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Sep 30, 2015, 03:14 PM
B for Bruce
BMatthews's Avatar
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Making up tools to make our life easier- Rubber motor jig

Making up motors is one of a Free Flighter's duties if they want to lean towards the quieter and more sedentary form of flying encompassed by flying rubber power models.

Years back I made up a motor making stick out of some old scrap of wood. It was so rough that it even managed to give me an occasional sliver. The nails I used for the pegs got snagged on just about everything unless I removed them then they just plain got lost.

When tidying things up for the move I quite happily tossed it away with the rest of the scrap and useless things I'd collected or made.

So I finally got around to making the Mark II version today. This one should be a keeper.

It's a scrap strip of pre-finished 1/2 inch birch veneer plywood left over from my shop construction. And this time I took an extra 15 minutes after drilling the holes to make sure the pegs don't go AWOL. I routered out a 1/2" wide shallow slot then drilled a little deeper at the ends and middle to allow for gluing in a 1/2" super magnet and for the heads of the common nails to fit down into recesses. So now they sit below the surface and are snag free. Yet as long as I don't trim my fingernails down to the quick I can easily pry them out to use.

The jig is 4 inches wide which may seem a little much but it's nicer than the 2.5" (a piece of 1x3 was used before) of the old one which frequently saw the rubber strip falling off the edge and snagging on those darn slivers. This one being a little wider and flatter didn't make me notice if I did lay the rubber over the edge or not.

Holes are drilled at 1" increments which I feel is fine for what we're doing. More serious use might make it worth doing at 1/2" increments. I can't see it though unless making up weight rule motors for things like P-30, Coupe d'Hiver or F1B. And in that case you'll likely want a channel like track which lets you put the adjustable pin at ANY location to suit the weighed amount of rubber.

I didn't bother with any holes inside of the 12" length. And truthfully I'll likely never use any of the holes at least out to 18". Such motors are generally single or at most double loops and I make them from a single then fold it over. But including them helps make it look like I care.....

After using it to make up 4 motors to use in my Miss Canada Sr this coming weekend down in Oregon I'm convinced that this version is a real keeper. A nice jig like this makes making up the motors quick and easy. A section of the board could be a note pad area with names of the models and motor details. Or use the back of the board for more room. If you use fine tip permanent markers and finish the wood with a couple or three coats of polyurethane it'll take the ink just fine but if you crash or lose the model it's easy to use some rubbing alcohol to remove an entry if you wish.
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Sep 30, 2015, 07:21 PM
Registered User
Thanks for sharing that, Bruce. It's better thought out and a definite upgrade from what I have been thinking of doing.

Oct 06, 2015, 09:29 PM
Registered User
Thanks for posting! I'm sure your jig works well, but just the idea of a tying jig got me going. My question is what knot?
Oct 07, 2015, 01:08 AM
B for Bruce
BMatthews's Avatar
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I'll have to try those options. The fisherman's I knew of but have not tried it for rubber. The other in the middle and presumably the last picture is one I'll have to try.

Up to now I've always used a basic reef knot with simple overhand knots in the free ends. The idea being that the overhand knots serve as a block to sliding through the reef knot.
Oct 07, 2015, 09:33 AM
Registered User
All 3 have worked well for me. I like them because the ends lay flat against the loop instead of being at 90 degrees. The one on the left is the least bulky. The middle one (the tape knot) was recommended for rubber motors in a couple of places online. If you go to my profile to "all posts by Yuvie1" you can a find post called "knots" from a while ago where I posted these same images with more detailed explanations. Good Luck and nice talking to you Bruce!

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