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

[NeilBlanchard]

Thanks! You ask some good questions - I'll try to answer them.

The symmetry of the cut sections was pretty good, and overall symmetry is probably decent - but I know that the gluing process was not as precise as I would have hoped. I have started the process of adding horizontal temporary braces across the hatch opening. And I need to find a way to align the hood and hatch door as they are glued up.

The long sanding board is allowing me to smooth over "pinches" and bulges in the chassis, and I think that any remaining asymmetry will be fine for this prototypes purposes. I am finding that the hardest things to deal with is forming the overlapping joints on the hood and the hatch door (and to a lesser degree, the rear wheel skirts, probably?). A lot can happen to a 3D form along the way - but the fact that I am able to transfer the virtual model into a real full sized version is all I could hope for.

The sides are basically solid - the only holes are the 1/2" diameter one for the alignment dowels; and the short exhaust air vents in the back, and the small wiring "junction box" a few inches from the taillights.

There are several areas of the car that would have benefited from a different orientation of the foam sections. I debated turning all the sections in the hood area 90 degrees (leaving the outer face of the fenders as is). And yes the fins would have been straighter if they had been added in later. I ended up having to correct the location on a few because of errors introduced by the CNC machine slipping (which may have been early signs of the X-axis motor wearing out?).

In the end, there are definitely much better ways to layout the foam sheets so as to both reduce waste and to simplify the shaping and smoothing process. But I had to do it in a way that I could keep a good handle on - as it was I had to cut some miscellaneous pieces near the end because I had skipped them, and I had 2 or 4 "extra" parts that I had duplicated.

You are right to focus in on the battery bays - I want them to be long structural 'U' channels, and the ribs would be easier to do in a way similar to the fins. The outer shell is the raison d'être of this design.

I had modeled the outside, and I put the battery cells inside the floor with some space for the structure. The battery bays themselves were added during the 2D drafting process by offsetting the edges of the cells, and then filleting the corners. It may well be that I end up using battery cells that are smaller or more easily packed into a tapered space, but with the cells I designed around (that are 10.5" x 5.5" x 3/8") would have not allowed for more structure below the battery; given the aerodynamic requirement to have the underside of the car slope upward.

The inside radii are proving to be a pain for the shaping and smoothing process. I'm going to need a good oscillating saw very soon for some other other areas. Hinges for the hatch door and the front wheel skirts need to be fabricated. The hood I think will be held in place by quarter turn fasteners - I can duck the need for hinges there, for the moment I think.

[chrisgerman1983]

wow this is really an amazing build! I have never really looked over it before. I cant wait to see more!

[cRiPpLe_rOoStEr]

Originally Posted by bennelson

Nearly all EVs are "Fly by Wire", using electric components to send signals. That gives more design flexibility. No reason why a car couldn't be designed with a foot pedal, but moving just one potentiometer and a pair of wires to the dashboard makes it a hand-control.

That's a good point with the EVs. But it's not restricted to them, it's also used in some vehicles adapted to disabled drivers.
http://www.emc-digi.com/site100-01/1...&SS=&Ver=0&W=M

I also like the idea of a separate pedal for regenerative brakes. On my hybrid truck project, I'm leaning towards separate accelerators for the engine and electric motor systems, as this maximizes the driver's control. Any sort of computer-controlled or automated system does not take into account all driving situations, whereas the driver can.

Instead of a 3rd pedal, why not a steering wheel-mounted secondary accelerator for the electric drive? That would prevent some confusion if you'd ever lend the vehicle.

[Galane]

For shaping the rabbet style lip joints around the hood and hatch, here's what I'd do.

First, figure out the depth of the cut from the outer surface. Cut a short block of wood that thickness.

Second, figure out the width of the lip and cut the block of wood to that width.

Third, Connect two boards together in an L shape. Cut the boards to the same length as the block, but a but wider so that when the block is placed into the V of the boards they project past it.

Fourth, clamp the block into the V of the boards drill a hole through the block and one board. Insert a teenut in the block's hole. Counterbore the hole so the teenut flange is flush with the surface.

Fifth, wrap sandpaper around the block, poke a hole through the paper on the side opposite the teenut then bolt the block to the L boards.

Now you have an automatic depth gauging rabbet sanding block. :-)

With some modification this design can be used to carve the rain gutter you'll need along the sides of the hatch. You'll also want to make certain to have room for a closed cell foam weather seal around the hatch. There are a wide variety of shapes of automotive weatherstripping available in bulk rolls. Check with RV and boat suppliers.

[NeilBlanchard]

Any chance you could sketch this sanding block? I am close to getting is, but I'm not clear on the L boards fitting to the block itself, and which direction the T nut is used.

Oh, and to answer one of your earlier questions - I will pay tolls with the EZ-Pass so no need to have an opening window for that.

[Galane]

Here's a quick 3D render. The purple part is what you wrap sandpaper around.

The green and red are held together. Nailed, glued, get fancy with dowels or dovetail joinery, stick them together in some sturdy fashion.

T-nuts need to pull inwards so you want to put it on one of the faces away from the boards.

You could also just put a couple of holes in for wood screws. Depends on how long lived you want the tool. Use a T-nut and bolt and build it with care, could hand it down to your grandkids. ;-)

Of course to make a straight/smooth rabbet, the areas the boards ride on have to be smooth.

Another way to do a rain gutter for the hatch would be to first sand the rabbet with this tool then glue a strip of foam on the edge before glassing.

Make a mock up by gluing up a stack of your scrap foam to use for practice. Get some lengths of hood and hatch edge perfected and glassed so you'll have your technique debugged before doing it to your laboriously constructed and $$$ invested vehicle shell.

[freebeard]

The inside radii are proving to be a pain for the shaping and smoothing process. I'm going to need a good oscillating saw very soon for some other other areas.

Is this the problem you asked about in #post324285? I looked at oscillating saws in Google images and in addition to jiggler saws and Sawzall, there is a medical style. It looks sort of like a powered putty knife. A knife blade might cut cleaner than a saw blade. I know that's the case with corrugated cardboard.

I had to read Galane's description twice; but I got it, as his render confirmed. What I'm not seeing is why a router drawn along a straight edge wouldn't be quicker. A router is a high-speed tool and should leave an acceptable surface on the foam.

FYI the pictures in #post336352 no longer load.

[NeilBlanchard]

I fixed the broken picture links in the earlier post - I'd forgotten to do that after I moved things around on Photobucket...

Thank you for the 3D image of the sanding block. I need to do something like that, but I need a lip for a rain gutter. I have a large plunge router and a small rotary tool and I may try to come up with a guide collar for the rotary tool to shape the edge. There needs to be enough space to get the latches in there, too. I like the idea of a slightly flexible strip of wood that can be clamped in place as a guide.

[zoltanbod]

Originally Posted by NeilBlanchard

Well, I hope you are patient. This will take a year, or two or maybe more.

I have to buy ~68-75 more sheets of foam (depending on how many "extras" I need), and then the real fun begins. Fiberglassing the inside and the outside, fitting it with suspension and wheels (likely custom rear suspension?) and working out the steering and the connection to the hinged front wheel skirts, buying at least the windshield and wipers for a Smart ForTwo, putting in the driver's seat, working out hinges and latches for the rear hatch and rear doors -- and THEN building the battery pack (hopefully around 50kWh+) and the drivetrain.

I can relate, patience is a virtue. Your project is a long and arduous jorney.I wish you much success.

[ron]

what a commitment I am having trouble just making a aero nose and you are building ground up ! Inspiration 1