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Today I started working on the top view of the Tigon. Still much work to be done on it but you can get an idea of the general aerodynamic shape I am going for here. The body design if you are wondering is a heavily modified Fiat Turbina. There are some improvements I have made to the body design as you will start to see as the sketches become more refined.
So where did I get this idea anyways?
I purchased the Urba Centurion plans many years ago which gave me the original idea of creating my own body shell and utilizing a donor chassis. The plans also pointed me into the diesel direction as the energy source. Although the Urba Centurion is a solid design that achieves over 100mpg, I thought it could be made much better performance wise and improved upon aerodynamically.
The original only had a 17hp 3 cylinder diesel in it for propulsion which gave it a horsepower to weight ratio of 1200lbs/17hp = 70.5 ratio. I think this was fine for the time but for today's standards I think you could use a lot more on the low and top end. For a quick comparison the Geo Metro XFi had a Horsepower to weight ratio of 1,621lbs/49hp = 33 with 58 torque @ 3,300rpm. So its safe to say the Urba Centurion could use a little help in the acceleration department. The Urba Centurion topped out at 65mph which to me is to slow for our modern freeways. The plans do not state the 0-60 time but I estimate it to be very slow to say the least! The Geo Metro again for comparison sake can theoretically hit 100mph and many individuals have stated getting it up to 88 to 90mph.
The Urba Centurion was not meant to be a speed demon by any means and I am not trying to build the Tigon as such either, however I feel as though the Tigon needs to have better acceleration than the Urba Centurion and better acceleration than the Geo Metro. In order to achieve this I new I would have to do a major update to the general plans of the Urba Centurion. So that is exactly what I am doing. When I decided to move forward with the plan I came across another plan set of a person who turned an Opel GT into a diesel hybrid. This sparked my interest into hybrids and I have been researching them ever since.
For many years I was dead set on an all electric Tigon, but my practical wife stepped in and thought for the first prototype it would be good to go the hybrid route. This way it has the opportunity to appeal to more people and I tend to agree. I have always loved the idea of driving on electric helping to decrease my carbon footprint but also driving on biodiesel or recycled petroleum products. So why not build the Tigon to do both? I could not come up with enough reasons not to so the Tigon Hybrid was born and will in fact be the first prototype.
After reading and studying the Urba Centurion and other plans I felt as though it was time to create an updated modern plans booklet. You can absolutely learn a lot from the Urba Centurion and other plan sets, but I felt the plans had potential for expansion into theory and component selection. These are 2 areas of the Tigon plans I will definitely expand on.
In order to achieve my performance goals and range I new that I would have to go diesel with electric. I almost went all diesel with a VW 1.4L 3 cylinder TDI but I liked the idea of using electric in town to much and felt the combination of the two would be overkill. Then I stumbled onto the Smart for two CDI .8L turbo diesel. Now I thought this would just about be perfect but quickly realized that if I was going to be making a plan set for this vehicle it would need to be practical for people here in the US to get the parts for it. So both of those engines would not work as they are both illegal in the US currently.
So I settled on a 2 cylinder .79L 19hp V twin diesel that is both cost effective and legal here in the states. It holds an EPA Tier 4 rating and I have no problem importing the engine through customs. The company I am getting the engine from also has a 10kw genset based on this engine that is EPA certified as well so perfect for the series hybrid design option. This diesel is more efficient than the original Urba Centurion Diesel and more powerful. This component selection really sets the stage for the rest of the vehicle. The weight of the engine is only 126lbs compared to 181lbs of the Urba Centurion. So not only is it more powerful and efficient it also weighs 55lbs less.
The electric component of the hybrid drivetrain will use a brushless design. Not completely set on whether to go PMAC or BLDC. I thought I had it all figured out until the company I was going to get the PMAC motors from has backed out for whatever reasons. So I may have to go the BLDC route which I have all ready contacted numerous suppliers and have some solid options lined up at affordable pricing.
The Urba Centurion had a curb weight of 1,200lbs. I felt I could easily knock off 200lbs or more to the design with modern materials, 3 wheeled platform, and better component selection. So far I am sitting at 611lbs diesel only and 706lbs with hybrid components. So it looks promising at this point I can definitely knock off 200lbs to the Urba Centurion design. The vast majority of the components have gone into the weight calculation thus far. There really is only small minor parts that have not been accounted for. So I feel pretty good so far with my design weight.
The lower weight gives me some options I would not have if the vehicle was 1,200lbs. First I can go with a smaller electric motor and battery bank. This opens the door for a 20kw peak motor to be used for traction purposes. You would find this size on motorcycles and smaller electric vehicle builds. Do to the low weight and enhanced aerodynamics of the Tigon this small of a traction motor is very possible. This further cuts weight and costs. The voltage range I will be utilizing will most likely be 120V. A brushless water cooled 20kw DC motor I have been looking at weighs 35lbs and has more torque than the Geo metro engine by a longshot. The motor will put out over 55hp peak. So very light, compact and powerful electric motor. looking at the numbers if we can in fact get down to 1,000lbs curb weight and we can safely put out 55hp peak we have a hp to weight ratio of 18. This is far better than the Geo metro or Urba Centurion not to mention we have instant torque available at 0 rpm perfect for in town use or getting onto the freeways.
The body design was taken from the Fiat Turbina one of the most aerodynamic cars of all time. It just so happened that the Turbina had very similar size specs as the GT6 I used for the donor chassis. So I have been studying the Turbina as well as general vehicle aerodynamics and incorporating what I learn into the Tigon body design. At this point I think I have a pretty solid body design being sketched up definitely needs to be refined but has a good profile and modern look going. The Tigon definitely does not have your normal 3 wheeled trike feel to it. In fact it looks more car like than trike and this was part of my goal. I wanted to have a 3 wheeled trike that has an all year round cabin rather than open cockpit like most of the 3 wheeled designs you see. This creates more versatility I believe and is more practical for the majority of people to use as a commuter vehicle including myself.
Tigon will definitely not be the answer to all of our fuel problems, but it will provide a good option to help reduce them responsibly. I hope as this build thread continues you all will find it interesting and helpful.
GreenHornet
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