Cutting the Main Frame Tubes

I am planning to use a non standard front suspension system that will give the vehicle a very smooth ride, and want the entire weight of the battery bank to be taken up by the differential, so that the frame does not have to take any extra loading. By integrating all of the heavy mechanics into the differential, I am basically building a two wheeled electric car that will just happen to have a lightweight, 16 foot long motorhome sitting in top of it. The only mechanical part at the rear of Arcturus will be a motorcycle wheel on a simple swingarm suspension system, allowing the body to take on a very efficient aerodynamic "fish" shape in order to keep wind resistance to a minimum.

The main part of the frame will consist of a 10 foot long camper area and a raised 4 foot long cockpit section to place the riders over the front differential. The width of the vehicle will be 4 feet, but slightly tapered to the rear where the width will fall off into a more aerodynamic fish shape. All tubing is 2 inch square steel with a wall thickness of 1/8, providing a sturdy foundation to mount everything else. The goal will to place the camper area as low as possible, yet still allowing adequate ground clearance and to also place the riders up high enough to see other city traffic eye to eye. This plan works out nicely, and provides room under the front of the frame to install the motor, battery bank and the suspension system, all which will be supported by the differential.

Cutting the tubes for the main frame.

Cockpit Frame Rails

These two frame rails (shown upside down) will provide the foundation for the frame of the cockpit. The seats will be placed just ahead of the corner, and the adjustable bottom brackets will install near the front of the frame. Having adjustable bottom brackets will allow the cranks to be positioned perfectly for riders of any height. Moving the pedals is better than moving the seat, since you want to be sitting side by side with your camping partner. The length of the cockpit frame tubing is 4 feet, and the length of the riser tubes is 16 inches. The angle of the riser tubes was chosen completely by random.

The two frame rails for the cockpit.

These two frame rails (shown upside down) will provide the foundation for the frame of the cockpit. The seats will be placed just ahead of the corner, and the adjustable bottom brackets will install near the front of the frame. Having adjustable bottom brackets will allow the cranks to be positioned perfectly for riders of any height. Moving the pedals is better than moving the seat, since you want to be sitting side by side with your camping partner. The length of the cockpit frame tubing is 4 feet, and the length of the riser tubes is 16 inches. The angle of the riser tubes was chosen completely by random.

Fresh arc welds need chipping.

I enjoy being a minimalist, so in my garage, I have only a basic AC welder, and angle grinder and a hand held drill. Besides the usual wrenches and screwdrivers, I own no other tools. Every bike or electric vehicle I have ever made was done using only these basic tools, and Arcturus will be no exception. An AC buzz box is the most basic welded you can own, but like all skills, practice is the key to perfection, not how fancy your tools are. These welds look pretty scary, but that’s only the flux coating from the rod, and will be chipped away to reveal the weld metal.

Welding order is important.

The chipped welds look a lot better once they have had a little cleaning with a wire brush. When welding square tubing together, the order of welding become extremely important since cooling weld metal tends to shrink with an incredible amount of force. By welding the top and bottom of the joint first, any side to side warping of the frame tubing can be avoided. Sure, there will be a slight distortion in the angle of the cockpit frame tube and the riser tube, but since the angle s not critical, all that matters is that both rails are the same after welding. To ensure this, welds are done in the same order for both rails.

Finishing the sides of the joint.

With the top and bottom of the joint welded first, side to side distortion can be avoided since the other welds will keep the tubing aligned. Good penetration is also important in a joint that will see a lot of stress, so the current is turned up high to weld this heavy wall tubing. Compared to bicycle tubing, this heavy tube is a breeze to weld.

Comparing the frame side rails.

The two main frame rails are placed side by side for comparison. Since all welding was done equally on both sides, the two frame rails are identical. Having a flat cement floor to weld on also makes a huge difference, since these parts are much to long to place on the workbench.

Added the front frame tube.

The front and rear end tubes are installed to join the two frame rails together. These tubes are 27 inches long, which is the perfect width to allow two people to sit side by side comfortable and allow the front wheels to turn to their full range of motion. Cross bracing and trussing will later be added to carry the 4 foot wide frame and support the floor, but it will be made of lighter tubing.

This is where the differential will live.

The front differential and most of the heavy stuff will live just under the area where the two seats will be, over the front frame tubing. This higher tubing gives the differential some room to move once the suspension will be installed, and also places the riders at eye level to larger vehicles. Since all of the heavy parts including the drive motor, battery bank, and human cargo will be right over the differential, the rest of the vehicle can be made using lightweight construction.

The seats will be right over the differential.

This is where we will sit – just ahead of the corner formed between the riser tube and the main cockpit frame rails. There is plenty of leg room to allow the bottom bracket to slide up for very tall riders, and plenty of room for a floor if I decide to add one. The steering system will be placed under the pilot’s seat on the right frame rail, so it will be easy to link to the steering hardware on the front differential. Brakes will be provided using a manual pump master cylinder connected to the brake hardware on the differential. No power brakes or steering will be used, keeping thins simple and easy to maintain.

The main frame is now 14 feet long.

The main frame is now 14 feet long, but the overall length will most likely grow to at least 18 feet once the rear wheel swingarm and body have been added. This is still a manageable length when you compare it to some of the trucks on the road, and certainly more manageable than a pickup truck pulling a 30 foot long trailer! Arcturus will have onboard all of the amenities and offer the same comfort level as any trailer of equal length, but it will travel from point A to B under human and solar power alone.

Next: adding the front suspension system. More to come soon!

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