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     2017 UpdateEconologica.org
Farthing Penny Arm
Push Power Grocery Bike
2013: VIDEO N.B YOU assume ALL responsibility in using this FREE webpage info
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. (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.)
to make the Farthing Penny compact luggage
if required.)
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