Rear Door Magnets

Now that WonderCon is over I’m hoping to go back and post details on the final few steps of my build – I’m probably going to post some things out of order, so you may see some things in the photos that I’ve not covered yet.

First up is the the rear panel/back door. I’d deliberated this for a while and tests a few different methods before finally settling on using the rare earth magnets.

I’d bought a bunch of different sizes, with the intent of using them on various spots on the droid.

One of my fears was the smaller magnets wouldn’t hold, and if I’d went with the larger magnets they’d get in the way of my movable electronics panel, or the door would be impossible to remove.

Frank Cerney had posted a few months ago about using 1/2 inch cylindrical magnets (NSN0818) from Magcraft successfully to hold the door on a wooden frame, so I decided to do something similar. Here’s Frank’s original implementation –

Frank Cerney Door Magnets

I don’t have the luxury of being able to drill holes in a wooden frame, so I needed to come up with something to hold the magnets to the skin. On hindsight maybe I should have gone with square or block magnets instead, but I was stuck with what I had on hand.

After a few experiments I ended up cutting some aluminum U channel into 1 inch chunks and bent them to clamp the magnets.

The gap is slightly narrower than the magnet, and I simply tapped the magnet in making sure they matched the opposite one.

I then took my CA glue and excellerant and glued them to the skins

I could have used epoxy, but I really wanted this to setup quick without worrying about clamps, movement etc. It seems to hold okay, but I still may still go back and re-enforce them with some epoxy at some point.

Here’s the skins/frame assembled showing the final location of the magnets

One of the issue of using the magnets to hold the door on from the sides is that the force pulls outward, instead of pulling or holding the door tight toward the frame/skin, like if I’d used screws to hold it in place.

You probably can’t tell from the photo, but this results in the door,which naturally curves a little tighter than frame, to bow out at the top.

To combat this I added a tab which will pull everything together and hopefully add a little more hold and reduce the strain on the magnets.

Again I used CA glue to hold it in place

I topped everything off by added some white tape to the inside line of the skins.

Remember I’d had a problem closing the gap at the bottom of the door once I’d cut it from the skins, so rather than fight with it – I simply masked the problem by covering the raw aluminum which blended the door into the skin. I have to thank my wife for this suggestion.

Due to the electronics panel having to swing out I had to either attach the rear power coupler to the door or make it removable from the frame. I opted for the latter as I didn’t want additional weight on the door.

I simply cut a chunk of metal (not aluminum) and secured it to the back of the power coupler. I then used a large magnet on a bracket on the frame to secure the power coupler and allow me to pull it off when needed

The good news is the door holds on great and I had zero problems with it at WonderCon – it even held on even when I did the R2 death spin :)

Posted by Chris on February 27th, 2008 in Body | No Comments

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