Jeff Minard

Projects / RadMini4 /

Second Battery Mount

One of the aspects of the RadMini4 that I really like is the dual tube design. For starters, it just just neat, but for me it’s also a great shape to build on.

The project here is to mount a second battery on the mid-tube of the bike. I modeled up the two bar frame in Fusion, measuring the tubes and spacing with some calipers.

Fusion 360 diagram and measures of tubes

I love having the dual tube setup as it allows me to model around both to create bracing that will stop the battery from rotating side-to-side – a real problem when you only have a single tube to work with.

3d modeling program showing rough shape

As there are three pieces per battery support, they need to bolt together. To do this I decided to use heat inserts, and the way this is modeled, the inserts are melted into the plastic from the opposite side of where the bolt will “pull” on them, giving them a TON of resistive strength when 3d printed.

Cross section
Cross section showing bolt locations

Finally, you add lots of chamfers and fillets to make the piece easier to print and nicer to hold.

3d model completed with nice surfaces

And the final piece works great. It’s printed int PETG which can survive outdoors no problem and VERY thick walls/infill to give it some heft. Overall these work out great. I also really appreciate that these are non-destructive to the frame – no drilling, no riv-nuts, etc.

Printed parts attached to bike with battery installed
Installed and looking great

Battery on bike close up next to stem
Battery slid all the way forward, plenty of space to remove it

If you’re interested in making your own, I’ve included the Fusion and STEP files here:

Also available on Printables.


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