Cargo bike design considerations

M

mackeenj

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35
Hello all!

My regular disclaimer: sorry the post is in English...I am based in the USA and cannot read or write in German. Also, this is the only source of information of its kind (that I can find). I use the google translate function, so feel free to post in whatever language you're most comfortable!

You may have seen my current cargo bike, which is actually quite great. But, I may have the opportunity to help design a new (and better!) one from the ground up. I want to know the forum's practical experience and theoretical implications of the following:
  • wheels of the same size (both small or both large) versus large wheel in the back with small in the front
  • cable versus linkage steering (or other
  • hub steering vs. fork (this one's for you, @bastiaen)
  • 3 (or more!) wheels versus 2 (not really a factor but I threw it in here for discussion's sake...I will 99% go with 2 wheels)
  • "traditional" chain/sprocket vs belt/internal gears (responsiveness versus all-weather maintenance, right?)
  • suspension (front, rear, both) vs. just using bigger tires
  • any other comparisons you can think of!
Thanks!

Josh
 
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Hi Josh,

- smaller frontwheel = larger pothole
- cable vs. linkage steering = religious question! Well made, both are ok. Badly made both are awful or dangerous
- hub, of course!
- if You ride a 3-wheeler in such a way that it goes on 2 wheels 99% of the time, You might as well build a 2-wheeler in the first place.
- Since I am not particularly interested in keeping my trousers clean and a heavy chain on a hub will outlast any belt, I´d say hub at any rate.
- I think a decent suspension on a cargobike has never yet been attempted in principle. Go ahead!

Other design considerations:

- short vs. long (if-Long John-type)
- Long John vs. Long Tail
- vertical vs. conventional steerer angle (angle of the tube the handlebar rotates on. (That one really makes a difference in design, size and feeling)
- progressive steering vs. parallel steering (does the front wheel rotate more than the handlebar to compensate vehicle length or not)
- upright vs. sporty seating position (as in any bike)
- "female" step through or "male" top tube
- high vs. low BB (I prefer low on a cargobike)
- double vs. single kickstand
- flatbed vs. spaceframe
- smaller vs. larger REAR wheel, too...
 
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My first DIY had two 26" wheels. Despite the not fully matured steering system, it was the smoothest ride I ever had on a cargo bike.
 
Hi Josh,
just a few thoughts:
- there are other designs than longjohns too
- with children the demands will change quickly and frequently (stop growing!:))
- you are tackling quite demanding transport situations with your bio bike - you could tackle even more demanding ones with a motor!
- is there the possibility that your wife rides the "train II" herself?
- you are driving a lot so longevity of the frame will be important

Bob
 
Hi,
Great projects you have! As our wife's height seems similar: have you considered a shorter seat tube to enable persons with inner leg length below 78 cm to ride it, too?
 
In response to @Rasende Badewanne and @jaho, I would like for my wife to be able to ride this one. Even though she has no intention of riding the cargo bike (for now!), she cannot even fit the current one, which is sad. With possible e-assist on the new one and built to fit both of us (maybe with a dropper seatpost :unsure:) she would be more likely to ride it one day.

@bastiaen Can you explain more about the progressive steering? Has anyone on the forum attempted this? Are there any bikes you know of that have it? My builder has experience and contacts in the human-powered vehicle world, so he's already thinking about steering mechanisms different from the norm. We will be exploring this further.

The intention for this bike is:
  • make it the easy commuting choice regardless if I am late or not carrying a big load (right now I may use my road bike to go fast if I have no load) - e-assist would assist with this
  • wider tire clearance for when the road ends and possible suspension
  • since I am forgoing a new fast road bike for this build, I would like to be able to take it on the group ride (maybe even with a kid onboard!) - motor will help
  • smaller footprint - able to easily transport in the minivan; also, it lives inside and I would like it to take up less space in our small house!
  • Not planning to live where we live now for too much longer (rural Louisiana, USA - not very bike friendly and not much infrastructure) and would love to move to a community where more is accessible by bike -> when this happens, this bike should become the minivan replacement I dream it to be

My ideas are:
  • wheels of the same size allow for one tube/tire size -> larger wheel size has more tire options
  • cable steering so turning is not limited (I find my current one very limited with the fender on, especially when I'm trying to maneuver it into its parking spot - not riding!)
  • hub steering
  • 2-wheels (I meant 99% chance I would ultimately go with a 2-wheel build :))
  • semi-adjustable position for both my wife and I to ride - me with sporty, her not as sporty
  • I'd like the cargo area to be a flatbed to allow for maximum flexibility as those kids keep growing! I'm not sure how to design this in the best possible way.
  • some sort of suspension system
  • electric assist - maybe even up to 45km/h, but would need to review my local rules and regulations
  • Either a coupling system to split the bike (concerned about load capacity) or something like the Cleaver cargo bike (here or here) which is also similar to the Brompton's back half folding mechanism...again, not sure how possible this is and feel like it will severely impact my carrying capacity

I'm not sure what other design elements I should take into consideration! For reference, I started discussions with the builder last week but the delivery date will not be until 2024. :oops: Would love to use this forum in the meantime as a sounding board for my own ideas and a way to generate ideas I hadn't thought of before.

Cheers!
 
mackeenj schrieb:
Can you explain more about the progressive steering?
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I think it simply means that the steering arm (for rod steering) that connects to the handle bar is longer than the one that connects to the front wheel, so that the front wheel turns more than the handle bar. This reduces the amount of handle bar turning required to stabilise the bike. If you got the right ratio, you get a similar steering feel on a long bike as on a bike of normal length.
 
As far as coupling is concerned, have a look how workcycles have done it on the KR8:

Bakfiets en Meer » Reassembly of a WorkCycles Kr8 Bakfiets

www.bakfiets-en-meer.nl www.bakfiets-en-meer.nl

Maybe not the most elegant coupling system, and not for taking the bike apart every other day. But it's very simple and extremely sturdy. Has not caused a single issue on my KR8, even though I have been riding the bike with a total weight of about 230-240kg. If you would like me to measure any dimensions on the coupling, just let me know.
 
Exactly what I was looking for @kistenfahrrad ! Thank you!

One other comparison would be location of the motor if I get one...front, rear, mid...I'd love to be able to have a dynamo to run lights even if I don't have the battery, so I'm thinking mid. Thoughts?
 
mackeenj schrieb:
  • wheels of the same size allow for one tube/tire size -> larger wheel size has more tire options
  • cable steering so turning is not limited (I find my current one very limited with the fender on, especially when I'm trying to maneuver it into its parking spot - not riding!)
  • hub steering
  • 2-wheels (I meant 99% chance I would ultimately go with a 2-wheel build :))
  • semi-adjustable position for both my wife and I to ride - me with sporty, her not as sporty
  • I'd like the cargo area to be a flatbed to allow for maximum flexibility as those kids keep growing! I'm not sure how to design this in the best possible way.
  • some sort of suspension system
  • electric assist - maybe even up to 45km/h, but would need to review my local rules and regulations
  • Either a coupling system to split the bike (concerned about load capacity) or something like the Cleaver cargo bike (here or here) which is also similar to the Brompton's back half folding mechanism...again, not sure how possible this is and feel like it will severely impact my carrying capacity
Zum Vergrößern anklicken....
Josh, seriously, I think You are overloading the project with conflicting constraints.
 
That could very well be true, @bastiaen! I just need to hear it from someone else for it to stick.:) What exactly do you think I may need to cut or prioritize?

@Rasende Badewanne and @bastiaen I will search the forum for a motor discussion as I'm sure there are many...I may have prematurely mentioned it before doing my proper research.

I'm also having trouble finding a thread I failed to bookmark...it had to do with "what would you do differently on your cargo bike next time" or "lessons learned." I cannot seem to find it. Do any of you know which thread I speak of?
 
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I think, You´ve got to differentiate between Your basic demands and possible technical solutions:

A smooth ride is Your demand. A large wheel or a suspension are two possible solutions.

Each possible solution comes with a compromize. A larger wheel for example will compromize maneouverability to a certain extend.

Another example: You want to transport the bike in Your minivan (basic demand). A splittable frame is a possible technical solution but You might as well build a compact bike in the first place. Which conflicts with a larger front wheel. Unless it steers to 90° - which might not necessarily indicate a cable steering - or You can live with detaching the wheel for each transport.

At any rate it is not good to start the design with just wanting some technical solution simply because it looks or sounds cool. But if the building is a hobby and You can live with a compromized result beacause You just want to try out something new, that´s fine, too.
 
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So you would say...the correct approach would be setting the basic demands and seeing what technical solutions flow from them? I'm not the builder, so I wouldn't say it's a hobby. But I do like bikes. And I'm liking cargo bikes more each day.

If I boil it down to core needs of the next bike, I would like more capability "off-road" (gravel/dirt road, nothing too crazy), smaller footprint for storage and transport, and have the ability for my wife to ride (about 30cm height difference between us).
 
The builder is another constraint: You might find an ideal concept he can not build. But I´d leave the production-driven considerations out for the moment.
I am missing Your transport demand from above post. After all it is a cargo bike.
As for You and Your wife: You should in principle be fine with any concept unless seat tube and steerer tube are not parallel, so that reach increases by lifting the saddle.
 
Of course the builder has final say on what he can build! He has tasked me with gathering my ideas and then we'll look through everything together.

As far as cargo specs, I wouldn't want a deck any smaller than my current one (94cm). I think with the hub steering I will be able to squeeze more space out of less overall length, as you know. I have four children now, but they're all quite small (for now!): ages 5, 3.5, 2, and 1 month. I will probably take the box I'm making for my current bike (modeled after @kistenfahrrad 's box here) and adapt it to the new bike. Fitting in the minivan is probably a silly requirement. I will have to mull it over and decide what is really important to me.

I will be exploring the forum in detail in the next few months as my homework. Sounds rough. :)
 
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