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Suggestion for mounting BOE-Bot servos — Parallax Forums

Suggestion for mounting BOE-Bot servos

Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
edited 2013-10-20 13:52 in General Discussion
Anyone who's ever assembled a bot on the BOE-Bot/ActivityBot chassis knows how aggravating it can be to install nuts on the screws that hold the wheel servos in place. And once you get one started, it's tempting to stop tightening when the nut starts to spin, just because it's so hard to get a wrench or pliers in there to hold it. As a consequence, many servos do not get tightened down as well as they could be. The latter could become an issue with the ActivityBot especially, since those same screws also hold the encoder bracket, which should be held tight to get the best results.

To address this issue, I've designed a self-threading backing plate to replace the nuts entirely:

attachment.php?attachmentid=104207&d=1380748315

It's laser-cut from 3/32" acetal copolymer with 0.096" holes (thanks, Matt!) into which 4-40 screws thread neatly and hold tightly. To install a servo, it's necessary only to position the backing plate over the back of the servo and start turning screws. No needle-nosed pliers or tiny fingers are needed. Here's a photo of the plate installed:

attachment.php?attachmentid=104209&d=1380748317

Attached is a DXF file so that Matt can try one out on Parallax's laser cutter.

-Phil
backing_plate.jpg
901 x 394 - 29K
dxf
dxf
backing_plate.dxf
17K
backing_plate_installed.jpg
575 x 479 - 45K

Comments

  • NWCCTVNWCCTV Posts: 3,629
    edited 2013-10-11 20:19
    That is definately cool. Good job Phil. Any chance of getting the file in something other than .dxf?
  • Duane DegnDuane Degn Posts: 10,588
    edited 2013-10-11 20:31
    Any guess on how many times the screws could be used on it without the plastic stipping out?

    I have an aversion to self threading plastic holes. My S2 screws barely stay in place since I've opened it up so many times.

    What if instead of holes, you cut hexagons to hold the nuts in place (so they don't spin when tightened)?
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2013-10-11 21:56
    NWCCTV wrote:
    That is definately cool. Good job Phil. Any chance of getting the file in something other than .dxf?
    Thanks, What format would you like?
    Duane Degn wrote:
    Any guess on how many times the screws could be used on it without the plastic stipping out?
    According to Matt G, even if the holes do strip, the Delrin is self-healing and can hold a screw again. The 3/32" material holds really tight, BTW. It would be hard to strip it. As a bonus, it acts almost like a Nylok nut, keeping the screw from coming loose.

    -Phil
  • NWCCTVNWCCTV Posts: 3,629
    edited 2013-10-11 23:05
    Thanks, What format would you like?
    MS Visio possible? If not it's no big deal. I have a AutoCAD file reader somewhere that I could use.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2013-10-11 23:57
    Sorry, I don't have MS Visio or even know what format it uses.

    -Phil
  • Duane DegnDuane Degn Posts: 10,588
    edited 2013-10-12 07:29
    Phil Pilgrim (PhiPi) wrote: »
    According to Matt G, even if the holes do strip, the Delrin is self-healing and can hold a screw again. The 3/32" material holds really tight, BTW. It would be hard to strip it. As a bonus, it acts almost like a Nylok nut, keeping the screw from coming loose.

    Thanks for the information Phil.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2013-10-20 13:52
    I just assembled my ActivityBot. I didn't know about the little Delrin wrench and the NyLok nuts until now. That combination works great! So I'm withdrawing this thread's suggestion. It's unnecessary.

    -Phil
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