Sunday, February 12, 2012

Tomahawk lowracer recumbent in Australia

Hi guys, this is my Tomahawk based low-racer recumbent bike I just finished and test rode today.

I have always been fascinated by recumbents, and on finding the Atomic Zombie website all those months ago, I knew I was ‘onto something’!

I ordered the excellent plans, but made a few changes during the build, with extra gussets here and there, and some different frame angles. I worked out all my dimensions and got all the frame angles calculated in CAD, especially since I used a composite moulded seat that I obtained from Ocean Cycles in the UK. This seat required different mounts on the top side of the frame to allow it to fit. The seat is really comfortable, and fits my back like a glove. Money well spent.

All parts on the bike are brand new, for peace of mind.

For parts like the derailleur hanger and caliper bracket, I drew the parts up in CAD, printed them onto sticky paper, then stuck the templates to 5mm thick steel to cut out and carefully grind and file to shape. The resulting parts look as good as CNC machined parts.

As it turned out on the first trial assembly, I had a chain rubbing problem on the underside of the seat. This needed another pulley to guide the chain around the lowest parts of the seat. The pulleys came from Hostel Shoppe in the USA, who specialise in recumbent parts. The drive pulleys have teeth inside, and the return pulleys are plain. The pulley ride on CNC machined shafts that are TIG welded to the frame.

The frame was all MIG welded from 1.6mm mild steel tube, and was put together by me in the workshop where I normally build rally cars! The front forks started life as 26” CroMo MTB forks (to get the caliper mount) but I chopped them down by 3” and sleeved them internally before TIG welding them up. The wheels are 26” rear and 20” front. The rear wheel was bought pre-built, for $75 delivered from Wiggle in the UK to Australia, where here, to just buy the spokes alone would have been $72! For the front wheel, I used a 20” Alienation BMX rim, and a Deore disc hub. I have built a few wheels now in my truing stand.

The alloy handlebars are from the UK, from a company that specializes in reproduction vintage bicycle parts. They work and fit perfectly. Brakes are Avid 160mm discs. All drive train parts came from a friend who runs the YellowBikeRoad eBay shop.

The frame was powder coated in Dulux bumpy paint. Close up it looks great!

For the test ride, I chose a closed road, to avoid traffic. Riding a recumbent is certainly different, but not particularly hard. I found the steering a little twitchy. I think I will get used to it. I managed a turn in the road on my first run up the road. I still have some clattering noises from the front and rear derailleur whilst the cables stretch. All that will be adjusted out. My legs ached a bit after my test run, but only because you use your leg muscles differently riding a recumbent. More getting used to!

I have also mounted some bases for my GoPro Hero2 HD camera on the front boom, and off the rear fork to look down the side of the bike.

It was a lot of work to build, but to stand back and look at it and say ‘I built that’ feels good. I take pride in anything I build, and if it’s worth doing, it’s worth doing well. It will feel even better to tell others that I built it when they ask where I got the bike!

Cheers – Rob Greaves
Sydney, Australia.

Well done, Rob! What a feeling knowing that you built this yourself!

You can build your own Tomahawk lowracer recumbent just like Rob did.

The Tomahawk Lowracer is all about the speed! The extremely laid back seating position means that you will always be able to deliver your full energy to the cranks, as well as cheat the wind in ways that are impossible on a standard upright bike. The short wheelbase configuration offers agile and responsive handling characteristics that make it feel as though you are piloting a jet fighter.

The building process is designed to allow anyone with a Do-It-Yourself desire to finish his or her own version of the Tomahawk without requiring previous bike building experience or specialized tools and skills. The plan is laid out in a format that makes customization or alternate parts usage a breeze, so you will certainly be able to include your own imagination in the process of building a fast lowracer.

With the adjustable bottom bracket and unique frame design, riders with shorter legs will be able to pilot the Tomahawk without dealing with crank interference with the front wheel. Before you start cutting your frame tubing, it is a good idea to read the entire plan so that you understand how modifications may affect the rest of the build. There is plenty of room for your own design changes, and the Tomahawk can be built using the parts you have available to you.

Take a look at our Builder's Gallery to see some other lowracer examples, including many creative modifications to the plan. Our international builders community ranges from students to retired engineers, but they all have one thing in common - the desire to build their own stuff!