CarBEN EV5 Full Sized Prototype Construction - 5 Seat Electric Car From Scratch

[TheSGC]

Originally Posted by NeilBlanchard

David, we should get together! I'd like to see your Civic, for sure.

Once I get my new motor for my Civic we can compare notes!

[NeilBlanchard]

I've spent this very warm day (close to 60F) to full advantage, working on rough shaping the inside of CarBEN EV5. Lots of chunky bits from the Surform tools followed by rough sanding with the random orbital 5" sander:

[Smurf]

Incredible. Here's hoping that David doesn't have much else to do, and is more than willing to help you finish this.

I'm impatient

[freebeard]

Those A-pillars, and the low-res jaggies in the B-pillars look challenging. I can't remember if the finish contours are 100% inside the foam.

Maybe poke a curved welding rod through there for a fulcrum for your tool and to protect the crown of the contour?

Were you to do it again; do you think cutting from sheets that are 2" down to 1/2" for different areas would save hand finish work?

[NeilBlanchard]

Those jaggies are not hard to cut out. I spent months doing drafting work and even to go to 1" layers would have doubled the drafting time. Half inch layers would have quadrupled the drafting time and doubled the cutting and gluing time.

If I do it again, I'll model a "box" on the inside made from the aluminum honeycomb composite panels, and then glue foam only on the outside. Basically exactly what the folks building the Trev did.

[freebeard]

I'm impressed by their methods too.

There are a lot of interesting composite laminate materials. One source is NUDO® Wall, Ceiling and Sign Panels, Flooring and OEM Products - Springfield, Illinois. Under signage they have Polymetal, which gets used for unstressed panels—the big wings on dirt track modifieds. Under Transportation products they have Plymetal, which has 5/8" plywood for the core.

But the aluminum/fiberglass material the Trev folks used probably has the best strength/weight ratio. How about a self-skinned aluminum foam for the critical areas?

[NeilBlanchard]

Today I worked on the hatch door opening - I had glued up a couple of pieces of wood and glued the 120 grit sanding belt onto two surfaces yesterday, and it was dried and ready to use today. Once the straight edged recess was started, I used the disk sander to move it along quicker, and then finished it with the sanding block. I also laid out the recess at the hinge end of the opening and radiused the opening, too.

[freebeard]

I was going to ask what the ratio is of the original 2D layout resolution vs the 3D spacial resolution of, for instance, the forward corners of the rear wheelwells. Are they within 1/10th or 1/4" of where they should be? Less than 1/10th" in the original layout?

That's one big opening. Is the rear bulkhead going to be a ginormously stiff U-shape?

And what did you think about foamed aluminum for the suspension attachment points? At the link they quote $2 to $500/lb for finished parts, so the first number is probably close to raw material cost.

[NeilBlanchard]

The relative 3D positioning in the foam core is very close to the original 3D model. The CNC machine was usually accurate within 1/16th of an inch, though some pieces were off by as much as a 1/2". But the variations are almost completely "averaged out". The overall length of the foam core "grew" a little in length because I had measured the thickness of the nominal 2" foam at about 1 15/16ths of an inch, while the 1" foam actually was about an inch thick - and there is twice as many glue joints, too. A longer car is actually a good thing.

You can kinda' see my edge shaping tool in the first three photos, by the way - it's the one on the left.

[freebeard]

Do you do diagonal measurements? I would think the greatest opportunity for distortion would be in torsion around the longitudinal axis.

[that was a 20 minute response time. Answer at your convenience. ]