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I’m planning to build a pedal car for kids (which I would love to use too), and many of the samples I saw on internet uses one-side Axle, I know wheel chairs and some brands like Cannondale use it but I can’t find any clear information about it, so my question is: Any regular axle can be used as one-side axle (ending it with a washer and nut) or it should be specific for that? This question is from the axle strength perspective, considering that the weight will be distributed into four wheel.

Thank you

  • In short: not for adults. But 12mm, 15mm and 20mm axles are relatively common, they're just not usually found on junk bikes at the local tip. If you have a local recumbent manufacturer they will almost certainly have what you need, but one wheel and axle will probably cost more than a cheap bike. You can make 4 wheel bikes with double sided axles - many Rhodes Car designs do this, and a lot of bike trailers. – Nuі Sep 10 '16 at 22:30
  • Thank you, considering all comments I move to use regular axle supported by both sides. – Marco Sep 13 '16 at 20:09
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Consider the design of a conventional axle. This is a cutaway of a rear hub, so just look at the right-side and imagine that reversed on the other end.

enter image description here

In the middle is an axle of threadded rod. A bicycle has maybe 15mm of this poking out on either side, and it is supported on the dropouts of the fork or frame.

If you replace this axle with a much longer one and only support it on one side, then you risk bending the axle just outside the locknut.

By comparison a wheelchair axle (aka a stub axle) has a short shaft but its much meatier. In this image, #38 seems to be a collar or similar to spread the load.

enter image description here

Drive

Also consider that bicycle wheels do not take drive through their axle. THe axle is fixed and the wheel rotates around that.

So your pedal car won't drive through the axle very well. Instead you want the bearings to be on the body of the pedal car, and the whole axle and wheel should be locked up, something like this:

enter image description here

So the rear wheels are direct drive.

Safety avoid the temptation to make a three-wheel pedal car. They are inherently tippy, and not recommended.

Steering A four wheel pedal car will probably need ackerman steering else its hard to turn. Depending on your kid's weight this may not be an issue.

enter image description here

  • Thank you so much, very clear explanation, I will consider all your recommendations. – Marco Sep 10 '16 at 18:16
  • @Marco Afterthought : You'll also want to consider what happens when not on flat ground when fully loaded. Do you incorporate some suspension, or simply build the chassis strong enough that it can cope? Having direct drive (ie a beam drive axle) means it won't get cross-axled, but if you used an open differential then there's the possibility of getting "hung up" with the drive wheel off the ground. – Criggie Sep 10 '16 at 22:20
  • Thank you Criggie. Considering your previous comments I was planning to make it using regular axle, like this one link (eliminating some parts to reduce weight), do you recommend to add suspension to design or it looks strong enough? Thanks again I appreciate your help. – Marco Sep 12 '16 at 17:13
  • That looks strong enough as-pictured. I'd worry about it being a little rear-tippy, with the rider's weight being mostly over the rear axle. – Criggie Sep 13 '16 at 3:12
  • Thank you, I’m agree about the seat it looks too rear, I will move it forward about a feet. – Marco Sep 13 '16 at 22:16

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