Construction Diary


pdf plans here


3D render of Jetrike frame

Some time in May 2007

Modified Jetrike Frame.

  • Lowered the seat.
  • Shortened the wheelbase.
  • Changed the rocker arm angle to 110.
  • Changed the right stay on the Drive Train to provide more chain clearance for my 60 tooth chainring.
  • Adjusted the backrest angle and seat angle.
  • Added a front caliper brake mount.
  • Added a rear pannier mount.
  • Added a front light mount.

10 Mar 2007

  • Painted the frame.

Painted Frame

3 Mar 2007

  • To correct the Trail, I cut the main pivot hinge off the Drive Train, adjusted the angle by 10 and rewelded it back into place. This is one of the grate things about Steel construction. If you make a mistake, you get a second chance!


Finished Frame

24 Feb 2007

19 Feb 2007

17 Feb 2007

  • Attached the Steering Tiller to the Drive Train
  • Mounted the Seat onto the frame.

16 Feb 2007

15 Feb 2007

14 Feb 2007

  • Took another three days off work - this time I will finish my trike!
  • Cut an M10 thread on left the Dropout.
  • Welded Swing Arm Bushes and drilled and reamed out the rear axle mounts.
  • Tack welded Swing Arms ready for alignment.

10 Feb 2007

9 Feb 2007

8 Feb 2007

7 Feb 2007

  • Took 3 days off work to try and finish my trike - but didn't.
  • Sourced more materials from our local steel supplier Shoe Steel. Fortunately I hadn't welded either the Steering Pivot or the Rocker & Swing Pivot bearing housings yet, so I can use them as-is on the new MkII design. I pretty much had to repurchase all the steel in the new cut list except the for the stainless used in the seat.
  • What should I do with the drive train and BB mount I already made? Build a Python Lowracer of course! Waste not, want not.
  • Machined the Dropouts.
  • Machined the Frame hinges for the Swing Arm and Rocker Arm Pivots.
  • Machined the Rocker Arm parts.
  • Machined the Swing Arm Couplers.
  • Machined the Swing Arm Bushes for mounting the rear axle.

3 Feb 2007

  • Drafted up the new Jetrike MkII plans.

27 Jan 2007

  • I spend the weekend completely redesigning Jetrike (MkII) from the ground up using a seat angle of 21 and a new drive train similar to the Speculoos developed by Laurent Dechenne <> i.e. the bottom bracket height is level to the seat height, 100mm positive trail and a pivot angle of 55 to 60. My hope is that by following his recipe, pedal induced steering will be minimal.
  • I also rebuilt the simulation in a way that totally isolates the vertical and horizontal movements. In doing so I discovered that Angle C is much better to use than Angle B for generating the self-centering effect, because the tilt angle before lock is actually greater.
  • I also realized that the rod ends in my earlier designs would have been pulled laterally beyond their specified limits, so new offsets were introduced into the simulation in order to bring the rod end movements back within their stated tolerances.

24 Jan 2007

  • Mark Schaaf voiced some concerns he had on the Python Lowracer list <> about my Jetrike Rev B design based on his experiences with a tilting python trike he built (pictured above). It has a flevo trike style back end, and a long wheel base, but he found that on a corner or at walking speed, the front frame would tip over to the outer site of the curve while braking. He also reported inferior handling when he attempted to carry any sort of load. This started to make me feel a bit uneasy about the whole python drive train. Maybe I should design a FWD trike with positive trail first, then once the self-centering geometry is perfected, experiment with negative trail.
  • Dirk Bon also posted a link to a document on "The Affect of the Posture and Rolling Resistance on the Required Effort to Ride a Recumbent" <diary/DeMeetligfiets-English.pdf>. Needless to say, this is required reading for anyone interested in higher performance recumbent bike designs. This lead me to experement with lowering the seat angle to 21. But would a python drive train be stable with such a low seat angle?

20 Jan 2007

  • I finished cutting out all the items in the Cut list.
  • I finished the BB Mount, which included hollowing out the sleeve sides, machining, taping and welding on the binder and fabricating the front derailleur post and welding that on.
  • Cut, sectioned, bent and welded the Fender, which is ready to be attached to the drive-train.
  • Machined the pivot mounts for the Frame.
  • Started machining the Swing Arms.
  • Announced the "New Look" website to the Python Lowracer list <>,

18 Jan 2007

  • Picked up the bearing housings from Bents engineering. They did a very nice job machining the Steering Pivot and Rocker & Swing Pivots. The total bill for this was $150 AUD, which when compared to all the money I have spent on the other bicycle components, was well worth it.

13 Jan 2007

  • Sourced all the materials from our local steel supplier Shoe Steel. They sell steel by the meter, so you can just buy what you need.
  • Droped off the stock for the pivots to Bents Engineering to machine the the Steering Pivot and Rocker & Swing Pivots bearing housings.
  • I spent most of Saturday afternoon just tidying out the shed to get it ready for this project, then I started by cutting down the 40 x 40 profile, which you can read about in the section on constructing the Drive Train.
  • On Sunday I managed finish my 40 x 10 profile and so only spend half a day actually cutting metal and welding bits together. I ended up only getting a bit of the Drive Train and a bit of the BB Mount done.

10 Jan 2007

  • Posted some notes on the Jetrike geometry to the Python Lowracer list <>,
  • Once again got lots of feedback and discussion ensued.

8 Jan 2007

  • Posted Jetrike Rev B plans to the Python Lowracer list <> -- the big changes included:
    • Regular python drive train to fix the chainline problems,
    • A Front derailleur post on the BB mount,
    • Stiffer triangulated frame,
    • Stiffer seat mounts,
    • 3mm plate on the rocker arm end caps
    • Improved tilt geometry
  • Once again got lots of feedback, causing numerous design changes.

7 Jan 2007

  • Machined a BCD 135 to 110 chainring adapter using a solid 44 tooth BMX chainring.

4 Jan 2007