Thursday, March 21, 2013

Introducing the Cruzigami Mantis

I have taken this week off and Kate, the monkeys and I went up to her parents house.  I had been hoping to get some bicycle riding in, but we drove up during a blizzard and have gotten a foot of snow this week (it snowed in Connecticut, too).  So I haven't gotten any bicycle riding in, but I did get to put the finishing touches on something I've been working on for the last few months.

I'd like to introduce the World's First (and currently only) Cruzigami Mantis - a folding, full-suspension recumbent moving bottom bracket (MBB) forward wheel drive (FWD) bicycle.  The goal in building this bicycle was to (1) have a bicycle that can be packed into a single suitcase including wheels (hopefully more on this later)  and (2) have this bike not compromise on the ride.

The Cruzigami Mantis - After

The Origami Mantis - Before

This bike is a fully suspended folding Origami Mantis bicycle converted into a FWD recumbent with a Cruzbike conversion kit (which includes both the seat and the front triangle).  From the original bicycle, I kept the frame, the fork and the kick-stand (replacing everything else). I have plans to use original parts from the folding bike to completely rework a Greenzone folding bicycle that I rode into the ground.

For those who don't want to bother reading what I have below, here is a video:

The rear wheel is a  used (former front wheel)  Alexrimm with a Shimano Deore hub that I got used from 'Bent Rider Online ad.  It came with the (slightly used) Primo Comet tires shown.  

The rear wheel and rear suspension.  I removed a guard that was attached to protect the chainring when it was attached in it's original position.

I use Shimano Acera V-brakes for both front and rear and XLC alloy V-brake levers mounted on a Wald steel handlebars attached using the same Dimension adjustable stem I use on the Sofrider. A Mirricle bar-end mirror and locking grips finish off the cockpit. 

The handlebars with the XLC brakes, SRAM trigger shifters, and Mirricle mirror.  You might also notice the Garmin 305 mount on the stem.

On the front brakes, I use  Kool Stop brake pads.  To keep the trail of the converted bicycle reasonable, the front fork is turned around when the kit is mounted.

The Koolstop pads with Shimano Acela brakes and Marathon Kojak tires.

The drivetrain is a FSA Gossamer triple crank which came with 50/39/30T rings where I replaced the 30T with a Sugino 24T granny gear.  Like on my Sofrider, I use Nashbar Soho pedals (one side clipless, one side platform).  I use an SRAM X.9 (10 speed) front deraulleur (I should use a 9 speed, but this was available).

The FSA Gossamer triple crank with the Sugino granny gear, the SRAM X.9 front derailleur, and Nashbar Soho pedals.

The front wheel has a Capreo hub and a 9 speed 9T-26T cassette (that I bought from another 'Bent Rider Online ad) shifted with an SRAM X.4 9 speed rear derailleur.  I use SRAM X.7 trigger shifters for both front and rear derailleurs.

The SRAM X.4 rear derailleur mounted on the Cruzbike conversion kit mounts. I haven't yet trimmed the shifter cables.

To allow the bicycle to still fold, I use wing-nuts to secure the two halves of the seat together and the bottom half of the seat is mounted such that it does not interfere with the bicycle fold.

The seat is mounted on the front half of the frame and does not interfere with the folding of the bicycle.  The seat pieces are attached with wing-nuts so that I cat attach them by hand.

Cruzigami Mantis Gearing

The choice of the Capreo 9-26T cassette was chosen so that this Cruzigami Mantis bicycle is geared almost identically to my Cruzbike Sofrider.  The Mantis, with its 20" wheels is geared from 17.6 to 106 gear inches; the Sofrider and its 26" wheels, is geared from 16.8 to 107 gear inches (For reference: a 700c wheel with a 23mm tire and 50T chainring and 12T cog has 109 gear inches).

Cruzigami Mantis Gearing (with 20" wheels)- the top (big ring), middle (middle ring) and bottom (granny gear) speeds for a cadence between 75 to 110 RPM.  Picture a snapshot of Mike Sherman's gear page.

 Cruzbike Sofrider (with 26" wheels) - the top (big ring)middle (middle ring) and bottom (granny gear) speeds for a cadence between 75 to 110 RPM.

The gearing and the tires were chosen to give this bike a ride as similar to a big wheeled bike as possible.

As you can see, although the bike still folds, it isn't nearly as convenient as it was in its original form.  The ultimate goal of this bicycle is to have it be packable (with the wheels) in a single airline-legal suitcase (hopefully more on this later).

Now that I finally have the bicycle assembled, now I'm just waiting for, well, roads that aren't completely covered in snow to try it out. Hopefully not too much longer and I'll be able to provide my first impressions of how it handles.

Threadless Fork

Unlike most folders I've seen, the Origami Mantis comes with a threadless fork (like modern road bikes).  As can be seen by the picture below, there is not a lot of stem sticking above the fork, so that it was difficult for the Cruzbike kit to grab a hold of it.. To solve this, I use Delta stem raiser that both attaches to the star nut inside and grabs onto the fork.  It's also works well in that I can remove the stem from the Cruzbike kit without having the fork fall off (will be useful for packing).

(It makes sense that the amount of the fork above the frame is so short because there is usually a foldable stem.  It just isn't ideal for this application.)

Threadless fork of the Origami Mantis and a view of the star nut inside.

Bike Folded:

Here are some pictures of the bike folded in the back of our mini-van.  None of these are fantastic pictures, but they do (pretty much) show what's going on.  Here is the complete bike except the seat back (and post) are removed.

Everything is folded except the stem.

Side view

Close up.

How to build a Cruzbike conversion - in 90 seconds

A lot of people are curious how to do a Cruzbike conversion.  Here's a video that I had nothing to do with (except encouraging Brian to make and post it).  It is a very cool time-elapse video that shows in 90 seconds how a conversion is put together:

Bryan's How to Build a Cruzbike Conversion in 90 seconds video


  1. How do you account for the dish in the front(rear) wheel? Most front forks are 110, and rear axles are 130-135, too?

    The concept of a kit-built MBB is interesting though...I would like to try a Vendetta one of these days. Maybe I could go faster than my usual plodding along at 12.6mph.

    1. Hi Vic,

      The Cruzbike conversion kit pieces for the fork are designed to provide the extra 25 mm of spacing. It might be possible on rigid steel forks to bend them so that this wouldn't be necessary, but this wouldn't work on aluminum or suspension forks.

      I'm hoping that once I get a shorter seat post, I'll reduce the seat angle and the aerodynamic advantage might help me go faster. I can't really afford a Vendetta... :)

  2. Charles - Very nice! You have proven you are a great craftsman. Can't wait to hear how it handles.

    - Randy

  3. I was wondering when I would finally see this creation. Congratualtions! It looks great! Now I want to know how it rides.

    1. Hi Randy and Paul,

      I hope to be able to tell you exactly how well it handles very soon. No snow here in Connecticut (just got back).

  4. Gorgeous. I anticipate reading your ride reports.

  5. Great stuff charles! I have not been following your blogs for a while. But wow, you've really been busy building some nice bike there! With the Capreo 9-26T cassette and the 50-39-24 crankset you seem to have even a wider range than your softrider!

    How is the stability of riding 20-inch small wheels?

    1. Welcome Ak-tux! Yes, I chose the gearing carefully because I like very much what I have on my Sofrider. It rides amazingly similarly to my Sofrider as well (I'm actually surprised how similar they are). 20" wheels won't do as well on rough roads, but this isn't an off-road bike (and the full suspension will help).

  6. Hello,
    I came here after seeing your post in the "show pics of your bike parked at work" in the commuter section of Bike Forums hoping to find some answers to questions I have. On principle I can't "knock" the build, but there are many things about it that bother me and hope that you could explain/educate me on.

    1) With the location of the "peddle assembly", on the other side of the stem and headset from the body of the bike; how do you steer the bike without having to remove your feet from the peddles?

    2) With your feet locked into the peddles, how do you extricate yourself quickly from them in a case of having to make an un-expected turn?

    3) If you do have to remove your feet from the peddles in order to turn, why is this a benefit?

    4) If you do have to remove your feet from the peddles in order to turn, what method is in place to apply power to the drive train, if there is none, why is that desired?

    5) In its unfolded, road going, configuration, what benefits does this bike have that the original could not give you, and in what ways do those benefits improve on the original?

    6) In its folded for stowage configuration, what benefits does this bike have that the original could not give you, and in what ways do those benefits improve on the original?

    7) Is there post or thread somewhere that has your riding impressions and lessons learned to date in it? If so, could you direct me to it?

    Lastly, I do not want to seem like I am insulting you, or the bike. My questions are genuine, and from a curiosity point of view because I can not figure out the answers on my own.

    Very Respectfully,

    1. Hi Tom,

      I'll do my best to respond. :)

      1, 3, and 4) This is the hardest thing about learning to ride a MBB (moving bottom bracket bike), turning while your feet are on the pedals. In fact, I advice people who are learning to take their feet off of the pedals when they feel like things are going badly. But after getting used to it, I can turn quite tight turns with no problems with my feet on (attached) to the pedals.

      2) I've heard it said that everybody who clips into their pedals falls. I am no exception. But I can get my feet out very quickly when I need to.

      5) I wanted a recumbent bike. I find them much more comfortable.

      6) The original Origami bike folded better than the Cruzigami I created. But the new bike folds well enough for what I want to be able to do.

      7) You can look at this blog entry or this thread on BROL.