F/FSport I
by david mitchell You can reach David Mitchellat 230 Walnut St. NW, Washington, District of Columbia 20012, or via e-mail at
davedge@me.com
don’t know about you, but there’s noth- ing I like better than re-purposing ex- isting materials or hardware to arrive at a neat solution to a problem. How many times have you been prowling about the local hardware store, looking for the per- fect this-or-that to do such-and-such, been asked if you needed help, and had to just shrug and say “No thanks?”
You could always try to explain. Something
like, “I need a device that allows me to quick- ly, cleanly, and securely connect and discon- nect the hook of a 20:1 winding device to a power train, in a way that doesn’t require reinventing the common structure of the power train itself, ideally avoids the transfer of a slippery, tightly wound rubber motor to a prop shaft hook under often pressing circum- stances, and that allows very high amounts of torque to be safely wound into the rubber motor. The device should be small, easily stored, cheap, and commonly available.” That should get rid of the pesky employee, and al- low you to get on with your scavenger hunt. It is, after all, one of the quiet pleasures of base- ment engineers everywhere. We are going to rob you of your joy for this particular proposal however, because we have just the device for you already! Yes folks, put away your Rube Goldberg-ian contraptions and embrace the lowly alligator clip. John Ernst brought the method to my attention; Andrew Ricci, who sent the pictures, says he learned it from Doug Beards worth, who says he got it from Richard Zapf. Beyond that, I cannot trace the provenance. In any event the alligator clip—friend of electrical gadgeteers everywhere—reveals itself to be an elegant and simple solution to the above require- ments with only a few modifications.
What’s in a name?
Oh, but remember Dave’s First Law: “Simplicity is an Illusion.” You may begin to notice that not all alligator clips are alike. Indeed, you may learn that some call these devices crocodile clips and that a deter- mined search on wikipedia or even a query put directly to the local gadget geek will not clearly resolve their respective identities. Confusion reigns. I will try to clarify the sit-
PHOTO: WALLY FARRELL Wally Farrell’s take on the Thomas Vagabond. Ya just can’t beat a yellow Piper!
uation, but we must ultimately focus on function over all, names be hanged. The clip in one of the photos features a tension spring wound about the pivot point of a pair of non-crossing jaws. Following con- vention, let’s call this one an alligator clip. The second type places a compression spring forward of the pivot point of a pair of crossed jaws. Let’s call this one a “crocodile clip”. Why? Well, the biological crocodile has somewhat finer jaws than the alligator. You may say tomato..., but here’s the real dis- tinction for our purposes: the rear post of the “crocodile” clip is axial to the centerline of the clip, whereas the rear post of the “alliga- tor” clip is in-line with one of the jaws of the clip—but not the other.
While certainly not a fatal problem, this asymmetry may cause annoying vibrations when you’re winding at warp speed to avoid holding up (or missing altogether!) the Big Event. Therefore, while either type can be used, I champion the “crocodile” clip for our purposes and indeed, this is the very clip featured in the photos that Andrew has so helpfully sent to me. If you can’t find one of these at your local electronics supply
store—yeah, Radio Shack ain’t what it used to be—try looking up “Mueller BU-85” on the internet. You should be able to find ’em for less than a buck.
Okay, let’s get to the nitty gritty. Modifi- cation of the “crocodile” clip for our purposes is simplicity itself. First, note that there is a small machine bolt in the rear post. Remove the bolt, and check to see if the hole easily fits your winder’s hook. If not, drill it out so that it does.
Next, drill a hole through one of the jaws that will comfortably but not sloppily fit the size of prop shaft wire that you are using. You can drill a couple for various applications. I suggest that this hole be drilled in the jaw that continues back to the rear post, rather than the jaw that is hinged, for additional safety. While this isn’t how Andrew did his in the pictures (and he’s had no problems), my thinking is that the hinged jaw could possibly become unhinged over time with wear and might fail under load, whereas this cannot happen if the the other jaw is used. That’s it. Really? Yes. The idea is that you open up the crocodile clip, insert the bent front end of the prop shaft into the hole you
PHOTOS: VIA MUELLER WEBSITE
Repurposing common everyday items for free flight modeling is easier than you think. Take for instance the common “Alligator Clip” (above left) or the
30
“Crocodile Clip” (above right). Both items become invaluable tools in winding rubber motors. Text has details.
MAY 2014
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