# [EVDL] Scratch Built EV (In theory)



## EVDL List (Jul 27, 2007)

Hi Jeff and All,

----- Original Message Follows -----
From: "Jeff Miller" <[email protected]>
To: <[email protected]>
Subject: [EVDL] Scratch Built EV (In theory)
Date: Mon, 9 Jun 2008 22:53:45 -0600

>Hello all
>This is my first post so please be gentle! I don't have
>any specific questions yet just sniffing around for people
>who have done what I am considering.
>
>I am considering building an EV (or two) from scratch out
>of composites. 

I'm assuming you know what you are getting into
here/ have enough composite experience? All composite
scratch built EV's can be the best possible way to go but
needs to be looked closely due to the work. If one is doing
3-5 then it's worth it as the first one is most of the work.
I and some others have an excellent archive on just
this at <[email protected]> that goes thru the whole
process in many different ways with many tricks to lower
man-hrs, cost greatly. It takes some time to get approved
but well worth it.
I'm doing a unibody/chassis 3wh 2 seat sportswagon
myself and built custom, production boats for 20+ yrs.. 

I did find Lee Hart's Sunrise site and
>spent some time seeing what I could see there but it is a
>long drive to Minnesota to get more info (not that I won't
>eventually as my plans proceed). I found kit car makers
>but most of those currently in production don't seem to be
>well suited to my needs. Ultimately the Sunrise is
>approaching what my wife wants but I tend to stray closer
>to the edge than that.

As designed the Sunrise is a 4 seater. You'd have to
change the central battery box to something completely
different to seat 6 which it can without the box. 


>
>At this point I would say my designs lean towards the Solar
>Car racer designs except having real tires. The low drag
>body that is painful to wiggle out of sounds perfect to me!
> I would estimate I am two years from starting construction
>but if gas hits 6 it might be sooner. I have a short drive
>to work but I would like to build something where range is
>less of an issue. I have friends that might decide to
>build one if I get past 100 mile range and while that is
>lofty I think it is possible to build a spartan 600 pound
>car that can carry two people and a 1000 pounds of
>batteries. If all goes well for Caterpillar's Firefly
>maybe I will be able to utilize that technology but I am
>not counting on it.

That describes mine exactly except I use flooded CG
batts and taller so to see and be seen, an important safety
feature. It's really not that hard getting 100 mile range.
My EV without the batts is about 550lbs and 720lbs of batts.
There are other more targeted groups like
Vortex3wheeler, F2R1EV among others.
By the time Firefly's get to the market for us,
li-ions will be less cost most likely. 

>
>I have a family with kids in car seats and all that jazz
>and what works well for me (or my wife) is a minivan! So
>one of my longer term goals is to build a minivan
>replacement. Seats for six to seven people and some cargo
>room. 

That's a big order but not impossible. A Dymaxion
style with front steering would do this well, light and
extremely aero, be easy to build and only one door.

I am more than happy to have it look like an insect
>that mated with a Stealth Bomber if that is what is
>required to make it work. I have some other strange ideas
>like building the seats as part of the structure to add
>more rigidity (moveable pedals and steering wheel)

Excellent idea and the only way you'll get truly
lightweight is to not only be light but also do several
things with each part and connecting them together to
strengthen each other. 


and only
>having one door (think business jet) to keep the weight
>down and strength up.

That can nicely lower costs, time as doors are the
most expensive, hardest to do right body part. In a 4door
car the doors cost more than the body in Detroit!!

I have considered alternate air
>conditioning methods that are most likely not practical.

The best cost/performance is probably a window AC
repackaged and using an inverter off the battery pack.


>
>At this point I still don't know what I don't know yet but
>I am willing to watch, learn, redesign or even discard my
>ideas as they are shown to be idiotic. Feel free to give
>me feedback if you want especially if you have tried
>something like this before.
>
>
>
>I have done a little checking and as I live in Kansas it is
>pretty easy to get an individually newly manufactured car
>titled and registered. Insurance companies are less
>cooperative but far from impossible based on what I have
>read on this list over the last couple of weeks. Also I
>happen to have training building things (including
>composite things) so that doesn't hurt.

Progress has come out in favor of EV's, EV
3wheelers recently, even giving them lower rates because
they rightly believe EV people drive safer.

Jerry Dycus
>
>Have a good night
>Jeff
>
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## EVDL List (Jul 27, 2007)

> Jeff Shanab wrote:
> > I too want to build a all composite EV. It is fun to dream.
> >
> > I just thought of a strange edge minivan concept. cut the width in half
> ...


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## EVDL List (Jul 27, 2007)

> Lee Hart <[email protected]> wrote:
> 
> >Jeff Shanab wrote:
> >> I too want to build a all composite EV. It is fun to dream.
> ...


----------



## EVDL List (Jul 27, 2007)

It just occurred to me, I left the wrong impression.

My problem is space,money and time. The tech worries me less.

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## EVDL List (Jul 27, 2007)

Jeff
I have enough space and time but if you feel like doing a little design work
to keep the brain sharp I could use the help! I am short money too but a
good design will reduce the cost of the project. Interestingly enough the
majority of the work can be done before spending the majority of the money
in this project. Building the chassis and suspension isn't free but only
incurs about one-third of the total project cost while eating up most of the
time. For me design is probably going to take as long as doing the build
but I enjoy a good mental challenge so even if I never get to build it at
least the world gets a neat design to play with.
Jeff


-----Original Message-----
From: Jeff Shanab [mailto:[email protected]]
Sent: Wednesday, June 11, 2008 8:38 PM
To: [email protected]
Subject: Re: [EVDL] Scratch Built EV (In theory)


It just occurred to me, I left the wrong impression.

My problem is space,money and time. The tech worries me less.

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## EVDL List (Jul 27, 2007)

> Anyone
> Suspension design. At this point I would say suspension design is where I
> have the least amount of knowledge. I think I want equal length A arms on
> the front and back because it has the smallest number of questions in my
> mind but if somebody has drawings for things that work I would be pretty
> excited to see them.

You could always do it the easy way. Grab the suspension parts off an old
Miata. Double A Arm front, and multilink rear.
It's a pretty decent suspension and all the hard work is done.


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## EVDL List (Jul 27, 2007)

>
> Anyone
> Suspension design. At this point I would say suspension design is where I
> have the least amount of knowledge. I think I want equal length A arms on
> the front and back because it has the smallest number of questions in my
> mind but if somebody has drawings for things that work I would be pretty
> excited to see them. The other side of the coin is if there are any
> suspension experts on the thread that are willing to look at what I come up
> that would also work but I don't want to reinvent the wheel if I don't have
> to. Jerry I see on your Freedom EV you have unequal length control arms up
> front so naturally I was curious about that design and what I could learn
> from it.


Uh, you mean Un-Equal A-arms correct? equal a-arms can cause a roll
center problem if close to parallel. (there is only one case where this
is acceptable or desirable.

There are a lot of books at the bookstore on suspension design.


Simply put
draw a line through the upper A arm
draw another line through the lower A arm
where they intersect is the instantaneous center, the effect point
at which the wheel moves in an arc when it encounters a bump or is side
loaded.
When a line drawn from this instantaneous center to the contact
patch, where it crosses the center line is the roll center.

When the Center of gravity is above center the body rolls top
towards outside of a curve, if it is below, the bottom swings out like a
pendulum.
So, draw the vehicle, draw the CG and the roll center
then re-draw the vehicle at 1,2,5,10 of body roll. (you can
calculate the angle based on cg and distance above roll center.
Now re-draw the lines through the a-arms and you will get to see the
changes in instantanous centers and most importantly the camber gains or
losses at the wheels.

You don't want the roll center to pass through the center of gravity
during a turn.
You don't want positive camber gain on the inside wheel, you want a
little negative camber game actually.




"how to make your car handle" Fred Puhn ISBN 0-912656-46-8
The datsun in there is from two brothers Bill and Bob swan who I
have talked about. I worked with bill for years and he let me race is
race car.
"Tune to win" Carrol Smith very good book rates geometry formulas,
theory.
"Engineer to win" ISBN 0-87938-186-8 A materials centric Carrol Smith
book,
"Sprint Car Technology Design,theory,suspension" good intro section on
simple suspension
"Race Car Engineering and Mechanics" Paul Van Valkenburgh


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## EVDL List (Jul 27, 2007)

> Jeff Miller wrote:
> > I looked at the book Lee suggested and at 27 pages I am not sure how
> > much I would get out of it. From the guys who have read it is it
> > just process related or does it give some design information also?
> ...


----------



## EVDL List (Jul 27, 2007)

> Everyone When things are designed what CAD package
does this group
> prefer?

http://www.emachineshop.com/download/index.htm

It's free 

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## EVDL List (Jul 27, 2007)

> Jeff Miller <[email protected]> wrote:
> 
> *Snip*
> 
> ...


----------



## EVDL List (Jul 27, 2007)

On Thu, 12 Jun 2008 08:12:08 -0700 (PDT), Rod Hower <[email protected]>


> wrote:
> 
> >> Everyone When things are designed what CAD package
> >does this group
> ...


----------



## EVDL List (Jul 27, 2007)

>


> > Jeff Miller wrote:
> >> I looked at the book Lee suggested and at 27 pages I am not sure how
> >> much I would get out of it. From the guys who have read it is it
> >> just process related or does it give some design information also?
> ...


----------



## EVDL List (Jul 27, 2007)

Jeff S.
Based on what I have managed to figure out you teach for a living probably
in a University environment? You teach something technical but not
engineering. You know your CAD products so I could guess you are in that
field.

A composite structure's properties are calculated like you would an I Beam.
The strength in Tension on the bottom of the beam and the strength in
compression on the top of the beam and the farther they are apart the more
leverage each the top and bottom have on the load. For example assume a
panel made with one layer of a specific cloth on the top and one layer on
the bottom and then vary the core thickness. (for now lets assume the core
is the perfect material that weighs nothing but is very strong) With a two
inch core the top and bottom are farther apart so with a given amount of
deflection the cloth has to stretch much more than something with 1 inch
core. Something with no core at all is very flexible. The core's true
purpose is to prevent the structure from collapse. As just with any I Beam
as soon as the two walls get closer together the rigidity goes away and the
structure fails. Honey comb is very hard to crush but is very flexible,
easy to bend around complex parts and it is used extensively because it is
almost completely air. A true to form design will use the lightest core
that prevents crush for stresses up to fabric failure.

Examples. Think of how tubing fails when you bend it. Any coat hangar,
wire, piece of aluminum or any metal that is bent to failure.
In the tubing it fails by the side walls bowing out and the bottom wall then
collapsing in. The core is the side walls and when they bow out it is over.
The solid metal can't collapse on itself so the surface under tension tears
as it is bent past its limits. Then with the reduced cross section it is
weakened and the new surface in tension fails.

In composites you want to force the tearing scenario but with much less
weight than making it out of a solid piece.

To calculate go to
http://www.fiberglasswarehouse.com/fiberglass_cloth.asp
as they have tech sheets for most of their materials for examples
http://www.fiberglasswarehouse.com/tds/7781.pdf
http://www.fiberglasswarehouse.com/tds/120.pdf
and it tells you the breaking strength of the material in both the warp and
fill direction. Warp is the direction as it comes off the roll so in theory
you could find one Warp thread that is the length of the whole 125 yard role
or whatever. Fill is in the other direction and will only be as long as the
roll is wide. Some cloths are biased and have big variation between the two
numbers.
The breaking strength is in pounds per inch (linear) so figure out how many
inches wide the narrowest or highest stress place is and how many layers of
what breaking strength material and you can figure out the force it will
take to break the cloth. Then you have to figure out the compression side
which I don't know for sure how to calculate but I expect it to be similar
to tension but I don't actually know that. Once you know the failure point
of the top and bottom of the I Beam you then have to know the crush strength
of the core and plug that into the I Beam formula which I have long since
forgotten. http://answers.google.com/answers/threadview?id=753367
http://physics.uwstout.edu/Statstr/Statics/Beams/bdsne49b.htm and other
sources you are sure to know. With that you can calculate the strength of
the beam.

If you are just pulling the beam into complete tension then you should just
be able to total up the breaking strength for the top and bottom. I figured
one part of one car design would have 240 inches wide of fabric on each side
of the core. In pure tension (the front of the car trying to leave the
back) 350 pounds per inch x 480 inches would result in a pure tension
strength of 168,000 pounds of force before it pulled in half. The shear and
bending loads are far more likely to break it than experiencing 168000
pounds of force in one direction.


As far as anything with composites large radiuses are your friend. You
don't want to try to get fabric to go into a tight corner or around a sharp
bend. Also please remember from above you want to make sure the Warp fibers
are carrying the load. I didn't plan on making molds just form the core out
of the foam you have decided resists crush as required and then lay the
material onto the outside and inside of the foam. When you do this you
can't start out with Gelcoat in the mold so you will have some texture on
the outside but you won't have the weight or expense of the gelcoat. I am
unsure about Gelcoat after the fact but for my low cost purposes I can't
afford gelcoat anyway. In this type of build the design of the core will
dictate how fast and easy it is to lay-up. Where you put the seams will
greatly affect how it will look when you are done. I find it useful to not
fight gravity also and set up some sort of rig so you can rotate it so the
piece you are working is being pulled to the core by gravity. If you have
more money and time you can lay it up and vacuum bag the lay-up to get an
even thinner part that has a higher fiber to resin ratio which is desired.
Using Prepregs the pro's can get up to 90% fiber to resin ration by weight.
By hand 80% is a pretty good achievement. Interestingly enough you can use
those facts to estimate your final weight of the assembly assuming you
already know how much the fabric and core will weigh.

As far as design goes you can mix materials types and weaves. Most likely
you will need more strength in one direction than the other so you may
choose to use some unidirectional Carbon fiber tape in one direction and
then cover the whole thing in a nice balanced weave to give it the
additional strength in the other directions but use fiberglass because it is
cheap and the bulk of the load is carried by the tape.

Basically if your first adventure is a foam bathtub that gets narrow at the
ends and wider in the middle where you sit it shouldn't be to hard to lay
up. Where it gets narrow you have the same width of cloth if not more than
you did where you are sitting but it is concentrated to carry the loads to
the suspension mounting points.

Thanks for the tip on what race cars use for bolt holes and the suspension
information and I will be re reading that post a few times until I actually
understand everything you said in it. I will also check out all of the
suggestions for CAD programs like Solidworks and see what I can find for
cheap. The beauty of doing it in CAD is you can build the pieces, assemble
them, make sure they fit, then print out all of the drawings for all of the
indvidual pieces and make them all. If you do that and hold tolerance it
should all fit together properly just like the computer said. I have
actually seen this work on several occasions. This idea has shaved years
off of the process of designing an airplane but that is a different message
on a different night.

enjoy!
Jeff M

-----Original Message-----
From: Jeff Shanab [mailto:[email protected]]
Sent: Thursday, June 12, 2008 8:42 PM
To: [email protected]
Subject: Re: [EVDL] Scratch Built EV (In theory)




I have two big questions about building my composite chassis
How to I estimate/plan the number of plies and core thicknesses
needed to make something strong enough.
How do I make molds and tooling that will lend themselfs to
effective production.


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## EVDL List (Jul 27, 2007)

>
> Jeff S.
> Based on what I have managed to figure out you teach for a living probably
> in a University environment? You teach something technical but not
> engineering. You know your CAD products so I could guess you are in that
> field.

Whoa! I'll take that as a complement, but probably not as close a guess
as you think.
I once was a mechanical engineering electrical engineering double
major. Now hang on to your shorts, I stopped when I had a semester left
in the ME and about 1/2 of the EE. Due to money and family issues. I cut
my teeth on cad systems as they introduced autocad to the college (oops,
showing my age) and was very very unimpressed. 2d cad was a way to help
a person draw, I saw it as a waste kinda like I once saw documentation
on code, something to do later to help communicate the design. Then I
got to take a pilot class on SRDC IDEAS a true solids program with
stress analysys but you had to be at a tektronics 4107 graphics terminal
connected to a PDP computer. 

Then I spent 23 years in plastic injection molding where I got to use
solidworks. Tried autocad 3D and the difference is about 20 hours trying
to do something in autocads pseudo 3D took 20 minutes in solidworks.
Never looked back.

Then I went back and got my computer science degree. I am a software
engineer now and am 1/2 way through the masters program.
humm, Maybe I do spend too much time at the university. LOL

I guess the point is I have always believed in a good balance of
experience and theory. someone once said "I engineer things that can
actually be built"

Thanks for the links, I will go through them. I have books on
calculating the strength of specimens, But I would like to find software
I can afford that can mesh a 3D shape with varying plys and core
densities and get an approximation of strength. Especially because I
want to try some 3D core re-enforcements.

I know enough to know this is an approximation, but it is the relative
degree of the strengths in different areas that I want to
optimize/equally distribute.

In the long run We'll want vibration analysis and crush analysis in
addition to strength and fatigue.

The real beauty in solidworks is when you get to the revision. It
integrates the 2D drawings you create off of the 3d model and has a undo
bar int he left pane that you can slide back in the model hierarchy,
change something, slide it back forward and regenerate the 2d drawings.

Here is the standard methodology that solidworks uses.
Grab a 2d work surface and draw a shape. ----like an adapter outline
Add dimensions until it is completely constrained, goes
red-->blue-->black
extrude, revolve, loft, whatever into a solid ---extrude to 3/8" thick
pick a surface, it automatically becomes the 2D surface for the next
set of operations
draw and extrude a bolt hole
array the bolt holes in a pattern or from a spreadsheet.
draw a center hole and extrude through
chamfer all the holes and radius the center hole.

Here is where it's power shows. Lets say in the 2nd step you made a mistake.
You can change a dimension in the 2d drawing and it will show up on
the 3d model as well
or if there may be interactions, drag the bar up the hierarchy to step
2, It undoes the visual model on the screen without loosing everything
that comes after it.
You make the change, then drag the bar forward It re-applies changes
adjusting as necessary along the way. if the hole is radiused and you
change the hole dimensions, you don't have to re-radius it.

Standard disclaimer, I don't work for solidworks, indeed their choice to
sucome to the pressures of parasolid (the engine) and go to annual
licensing and significant jump in prices didn't win much from me.


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## EVDL List (Jul 27, 2007)

> Jeff Shanab wrote:
> >> Jeff Miller wrote:
> >>> I looked at the book Lee suggested and at 27 pages I am not sure how
> >>> much I would get out of it. From the guys who have read it is it
> ...


----------



## EVDL List (Jul 27, 2007)

The problems I've had with mechanical CAD programs stem from the 
programs themselves, and from my lack of understanding in how to use 
them productively.

Let me explain it by analogy. I use electronics CAD programs all the 
time. The basic idea is that you have several related programs that work 
together to produce the final design.

The schematic program draws a symbolic representation of the circuit, 
with idealized resistors, capacitors, inductors, transistors, etc. It 
can make parts lists, wiring diagrams, and other useful printouts to 
help you actually build it.

The simulation program uses the schematic to test an idealized version 
of the circuit without actually building it. It doesn't accurately 
reflect real circuit operation, but gives you a rough idea if the 
circuit works at all. You generally go back and forth between schematic 
and simulator to refine your circuit (adding parts, changing values) 
until it seems to work well enough to actually build.

The layout program lets you make a printed circuit board. It adds the 
physical size of each part and its pin locations. You can move the parts 
around until they fit on the board, and add the wires to interconnect 
them. The layout program does all the "accounting" to be sure parts 
don't overlap or have too small a space between traces, etc.

These electronic CAD programs are faster and more accurate than doing it 
all by hand because they automatically keep track of so many details for 
you. The parts list is updated when you change the schematic. Moving a 
part on the PC board automatically moves the related traces, and warns 
you if it encroaches on another part. The simulator lets you discover 
you're trying to dissipate 10 watts in a 1 watt resistor.

The CAD packages I've tried don't come close to this level of 
integration and automation. They'll cheerfully put a 2" hole in a 1" 
bracket. They won't tell you that a 1/16" sheet metal bracket won't 
support 1000 lbs. You can easily design parts that won't work or are 
impossible to build.

Editing a design is especially tricky. They don't seem to link related 
parts or do error checking; moving a hole on a part won't move the 
mating holes on a cover.

Perhaps they *can* do it; but I can't figure out *how* to do it. The 
manuals are no help. It takes me far longer to draw a bracket with one 
of these CAD packages than it does to just do it with pencil and paper.
-- 
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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## EVDL List (Jul 27, 2007)

> Editing a design is especially tricky. They don't seem to link related
> parts or do error checking; moving a hole on a part won't move the
> mating holes on a cover.

Solidworks and ProE, as well as a few others are "parametric" modeling 
programs, which allow you to easily create parametric links between 
features. In fact its fairly automatic to create links based on how you 
create the model. I use Solidworks everyday, and so I have a lot of 
experience that helps me decide when to create links and when not to. I can 
revise one dimension on a 10,000 part assembly, and all the related parts 
will update!

> Perhaps they *can* do it; but I can't figure out *how* to do it. The
> manuals are no help. It takes me far longer to draw a bracket with one
> of these CAD packages than it does to just do it with pencil and paper.

It is a shame that solidworks is so expensive - it really is an incredible 
tool, and is very easy to use. A couple of days with the tutorials will 
have you creating parts, assemblies, and appropriate relations between 
parts. On the topic of making brackets that hold 1000 pounds - most people 
use separate FEA (analysis software) for this. Cosmosworks is a solidworks 
plugin that does this in the same modeling environment and can react to 
changes in dimensions, ect.

Jon 

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## EVDL List (Jul 27, 2007)

There is a world of difference between a simple 2-D package which should
properly be called a Computer-Assisted Drafting package and a fully featured
3-D mechanical design package.

Unfortunately, since things like finite element analysis (what would catch
that sheet metal bracket having 1000 lbs thrown at it) and manufacturability
checking are both so complex, compared to electrical simulation, that there
aren't any good but inexpensive mechanical packages out there.

I'm not a MechE so I'm not really up on what is available but on many projects
I have a MechE sitting beside me and we talk. I think that Solid Edge has
some of the best bang for the buck.

In this package you can design a part or an assembly in 2-D windows (plan,
side, top views) that are linked and the 3-D part materializes in a 4th
window. One can edit the 3-D image (difficult) or go back and edit the
appropriate 2-D view.

It comes with a few design checking extensions as standard and others are
available. One standard package is sheet metal. It can identify
un-manufacturable sheet metal objects. It doesn't have FEA as a standard
feature so it won't check for overload.

It also has a structural steel package that lets you build things out of
I-beams, tubing, bar and such instead of having to draw them out. Metadata
associated with each object lets the program do some design checking.

I have now reached the end of my knowledge of the package 

One of the major problem with mechanical design rule checking and in
particular, manufacturability checking is that both depend so heavily on the
particular machines to be used to make the object. It's easy to catch a weld
or a hole to be tapped inside a closed box but it's much more difficult to
catch the interference of the machine tool head with the part being machined
since the head size, shape and location vary so much with manufacturer. The
program has to contain a library of sorts for every machine tool and every
combo of attachments that might be used.

The difficulty in simulating all this stuff is why rapid prototyping/rapid
manufacturing is such a hot field. Do the best you can and then have a rapid
prototype model built and see how an actual physical object fits. You can put
the object on the candidate CNC machining center, run it in simulation mode
(does all the motions but without any cutting tools) and see where the
interference is. Maybe just a change in tool path or collet length or
something will fix the problem. Or it might take a major design change.

I have now pretty much reached the end of my knowledge of mechanical CAD in
general.

John



> Lee Hart <[email protected]> wrote:
> 
> >The CAD packages I've tried don't come close to this level of
> >integration and automation. They'll cheerfully put a 2" hole in a 1"
> ...


----------



## EVDL List (Jul 27, 2007)

I don't know if everyone's moved on from suspension questions, but
interested parties may want to check out a book called "Chassis Engineering"
by Herb Adams regarding suspension. It's primarily for circletrack racers,
etc, but covers a lot of important basics. I've learned a lot from it,
although I would not consider myself an expert in any regard. FYI.

Table of contents:
1. Tire characteristics
2. Weight Distribution & Dynamics
3. Roll Angle and Roll Force Distribution
4. Bushings and Deflections
5. Springs and Shocks
6. Types of Front Suspension
7. Front Suspension Design
8. Building a front suspension
9. Live axle rear suspension design
10. Independent Rear Suspension design
11. Building Rear Suspensions
12. Frame design
13. Building a frame
14. Aerodynamic downforce
15. Rotating Inertia
16. Vehicle Testing and Tuning
Index.

- MM


> Anyone Suspension design. At this point I would say suspension
> design is where I have the least amount of knowledge.


Same here. I know just enough to be dangerous.  We chose to lift the
suspension intact from a production vehicle, because it's already
designed correctly (at least better than we can do it). Make changes on
an incremental basis, testing each as you go. For example, we changed
from coil springs to air springs, and are using adjustable shocks.


> I think I want equal length A arms on the front and back

A arms are almost always unequal in length. The upper arms are much
shorter. This makes the tire lean out relative to the body as it moves
upward. Since the body leans out during a turn, this keeps the tire
perpendicular to the road (when you get the dimensions right).
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## EVDL List (Jul 27, 2007)

Jon wrote -


>> Editing a design is especially tricky. They don't seem to link related
>> parts or do error checking; moving a hole on a part won't move the
>> mating holes on a cover.
>
> Solidworks and ProE, as well as a few others are "parametric" modeling
> programs, which allow you to easily create parametric links between
> features. In fact its fairly automatic to create links based on how you
> create the model. I use Solidworks everyday, and so I have a lot of
> experience that helps me decide when to create links and when not to. I 
> can
> revise one dimension on a 10,000 part assembly, and all the related parts
> will update!
>
>> Perhaps they *can* do it; but I can't figure out *how* to do it. The
>> manuals are no help. It takes me far longer to draw a bracket with one
>> of these CAD packages than it does to just do it with pencil and paper.
>
> It is a shame that solidworks is so expensive - it really is an incredible
> tool, and is very easy to use. A couple of days with the tutorials will
> have you creating parts, assemblies, and appropriate relations between
> parts. On the topic of making brackets that hold 1000 pounds - most 
> people
> use separate FEA (analysis software) for this. Cosmosworks is a 
> solidworks
> plugin that does this in the same modeling environment and can react to
> changes in dimensions, ect.

Excellent description of Solidworks. I've been using ACAD in its various 2D 
flavors for about 20 years and recently was introduced to Solidworks because 
I wanted to start doing 3D drawing (and also change jobs). I took the 
beginner level course and really appreciated the intensity.

The excitement of the program comes when you draw one bracket, then draw 
another bracket, draw a strut to hold the brackets, then a linkage to 
connect the brackets and make them interact. They become parts in an 
Assembly. Change one part and the assembly changes. Solidworks will also 
tell you where they bind or interfear with other parts of the assembly.

Cosmoworks is even more rewarding - you can populate a box with known or 
newly designed elec components, each of which has specific values and see 
where it is too hot, you can move a component or add another fan (as an 
example) to see how the thermal envelope changes. You can redesign the 
bracket, slim it down here, fatten it there, lighten it with holes etc, then 
ask Cosmoworks is it structural? It really is an amazing program.

Well worth the $139 for the 24 month licence. But I don't know how crippled 
it is. Maybe it only says "Educational Version".

Rush
Tucson, AZ
2000 Insight, 62lmpg, #4965
www.ironandwood.org
www.Airphibian.com
www.TEVA2.com 

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## EVDL List (Jul 27, 2007)

I wantred to share my personal experience here. One of my other hobbies is
building robots (sorry nothing spectacular yet). For the DARPA Grand
Challenge 2005, I started with building a chassis from scratch. I wasted
many months, coming up with my unique design and chasing down hard to find
parts. I ended up buying a ATV to use as a chassis. Though I had done a lot
of work, I was not far enough along to qualify for the race. (Not learning
my lesson. I spent many more months fabricating tractor tread from scratch
for the next contest. I didn't apply for the next one.)

I think you are trying to do two things here. You are trying to learn about
Electric Vehicles. You are trying to learn to design chassises. Both are
good. Combined that would be great. However, in practice, you may want to
start with some prototyping projects. You could start with a bike. Get a
decent frame. Add a small motor, controller and battery. Use that to learn
about battery use, motor size and controller control logic. It should not
set you back much (a few hundred). In the end you will have a nice bike to
take to the store. On the larger scale, convert a used car. This will cost
several thousand dollars. The car frame will be your cheapest purchase. (I
just bought a 99 Sonoma PU for $1K with a bad head gasket. Most running PU
start at $2K (my Escort chassis only cost $200)). In the end, you will have
learned about EVs and have a decent motor, battery and controller to go in
you specially designed frame.

Please don't consider this as me trying to talk you out of what you are
doing. I am not. I think more people trying to make a better EV is the best
thing. I am just suggesting a path, that will allow you to meet you goals
without being overwhelmed.

Don

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## EVDL List (Jul 27, 2007)

All the things you complain about are common in so many I call "wanna
be" cad programs, and especially the "Constructive Solid Modelers" They
are drawing tools. Frustrating wastes of time that give CAD a bad name.

What separates solidworks, pro-engineer (and maybe alibre, it looks to
be a solidworks clone) is that it IS all that. The key here is
"Parametric solid modeler" meaning the model is build off of the
parameters which can be changed at any time. (ok the other think that
separates them is 5K-15K per seat sometimes per seat per year)
Handling part configurations, 2d drawings are generated not drawn, and
changing a dim on the 2d drawing changes in all 2d drawings and indeed
the 3d model.

Solidworks does constrained assembly
It allows the assembly to dictate a feature on the part.
You can create a cover, create a box and a bolt, assemble all three,
even according to a spreadsheet. Then referencing the hole created
chamfer, enlarge, etc.
Change the number in the spreadsheet or the dimension from the edge in
one of the 2d drawings or just change the dimension on the display and
all actions related are re-done.

It really does match your analogy.

In the Simulation side you can pay more $ and get cosmos. You can run
stress analysis and chose diminsions that vary based on the result or
just to get a distortion or stress map like you would get a freq
response table for a filter circuit in AC Analysis.

The bracket is a great example. When you start out you submit it to
cosmos and the post processing is done is solidworks to display how bad
it distorted.
As you move forward you tend to analyze it by having it tell you the
material thickness that results in < 10% deflection at 1000lbs of load.

Where I work they use pro-engineer and an upper end electronics
package(can't remember the name). The demo I saw created a board,
simulated it and analysed the heat dissipation while in the enclosure.
The circuit-baord was a mechanical part in pro-engineer and was also
used to create the tooling for and the schedules for the pick an place
machine.

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## EVDL List (Jul 27, 2007)

The CAD discussion can go on for quite a while. The best CAD package is
usually the package which the individual have had the most experience with. 
I have used ProE, SolidWorks, and OneSpace CoCreate. Each have their
strengths and weaknesses. OneSpace is probably the easiest to pick up for
me. There is a free home version you can get at the website below. I think
there are limitations such as assembly sizes .... with the free version. I
have not used the PE version since I have a license.

http://www.cocreate.com/products/pe2/ModelingPE2.aspx

As for suspension design, it is a very complicated topic if you are planning
to develop a race car ... If you are interested in developing a suspension
for an EV, I think the design becomes much simpler. For EVs, the tires are
typically narrow and the handling does not need to be great. One does not
have to be overly concerned about camber curve at high cornering speed or
braking. 
Jeff mentioned he wanted to use equal length A-Arm. The equal A-arm set
parallel to the ground puts the roll center at the ground. I would also
recommend using a larger anti-roll bar if you plan to used heavy lead acid
batteries. Minimizing bump steer is still important. Lastly, don't forget
about designing the steering to have correct Ackerman angle (I did not - and
it is a pain to steer the car at low speed).

There are many good suspension book. I recommend Fred Puhn's "How to make
your car handle" because it is easy to understand. Please read at least one
of the suspension book prior to designing your own suspension. As some has
already mentioned, the Miata is a great suspension part donor. Other good
spindle/hub donors include Mustang II or Fiero.

your novice car designer,
Minh








> provo_spain wrote:
> >
> > I don't know if everyone's moved on from suspension questions, but
> > interested parties may want to check out a book called "Chassis
> ...


----------



## EVDL List (Jul 27, 2007)

Don
I respect your opinion and if I had a few hundred bucks to play with right
now I might start building something but I don't have any spare capital for
at least another year. In the mean time I can draw upon the large volume of
information on the internet and start designing something. In a couple of
years when I will have enough money to start the project I should have a
good design that has been widely reviewed and possibly even built by other
people. In one of my posts I asked what CAD program is widely used by the
members of this list and obviously this list has never gone down that path
before but the reason for asking was so the design that is generated can be
reviewed and tweaked by a maximum number of people. The DARPA Grand
Challenge was a HUGE undertaking but you weren't restricted by cost per mile
where here by choosing to go electric and with a budget under $10000 makes
one critical decision for us, Lead Acid batteries. Some other list member
put it best when he said that to have a truly practical Lead Acid powered
electric car the car has to be lighter than the batteries. You can't do
that with any affordable production car as the steel body weighs to much.
Interestingly enough my preliminary analysis has shown that converting a car
is just as expensive to do as building one from scratch due to the lower
amperage rated components in the scratch built car. (One ESTIMATE shows I
can put a minimalist vehicle together for $4000 which should cruise at 70mph
with a 50 mile+ range) Also the motors appropriate for a conversion are
actually to heavy and big for a from scratch build in my opinion. I may
ultimately take a whole suspension from a donor vehicle like Sunrise does
but for the time being I am not designing it that way. If I had to build
one NOW I would go that way if not just straight conversion.

So to sum up I have far more time than money right now so the only thing I
can do is design the best car possible and hope that I can build it some
day. In a couple of years when my kids get a little older my wife will go
back to work which should free up the cash a bit to do something like this.
Until that day I just have to learn, design, relearn, redesign, repeat!

I respect anyone who even attempted that event and in fact I watched a
television show on that subject not to long ago. If I have the right
vehicle in mind your ATV was dark blue. That was hugely challenging but the
solution turned out to be largely a software solution with some sensor
challenges. If you had known the final outcome would you have done things
differently? In building electric vehicles we have many cases to study
including the EV1 which did many things right. The original EV1's that were
even shipped using Lead Acid batteries. So in reality this is MUCH easier
than the DARPA challenge as I am not doing something previously thought
impossible. There are people on this list that have what I want to build
and some of them even use a similar approach.

The long term challenge for us is making these vehicles so user friendly
that other people can use them and the EV1 did that.

There is a real possibility that by the time I am ready to start building a
vehicle a commercial entity will have put something into production that
meets my needs and so long as the price isn't out of line I may just buy one
and be done with it. But in life you can't always sit around waiting for
someone to build what you want so you start working it to see what happens.

Have a good one
Jeff



-----Original Message-----
From: D S [mailto:[email protected]]
Sent: Saturday, June 14, 2008 7:09 AM
To: [email protected]
Subject: [EVDL] Scratch Built EV (In theory)


I wantred to share my personal experience here. One of my other hobbies is
building robots (sorry nothing spectacular yet). For the DARPA Grand
Challenge 2005, I started with building a chassis from scratch. I wasted
many months, coming up with my unique design and chasing down hard to find
parts. I ended up buying a ATV to use as a chassis. Though I had done a lot
of work, I was not far enough along to qualify for the race. (Not learning
my lesson. I spent many more months fabricating tractor tread from scratch
for the next contest. I didn't apply for the next one.)

I think you are trying to do two things here. You are trying to learn about
Electric Vehicles. You are trying to learn to design chassises. Both are
good. Combined that would be great. However, in practice, you may want to
start with some prototyping projects. You could start with a bike. Get a
decent frame. Add a small motor, controller and battery. Use that to learn
about battery use, motor size and controller control logic. It should not
set you back much (a few hundred). In the end you will have a nice bike to
take to the store. On the larger scale, convert a used car. This will cost
several thousand dollars. The car frame will be your cheapest purchase. (I
just bought a 99 Sonoma PU for $1K with a bad head gasket. Most running PU
start at $2K (my Escort chassis only cost $200)). In the end, you will have
learned about EVs and have a decent motor, battery and controller to go in
you specially designed frame.

Please don't consider this as me trying to talk you out of what you are
doing. I am not. I think more people trying to make a better EV is the best
thing. I am just suggesting a path, that will allow you to meet you goals
without being overwhelmed.

Don

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----------



## EVDL List (Jul 27, 2007)

> The other question I have on Sunrise is in regards to the
> suspension sub frame mounting and what are you doing to prevent the
> core from being crushed and what steps have been taken to distribute
> the point load of the suspension mounting bolts over the whole
> structure?

That is a big concern in composite bodies. Solectria tried embedding 
aluminum tubes in the composite for their suspension attachments. There 
is considerable cracking around these tubes.

We chose to spread these forces out over a very large area, rather than 
let them concentrate in small bolt attachment points. The front 
suspension has about 1 square foot on each side. 

On cored fiberglas boats at the high load points the core is removed and the
void filled with fiberglas. The edges of this fiberglas section are tapered
into the foam on one side to avoid an abrupt transition.
-- 
View this message in context: http://www.nabble.com/Scratch-Built-EV-%28In-theory%29-tp17747933p17854866.html
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

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## EVDL List (Jul 27, 2007)

Flyin' Miata in Colorado sould be able to help you
with parts.




> --- Peter VanDerWal <[email protected]> wrote:
> 
> > > Anyone
> > > Suspension design. At this point I would say
> ...


----------



## EVDL List (Jul 27, 2007)

I was in Barnes & Noble this evening and the latest "Kitcars" caught my 
eye. For this beauty on the cover:

http://www.factoryfive.com/gtm/gallery/cheney/gallery.html

THAT would make an eye-catching, relatively light-weight EV.

$19k to get started:

http://www.factoryfive.com/gtmhome.html

--Rick

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## EVDL List (Jul 27, 2007)

I went through a list of all of the kit car builders I found on wikipedia
http://en.wikipedia.org/wiki/Kit_vehicle
Ultimately they all ended up being more costly than my goal. However since
many of them support VW and EV supports VW you can have an easy job building
one up. I think the most attractive thing I saw was one of the kits cars
but with the http://www.electroauto.com/catalog/ackits.shtml#ldirect direct
drive kit. However for the cost of that setup gas is going to have to get
REALLY expensive. I guess in my mind I am still shooting for lower cost.
I was liking this design the most though
http://www.sterlingsportscars.com/index/parts_price_details.html
oh and that is a source for fairly aerodynamic parts for those build from
scratch types like me! They sell DOT rated windshiels that may just work.
http://www.sterlingsportscars.com/index/Car_Pricing.html


-----Original Message-----
From: Rick Beebe [mailto:[email protected]]
Sent: Monday, June 16, 2008 8:01 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Scratch Built EV (In theory)


I was in Barnes & Noble this evening and the latest "Kitcars" caught my
eye. For this beauty on the cover:

http://www.factoryfive.com/gtm/gallery/cheney/gallery.html

THAT would make an eye-catching, relatively light-weight EV.

$19k to get started:

http://www.factoryfive.com/gtmhome.html

--Rick

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## EVDL List (Jul 27, 2007)

> Lee wrote:
> >>I have two big questions about building my composite chassis
> >>How to I estimate/plan the number of plies and core thicknesses needed to
> make
> ...


----------



## EVDL List (Jul 27, 2007)

> Jeff Andre wrote:
> > Lee,
> >
> > You might want to contact Alan Shaw in Florida. He's been working for years
> ...


----------

