Introduction: Mini Electrical Car - FTA Contest
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I gonna detail you the realization of a project that I had in mind for a moment :
Many people in Europe know the "Mini Austin", much less the "Mini Moke", let alone his little sister the "Mini Schmitt" (or Mini Hrubon) that would correspond to a shortened Moke.
There is a recent electric version of the "Mini Moke" called "Nosmoke" (translate "no smoke").
My project was to achieve :
_ a reduced version of the Mini Schmitt => Nano.
_ with an electric motor => No Smoke.
Hence the name of "NanoSmoke".
Step 1: The Choice of Motorization
I was initially interested in converting an alternator into an engine.
Interesting, powerful, but greedy in energy, and it was also necessary to add a transmission.
Then looking more specifically, I opted for "hoverboard" engines, you know a kind of electric skateboard 2 wheels.
These engines have many advantages: inexpensive, a good ratio weight / power, brushless, with a good performance.
Another big advantage is that the tread also provides direct frictional transmission, like the old French bike Solex.
So, I didn't have to design a mechanical transmission.
Step 2: The Electrical Diagram
The electrical wiring is quite simple and is easily found on internet.
I customized it according to my need (coupling, headlights ...).
You can also wire additional options in the controllers (regulator, engine brake, regeneration, low speed ...).
Each 250W motor is managed by a 350W speed controller.
I opened it to modify a resistor to give more output power, I roted peak consumption of engines that can exceed 2000 watts together...almost 3 horsepower !)
They are powered by a LiPo battery pack of 12S (about 45 Volts) and 5.2 Ah.
Step 3: Groceries
So I have to do the shopping to check the operating principle, and take into account the congestion for mechanical design.
Here are the main items to buy:
_ 2x 6" hoverboard motors (48V 250W).
_ 2x speed controllers (36/48V 350W) : https://www.ebay.fr/itm/36V-48V-350W-Electric-Bic...
They will be coupled in parallel (power and commands).
_ 1x throtle pedal : https://www.ebay.fr/itm/Electric-Bike-E-Bike-Scoo...
_ 1x 30A circuit breaker contactor : https://www.ebay.fr/itm/40-50-60-80-100A-DC-12V-2...
To secure the batteries from an overload (placed just downstream of the batteries).
_ XT60 connectors (female connectors on LiPo batteries) : https://hobbyking.com/fr_fr/xt60u-xt60-upgrade-ma... https://hobbyking.com/fr_fr/xt60u-xt60-upgrade-fe...
They will be used to make the beam.
_ 1x LiPo charger : https://www.amazon.fr/XCSOURCE-déquilibre-batteri...
Known and used by many modelists.
Power supply not included, see for a 12V transformer with 2, 3A.
_ LiPo alarms (one on each battery pack) : https://fr.aliexpress.com/item/F00872-1S-8S-Dual-...
The module "beeps" when the minimum voltage set is reached.
_ 1x wattmeter : https://fr.aliexpress.com/item/F00872-1S-8S-Dual-...
Not necessary but it will serve to check the total voltage, the consumption, the instantaneous power, and the maximum power.
Disadvantage : no memory, it loses its data as soon as it is disconnected.
_ 2x 6S LiPo batteries (22,2V - 5,2Ah) : https://hobbyking.com/fr_fr/multistar-high-capaci...
Very punchy, it's the most expensive item.
It is an investment so well maintained.
Step 4: Starting the Mechanical Study
The starting point of my study is the reference of the wheels that I will use.
This will allows me to set the scale in relation to the Mini Schmitt. I am going to take 260 mm diameter wheels with a sheet metal rim. They are equipped with a bearing hub, for a 20 mm shaft diameter.
I am a professional mechanical designer, I am used to use digital design tools (CAD).
This allowed me to fully develop the mechanics of the vehicle.
Here is a small 3D picture under design, such that the vehicle should be completed once.
Step 5: The Preparation
You can see here the main assembly drawing of the project.
You will retrieve it and all details drawings in the last step of the instructable.
It was necessary to calculate the flow of all references (square tube, flat iron ...).
I bought steel from the local supplier, and also recovered old construction barriers.
I specify that I don’t use a template, and only affordable tools :
vise, angle grinder, drill press, arc welding machine.
For small tools :
ruler, measuring tape, square heel, scribe, wedges of all kinds.
The bendings are made in the vise.
Step 6: The Manufacturing of the Frame
This is the basis of the advanced frame, with the rear wheel axle and the clevises for the front wheel flares.
You can see the slight inclination of the front wheel rocker caps, this creates a hunting angle and participates in the recall of the steering wheel in a straight line.
The study under computer allowed me here to position the angle of the steering column without protractor (angle / distance conversion).
Step 7: The Steering Column Bearings
Bearings are set up in the upper part of the steering column, and in lower part.
These are 6801-ZZ bearings (24 x 12 x 6), mounted in force in the outer tube.
Step 8: The Running Gear : Axles
Here the front axles ready to welcome their bearings.
The right axle with its bearings put under press.
I used the same 6801-ZZ bearings as the steering column.
2 bearings at the top for the axial load, 1 bearings at the bottom for guiding.
A spacer placed in the vertical tube is welded into a plug to hold the bearings in place.
Step 9: The Original Hubs
The front hubs are held at the rockets by an adjusted pinning.
These hubs, which came with the wheels, were very frails (thickness 1mm).
The flange of one of them was "torn", they were not intended for this use.
So I started to build beefier hubs.
Step 10: My Homemade Hubs
I realized then welded a 2 mm flange with a piece of tube D50x2 to accommodate bearings 6204-RS (47 x 20 x 14).
The inside of the tube was too fair (Dint = 46 mm), I scraped with a cutter to be able to put the bearings (Dext = 47 mm).
The bearings are press-mounted.
You can see on pictures the difference between my hubs and the original cheap hubs.
Step 11: Installation of the Motors
There is a pressure control system that plates each motor on the associated rear wheel.
Seen from below, a plate welded to the frame enters the flat of the motor shaft which prevents it from getting skewed. A screw allows adjustment of the engine pressure on the tire.
Strapping secures the motor shaft to the plate with 2 setscrews.
Step 12: The Steering Column (mobile Part)
I had to change the leg because I was wrong on the intermission of the holes, hence the apparent weld.
Lifter in place in the column.
Step 13: Axle Assembly
Here is the right axle mounted on the frame with its wheel.
In the first picture it is the original hubs, the second with the hubs "homemade".
A support washer at the top ensures that the load is applied to the bearing's inner ring.
The hub is in abutment on its inner pin.
Step 14: On Her Wheels
The entire front axle with the ball joints but without the tie rods (M8 threaded rod).
Step 15: Making of the Steering Wheel
1:1 scale printing of the unfolded parts, and tracing on the sheetplate (2mm steel).
Cutting with the grinder, bending (in the vise), and welding.
2 wooden strapping will be placed above and below.
Step 16: The Steering Wheel Stem
I made the same steering wheel as the one of the « Bidonette » of my son (another car that I realized).
I borrowed it these photos (red color).
The steering wheel stem is made and fixed on the column (with temporary pins).
Step 17: The Bumpers and the Safety Bar
The bumpers and safety bar are made from old construction barriers.
On pictures, the hoop is mounted with the 2 bumpers.
Step 18: The Batteries Compartment
Here is one of the batteries with its mini voltage threshold alarm (battery voltage limit : 3.2 V mini per element).
The battery box with in order :
_ 3x batteries 4S in series (or 2x 6S) with their respective alarms.
_ 1x wattmeter (control of the consumption).
_ 1x circuit-breaker of 30A.
It will be placed at the front of the vehicle.
Step 19: The Raw Bodywork
The bodywork is made of 10 mm plywood.
First of all, I defined all the panels to be cut.
I then made a nesting to optimize the cutting and minimize the falls of the plywood sheet. No less than 15 kg of wood will be needed.
The bodywork is divided into 2 major parts:
_ The "Base", is the floor of the vehicle, and the seat support.
_ The "Shell", which is really the main piece, comes to cap all over.
Step 20: The Bodywork "Base"
Here the Base begins to be mounted and adjusted.
Base completely assembled.
Step 21: The Bodywork "Shell"
Here is the Shell assembled and placed on the Base.
We can see the started dashboard, where there will be a switch to reverse the direction of travel, and a switch for the headlights.
The hood made in “creasing” (several close bendings) is placed on the bodywork to be adjusted.
Step 22: The Headlights
Fixings of the headlights on the front face.
Step 23: The Brakes
I have not yet discussed the subject voluntarily because the braking had to be provided by the magnetic brake motors (option to wire on the controllers).
I over-estimated this braking, it proved totally ineffective. At this stage, a simple solution was needed without much modification of the project. A tube will rub directly on the wheels by means of a lever.
The lever at a booster created with a bungee cord.
The tube that rubbed on the tire did not have enough friction surface, and the crampons of the tire generated a not-so-nice grunt.
Later, I added a flat piece of steel that optimized the braking.
Step 24: The Seat
I stuck polyester foam on 70 mm on a plywood board, then I covered it with imitation leather stapled on the bottom.
This set is nested on the Base, in this way the "controllers" part is easily accessible (placed under the seat).
Step 25: The Painting
After several tests of colors on computer, red is the chosen color.
All metal elements are primed and painted in glossy black (economic paint).
The wooden parts are sanded and then coated with polyester resin for moisture protection.
Places that will receive paint are coated with white polyester gel coat.
The Shell is covered with white gelcoat, and the painted Base is fixed on the rolling frame.
After 2 to 3 coats of red spray paint, it's the finished.
Step 26: Finishes
The dashboard sheet is in place.
Summary, it has only switches :
_ one for the direction of travel (forward / reverse).
_ other for the lighting of the headlights.
The tie rods are put in place and adjusted.
You can see the throtle pedal on the right (potentiometer).
As announced above, the steering wheel finished with its white color.
A small manual horn has been added on the side for more fun.
Step 27: Finishes
I printed the desired shapes on white paper.
This served me as a template for cutting tickets in a colored sticker film.
The small "NANOSMOKE" is for the grille, the big one for the back.
My signature "BY TANG" also for the back as a brand.
The big "Coca-Cola" will be for the hood (marking for the exhibit at a motor show on the theme of advertising).
A "Coca-Cola" wave for each side of the bodywork.
Step 28: Enjoy !
My little 4 years boy proudly driving the car.
My vehicle stand here on an old car show, in front of his big sister : the Mini Schmitt.
I hope that my accomplishment has you more and will give you ideas.
If you need any information, don’t hesitate to send me a mail : email@example.com
You can also watch my YouTube channel : Tang22300
Step 29: Technical Drawings
Here I let you the entire PDF drawing folder (.zip) to make all the parts and assemblies.
If you need precision, send me a mail to get it.
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