3D model description
This is a work in progress project. Use and modify at your own risk !
If you neither know what Hyperglide is, nor what BCD104 means, you can now safely stop reading :-)
First off, this is not my own "invention". A similar product is sold from pinion as "Pinion 104mm BCD Cassette Spider" from what I know, allowing you to use BCD104 chain rings as read cogs on a standard Shimano Hyperglide compatible body. Also the folks from the High Voltage community already produced several designs like this. They sell another product matching BBS HD chainrings as rear sprocket:
https://highvoltagekits.com/hv-shop/p/bbshd-sprocket-adapter-use-bafang-front-sprockets-on-the-rear
When using BCD 104 Narrow Wide Chainrings which you can get from Ali Express you get pretty much any teeth number you like. From 32T up to 52T. Since those chainrings are pretty cheap, combining them with a powerful bottom bracket motor like a BBS HD or CYC X1 Pro seem like a good choice to me. There are also other more durable options like chainrings made from steel. Compare to your standard BBS / BBS HD chainrings from Lekkie, Precialps, etc you can buy a looooot of standard BCD 104 NW chainrings.
Long story short:
For who is this adapter ?
It is geared to the rider of a powerful e-bike which possibly runs a throttle as well and wants to get rid of any deraileur. From my experience running a X1 Pro or BBS HD with 1:1 gear ratio or below pushes you up pretty much any hill. Running a throttle eliminates the natural "speed limit" you get from using only PAS mode multiplied with your cadence. I have included STL files and DXF files. I am not shure if any technical filament could take the beating from a powerful BB motor but for fitting / prototyping it should do the trick. You can easily get this stuff laser or watercut from a shop near you from any material you can imagine (steel, aluminum, etc). I guess any aluminum plate above 4-6 mm should be stable enough to keep things from bending. Since the motor peak powers often cause damage to the cassette body of the rear hub I included some "spacers" wiht 6 mm holes in them. You can easily attach one spacer left and right to the BCD104 adapter to spread the load on the cassette body. A cheap single speeder set with adapter rings is still needed for spacers and the mounting nut at the end of the cogset. Those going completely nuts could use two BCD104 adapters and put the chainring in the middle like a "sandwich". For this you would need a spacer as thick as the chainring.
Please note that the holes for mounting the chainring are only 8 mm. This fits standard screws. If you want to use those standard chainring screw & nut combinations and they match the thickness of your adapter, you will need to use the adapter with 10 mm in the filename.
As for princing goes YMMV but I did a quick inquiry and 6 mm V2A steel as well as 6 mm Aluminum were around 50β¬ with laser cutting. If you feel like adding two additional spacers for load spreading I guess you are somewhere around 70-80β¬ with shipment.
Please note that the adapter in the pictures was an earlier iteration and thus is lacking the holes for screwing to the other spacers. Do your test prints with cheap PLA prior ordering anything laser cut.