Tuesday, April 24, 2012

Construction of Utility bike

I could not find a bicycle like this to buy at any price; Easy dismount step through frame (18" ) ,  4.75” crank forward for sitting up straight to stop leaning on my wrists (carpel tunnel syndrome), full MTB gears, front rack on frame to not affect the  steering.  And I need it to be strong enough to haul cargo (no aluminum). Aluminum is ‘Planned Obsolescence’ designed to make sure you buy a new bike soon as possible!

How I invented my ‘new’ bike geometry.

Short cycle trucks were proven to be very popular during the Second World War. And Worksman Cycles have been producing them ever since. Because of my carpel tunnel syndrome I needed a seat that was 60 degrees from the crank to sit up straight.

Old commuter bicycles used to have 60 degree seat tubes to sit up straight. But when racers developed that front derailleur it was for a steeper seat tube so they could lean on the handle bars.

The Trek ‘Puresport’ and the Townie bikes have the same easy dismount geometry, but they are made for LIGHT duty cruising, not for hauling cargo.

All I did was to combine the old style commuter geometry and the new style gears and derailleurs.
Also Note how low (18”) the step though is and the steep steer angle (74 degrees) for maneuverability.

  I am able to turn in a very tight circle of only 105" or 8.75ft. This is very useful in a crowded situation.
              Build one or buy one: http://www.jonesbikes.com/h-bar.html
                         It has a 42.5" wheel base and weighs only 46lbs wiht out the box and fenders.

Paper work first, I recommend a Pickett 235E ruler, worth every cent!
And a 360° Adjustable Protractor 


Then add an extension from nova cycle supply, to an old fork.

when you take the old bikes 
apart, keep the old crank
spindle so it will be easy to get a new one that fits.
This wood jig is impossible to make square, should have used steel flat bar.

                                        I changed the steer angle to 73 degrees to get less trail,

                                                         for easy slow speed hill climbing.

Hand filing the joints is much harder than using a machine,

                          but it is easy to get them right. And square tubing is much easier than round.

Do not assume that the face of the bottoms brakets are square to the leingth.
I made a big mistake on measurements: the rear of thsi is for a 24" wheel. Now I must pay more to build a wheel. http://forums.mtbr.com/general-discussion/36-hole-pull-apart-hubs-806465-post9581280.html
I also gained trail, but not too much.
One Milimeter off in the center can mean one eight inch at the rear drop outs.

              Alignment with string is very difficult, better to use an expensive 'frame alignment caliper',

                                                     and a botom bracket holder jig.


MIG welding is fast and cheaper than TIG welding, but it can be cleaner if it has a foot pedal controller and the person using it knows how to keep the head tube and bottom bracket from warping.

                                             45dgree handle bars with hill climbing extension
                              Don't forget to measure every thing ten times and just before welding!
                                              Or you may have to do it over again, like I did.


old headset

frame shimmy and steering geometry
finding parts can be a bugger!
 Disc brakes
Head sets



Chain lube

                                 I should have Googled "frame building jigs" before I began.





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