OUR ADVERTISERS

Sunday, September 09, 2007

HOW TO BUILD AN INEXPENSIVE SUSPENSION RECUMBENT BICYCLE AT HOME PART 2 THE FRONT BOOM

Before we build anything, we need some more parts. You need a road bike frame and fork. The fork will be used to connect the front boom to the frame and you will make the front boom from the lower part of the road bike frame. See and enlarge the image. You will also need the top tube of that bike to make the steerer tube extension which will be covered in the next post.

So you had some fun with the hacksaw and you have all your bits, let's start. I removed the bits of the seat tube on the mountain bike frame since they won't be needed. This will save just a little weight as well. Not a lot, but homebuilt recumbents are notorious for being heavy, so every little bit helps.

Now I have a drill press, but since most of you out there don't, I will use a regular drill to make my holes so you can see that it is possible. 15 years ago when I built my first recumbent I had a revelation when I realized that a fork steerer tube would fit almost perfectly inside a seat tube. That's where all those road bike frame parts come into play. Cut the lower frame of the bike as illustrated in the first image, cut more and remove some length later if it's too long. Now set that piece aside after cutting a slit about 4 inches long in the seat tube where it will be inserted in the steerer tube. This will help when installing the clamps in final assembly.

Now take the fork and cut it at the end where it starts to curve. Close to that cut, drill a hole on each side. Make sure that your holes are aligned. Now slide the cut fork in the mtb frame so that the steerer tube faces forward. See where you want to make your holes in the mtb frame and mark them. Drill the holes and bolt the cut fork into place. Voila, you have done the first step in building the front boom. The front boom will hold the pedals, crankarms and front deraillleur.

Noticed that we only installed one nut and bolt, this is to permit you to see where you want the boom assembly to sit. You want to make it as level with the seat as possible and high enough so you don't hit the wheel with your feet when turning and pedaling. At this point, it's educated guesswork since we have no seat, so do the best you can or wait for the end of this story. Building a recumbent yourself involves a lot of guesswork and return visits to the drawing board. Heck, that's half the fun. :) This recumbent will most probably end being the kind that you hit the wheel when you pedal and turn sharply. I don't have a problem with that since I found a solution for me some years ago: don't pedal when you turn.

After finding where you want the boom to sit, mark where your holes will be and drill them. You might end up with a gap between the fork legs and the mtb frame. Fill those gaps with washers and make sure to use the same number and size on both sides. Your boom must be aligned with the rest of the frame. Bolt down tightly and you will check those bolts for tightness after a few miles when it's done, if you have half a brain.

Lastly, insert the road bike seat tube that you cut into the steerer tube and admire your progress. At this point we don't have a seat and we are pretty clueless on where it will finally end up. So for now we will leave it alone.

The next post will cover the handlebars and how to make an extension for them.

Until next time, ride safe and Godspeed.

Gerry :)

Recumbent build Part 1
Recumbent build Part 3
Recumbent build Part 4

1 comment:

Anonymous said...

Man, I wish I had the skills and the patience to build my own recumbent! Very cool!

On a different note, could you please do a post on how to optimise your gears? I for one only use 5 of the 3x7 available gear settings on my bike, so it kind of feels like I'm carrying dead weight around with me! Thanks :)