WIRE HANGER RETRACTS - 2 - IMPROVED STABILITY

And like this:

The same geometry applies tho the main gear except that the wheel struts are at 90 degrees to the base line (swappable) instead of 110 degrees.

Here is a drawing of the bends for the nose gear wire:

You should check the angle using the angle sheet below.

You should make a sheet up with all of the angles that you will use for the build.  If you do not have a protractor you can print one from the internet.  Just search "protractor printable".  It should look something like this:

You can check all bends including the 90 degree ones against this.

UPDATE:  Here is a scan of the angle drawing.  It will not print ful sized from this article.  You can save it as a document and then print it.

The pivot wires should look like one piece when sighted from the end.  

 This picture is from another build and out of sequence but you should have 2 1/4" or just a little over from iside to inside of the last two bends.

You have to put the plastic triangles on now before you make the bends that bring the two legs together.  Slide one small then one big triangle on each side: 

Next hold the pliers right against the last bend and bend both sides in toward each other so they cross.  The measurement to the intersection from the last 90 on each side should be 3 1/4" for cam clearance.  Take your time and make small adjustments untill they are just right when at rest.  Make sure both sides are the same (for centering). Like so:

 Then grip the intersection very firmly with side cutters and twist the two loose ends as tightly as you can by hand for two full turns.  Then grip the twist with a second pair of pliers and tighten the twist firmly. 

Next, straighten the longer leg in line with the twist and bend the shorter one at right angles to the twist.  Then twist the short one around the longer one by hand or with pliers making two full tight turns:

Trim the end off as close as possible and use side cutters to "walk" the loose end in tight.

You will most likely have to do some straightening after the twisting is done.  Straighten the twist and remaining loose end until everything looks centered and the piece will lay reasonably flat on the table.

Next grip just below the twist with side cutters or the widest part of the needle nose pliers and make a 45 degree bend to one side.  At the other side of the pliers bend it back 45 degrees in the original direction. Like so::

 Then measure 1 1/4 (or 1/4 " bigger than the radius of the wheels you plan to use) and make the last 90 degree bend.  Measure from the last bend 1 1/2" and trim off the excess.  This is the axel and it should be parallel to the pivot wire in both directions.  Like this (picture out of sequence):

The finished piece should look like this:

My piece ended up a little longer than the drawing.  That is due to the length of the twist.  It does not matter.  Just make the main gear a little longer to compensate.  

Note:  To determine the length of the legs on the main gear measure the length of the nose gear and mark it on the 110 degree line on the angle paper (extend line if needed).  Then measure the distance to the base line at 90 degrees.  Measure up the same distance 90 degrees from the base line and put a mark on the 45 degree line (extend if needed).  This should be the length of the main gear legs.  My nose gear length was 5 3/4". The height at the 110 angle was 5 3/8".  That made the main gear length measured along the 45 degree angle 7 1/2". 

Next we will make the transfer cam.  It is shown on the right  side of the drawing above.

TRANSFER CAM:

Use the remaining short piece left over from the first wire.  First make the small "hook" 90 degree bend.  It should be  3/16" to 1/4" max.   Then measure 3/8" from the inside of the hook.  Set your pliers on the mark and make the second 90 degree bend in the same direction foming a "U".  Then measure 3/8 " from the inside of that bend and make another 90 degree bend back in the opposite direction.  Again, measure 3/8" from the inside of the 3rd bend and make one more 90 degree bend in the opposite direction. The last bend should be rotated 20 degrees away from you as shown in the picture below (or you can bend it later).   It should look like this:

Make sure all of the bends are good 90s.   The one pictured needs a little straightening to make everything good.

Next, measure 3/4" from the last bend and make one more 90 degree bend in the opposite direction.  Then slip the loose end through the second hole in the link that is already on the first piece you made.  Make sure the link is oriented the way it is shown below.  The cam wire on the first piece should be "away".  The rest of this piece will have to be made while it is attached.  

Again use the narrow end of the needle nose pliers to make the 90 degree bend for the 5/8 " link position:

Then measure 1" and 3/4" and make the last two 90 degree bends as shown in the photos.  Each measurement is made after the previous bend is made.  Cut off the excess leaving the 3/16 hook on the end.

Here is a picture of ther cam showing all  the bends in the right directions.  The piece can be made flat and then twisted to get the angles shown but it is probably easier to make the approximate angles as the bends are done,  Some fine tuning of the 90s will probably have to be done after any twisting.

 Everything needs to be double checked for square, parallel to the pivot wire and allignment of the pivot wire (looking like one wire like before).  The pivot wires for both parts should allign well, like this:.

Each pivot wire should lay flat in the table through it's full rotation.  It should look like one wire when viewed from the end.  You should look from both ends and straighten anything that does not line up.  You can also check with a straight edge.

The finished assembly should look like this:

Set it aside while you make the main gear.

MAIN GEAR:

The main gear is mostly the same as the nose gear.  The initial bends for the rear strut are the same up to the point of the third pair of 90s.  The third pair of bends are 45 degree angles outward instead of 90s and they are made at 55 degrees to the angle of the center lug.  This is because the main gear is at 90 degrees to the pod instead of 110 but the lug is the same angle as before.   

Start out by cutting a 24" piece from the second straightened hanger. The 5/8" lug is in the center this time because both legs are the same length.  Mark the center and then 1/4" each way.  Make the first 90 degree bend on one of the outer marks. Slide the second link on the longer side and then make the second 90 degree bend for the lug same as for the nose gear. It should measure 5/8" wide. Measure 1 1/8" on each side and make two 90 degree bends outward in opposite directions.  Allign these wires by sight or straighrt edge as before. Measure 3/4" on each side and make the third pair of bends at 45 degrees. These bends are rotated 55 degrees from the lug.  It should look like this:    

Carefully double check the 45s with a triangle or the 45 degree angle drawn on the paper.  You should also check the 55 degree offset between the lug and the struts.  If the legs are laid flat the lug should be up 55 degrees.

Repeat the steps above for making and attaching the second transfer cam. It is identical to the one for the nose gear.

Main Gear Brace:

Due to the length of the main gear and the relative weakness of the hanger wire (as compared to music wire) the main gear needs to be braced.  This is done by adding a wire hanger cross member at about half of the height. first measure down 3" on each leg from the 45 degree bend at the pivot.  Then measure across the two marks. It should be about 6 3/8".  Add 2" and cut a piece of wire that length.  Measure in and mark 1" from each end.  Make two 45 degree bends in the same direction at the marks.  The piece should lay flat when you are done.  It should fit between the two marks like so:

You will also need 4 pieces of heat shrink tubing 1" long.

Put the anchoring triangles on before attaching the brace.

The cross member is first hot glued into place.  Just lay a generous bead along both sides of each joint. Like so:

Then slip one of the pieces of heat shrink tubing over the glue and heat it well.  Slip a second over and heat again.  The glue will be reheated and will squeeze out both ends.  You can wipe away any excess while it is hot.  You should adjust the positions of the wires before/as the glue sets.  Do the same to the other side.

After the brace is installer it needs to have a couple of bends made so it will clear the push rods.  Measure in 2" on each side from the 45 degree bends and make marks.  Bend on these marks to make a 5/8" offset on the same side as the lug.  Lay it flat and use a 5/8" piece cut from scrap to gage.  The offset including the thickness of the heat shrink should be 5/8".  Like this:

Note: This picture does not show the triangles in place as they should be at this point.  I had to unglue / reglue one side to put them on.  

The brace bending will pull the legs in a little from the 45 degeree position but that is OK.  You may need to adjust these bends later to get the clearange needed for the push rods.

After the braces are complete measure and mark the main gear leg length determined above and make the two 45 degree bends for the axels.  My length was 7 1/2".  Yours may be a little different.  Make the two bends opposite each other and adjust till they are in line with each other as described above (sight and /or straight edge).

Now you are ready to install.  

LOCATION - LOCATION - LOCATION:

First you have to determine the proper locations for your model.  My example is one of my flying wings from the related article ("One Sheet Two Sheet No Waste Flying Wings") below.  Since it is a flying wing with a pusher configuration the nose gear is at what would normally be the back end of the swappable pod.  You will notice that I have closed the angled front by adding a panel that is taped and hot glued on.  The nose gear will go as close to the front as possible.  Leaving enough room for mounting I am using 3/4" back from the bottom front edge.  Measure back 3/4" and draw a line across using a trianglee or square. Measure back another 1/8" and draw a second line across.  This is the position of the pivot wire of the nose gear.  Like this:

The main gear on either a tractor (conventional) set-up or a pusher should be just far enough behind the CG to accomplish ground stability.  You should be able to lift the nose 15 or 20 degrees before the balance causes the tail to drop.  With a 6" gear height that places the main gear 1 1/2" to 2" behind the CG.  You cannot go too far or the elevetor will not have enough force to cause rotation.  

For take-off to be accomplished the elevator has be be able to push the tail down enough to create an effective angle of attack so the wing produces enough lift to overcome the weight of the model.  This position is more critical on a flying wing because the elevons are just at the back of the wing instead of on a long tail boom.  For this model I started at 1" behind the CG. That is only 10 degrees back.   I can always bend the gear back to increase that if needed.

For a conventional tractor layout the nose gear should be at what would be the fire wall in a real plane or about half way between the wing leading edge and the nose.  The main gear should be about 1 1/2" behind the CG.  If there is a tendancy to drop the tail, bend the gear another 1/2' back.  If you have trouble rotating bend 1/2" forward.

For this model we are using 1" behind the CG.  We have to install the swappable pod on the model and transfer the CG to it.  Use a straight edge to mark the CG on the wing at both sides of the pod. Use a triangle (or similar squaring device)  to transfer it to the bottom of the pod.  Measure back 1" and draw a square line across.  Measure another 1/8" back and draw a second line across.   This is the position of the pivot wire for the main gear.  The strut will be at 90 degrees to the fuselage so this is also the center of wheel position. 

GEAR INSTALLATION:

 Start by holding the nose gear strut centered on the layout.  Then use a hobbyknife to mark the anchor positions on each side of the lug.  These should be pretty tight to the sides of the lug since they control the sidewards position of the gear.  We don't want it moving sideways on us.

Then use a straight edge to extend the cuts to about 1/2" each side of the layout lines.  

Use the tip of a cheap mechanical pencil to open up the cut to make a slot for the anchor and glue. 

Dry fit:

Insert the smaller triangles and adjust the pivot wire on the layout accurately.  Then fill each end of each slot with glue till it starts to squeeze out.  Squeegee off the excess.

Slide the larger triangles down and glue them to the sides of the fuselage.  

You should use enough hot glue so that the back of the anchor is mostly covered with little of no squeezing out on the sides.

Hold the gear in the proper deployed position (make a 110 degree pitch block if necessary) and mark the position of the cam frame.  The nose strut should be at the proper angle and the cam lug and link should be in a straight line.  This will be the gear down and locked position.  Mark both sides of the wire.  Use a square and draw both lines across.  Mark and install the small and larger plastic anchor triangles as described above. 

Cut a small 1/8 plywood wedge block sized to allow the cam and link to rotate just past the straight line position.  Glue it on.   This will allow the assembly to "lock" at the full extension of the servo.

MAIN GEAR INSTALLATION:

Repeat the exact same procedure for the main gear.  The only differences will be that the main gear legs are bent out at 45 degrees instead of 90 and the down and locked position will be at 90 degrees to the base line (swappable face) instead of 110 so the lug angle is 55 degrees instead of 35.

Mark the small anchors for the mian gear pivot:

Extend the cuts:

Open the slots:

Main gear anchors glued and marking for the cam.

Checking completed main gear installation for square.  This is a tilted a little back from 90 degrees which is OK.   

INSTALLING SERVO AND SERVO ARM:

The servo gear should be centered between the short lugs on the cam pivots:

Mark both sides of the servo and then complete the layout by standing the servo up and tracing it at the center of the swappable.  Clean the tracing up by checking measurements and squareness with a ruler and square:

Make minor adjustments if needed.  Cut it out and install the servo from inside the swappable.  I added a couple of plastic triangles to give the servo a wider base.  This added greatly to the stiffness:

Here is a picture of the completed servo / linkage installation:

The round servo arm is an old one from a full sized Futaba servo with the center drilled out and hot glued over the round one that came with the 10 g servo. It is 1 3/8" in diameter and should be a little bigger to get enough throw.  I will change it to a plastic bottle cap that is at least 1 1/2".  

Connect the servo and set it to the down and locked position (all the way counter clockwise).  Then drill two 1/16" holes at 10:30 and 4:30.or about the 45 degree positions.  Mark each linkage at the holes and make a modified "Z" bend.  You will have to take the wheel off to connect the linkages.  You will probably have to slip one of the linkages past the 90 degree bend to make the second connection so the hot glue stops should be done after. 

Adjust hole positions if you are getting too much or too little throw or need to adjust the balance brtween nose and main gear.  When you are satisfied with everything add the hot glue stops on each side of the linkages. 

Test the throws and adjust the hole position if needed till you get the action needed.My radio also has a throw adjustment that will go to 120%.  That may give the additional stroke on the retracted position that I need.  If not I will install a larger wheel made from a plastic bottle cap with the sides cut off.

LINKAGES:

The linkage is made from flag wire.  The flag wire is pretty stiff  so this will take some effort. The loop at cam log is connected first.  You have to make an open full loop then slip it over the cam lug. Then snug it up both directions.  It should be snug enough not to wiggle but loose enough to allow free pivot.

Make the open eye with needle nose pliers.

 Slip the loop over the short cam lug.  

First close the open loop till the two sides touch.

Then snug the loop around the lug wire till it is snug but still moves freely.  You may have to go back and forth between the two squeezing positions to get it just right.

Then make the "V" bends.  First close the main gear to see where the brace hits.  Mark that position on the linkage and make the first "V" bend a little after the mark.  After the "V" bends are complete mark the linkages at the holes in the servo wheel and make the connections as described above.  

Hook everything up and check the range of movement.  Ideally the main wheels should touch the under side of the wing and the nose gear should stop just short of hitting other parts of the gear.

Check the height of the nose gear. 

 Checking the height of the main gear.  If should be the same as the nose gear.

THE COMPLETED INSTALLATION:

The servo is postioined so the gear is in the middle between the two cams.  This is the largest servo wheel I had in my box from my nitro days.  The center was drilled out then it is hot glued to the smaller one that came with the 10 g servo.  This is actually a little too small so that the gear does not close as tightly as it should. I have some adjustment available in my radio settings but if that is not enough I am going to get a plastic pill bottle lid that is a little larger and re-do it. 

UPDATE:

I have worked out a solution to the problem of not enough throw.  The largest servo wheel I had was 1 3/8" in diameter.  That allowed a push rod attachment at 5/8" maximum from the servo pivot.  I have added two plastic triangles to the servo wheel effectively increasing it's diameter to 1 7/8".  The push rods are now at 13/16 and the wheels almost touch the bottoms of the wings.  If using a bottle cap I would look for one 2" in diameter.

 One more additional important note:  THE SERVO MUST BE CONTROLLED BY A DIAL rather that a switch.  The abrupt motion forced by the switch will overheat the servo.  I have a fried one to prove it.  It really snapped up and down two or three times and then melted.

COMPLETION & TESTING: 

Well, that is it for the retracts.  I have to comlpete the radio and motor installations and then fine tune the main gear for ground stability.  Then test flight.

I have to test the wing as well as the retracts. I have been weather locked since starting with these FT style builds at X-Mas time.  I am eager to get out and see how everything works.

Please comment and feel free to offer any useful suggestions.  This article is the result of reader comments on a previous article.  Hopefully a significant improvement has resulted.

Please look at my other articles for a lot of related information.

Happy flying!