BS Bikes Build Log

My first bike design just hit shop floors:

I spent the last few years managing and designing products at Strider bikes, the 20X was my final project at the company.

I learned a ton developing the geometry and fit for this bike, it was designed using anthropometric data to drive fit. The bottom of the adjustment range is a median sized 8 year old and the top of the range is median sized middle aged woman. The fit worked surprisingly well for the entire range of users with the only adjustability being seat height, handlebar height (using a quill stem), and handlebar roll (150 mm riser BMX style handlebar).

The main goal of this bike was to give gym teachers using the Strider kindergarten All Kids Bike program a tool to aid in visual learning that matched the kid’s bikes. The second goal was to give the special needs group another option for learning to ride a bicycle, something most of this group has been told they can’t do.

The most unique aspect of this bike is the removable pedal kit allowing to start out as a balance bike and add the pedals once the rider is ready for them.

Some of the challenges of this design:

  • Pedal kit had to mount without removing the rear wheel.

  • Pedal kit had to be adjustable to allow chain tension adjustment.

  • Weight limit of 350 lbs.

  • Had to comply with several product safety regulations for a worldwide market: ISO 4210, CPSC 1512, EN71, ASTM-F963.

Surprisingly, the strength testing associated with the toy standards was the most problematic because it was driven by the declared maximum weight. The frame failed this testing on the first go.

One of the design aspects that is most important to mass market companies like Strider is actually assembly instructions and packaging. These bikes are cranked out in the thousands, I believe Strider sold over 400,000 units in 2021, and shipped from China worldwide. The easiest way to save money on these products is to reduce shipping size so you can fit more units in the container. I had to come up with some novel ways of “idiot-proofing” our assembly, particularly adding the front wheel, fork, quill stem, and handlebar properly and having the front drum brake connected properly at the end, tougher for a soccer mom than for us. Strider is in an interesting position as they have a mix of dealers and direct to consumer worldwide, so they go to great lengths to have NO WORDS, only images, in the assembly instructions.

I learned a ton about designing bikes throughout the process, including how inefficient it can be to build bikes overseas.

Overall I am very proud of this design and am excited to see it in bike shops and gym classes!

I have since left Strider and started accumulating equipment to design and build bikes on my own terms. Currently learning the dark arts of sheet metal design and machining in my new position at a company that manufactures equipment for measuring greenhouse gas emissions from livestock.

More to come soon!

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:clap:

I am always shocked by the scale of “real companies” 400k units is no joke. That is a lot of bikes! More importanty, I think projects like this have a bigger impact on cycling than our $5k fancy bikes.

I have always had a question about kids bikes that maybe you can answer. Why are the bikes designed with the riders so upright? It looks like companies go out of their way with massive risers to get the bars up. I know kids don’t need an aero tuck, but I feel like their CG is very high and on their rear wheel. At the pump track, I witness toddlers tucking their front ends and yard sailing all the time. I can’t help but think the CG contributes.

I know I probably shouldn’t laugh, but I found this funny :rofl:

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Yeah, Strider production is pretty wild. I’m bummed I never got a chance to tour our factory in Ningbo because of Covid but during peak demand they were pumping out 3k 12" a week. Of course they are vertically integrated and also handle all of the injection molding and packaging too so there is a lot going on there.

It’s very interesting how some of those factories operate though, we went through an intermediate company in Taiwan so I didn’t actually have direct communication with the factory. They are very good at building things but don’t seem to have much in the way of engineering, simple things like go and no-go gauges were extremely difficult to implement. I dealt with a lot of quality issues but the most amazing thing is the failure rate was still only around 1 or 2%.

I can’t speak for other companies but, like most cycling companies, I think a lot of people overestimate the amount of engineering that goes into some of these products. For most brands, kid’s bikes are a secondary offering. 90% of the time they will be choosing parts out of a catalog based on available parts and there hasn’t been much innovation in this category for decades. I think that is part of the reason Strider has been so successful, that and the fact their marketing budget is 20X the engineering budget.

I think the main reason you see kids bikes with such high bars is so that the kid won’t outgrow the bike in 3 months. I can tell you that the Strider ethos is all about learning to ride and low cost of entry. The main geometry driver on the 12" bikes was actually keeping the seat tube and head tube angle in positions that allow the reach to grow as the handlebars and seat post extend, they even included a short and long seat post with the bike. Strider went so far as to eschew standard headsets for a custom PP bushing to allow them an adjustable stem length, it also reduces cost and weight significantly. Our larger bike use a BMX style high rise bar for the same reason, the thought is that this will allow for additional reach adjustment but I doubt many of the customers ever actually roll the bars.

So in a nutshell, they are high to fit a wider range of sized kids and to attempt to grow with the kids. and the secondary reason is the same reason most companies only offer one chainstay length, they are lazy. I basically created a bike frame design process for Strider since they had never taken a design from concept to production in a standard manner.

Definitely some odd design criteria on this bike but it was a fun project!

My biggest regret on this bike, and this is true of most kid’s bikes and low cost options, is the amount of disposable parts still being specced. The chainring is pressed onto the cranks (and usually way out of alignment), the drum brakes are riveted to the hub so you need a whole wheel assembly to replace the pads. It is good for keeping costs low but I can’t get on board with that ethos.

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Sorry, it’s time for me to bail on the forum.

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I hear specialized spent millions on R&D developing the hotwalk carbon. :wink:

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Sorry, it’s time for me to bail on the forum.

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At the pump track they OTB no matter what :rofl:

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A Strider-like push bike is in the plans for 2023, I have seen a couple with CK/Phil components and I am looking forward to spoil my niece! I’ll definitely reach out before starting!

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Sorry, it’s time for me to bail on the forum.

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Heck Yes! I figured I would start with what I know so I have one in the works as well; Plus the Non-Compete Strider made me sign rubbed me the wrong way so my first sale will be a balance bike :wink:

Just got my dropouts, I went with the Strider “Standard” to make finding parts easier.

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My balance bike manifesto:

Children’s bikes, especially balance bikes, are unique from adult bikes in that the saddle height will typically match the max stand-over height of the child. With a balance bike, they need their feet firmly on the ground while perched on the saddle for propulsion and balance purposes. Proper fit on a balance bike will have the saddle MUCH closer to the ground than a proportional adult bike. This is true of most kid’s bikes including those with training wheels (I could write pages on why training wheels are a TERRIBLE idea for teaching cycling).

The typical skills progression on a balance bike or any learn to ride bike is as follows:

  1. Child walks with bike between their legs, not perched on the bike in any way, just in contact with the handlebars.
  2. Child perches on the seat with feet firmly on ground and rolls around, eventually learning to turn by leaning.
  3. Child becomes proficient at balancing and begins to glide rather than walk.
  4. Child gains confidence to stand on the frame and glide without feet on the ground.

As you alluded to, Step 4 becomes a critical point in learning to ride because this will eventually translate into riding skills which is what we are trying to foster. With a balance bike, pedaling will be the next step and handled completely separate from riding skills.

So know that we have the background, we can look at the dynamics of the rider-bike system. Bike design should not be only about the shape of a human but also the way a human body moves through space, this is something that anthropometrics cannot account for.

When the child stands on the frame or pedals, we want them to assume what is known in the cycling skills world as the “neutral” and or “ready” position.

In this scenario, having a handlebar with a large amount of rise is beneficial because it allows the proper body position for learning riding skills, which is the goal at this point, they can learn how to pedal perfect circles next year :wink:

I like the illustration above for a few reasons but it does highlight the similarities between a childs bike and a MTB with the seat dropped. The handlebar to saddle height is increase to aid in proper skills execution. This is the beauty of decoupling the pedaling from the skills development at such an early age!

Keep in mind, this is why it works out ok, most brands haven’t put this level of thought into their balance bike designs.

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Sorry, it’s time for me to bail on the forum.

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I did not criticize Strider, they are one of the few companies progressing kid’s bike development. Striders use a quill type system to allow for a large amount of adjustment on their bikes and understand that weight is the biggest enemy in gettingsmall childrento enjoy bikes.

It is all of the major bike manufacturers that slapped together a balance bike to round out their line uo that i meant to call lazy:

This monstrosity comes to mind, the thing is a tank. It has been proven that balance bikes do not require double triangle construction to hold up. I’ve seen those tiny striders with just a downtube and chainstays hold up to some crazy abuse!

The contemporary threadless headset, stem, and bar combo offer zero adjustability so they just placed them sky high in an attempt to cover a wide size range. Many companies are using shrunken down adult bike components which are just heavier and not necessary. Strider does it right by making all of their own components.

A company that i think does even better is Woom but they are definitely a premium brand.

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We all know those Commencal kid’s bikes are really marketed to their dads

Thanks for the insight on kids’ bikes. It’s probably more thought than anyone has put into the subject!

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Do we need a kids bike thread? Somewhere to share builds as well as commercial products that might be of relevance. Just came across this modular design that looks pretty neat.

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Life has gotten busy this spring: I’m getting married in two weeks (on top of a mountain at the end of a gravel road of course), I have been putting the finishing touches on launching my MTB coaching business [elementalbikeskills.com], I’ve been trying to train for a 210 mile gravel race that is just over one month away [https://www.pineislandgravel.com/copy-of-gold-rush], and slowly building my shop and skills.

I’ve made some shop upgrades that I’m pretty excited about:

  • I got a full size vice and finally got it mounted and halfway organized. I’m gonna need a sturdier bench to mount it to in the long run. I also have my tube notcher (named Nibbler) setup pretty well but I’m already planning on hot rodding it with an Arduino controlled auto feed.

  • Got some real hole saws so I’m not cutting on one tooth and made a quick storage solution for them:

  • Practicing my fit-up and welding. I’m just starting to play around with pulse settings and lay wire, between moments of brilliance were moments of utter failure. I need to play with my setting more, kept having the rod burn off before it was in the pool, I’m thinking I’ll try reducing my amperage and increasing peak time.



  • I also purchased a simple Vevor tube bender that I am hoping to upgrade for bending rear ends. I have access to a Haas 5-axis CNC at work so I’m planning on designing some dies and follower blocks for it.

  • I purchased tubing for my first batch of 3 balance bikes but I am still deciding if I’ll bend the stays or come up with a sheet metal yoke, should have a plan to start building this weekend!

Cheers!
BS

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That hole saw storage is really cool. Great job.
I really need a 3D printer……

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@sikocycles Thanks! I love the flexibility of a 3D printer, You can pick them up for a very reasonable price these days: Creality Ender 3

I bought one of these this year: Bambu Lab X1-Carbon Combo 3D Printer | Bambu Lab US

It’s been pretty amazing to have multi-material capabilities and I can handle exotic materials like glass infused nylon for super rigid parts. It also prints 5 times faster than my old unit. I even talked my company into buying a few for production, they are making our $5k production printers look bad…

If you have CAD skills, a 3D printer is one of the best investments you can make.

Here’s a few more examples from this weekend of why you should pick one up:

Planning on wrapping the tap up this week and finally feeling confident enough to start on some balance bike frames!

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Thats awesome

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I have opinions and recommendations :slight_smile:

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