and more battery frame ideas

13 03 2010

As i as describing in my previous post, i’ve been struggling with how to make sure that the batteries stay in the frames.  I went over a bunch of different ideas, and thought the latest plan was to weld or epoxy bars to the Thundersky  end plates sort of like this:

End plates showing welded or expoxied bars

End plates showing welded or expoxied bars

Then, tapping holes in the bars/end plate and using screws to keep them anchored to the angle aluminum. This allowed me to keep all of the … existing hardware including all of the compression straps, and also got around the fillet in the 6061-T6 angle aluminum.

Mount with bar

I showed these around to some folks, and Adam (RemoteContact) from elmoto asked why i didn’t just use the screw holes for the bands.

Well….duh. that seemed like a much better idea than what i was going to do (even though i already purchased some aluminum epoxy…).

The problem with this idea was that given the way that the plates are designed, there would be space between the angle aluminum and the end plate.  this would cause things to get out of alignment.

Mount using existing holes. That space is going to be problematic...

I did like this idea however, because there isn’t much room between the motorcycle frame and the width of the 3 cell packs.  The photo below shows how tight it is between the battery frame and the motorcycle frame.  There’s around 1/2″ between the motorcycle frame and the purple battery frame when i had the bars and other stuff there.

there's not much spacing there...

So, i figured i could cut the little nubbies off of the plates, thus making the width even smaller (for frame clearance…hey every mm counts!), and also allow the plate to be completely flush against the angle aluminum.

By milling/cutting off the nubs, a flush mount is achieved.

in talking to my father-in-law, he said he would like to do the cutting on his Bridgeport milling machine.  that worked for me since i’d have to move my aluminum saw blade from my chop saw to my table saw to do the work.  (Hey, even i’m up for outsourcing every now and again! 🙂 )

Here’s what the plates look like now…

Milled End Plates

Note the bottom nubbies are gone. Flush mounting possible!

Thanks for looking.

Oh yeah, and one more thing I forgot to mention…

Since the battery frames and the end plates are made of aluminum, i didn’t want to use steel screws for anchoring since i’m a little worried about galvanic corrosion between the screws and frame.

Mcmaster-carr has aluminum screws, but they only come in english (not metric) sizes. So, i re-tapped each of the holes that will be used for mounting the batteries with 1/4-20 instead of the M5 that it was. I may end up adding a third hole for each of the vertical packs since the holes are fairly close to the edge of the aluminum.  I think it’ll be ok as it is, but i’m ok over engineering this thing since it’s “pretty critical” that the batteries don’t jump out of the frames while on the road. 🙂

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