Louis M
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| posted on 9/5/04 at 11:11 PM |
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When Building Custom Chassis: What Part Sizes Do You Need?
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?
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leto
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| posted on 10/5/04 at 09:15 PM |
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Wheels, uprights, coilovers, seats, battery, pedal box, master brake cylinder, handbrake?
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Louis M
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| posted on 11/5/04 at 10:42 AM |
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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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200mph
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| posted on 11/5/04 at 10:50 AM |
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quote:
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.
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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Digger Barnes
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| posted on 11/5/04 at 11:32 AM |
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quote:
Originally posted by Louis M
Also, coilovers would only effect ride height, so that shouldn't effect it.
actualy coilover length does not affect the ride height by itself it is their mounting position (dictated by the suspension geometry) along with
length and and spring rate that affects ride height.
quote:
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.
Not to mention extra time and head scratching
[Edited on 11/5/04 by Digger Barnes]
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Louis M
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| posted on 11/5/04 at 04:24 PM |
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quote:
Originally posted by 9904169
quote:
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.
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]
Besides lengthening the coilovers, is there even a way to increase the ride height?
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Digger Barnes
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| posted on 11/5/04 at 04:57 PM |
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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]
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Louis M
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| posted on 11/5/04 at 05:36 PM |
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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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pbura
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| posted on 11/5/04 at 05:40 PM |
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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
Pete
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Digger Barnes
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| posted on 11/5/04 at 06:07 PM |
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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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leto
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| posted on 11/5/04 at 07:19 PM |
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quote:
Originally posted by Louis M
I don't think wheels would affect my measurements at all...
They will effect the way the finished car looks and handles but if thats not an issue, fine.
quote:
Also, coilovers would only effect ride height, so that shouldn't effect it.
There isn't much room around the upper A-arm.
It's nice to know that things will fit and can move freely before you spend hours and hours fabricating them.
quote:
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.
The battery is quite heavy so handling will improve if you can to get it down on the (more crowded) floor level quote:
Also, the handbrake is
connected to the tranny, so I shouldn't need measurements of that.
OK, that was maybe a little overkill quote:
Anyone else?
I forgot rear wings and nose cone, if you are going to buy them.
Cheers
[Edited on 11/5/04 by leto]
[Edited on 11/5/04 by leto]
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Digger Barnes
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| posted on 11/5/04 at 07:32 PM |
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Yep all that too
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crbrlfrost
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| posted on 14/5/04 at 05:31 PM |
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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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leto
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| posted on 14/5/04 at 08:57 PM |
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quote:
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
Well, no.
If you try to design a car one piece at the time you may very well end up as Johnny Cash did in the song with that name, or worse (“One piece at the
time” I recommend it, it's rather funny. Hmmm... Yes, it is country BUT the lyrics is about building your own car).
The book-frame is designed to fit the Cortina upright, from what I understand they are not easy to find in the US. The geometry of the Cortina upright
is “somewhat odd” and it will, most probably (and hopefully), be hard to find something that reassembles it. So you will have to design your own
suspensions. The book design is fair, but it's not to hard to come up with something that is better.
The suspension brackets have, obviously, to connect to the frame, so the suspension must to be designed before the frame. (and the wheels will effect
the suspension design, but I guess you have figured that out by now ).
Good luck, and happy building.
“I'm gonna ride around in style
I'm gonna drive everybody wild
'Cause I'll have the only one there is a round”. (J. Cash)
[Edited on 14/5/04 by leto]
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crbrlfrost
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| posted on 14/5/04 at 11:19 PM |
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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!
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Louis M
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| posted on 22/5/04 at 11:34 PM |
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alright, so start w/ the suspension, then build your chassis around it... k thanks.
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leto
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| posted on 23/5/04 at 08:36 AM |
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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'm gonna ride around in style
I'm gonna drive everybody wild
'Cause I'll have the only one there is a round”. (J. Cash)
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Louis M
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| posted on 23/5/04 at 05:28 PM |
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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...
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Louis M
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| posted on 23/5/04 at 05:28 PM |
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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...
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Louis M
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| posted on 25/5/04 at 03:32 PM |
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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...
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leto
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| posted on 25/5/04 at 06:01 PM |
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Have you checked virtual swingarms and camber gain?
“I'm gonna ride around in style
I'm gonna drive everybody wild
'Cause I'll have the only one there is a round”. (J. Cash)
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Louis M
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| posted on 25/5/04 at 08:31 PM |
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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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jcduroc
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| posted on 25/5/04 at 08:55 PM |
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quote:
Originally posted by Louis M
...
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
And camber, do you know what it is? And how to change it?
Cheers,
João
JCM
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Louis M
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| posted on 26/5/04 at 12:22 AM |
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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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leto
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| posted on 26/5/04 at 05:12 PM |
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quote:
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
Ok, that was just a small test to see if you done your homework like crbrlfrost suggested, obviously you have not. Here is a place or two to start.
http://www.rqriley.com/suspensn.html
http://www.gmecca.com/byorc/index.html
(last link provided by miller, thanks!)
“I'm gonna ride around in style
I'm gonna drive everybody wild
'Cause I'll have the only one there is a round”. (J. Cash)
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