Saturday, December 27, 2008

Front Wheel Drive Rear Wheel Steer Recumbent

Many of you might wonder why build a recumbent with front wheel drive. Why not stick with rear wheel drive? Well front wheel drive provides may advantanges. First is that it requires much less chain than a normal recumbent. Second is it reduces weight by needing less chain and chain guides. Third in slippery situations like sand or an oily road the front wheel pulls the bike through the mess which is easier than the rear wheel trying to push the bike and rider through slick situations. The same holds true in cars.

So if front wheel drive is so good why do most bikes have rear wheel drive? Well there are more and more recumbents entering the market all the time with front wheel drive. The difference between my design and others is that my design steers with the rear wheel. Most other front wheel drive recumbents still steer with the front wheel. Others like the Flevo and Python articulate just behind the front wheel. Still others like the Cruz Bike steer with a head tube in a normal fashion. The problem with these designs are that they have a lot of pedal steer that has to be compensated for by man handling the handle bars at high pedal power to stop excessive wiggle. This uses a lot of energy and strain the arms. The rear wheel steering removes pedal steer. This improves peddle energy efficiency. This makes for a smoother more efficient riding machine.

So what is the down side of a front wheel drive rear wheel steering recumbent? I suppose it is the learning to ride such a bike. It still feels like a bicycle but has a slower rhythm. At least that is the best way I can describe its handling. It is a very relaxed ride. Still learning to ride one is a new adventure.

Summery: It is my opinion that this design has very good potential to make a more efficient recumbent. In a lowracer design this configuiration could push the efficency envelope farther forward. I am currently working such a design.

6 comments:

  1. Dennis,
    Here is a FWD Low Racer Recumbent that might give you some ideas for your work. It is lsted on Bent Rider's Site for sale @ $1000. There are some photos on the listing... Here is the link to the posting:

    http://www.bentrideronline.com/messageboard/showthread.php?t=45643

    Preparing for my move to Australia currently located in Columbus, Ohio and have to leave my lowracer behind. Dual 20"(406) wheels, Front Wheel Drive, 8 speed widerange cassette, disc front brake/ caliper rear, 31 pounds, steel frame, 8.5" seat height, 33" minimum in-seam(crotch to pedal) using a 172.5 crank(fixed boom). 2/3 step drive makes gearing comparable with 700 wheels.
    Dura Ace crank, friction thumb shifter, deore LX deraileur. Have sprinted it to 35-36 mph. Been on several multi hour rides. Never had any front wheel slippage. Built and modified over the past year. $1000 or best offer

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  2. Dennis,
    Love the blog, great explanation on the value of a front-wheel-drive recumbent. One of these days, I too hope to have a front wheel drive bent. I also enjoyed watching the video clip showing the progress involved in creating Maggie’s recumbent.

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  3. Hi Dennis,
    Would you believe me if I tell you I have something like that in my basement? I started to work on the design last summer, doing all the energy calculations in Matlab and also running it through JBike. Then I made most of it but the inverting steering. I really couldn't get it to work with the inverted steering, it seems the brain just doesn't like to turn left to go right. Seeing your bike is really encouraging, I have to get that inverting steering in! You said already that the trail is 45" and the head tube angle is 71 degrees. In addition to that what defines the system according to my calculations is the trail and the position of the center of mass (X,Y). That is given mainly by the position of your hip, where your hip bones touch the seat. Do you think you could share that?
    Are you familiar with the Velaero? It's the same but needed to move the steering axis a bit back. I also tried all this with a model first. The RWS does not have a self-stable regime, but it's sterable. You can find my videos on this if you search crisbolle on youtube.
    I look forward to hearing from you!
    Cris

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  4. your bike is awesome! is there anyway that i could get the geometry specs from you. I am part of a senior project team at Cal Poly San Luis Obispo that is engineering a human powered vehicle. We would love to build a test model of your bike to see if it will handle high speeds. What is the best way to get in contact with you? Thanks in advance.

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  5. I can't believe this site isn't more popular. I just discovered it and am very pleased. I've been wondering about just such design for ages, but what I read on the Internet from 'engineers' led me to believe that the physics made it too difficult to be practical. Your video certainly demonstrates otherwise. I WANT ONE!!!

    John Lambert
    Paris, France

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  6. Hi Dennis,

    The FWDRWS is phantastic! Would you like to publish some construction details? You got menshioned on this site: http://en.openbike.org/wiki/File:FWD_Pictures_108.JPG

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