As I wrote in my intro I would like to build something basic for (and with) my son.
I have a technical background, I can solder reasonably well, and know my way around a drill. Here are the requirements, some questions, and my initial thoughts.
Requirements
Slow: Cause I hate writing “safe”. 10mph (or 16kph as they are called in Israel) would be great. Better would be if it could reach twice as much and I could limit it with the ESC.
Cheap: I’m sending him to work in the mines, but he’s very weak so he can’t make much $ for now. I have to admit that I already realised that it would cost more than I hoped it would, but I’m still hoping to keep it cheap.
Limited torque: the kid is 35kg, and with a restrictive diet he shouldn’t grow much. His pickaxe is just another 1Kg. There are no big hills to climb, and limited initial acceleration is a plus.
Limited range: Better for ensuring he comes back home once in a while to charge, and not cohorting with those scary looking skateboard dudes.
My thoughts so far
Single hub: Cheaper than dual. Simpler assembly than a pulley/mount system.
Single battery pack: Small, lightweight, limited current.
Low Energy: Compared to a “standard” build, we aim for
60-70% lower weight
50% less distance
50-70% lower upper speed
which my “bottom of an envelope” calculations shows much lower energy consumption.
procurement: Besides a battery which I can try and get locally, I prefer stuff that can be ordered from Europe or [China], or from the US for reasonable shipping prices.
Specific questions
Is there a cheaper way to go instead of a vesc? I understand the importance of it, but considering the small battery and limited speed/torque, is there a cheap alternative?
Should I consider a really fast skateboard so he can work an extra shift in the bakery?
I assume a single hub can be enough. I also assume it’s installed on the back truck. Is that crazy?
All my three kids work in mines. They leave at 3.45 AM. No time for breakfast. Without them we’d be broke. I usually spend my days lying on the sofa making sure I won’t be too tired to welcome them back home when they get back at midnight.
I’m serious! My son did ask me to do a project with him, and that’s what we’re planning. I’m already teaching him about torque, electricity, physical design… It’s a great process. And when he grows up he can even become a mining engineer!
PS: Just for full disclosure, there no (and never were any) mines in Israel.
PSS: We do have bakeries. Someone got to make those Challah bread…
As far as the build, I would suggest going belt drive. Its a lot longer lasting and much better torque. I would also recommend a vesc, an RC ESC is gonna be nothing but trouble and the cheap Chinese ESC’s aren’t terrible but they offer no programming options. With a vesc you can limit duty cycle and amps to control top speed and torque.
These were my plans for my sons esk8. Slow and steady. Bought him a meepo. That thing now runs 2 focboxes and a 10s 5p with the amps far too high because the little shit is a speed demon. I’m now building him a mini mountain board so he can hit the off road trails…when will this obsession stop.
Its actually a great bonding process and they learn so much during. Hes the one who sets his own parameters now with some basic ground rules in not blowing the thing sky high. Hubs are not all bad for small kids. If your son is anything like mine then he won’t be careful with it at all and with belts and satellite motors there is an awful lot of undercarriage to wreck. Definitely go with vesc over esc though. Much more control for you as the parent. Good luck!
@b264, @mmaner, thanks for the input! I thought hubs are “the future”. Maybe it’s simply not the future yet…
A belt drive will be much more fun to build (plus the added “gear ratio” tutorial for my son), but wouldn’t it also be more expensive?
Can you give a rough guidlines for a <40Kg rider, <20 kph top speed and just reasonable torque?
A single 6355 170kv on a Gear ratio of 2.4:1 with a 6S1P battery should be fine? Would love your input on this.
Here is a calc I used. The default is 18 W-hr. I have no idea what to put there, but I assume it shold be lower with a much lower load. Any thoughts on this?
@dareno, that’s a valid point - not only there is a better chance of something breaking, he’ll probably let his friends ride it and the chance of misuse grows even more… Did the meepo had just one hub originally? What do you think of the original plan I’ve put?
No they are a twin hub design and very cheap for what you get. A single hub design is fine for a 9 yo. Put it this way when the meepo was stock it pulled him up hills as fast as my dual 6374 10s board got me up them. I had the little git on the flat though. Great plan for a starter set up for him. Again though if hes anything like my boy then he will be riding that thing like a pro in no time and making his dad look slow so might be an idea to over engineer it to start with and use limits rather than have to build a complete new set up when he gets bored and he will.
