Tutorial Advanced - Orta Saint - Hubert G - 1

[Gearup]

Measuring, cutting and fitting struts

With the attach points marked on the fixture for the various struts, now the actual length of the parts can be directly measured.

To do this, use a [air of dividers or compass points to measure between the marked points.IMG1031

Here the centre wire for the vertical gear strut is in place between the lower wing attach point and the lower point, which is the axel height. The wire runs long an after everything is soldered up, it will be the pin for the wing attach and the bottom will be bent 90 degrees outboard to form the wheel axel.

The divider is set for the length of the intersection of the vertical strut and the lower aft gear leg mount point.

Transfer the measurement to the appropriate sized tube and cut it to length. The best way I have found now for cutting small brass tube is with a mini cutoff saw. They are available from harbour fright in the states for the best price. Amazon carries them, but they are more expensive for the same saw.

Second best is a serrated cut off blade fitted to a Dremel tool or a fine modelling pull saw. You get nice clean cuts with these tools.

Using a side cutter or sprue cutters does work well on wire, but tends to crush the tubing closed. If you use them allow for a bit of extra length to file the end flat and open the tube up.

Insert the wire core and cut it a bit long to form a pin for attaching to the model. If it butts to another brass part that will form a soldered joint, cut the wire flush to that end of the tube. IMG1041

Keep cutting and fitting the various parts until you get a good fit in the fixture and solder them together in small groups as you go.

[Gearup]

Soldering brass struts

Solder is simple. Clean, flux, heat, apply solder. How you accomplish the steps will determine the strength and tidiness of the joint. Solder is amazingly strong for the structures used on small models like these.

Once you have settled on the fit of the parts, individually clean the parts joint area with a small piece of scotch-brite or fine sandpaper. This gets rid of oxides and give a bit of tooth for the solder to bind into.

Set the parts into place and if required hold them with self closing tweezers. I use tweezers mounted on metal bases that are used for jewelry or electronic soldering. They are not expensive and I find that they are very useful for modelling in general.

Apply a SMALL amount of flux at the point that will be soldered. The point on the end of a tooth pick is about right. With heat and flux, the solder will flow where the flux is towards the heat. This allows a very small area to be soldered with control. Too much flux is not helpful.

Use the sprue cutter to cut a small piece of fine electronics solder wire. The cut piece will make a match head look like a boulder in comparison. Really small... about the size of a typed letter "O" is a good starting point.

Set the small piece of solder on the joint to be soldered. The flux will provide a bit of stickiness to hold the solder in place.

Use a small soldering iron such as used for electronic projects. Touch the tip to the joint and try to heat both sides of the joint. If done correctly, both parts will heat quickly, the flux will melt off and the solder will suddenly melt and flow into the joint. when this happens remove the solder iron. The pieces will cool quickly. Total time with the sobering iron on the parts is about 2 seconds for such small joints.

Practice will make for more proficient joints. Variations in the first four points will affect the quality of the job.  If it goes bad, the parts can be cleaned and easily reworked again. It would be another entire tutorial on how to solder small parts, but I would recommend a youtube  video that will help. Almost all solder is lead free and works well enough.

www.youtube.com/watch?v=-7D3M3VqCUg

[Gearup]

Completed and Soldered landing gear and struts in fixture

These pictures show the completed struts as they are soldered into the fixture. While on the subject of fixtures, why not call them a jig? The convention I know is that a jig is used to guide the tooling during the manufacturing process. A fixture is used to hold something into alignment during manufacture. Example: Jigs can be used to guide a drill while the part is held in a fixture. The terms get used interchangeably and probably both are valid as long as the intended function is known, but I digress.

The last picture IMG1064 shows the fixture with the struts compared with the CAD drawing for fun. It was fun to see the real world meet the virtual world here.

[lastvautour]

Looks great Fraser.

Lou

[Gearup]

Thanks Lou. In retrospect the "simplicity " of the design did not take into account the fairly complex geometry of the landing gear and wing support.  Several online  pictures of crashed Orta's usually showed the wing askew to the fuselage with the gear collapsed.
 
Perhaps not the best model for a novice, but it is an interesting build. It shows the value of making a fixture separate from the model for more complicated sub assemblies.

Regards
Fraser

[Gearup]

Marking holes under wing for struts

Once the gear components are soldered together in the fixture, the holes for mounting the wing to the upper forward struts can be located and drilled.

Remove the top of the jig. You will now have a flat surface with a centreline to help orient the wing and the tops of the struts will locate the holes. IMG1268

On the wing fixture, measure the distance between the two wing mount holes. I used a calliper to make get the actual dimension. Dividing by 2 will give the center of the wing to set a compass to mark the points on the wing.

If you only have a divider, you can geometrically find the exact center to draw the points. The notation on the picture shows how to bisect the measurement to get the center. Basically mark two points "B-B"on a paper with the divider set to the wing mount point measurement. Connect the dots with a line. Set the compass to any measurement "R" greater than the estimated half way between "B-B". Set the compass on B and strike an arc.Do the same on the other point B. Connect the intersecting arcs with a line "A-A". The crossing point is the exact center of line "B-B". Call it X and set the compass on X to measure "X-B"

Set the compas on the center of the wing, in this case the previously made wing tape line. Position the point 5/16" back from the leading edge and make the two arcs on the wing lower surface. Measure back from the leading edge and this point will be the wing mounting holes. IMG1277 IMG1276

Hold the wing in place on the fixture to check that the pins line up with the marks. IMG1278

If all is good drill a 0.020" hole about 1/8" deep at each point. If you go thru the wing, just fill the holes on the top later. IMG1280

Trim the tops of the wires on the strut to 1/8". The wing should now site nicely on the fixture held by the two struts.IMG1279 IMG1281

The aft wing struts are located fore and aft on the drawing and transferred directly to the wing and drilled as before. IMG1283

[Gearup]

pictures to mark wing mount holes

[Gearup]

Mounting landing gear to fuselage - scribing reference line on cowl

Before we can mount the gear, the mounting holes need to be located on the fuselage. To get a good reference point on the fuselage, the firewall / aft cowl line was marked on the fuselage. I used a strip of thin brass to provide an edge to draw the line on the fuselage.  A single edge razor blade is used to cut the line into the model. For a surface like this. I simply place the blade on the line and apply pressure to the blade while I roll the blade over the line. I don't drag it as it is not as controlled and may also tear the paint finish. IMG1286 IMG1288 IMG1289

[Gearup]

Mounting landing gear to fuselage

Use the divider to locate the aft strut mount hole at the bottom of the fuselage side aft of the cowl line. Drill the .020" hole at this point on both sides. IMG1291

Remove the gear from the fixture. Hopefully there is a short .020" wire pine on the aft lower strut, upper end and the aft upper strut lower end. Insert the lower strut end into the hole on the fuselage. The lower forward strut is located at the cowl line bottom edge. There is no pin here and the strut can be manoeuvred into position over the cowl line. IMG1296 

With the vertical strut vertical to the fuselage side, mark the upper aft mount point and drill. Now there are two pinned points on the gear and the forward struts are located. Again the those struts are not pinned, but will be glued to the fuselage side. You could make them pinned, but it was more difficult to position and drill with them if there is a small amount of distortion in the assembly. IMG1297

Both gear assemblies can be held in place to see how they fit. I also made a small fixture of the wing center section to hold the upper struts at the correct location while the fit was checked. The struts were then glues into place at the four attach points with thicker CA glue. IMG1295 IMG1298

Note in this picture the landing gear axels are still straight down and can be bent outward 90 degrees to form the axels. IMG1299

[Gearup]

Making Seats

So after all the work on the landing gear, I did take a break for awhile...

But I did make a couple of cockpit seats out of card stock and CA glue IMG 1410

I I drew a pattern based on a wicker seat used in the aircraft of the era. It is simply heavy card paper cut and shaped around a pencil to curve it.  CA glue was used to hole it together and then it was covered in CA to essentially plasticize it. The back seat is slightly narrower than the forward seat which holds two people. After they were painted, I mounted the aft seat on a thin block to raise it as the cockpit was a bit too deep. They were glued into the cockpits after the model was painted. IMG1438 IMG2228

[Gearup]

Marking and Making Wing Struts
Meanwhile, after completing the gear and wing strut....ha....I was looking at actual aircraft pictures again and discovered I had not built the actual struts for the darn wing. The three view I was using did not show two forward struts that tie into the fuselage and at the top of the gear strut.  They are hidden from view due to the structure and geometry of the gear assemblies.......HA....

I had the aft strut locations ok from the drawings but the forward wing strut was hidden. The lower end of the strut is centred between the lower gear in line with the vertical strut. IMG1420 IMG1421

Measure the length between the fuselage point and the inside angle of the joint on the gear upper end. Make a streamlined brass strut as was described before, but only put a .020" wire in the one (lower) end. Glue it into the hole and to the strut joint at the top.IMG1428

The aft strut needs to be measured with the wing temporarily mounted to the aircraft.

With the fuselage upside down on the bench and with the wing in place, level the fuselage with shims under the tail so the strip on the side of the fuselage is parallel to the surface. IMG1432

Use dividers to measure from the lower strut point on the fuselage side (forgot to mention that before that it was located and drilled...my bad) to the mount holes on the wing. IMG1434

Cut and form the aft strut with pins on each end. Glue the aft struts into place. Yes, the struts do have a forward sweep on them that looks crooked compared to the vertical struts. Photos do however confirm this skew on the aircraft. Probably the structure in the aircraft did not line up where it was needed on the wings. Hey, the whole landing gear design is a bit weird too.....
IMG1436  IMG1437

Do not glue the aft struts into place yet as it will make it easier to handle the model further on.

[lastvautour]

Not only accuracy, but strength. Excellent approach.

Lou

[Gearup]

Engine cylinders intro

The aircraft is powered by a Belgian designed 100 hp engine, the "RENARD".

It is a five cylinder radial with some very unusual configurations. Photos on line show several different combinations of valve push rods, exhaust stubs and exhaust collectors.

For this aircraft the most unusual thing is the valve operating push rods and cylinder head. The head has a valve housing for both intake and exhaust in tandem oriented fore and aft on the top. The intake is aft and the exhaust is forward. To operate the valves the push rods are also aligned vertically fore and aft at the front of the cylinder. The rod closest to the cylinder operated the exhaust valve via rocker arm. The intake push rod was forward of the exhaust and because of the inline valves, it operated a split parallel set of rockers on a common shaft to the exhaust valve. Therefore you had the exhaust rocker sitting between the two intake rockers on either side on the same shaft.

Each cylinder had a duel exhaust stack. This engine simply had two short stacks per cylinder like a set of horns. On some engines the exhaust stacks were connected via a collector ring at the front and directed to a long exhaust pipe. 

To duplicate the split rockers would be very difficult at 1:48 scale using wood and wire, so I simplified the cylinders for this model. As well only the cylinders stick out of the rather well streamlined front of the aircraft, so the engine case does not need to be modelled.

The illustration of the simplified cylinder assembly was done on Sketchup to illustrate the completed part. Following will be the pictures and details on construction. Oh yes, the cylinders are only 1/8"x 5/16".

Required materials: 1/8" dowel, 0.020" brass wire. 0.032 brass wire.

[Gearup]

Engine cylinder construction - cylinder and exhaust
Cylinder barrel and head

Make a fixture to hold the dowel. I had a piece of 1/2" thick plastic cutting board. Ikea boards are a great source of plastic for projects.  Wood works well too.

Drill a 1/8" hole in the fixture. I then held the fixture in a small bench vise when woking on the part.
Insert the dowel to protrude 1/16' from the fixture. Mark a centreline on the top. IMG1172

Use a razor saw to cut a 1/32 deep notch either side of the line  1/16" down from the top.  A razor blade is the used to split the pieces away from the part leaving the central valve block attached. IMG1174 IMG1175

Drill a 0.032" (1/32") hole through the valve block. This hole will be for the exhaust pipe.

Make the exhaust pipe from.032" brass rod. I cut mine to 3/8" and bent the shallow "V" at the middle using pliers.IMG1171

Insert the wire pipe into the hole. I pulled the dowel down to trap the part in the correct orientation as shown then used CA to glue it in place. IMG1179

Paint the part in the fixure. I used grey head, black barrel and black valve block with black exhaust pipes. IMG1161

Cut the dowel about 1/2" past the side of the fixture to give you a 1" working length. Repeat for the remaining 4 cylinders. Ummm, better make ten to allow for dropping and loss....

You will find it easier to perform each individual step on the batch of parts at the same time.

[Gearup]

Engine cylinder construction  - push rods/ rockers

Again, here is a test of you soldering skill. The rods are made from two pieces of 0.020" wire soldered together. The challenge is keeping the parts aligned for soldering and handling such little bits. IMG1142

"L" part = forward (intake) push rod and rocker arms
"I" part = aft (exhaust) push rod
Start with cleaning the wire with fine sandpaper then bend and cut the "L" shape. Each leg is 1/8" long measured on the inside of the bend. Bend a piece of wire 90 degrees then measure and cut the piece to length. The straight "I" rod is cut 1/8" long.
Now the "I" part is soldered to the "L" part with a small parallel gap between the two. The fixture for this is a piece of double sided tape on a sheet of paper! The tape holds the parts into alignment and does not burn up if the heat is applied to the brass. Just don't press hard ...

Putting the parts onto the tape is a fun job. If you try and use tweezers they just seem to shoot the part across the room as you grip them. I found the solution in stick wax jewellers pencils!
These are special wax pencils I bought on Amazon.They are also used in applying false finger nails. They have just the right tack to pick up and hold small parts yet release the part with a little roll of the pencil. If the tip stops working, just resharpen it.

Use the tip to place the"L" part on the tape. Now place the "I" part next to the "L" part inside the leg and with a small gap. The picture shows the "I" part is short, but the "L" part was trimmed later.IMG1150

Cut a small piece of solder. Really small. Too much will wick down between the two parts. IMG1149 Apply a small dab of flux on the joint. Too much and the solder will wick again.

Pick up the tiny solder particle with the pencil and place it on top of the joint IMG1150.

Heat the solder iron and when ready, lightly touch the joint. The heat transfer should be fast and the solder will flow into the joint.

After the part is cool, tune up the joint with sandpaper and paint them as desired.IMG1151

Here is the production run of eight parts on a dime.IMG1160