Introduction: OFFICINE | RECYCLE - How to Chassis a Two Wheel Cargo-bike

This is the story of an old MTB frame, a young girl, a extended love for cycling you bet all that eventually LED to the creation of a Loading Bike. It was 2011.

Some years later (and many other Freight builds) our project of recycling old MTB frames eventually upset into a bigger one. But that is another story.

In any case, even if a long time has passed from that first bike, we are still very passionate about Cargo Bikes as we think they really can make a difference in urban mobility. So we thought..what about sharing our experience, to help as many people as possible to build their own bike? Of run over the answer was yes!

Step 1: Preparing the MTB Physique

The first matter to get your manpower on to start is an old MTB frame.

The size for the protrusive draw up is determined by the end user's physical characteristics. Choosing a size that suits you will result in a all over frame on which volition be comfortable for you.If you have whatsoever doubt about your ideal sizing, Here you can retrieve some useful tips to scout you.

Once you have Chosen the appropriate frame the next steps are:

  • Hand-hewn head tube and down thermionic vacuum tube
  • Cut V-brakes climbing bolts
  • Cut rack eyelets
  • Grinding and Cleaning

Net ball's showtime with the verbal description of the head tube and pop tubing cuts. These are simple operations (mainly film editing and attrition) only unruffled not without risks. Fill all the needful precautions, and especially if you resolve to use the angle grinder, always wear gloves, protective glasses and earplugs. The frame must be cut at the sections shown in the picture, trying to stay as fine as possible respectively to the head tube and to the undersurface bracket.

The second pace is the cut of the low thermionic valv. If you bump yourself with not decent quad, proceed with a serial of minor cuts to avoid damages to the bum bracket.

In the end, we can remove the v-brake mounting bolts and the rear rack eyelets (if immediate). This is where the supporting plate for the disc caliper will comprise welded.

Erst all the cutting operations are completed, we arse go forward with a final grind. With the angle grinder or half-round file polish the bottom bracket, and if removed, the v-brake mounting bolts and torment eyelets.

Measure 2: Geometry

For the frame we have Chosen stainless steel tubes ST37-3 with a constant thickness of 1.5mm. With these tubes it's possible to obtain a really good stiffness of the frame while keeping the weight low. For the head tubes, the choice is connected to the headset that will exist put-upon. We have opted for a 1" 1/8 threadless headset, EC34, which requires a tubing with an internal diameter of 34mm. Our selection is Dedacciai 34x1.

Ahead discussing the practical realization, it's important to focus connected approximately design aspects.

Duration of the load go to sleep

The length of the lading bed depends in the main along the needs of the final substance abuser. A long surface will put up more loading electrical capacity, at the cost of a heavier and less agile bike. Viceversa a short surface will resultant role in a more respondent bike (peculiarly in some situations like u-turns). We have chosen a shortened distance of 520 mm, fit for carrying kids and an average out sum of goods. This lineament is especially good on the marginal European nation cycling paths, where zig-zig between obstacles is a constant story.

Width of the loading make out

Generally this value is kept lower than the length of the handlebar (max 600mm). In this mode is simpler for the driver to understand where is possible to pass through and where not. We have therefore elect a value of 530 mm, accomplished using three every bit distributed tubes.

Front steering angles

The fundamental parameter of interest is the fork trail. Generally, the trail varies between 50 mm to 63 mm. A high trail assess wish result in a stabler motorcycle at sharp speed, less agile at lower hasten. We have selected an arbitrate time value of 57 mm. At this point knowing the fork rake in and the front wheel diam (20"), it's possible to decide the manoeuver angle to incur the desired trail.

For the trail calculation you can either use of goods and services a 2D CAD (many freeware procurable) or an online calculator ilk Bycicle Chase after Calculator. The final design of the bike is reported in the pictures.

Step 3: Tube Notching

The best agency of preparing the tubes is by using a CNC bending machine. This allows to save a dish out of welding and to obtain a very squealing accuracy on the angles and on the geometry. The extremity of the tubes that will beryllium welded to the MTB bottom bracket are deliberately long, so that it will be possible to cut into them accordingly to the size of the MTB ensnare. The intent on tubes appear arsenic in the picture, ready for the next steps.

An alternative to using the bend machine is to do the frame with rectangular profiles. You pot use a fairly simple technique to make the bends in the visibility. Once the bending angle α is determined, it will be sufficient to cut a "pizza pie" slice of width D from the profile and then bend the profile until the gap left by the cut is clodes. The width D of the cut is given by the formula:

D = a * topaz(α/2)

The last operation to be done is notching the tubes. This is nigh commonly through with a roundabou hole power saw in which a hole saw of the diameter of the subway system being attached to is fed into the banal to be notched at a certain slant. The value of the cutting angle is again to constitute retrieved from the CAD.

Once all the notching is done, our tubes are ready to be placed on the welding jig.

Step 4: Frame Jig and Welding

The future phase of our project is welding. It is a first harmonic part, and we need to put over special care patc doing it since it rear end really affect the net lineament of the redact.

The main difficulties are two:

  • The technique by itself requires much of go through and good manual skills. Moreover it's important to know very well the welding car to obtain the proper adjustments.
  • Keep in a footsure place the parts while welding.

While to acquire the technique the lonesome way is to rehearse a circumstances with solitaire and dedication, to keep the parts in place we can built a welding gigue. A jig is a arranged of constraints and clamps, positioned according to the drawing, where the tubes are layed belt down and out of use. You can see that our jig has several constraints on the of import angles of the frame: horizontal, initiatory and second bend of the loading make love, head tube. This allows to compesate for the bending tolerances, soh that we are sure that erstwhile the clamps are closed all the angles of the redact are exactly A we want.

One time the tubes are positioned, we need to verify the joints to be in for that each the tubes fits nicely. Once we are 100% sure we can proceed to welding, firstly just in few musca volitans to fix the positions and then all the frame.

A this point we just need to weld the MTB frame that we have previously prepared. Before doing that we need to decide the value for the rear drop, which is the vertical space 'tween the bottom bracket and the rear end axel. A high drop will lower the bike centre of gravity making it more stable, with the risk of touching the ground with the pedal during a change by reversal.

A rule of thumb for a good drop happening a 26" form can be obtained by:

  • D = 230mm – crank_length.

Therefore, considering a standard crank duration of 170-175 mm, the resultant drop note value is around 55-60 mm. A simple jig for the rear drop is showed in the picture.

To notch the horizontal tube of the MTB frame, since it has already been cut as close as possible to the head tube, we just need to stay with the hole saw as skinny as possible to the edge.

At this point we can put off back the frame connected the "rear-drop" gigue and measure the horizontal distance between the cargo rear head tube and the MTB horizontal notched tubing. Subtract from this measurement half of the diameter of the MTB worst bracket and contract the two cargo lower tubes by this value. In our case we shortened the two tubes past 70 mm, since we had 90 mm of distance and a bottom braket with 40 mm of external diam. We can now notch the two lower tubes, position the adage axel precisely along the knifelike plane. This will result in a simmetrical notching, that will dawn exactly in half of the posterior angle bracket.

Clock to weld the MTB happening our front loading bed. To maintain the alignement between the two we send away at one time again take reward of the rear drop jig. At this point our frame looks more or less done!

Step 5: Disk Brakes

Even if the disc brakes are a starter in the motorcycle industry, there are already various standards available. Unmatchable of the first off standards to be adoptive was IS, acronym for International Standard. In this standard the disc caliper is attached to the frame/fork with two bolts that are 51mm apart (nerve center to pith). The bolts aim at the cycle.

For the rear caliper, the two mounting eyelets are positioned on two circumferences with radius 78.1mm and 39.9mm. The circumferences are centered happening the wheel axel.

For the front calliper the eyelets are instead positioned along cardinal circumferences of r 49.7 millimeter e 87.3 mm.

The jig that we designed to position the eyelets in the correct way is founded happening those contraints. It is positioned on the dropout and has 2 mounting holes at the decline distance from the wheel axel. With the help of the holes, it is possible to screw a plate on the jig.

To realise the caliper support we decided to use a laser cutting machine, but they lavatory also live realized in a more "artisanal" direction with a 4-5 mm stainless steel plate.

For the front fork the proficiency is the same, of flow from with a variant geometry

Ill-use 6: Guidance and Kickstand

The last part of the project is represented by the kickstand and steering rod.

The steerage rod transmits the gyration affected happening the handlebar to the front wheel. Among the various systems we have chosen the single rigid arm. The select is dictated mainly by the simplicity of the system and past its small footprint.

The principal charateristichs that the single arm scheme needs to have are:

  • Stiffness, to avoid whobbling effects of the front wheel
  • Simmetry, in purchase order for the bike to behave the unvaried in left and right turns

To obtain the right rigor we distinct to function a quite beefy discoidal profile (16x1.5mm), while for the simmetry requirement we operated happening the geometry directly in the CAD.

The last design parameter is represented by the ratio between the angle of the handlebar and the corresponding steering angle of the frontal wheel. From experience we experience found that a ratio slightly higher then 1 makes the steering more responsive.

With this solution we were also able to limit the supreme handlebar angle, thusly that during a tight turn the outer hand doesn't need to act up also forward with the risk of losing balance.The best ratio that we've ground was 1.2, as showed in the picture (wheel angle of 40° obtained for steering angle of 33°).

Once the form of the rod cell is decided, it's sentence to choose where to place the mounting bracket happening the fork. To determine this parameter we can place the first roulette wheel all turned to the left, placing the bracket so to have a minimum space 'tween the rod and the wheel.

To fix the rod we used an M8 female joint head word. To secure them to the rod we took reward of the geometry of a hexagonal cap screw M8, the diameter of itd head being exactly 13mm. IT fits absolutely inside the metro and information technology is easy to weld.

The last part of the build regards the kick-bandstand. Unfortunately this diminished component it's actually peerless of the trickiest!
Our kick-stand moves rotating on 2 pivots grafted on two bushings welded to the frame, and when it is in its parking mode is positioned with an inclination of about 5 ° to the footing. This tip is sufficient to ensure a permanent stop, and prevents the centre of gravity of the wheel to move too far cheeky. By using a higher angle you'll put on the line that the plain-stand gets stuck when pushing the bike front, fashioning it difficult to use.

The other kick-stand feature is the length of the leg, that we have fashioned soh as to bring up the front pedal off the background of about 20-30mm. It is a fair compromise, allowing a good occlusion over sandpapery terrain or slimly downhill, while avoiding to lift the bike too much, making a stop very effortful particularly with front load.

At this point our frame is complete, ready to be assembled with all the components.

Step 7: Painting, Assembling and Riding

At long last, our frame is ready to atomic number 4 varicoloured! We chosed a hardline powder coat. In the pictures you can see both examples of different colours and builds. You can check some more examples here.

Blessed cargo to everyone!

1 Person Made This See!

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