Introduction: Three Wheel Bike Car
Second Prize in the
Spring Bike Contest
No gas pump for this car! A Three Wheel Bike Car, with panniers, a cargo platform, 16 speeds, and a canopy. This project allows for worthwhile grocery trips, pleasurable joy rides, drive-through coffee or bank drive-ups, and the ability to carry what you need, whether that be croquet mallets, warm clothing, a load of groceries, you name it.
Step 1: Get Inspired.
This was an idea bubbling at the back of this bike mechanic's head for several years.To be honest, a recumbent or sit-down design never had appeal for me unless the extra bulk of such a machine could earn its keep by carrying loads. The three wheel design differs from a "long bike" with two wheels, by proving to be awesome on snowy or muddy pavement; there's no fear of laying the bike down in inclement weather. Sketching, collecting cast-off parts, measuring bike path widths, assessing what needed carrying, these went into formulating a somewhat unique design. 30 years of professional wrenching experience made technical issues like drivetrain design and general bike part selection and set up easy. Welding was required; my skills are rudimentary as to prettiness of the welds. This partly owing to using a basic flux-cored electric welder. But destructive testing showed that the joints have integrity. Mechanical ethics of good joint preparation and careful fabrication essential. Accuracy in measuring and cutting, and so on. The final step of painting the frame is waiting until I'm sure I don't have any more last minute add-ons to weld. I've been riding the machine since January.
Step 2: Assess Your Needs
This instructable can't hope to completely walk you part by part through an involved project like this. If you've been around bikes in a more than casual way and have some fabrication chops, you stand to be ready to make something like this using your skills. Being the creative person that you are, you will also be poised to tweak and alter things to suit your needs. This series of sketches and photos of the bike car I built can serve as a good jumping off point for the bike car of your dreams. Myself, I don't like to build from point by point blueprints when I'm creating an original design. It's a process of designing and executing as you go. Feel free to borrow ideas from here.
Take stock of your physical dimensions in order to build a suitable frame. If you are over 180 lbs, you will likely need to incorporate beefier tubing than the 1" tubing I used, both round and square mild steel. Or you could add gussets, truss pieces, or use other ways to stiffen the longitudinal aspects of this rather long-wheelbase trike. Some flex feels good over bumps, that's a bonus of a long wheelbase. But undue deflection could lead to eventual failure for heavier riders. Think "custom" frame, and adjust to suit your build. As for length of the cockpit, it's good to have some room for adjustment. At a minimum, your feet need to clear the front cargo deck. If you are of moderate leg length leave extra room for that taller friend who will want to try your machine. You can have some flexibility by making the crank mast and the seat points moveable on their mounts in one way or another. Accomodating a rider with longer or shorter legs than yourself will entail changing the chain length with my current design. Incorporating additional chain tensioners can free you from that, but adds to cost of parts and adds a little bit of friction, noise, and weight to the drivetrain.
A basic starting point is to measure your sitting leg length: Sit with back against a wall with legs straight out, and measure the distance from the wall to your heels. This will define the general seat back-to-pedal parameter. Other things like height of canopy, width of steering bar, etc, you can work into the design to suit your build as you go. With this triangular frame design that narrows from front to back, be sure your heels will clear the side tubes as you pedal.
Step 3: Gather Parts Before Making a Hasty Start
It is great to use parts you already have on hand. This will influence your design. Which direction you go with a particular design decision is very dependant on the unique measurements of the parts you will actually use. So spend time accumulating ideal parts before cutting too much in the way of tubing or more involved parts like fabricating steering knuckles or rear dropouts. For example, the spacing on various rear hubs varies. You need to build the rear triangle to suit the actual wheel you will be using. A hefty frame like this can be very hard to cold-set to correct an error in rear triangle spacing.
I built all three wheels before almost anything. Having them is critical to laying out the frame. Brakes and other small parts were on hand early too, to help with the design process, and to be sure what I wanted was available.
Step 4: Take the Plunge
Ideally, draw with a magic marker on plywood or even the slab of your garage, use a framing square to make a baseline and a centerline for reference. This will keep your frame from being cockeyed. Work over this centerline during the frame build phase until the basic triangle is tacked together. To start, once you have general dimensions, lay out uncut tubing on the floor of your workspace, study the tube intersections and devise the best method for cutting and fitting them together. This could be hacksawing and filing mitered tube ends, or jigging up a properly sized metal holesaw in a drill press for clean "fishmouthed" miters. (I use a "Joint Jigger" fixture made for this purpose.) Make good tight fits before entertaining weld-up. Think about any mods you want to make, any places where room will be tight, and get clear about any concerns with your build up. Are you a size 14 shoe? Adjust frame to suit.
Some things to watch for: Make front cross bar that connects to the steering knuckles wider than the cargo deck, keep in mind that you don't want the turning front wheels to hit any part of the frame in use. However you will be limiting the throw with the steering components, and have some adjustability here. I used 26" wheels. If you use a smaller size wheel, you can widen the frame triangle with more room before hitting the tire. But I prefer the better gear development and the suspension feature of a larger wheel. Too small of a rear wheel can cause problems with finding short enough spokes to suit a large-flanged internal gear hub. I have the tools to thread and cut custom spokes, but its a hassle. I just don't prefer the smaller wheels in this case anyway. I wanted some ground clearance, ease of climbing aboard, and there are a great many tire choices with mountain bike tires as well. You have choices, think about them and adjust accordingly.
Step 5: Fuss With Drivetrain
I built a crank mast that allows for sliding the assembly fore and aft for leg length issues. I prefer to keep the seat near the rear tire, for good braking and traction reasons. The bike car is great on those points, by the way. The tube section added on top makes place for a derailleur as well as a bottle cage.
Although large-loop chain tensioners exist that release and take up a great deal of slack, I'm using a simple short tensioner back near the jackshaft. This takes up slack when I go from large to small front chainring. I welded up a mount point onto the large jackshaft bearing mount. Seems to work well, although it won't take up enough slack to allow me to alter the crank mast position without also changing the physical length of the chain. I don't mind doing that, and I rarely need to alter the cockpit for anyone else. It seems quieter and less draggy than the larger units. and I'm running less chain with saves weight. (But with this bike car, unlike my racing bikes, it has not been an obsessive goal to be nuts about weight.)
I'm using a fixed cog on the 5/8" keyed jackshaft to drive the chain from the rear 8 speed internal hub. Then a freewheel cog from the jackshaft to the chainwheels. I can play with the sizes of these to fine tune the gear output.
Step 6: Some Brake Opinions
For brakes, at least in the context of a bike car, I highly recommend going with disc brakes, even though they can be fussy to align against occasional rubbing. The reason I chose them, besides their stopping power, is that I think a caliper brake is too limiting: for one thing, they limit use of really fat tires. They are flexy. Even with the better cantilevers, you are still subject to building a set of stays or fork-like frame supports to be able to reach the rim. With rim brakes, you are more affected when a wheel goes out of true, unlike with the disc brake set up. And with the wheelchair hubs, a great feature is to have nothing in the way of wheel repair maneuvers, especially flat repairs. The whole tire is removable without removing the wheel. Not so if you are building around cantilevers or caliper brakes. This is all especially true of the front steering wheels on this bike car. In the back, I do have a bolt on wheel that must be removed for flat fixing, but for me that's not a big deal, and is hard to avoid with a rear triangle. The 8 speed Sturmey Archer hub can be ordered as a disc brake model. Not worrying during a ride about rear wheel truing is a plus. I'm not advocating letting your wheels get out of true. But at least in the middle of a ride you're not subjected to a "show-stopper."
Step 7: Steering Issues
The steering design is "underseat steering," a term you'll hear a lot in reference to trikes. I like a cleaner cockpit without a bulky steering setup over my lap. (this latter often is called "OSS" for short, meaning "overseat steering.")
Something different that I did: I engineered a system of cables to pull on the steering arms, with a T bar up front as a pulling point. Being a section of headset bearing, it is smooth and has decent leverage. It keeps steering hardware clear of the cargo deck. My main concern was to be able to tidy up the hardware that runs from the front to the underseat steering bar. Many setups use a one-sided bell crank that runs off to one side, this can be a space problem depending on cockpit design. For me it would have crowded the pedaling leg space. My arrangement hides the pulling device (the cables) underneath the center fore and aft tube. Clean, quiet, light, effective. I needed to make custom brass pulley towers to reverse the cable action, as well as give them a narrow line up. Works pretty well.
In much shorter trikes, often the steering is direct, with the rider pulling on handles rising out of the steering knuckles. This wouldn't work on a long-wheelbase trike, too far to reach. Those steering handles can crowd the cockpit sometimes, anyway.
I used established principles for laying out the angle of the steering arms on the knuckles. (See sketch about Center Point steering.) You can research Ackermann steering for more about all this. Basically it's best practice to have the steering arms pulling on the steering knuckles in a controlled way that helps keep the inner wheel in a turn from fighting the outer wheel so much. There still is some disparity owing to the tighter circle the inbound wheel cuts compared to the greater distance the outer wheel has to cover in executing the same turn event. But the way that the steering arm points to the rear of the "car" is germane.
Other parameters, like caster and camber, deserve some study on your part, if only to enrich your knowledge base. For a slow-speed vehicle, there are differing opinions. Some say too much emphasis is given to the need for these angular dimensions to wheel mountings when you're not talking about a motorized vehicle. Camber, especially if set to splay the bottom of the wheels out, can enhance stability in cornering. But it enforces a weird tire wear pattern, not landing on the centermost and thickest part of a cycle tire. It loads the spokes laterally. If a frame design is pretty narrow (and therefore more tippy left to right) a bit of camber can make some sense. Short, narrow sport trikes more often have camber.
Caster is a fore and aft angle, affecting the "trail" of a wheel from its pivot point as it steers. In a two wheel bike, the head tube angle and the bend or rake in a fork combine to make "trail" that produces stable steering results if done right. It's very noticable if done wrong. A bike steers poorly "no hands" if this dimension is off. (note that steering also suffers during "no hands" if steering bearings are too tight.) Some say caster is less important on a 3 wheeler, but sloppy steering connections or poor weight distribution can introduce chatter if trail is non-existent or backwards. (Think shopping cart wheel, rabbiting wildly at high speed, or when you push the cart backwards. On a shopping cart there is a large amount of caster, plus sloppy axles.)
Anyway, after much study, I incorporated very mild caster, and used NO camber. For my wide front end, long wheelbase, and loaded cargo platform, much that I read said that this could be the way to go. Some folks are hung up on this as they see visible camber on most all sport trikes they encounter, and assume it is de rigeur. But I try to keep my designs in context and don't just blindly follow similar bikes if they aren't truly parallel to what I'm building. In practice handling is very good.
Step 8: Get Out and Ride!
This was a great project. I hope you get some ideas and enjoy crafting one of your own. Since I first rolled out on it, I continue to be amazed at the fun factor--still not waning--as well as the practical usefulness. No longer am I stuck grabbing 2 or 3 items and then needing to take the car to finish regular grocery shopping. Able to haul items for friends, including those croquet mallets and a picnic for afternoons in the park. With lights, reflectors, and a flag, evening rides in the dark are fun and cars make room in a way they don't for my two wheelers. The canopy cuts the sun, and reduces the frontal wind chill nicely. It's a hoot!
Here I'll toss in a bit of advice for would-be welders: If you decide to tackle this kind of project as a lark, in most respects the worst thing that could happen would be something that didn't go down the road well---except please don't take on welding "as a lark." It can be easier than you thought, at the same time more frustrating than you thought. My main point here is to remind you to "be a pro" as far as safety. Put a sign on every door entering your workspace: "WELDING, knock first." Don't weld in the open in your neighborhood with kids or passersby being exposed to the blinding arc. Ventilate; save your lungs and other organs from the fumes. Wear a good helmet--an automatic darkening one is convenient as all get-out and helps technique as well; you can improve initial landing on the work with these helmets. Learn how to run your particular machine. Some are "hot" as soon as you plug them in, or as soon as you turn them on--this contrasts with others that will not let arc current flow until you actually press the trigger on the MIG gun. Every time you pick up the gun have helmet on and a clear path to the work. It is good practice to have a safe place to hang the gun for when you stop-- assume it's "hot" and don't lay it on the floor or just anywhere between beads, that way you'll never generate an accidental arc. Learn to turn off the switch between beads as a matter of course. (you'd be surprised how easy it is to switch the amperage setting, when you meant instead to switch the box off.) This way if you borrow or use someone else's machine you won't get a nasty surprise from an "always hot" version. Get some good books and search the 'net for welding videos. Others are more expert than me. I just want to pass on some good general shop ethics.
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