Tuesday, 1 October 2013

DIY Longtail Cargo Bike - Chapter 3

DIY Long tail Cargo Bike - Intro


Having finally sorted out the geometry to the best of my ability. There are the following things to do.

  1. Strengthen Rear Rack
  2. Build Lower foot rests.
  3. Check over welds
  4. Sand down knobbly welds.
  5. Paint
  6. Assemble
Catch up on Chapter 1 or Chapter 2

DIY Long tail Cargo Bike - The last of the welding.


So strengthen rear rack, after all it will be carrying a fair bit of weight. You can see in the below picture that I have added some builders fixing strap 90 degrees to main bars. This was a pointless addition and it would have been better to have created one high quality join half way along the span.


After adding the fixing strap the outer bars were still pretty bendy so I added in some thin tubing for support (below), I also added the same gauge tubing at the rear coming up from the seat stays (as was). All of the thin tubing was from stuff lying around, most of it coming from a kids play pen, probably some type of mild steel.

Finished Length

1.63.m - Front Drop-out to rear drop out.

2.25m - Overall length with tires.


DIY Long tail Cargo Bike - Paint Job


I let my daughter choose the colour for the paint, and she went for Howard Rotovator Orange (by Temac) which we bought from Mole Valley Farmers. I didn't bother with a primer, and painted over the top of any existing paint. It took two generous coats equating to around 1/4 of a 1 litre tin.


DIY Long tail Cargo Bike - Rear Decking


The last thing to "build" is the rear decking for the top deck I used a bit of 1/2" marine / exterior ply wood. I figure I may attach things to this like grab handles and seats etc. so I wanted it to be fairly sturdy. This was secured with a combination of M6 bolts and (my favourite) builders fixing strap.


The lower deck was a thinner 1/4" ply, and this was secured use fairly large zip ties.






DIY Long tail Cargo Bike - Assemble


So now for the fun bit putting the bits together.


Forks for your long tail cargo bike.


The forks are  thorn carbon fibre forks with a very long steerer tube. These are completely the wrong forks to use, as thorn specifically say they are not suitable for off road or tandems. Still that is what I had spare.

An ideal fork would be a thorn mt tura fork, which are strong and made of steel, and have attachments for everything except disk brakes, for that reason you may wish to opt for surly disc trucker forks, which offer nearly the same length steerer.

Suspension forks with disc brake mounts may also be a good choice.


Wheels for your long tail cargo bike.


I would not go below 36 spoke for wheels, but then a lot depends on the quality of the rim too. In my spares pile I had a Shimano DH-3N20 paired with a Sun RhynoLite XL. This is an ideal front wheel for a cargo bike as it will provide reliable power for lighting, and the rim is bomb proof.




The spares pile did not yield a particularly good rear wheel for the long tail cargo bike. A grunert   something or other, laced to an old shimano 9 speed hub.


Gearing for your long tail cargo bike.


The biggest problem is obviously the distance from the rear hub to the chain set. The distance for this bike is roughly double of the that on a normal bike, I had to join 2 chain together. As you can see from the above picture I am running in single speed for the maiden voyage! This keeps very good chain tension obviously, but previous attempts using a powerful chain tensioner (gusset I thing) were not successful with lots of chain flip / flap/ flop.

So if you have horizontal drop outs a hub gear might be ideal here, but I will have to stick with derailleur or single speed for the time being, as I am low on funds.

I will be opting for a 1x9 set up, as I can't stand rubbing noises from front mechs, so I will limited to a gear range of around 300% provided by a 11 - 34 cassette

The 33 tooth M - igthy chain set was very cheap from SJS cycles, but you will need a fairly long bottom bracket axle in order to allow clearance, the chain ring was rubbing the frame on my maiden voyage, so I will have to make some adjustments there.

Tires for long tail cargo bike.


world is your oyster here, I went for cheapest schwalbe tires on ebay at time which are speed cruiser just make sure they are good a grippy. A side effect of having a very long bike is that when you are riding solo the weight to set very far forward, pedal hard on a slightly slippy surface (that would be fine on a normal bike) and the rear wheel will spin.

Please concentrate on the tire in the picture below and overlook the jaunty angle of the framing! The pitfalls of frame build without any kind of jig I presume.



Brakes for Your Long tail Cargo Bike


So in an ideal world it would be sturmy archer drum brakes all round, they are lovely. But as it was the spares heap gave me v brakes, so on they went.


Just as well it was v-brakes, as I don't think a standard brake cable would reach down to a disc or hub brake. As you can see from the above picture the uncut cable was just long enough.


More pictures of nearly finished long tail cargo bike.



 Read on in  Chapter 4?

Sequential Test for Planning

Flood Risk

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