Introduction: Velomobile Three Seat Electric Car
Environmentalist? Give this a try!
The problem: Need exercise and local transportation
The first solution: Electric bike kit! (excellent parts from ebikes.ca)
The new problem: It rains here. A lot.
The second solution: A zero emission vehicle with a roof.
The plan is to make a car that is light weight and pedal powered with electric and solar assist.
For now this is a build log and collection of messy notes. I'll add more over the next few days until school starts again. Feel free to subscribe and check back in the spring (of 2013) when I hope to have the front wheels on.
Minirant: I was trying to sell my neighbour on electric bikes and she said "It rains a lot here". Which is true and it got me thinking; is it crazy that in our culture we use two tons of steel as an umbrella and call it normal? A tonbrella as it were. This vehicle is my first attempt at a more practical solution to the rain issue.
Step 1: Prior Art
This plywood car was called the Fauchet = faux + Mochet
Georges Mochet made pedal powered micro cars in the 1940~50s.
Mr. 1JohnFoster (from http://endless-sphere.com/forums/viewtopic.php?f=2&t=25315&start=30) made his Fauchet electric car out of 1/8" plywood using a stitch and glue boat building technique. http://fauchet.tripod.com/
Stitch-and-glue seems like a construction method that is quite useful: it requires no specialized tools, no mold (unlike fiberglass), little skill/experience, cheap materials. We'll find out shortly.
(Will add image credits once the notation system is fixed)
Step 2: Measure Driver
Custom made for a person like this:
inseam: 70cm = 27 1/2"
thigh ground to crotch barefoot 34 = 13.4"
shin ground to knee bump 43 = 17"
torso sitting ground to shoulder bone 56 = 22"
arm shoulder bone to palm fingers up, palm forward 56 = 22"
hips 41 = 16"
Step 3: Make Seat Mockup With Pedals and Measure It
Seat flat length (short so can extend later) 9"
Lumbar angle rise 22.5 run 13.75: arctan (22.5/13.75)= 58.5704deg
Thoracic angle: (from lumbar angle +10.305) = 68.9
Seat / back junction to BB center (critical!) 33 1/8"
BB center to floor: 10 3/4"
Seat junction to thoracic 11.5" along lumbar board (note thoracic board is 1.5" thick)
My leg clearances:
32 from floor knee height max (no clearance)
24 from floor max toe height (heel on pedal)
22 forward from seat junction much less knee clearance needed.
Step 4: Suspension and Steering Research Notes
Research different kinds of front suspension and steering systems.
J-arm seems to be intrinsically anti-roll bar like. Very simple. Maybe affects caster? Used in 1980s Odyssey buggies.
Double wishbone: heavy complex, takes up space, high performance.
Dunebuggy style: long straight lever with shock: very simple! Could be Mcpherson variant?
Macpherson suspension is most common in cars. Few parts, easier to work on, cheaper.
camber: negative camber is bottoms out
toe: front wheel drive toe out, rear wheel drive toe in.
body roll: run the shock from the outside of the arm to the CENTER of the car to eliminate body roll (according to SoCal dune buggies).
Step 5: Sketchup CAD
Draw it up and check for places where heels, knees etc. would hit the body. Revise to fit on plywood sheets.
Check for possible center of gravity problems. Put weight well inboard of a line draw between front and rear wheels.
Step 6: Flat Layout
Flattery is a Sketchup program that unwraps curved shapes but it didn't want to work on my ancient laptop so I unwrapped manually.
Step 7: Draw on Wood
After some trial and error I figured out it's best to plot points from a single corner. Eg. 35" down the sheet of plywood and 24 1/3" over from the edge.
I used a tape measure, a long T square and a long L square.
Step 8: Cut Out Shapes
Jiga jiga jiga.
Funfact: you don't need to drill a hole or start on an edge to start a cut with a jigsaw; just tip the saw way forward and eat into the wood like with a sawzall. This is sort of like a plunge cut.
Step 9: Drill Drill Drill
Drill holes along one edge to prepare for copper wire stitching.
Clamping identical pieces together and drill both at the same time to speed up the work.
The slightly harder part is drilling matching holes on the other piece of the seam.
Step 10: Wash Hemp
Most fabric comes new with starch sizing. This might interfere with the glue.
So I washed the canvas with a bit of laundry detergent. I hand washed because the edges were unhemmed.
The trick I learned from hand washing down sleeping bags is repeated rinses. Rinse until you're prepared to drink the rinse water.
Step 11: Stitch
Snip bits of copper wire and stitch up some seams. I started with the wheel well to make my mistakes since it's fairly hidden.
Step 12: Glue!
Prepare a rounded squeegee. I found a bit of 2" scrap wood, rounded it out and sanded it smooth.
Mix wood glue with thickener until peanut butter texture. I got a garbage bag full of semi-fine sawdust. Proper fine wood dust might have been better; my thickened glue rolled up and stuck to the squeegee a lot. I massaged the glue back down with my finger and it seems OK.
Moosh glue into seams covering the copper stitches. Smooth down with rounded squeegee (may need to give it the finger too).
Step 13: Trouble With a Thick Floor?
I'm using 1/2" plywood for the floor but it's way thicker than the doorskin I'm using elsewhere. I'm concerned that when I bend the floor and stitch it to the walls, the stitches will tear right out of the walls as the floor tries to spring back straight. Maybe I'll cut an arc in some lumber and screw the floor to that to hold it's shape at least until the seams are stitched, glued and taped...
Step 14: Bending Thick(ish) Plywood
Step 15: Stitch and Glue Some More!
This innovation using string opens up a lot of possibilities with different stitch patterns. It would be possible to lock the panels together in perfect alignment using a stitch where the string passes in between the panels.
To thread the string, I used a needle of sorts made of some thinner steel wire (the wire used to tie rebar together in foundations) bent in half. This pinched onto the string and held it nicely.
Step 16: Reshaping the Nose (Rhinoplasty)
Step 17: Glue AND Tape at the Same Time!
Yes, I'd forgotten some sage advice from Mr. 1JohnFoster: Lay your fiberglass on BEFORE the fillet filler is hardened. This lets you squish out air pockets more easily since they fillet won't have cruddy divots solidified in place yet.
This is especially important since I can't see any air pockets because I'm not using fiberglass tape. I'm using strips of hemp canvas instead. This canvas is not transparent when wet. Also I'm not sure how well it wets out with the goopy glue I'm using so I mooshed lots of glue on both sides.
I used 10 oz hemp canvas.
I cut the canvas into 3 1/2" wide strips.
Hemp sack material might have wetted out better.
Step 18: Glue Heater Cocoon
I'm using Tightbond 3. It's cheap, sort of waterproof, easy to work with and stench free, plus it's non-toxic. Way nicer than epoxy.
The only drawback is it needs temperatures above 8 deg. Celsius to cure properly. So I put a heater in the car and covered the whole thing with three layers of plastic. I made sure the plastic would be a safe distance from the heater. This should hopefully ward off any frosty temperatures at the glue cures overnight.
Step 19: Wheelwell Redesign
I wanted a stronger wheel well. The one I'd made had all straight pieces so it lacked rigidity and probably couldn't be sat upon. So I've designed one with each piece curved to give it stiffness. The trouble now is that it has so many dimensions, it's bogging me down... first world problems.
Yeah this wheel well's a bit gross. Oh well.
Step 20: Aligning Pedals?
Step 21: Pedals Aligned?
Step 22: Chop Off the Slack!
Step 23: Practice Welding
Because I'm not a very good at it yet.
Step 24: Weld on Crossbrace
Now the pedals can go 'round and round.
Step 25: Gear Up
And I've busted out an early-release second generation Stokemonkey motor. I should install that before I put the wheel well in...
Step 26: Front Wheels and Suspension Materials
It was hard to find the parts to make a 20" wheel with a disk mount. I wanted smaller wheels to withstand lateral loads. 1JohnFoster used 26" wheels without incident but I wanted to err on the side of caution. He also kindly gave me some parts including hefty hubs that will probably make their way onto a recumbent trike at some point.
Step 27: Front Struts
I'm making these from $#!++y shocks from a mountain bike but they're going to be too wimpy. It would be better to use proper struts or at least motorcycle front shocks.
I had to shim the shocks with a bit of flattened mild steel wire so they'd fit tightly.
There are two sizes of 1/4 inch taps. Use the correct one.
Step 28: Disk Brakes
Breaks on a bus, brakes on a car
Breaks to make you a superstar
Cause I'm Kurtis Blow and I want you to know
That these are the breaks...
Step 29: Motor (Start Small)
Step 30: Reglue Redo
Also the problem probably originated from a slight alignment or tension issue which I think I also corrected by chopping and resetting the upper seam just behind the seat... hopefully.
Step 31: Beef Up Strut Connection Area (and Clamping Using Magnets)
I got the magnets to make a Hugh Piggott style wind turbine generator but I haven't built that yet...
Step 32: Redo Wheelwell (again)
This time I braced it in place for a few days whilst the glue set deep inside the fillet. It worked
Putting the wheel well in also required some butchery.
Step 33: Shock Tower Side Panel Bracket
Enter the $5 sheet metal from the scrap yard.
I made a little tap jig to hold the tap perpendicular(ish).
Before painting, wash metal with dish soap and water before painting in order to remove oil etc.
Step 34: Seat
Step 35: Trunk
-Maintain the curved shape of the rear panel after having chopped out the trunk hole. I
-Reinforce the trunk hood and coping.
-Easy placement of stops for the trunk to close against.
-Proper clearance for the bottom to swing inward.
-Comfortable sitting position for passenger in rumble seat.
I think I've done it. I took some measurements (see video) and laminated two oversize pieces on the inside with my fancy magnet clamp method. I also put some screws through the cut line to act as clamps.
I also used the excellent nail-in-a-drill method. I did this to make little guide posts to line up the panels as I glued them in place inside.
It worked out pretty nicely. I cut the trunk hole with a snap blade knife since it's really thin. This gave a pretty clean cut. There were a couple of unglued spots in the upper corners that I'll have to fix somehow.
I beveled the cut on an angle to make a natural stopper.
Step 36: Wishbone Front Bracket
A little trigonometry never hurt anyone. Well sort of... Anyway, I trigonometrified the placement of the front wishbone brackets. The challenge here was to make them pivot on the 11 degree forward rake that I'd designed the struts for. The result was a choice; do I have a thing sticking way down to get smashed when I roll over a protruding rock or do I have a thing that sticks way up and is harder to mount?
I chose to have a bracket that cantilevers up from under the car.
Step 37: Wishbone Connection Bolt at Bottom of Strut
I needed a 12mm bolt to stick out of the bottom of the strut. It needs to be coaxial with the strut so it will rotate as the wheel steers rather than force the wishbone in weird ways.
I thought of using an aluminum plug to fit up in the bottom of the strut which I could then thread to accept a bolt but I worried that such a bolt might wiggle out since it is rather hidden. Instead I made and attached a U shaped bracket and threaded this so I could screw in a bolt from the inside such that it could never fall out.
Step 38: Front Swing Arm / Wishbone
And here's a neat way to extrapolate holes from an underlying piece:
Step 39: Door
Funfact: materials stressed by flexing have most of their load concentrated on their surfaces. The concave side is under compression and the convex side is under tension. Any discontinuities on the surface can concentrate stress at this discontinuity. For example, this is why takeout sushi soysauce packs have a little nick in the side so you can tear 'em apart easily at this discontinuous place. Also, polishing the surface of a material significantly strengthens it probably due to less microscopic nicks.
In light of the above fact I put a continuous horizontal strip of doorskin on the top and bottom of the door and frame.
Also the driver's side has no door but still needed to be beefed up in case someone silly leaned on the window sill.
I ran out of clamps and magnets so I used this awesome pipe clamp trick from Tim Anderson.
Step 40: Steering (temporary)
A short push-pull cable steering system may work nicely. I got a 10 foot cable since that's all they had in stock. A 7 footer might have been better. Bear in mind this steering system will probably have little or no self centering steering.
Step 41: Test Ride
Step 42: Belt Drive CVT
I've had a lot of trouble with my chain drive falling off; I knew I would but I had to start somewhere right. Enter the belt.
Yes, belt drives have ~95% efficiency according to the internerd. They are also cheap, quiet and tolerate misalignment; ie. they're ideal for someone of my purposes. Also they are handily conducive to a nice continuously variable transmission. I thought I had one from my buddy's dead scooter (that cost a bottle of wine and a few bucks)... a look inside revealed that this was a single speed belt drive. That's fine, I'll just have to get creative.
Listen to me get confused in the video above when I still thought this was CVT and not single speed.
Step 43: Shorten Front Swing Arms, Bigger Shocks
Needed to shorten the swing arms in order to bring the axles 5.5 inches inboard. Pythagorean theorem to the rescue.
Also needed beefier shocks shoehorned in which is kind of an involved process.