Build a Long-wheelbase Low Racer Recumbent Bicycle

This instructable details how to construct a fast, inexpensive recumbent bike from one 1980's-era road bike plus some bits off a scrap bike. You should be able to build this for around $100 less paint. I plan to document how to build the kid's version shown in the video in the future.

***UPDATE July 23, 2008 - The kid's version is now available!

I tend to get numbness in my upper back and arms when riding a standard bike. I've found that I can ride all day on a recumbent without pain or numbness. Unfortunately, I don't have large amounts of cash to buy one, so after scrounging the net looking at other home-built bikes, I designed my own. I'm quite happy with the results and have built several other bikes as well. Now if I can just get off long enough to paint it ...

A few things to note before we get started:

I made this design with the intention of only needing one donor bike. While it is possible, I found that it is easier with one 1980's era 10-12 speed and any old piece of junk to donate its front steering components and fork. I bought my donor bike at the local Goodwill thrift store for $6 and found the crap bike rotting away in the Cuyahoga River in a national recreation area.
I assume that you will clean up bike parts as you take them off the donor bike (bearings, chrome, etc.). Do it now, you'll be too busy cruising around to do it later.
I assume that you will grind and file down all your welds as soon as you make them so they look pretty. Do it right after you finish the weld, you won't do it after everything is complete (you may not be able to get at them at that point, either).
I assume that you know how to assemble/disassemble a bike and know the names for the different tubes and hardware on a bike frame. Hopefully I have remembered them all correctly. Wikipedia has a quick reference.
This project will probably take a week of on and off work. After you are done welding for the day, hit the bare metal with some spray can primer. This will keep things from getting rusty, especially if something comes up and you have to set it aside for a while.
Wire wheel any zinc off electrical conduit before welding. Don't get metal sickness.
I was too busy building to take photos during construction (and didn't want to junk up my nice camera with workshop filth). I believe the photos will be clear enough to get you going.
I can't give you exact dimensions for cutting. Bikes and bodies vary, so I tried to give you instructions on how to measure for your situation.
This is my first instructable, so be nice :) ... I used to do a lot of technical documentation, so I hope things are clear and understandable - kind suggestions and corrections will be appreciated. Good luck and please post pics!

Step 1: Collect Your Parts and Tools

The biggest expense here is going to be a welder. I bought mine from Home Depot on sale and with a coupon for around $480. For me, this was a really big tool purchase and I saved for two years for it (we're really frugal at our house). With all the materials and tools purchased, I cant imagine being out more than $800 for everything you need. Try buying a recumbent for that price. Make your own and you'll have the tools left over for more projects (I've built several bikes and have bits and pieces for a few more). Make and sell one or two more and it could pay for itself and the tools.

I spent right around $100 for materials. If you're good at scrounging and have access to the tools, you could reasonably build this for nothing. You also don't need an amazing workshop. See my craptacular shop below.

Raw materials:

10 speed bike ($6 at thrift store)
another donor frame with steering components would be great (found mine in the river)
cables ($15ish from Loose Screws - see what's on sale)
skate wheels (garage sale/thrift store $2)
3 - 10-speed chains. New is best, they should total around $30. The brand I picked up was Z-chain at $10 a length (thanks Ernie's)
1" electrical conduit ($6-$7 for 10' at Lowe's or Home Depot)
1/4" threaded rod ($4ish scrounged mine)
plywood (3/4" or 1/2") and padding (scrounged off a $2 car seat pad) for the seat
1 1/2" square tubing ($20) - you could likely substitute 2" - 2 1/2" exhaust pipe if it is more readily available. You will need around 6'. If you buy from a metal supplier, check for cutting costs. I could have had 12' uncut for the price of 6' cut.
1/8" x 2" x 8" and 3/32" x 1" x 3' mild steel - This is pretty flexible. Use what you can find that seems strong enough for the task ($5 or scrounge)
1/4" and 5/16" bolts w/nuts, washers, & lock washers
1/4" tie rod ends (2) ($7 at Wicks Aircraft Supply - you might also try Summit Racing)

Tools (probably incomplete):

flux core welder, welding gloves, tip dip, wire brush, chipping hammer
various clamps
angle grinder with cutoff/grit/wire wheels
bench grinder with cutoff/grit/wire wheels
hack saw
misc bike assembly tools
misc woodworking tools
files/rasps
an old screwdriver or similar piece of metal to fabricate a chisel for the skate wheels

Step 2: Slice Off the Rear Triangle

The idea here is to remove most of the rear triangle of the donor bike while leaving the bottom bracket shell attached to the front down tube. Before you cut, measure the distance of the bottom bracket to the ground when the bike is upright and the tires are inflated and save this measurement. You will need it when you weld the new frame together. It is important for getting the front wheel at the proper angle.

Use your hacksaw to remove the seat stays from the seat tube while keeping as much seat stay material as you can. Cut the chain stays as close as you can to the bottom bracket shell. Cut the seat tube from the bottom bracket shell leaving enough attached to the bottom bracket shell for the front derailler to mount plus about 2". Grind the remaining seat stay material from the bottom bracket shell - make it look nice.

Don't worry if you end up with big holes in the bottom bracket shell from the chain stays. Just try to keep all the metal straight so you will be able to re-thread the bottom bracket back in later.

Step 3: Bend the Seat Stays

Make sure that the rear wheel is on and pushed in as far as it will go in the dropouts. You will use the wheel to tell you how far to bend the seat stays.

Bend the seat stays down with the rear wheel and brakes still on. Don't bend it so far that the brake bracket will rub on the wheel or that the brake pads can't be adjusted to hit the rim. It would be nice to cut some sort of form for this step so that everything is bent evenly. I didn't do that. Instead, I used small pieces of 2x4 lumber to set where I wanted the bend and tweaked it by hand - kind of an ad-hoc form I guess. It worked well enough, but if you look real close, the seat stays don't have exactly the same arc. Next time I'd make a form out of plywood to bend them over.

I tried to have the top of the seat stays be parallel to the ground when the recently cut chain stays are around 6" off the ground.

Step 4: Make Main Tube Bracket and Weld

Cut a 1/8" thick piece of mild steel to weld to the chain stays in place of the bottom bracket. It should be wide enough to reach the outer edge of the cut chain stays and at least as tall as the square main tube (1 1/2"). The metal I had was a little taller than the square tubing and I didn't bother to cut it down. Weld it up centered on the end of the 1 1/2" square main tube at a 90 degree angle.

Clamp this assembly upright about 6" parallel from the floor. Weld to the chain stays with the wheel installed and touching the ground. Try not to get sparks from the welder on the tire (or use and old tire you don't care about). Some damp drop cloth material would work.

The 6" measurement is pretty flexible, so do what seems to look right to you. Make sure that you grind the cut ends of the chain stays so they are flat on the bracket you fabricated and that this is a good strong weld. Also sight down the frame and main tube assembly to make sure the frame is straight. It is long enough that you should be able to eyeball it. If not, center up your 1" conduit along the main tube assembly and through the rear triangle (after measuring and clamping up the proper height and removing the rear wheel) and measure the rear dropouts to be equidistant from the conduit ... or just eyeball it.

Step 5: Weld Seat Stays to Seat Tube

Now we need to attach a new seat tube. The seat tube will support the seat back, so it needs to be angled correctly. My research and experience shows 30 degrees to be pretty comfortable.

Your offcut piece of seat tube will probably be too short, so we will use 1" conduit. Measure up a piece that will allow for an angled cut at the bottom where the seat tube attaches to the main tube.
weld the new seat tube to the seat stays (that have been bent) and to the main tube at a 30 degree angle. Grind the tube to fit and weld. Try to keep everything centered up and straight.

The rear part of the frame is complete. Yipee!

Step 6: Measure the Main Tube and Cut

Sit your hind-end on this thing backed up against the seat tube (after it cools) and stretch out your legs. Clamp a 2x4 (or two) to the seat tube to simulate your seat and padding depth. Stretch your legs out flat-footed and have someone mark the main tube at that point with a sharpie.

Now either measure the distance from where your foot hits the pedal to the back of the bottom bracket (see photo), measure back and then trace the bottom bracket shell on the main tube or fuss the pedal to the line you just marked and then trace the bottom bracket shell this way.

The idea is to locate the bottom bracket in relation to where the pedal needs to be in order to fit your body. I didn't design this with an adjustable seat, so it needs to be right. Once you are sure that you have this measured correctly, cut the main tube and grind/cut it to fit around the bottom bracket shell. This is a pretty critical cut, so take your time, measure it up right and grind it to fit snugly and straight.

Step 7: Weld Up the Bottom Bracket and Front End

This is one of two tricky welds. A jig would help tremendously here, but for a one-off bike, I personally wouldn't make one (I want to make bikes, not jigs). With careful clamping, you should be able to clamp a straight piece of metal (like the leftover 1 1/2" square tube or the 1" conduit) or a straight 2x4 across the down tube, the top tube and the new main tube to keep things straight while welding.

The proper angle is determined by the bottom bracket measurement you made at the beginning before you cut the bike apart. make sure the wheels are on the frame and inflated, make a straight line between them and adjust the angle so the bottom bracket will be the proper height from the ground. If you have feet larger than size 10, you might want to add 1-2" or your heels may scuff the ground when you pedal. You could measure your shoes and make sure you have a good 1" clearance. This is very dependent on the donor bike and can be adjusted later (but do it now - it's easier and less work).

Now, weld it up. Spot weld on one side and sight down the frame and make positive that everything is straight and that there are no twists. I was able to keep things straight easily, but I think I just got lucky. If it's off, you should be able to bend it and tweak it a little. If not, grind the weld away, re-adjust, and try again. With a long bike like this, it's pretty easy to eyeball when things are off. Once everything looks good, carefully finish your welds. Don't weld it too hot (and the bottom bracket should be removed from the shell already). Be careful not to get slag in the shell threads.

Step 8: Strengthen the Steering Tube

Cut and grind the top tube from the donor bike. Cut a piece of 1" electrical conduit to fit from where the top tube was, across the old seat tube (now the front derailler tube), and then to the main tube. Grind a birdsmouth so it will fit the steering tube and the proper angle to fit the main tube. Grind a birdsmouth in the front derailler tube and weld in place - make sure it is straight and centered or it will look goofy and cause you to crash when you're staring at your goofy-ass support tube while careening down a hill. Really watch the heat with your welder - this metal is thin.

Congratulations! You have the basic frame completed. We now need to build the remote steering, the seat, and assemble!

Step 9: Remote Steering Front Fork

Fabricate a tab to weld to the front fork. It should be the width of the fork and around 2 1/2 "- 3" long. You can get an idea of scale from the photo. The metal should be 1/8" thick.

Grind it to fit whatever fork you are using and round off and smooth the other end. Drill a 1/4" hole and mount one of your tie rod ends.

Step 10: Remote Steering Handlebars

Here is where, with a little ingenuity, you could eliminate the need for a second donor bike. If you feel like fabricating a simple steering assembly, go for it and please post photos. I had a steering tube already cut out and ground from another project and decided to use it to save time. I will assume that you are using a donor steering tube.

This is one of those parts that will need to be adjusted to your body and preferences. I sat on the bike with the assembled steering tube with handlebars attached and held my arms in a comfy position. You will likely need someone to help you with this.

Once you figure out where you want the steering tube, measure and cut a length of 1" conduit, grind to fit the steering tube and main tube, and weld to the main tube. I have had this tube face both forward and back. I prefer forward, but whatever seems to work best should be fine. Weld the steering tube at approximately the same angle as the front steering tube. Get it as close as you can; it will help with the feel when you are turning to have everything at the same angle.

Cut the forks from your second donor bike and weld on a tab the same size as the front tab. It's easier to match everything up if the the forks are built similarly. The distance from the center point of the steering pivot to the pivot of the tie rod should be equal. Mount the other tie rod end here.

Re-install the bottom bracket, cranks, and pedals (if they aren't already there). Install your remote handle bars and fiddle with them so you don't hit your knees when you pedal. This will take some trial and error.

Step 11: Remote Steering Tie Rod

Connect the two tie rods with 1/4" threaded rod. I used rod from a bed box spring and cut threads on each end. The rod will not be strong enough in compression and will bend (especially with spring steel from a bed - boingy!) I ended up cutting and gluing some wood around it for support.

With a little adjustment, you should be able to steer now!

Step 12: Seat and Brackets

The seat and seat back are made from 3/4" cabinet grade plywood that I had leftover from some other projects. 1/2" would probably work fine. The seat bottom is 12" long and tapers from 12" in the front to 10" in the back. The seat back is 18" tall and tapers from 10" to 8". Adjust these sizes to fit your body. Round off the edges. I used cd-roms to trace a circle and borrowed a jigsaw, but a coping saw would work. Use your wood rasp to remove any sharp edges and smooth out your cuts.

There are several tutorials on the net on how to build a lightweight frame and wrap it with mesh material, but I was sick of welding at this point and wanted to ride. The wood seat was quick to build and ended up being good enough, so I covered it and left it. I plan to steam-bend some cherry for a seat at some point to match the fenders and other bits of the bike. I recommend you do something quick that works and upgrade later.

Now we need to attach the seat. Cut five pieces of your 1/8" steel to these approximate sizes:
1 - 1" x 2"
2 - 1" x 8"-10"
2 - 1" x 3"

These dimensions will vary depending on the tubing sizes you end up with. the two 1" x 10" pieces will need to be bent at a 30 degree angle to hold the seat bottom and seat back together. the other three pieces will need to be drilled on each end for carriage bolts. The smaller piece needs to be mounted 10" to 12" up the seat back. I used six 5/16" carriage bolts with washers and split lock washers. They have stayed put, but you might be more comfortable with nylon locking nuts. I also slid some vinyl tubing over the bolt threads to keep them from scratching the frame.

I screwed the 1"x10" brackets to the seat and seat back and had some problems with them pulling out if I wasn't careful. small bolts (maybe 1/4" carriage bolts) and washers would probably work much better.

See the three photos of the yellow bike for alternative bracket designs. Thee were created for a later project and seem to be stronger. I may retrofit.

After the first ride my lower spine was bruised a little; especially with the lack of padding. I cut out a bit of the lower seat back to relieve this. The seat was then fairly comfortable even without padding. However, padding was called for with rides lasting more than an hour or so.

Covering the seat was fairly simple. I found an automotive seat pad at our local overstock/closeout store for $2. I ripped all the seams and used its padding, foam and fabric. The idea is to staple foam to the seat and then stretch fabric around and staple it to the back. Its pretty easy. I've seen people glue wheelchair foam to the seat as well.

Step 13: Chain Management

You will need to make chain rollers from the skate wheels. The idea here is to get the chain under your seat without it rubbing. Drill 5/16" holes near the back and front of your seat (you may need to put the chain in place to figure out exactly where) and install 4" - 5" bolts. I used threaded rod and simply cut off the excess. Mount these with nylon locking nuts.

Remove the bearings from the skateboard wheels and chuck each one to your bench grinder one at a time. Use a sharpened screwdriver or piece of metal to carve a groove in the wheel. Wear gloves and safety glasses! The chain should fit in the rollers freely but not loosely and to a depth of about half the chain. Install these with nylon locking nuts.

Pick up something to use as a chain tube. Black 3/4" irrigation tubing works great. You will need between 2-3 feet. Feed the chain through the tubing before linking it together. The tubing will be mounted with zip ties just behind where the chain stays connect to the main tube. it should extend several inches past the front of your seat if possible. Make sure it's clean. Heat up the ends gingerly with a torch and flare each end out. A ball-peen hammer works good here. This will allow your chain to move through easily without getting snagged by the tube. Heat up the tube if it needs to be straightened. You want it to follow the natural curve of the chain to reduce friction.

Step 14: Finish Assembly

make sure that your crank is on tight and install the rear derailler. Splice your chains together (about 2-1/2 10-speed chains) and set up one brake. You may need tandem bike cables to reach the front brakes and rear derailler. Loose Screws Bicycle Parts is a good source for cheap cables and bits. I bought extra long cables for the entire project and cut them to size.

Only do one brake and just adjust the deraillers so you are in a fairly low gear as you may need to disassemble and adjust the frame. Ride in a parking lot and check for heel strikes. If you have heel strikes, you will have to remove material from the two front tubes, but not so much that your pedals hit the front tire. This is a pain. I had to remove 1.5" from my frame. Hopefully you measured correctly at the beginning. Cut it with a tube cutter to get nice straight cuts and try to find tubing scraps that will fit inside for support. You will have to bend the frame to make them line up as they are on an angle - this inner tubing helps hold things in place and will also help keep you from burning through the metal. Just be patient and try not to stomp around and cuss too much - you are almost there.

Step 15: Test Ride!

Ok, re-assemble if you had to cut some of the frame and test ride again - hopefully everything feels right. Mount and adjust the brakes, set up the deraillers, and give all of the hardware a once over. If you haven't already, give all the bearings in the steering tubes and the bottom bracket a good dose of grease and reassemble.

Remember that you will have a pretty wide turning radius as this bike's a little over 9 feet long! You should find that the low center of gravity makes this bike easy to balance. I think you will also find that it's pretty fast. I can easily get to 34 mph on smooth flat pavement. Keep in mind that your brakes may not be up to the task of slowing you down quickly from those speeds - they may melt if you aren't careful. Also, cars will probably have a difficult time seeing you. I don't ride mine on the road anymore unless I am with a group. Toe clips or clipless pedals are very nice to have.

You will almost certainly want fenders as soon as you are done with your first ride. I made mine with these instructions.

Paint it as soon as you have all the bugs worked out, and please post pics - I love to see what people build! This is not a terribly difficult build and the results are well worth the time. This is my favorite bike out of the 15-20 I own. It's comfortable and fast and always attracts attention. I'll keep an eye on comments, so let me know if you need a photo or better explanation - enjoy!