Extra Information:

Books1: Bicycling Science. Frank R. Whitt & David G. Wilson MIT Press. USA 1974/1982. 0-262-23068-2

2: Pedal Power. Edit. James C. McCullagh. Rodale Press. USA 1977. 0-87857-178-7

3: Human-Powered Vehicles. Edit. Allan Abbott & David G. Wilson. Human Kinetics Publishing. 1995.

4: Velomobile Design. Danish Technical University and Danish Cyclist Federation Copenhagen. 1993. Fax: + 45 33 32 76 83

5: Bicycle Design. Mike Burrows. Open Road Publishing. UK 2000.

6: The Bicycle Wheel. Jobst Brandt. Avocet Inc. Palo Alto Caifornia USA 1999. 0-9607236-6-8

7: Richard’s 21st. Century Bicycle Book. Richard Ballantine. Pan Books. UK 2000. 0-330-37717-5

8: The Super Handyman’s Big Bike Book. Al Carrell. Prentice Hall Publishing. USA 1973. 0-13-875989-8

9: DeLong’s Guide to Bicycles. Fred Delong. Chilton Book Company. Radnor, Penn. USA 1978. 0-8019-5846-1

10: Bicycle Repair Book. Fred Milsom. Haynes Publishing. UK 1997. 1-85960-135-9

Internet sources:www.ihpva.orgwww.zechlin.comwww.ihpva.orgwww.pashley.co.ukwww.pashley.co.uk/landrover/landrover.htm www.windcheetah.co.ukwww.workbike.orgwww.brox.co.ukwww.bikeculture.comwww.sustaintech.comwww.villageearth.orgwww.jademountain.com/appliances/alttools.htmlhttp://users.erols.com/mshaver/bikegen/htmhttp://www.los-gatos.scruznet.com/pedgen.htmlwww.bikesatwork.comwww.elite-it.com www.ata.org.au

The Amazing BicycleWheelbarrow Part 1“The Ho Chi Minh” - a 10 Speed Wheelbarrow

A new variation on an Asian themegreatly extends the carrying capabilitiesof the bicycle. What is more it can bemade in a home workshop and can save youlots of money throughout its working life.It's easy to ride too.

by Ian Grayson

The more I thought about it the moreI became convinced that bikes are tooshort. They cannot carry all that needs tobe carried and pulling trailers is hardwork. The other option, a tricycle as usedextensively in Asia for transporting bulkyloads, is cumbersome. It is slow anddifficult to manoeuvre in city traffic.

A hybrid came to mind - a crossbetween a tandem and a trailer, a sort ofbicycle ute. Something that could carrycheap vegies from the central market 7kilometres away by the boxload withoutbreaking my back.

I decided to constructsuch a machine by welding2 bicycle frames togetherin a special way.

Now finallycompleted, itexceeds mywildest ex-pectations.

It is such a practical machine that I haveall but abandoned riding my regular 10speed in favour of it.

Luggage capacity on a normal bicycleis poor. Bikes are built primarily tocarry the rider - luggage is anafterthought,

The mania for short wheelbasesoriginates in the guest for stiffness andhence a marginal gain in efficiency, byracing cyclists. It has nothing to dowith functionality for commuting ortouring.

I decided to weld a basket along thelength of my long bike - a big basket,"sculptured" around the rear wheel.

Although heavier than a normal bike,the trade off for functionality, carryingcapacity and comfort make it well worthit. In any event the revolving weight, theweight that really counts, is not thatgreatly increased - just some extra chain.For a long bike it is also very stiff, thewelded basked itself stiffens itenormously.

The "Ho Chi Minh" as the machine hasbeen named, fulfils all the criteria forthe Small is beautiful philosophy. It is more efficient than a bicycle/trailercombination and a tricycle for carryingcertain loads by still having only 2

wheels on the ground - thus less drag and friction.

Third WorldDuring my extensive bike travelsthroughout India and Asia,

(having hardly had my bum offthe saddle for six monthsduring one stretch), Iobserved closely all thenumerous and ingeniousapplications of pedal power.

Single speed roadsters areeither loaded to the hilt or a longtricycle is used. There is nothing inbetween. The concept of lengthening abicycle to increase its carryingcapacity has been completelyoverlooked, despite the obvious needfor such a machine. As a deliveryvehicle it is ideal. (Posties andcouriers in the city give it morethan a second look!).

Its third world applicationscould be considerable. Its ability togreatly increase the range for muchload carrying would greatly assistvillage life and inter village trade.Firewood collection and water cartingwould be made simpler and easier.Many of the loads being pedalledaround in China and Africa forexample, by cumbersome trikes, could bemoved with less effort, more speed andmore manoeuvrability by a machine of thisnature.

It is this application whichinterests me most and I would beinterested to hear from anyone or anyorganisation experienced or interested inpromoting such an example of intermediatetechnology in the less "developed"countries where it would be of most use.

Long lengths such as ladders, timberlengths and bamboo poles can also becarried in a simple manner. By strappingthem to the outside of the long basketalong the length of the bike, from thefront forks to beyond the rear wheel, theyare thereby held rigid, and the leg strokeis not interfered with. 20 foot lengthscan be carried in this manner - evenwhilst riding through city traffic.

A small child can also be carriedaround sitting in the basket, which ismuch safer being lower down.

As a workhorse on farm or commune itis a virtual 10 speed wheelbarrow. Bricks,building materials and timber can behauled along narrow tracks. Not to mentionfruit, vegies, firewood or compost.

A house or shack could be built in an

area inaccessible to motor vehicles.(For those like myself who abhor the

motorised society with its casualties,waste and pollution, this opens upinteresting possibilities...).

Bulk shopping once a week for anaverage family is literally a breeze onthe Ho Chi Minh. We shop once a week onlyat the Adelaide central market and reallyload it up. The 14 kilometre round trip iseasier on the Ho Chi Minh than on anyother pedal powered option.

Another important feature of thismachine, The most important feature, sofar as any appropriate developmentapplications in the third world areconcerned, is its ability to be locallymanufactured and maintained,

A single person with oxy-acetylenewelding equipment and basic metal workingtools can make this machine from basic oldbike parts and scrap in about 3 weeks. Imade my first one without any electricaltools - in fact without any electricity atall!

The only high tech. vulnerable anddifficult to replace part of the bike isthe gearing system (and possibly the cabletechnology).

Presently I am working on a 3 speedgearing system which is robust,maintenance-free, everlasting and can bemade from recycled materials with no cabletechnology. (Comprising of 3 old differentsized chainrings bolted together with acrude spring tensioner for the chain and arod-operated changer.)

Self-sufficiencyFor country dwellers a couple of

these machines can offer real selfsufficiency. Nearly all the selfsufficiency advocates are car dependent.This car dependency is the Achilles heelof the self-sufficiency movement. This isnot to deride all their useful projects,but in my experience the transport problemand the question of car dependency isalways given least priority and oftenignored completely.

Yet it is a fact that the motorvehicle is the single most wastefulconsumer item.

Six million cars are scrapped in theUSA alone, every year. How much acid rainand nuclear waste is spewed over theplanet in order to feed such obsceneconsumption ? For it is consumption that isat the heart of environmental crisis,nothing else. And the locomotive force,the prime mover in the economy which keepsconsumption rising, is ever increasingmotorisation of society - a force whichhas continued unabated in Westernindustrialised society since the end ofthe second world war - along with itsmultitude of by products. Highwayconstruction, freeways, motels, drive inshopping centres, multi-storey carparks,the urban sprawl ...The list goes on.

That is why an energy efficient house

24

with a car in its driveway (and more oftenthan not 2 cars!) is but an empty gesture.It avoids the heart of the environmentalproblem which is car dependency.

To me, using a bike for my everydaytransport needs (as opposed to leisurerides) is a form of political statement, astatement of my beliefs. (As well as beinggood fun of course!).

Development of the Ho Chi Minh was anextension of this statement. Low down weight.

This long bike has another attributeto its carrying capability - the weight iscarried low down, a very important factor.

In the next issue of Soft Technologywe will be featuring the constructiondetails of the Ho Chi Minh.

On a regular bike the load is carriedtoo high, causing more rocking and swaying- this requires constant compensatory bodymovements therefore more effort. 60 kilosof luggage can easily be carried on thisbike. (With stronger spoking in the rearwheel, even more. I have not yet testedits limits).

Incredibly, such weights actuallyfeel much less than they are. Friends evenclaim it is easier to ride partly loadedthan empty ! This is due to the weightbeing carried not only low down, but alsoin between the wheels. It stabilises andlowers the centre of gravity compensatingfor the riders high up weight, therebyimproving handling.

DrawbacksMost readers would by now be a little

cynical about the numerous claims I haveso far made for the Ho Chi Minh and to besure it does have just one short-comingover a regular bike. But only a minor one.Due to its length and larger turningcircle, wheeling it around in crowds whenwalking is a minor hassle. Otherwise thereare no drawbacks. All I can say is makeone for yourself and try it out.

Don't let the extra length of thebike put you off. It rides like a regularbike in city traffic. If anything the HoChi Minh is certainly a more comfortableride as the rider is no longer sitting sonear to the top of the bumpy back wheel.

The slight reduction in the turning circledue to its length is hardly noticed. On aregular bike I never perform sharp turnsanyway - its a bad habit in traffic. Myturning circle is always kept within thatof the Ho Chi Minh no matter which bike Iam riding.

TALK TO US !!Soft Technology relies on its readers forfresh exciting and interestinginformation. We are always on the lookoutto find out what you, the reader has beendoing and would like to hear about. Sotalk to us! Let us know about the fresh,exciting and interesting things that youare doing so we can let other people know.Don't worry about being able to write wehave trained experts who can decipher themost obscure scrawl.

Remember Soft Technology is a non-profitmagazine produced by unpaid volunteers. Tofunction it must have the support of itsreaders. So make the job of those hardworking souls who produce Soft Technologya little easier by sending something in.....anything....as long as it isn't

dirty or smells bad.

Talk to us!!

Building the BicycleWheelbarrow

In the last issue of Soft Technology we described a novel bicyclewheelbarrow named by its owner as the Ho-Chi-Minh. In this issue we show howyou can build this practical and flexible means of transport.

By Ian Grayson

You'll need- all the normal equipment from a ten-speed bike with preferably an alloychainset- 2 good old bike frames for weldingtogether. The rear frame must be a woman'sframe, the longest you can find, with acurved top tube of the old fashioned type.These old frames are easy to scavenge orfind in junk shops.- a long back brake cable and a longderrailleur cable. These are made fortandems and may need ordering but they areusually available.

- an extra chain and a idler wheel fortaking up the slack in the long chain. Aspare derrailleur jockey wheel will do,but a tandem idler wheel is better.

- if you can get it, a 2 l/2 foot lengthof oval tube for welding between the 2bottom bracket shells. If not, a piece ofold bike tubing will do, but it is thenadvisable to weld in steel plate gussetsat the joins, to compensate for the roundtubings lesser stiffness.- an extra length of old bike tubing, anold downtube will do.

- two extra sets of detachable seat stays,taken from old frames.Also, for the basket- 5 lengths of l/2 inch square tube each 2metres long. (The thinnest gauge you canfind).- one length of 5/8 square tube, 1 l/2metres long. (The l/2 inch-square tubemust be able to sleeve into it snugly whenthe ends are filed down).- 4 lengths of one inch square tube forthe baskets base each one metre long.- 2 pieces of 1 inch angle iron each 20 cmslong.

TOTAL COST OF THIS NEW STEEL IS ABOUT 15

DOLLARS

Also- some mesh for the basket sides.Difficult to buy. Cut up some old secondhand baskets from junk shops. (Using steelmesh gives many hitching points for loadsand allows long lengths to be tied to theoutside. In addition there is no airresistance.- some ply to cut to shape for the base.

Tools- basic metalworking tools including astrong bench vice and some clamps- hacksaw and blades- files- access to oxy-acetylene weldingequipment- a dozen nickel bronze welding rods.No jig is necessary but in order to clampthe frames together in a dead straightline a 4 foot length of angle iron isrequired or something similar, which isabsolutely rigid with no flex. I use veryheavy 3 inch angle.

NOTE ON WHEELS AND FORK RAKEA longer bike needs a softer fork

rake than a regular bike - about l/2 inchmore. A 28 inch front wheel and a 26 inchrear will help soften the rake. I preferthe 26 inch rear wheel anyway - its muchstronger for loads.

PRODUCTION STEPS FOR THE HO CHI MINHAny fully experienced backyard

tinkerer with basic welding skills canknock this extremely useful machinetogether in a couple of weeks.1. Select your 2 old bike framescarefully. Check for damage. Now...removethe seat stays from the front frame,2. Next, remove the forks and bearing cupsfrom the rear frame. Grab a hacksaw, and,holding the frame firmly in a vice, cutthe headstem vertically in half. (DrawingA).

Scrape, sand or file all old paint fromthe cut area down to the bare metal inpreparation for brazing. (Do likewise forall the subsequent welds).3. Clamp it with vice grips or a clamp tothe seat tube of the front frame, flushwith the bottom of the seat tube lug.(Drawing B).

*WARNING- Do not clamp too hard as thismay dent the tube preventing the seat tubefrom sliding up and down later. Clampwith seat tube inserted.

12

4. Before doing any brazing insert thewheels when the 2 frames are clampedtogether. See what you're aiming for.Check the fork rake - is it soft?Unfortunately, for reasons too long todiscuss here, certain frame combinationssit together awkwardly. The main problemis that the front riders bottom bracketcan end up rather high off the ground. Itsstill quite a feasible machine but itneeds the seat up higher to compensate forit, thus restricting it to larger riders,It also requires a very slight hop on andoff the pedals. Compare the pedal heightwith your regular bike. If you don't likeit then proceed no further - try anotherframe combination,5. Place the makeshift jig - the 4 feetpiece of stiff angle iron, diagonallyacross the 2 lightly clamped frames so ittouches the front frames downtube and bothframes seat tubes. Clamp it to all thesetubes. The 2 frames should now sit in astraight line. Insert front headstem andsight by eye along seat pillars andheadstem to check straightness. If all isOK then braze the join. (Drawing (C).)6. Clamp the front frames chain staysaround the down tube of rear frame and

weld. (If stays are long enough weld ontocurved top tube as well for extrastrength).7. Cut a length of preferably oval tube,for welding between the 2 bottom bracketshells.

8. Mitre it to shape, clamp in and weld.Leave cups in shells to prevent heatdistortion of the shells when welding.

Assembling the Ho Chi MinhAssemble everything exactly as a

regular 10-speed bike using a longerchain and the longer brake and gearcables. Bolt an idler or jockey wheel intothe rear bottom bracket shell and run thechain over it. The chain should now cleareverything - check it on all sprockets,especially the largest. If it touches themiddle seat stays that are now welded in,

13

don't be afraid to flatten the stay alittle - bike tubing is very strong.However this should not be necessary.

Test run the bike.If all is OK then cut a pair of the

extra seat stays to shape and weld theminto the rear triangle half way up theseat stem. Ensure chain clearance. Thismay be a tight fit. If necessary flattenthe offending stay to achieve clearance.

These extra stays are absolutelynecessary - the rear of the basket issupported by them. ENSURE THE SEAT STAYBRIDGE IS ALSO WELDED IN.

Test run the bike again.If all is OK then proceed to welding

on the basket while the bike is assembled.

Welding on the Basket (Drawing D)The 1 inch square tube can usually be

bent to shape cold, even to 90 degreesprovided the bend radius is soft.

FIRSTLY, Cut a 24 cm length of 5/8square tube. File the inside at both endsto enable the l/2 inch square tube to besleeved into it.

THEN Weld it onto the sliced topheadstem lug of the rear woman's frame inthe middle, (After removing the seat foreasy access).

NEXT A 1 l/2 metre length of l/2 inchsquare tube has to be sleeved into theattached 5/8 tube and bent into shape.

Bend it slowly and carefully in avice, little by little, constantlyreplacing it back in the sleeve foralignment and sighting by eye. The bendmust finish on the extra seat stays twoinches forward of the rear wheel axle.(Extending the base further than thispoint would result in whip and strain onthe back wheel).

IMPORTANT As shown in Drawing (D),this outer base edge of the basket sits oncross supports of one inch square tube.Clamp the first 2 in position prior tobending the edge, so you can see whatyou're aiming for. ENSURE THE CHAIN CLEARSTHE CROSS SUPPORTS - select your heightaccordingly. Weld nothing more yet. Ensurefoot clearance on pedal stroke.

If everything clears then weld in thefront cross support. (To strengthen itfurther, braze one of the 20cms longpieces of 1 inch angle iron across thecurved top tube first, then braze thecross support in it).

This cross support is now your heightguide, it should be as low as possiblewith chain clearance.

Now braze the outer bottom edge intothe sleeve and to the cross member.

The second cross member will need tosit on about an inch of upright tube as ashim, to obtain equal height with thefirst.

14 CONTINUED PAGE 33.

BICYCLE WHEELBARROW ..... CONTINUED FROM PAGE 14.

THE OVERALL OUTER WIDTH OF THE BASKETIS 48CMS - 24 each side. The lengthdepends on your frame. The height shouldbe flush with, or slightly above, the topof the rear seat tube.

The top of the basket can be curvedaround in a single piece at theappropriate-height as shown in Drawing(D).

Brace it for strength with uprightswhere you deem it necessary - obviouslythe corners are required.

To brace the rear, where the top ofthe basket straddles the rear wheel, twovertical supports welded up from the extra

seat stays are absolutely necessary. Theymay need staggering out, or bending alittle at the bottom to get the support.

To screen the top of the rear wheel,(not shown in the diagram), cut anotherpair of seat stays very short and boltthem into the seat pillar with the seatbolt. Weld the other ends to the rearinside end of the basket, flush with thetop, at a slight angle apart (notparallel). This also stiffens the baskettremendously, and doubles up as a kiddiesseat if a cushion is lashed over the top.Enclose the sides with mesh or rivetedplate, and weld short pieces of tube

STOP PRESS! - WITH HO CHI MINH BIKETo obtain maximum space in the basket

it is necessary to eliminate the intrudingseat pillar, and brace the rear wheeldifferently.

To do this cut the seat tube at theheight of the basket base.

Then bend a piece of thick walledsquare tube (I use 13/16 inch 1.6 mmwall). Bend it cold around an old style 28inch wheel. This would leave ampleclearance for your 26" wheel (if youdon't fully bend it).

Insert and weld in as shown inDiagram E.

It must be braced from the cut offseat pillar.

To screen the wheel I insert 2 morecurves of l/2" square tube from the reartop of the basket, about 1 1/2" from thesupporting curve each side (not shown indiagram). I then taper them in to Point Cand screen with tight mesh.

This modification takes 2 or 3 daysand it is best to assemble and constructthe machine first - then eliminate theintruding seat pillar.

With this modification maximumpossible space utilisation is obtained inthe basket.

Much is left out from this sketch forclarity. Points A, B, and C are points fromwhich cross braces of square tube can bebrazed for extra strength.

Right: Rolling along the Ho Chi Minh trail

across the gap at the top. (The dottedlines demonstrate the concept).

Also not shown in the diagram, apiece of 1/2 inch square tube has to bebrazed between the 2 points marked x,along the extra seat stays.

Welding in the mesh is very fiddly -here you are left to your own devices.

The plywood base is best cut bymaking a cardboard pattern first thentransferring it to the ply. Due to itsunusual shape it is best to cut and insertit in 2 halves.

The seat pillar protruding into thebasket can be a bit annoying sometimes butI have yet to find a load it interfereswith. Doubtless, a tooled up factory withall its resources could eliminate it bybracing the rear wheel direct to the rearof the basket. Although this is quitefeasible I am reluctant to interfere withthe rear triangle at this stage, as thatis the critical area for strength.

Finally, for those readers who arecurious about the connection between thebike and its name - well the Vietnameseleader who ousted the mighty American warmachine from Vietnam with peasanttechnology, Ho Chi Minh, used a similarapplication of the bicycle in hiscampaigns. In fact, although littlementioned in writings on the Vietnam war,extensive use of the bicycle technologywas the deciding factor in Americasdefeat.

American troups, although they hadmore logistic support in the jungles ofVietnam from their air force, stillcarried all their supplies and weapons ontheir backs.

The North Vietnamese adapted standardbicycles to haul huge amounts of suppliesthrough the dense foliage and narrowtracks - not ridden but pushed, with theloads bolted across the crossbars inwooden crates. Rods were attached to thehandlebars to assist pushing.

The Vietnamese supply lines stretchedhundreds of miles using vast numbers ofpeasants - "Peoples supply columns",pushing thousands of bicycles in this

manner. The manoeuvrability of the bicyclemade this possible in the dense jungle.

The Americans meanwhile, werecollapsing under their packs awaitinginaccurate supply drops.

Throughout the whole of theVietnamese war the Americans' obsessionwith high technology was so great thatthey never even considered the damage thatpedal power was causing them. They ignoredit and never considered its usethemselves. It was beneath them to evenacknowledge that simple bicycles, in thehands of a peasant army, posed a majorthreat to the world's largest militarypower.

Thus were they defeated.My long bike is named Ho Chi Minh

because it is an extension of the loadcarrying concept which the NorthVietnamese used. It was inspired by theconcept, and simply takes it one stepfurther by extending the bikes length andcarrying capacity.

34

BICYCLE TRAILERSTwo Wheel Designs

The versatility of the bicycle can Secondary things to consider arebe dramatically extended to the carr- - ability to squeeze throughiage of large and/or heavy loads with traffic (and doors)the use of a trailer. I've carried - capable of taking brakesquarter-tonne loads in my time (not - versatile loading spacerecommended for hilly, gravelly roads) - robustness in collisionsand recall instances of cyclists (posts, gutters)carrying couches, wardrobes, friends, - storage needs.soil, pot plants, small boats and

Dynamicssurfboards. Shopping is of coursetheir main use. A ridden bicycle forms a very

The main consideration in trailer unstable system that requires con-

design is stant correction from the rider.Whilst this becomes automatic- weightquickly, the addition of a trailer

- strengthgood cornering ability can be unnerving to the inexper-

-ienced. Unexpected harmonic motions

l good positive connection to thebike/trike.

can cause control difficulties whencarrying very long or unbalancedloads. Whipping and oversteeringmust be borne in mind when carrying

Page 19

other than small loads. Sometimesthe load will be much heavier thanthe rider so safety is a major factor.

resignTrailer design must be based on the

expected weight and the type of wheelsnecessary to support this load Bi-cycle wheels are very strong vertic-ally, since they act as prestressedcircular trusses. However, the largerthe wheel the poorer the ability toresist the side thrusts associatedwith swerving, cornering and manoev-ering along steeply (side) slopingroads. For this reason most trailersuse 20" X 1.75" as found on dragstersand BMX bicycles, (solid 10" and 12"

HEAVY DUTY TRAILER

have had some use but are poor shockabsorbers) although their lower inflat-ion and wide profile make them lessefficient rolling. They can staticallysupport 200kg easily but dynamic shockloads super-imposed on corneringloads limit the total to about 250-300kg/pair.Wheels can either be supported at

both ends, as on bicycles, or canti-levered, as on wheelchairs. The canti-levered construction gives a narrowerprofile but relies on heavier stubaxles and local reinforcement of thetrailer frame where it is attached.Most lightweight shopping trailers usewheelchair hubs, while the simple

supported wheels are generally foundon heavy duty trailers, wheelbarrowsand delivery trikes.The body frame is equally determined

by the necessity for strength and goodstability, The wheels need to beLocated so that the load space isdivided into two with a slightlyLarger forward section. This preventsthe trailer lifting the rider onsharp or unavoidable braking, as ittends to continue forward. Too muchforward loading will unload the steer-ing wheel of the bicycle. The framemust be capable of taking the loadwithout splaying (scrubbing-willresult).

The strut that connects to thebike must be rigid enough not to flexand hence transmit push-and-pullnotions to the bike, These strutsshould be straight as possible so thatthe least possible 'springing' occurs.Unless at large diameter (35-40mm) orheavy wall thickness, the use of asingle strut for heavy duty trailersis not recommended.Most trailers use 25-30mm diameter

mild draw steel tubing which is easyto work and weld/braze. It need be nomore than a millimetre thick. Alumin-ium is more difficult to repair, andwill need to be of larger diameter.The use of an open frame will increase

the flexibility for loads of awkwardshapes and make it easier to tie down.Solid baskets and walls will be aLiability in the wind (except for smalltrailers), whilst the open design isrelatively aerodynamic,HitchesLight weight trailers can use many

flexible materials to form the hitchas well as universal joints. Steelreinforced hydraulic hose is favouredin recent British models, whilesimple draw-bar type pivots and springsare used on USA children's trailers.Small rod ends from machinery, such asgo-carts, are light, reliable and ofsufficient strength.

Heavy trailers must have ball jointuniversal hitches due to high impulseloads and tension. The rod ends from automobile steering systems are good(and cheap). To prevent the bikeframe (and rider) being twisted onoverturning a laden trailer, it is goodpractise to enable the joint to rotateunder high stresses.

It is commonly attached to the seatpost with a clamp similar in action tothat of the normal seat clamp. Somefit onto the seat clamp. Low axlefittings have also been used, but thisarrangement tends to limit steering toone side and introduces uneven loadings.On sharp turns it can push the rearwheel into a skid. Higher pitch pointsenable the rider to lean further intoa curve to counterbalance the trailer'soutward-bound momentum. Additionally,the pivot should be as close to thecentre-of-turning gravity of thebicycle, so that the turning momentabout the hitch is low. Hitches fittedbeyond the wheel accentuate the "sep-arateness" of the trailer, increasingcontrol difficulties.

Page 21

BrakesHeavy duty trailers can adopt either

standard rim caliper brakes, or inter-nal expanding hub brakes. Caliperbrakes are cheap and easy to fit on abridge. The cable can replace thestandard rear brake cable on the handle-bar lever. Back pedal hub brakes willneed modification to enable the controlcable to turn the cog backwards. Itwill require more cable travel, so aseparate long handbrake lever fittedinto the bicycle frame is necessary.These brakes are robust and usuallyhave stronger axles. Both types willneed some balance gear and adjustmentscrews. Small drum brakes, though verygood, are usually too expensive forcommon use.

The writer Wayne Kotzur actuallymakes and sells bike trailers. Theheavy duty trailer (250kg max.) is$250 while the shopping trailer is$150 with a 1" square plastic coatedtrailer. For more information writeto Wayne Kotzur at Inner City Cycles,31 Glebe Point Rd., Glebe, 2037.

Page 22

Four Wheel DesignsWhen you're carrying very heavy or

very bulky objects (fridges, ward-robes, pianos, etc) a 4 wheeledbicycle trailer can be a big advantage.They are much more stable and exertmuch less pressure on the towbar whencarrying these types of load than 2wheeled trailers. They avoid balanceproblems due to poor load placement,sudden braking, etc. (as discussedin the article on 2 wheeled trailerdesign). However, 2 wheeled trailersare more suitable than 4 wheeledtrailers for lighter and smallerloads, because they're more manoeuvr-able, fit through narrower gaps intraffic, and are smaller and lighter50 are a bit easier to tow.Because the weight is spread over 4

wheels instead of 2, the maximum loada 4 wheeled trailer can carry isroughly twice that of a 2 wheeledtrailer. This gives a maximum loadingof 500-600 kg. This is not allowingfor other factors such as steep hills,bumpy roads, lack of low enough gearson the bike, strong headwinds, fitnessor otherwise of the rider, etc. Inpractice the limitations to maximumLoadings are these other factors,Watch out for bumps or potholes in

the road - a heavy load that can beeasily supported on a smooth road willrapidly destroy wheels that quicklytravel over very rough sections ofroad. Steer around them, or if you

trailers (except for balance as alreadymentioned) I won't go into much detailhere, except to point out a few ideasbased on my experience with my owntrailer. I have found the drawbar(the connecting strut between trailerand bike) made of 3/4" steel waterpipeis strong enough for the job. Water-pipe is labelled by its inside dia-meter - its outside diameter is 2.7cm(l-1/16") and wall thickness is 3mm(7/64"). You may find, like me, thatyou don't need brakes on your trailer,When the trailer is lightly loaded, Ican stop from high speed quicklyenough with just the brakes on thebicycle. When the trailer is veryheavily loaded, I find I'm able totravel at only 15 k.p.h. or so, slowenough to stop safely just with thebike's brakes. The load regulatesthe speed! Anyway, it could be anidea to try your trailer without brakesbefore going to the extra work andexpense of putting them on.

My trailer heavily loaded seems tohead into a corner better than aheavily loaded 2 wheeled trailer. Ithink this is because the dynamicsare different because it is articulated- it 'steers' into a corner like acar, reducing the tendency for thetrailer and load to keep going straight.Maybe this is why I don't have controldifficulties even though my towbar ismounted on the back of the rear rackon my bike - in theory an undesirableposition (see the discussion in the2 wheeled trailer article on thecentre-of-turning and the desirabilityof mounting the towbar/pivot pointfurther forward).

can't, slow right down to a slowwalking pace. Collapsed wheels aren'tmuch fun.Because the design considerations

talked about in the 2 wheeled trailerarticle apply equally to 4 wheeled

Page 23

The drawings of the trailer shouldgive you a fairly clear idea of howI built it. Modify the materialsaccording to what you have or can getcheapest or free. Substitute materialsonly of equal or greater strength tothose listed. I used round steel tubecut from discarded school desks forthe frame, The pieces I then oxy-welded together. I rescued an oldwheelchair from the tip, and dismantledthe wheels to obtain the hubs. I tookthe hubs to a bike shop and had thefront wheels built. The wheels werethe biggest expense - about $90 for the4 of them. Since I had the other bitsand pieces of steel already lyingaround in the yard at home, the onlyother expense was about $15 worth ofwelding gas. So for about $105 I hadthe whole thing together.

For more details, please contactTony Murphy, at the AlternativeTechnology Association, 366 Smith St.,Collingwood, Vic. 3066, ph: 419 0250or 419 8700.

The Alternative Technology Associationis organizing an information night onbicycle trailers in August or September- watch your newsletters for a date.We'd like to get a few people to bringtheir own trailers to show everyone andgenerally pass a few ideas around.

So if you're interested in this pleasecontact the Alternative Technology Ass-ociation on 419 0250 or 419 8700.

Page 24

Hole A is slipped over tapered bolt B, pin can be easily compressed by fingerthen split pin C is inserted through pressure to fit through hole, and onhole D. Split pin holds trailer coup- releasing pressure after insertion,ling on towbar, and provides easy 'no springs back to position as on drawing,tools' quick release of trailer, Split and can be reused many times.

The Law and Bicycle TrailersI have been stopped by police sever-

al times - their immediate reactionis: "What you've got there is illegal!"So I was inspired to check on the law.In Victoria (I assume it's the samein other states though it would beworth checking) there is no law relat-.ing to trailers towed behind bicycles.This puts the responsibility for gooddesign and construction on the indiv-idual builder. Providing peopletake this seriously, and don't buildtrailers that are unsafe and causeaccidents, there never needs to be alaw about bike trailers. A good wayfor it to stay:

This is all very clear when we'retalking about carrying luggage,shopping, non-human passengers, etc.But when we start talking aboutcarrying human passengers on trailerstowed behind bicycles, things getmore complicated. There is still nospecific law on this, but a bicycleis considered to be a 'vehicle' inrelation to road traffic law, andgenerally laws that apply to cars(having lights at night, stayingbelow speed limits, etc) also applyto bicycles. There is a law prohib-

iting human passengers from beingcarried in a caravan or-trailer towedbehind a car. 'This is for safetyreasons - the caravan might comeloose from the car, caravans are veryfragile and don't offer the sameprotection from injury as a carduring a smash, they don't haveseatbelts, etc. But there is alsoa law allowing human passengers tobe carried on bicycles providing theyare properly designed and built forthe purpose, or have been modified bythe addition of a properly designedand built seat (e.g. a baby carryingseat).When is a device towed behind a

bicycle only a trailer, and when is ita properly designed and built vehiclefor the transport of human passengers?When is it legal and when is it illegal?Of course there is no answer, andthere won't be a definitive legalanswer unless someone has the mis-fortune to be brought before a court(perhaps if passengers on a 'trailer'were killed or injured, and it wasalleged such a 'trailer' was illegaland a contributing cause of theaccident), I would argue that the

Paqe 25

Southern Australia has not been reportedCertainly, the horizontal rockbed rep-resents a novel technique not yettried fro greenhouses. Operating experience and results from both the"active" rockbed adn the "passive"water barrel systems will enable con-clustions to be dreawn as to the suitab-ility of this type of greenhouse to our climate.

safety concerns about car caravansdon't apply to bicycle trailers becausetravelling on bicycles involves beingout in the open unprotected anyway,whether you're on the bicycle or thetrailer,Don't get the idea I'm trying to

discourage passengers from travellingon bike trailers - I carry friends onmy own trailer. I am encouragingpeople to be safety conscious. Toprovide for the comfort and safety ofyour passengers, as well as puttingyourself in a good position if thelegality of your trailer should bequestioned, I suggest the minimum youneed is a seat and some footrestarrangement to prevent people's feetdangling on the road. The seat couldbe just an old kitchen chair with thelegs cut off attached to the trailerframe, and the footrest could be apiece of board, both easily detachablewhen the trailer is used for otherpurposes. For young kids a boxed in

Solar GreenhousesContinued...

5.0 Conclusion

This type of greenhouse is not new.Its ancestry goes back to the CanadianBrace Research Institute which builtsuch a structure in 1973. However, tothe author's knowledge the existence ofperformance of such a greenhouse in

compartment with fairly high sides isbest. Seating can then be attachedinside. It helps to have some part-icular physical characteristic topoint to as satisfying the 'properlydesigned and built' requirement.--

Make sure the linkage between thetrailer and bike is very strong. Ifyou've just built a trailer, test itcarrying things around for awhile beforecarrying people. For after dark use,have reflectors and lights attached tothe trailer. For daytime use, considerpainting the trailer a light colour,or having passengers wear bright col-oured clothes or a bike vest, Bicyclehelmets for passengers are a goodidea too, Anyway don't let all thistalk of laws and accidents get youdepressed, bike trailers are fun, it'slike being a kid playing around inbillycarts again!

TONY MURPHY

Page 26