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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@yantor3d Note: some BMS cut off "permanently" when shorted out, but reset when charged. i.e. good luck resetting the unit in the field unless you have a second phone battery bank to trigger the charge mode with.
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@trouble Aha! You are correct.
This is a 12V battery, so I don't know if a 5V phone battery bank would be enough to reset it...
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@trouble Although I guess if all I need is a brief 12V charge, I could build a reset stick with an A23 battery.
Edit: Oh, does it have to be fully recharged?
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@yantor3d nope, just needs to be woken up. My experience is with phone usb battery banks (wired two in series to get 10V; regulated. but don't mix your connectors up, lest you short out the pack!) However, USB-A is highly DIS-recommended. I had to replace several USB-A jacks because they couldn't take the vibration of being carried around on a bicycle.
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@trouble Good to know. I've gone with 2.1mm for the jacks. And put them as close as I can to the center of rotation of the wheel.
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@yantor3d also recommend a dust cover. Rubber will work (quick and dirty) but get several, since you will drop and lose it. Moisture, dust, and rocks inside your connectors is bad. "DC Barrel rubber plug" will find the products.
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@trouble I 3D printed the cases with a tongue and groove interlock around the perimeter, hopefully that will help keep them dry. I might do a bead of epoxy around the jack to seal it... I suppose I could print some sort of cover for the plug to give it some more protection when plugged in.
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@yantor3d I guess I'm recommending to not to overthink it. Rubber plugs are inexpensive. Try them, see if they get lost on the road due to vibration (depends which way they are facing). Then iterate. My bike hubs are always dirty, indicating the need for at least dust and road splash resistance. To test sealing experimentally, put glue on one half (left/right), and with your next iteration see if it leaked. Zip ties or string around the circumference might be a good safety cable just in case.
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@trouble Good ideas! The cable will currently run through a case to house the receiver (remote control lights FTW!) with channels to clip it to the spokes. It should probably hold. If it doesn't I can print a new version with slots for zip ties...
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