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sydney alternative media - non-profit community independent trustworthy
Thursday, 19 July 2007
Build a bicycle trailer with no welding - cost $20
Mood:  a-ok
Topic: local news


We are going to burn alot less petrol and alot more fat with this home made and designed bicycle trailer. It only cost about $20 because we were lucky to find and scavenge alot of the materials and buy the balance from The Bower at 142 Addison Rd Centre. We blame the ABC inventors show and necessity for this invention.

 From top left clockwise the picture reveals

1. Not as great a design as the Hills Hoist but we are still quite proud;

2. The swivel mechanism - a chunky bit of wood (the swivel beam) with 2 holes (via power drill using skinny drill bit in a circle, and chisel out): A hole at one end for bike seat pole and another hole for the swivel over the back wheel (a 2nd fork cannabalised from one of the trailer frames). Notice the hole in the wooden cross beam (main trailer cross beam) on the trailer at top left of the image which will fit onto the swivel. Take care to measure the length of the swivel beam, seat to swivel (say 30 cm roughly), such that when the main trailer cross beam fits onto the swivel the metal axle pole of the trailer (fed through the two absent bottom brackets) has decent clearance from the rear wheel of the bike.  This swivel beam is essential to prevent trailer running into the back of the bike on down hill momentum (we first tested a bit of climbing rope fine going flat or up but as you would expect no good slowing down or down hill). The swivel fork over the rear bike wheel is essential for attachment - trailer to rear wheel to back seat - but also to keep the trailer 'up' over the rear wheel, and thirdly to allow cornering. It also allows a straight line of load force from trailer to bike  

(See below for the attachment of the lower fork ends of the swivel to the rear axle of the bike rear frame. Another (commercial) method of trailer yoke design is arms of a trailer direct to the rear axle of the bike good for avoiding bounce, but that's another story and may require welding ability and a wider rear bike wheel axle. Our design does not anticipate bounce with a fairly heavy lower shelf, bottom bracket axle, and swivel to stabilise travel vibration.)

3. One of the two 20 cm bolt assemblies through one of two front trailer frames (two cannabalised and stripped old bike frames front wheel removed) fed to metal plate at bottom end of what used to be hole for front forks, fixing chunky wooden cross beam at front of the trailer - big enough for hole to be drilled in middle for the swivel pole. The wooden cross beam is the trailer attachment to the swivel on the bike but also supports the top storage shelf of the trailer.

4. Right trailer wheel (facing forward on bike) inner attachment to wooden cross beam. We only had a skinny front bike wheel to recycle which is skinnier than a stripped regular rear wheel. As a result we ended up using a little U bolt to ensure wheel travel clearance onto a 2nd bigger U bolt onto the hard wood cross beam.

5. The attachment of the lower fork of the swivel to the rear bike wheel frame - if the bike has unusually wide rear axle then maybe just fit as a second set of forks, but more likely you will have to marry the Allen key bolt holes of the respective forks (originally designed to mount panier racks). It's alot easier if you reverse the swivel fork as if facing backwards to make room to line the holes up and screw the Allen bolts in.

6. metal pole cross beam fed through the two absent bottom brackets of the bike frames. Note at right the U bolt onto some 9 mm ply shelving. Notice this pole axle is fixed with some bashing with a hammer to slightly flatten the circumference of the pole each side of the bike frame.

7. rear safety attachment of bread basket shelving (light bright strong and weather proof) with some unused climbing carabiners.

8. left hand wheel of trailer with U bold attachment, notice this wheel is a back wheel stripped of its cogs (for lightness) and provides much better clearance for attachment of wooden cross beam.

9. rear shelving fixed by safety bolt.

10. top shelf fixed by safety bolt to swivel fork with metal plate and recylced handlebar nut off stripped frame.

12. under carriage showing wooden rear cross beam, bottom bracket axle, lower shelving bolts

13. Not shown - trailer rear wooden cross beam for upper shelf attached with u bolts through drill holes.

Note - care should be taken to provide all nuts with either a split washer or plastic insert in the nut to hold the nut fast from vibrations. We found many of these from an old metal couch in a local lane.

The above still needs some road testing and probably a flag in the trailer empty seat holes and reflectors on the rear especially at night to aid visibility on the road. Riding is likely to be mainly low gears. Design weight on the trailer we expect to be around 50 to 100 kg.

Posted by editor at 4:13 PM NZT
Updated: Friday, 20 July 2007 2:28 PM NZT

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