Tres Chic

The rear support for the Upper Battery Tray is done.  It joins the rear of the tray to a rectangular cross piece that ties the frame rails together.  The piece required about 105 degrees of bend, which my tooling is not able to do, so I had to fudge the last 20 degrees. You can see where it doesn't sit flat along the cross piece, but through the miracle of modern coping techniques, I will live with it ( 1 deep breath and repeat "not everything can be perfect" 10 times).

The rear support piece requried four bolts thought the rectangular section, where I had previously mounted the controller.  So I will need to figure out how else I mount the controller and ther rest of the electronics.  Another goofy thing is that the whole tray seems to be skewed to the left side of the frame (look where the support joins the tray), but I can't see what is causing that, except that front frame rails are not exacly parallel.  The good news is that there is plenty of material on the rear tab of the tray, and you need to allow for such variations in a kit.

My lithium pack models fit fine on the tray.  The cardboard models simulate 12 Thundersky 60 AH batteries in the upper tray and 8 in the lower tray, giving an approximate 60volt setup.  I designed the trays to have enough room for Lithium Modules made of 5 units.  The model batteries were originally made to simulate modules of 4 batteries, but ended up too long by almost 1/2".  There should be enough room to squeeze in 24 cells, for an effective 72v system, but it's going to be tight in the back of the tray.  I can worry about that more when I can afford the lithium batteries.

Tres Magnifique (almost)

I got the upper battery tray cut and bent, but ran into a few hiccups in the bending process

After bending the front and rear tabs, the part will no longer fit into my bending brake, so I ended up finishing the bends in a vise.  The bends forming the side tabs are not uniform and the flat area where the batteries are supposed to sit is distorted.  The good news is that this piece is functional.  I will need to make a few changes to my tooling in order to accomodate future versions. 

I've also come to the conclusion that 3/16" stock is just too thick.  On version 2.0 all pieces will be made from 1/8" material.  This will help reduce the raw material costs and will be a lot easier to work with.  It also will save a little weight.

Fun with Paper & Glue - Upper Tray Begins

(Editorial note: this entry is for the absolute beginner and my documentation.  Experienced EV builders can skip this one)


In working with the sheet metal pieces, I've developed a system of modeling and checking fit without having to cut metal.  It's pretty common in the EV world to do Cardboard Mockups, but here's my take on it for sheet metal.
Model the sheet metal part

Print a full scale version of the flattened 3D model. In this view the flattened model has the bend lines and some additional construction lines to indicate where the curved surfaces will start, since I'm creating sharp creases, rather than gradual bends like the the actual part.

 Use spray adhesive to adhere the Print to some Posterboard and and trim the outer shape.  It's important to let the glue dry overnight while laying flat. When dry, use a straightedge to make straight creases along the fold lines.

Using the Posterboard model, I can get a feel for how things look and fit.  Obviously, it's a lot easier to make adjustments in paper.  This is the 4th verision of this particular paper part, and I'm finally ready to cut the real thing in 3/16 Aluminum sheet (5052 alloy).

Mounting the Shield

Finally got around to mounting the Shield.  I had planned to use the original motor mounts and have the bolts thread from the outside to the threaded bosses on the interior of the frame.  Problem is that the threads are lined up horizontally, and the surface I'm fastening is about 12 degrees offset.

I had to make a decisions to backtrack on the purely "bolt in" philosophy, but I figure anyone converting thier bike should have a drill and a grinder. I ground the motor mount bosses down close to the frame, but not too close as to remove all the welded material.  Then I clamped the shield into place and drilled holes slightly bigger than the existing threads (5/16"). The holes are perpendicular to the frame surface, positioned so the drill reamed out the threads at the new angle.

I then clamped the Tray to the Shield, drilled four holes, and threw in some 1/4" grade 8 bolts.  Eventually, I will probably use some stainless button head screws but, for now I like the looks of the gold colored grade 8 hardware.

Lower Battery Shield

My earlier misfortune with the plasma cutter turns out to be a blessing in disguise.  I had second thoughs about having relief holes on the frontward facing piece of the battery tray, because I would like it to protect the batteries from road debris and water.  This functionality prompted me dub the piece: "Shield".  I decided that using 1/8" sheet instead of 3/16" was accepble for the Shield, beacuse it's not really expsosed to direct flexing loads like the Tray. Even the 3/16" might have been overkill on the Tray, it's overly stout.

The  end result looks pretty decent, and even though it's 1/8" thick, seems plenty strong.  In hind sight, I would have liked the mating tabs between the Shield and the Tray to overlap a little bit more, but it's certainly functional.

I had intended to bend the top tab over at 45º, but I kind of like how it fits between the old oil-cooler mounts. The two piece design of the lower battery support system allows me to remove the Shield in order to load the batteries or perform maintenaince.  Now to drill some holes to mount it to the frame and the tray.

Beauty is Skin Deep

I had a slight malfuntion of the Plasma Torch in cutting the second piece of the lower battery tray.  The vertical axis was having problems lining up, but I decided to give it a shot.  Wrong move.  The torch made contact with the stock and drug it around on several moves.  I could only watch in horror as my precious 5052 sheet was sliced into semi-random chunks.

Time to order more aluminum sheet.

In the meantime, back to the cosmetic pieces.  The fairing is pretty trashed, but staying with my mantra of "use what ya got" for this phase, it had to be sanded and painted.  The sanding was complicated by several sloppy repairs of cracks with some nylon material that didn't bond well to the ABS.

The upper fairing turned out pretty decent, so I may even keep it.

Progress At Last - Lower Battery Tray

Buoyed by the completion of my new bending brake, it was time to tackle the big kahuna:  the Lower Battery Tray. 

Back to the plasma cutter I went

I crossed my fingers and held my breath as I loaded the swiss-cheese like sheet into the brake.

The first bend was one of the two longest ones - could the brake handle a 12 inch long bend? 

It held up like a champ, but the leverage required for the bend almost flipped my work bench over.

The icing on the cake?  The tray actually fits!

 

Of course this piece is only half of the lower tray.  A vertical piece will join the front of this piece to the frame, but that should be a piece of cake. Right?