Fiat 500 Forum banner
21 - 36 of 36 Posts

·
Registered
2013 500e
Joined
·
67 Posts
This is one of the battery tabs with a riv-nut installed. The riv-nut is designed for soft materials and fits an 8mm screw. I used this type of riv-nut because the hole was oversized.
I made spacers of 1" round ABS to fit between these tabs and the bottom panels. The length of the spacers was approximately 1.1", but varied to fit the space because the distance between the bottom of the battery and the tabs wasn't consistent.
Note the battery support next to the nut. It's approximately 3/8" vertically away from the bottom of the battery. This doesn't sound like much, but consider this: A flat plate is the worst aerodynamic shape there is, with a Cd of ~ 1.1 and this support piece has two flat plates. There are four support pieces like this down the length of the battery, and they can pretty much guarantee there will be nothing but turbulence entering any diffuser at the back of the car. The bottom panels both reduce drag and ensure there is clean airflow into the diffuser.
Hood Automotive lighting Automotive tire Automotive exhaust Bumper
 

·
Registered
2013 500e
Joined
·
67 Posts
This is one of the middle panels during a test fit, showing the screw fastening it to the rocker panel. The location corresponds with the relief space mentioned earlier, with the middle panel fitting between the rocker panel pieces. 6mm riv-nuts similar to the one above are fastened to the middle panel.
The majority of the screws are stainless steel 6mm X 20mm flanged button head cap screws. Most of them thread into riv-nuts in adjoining panels. The main advantages of these screws are: they won't rust, low aerodynamic profile, and a large flange diameter to allow for the oversized holes required for fitting parts.
Wood Water Asphalt Gas Road surface
 

·
Registered
2013 500e
Joined
·
67 Posts
This is the new front panel. It is now made of 0.120" ABS and is designed to integrate better with the car and middle panels. The new rounded front fits into the front bumper and bolts to existing tabs in the front bumper cover and a cross-bar that supports the bumper cover. It is shorter than the original; it doesn't extend all the way to the battery. All panels I made are approximately 3' long, which allowed me to make the main panels out of two 4'X8' sheets of ABS.
The gold things around the edges are riv-nuts for fastening to other panels. The offset pairs of holes near the center are clearance holes for the stiffening crossbar.
Rectangle Composite material Tints and shades Font Fixture
 

·
Registered
2013 500e
Joined
·
67 Posts
VERY NICE WORK !! 🖖 🙂(y)
Thanks! :)

Here's the top (car side ) of that panel.
Note the addition of a whole bunch of holes just below the top 5 riv-nuts. These connect to riv-nuts inserted in that square bumper support bar. If you look at the pics of my first panel, you'll see the bumper cover did not smoothly connect to the front panel. This really bugged me and I added fasteners to hold it down.
At the bottom of the pic shows how the front panel connects to the first middle panel. One of the panels has a intermediate panel that fits behind both panels. This connector panel has a bent up edge for stiffness and is glued and riveted to the main panel. Riv-nuts allow the other panel to connect to it.
Azure Rectangle Fixture Wall Material property
 

·
Registered
2013 500e
Joined
·
67 Posts
Next comes the first middle panel; this is the bottom (road side )
Like I mentioned earlier, these panels are pretty large. Front to back is 3' for the main piece; a bit longer for the connectors. The panel is 59 3/4" wide, to fit into the space in the rocker panel. The large cutouts are primarily for the lift access space. The space will be covered with an easily removable access panel.
Blue Hood Rectangle Automotive exterior Gas
 

·
Registered
2013 500e
Joined
·
67 Posts
Here is the top (car side) of that panel bolted to the front panel.
There are some details worth noting:
1) the bent up edges in the cut out corners help keep gravel, etc out of the panels. They are also very effective in stiffening the otherwise floppy ABS.
2) That steel piece near the top is also a stiffener. It's actually DIN mounting rail for industrial electronics; however it is a very stiff and light, low profile option. It's actually stiffer and lighter than similar sized pieces of aluminum.
3) the aluminum piece just below the steel stiffener is a hook, designed to fit between the battery support rail and the battery. There are a few places in the middle two supports where this is possible. Using this hook allows the middle of the panels to be securely fastened to the battery without modifying the battery or its support rails. In the final installation I glued on a rubber pad to keep the part from vibrating and wearing on the battery support.
To install the panel on the car, first slide one side into that gap between the rocker panel parts. Then flex the whole panel to make it narrow enough to fit into the opposite side. Once this is done, the engage the hook by sliding the panel rearward. The panel is now captured in place and a few more fasteners make it essentially impossible to remove.
Hood Rectangle Road surface Automotive exterior Asphalt


Here is a close-up of the stiffener and hook:
Note how the DIN rail is essentially a "hat section" with lots of weight reducing holes. The stiffener is necessary to provide a straight connection between the two pieces. It also has to be low profile because the battery support is only ~ 3/8" thick.
Also note how the riv-nuts are slightly different than the other ones I'm using. Again, this is required because there isn't much space to work with.
Both the stiffener and the hook are riveted to the ABS panel. I'm using 3/16" heavy duty pop rivets; no glue.
Hood Wood Automotive exterior Asphalt Road surface
 

·
Registered
2013 FIAT 500e
Joined
·
3,158 Posts
NICE details for future builders. It will improve acceleration too, since even 0-30 is mostly at fairly high-drag speeds.

Please send pics of the car's whole underside.
 

·
Registered
2013 500e
Joined
·
67 Posts
NICE details for future builders. It will improve acceleration too, since even 0-30 is mostly at fairly high-drag speeds.

Please send pics of the car's whole underside.
This did add a bit of weight; it weighs about 30lbs. However, it's low (location) weight, which should help lower the already low Cg.
I'll get to the underside; I was planning to show the other parts and some of their construction.
BTW, I've added some background aerodynamics information that might help people in posts 16 and 17.
 

·
Registered
2013 500e
Joined
·
67 Posts
Well ****, I screwed up. I had intended to post a pic of the middle back panel, but I must have forgotten to take a pic of it before installation.
Suffice to say it's very similar to the middle front panel. The overall length and width are the same. The cutouts for the lifting points are similar; shorter and the same width.
It doesn't have the DIN rail stiffener. But it does have two "hooks" rather than one.

One important detail is that there's an inflection point at the battery before the channel for the suspension cross beam. If you put a straight edge between this point and the very back of the battery, there is a 2.5 degree angle with respect to ground.

There is also a stiffening rib at this point running across (left to right side) the battery pack. I had convinced myself there was nothing in the rib; it sounded hollow. I also watched the teardown of the battery pack video to verify my guess. I thought it would be clever to put some riv-nuts in this rib to hold the panel.

DON'T DO THIS!!

Attempting to put riv-nuts in this rib was one of my biggest mistakes in this project. First, it is not empty - part of the batteries themselves fit in this rib. I ended up spending a LOT of time drilling multiple holes trying to miss those battery parts. Yes, that's holes in the steel battery pack. Complete insanity!

A little later in the project (I'll show pics) I found some studs that are intended to be bonded to surfaces. These studs worked out great, and I would use them as an alternative.
 

·
Registered
2013 500e
Joined
·
67 Posts
Here are some early fit checks of the diffuser. I tried to make it as wide as possible without interfering with the suspension. It's about 43" wide, limited by the the shock mounts.
As you can see, it gets very close to the shock mount and the spring perch overlaps. I was very concerned that a topping out suspension would hit the diffuser, and had plans for limit straps, etc. Fortunately the shock's travel limit (for the Bilsteins) is enough to keep the spring perch from hitting the diffuser. In this photo, I had disconnected the shock to test suspension travel limits.
Automotive tire Motor vehicle Tire Bumper Vehicle


Here is the diffuser in an early fit check, supported by buckets.
Water Automotive tire Hood Motor vehicle Bumper


Here is the diffuser from the back. The blue tape lines indicate the centerline and locations for future guiding vanes. Note the lumps in the diffuser at the front of the guiding vane lines. These lumps fit the stiffening ribs that run fore-aft on the last part of the battery. In this case, the rear of the diffuser is bolted directly to the back panel with all the holes in it. The angle relative to ground is about 13 degrees. I think this is too steep, and will add some spacers to reduce the angle in the future.
Also note that most of the flat panels have been installed. You can see a mostly flat bottom all the way to the front of the car.
Hood Automotive exterior Vehicle Aviation Aircraft
 

·
Registered
2013 500e
Joined
·
67 Posts
Here is the suspension-diffuser clearance with the shock bolted in place. As you can see, there is no issue with suspension top out clearance.
Also note the aluminum bracket in the center of the picture. A stud is bonded to the battery pack using 3000 psi epoxy. There are three of these brackets on the back part of the battery pack. Two brackets like this are connected to the side of the main part of the pack. You can see one if you look carefully under the spring perch.
Tire Automotive tire Hood Tread Synthetic rubber


Here is the cavernous space between the battery and the back of the car.
Automotive tire Motor vehicle Black Bumper Automotive design
 

·
Registered
2013 500e
Joined
·
67 Posts
This is the front panel with all the bolts connecting it to the bumper cover. It seems like overkill, but all these bolts were necessary to keep the bumper cover securely fastened.
Note there is no air dam. I want air to flow freely under the car. There will be some small deflectors to encourage the air to flow around the front tires.
Tire Automotive lighting Vehicle Automotive tire Hood
 

·
Registered
2013 500e
Joined
·
67 Posts
These are the details for coving the lift points behind the front wheels. The left & right sides are pretty similar.
The first part fits behind the inside fender liner. It provides a straight bottom between the rocker panel and the rest of the car bottom. There's an angled tab that bolts & screws to an existing inside side cover (on the left side of the pic) This piece is thermoformed to fit the odd curves of the inside of the fender. (upper left of pic) At the bottom, it's riveted to an aluminum angle for stiffness & strength.
Fixture Wood Composite material Gas Bumper


Here's that part, looking from the inside forward. The bottom cover fits into the space between the rocker panel parts (on the left) and bolts w/ two bolts the the middle front panel on the right. The main purpose is to shield this area and the underside from dirt. Aerodynamically, it's not important because the space behind the rear wheel is very turbulent.
Automotive tire Bumper Automotive exterior Gas Automotive wheel system


Here's the cover plate bolted in place. The inside and trailing edges are bent a little to provide a clean edge and a bit of stiffening. The forward edge (right side of pic) is bent up 90 degrees to fit against the inside fender liner plate. The outside edge fits in the space between the rocker panels. The two bolts shown in the pic are the only fasteners necessary. This cover plate is reasonably easy to remove/replace when the car is on the ground.
Hood Automotive exterior Rectangle Bumper Gas


Here's the leading edge of the complete assembly: I may try a bit of foam to seal the leading edge if there's an issue with water/dirt intrusion.
Bumper Automotive exterior Gas Fixture Composite material
 

·
Registered
2013 500e
Joined
·
67 Posts
That cavernous space above the diffuser needed to be covered in the rear fenderwells. Obviously if it was left open there would be a huge aerodynamic and physical dirt mess.
Here is some of the work on the passenger side. Note the passenger side and the driver side are not the same. The general design is the same, but the geometry is slightly different.

Here is the cardboard mockup. Note that even though I didn't show it, just about every piece has been mocked up like this. This part is one of the more complicated parts in that there is an offset from top to bottom, with the top fitting the existing fender liner and the bottom bolting to the diffuser. Toward the back there is a slanted zig-zag detail to fit the existing fender liner. On of the main differences between the left and right side is the offset in this zig-zag.
Tire Wheel Automotive tire Tread Motor vehicle


Here is an early fit-check of the ABS part. That hole above the part is for the existing fender liner attachment; it will get a separate cover plate. One of the things I improved throughout the project was my thermoforming skills. In the beginning, I wouldn't have considered a complex zig-zag like this; also the bend quality got better, with fewer ripples.
Grey Gas Tints and shades Auto part Automotive exterior


Here is that part, near completion. The leading edge (right side of pic) has a 45 degree bend that is parallel to the shock absorber. The relief in that bend provides clearance for the shock mount. All the bends in the part provide quite a bit of stiffness; no other bracing is required.
Wood Netbook Rectangle Gadget Hardwood


Here is the final part, riveted in place.
Automotive tire Motor vehicle Tire Tread Rim
 

·
Registered
2013 500e
Joined
·
67 Posts
The front of the fenderwell also needed some covering. The space between the tire and the rear swingarm is very narrow; about 3/8". In fact, when I first installed the new wheels/tires, I left the parking brake cable loose in the OE clamp. The tire nearly wore through! o_O I circled a prior screw-up in red... It is now fastened securely..

Automotive tire Tread Automotive exterior Automotive wheel system Gas


When I first considered a solution for covering this area, I thought something flexible, like the rubber I used in the front. However, I found a thin 1/16" thick piece of ABS carefully formed would just fit. Some careful forming ensured it would not rub on the brake cable or swingarm.
Automotive tire Motor vehicle Bumper Automotive exterior Gas
 
21 - 36 of 36 Posts
Top