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Farthing Penny Arm Assist Grocery Bike 2013:  VIDEO

 

Description: Arms can assist pedalling for extra peak power, reduced leg muscle fatigue and full body exercise (as in the frontrowing rig).

    The low stemhead  on the Farthing Penny due to the small “farthing” front wheel  suggested  a U handlebar that would clear the bucket even when raked forward. Then hinging the bottom of the handlebar would allow a forward and back oscillation of the straight handle crossbar crowning the uprights.  During this rowing, steering can still be effected by opposing the arms. Pushing against the body weight on the saddle, the forward stroke pulls a chain around a BMX 16T ‘Southpaw” left-handed freewheel on the left side of the rear wheel.

      The key control mechanism is a pin which is sprung into a plate with an arc of holes to lock the handlebars in various fixed rakes and for support during braking. It is unlocked by a Bowden cable when the rear brake lever is held open beyond a limit set on the rear caliper opening.  As soon as the right fingers stop pushing the lever wide open, the spring locks the handlebars for support. The locking pin engagement in a hole will be visible for extra safety

      The  arm-pumping gives a welcome boost to keep the mean speed up and avoid downshifting on grades and gives a whole body workout. Exhaling hard  in the forward push achieves synchrony of the two chest-tightening actions.

      The handgrips inside of the uprights protects the hands and  narrows and compacts the bike for less windage, safely sharing narrow paths with pedestrian and easier storage.  Dangerous bottoming out of the brake levers, and snagging by the levers and handlebar ends are all eliminated..

      Besides locking at forward rake, one can crouch by holding the handlebars at the bottom of the U. This,and carrying cargo in 1 hand needs a backpedal brake for safety

     The latest 2013 model has stronger ¾” pipe steel instead of 1” x.9 tube for the stemtube. At 1.050x.824” it just passes through 1” standard stem bearings because the cones are 1/16“ oversize. The opposite ends of a ¾” cast iron T are bored out to accept the handlebar cups. The T is screwed tight onto the end of the stem pipe into alignment with the forks with a sleeve machined for the right stem bearing tightness. Then the sleeve is Nickel tacked to the T and the locking pin barrel is welded across the sleeve at 2.5” radius. The handlebars were bent cold with a pipe hickey with the T and bearings and a slit clamp loose between the bends.  The pin engages  holes in an aluminum sector TIG welded on the backside to the handlebar and seating a cone on the inside. The adjusting cone on the other side seats on the slit clamp tightened on the handlebar tube.  The locked handlebars are very stiff and strong to decelerate the rider in hard braking.

    The top crossbar  of  1”x7/8” aluminum was miter TIG’d to the uprights. Its stiffness is now exploited to just bridle between the inboard clamp ends of dual front brake levers that pull symmetrically through crossed Bowden loops that flow with the handlebar into the horizontal linear pull front brake from both sides with a center nicopress wire joint  The brake arms are cantilevered on the back of the front fork to not interfere with the bottom support of the cargo bucket (pronounced “Bouquet”!) just above the small front tire and clear of the fork crown.

     Pushing the extended-range right brake lever open pulls the pin through a third Bowden cable to unlock the handlebars for armpower assist. The bridle snaps onto the eye end of a wire passing through a pulley swinging on weldment to the frame of the saddlenose. This point gives the best pushing angle and least pulley contact. Now the slack side of the chain passes over an idler welded to the inside of the chain stay and then under the chainstay and bottom bracket to a shockcord and then around a sheave just shy of the front fender to return to the back of the seat. This rearrangement means the chain return is now using gravity not fighting it as before and further from the trousers. 

      Independent of the hands and handlebars, the rear wheels cantilever brake is applied by my backpedalling mechanism.  A single standard diamond road frame was cut reversed and rewelded at the front lugs of the seat-tube front joints to give the small (Farthing) front wheel with room above for the cargo bucket (pronounced Bouquet!).The design is easily made into a “Farthing ha’penny” folding bike; conversely a folding bike is improved by backpedal braking, armpower, and bucket cargo.

    An improvised die cut left hand threads on the aluminum hub of an existing spoked wheel for the 16T ACS Southpaw freewheel for the left hand arm assist drive. Most hubs are about the correct diameter on the left hand side so lefthand threading  with the “tap” die avoids tedious unspoking/spoking. In the 1.375”x24tpi LH die the .330” tap holes are evenly spaced on a circle of 1.705”. They are tapped with the same the 3/8-24 right hand tap through a faced nut vised against the plate and progressively rotated 120 (2 corners) clockwise in clockwise succession. The die can be adjusted by locknutting the taps so their cutting edges are not quite radial to the big circle. It is best to have the 16T ACS Southpaw freewheel and remover in hand to test tightness.

 The frame design began with ubiquitous 5 gallon bucket and the cheap pail organisers that are mass produced for the building trades. These hang over the bucket rim with numerous pockets on the inside and outside. The inside pockets are useful for small valuable ‘purse’ items like a notepad, cheque book, pens and mobile phones which help prevent fruitless tiring cycling. The outside pockets are good for spare inner tubes, glasses cases, bike tools etc. Instead of adding wind resistance, a front mounting provides a bit of a round entry fairing to the body behind. The maximum 45 lbs of 5 gal bucket full of liquid then evens the weight on each wheels at 100lbs for a 175 lb adulta standard bucket to transport cargo (mainly groceries) in living without a car and a bucket organizer as a sort of bike purse.

 A smaller front wheel lower the weights of the cargo and the top of the bucket below the arc of the handlebars. The grocery delivery and Paschley Post Office bikes in the UK have slightly smaller front wheels under their trays attached to the frame  The stability and control of a bicycle are largely governed by the steering front wheel, and folding bicycles have shown that a small front wheel has very good balance as well as high manoeuvrability.

 But the standard rear frame is a lighter way to stiffly support the seat and a fullsize rear wheel allows light yet high derailleur gearing. So the idea was to just change the frame ahead of the seat-tube to allow a small front wheel but to keep it and the handlebars stiff.   Since the steering tube is parallel to the seat tube, the front end can be lowered by cutting the front and top tubes at the seat tube. For a match the tubes should be cut at the same angle to the seat-tube. Since the original top tube is smaller it should be cut say ¼” minimum clear of any lug, so that the downtube can then locate over this stub flush with the lug. The downtube  should be cut at its lug outer edge for this. The clean end of the downtube will fit inside what is left as deep as possible. The overlaps and lugs if present allow stick welding

A bracket to hold the bottom lip of the bucket is welded to the bottom of the steering tube just above the tire, and a circle of banding strap projected from the top of the steering tube holds the bucket dropped into place.

 

 


    

        

 

 

 

sts

Cargo bucket holder, armpower chain

trailer.02s

 

T- Bearing, Locking Barrel, Front Brake

 

dtrs

Bridle,Saddle Pulley and Locking Pin from Below

 

 

 

Taps locknutted to back off cutting edges for tightness on LH bearing cup.jpg

 

Setting die for depth of cut against left hand bearing cup (undersize) by locknutting cutting edges vs tightest radial.

 

Die then edge- clamped in vise and hub fed down and left handed into it by hands turning and loading rim parallel to plate.

 

(Panniers require extensive frames and support points to keep them out of the spokes, complicating removal. In the front their weight and volume capacity is limited by turning with the wheel. Rear panniers or racks do not allow monitoring the contents when riding and add extra spoke-breaking load to the rear wheel which already bears 110 lbs  of a 175 lb  rider.  Backpacks have a particularly high center of gravity again too far back and exacerbate the differential cooling problem that leads to a wet and clammy back yet a frozen front.)