RaptoBike Mid Racer: a front wheel drive recumbent

Miscellaneous 12 19

I am certainly no expert on recumbents, but I do appreciate seeing interesting recumbent designs from time to time and I am always interested in learning more about them. When Arnold Ligtvoet from RaptoBike sent me some information about his latest bike, the fact that it was front wheel drive with an innovative way of adjusting the frame length is what immediately caught my attention. I asked Arnold to elaborate on the Mid Racer’s ‘splitting-frame’ feature, and that is what I want to share with you in this post.

First, I will mention that most recumbents have a ‘noseboom’ to allow for length adjustable to accommodate riders of different heights. The noseboom is generally a tube sticking of the front, which holds the bottom bracket and slides in and out of the main frame tube. When you slide the noseboom to vary the length of the front beam, the chain length needs to be adjusted as well (and most recumbents have pretty long chains). The Mid Racer gets around the traditional noseboom construction by dividing in the middle (under the seat), so that as the wheelbase changes, the front layout remains the same.

Arnold can do a much better job explaining his design than I can, so read what he had to say about the Mid Racer below.

“After my first bike (the Low Racer) I had some further ideas. It occurred to me that if I made the length adjustment of the bike behind the drive train, this would mean that I could develop a bike with a fixed drive train and even importantly a fixed geometry at the front.

The fixed drive train combined with the splitting frame has the advantage of being able to quickly adjust the bike to the length of the rider, without having to change the length of the chain. It gives an added bonus in the sense that the bike can be taken apart in two sections for transport for instance. It’s not a folding bike, nor was it designed to be that. The drawback of making the bike change it’s length by splitting it in the middle is that, as the wheelbase is shortened or made longer, the handling of the bike changes. To counter this we have designed the main tube to slope. The amount of sloping needed to counteract the change in size of the wheelbase has been calculated with an application called JBike6. JBike6 is a computer program that determines the stability of bicycles and was developed by Delft University of Technology & Cornell University. As far as I can tell now it is the first commercial bike that has been partly developed using this application.

The added bonus of the fixed front geometry is that we could design the bike to fit a large portion of potential riders. Some recumbents, mainly the faster ones, have an issue where the bike, when set to shorter riders, does not allow for enough room between the cranks and the front wheel. Shorter riders either can’t ride the bike or forcibly have to use short cranks. This is never the case with the Mid Racer as the whole setup never changes, so shorter riders can ride the bike without this problem.

The bike has become quite a versatile machine. It can be fitted with most any type of brake (vbrake, disc brakes and race calipers) and can be delivered with 2×26″ for touring and commuting. People wanting to race the bike can opt for 2x700c as well as the bike is shown in the picture.”


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12 Comments

  1. Whizbo February 12, 2010 at 10:09 am -  Reply

    How do you steer this thing, and not screw up the chain alignment?

  2. Arnold – RaptoBike February 12, 2010 at 10:49 am -  Reply

    Hi Whizbo, just just simply steer it and the chain flexes to absorb the torque. The pulleys that guide the chain are a bit wider than the actual, so most of the flex/torque absorption is done there.

    I've sold bikes with a similar chain routing for close to three years now, so the theory works well in the real world (also when riding through busy cities).

    I would have made a small video, but winter is still here….

    Arnold
    RaptoBike

  3. suganick February 12, 2010 at 11:14 am -  Reply

    I was never much of an observer of recumbent bikes but this is some great innovation! I this is a great start for some awesome future products. Paint/materials could really make this pop. Great work!

  4. Michael February 12, 2010 at 1:18 pm -  Reply

    It is great to see this innovation and to have another "front wheel drive" recumbent in the market besides our "front wheel drive" recumbent trike. http://www.Sidewindercycle.com

    Michael

  5. coundetu February 12, 2010 at 5:19 pm -  Reply

    'bents aren't bikes. Not really…

    • Dan December 28, 2010 at 6:53 am -  Reply

      neuropathy, tissue damage, strained necks, aching backs and
      leg edema … they don’t exist with DF’rs. Not really.

  6. Stupid_C February 12, 2010 at 7:02 pm -  Reply

    This is the raptobike I've been waiting for! The original low-rider looks amazing but a little too low for my commute, this on the other hand looks to be a perfect compromise of speed and visability. If the price point is as good as the "low" then I'm seriously interested!

  7. Anonymous February 14, 2010 at 10:33 pm -  Reply

    I have ridden several FWD recumbents over the past 7 years, they have been around much longer than that. I assure you, the concept works fine. The drivetrain stays somewhat cleaner because there's nothing in front of it to throw up slop, like you'd have with a RWD. The factory bike I rode was a Flevo, apparently no longer available. My current ride is a homebuilt Flevo replica. It's wicked fast on my slightly hilly 25mi WV commute. It's getting close to time to replace it though. Good to see there will be an available alternative – hoping to see luggage racks and fenders available as I'll still be using it to commute. A fairing would also be nice.
    As a point of interest, the bike that currently holds the world's speed record of 83mph (unpaced, standing start) is of this configuration. Georgi Georgiev's Varna.
    Nick Hein, WV

  8. John February 15, 2010 at 9:45 pm -  Reply

    Bents are bikes, really. I race a Scott Addict R2 and consider this every bit as beautiful as the Scott. Brilliant, simply brilliant.

  9. Anonymous February 17, 2010 at 3:38 pm -  Reply

    One of the most amazing aspects of FWD is the ability to add Arm Power. This adds about 1/4 HP and Tom Traylor was beating everything faired or unfaired @ HPV events 25 yrs ago.

  10. kate February 20, 2010 at 2:57 am -  Reply

    Whats the feeling of riding this bicycle?

  11. Luk Wynants November 23, 2010 at 9:58 am -  Reply

    I’ve tested this bike some days ago and it was fantastic! Very stable and comfortable ride. Got home and ordered a framekit right away! (Currently 10% discount for pre orders)

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