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Just another Ballerina


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Posted by kc on 31/01/2016 11:50:34:

I reckon your wire bender deserves a thread of it's own..........

It would be nice if you gave some dimensions for the bender such as bolt spacing and size of the steel.

It started off as a temporary bender until I had time to make something better but it's been going for a couple of years now and has do wire bending for quite a few models including coiled retract legs in 6swg wire with little effort.

The base plate is just thick plate 2" x 1/4 and about 6" long

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There are 2 M6 bolts as wire stops about 1" apart

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and a third M8 bolt the opposite way forming a gap of about 1/2" It's M8 because that's the minimum radius for bending undercarriage coils. This is the pin the wire is bent around.

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The pin projects from the base plate about 20mm which is enough to form 2 coils in 6swg or 4 coils in 12swg

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The base plate is gripped in a vice by the projecting nuts and bolt on the underside

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The bending arm is again just flat bar about 5/16" x 1" x 2' long and has an M8 bolt screwed into a tapped hole. The end of this bolt has a hook filed into it to prevent it from slipping off the wire to be bent.

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The pin in the base locates in a hole about 1/2" away from the hook bolt

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And that's it really. 2 pieces of metal, 2 M6 bolts with nuts and 2 M8 bolts. 2 6mm holes and 2 tapped M8 holes.

Depending on the direction you want to bend, the wire is placed between both M6 bolt heads passing the M8 bolt. The hook bolt is adjusted to the size of the wire and is placed on the pin over the base plate.

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The hook bolt engages the wire and traps it against the bending pin in the base plate. The tail end of the wire is trapped against the head of one of the M6 bolts.

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The next photo shows the hook bolt engaging the wire.

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The wire is bent by pulling the handle to the desired angle. If forming coils for undercarriage legs the handle is slightly lifted so that the hook bolt passes over the top of the M6 stops and the wire crosses over itself, travelling up the bending pin as it goes. The only thing to watch when bending coils is that after bending about 270 degrees the hook bolt starts to pull the wire past the bending pin. This is prevented by clamping the wire to the base plate with mole grips. When (if) I get around to making the refined version I'll add a plate under the M6 stops so that they can be tightened down to clamp the wire in place.

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The hook and the bending pin are already showing signs of wear but they are standard M8 bolts and are easy to replace. To prevent damaging the tapped hole to get them out I'd screw them in as deep as they'd go and cut the damaged part of the thread off, then remove them.

As you can see it wouldn't take much to convert the M6 stops to clamps either. Just longer bolts and a thick 1/8 plate with a hole for the M6 bolt and a groove to sit over the wire.

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Posted by john stones 1 on 29/01/2016 09:39:44:

What's going off at the front end I don't see a cowl on there ?

John

Ah! well spotted sir! laugh

My initial idea for the cowl was to cover a dummy radial engine but I really do think the Ballerina suits an in line instead so that idea was scrubbed! The .52 FS leaves little room for a balsa cowl and besides I prefer to be able to completely remove the cowl to get at the engine.

I started the cowl yesterday afternoon by cutting 3 x 6" disks of 50mm pink foam. I then got the start of a shape by positioning one of the disks against the firewall (engine, mount & fuel tank removed) and drawing around the nose. I need to allow hot air to exit the cowl so using a french curve I bowed the sides of the lines out which will form a gap at the rear of the cowl. This was used as the master shape and all 3 pieces were cut the same. I also drew a center datum line on the back, top and bottom of each piece to help line them up.

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From the thrust line marked on the firewall I could also mark the center of where the prop shaft will exit the cowl and using a 2 1/4" spinner I could also mark the front of the cowl. Now I had both ends marked all I had to do was join the two ends together. The 3 pieces were clamped together unglued and a rough shape sketched out on the four sides. A minimum size I have to clear is 45mm from the center line, 70mm back from the front to clear the 90 degree manifold knuckle which determined the curve at the front of the cowl. With the lines sketched out the three pieces were released from the clamp and roughly cut out with the scroll saw.

The pieces were then glued together with aliphatic, clamped up again and left to dry for a couple of hours.

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Once dry I rough shaped the plug with a rasp and then refined the shape with 100g sandpaper, feeling the shape in my hands to keep it even and consistant until I was happy with the profile shape.

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The front was shaped to form a nose ring with a recessed cooling intake below, blending it into a curve that should still allow space for the engine.

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The plug was then wrapped in packing tape to protect the foam against the polyester resin. The packing tape can be shrunk and creases flattened out with a covering iron just like covering film.

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Once covered I cut 3 pieced of heavy glass cloth from HobbyKing, one for the bottom and 2 for the sides & over the top. I can't exactly remember but I think it's 54GSM or similar. The cloth will be applied with polyester resin readily available from Halfords or most motor factors.

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In addition I have P38 filler for fine filling, plastic cups and coffee stirrers for mixing, epoxy brushes for spreading and scissors for cutting the cloth.

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Oh and a plentiful supply of latex gloves. Don't even think of starting without them!

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The plug was laid up yesterday so after hardening today I took these photos of the first layer.

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Tonight after a light skuffing with 80g sandpaper the plug has had another layer of cloth and resin, this time a piece over the nose towards the back and a second piece over the top, down both sides and folded under the base. The cloth is stretchy in one direction of the weave and with a little observation and planning it's possible to get a cross ply layer going. The cloth was pushed and stretched into position with the brush & resin until as many of the folds were removed or minimised and all air pockets eliminated.

The plug is now hardening in the shed ready for sanding and filling tomorrow evening. The shed now smells great! laugh

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Posted by john stones 1 on 02/02/2016 01:25:02:

You can see on my build I've not mentioned/started a cowl, been pondering and getting nowhere, unless cowls removable on mine there's little chance of getting at the lecky motor once/if it's built in. So plenty of pictures please.wink

John

No problem John. yes

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Chris, that's an excellent explanation of the wire bender! Obviously you are a really practical person who understands exactly what is needed for the job and produced a gadget with no frills. As you have gone to the trouble of taking the photos as well I think it deserves a thread of it's own with a suitable title so that in future if anyone searches for 'wire bender' they go straight to the thread.

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I'm with you KC. Superb explanation. I love it. I've had a go at bending the undercarriage and essentially wasted a length of wire. As it turns out, bending a piece of wire with a vice and a hammer isn't as easy as I thought. Looking forward to seeing the finished cowl too. Not gave much thought to mine at the moment.

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My first bender was simply nails in a piece of wood used, ironicly enough on the 2014 Dawn Flyer Mass Build!

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That was OK for the smaller wire sizes but the nails soon became loose and thoughts went towards a metal version!

Peter, I have seen the commercial benders on Ebay and wondered if they'd be better than my rough temporary version! Funny how you "invent" something as a solution to a problem only to discover they're already available to buy! laugh

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Posted by kc on 02/02/2016 11:23:05:

Chris, that's an excellent explanation of the wire bender! Obviously you are a really practical person who understands exactly what is needed for the job and produced a gadget with no frills. As you have gone to the trouble of taking the photos as well I think it deserves a thread of it's own with a suitable title so that in future if anyone searches for 'wire bender' they go straight to the thread.

There's already an excellent article in RCM&E on wire and steel bending, October or November I think?

I have thought about making a couple of bending dogs as well. They seem very effective!

I wouldn't like to post a separate thread on it though. "Drone" flyers might hurt themselves with it! wink laugh

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