First size test for the bike wheel hub battery I'm designing - which I'm going to tongue in cheek refer to as the Tri-Force due to its three pieces - is a success. There's enough clearance between the spokes to get the pieces in and out.
The plan is to attach them with straps so I can maneuver them, then secure them at the hinges. Depending on the angles I may be able to skip the hinges.
[#]bikeTooter #3dprinting #diy
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I'm enjoying the challenges of designing for the "Tri-Force" bike wheel hub battery.
Since the lights will be remote controlled, I need to fit a receiver into the plug; I don't want in the battery because that may complicate charging.
So, I have to fit a 11x24x8mm chip, and the eight wires involved (two from the battery, two from the lights, four from the chip) all into as small a form factor as possible, all in the space between two spokes forming a wedge.
Fun!
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After five and a half hours, the first full scale test is ready. And there are notes.
To accommodate using battery clips instead of a modeled holder and a nickel strip tail, I had to increase the thickness to 36mm. Now it barely fits between the spokes.
But, I was able to get in on and off with two of the three hinge pins in, which is good.
When the clips arrive on Tuesday I'll iterate on the thickness - I may have to use 21700 cells instead of 26650 cells.
[#]bikeTooter #3dprinting #diy
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The mark II Tri-Force bike wheel hub battery fits perfectly. The extra 4mm of clearance makes it easy to install with two of the three hinge pins in; although it helps to have three hands.
This means I have to go with 21700 cells instead of 26550 cells, which is fine. I think i need to recheck the outer diameter of the hub - 32mm is feeling a little snug.
Fortunately I already have a hinged ring designed for the handlebar mount, so I can reuse that.
[#]biketooter #3dprinting #diy
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The really cool thing about the lights I'm going to power with the wheel hub battery is they're remote controlled via a switch on the handlebars, rather than having to reach in between the spokes to turn them on/off.
I am not an electrical engineer but I feel it's probably a bad idea to have electrical components dangling freely in your wheels.
So I've designed a piece to go around the wires for the LEDs to house the receiver and the many wires involved.
[#]biketooter #3dprinting #diy
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A challenge in #3dprinting a bike wheel hub battery and controller will be the transmitter. I opted for an A23 battery for its voltage and form factor. Fortunately you can buy tiny little battery clamps to secure it.
Unfortuately there's exactly zero clearance between the battery and the base plate when installed, so I'm unsure how I'm going to make this work. I can't print in place because they'll interfere with the tool head.
I'm thinking a very small clip?
[#]biketooter #diy #electronics
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It's print day today for the bike wheel hub battery. I went through most of a spool of PLA iterating on designs, and now I can print the "final" parts.
I'm a little disappointed that I ended up having to have multiple shell variations - I could get away with just two if I had metric drill bits.
Oh well. I didn't design this for mass production.
[#]bikeTooter #3dprinting #diy
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A weekend of printing later and all the parts for the bike wheel hub battery - aka the "Tri-Force" - are ready.
The battery clips have pins that fit into slots and are glued in place. Everything else will be held together by nuts and bolts - a grand total of:
Too many fasteners? Not for an #ebike part!
[#]biketooter #3dprinting #diy
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"Ryan, you don't have to design everything to be a two identical parts with rotational symmetry."
"BLASPHEMY!"
It's an assembly jig for the battery case - to hold the halves of the three shells in situ while I do the wiring.
Why two parts? Because one continuous piece wouldn't fit on my print bed.
[#]bikeTooter #3dprinting #diy
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Let there be light!
I'm a little concerned that I seem to have fried the BMS on my test battery during this test - hence the pack of AAs. It did fine for the bench test a few weeks ago...
Oh well. The transmitter ia wired, and so is one of the receivers. I'll wire the other one tomorrow and see if I can pair it with the same transmitter.
Then we'll wire the battery cases, and once I'm sure it all works, then we'll order the LED strips.
[#]biketooter #3dprinting #diy #electronics
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I tallied up the cost of building the bike wheel batteries last night.
$70 - and an extra $30 in shipping.
Sure, I could probably get that down if I could get everything in one place, but the full parts list includes forty eight screws, twenty four coupling nuts, twelve battery clips, six battery cells, two battery management system circuits, and two 2.1mm jacks.
I'm sure I might be able to get all of that on Amazon, but there's no telling the quality of it...
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And the battery cells themselves are half of the cost of parts. So there'd be minimal savings from redesigning the part to require fewer - or even no - fasteners or battery clips.
Ultimately, if the design even works, I want to put it out into the world. The parts are easy to acquire. There's not much soldering in the wiring - I taught myself in a weekend.
It's just the cases that a person needs... so I guess I should research print on demand solutions.
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No prototype survives contact with production.
The solder joints must be imperfect, because the light is temperamental and will turn on and off as I move things around to close the shells. The wires are interfering with each other, physically at least. There's too much happening in the main shell.
No worries, I can iterate on the design. I need to give more room for the wires...
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@yantor3d I can't tell, you're using stranded wire, right?
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@trouble I think so - 24 AWG stranded. I'm tinning the wires before I solder them, but the battery clips don't seem to like to be soldered to...
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@yantor3d I would use larger wire. Automotive uses min size of 18 GA due to vibration and flex. 20 GA should be fine for this use case, except for battery shorting out (fuse can prevent melt down). Also consider batteries with solder terminals. Harder to get, but eliminates the springs as points of failure.
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@trouble Noted. I'm looking at re-arranging the layout - inverting the middle shell - so the wires will all be on one side. I'll try a thicker gauge of wire next time.
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