LITHIUM
HAWK 

by Nap Pepin 

 
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  Introduction - Page 1 (Last Update - September 19, 2012)
 


September 22, 2011

Welcome to the Lithium Hawk electric vehicle (EV) website.  My first EV project was the Lithium BugE.  You can read about it here.  The Lithium BugE was an educational and successful project for me with specifications that met my design goals.  It is now in the care of the Reynolds Alberta Museum and is fully functional.  This new vehicle will outperform the Lithium BugE but will take a lot more effort, time and money to complete.

Like the Lithium BugE, the Lithium Hawk will be configured as a reverse trike and equipped with a powerful and efficient AC drive system powered by lithium cells.  Thereafter, the similarities are fewer with the Lithium Hawk designed and built to be technologically and mechanically superior to the Lithium BugE. 

 

Below is the chassis of the Lithium Hawk certified, insured, registered and licensed as of August 9, 2011.

See a short (36MB) driving video here. (you may have to right click then select "save target as")

 

   
     
     

The Lithium Hawk as of August 2010
     

I built the Lithium BugE with the best and most advanced technology that I could get my hands on, understand and afford. It was propelled by an efficient AC motor powered by prismatic lithium iron phosphate cells.  Besides being able to tune the highly programmable Curtis controller to optimize vehicle performance such as throttle map, torque and current limits, the most significant feature was variable regenerative braking who's purpose was to recover energy when braking, reduce wear on the mechanical brakes and provide better vehicle control.  I programmed the regenerative breaking to operate in response to the inverse of the twist throttle position.

The regenerative braking was so effective that I rarely used the mechanical brakes unless I required really hard braking. The vehicle achieved impressive performance numbers with a range of about 200km and an equivalent fuel economy of around 600mpg.  Those performance specifications are quite amazing to me to this day however they were obtained while sacrificing safety and stability.  The Lithium BugE only weighs about 400lbs,  has only a non structural fairing, almost no suspension and no safety features.   In addition, the brakes are minimal and the size of the vehicle leaves you feeling somewhat vulnerable.  It was fun driving the Lithium BugE but I learned that trying to make the vehicle too light has it's own problems, mostly related to stability in bad weather and at higher speeds.

The new vehicle will be significantly larger, have a fully enclosed composite structural body, be equipped with full independent suspension, hydraulic disk brakes and be much heavier than the Lithium BugE.  If you're wondering about the picture of the black 3 wheeler up top;  I found that picture long after I chose to make a tandem 2 seater and after I bought red and black racing seats.  It's a stunning vehicle and my vehicle may look similar when I am done.  I do like the color scheme and as such, I have had my wheels powder coated with the same colors.  It was both the name of the synchronous drive and the look of that concept vehicle that inspired me to choose the "Hawk" in the Lithium Hawk name.

 

On the left is the Lithium BugE at the Reynolds Alberta Museum.  This was my first visit to the Museum since I donated it.  Each May, the staff select their favorites for their annual show.  This year, they selected the Lithium BugE as their first choice.  It will be shown for 1.5 years before being rotated through their inventory.
 

Current State

I have been working on the project for some time now (about 1 year), and a lot has been done but I am no where near where I expected to be at this time.  As of this date when I have first posted this site, I can explain what state the vehicle is at; 

The rolling chassis is near completion.  It is an all aluminum frame equipped with a Honda Goldwing GL1800 shaft drive and swing arm.  It is powered by a high efficiency 70kw AC motor and motor controller.  An intermediate drive provides a 2:1 gear ratio for a combined total gear ratio of 4.75:1.  The intermediate drive is an advanced synchronous pulley/belt drive that operates at 98% efficiency using a Kevlar belt.  The Goldwing wheel is fitted with an ultra low rolling resistance car tire called a Bridgestone Ecopia.  The 17 inch front wheels are from a Kawasaki 600 ZXR motorcycle.  On them are oversized Metzeller high mileage tires.  The brakes are hydraulic disk on all 3 wheels using a hot rod CNC brake pedal and master cylinder.  There is a proportioning valve to balance the back to front brakes.  The brake lines are custom stainless steel braided lines.  The seats are lightweight Corbeau reclining racing seats on double locking sliders with 3 point safety harnesses.  The overall length is about 8 feet with a 66" front wheel base and almost 11 inches of clearance from the ground.  The rear shock is a hydraulic adjustable (electrically adjustable) shock to raise or lower the backend.  The rear shock bracket was modified to increase vehicle frame height (clearance) and to help meet the 700mm seat height requirement for motorcycles.

   
 

Test Equipment

70kw Motor

Steering Bearing

Secondary Drive

Mock-Up
The arrival of the frame
Frame Arrival

Brake Manifold

Side View

Rear End

Shock Bracket

Daisy and I

Cell Welder

Welder Guts

Lithium BugE

45 degree View

2000 K2 Cells

Battery Mock-Up

Front  End

Another View

Welded Bushing
   

Progress Made in 1 Year
 
  •  Purchased or built the necessary equipment:  This includes a large and powerful Lincoln Precision 275 TIG welder and the electrical service to power it, pneumatic tools, a tube notcher for cutting complex angles in metal tubing, load profiling equipment and milliohm meter to evaluate lithium cells and a capacitive discharge welder and pneumatic weld head to build batteries from cylindrical cells.

  • Completed a lengthy TIG welding course:  This was very challenging for me and one of the most difficult skills I have ever had to learn.  I practiced welding aluminum for many hours before attempting anything I needed to keep. 

  • Contracted the basic frame out:   I could not find a suitable frame to use but found a very talented fabricator named Kale Kotecki in the USA  with the skills and equipment needed to build a strong and lightweight frame.  I was responsible for determining the configuration (reverse trike tandem two seats), choosing the drive system, and determining key chassis dimensions.  This took several months requiring a lot of research, part sourcing and purchasing.  The front half of the frame was based on a single seat reverse trike frame the fabricator had built before.  I needed to choose and purchase the rear end, the motor and controller, seats, brackets and harnesses during this stage.  The rear end I chose was a new Honda Gold Wing GL1800 shaft drive and swing arm. 

  • Completed the rolling chassis:   Some rework of the front end was required to reduce tolerances and make improvements.  However most of the work was directed toward replacing a temporary motor sprocket and chain that drove a larger sprocket on the shaft drive rear end.  This was needed to obtain an overall gear ratio of 4.75:1.  I had no intension of keeping the chain drive.  It was loud and my experience with the BugE proved to me that chain drives have huge maintenance requirements.  After much research and using vendor supplied software to determine noise levels and components for various drive systems such as synchronous belts, gear reducers and V-belts, I was stuck for some time.  I was even considering the use of an automobile torque converter for its torque multiplying capabilities and even a CVT (continuously variable transmission).  Finally, I discovered a patented synchronous drive that had dramatically improved performance characteristics than standard synchronous drives.  It is a Goodyear Eagle PD Synchronous drive.  I'll talk about it a little later.  It is quite amazing.

  • Chose and purchased the lithium cells:  This was a very important and difficult part of the project to date.  In the Lithium BugE were Thunder Sky lithium cells that performed quite well.  My tests and experience proved however that those cells would not be sufficient for this vehicle for the performance I desire and the estimated weight of the vehicle.  I see a lot of people using those cells for a lot larger vehicles than the Lithium BugE (cars and trucks) and I am certain they are quite disappointed with the performance.  They have good energy density but do not have the ability to sustain high power output.  The Lithium BugE was very light and that is why those cells worked well.  I initially had the controller set to maximum power which required over 300 amps from the 24 TS-LFP90 cells.  But huge voltage sags occurred and would inevitably damage the cells so I ultimately programmed the controller to 180 amps maximum.  The vehicle was still peppy but I had to take it easy when the vehicle's energy level was less than 70%.  Those cells are rated at <3C continuous meaning <3 times their AH capacity in amps but in reality the cells should be rated at about 0.9C.  So if I wanted the lithium BugE to perform the same with the cells at almost any state of charge (i.e. 10% to 100%), the controller should have been reprogrammed for 81 amps maximum,

    With the above in mind, I was determined to find the best cells I could and test them extensively.  The cells would have to be able to deliver the maximum current of the controller at almost any state of charge.  After testing A123 Cells (2 types) and cells from K2 Energy solutions, I chose the K2 cells.

   
 
Comparing the Lithium BugE to the Lithium Hawk
   

Component/
Feature

Lithium BugE

Lithium Hawk

Advantage

Frame

Single plane steel rectangular tubing

Aluminum round tubing

Multi-plane aluminum tubular frame is much more robust with no frame flex adding to safety and stability.

Body

Fiberglass open fairing

Fiberglass or carbon composite with chromally steel embedded cage.

A fully enclosed composite body with a chromally integrated roll cage will be safe, secure and quiet.

Suspension

Frame centric monoshock

Three wheel in dependent

The independent suspension on all three wheels will provide a smooth ride with great handling.

Brakes

Cable actuated drum, hand lever and foot brake

Hydraulic disk, pedal actuated with front/rear  proportioning

Hydraulic disc brakes will be responsive and provide superior braking.  The proportioning valve will allow me to balance the front brakes to the back brake.

Motor

AC 9, 38HP, 85 ft-lbs

AC 31, 50HP, 115 ft-lbs

Likely similar power to weight ratio since the Lithium BugE was tuned down but this much larger motor will remain cooler.

Controller

Curtis 2265, 102 Volts, 300 Amps

130 Volts, 550 Amps

More powerful and higher system voltage

Cells

Prismatic Thunder Sky TS-90LFP, 24 cells X 90AH, total energy 6.9 to 7.2kwh

Cylindrical K2 Energy LFP22650P,
1980 cells X 2.6AH

Far superior cells handling 8 to 10 C continuous compared to 0.8 to 1 C for Thunder Sky cells.  Total energy will be >15kwh. There should be much more usable energy as a result of far less internal losses.

Gross Weight

Est. 400lbs

Est. 900lbs

At more than twice the weight, the Lithium Hawk will consume more energy to start off or to accelerate but the added vehicle mass will add tremendous stability and improve handling

Drive

Sprocket and chain

Goodyear Eagle advanced synchronous drive and Honda GL1800 shaft drive.

The new drive system will be quiet and efficient requiring little to no maintenance. 

Wheels

2” X 16” moped with 2.5 inch tires

Front 17” Kawasaki  600 ZX6R wheels with oversized high mileage Metzeller tires and a Honda GL1800 rear wheel with a Bridgestone Ecopia ultra low rolling resistance car tire

Larger  wheels will help keep the vehicle stable. Rear car tire will add traction and may result in overall lower rolling resistance

Front Wheel Base

34”

66”

Far greater front wheel base will add stability and improve handling

Size

Small

Height of a small SUV

Driver will have greater visibility and will be easier to be seen by others

Passengers/Seats

No passengers, one driver seat

1 passenger, 2 seat

Seats are Corbeau reclining racing seats.  They are very light, comfortable and can be adjusted

Safety Belts

None

3 point safety harness for driver and passenger

These are professional racing harnesses

The reasons I chose the GL1800 shaft drive and swing arm is that they are built using aircraft grade aluminum (outer case), seem to last >100,000 miles, can be equipped with a hydraulic adjustable shock and it so happens that one of the lowest rolling resistance car tires (Bridgestone Ecopia) fits the stock aluminum Honda rear wheel.  In addition, the shaft drive is silent.  Don Breneman, a bright guy who has built some electric vehicles himself, made me aware of the common availability of these drives as a result of trike conversions.

 

Shown is the Honda GL1800 Goldwing shaft drive and swing arm rear end.  This picture was taken before I installed the Goodyear Eagle PD synchronous drive between the motor and splined female drive shaft to obtain the desired gear ratio.  The tire is a Bridgestone Ecopia car tire, one of the lowest rolling resistance tires ever produced.  Note the cardboard mockup pulley on the shaft drive.

 

 


The Honda Gold Wing shaft drive and swing arm
with a Bridgestone Ecopia car tire
 

The seats are Corbeau racing seats.  These are light weight, fully adjustable seats.  As a safety feature, I also bought 3 point Corbeau safety harnesses with pads with an automatic tensioning device.  The sliders are dual locking seat sliders that are center bar adjustable. The front wheels are oversized high mileage Metzeller tires on 17" Kawasaki ZX6R wheels.

 

 


The front end is 66" wide
   
 

The chassis has about 11" of ground clearance bringing the seat height to that required by the motorcycle equipment regulations (700mm).  I also purchased a hydraulic adjustable rear shock absorber to be able to adjust the rear height from the dash.  I had a custom shock bracket built to increase the vehicle clearance to help meet the regulations for seat height.

 

 

 


The chassis shown with high ground clearance,
proper seat height and tandem seats
   
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