Instructables
Picture of biga, the bike trailer
biga28b-pixlr.jpg

In support of a bicycle workshop I have decided with my friends to build a trailer to carry the tools around the city.

We were not skilled in welding iron frames, but that didn't stop us, and with some advice we succeeded in building a nice, strong, and effective trailer, which remembers me an ancient Roman "biga".

[first two pictures are created with pixlr express]

Step 1: The pieces

Picture of The pieces
biga02.jpg
biga16.jpg

We started to cut an old and cheap mountain bike frame, so that we had different measures tubes. As wheels I found a pair of children bike forks, so to have an easy wheel connection and to use 20" wheels, not big as 26" but not as tiny as a cart. The green tube comes from another old bike frame, it has an elliptical section, and it matches very well with forks' heads.

Step 2: The project

Picture of The project
biga05.jpg
biga04.jpg

As you see the project is quite simple. The forks are horizontal and connected by two little pipes. All this acts as a surface plane, where we will link the toolbox. The main problem in a frame like this is to avoid big leverages on the weld joints, and I planned to stiffen the structure with diagonal pipes for both longitudinal and cross direction. In this way the weak part is the middle section of the vertical pipe, but it proved to be strong enough.

 
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Hi Andrea, really like the project, I have built several bike trailers in the past and this one is great! I'm currently building a petrol trike and I'm also learning to weld while doing so, can you please explain in greater detail the size and thickness of the electrodes, I'm debating whether to use larger or smaller diameter ones. Anyway, thanks and love the build!
VentureScout2 months ago

good job, voted!

andrea biffi (author)  VentureScout2 months ago

thanks man!

Great Structalbe!Congrats on being a finalist!

andrea biffi (author)  ContraptionMaker3 months ago

Thanks! :-)

Very detaled.

Edgar4 months ago

Ave, Roma! :) A great Instructable, and this might serve also to tow a second Bicycle, to pick up someone...

Voted, and went to my Blog:

http://faz-voce-mesmo.blogspot.pt/2014/06/biga-e-imprimir-em-3d-uma-stranbeest.html

andrea biffi (author)  Edgar4 months ago
thanks Edgar! Glad to appear again on your blog :-)
:)
thumbsup.png
Bibilas4 months ago

Great Instructable. Thank you.

andrea biffi (author)  Bibilas4 months ago

:^)

I rather suspect that when loaded this trailer will be too nose-heavy, with likely severe consequences for handling of the bicycle-trailer combination, particularly when cornering or cornering and braking. When combined with the high-hitch, a bicycle with rear suspension could have its suspension overloaded.

It is notable that commercially designed and made bicycle trailers (and probably all commercially designed trailers for cars too) have a load platform with the axles, positioned slightly behind the centre of the load platform.

http://www.oxtailbicycletrailers.com/basic_principles.html

andrea biffi (author)  totally_screwed4 months ago

I don't understand what you mean... if the wheels axis is positioned "slightly behind the centre of the load platform" the nose will be very heavy, but in my trailer the load center of gravity is very near to the center of wheels, so the nose is not heavy at all. The trailer has been already used for many kilometers, it behaves marvelously in cornering and breaking.

Anyway we are planning to extend the loading platform toward the rear area between the wheels, in that way the load will be even more centered.

I'm sorry but your reply makes no sense and is self contradictory. If what you say is true "but in my trailer the load center of gravity is very near to the center of wheels, so the nose is not heavy at all.", why would you state: "we are planning to extend the loading platform toward the rear area between the wheels"?

That only makes sense if what I said were true. If the trailer worked as claimed (when loaded) why would you modify it, except to increase its capacity? *

Extending the load platform rearwards makes it much more like tried and tested commercial designs, which was exactly the point I was trying and clearly failing to convey.

*A rearward extension on an already well configured trailer is a recipe for tail-heaviness, which is even more dangerous than nose heaviness because it can unweight the rear wheel of the towing bicycle (especially during braking, turning and conditions encouraging low adhesion), causing loss of grip and jack-knifing.

andrea biffi (author)  totally_screwed4 months ago

We are planning to extend the loading platform toward the rear area between the wheels exactly to increase the trailer capacity, not much in load weight but especially to use that small area to keep a low storage box, which will still leave space for the toolbox to open.

You are right about the tail heaviness, but here we are speaking about only a few kilos.

I think that your trailer and mine are quite similar in terms of load and weight positions... in both trailers the centre of gravity is slightly in front of the axle, which I think as you that is the best configuration.

i still don't see the problem with this. for the problem to arise the load would have to be substantial, the trailer looks to be a little over 2 feet wide and just under that in length ( the area for storage). maybe i'm not understanding him. i don't see you hauling over 150-200 Lbs. so i don't see any danger, the bike parts you used "usually" can handle that much. anyway i like your simple and effective trailer. if i didn't live in suck a hilly area I'd use my bike more. and this would help greatly for store runs. totally if you can draw something and explain what your saying I'd appreciate it, this is a great place to learn and share.
andrea biffi (author)  andrea biffi4 months ago

Ouch! Sorry, I misunderstood the "slightly" adverb ;-)

yes, although you can see from your link (top banner image) that there are trailers with wheels very far behind the load center of gravity (the nose will be very heavy in that configuration), my trailer has the wheels axis slightly behind the centre of the load platform, and so it works very well.

andrea biffi (author)  andrea biffi4 months ago

Ouch! Sorry, I misunderstood the "slightly" adverb ;-)

yes, although you can see from your link (top banner image) that there are trailers with wheels very far behind the load center of gravity (the nose will be very heavy in that configuration), my trailer has the wheels axis slightly behind the centre of the load platform, and so it works very well.

i believe he has addressed this load platform issue the center of the wheels are behind the load platform.

You appear to have misunderstood my previous post. You have reversed what I said. Trailers generally need to have the centre of the load platform slightly in-front of the axles. They also need to be carefully loaded so the centre of gravity is as low as possible and lies on or very close to the centre of the load platform.

This is most important and my experience of towing with different bicycles, different trailers, combined with high and low hitches confirms that as built this trailer has what I believe to be a serious and potentially dangerous design flaw. Especially so, when carrying a heavy load, such as a toolbox full of tools.

Potential users - you have been notified.

A commercial bicycle trailer (I have the large version of this)

http://www.carryfreedom.com/wp-content/uploads/201...

lifeinbeats4 months ago
Love this. It's quite the endeavor but if I'm ever in need of a trailer and find myself in possession of a welder I'm doin it! Think it could go longer without much problem?
jslarve4 months ago

Looks very beautiful.

shazni4 months ago

Super instructable!

andrea biffi (author)  shazni4 months ago

thanks Shazni, I love your ibles!

Junophor4 months ago

Hi andrea biffi

Once again I am deeply impressed about this latest idea.

Five stars worth ;-))))

Yours Aeon Junophor

andrea biffi (author)  Junophor4 months ago

thanks my friend!

trans4mation4 months ago

This is a very wheel thought out design! See what I did there? Anyway, well done instructable, this looks like it coukld be very useful.

andrea biffi (author)  trans4mation4 months ago

LOL, indeed I also joined the Wheel contest, it probably is still under approval.

Thanks!

confu4 months ago

Awesome! In particular the design of the hitch.

andrea biffi (author)  confu4 months ago

yeah I'm quite proud of the hitch design but I have to give some credit to my friend Dado for that

i have a friend who is an avid biker so im gonna show him this. weel done!

andrea biffi (author)  some random dude4 months ago

that would be great! let me know what he says!

Tazmjm694 months ago
For not being welders, this really turned out great! Very cool idea!
andrea biffi (author)  Tazmjm694 months ago

thanks! :)