CarBEN Model -- 1/24th scale model and 3D computer model for EV

[JethroBodine]

Good to hear about the progress, Neil. I'm looking forward to seeing some more pics.

Have you looked into "drill saws"? I know you have a plan, but I have seen titanium bits fairly cheap with a large side cutting edge.

[NeilBlanchard]

The RotoZip up-spiral bits I have will cut all the way through a 1" foam sheet in one pass, so I need to layout all the sheets to know how many I need to buy.

Unfortunately, I've been told that XPS (extruded polystyrene) is rather bad for carbon dioxide output when it is made. I'll have to use it as long as possible to make up for this... And I would love to find a foam with similar physical properties to Dow (light blue) XPS but without the major downside.

[NeilBlanchard]

Question for folks who have worked with composites: I'd like to find a "greener" type of foam to use building CarBEN EV5. I was planning on Dow XPS but I found out it is just about the worst in terms of input energy so it has a very big "carbon footprint".

It needs to be fairly rigid, machinable, and I'm going to use 1" thick x 2' x 8' square edged sheets (not tongue & groove). If it is biodegradable then that is good as long as it is not water soluble.

If I cannot find something better, then I will use XPS (because I can't let perfection be the enemy of the good!) and the best / only place I have found it for sale is here at a place in Texas -- which seems like along ways to have it shipped to New England!):

FRP Shop - DOW Brand Extruded Styrofoam Insulation

[2009Prius]

I suppose the insulation foam boards sold at HomeDepot are not good enough for the car?

[NeilBlanchard]

My local Home Depot does sell Owens Corning (pink) XPS 1" x 2' x 8' sheets, but they are tongue and groove edged, which means I lose some usable foam. It would be fine otherwise. I'm going to probably use the square edged sheets from the place in Texas, unless I can find a more local source.

[NeilBlanchard]

Here's a screen capture showing all the sections forward of the high point of the roof -- and showing the 2' x 8' foam sheet layouts above them. The 3D model in to the far lower right.



Now, I will start to do the same for the rearward portion of the chassis behind the high point of the roof. After I lay out all the sheets, I'll know how many foam sheets to order. :-)

[NeilBlanchard]

This is a progress image of the drafting work I am doing in DataCAD 14 of the sections of CarBEN EV5, in preparation for generating the g-code to cut foam sheets with my PhlatPrinter 3 CNC machine.

[NeilBlanchard]

Here's a progress image of the drafting I'm doing on my CarBEN EV5:




All of the sections have now been smoothed and fleshed out; and then each section has the next section behind it copied overlaying it. This is so there is always an excess of material on all sections, so they can be smoothed just by carving with no filling needed. And the rear doors are laid out flat by cutting a section parallel through them -- they are in a slight angle, so they form a flat V.

[NeilBlanchard]

I've reached a benchmark on the drafting -- all the sections are drawn in their finished form. The next step will be to drawing the jigsaw joints and lay out the pieces on the 2'x8' foam sheets -- this will take a while!

Here's a more detailed look at a sampling of the section starting just behind the high point of the roof moving back through the CarBEN EV5 chassis.


The different colors show the areas where the adjacent section behind adds material to the forward section. In other words, the tapered shape must have an excess of material -- because both the outside and the inside of the same taper.

I hope this makes sense.


These are the sections at the top hinge of the hatch door. I've started the interlocking lip on the door and the opening that holds the seal and acts as a water gutter when the door is open.

Also, note the 1/2" diameter alignment dowel holes -- these are modeled straight through the entire model. As the chassis tapers, I added other alignment holes.


These sections show the transition in side windows -- the 'C' pillar that is just ahead of the rear wheels. I'm intending the have 2 layers of glazing on the side windows and the hatch and door windows, to provide more insulation.

The section on the right has the front top of the hatch windows, near the center.

The two center rectangles in the floor are the battery bays. The vertical rectangles on the center and right section are for the rear suspension; which is probably going to be a trailing swing arm(s).


These section have the front pieces of the rear wheels and the wheel skirts. Notice the hatch window is getting wider the closer you get the back.

I moved the wheels to where they may fit more efficiently when cutting the foam. And the rear shock / spring units will probably be located here.


The rear wheels are attached to the chassis here, for the purposes of building the model so it can sit on the ground as the car will. After the chassis is (started?) to be fiberglassed, the wheels will be cut out and the suspension components can be designed and have the anchors affixed to the chassis.

The section on the right has voids for where a lateral link arm can be located. This will form a box beam across the floor between the rear wheels.


These sections are at the back of the rear wheels, and I moved them where they fit efficiently on the foam sheets.

I am hoping to be able to use the alignment holes as a wire chase, so I am cutting a connecting channel from the outer hols to the inner holes that pass through the section closer to the back.


These sections show the rear wheel strakes and the diffuser fins on the underside of the chassis. Also, I'm cutting a small area so the tail lights can be wired -- the small triangular holes at the "shoulder".

The rear exhaust air vents (that exit flush to the sides of the rear fenders) are shown in the section on the right.


These sections show the exhaust air vents and the end of the rear wheel strakes. Also, the hatch windows stops at this point.

This is the 'D' pillar and the outer edges of the rear bumper starts on the section on the right.


This is the very back of the chassis (nearly) and the section on the left has the rear door stops and the exhaust air vents. These are 1" thick sections because the taper on the very back is much "steeper".

The center rib on the hatch door will act as a supporting stop at the center of the rear doors. I also have added a small "dorsal" fin at the center of the hatch spine. This was not on the SketchUp model; though I hope to remake the SU model from these sections that is much smoother and much more complete as well with all of the interior voids included in the model.


I cut sections parallel through the rear doors, so these are true size and I'll cut them from the flat foam sheets, avoiding an awkward bit of smoothing. The red lines are the actual edges of the doors and windows, and the gray lines are additional material so I can form the jambs.

The rear bumper and roof "spoiler" trailing edges are a very wide chevron, to match the way the rear doors close.

[straight5]

Your design reminds me of this:


I like what you're doing.