Trike #1

The first trike was to be built for a friend's daughter.  It was decided to go with the tadpole design and we would use parts off of salvaged bikes where ever possible. In the picture above both the brake cables and handle bars were left long so they could be shortened to size after "final fit" with the rider.

Frame

     The frame was made out of mild steel 1" box tubing and welded together with TIG.  Round tubing like muffler pipe was considered but I didn't have an accurate and/or reliable method of doing a "fish mouth" or contouring the end of the round pipe so it would fit tightly together for welding.  Mild steel is cheap, easy to come by and doesn't require any post-welding heat treatment like aluminum or chrome moly steel does. 1/8" wall tube was used for the crossmember connecting the wheels as well as the two parallel pieces extending out front and creating the boom.  The remainder of the bike uses 1/16" box tube as well as a few short pieces of bike frame tubing for the handle bar mounts and adjustment.  The seat stays off of a salvaged bike were used to not only mount the dual rear brakes on but to try to take some of the torsional twist out of the rear wheel forks and transmit it forward into the frame tubes under the seat.

     I made the boom the way it is because booms can flex up and down, left and right, and twist.   I wanted to eliminate these things if possible.  I orginally made the boom so that it could be extended and bolted to accommodate different size people.   As I think breaking chain is a poor way to accomplish bike adjustment, and often the chain tensioner designs are noisy I decided to adjust the bike by moving the seat.  This design doesn't always make for the shortest bikes, but it makes adjustment for different sized people much easier.  In the end I made sure the cranks were far enough forward for your heals to clear the main crossmember, and then welded the boom in place.  There is also an angled piece of box tube that provides cantilevered bracing from the boom down to a frame member underneath the seat to reduce boom flex.

     The steering necks off two bikes were cut down to matching sizes, and as previously mentioned, a bottom bracket or crank housing was also used off an old bike.  One note on steering heads and bottom brackets though. Often these items are brazed when the biek is built and they need to be THOROUGHLY ground after being cut off the old bike otherwise you can encounter a lot of problems trying to weld them to your new trike. It can also be a pain to fill all the holes from where the original bike tubes were connected, in these reused bike parts.

     Chain guides were made out of two old rollerblade wheels and the rear wheel drop-outs were cut off an old bike frame.  Cable guides were made out of 1/2" pieces of steel tube.  The ends of the tube were beveled to 45 degrees and tack welded onto the frame.  Lastly, and you can't see it in the pictures, but the return side of the chain runs through a short section of garden hose to help keep it tight and to stop it from potentially dragging on the ground.  Additionally, 3 small 1" x 1" x 1/8" steel tabs were added to the rear forks for mounting a fender and/or bike rack, and 2 small tabs were added to each of the kingpin assemblies for later mounting of fenders.  There is also a small tab at the front above the crank housing to mount a light should it be desired.

Seat

     The seat was made by my friend out of 1" electrical tubing (or EMT).  It was bent with a simple store-bought hand pipe bender and the seat has 2 support tubes bent, and welded to the bend at the base of the seat, and the second near the top.  Small 1" square pieces of 1/8" steel are used to fasten the seat to the seat rails at the bottom and to the seat back adjustment at the top.  The seat material was sewn from a black nylon mesh and is secured at the back with laced nylon cord running through grommets.  The bike was specifically designed for a single individual so the fore-aft seat adjustment is minimal but can be moved 4" in total on predrilled pieces of 1/8" angle iron seat rails.  The picture below shows the seat adjustment, as well as a closer view of the cable stays.

     The EMT is galvanized, so it needs to be thoroughly ground and/or cleaned before being welded.  The fumes are toxic in an enclosed area and the zinc makes welding difficult.  Using bathroom cleaner that contains hydrocloric acid is an excellent way to strip the zinc off but it should be wiped with alcohol or naphtha afterwards to remove any residue.  Grinding the zinc coating off with a wire wheel is also an effective method, but it takes a bit longer to accomplish.

Wheels

     The rear wheel is standard 20" wheel with a 5 speed cassette on it.  The front wheels are heavy duty 20" wheels with 48 spokes and 14mm axles so they can withstand not only the lateral forces from turning at high speeds but also only being supported at one end of the axle.  A bigger rear wheel can be used and gives higher top speed but you also run a higher risk of collapsing the rear wheel while cornering hard.

Misc Hardware

     The derailer and gear change lever was salvaged from an old bike.   It is important to match up the lever and derailer to match the number of gears on the rear wheel.  Some older derailers and gear change levers don't have a big enough range of motion to accommodate more that 5 gears.  The dual rear brakes were salvaged off an old bike as well, but new BMX brake levers were installed because they come with a "parking brake" which is a VERY handy thing for a trike.  Because the trikes are always "ready to roll", and they roll very easily, withou a parking brake attachment on one of your brake levers, the trike will roll away on you if parked on anything but flat ground.  It is also very important to match the brake levers with the brake calipers because different levers provide different of leverage and pressure, and need to be properly matched with the pull length and pull pressure of the calipers.  Hand grips will be added once the bars are trimmed down to size.   The steering knuckles for the end of the steering rod were bought at the local hardware store.

Specs:

Next time . . .

     As this is the first trike I've ever built, there are a number of things I want to change on the next one . .

• change the seat design.  Make it wider so that the sides of the seat back don't dig into my shoulder blades.  I'll try 18" and go from there.
• increase the angle of the boom so it tilts up more from the main crossmember.  This will give more heel clearance - just in case.
• try 1/16" wall 1" box tube for the whole frame and add a cantilever support to the top of the boom to stop downward boom flex during pedalling.
• Try to make the track narrower, the main frame rails narrower and try to cut the weight down a little.  I also want to optimize the frame length to accommodate heights of about 5' 2" up to 6' 2".
• add a 2 or 3 sprocket chainwheel with a derailer for extra gears and higher top speed
• maybe try front wheel brakes instead of rear wheel.  Might also try brakes on all wheels with some kind of brake pull divider to brake both front wheels from the same lever.
• add a small bracket for a visibility/safety flag and add a small piece of tube for a bike lock mount

More bike details when more bikes are built :)