Frame layout: Tubing size

Looking at the photos from some of the other vehicles I have been referring to, I am a bit uncomfortable with the tubing sizes that some of them use. My primary reason is because of crash protection.

Jim Musser's chassis is the most attractive to me because it forms some protection around the occupant. The tubing he employed was 2.00 inch square tubing with 0.12 (1/8 inch) wall. I like that, but wondered if there was a readily available square tubing that might be an improvement.

I have settled on 2.00 x 3.00 x 0.084 (14 gage) rectangular tubing. It is about 10% lighter than the 2.00 x 0.12 square tubing, and is about the same stiffness in the 2.00 direction and almost twice the stiffness in the 3.00 direction. Orienting the 3.00 side vertical in the bottom rails and the 3.00 side horizontal in the top rail of the frame should result in a stiffer frame with a minimum weight penalty. A stiffer frame should be better for performance and definitely better for crash protection.

Design Rationale: 6 - 8 inches ground clearance

The Sport Cycle has about 4 inches of ground clearance. Last summer, I built a Marauder recumbent bicycle as designed by http://www.atomiczombie.com/ It had 4 inches of ground clearance and it dragged when I rode it over the hump where our driveway crosses an irrigation canal. I modified the frame to 7 inches of ground clearance and that seemed to be a good number.

Design Rationale: Aluminum body

I know that fiberglass seems to be the ideal material for building a custom, one-off body. The problem is that;

1) Any time I work with fluids I make a huge mess and am rarely happy with the results.
2) I have been sensitized to chemicals in the past and don't want to repeat that experience.
3) The resulting aluminum body should be lighter than a fiberglass version would be.
4) Working with aluminum sheet metal looks like a ton of fun and a natural extension of my current skill set. I also think that once I am tooled up and have some experience with aluminum sheet metal that I will be faster working with it than with fiberglass.

Design Rationale: Non-tilting design

There are a number of 3 wheel vehicles that have been or are in the process of development that utilize tilting, like you see in a motorcycle going around a corner. There are huge benefits in handling with this approach and it has been a real temptation to incorporate this feature into the design.

However, there are some very big challenges to a tilter that I won't elaborate on here. Because of the scope of the project without the added complexity of a tilting design I have elected to stay with a conventional steering system. This project is on my "Bucket List" and I need to keep it reasonable if I am going to get it done.

Design Rationale: 500cc Ninja powertrain

A variety of engines have been used for vehicles similar to what I am working on. The XR3 and the MAX both use small Kubota diesels. The Indy Cycle built by Jamieson DuRette uses a 750cc motorcycle. The Sport Cycle by Jim Musser was designed around an 1100cc Kawasaki. One of the Sport Cycle kits that Jim produces was powered by a 600cc bike. The HyperRocket is powered by a 250cc Ninja.

Fuel mileage for the XR3 and MAX is in the 50 to 80 MPG range. The Sport Cycle with the 1100cc engine gets about 45 MPG. The HyperRocket gets 100 - 125 MPG.

Initially I settled on a 250cc Ninja, largely based on the performance of the HyperRocket. However, the HyperRocket was developed in Michigan and I live in Montana. My commute includes some moderate hill climbs and I believe the frame on my vehicle will be heavier than that of the HyperRocket. In a conversation with Jim Musser, he shared that the Sport Cycle that featured a 600cc power plant still had excellent performance, I decided to look for about a 400cc bike.

Knowing that I might have to gear the bike down using a larger rear sprocket, a 6 speed transmission and the capability of high RPM would be important in order to meet quick performance and sufficient power required for good handling in traffic and hill climbs.

I found a 1989 EX500 Ninja on Craigslist for $300 - in boxes - but the price is right. The odometer shows 6800 miles, so I snapped it up.

Design Rationale: 1000+ mile range on a tank of fuel

Life for our family tends to be paycheck to paycheck - maybe you can relate. With this range, I can fill the tank on payday and it should be sufficient to make it to the next payday. 'Nuff said.

Design Rationale: Enclosed cabin

Many of the three wheeled vehicles out there or in development have open air cabins. I plan to use this vehicle as a daily commuter when we don't have snow on the ground, so an enclosed cabin is a must. This does present a more difficult project with particular challenges regarding sourcing glass. My garage is also typically used for projects, not parking, so I don't want this thing becoming a stagnant "car pool" in the winter time.

Design Rationale: Good in-traffic performance

My father-in-law has often said, "If you want to look successful, find a parade and get in front of it."

I also remember hearing a statistic in the 1980's that there were more VW vans in front of traffic jams than any other type of vehicle.

No one wants to drive a slug. It is a matter of both pride and safety to have a car that handles well in traffic, climbs hills reasonably, and corners safely.

Design Rationale: 85 MPH performance speed

I say 85 MPH performance speed because I live in an area where speed limits on the interstates is 75 MPH. I think a car needs to get to 85 MPH in a reasonably quick, responsive way in order to be safe during passing. Above 85 MPH is excessive and an endangerment on public roadways and should be reserved for the track. Sorry - I guess I'm just getting old. Will this vehicle go over 85? Shouldn't be a problem. But that is not my purpose.

Design Rationale: 75+ MPG

Originally my goal was 100+ MPG since my daily commute is about 110 miles round trip. The HyperRocket achieve that and more. However, since its seating is tandem and I plan to be side-by-side, and because I am planning to build a more substantial frame to improve crash protection, my goal has been adjusted to 75+ MPG. Currently I plan to burn gasoline. A conversion to propane is a real possibility also.

Design Rationale: 2 seat side-by-side

My initial purpose was to build a 100+ mpg car and the best way to do that is to keep it as small and light as possible. That meant one seat. However, I know that this may be the only car I ever get built (God willing) and after all that work, not being able to share the experience with someone else would be very disappointing. It would be incredibly fun to drive, though. There are several on the web. The Sport Cycle designed by Jim Musser is a great design. I especially like how he has designed the front suspension to prevent body roll while cornering. I will be using the same concept in my design. You can check out the Sport Cycle here: http://autos.groups.yahoo.com/group/IndyCycleOwners/ Another nicely done single seat was built by Jamieson DuRette and you can check out his version here: http://www.indycycle.net/IndyCycle/indycycle.html

Enter the 2 seat tandem design. I actually started laying out the chassis for this version, but a ride I took in a Varieze airplane kept coming to mind. It is a two seat tandem design. While I enjoyed the ride, it felt very "disconnected" from the other person. One interesting design along this line is the HyperRocket. You can check it out here: http://ecomodder.com/blog/hyperrocket-125-mpg-100-mph-3wheel-motorcycle/

Enter the 2 seat side-by-side version. I have two main objections to this design, namely 1) increased frontal area will result in higher drag and 2) the asymmetrical loading while only occupied by the driver affects the handling in such light vehicles. In spite of these two disadvantages, I can't imagine not being able to sit beside my beautiful, sweet wife, Julie, while driving down the road. She likes this one the best too.

So now I have adjusted my target on the fuel mileage to 75+ mpg. I commute 55 miles each way to work every day, so it would still be a great improvement.

The only problem with the 2 seat side-by-side is that I will have to remove part of a wall in order to get it out of my shop after building it. At least its not in a basement where I would have to dig a tunnel also.

Design Rationale: 3 wheels, 2 front & 1 rear

I have long felt that a three wheel design has significant advantages over a four wheel design, and that putting two wheels in front with proper attention to CG would satisfactorily address the rolling tendency associated with 3 wheelers. R.Q Riley, developer of the XR-3 and other 3 wheel vehicles, has excellent articles discussing 3 wheel vehicle designs in detail, so I won't repeat that here. His web site is http://www.rqriley.com/

Three wheels also has the advantages of lighter weight and reduced mechanical complexity. Powering the vehicle through the single rear wheel gives the option of "bolting up" (sort of) an existing motorcycle frame as the drive train. This saves a great deal of build time.

Lastly, three wheel vehicles are recognized as motorcycles in many states, and this helps with licensing and insurance requirements.

Design Parameters

Design goals for the Sport Trike 2x are:

1. 3 wheels, 2 front & 1 rear
2. 2 seat side-by-side
3. 75+ mpg
4. 85 mph performance speed
5. Good in-traffic performance
6. Enclosed cabin
7. 1000+ mile range on a tank of fuel
8. 500cc Ninja powertrain
9. Non-tilting design
10. Aluminum body
11. 6 - 8 inches ground clearance