design, steering racks are a typical source of problems. Also keep an eye on what the final result might look like, you don't want to end up here http://www.locostbuilders.co.uk/viewthread.php?tid=13803

Cheers!

i was checking the book again, and since i'm going to have a live rear axle (not irs), then i will not have to deviate from the book much on this. as a result, i will almost copy the book on making my panhard bars and all i will need is to how high my suspension brackets are and how short my coilovers are...

in the same way, as per the book, the entire front suspension is fabricated and all that you need is to make sure the suspension lines up...

looking at the front suspension more, it seems like the only part that I would have to adjust for is the steering rack and coilovers...

Have you checked virtual swingarms and camber gain?

1) I don't know what virtual swingarms are
2) The camber will be based on the size differences between the swingarms, so I will not need to worry about that until after I build the chassis and begin on the suspension

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Originally posted by Louis M
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2) The camber will be based on the size differences between the swingarms, so I will not need to worry about that until after I build the chassis and begin on the suspension

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oops, i didnt' mean swing arms, but those pipes which connect the chassis to the wheel (i'm blanking out right now on the name)... anyway, i will put my steering rack with calipers on, then make my arms in order to make the camber 0 or slightly neg.

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Originally posted by Louis M
1) I don't know what virtual swingarms are
2) The camber will be based on the size differences between the swingarms, so I will not need to worry about that until after I build the chassis and begin on the suspension

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Front: I will read a lot more about this.

Rear: I still don't understand how the rear will be any different other than the book chassis since I will be using a solid rear (from mustang), similarly to the book... all the rear suspension consisted of was panhard bars, coilovers and the wishbones... so that will be straight out of the book right? all i will need is to compensate for the 7" wider the axle is...

Sounds like you'll get there Louis. And you're pretty close on the rear end, except those wishbones are called trailing links. A book design may work quite well if you follow it nearly exactly, but if you wanted, for your own edification there are some cool points to research in regard to four link suspensions (thats the trailing links part) and panard rods (depending on where they're mounted, they can be used to tune over/understeer aka NASCAR and sprint cars). Cheers!

Front: Sounds good! As I said before it's not to hard to come up with something thats better than the book. A really tricky bit can be to find/make a good drawing of the upright (Thanks Juão!).

Back: A live axle is very straight forward and should not be any problem. What can fail in the rear is looks. When we were going to build our first chassis we started by fitting the wheels to the live axle, tried on the wings until the wheels filled the arches and then measured the distans between the wings to get the width of the frame.

Good Luck and Cheers!

[Edited on 04-5-29 by leto]