Rubber Band Power

[mbauer]

First thing that will not be to scale shape is the propeller. It will be the average of 5-different 3-view drawings. Some were 15" some were 18.5", working up an ave. of 17.25inch.

But first a little history from last century till now: Can pass by if you want>
When I was 8 or 9 years old, both my Grandpas gave me control line models for Christmas that year. Grandpa Ed gave me a Cox .020 Green Pitts Special, it cranked and flew fantastic.

Grandpa Joe Gave me a Boeing P26 Peashooter made by Cox with an .049 engine. It only started once! No matter how much I tried, it would not start. I knew nothing about Glow Plugs and how they worked.

All I knew was hook the battery and spin the prop, it should start just like the little green one.

Well one day had some friends over to launch rockets and fly the control line Pitts.

Decided to try and crank the .049 again.

Guess what? it fired right up first spin of the prop!

Well the spinning prop totally caught me by surprise and left me with a scar to this day! Got my left thumb just below the main big knuckle! Please note scars around middle knuckle are from cop car/motorcycle accident, not to be confused with the propeller history:


Grandpa Joe was special: He owned a Cessna 182 that had Robertson Stall to fly into the Idaho back country. Anything, anytime he talked about flying, no problem with me falling asleep!

Or invited to fly the next day into the Flying B Ranch on the Middle Fork of the Salmon River?

No sleep for me.

He learned not ask about the trip until the day before, mother's request...4am alarm clock, 5am take-off. Usually meant work on the end of a shovel, but horses to ride and fish to catch and most important payment-over an hour each way to fly in.

When he gave me the model he told me about his favorite fighter he admired as a young adult in the 30's. That is why he bought me the Boeing Peashooter. Now you know why it gets high end printing! Looking around found a couple of gold colored fuselages. Perfect to show off the Metallic Photo Paper. The one he gave me was a Red, White, Blue colored one, which there are several.

Back to work:

Looking around it was possible to buy a two bladed 17" diameter propeller that was rough cut from balsa wood. Only final sanding needed done.

It will shatter instantly on contact with almost any hard object. Cost is over $20 per blank.

After several on-line searches and finding some interesting photos and reading material, decided to make my own propeller.

It will be made using photo paper! Why paper?

It won't shatter if it hits a hard object. Easy to cut to proper shape. Only issue is getting the correct under camber or curve.

Thinking that it will work to get the under camber by:
After cutting both sides of each blade out, verifying good dry fit for accuracy, super glue will be used to fuse the blades back to back.

Before the super glue has a chance to set-

A plastic wrap will be wrapped around a 2" paper roll tube (done well before super gluing).

The blade parts will be wrapped at an angle on top of the first layer of plastic wrap. The blade part will be tightly wrapped to the tube using more plastic wrap to hold it "tight" to the tube while the 60-second super glue cures for the next 4-hours minimum.

Hoping this treatment will give it the correct curve, by pre-stressing the blade this way, should make it incredibly Strong and hopefully will maintain its shape at the 2000 RPM it rotates at.

Rubber bands rotate at 2000 RPM? What??

Well, not sure, Have read several different places where 1000 windings are done in 30-seconds. That count is by an actual counter they use at the competitions.

You can get more windings by lengthening the rubber bands (what I do), by adding strands (what I do), and more time or less time by using a different pitch propeller, gearing, a bigger blade also slows down the RPMs.

To make a propeller and get it accurate you need a prop "Pitch Gauge" to verify both sides are the same.

Here is my home made tool after finding something similar on-line at endlessLift – the wonder of simple aviation.

My version cost way less than any you can buy, commercial ones start at $15 for electronic versions to $345 for adjustable mechanical ones. Old Scrap wood from the garage, $1.28 protractor. Screws were a major cost of the project. Electricty had to be in the the 2-3cent range for the drill press that was used to drill the holes

Here are some photos: Easy to see prop pitch at top of wood edge, harder to see prop in this photo-it is a 12" long plastic one:

Top View-Regular mechanic socket used for weight to hold prop down. Holes are 1/8" apart:

Here is a side view, easy to see wood used- ends are pine wood sized 8" wide x 3/4" Thick x 7" long. 2x4 is 14" long with holes drilled down the center. Don't need a ruler to determine length, just that blade falls at mid-length location onto the protractor edge-as shown with 12" blade. Clearly shown is 3/32" spacer under prop for proper clearance for the tool to work:


Last look for now: Soon you will see how it works to make a working propeller!:


Mike

[birder]

That P-38 looks great, Mike, cool projects. I see your are dealing with complex problems, the prop is impressive ..

[mbauer]

Photos just don't catch what this "ink" looks like. Have the tailcone printed, and then spray sealed with the clear gloss acrylic.

It is laying on top of my printer, each time I go past it, have to admire how it looks. It looks like gold, not ink.

The metal flake look is there. Any light reflects off of it. The whole print sparkles, you can see the sparkles in the following two photos. Notice how light the overall print looks like, well those are the sparkles the camera is not doing a good job of catching.

Kind'a makes the surface look foggy, the sparkles are easiest to see near the Gorrila Glue tube, just to the left you can see the thousands of sparkles:

On the very bottom edge of the photo paper, you can see a white strip of regular bond paper I have to glue onto the silver photo paper. It is the only way it will feed through my printer. Without the strip, my printer says it can't detect the sheet! Tried several things before gluing a strip to the starting edge of the sheet.

Awesome looking photo paper, wish I had bought a couple of more rolls!

Okay, just figured a way to show what the ink really looks like, check these two photos. I printed several different swatches to test for a color combination for this project.

The first print was on regular cardstock, a second was on the metallic paper. On top of the big print was placed the cardstock test print. This gold color is the "G2" color. Note the difference between cardstock and the metallic photo paper? Big time difference!



These color swatch test prints are used to narrow down the colors for each project I do. The first step is to go on-line searching for different colors. Many sites have the color code numbers for all the different ways to show that particular color. I just get the RGB codes for that color, enter them into AutoCAD as a new layer with the new color. You can see the many different hues of gold that I have added to the colors available in AutoCAD. The silver looking are actually the codes for "chrome" color, silver and gray, stainless steel all look different!.

For this project, I have a photo of the engine from a museum. It was cleaned up and will printed for the model. The background was of many other airplanes on display. Cleaned it up by adding a color to the background to hide the objects. Wanted something lite colored so the dark engine doesn't disappear in a dark mass. The color ended up using is a "flesh" color. Looking forward to see what it looks like.

Mike

[mbauer]

Originally Posted by birder

That P-38 looks great, Mike, cool projects. I see your are dealing with complex problems, the prop is impressive ..

Hi Glen,

Thank you.

Really enjoy watching your projects. Fantastic realistic looking builds!

Can only image what one of your colorful projects would look like made on this metallic paper.

Mike

[mbauer]

Photo of Engine after cleaning it up. Used a very light "flesh" color so that the engine wouldn't be lost in a dark blob.

Note: I could not find a very good photo of the back of the engine, so I mirrored the front to create a front and back view.

Spent 4-hours in AutoCAD adjusting the image to only show the engine and not the background. Then a "hatch" was added. Hatch is basically how you paint in AutoCAD.

The 4-hours were spent changing the shape of the photo. AutoCAD has a command called imageadjust. It allows you to "crop" the photo for your needs.

I very carefully created the new photo outline by slowly following the contours of the engine.

Should have thought ahead and added the Pratt & Whitney logo the the engine stand at the bottom. It almost would camouflage the engine stand and make it look like the oil sump that is behind it (engine stand is hiding the sump).


Before creating new photo outline to hide background:


After cleaning up:





Working on this project, trying to get two SR71 Habu's done for some friends, rebuilding Christmas stuff that was damaged, in other words slow progress on the P26. I do have everything printed and several items rough cut out.

Mike

[mbauer]

Found my old invoice for the photo paper I'm using. $488 included shipping. 24"x100ft roll.

That is 33.33 sheets sized 24x36 = $14.79 per sheet.

It is extremely hard to work with.

Want to score for a fold line? Every tool that you try to use, catches and will remove the ink, the shiny stuff right down to white paper underneath. Really light pressure and go slow & smooth, seems to work.

Glue? Tried Aleenes, no go, tried gel superglue, messy and no stick. Found some Loctite liquid super glue that is working.

Photo paper is 270gsm. Hard to fold, easy to cut/tear. Try to cut fine detail stuff, better have some sunglasses.

The light reflecting off this stuff is blinding if the light hits it just right.

Photos of the printed parts below. The "decals" have been glued into position for these photos (all the parts with white on them).

Some parts laid out on floor:


Wings view:


Horizontal Stabilizer & Elevator-Note upper right there is a fold line (dashed) that when scored had too much pressure on the embosser-you can see how it removed ink down to the white layers underneath, also note that along the bottom edge there is a white strip of bond paper that glued to the front edge so it would feed through my printer.You can also see how the ink "bled" after printing , before sealing with spray. Moisture in the Air really effects the paper in a bad way, must seal within a couple of hours or the ink bleeds. You can see this on the center edge of the line that is all fuzzy to left:


Closeup of 94th Pursuit Squadron Insignia:


SHINY:


Vertical Stabilizer and Rudder:


Fuselage View:



Skull and Cross Bones that I drew and printed with the model-had some spare places that I could print different things to see how they look on this expensive photo paper:


Will get more work done tomorrow after day job is done.

Mike

[mbauer]

A few update photos and a story to tell.

This is not the easiest of papers to use.

On top of the "silver metal flake" layer there is a membrane that allows the ink to take. Within a couple of hours you need to seal with some spray or the membrane soaks up the water in the air. This causes the ink to bleed in all directions.

When cutting the parts out, any light reflects. This light begins to hurt the eyes as to start causing focus problems and it feels like I've been welding without a hood after several hours of cutting. Sunglasses for today's cutting....

The biggest problem so far? The long fuselage tailcone with the super glued on decals are not user friendly to pre-rolling. They are trying to pop off instead of curl.


When scoring fold lines, the scoring tool is removing the layers of clear gloss, membrane and silver flakes, right down to the white paper underneath.

Liquid super glue is the only stuff that even remotely acts like it might glue this stuff. Bought some Zip Dry to try next-hoping the reviews here mean it will work!

After using two full cans of gloss spray, extra 24oz almost mean this will be only a display model, hoping that isn't the case but, an electric motor probably will get it air borne, not sure about rubber bands.

The paper is easy to cut, like the knife just glides along. However any sharp angles, meaning between triangle glue tabs, the paper has a tear point and it will tear. Had to superglue a few layers back together. Now those areas are hard to shape and deal with.

Boy is this "fun".

Well, after all my whining here are some progress photos.

Shiny Tail Feather look, the first portion of the horizontal stabilizer will have some 3/32" [2.35mm] plywood sandwiched between the photo paper. This will allow easy bending of the elevator as it will be just paper and bendable:


Another angle on the tail feathers. The rudder just like the elevator will be bendable, with 3/32" plywood on the front half:


A shiny wing and main fuselage-was going to do a cockpit, found a really awesome photo of a control panel. Then reality hit, there will be a huge rubber band tube going through the center of the model, not a good thing for a cockpit...:



Yardstick to show approx. size:



Only photo showing (blurry) front cowling progress-all others the paint was bleached out by the lights:


Shiny items and a final view for today:




More to follow!

Mike

[mbauer]

Problems are showing up on everything. A big new problem?

To power this rubber bands means I'll be traveling into uncharted territory:
Plan to use 8-strands of rubber band 1/4" wide [6.3mm]. Can't find where anybody has used this many.

Found an on-line calculator. 8-strands at my preferred length means over 25lbs of force stored up. This is incredibly dangerous territory!

I'm using a paper tube so far, with great results, however, it has not been tested to destruction. Really don't want to find out that it won't work in the model. After how much "fun" it is forming this 260gsm photo paper into shape.

Decided it is time to start some kind of testing program.

PPE for paper model making has to be a first for full body protection. Have a really heavy duty leather welding jacket, motor cycle helmet, and heavy welding gloves upper body. Leather motorcycle chaps for legs.

Purchased a rubber band winder for $125 with counter so that I can measure the turns.

Will be making my own strain gauge as the ones available don't record high enough for my purpose. Fish scale will be rigged to record energy present.

Finally a couple of Big surprises are in store once this model is done. One might work, the other will be made to work, even if it doesn't want too. It has taken over 40-hours of extra drawing for both of these "mods". Not saying anything other than that for now, in case they both fall flat.

A friend of mine has a local welding shop. He runs a really interesting crew, one of which is my son, working a Christmas present for the whole crew, it has something to do with my Skull and Cross Bone drawing.

Note I added a "leather eye patch" to the drawing. Should look ok on some T-Shirts!





Hoping everyone is having a great weekend!

Mike

[mbauer]

Have heard several mechanics talk about the Pratt & Whitney WASP R1340 nine cylinder radial engine.

From the very first it was easy to see that this engine was special.

First one built was in the mid 1920's.

Over 34,966 were produced from the 1920's through end of production early 1960's.

Th engine that powered a nation at War could be a name that could fit as well.

It powered many famous pilots throughout the Golden Age of Aviation.

It has been used for the basis of all Pratt & Whitney radial engine designs.

Here are some interesting facts:

The Pratt & Whitney R-1340 Wasp is an aircraft engine of the reciprocating type that was widely used in American aircraft from the 1920s onward. It was the Pratt & Whitney aircraft company's first engine, and the first of the famed Wasp series. It was a single-row, nine-cylinder, air-cooled, radial design, and displaced 1,344 cubic inches (22 L); bore and stroke were both 5.75 in (146 mm).

In 2016, it received designation as a Historic Engineering Landmark from the American Society of Mechanical Engineers.

The Pratt & Whitney R-1340 Wasp was a 9 cylinder, radial engine with horsepower ranging from 410 hp to 600 hp.

It was used in a range of aircraft that included the North American Boeing P-26. Jimmy Doolittle used the Wasp to set records in his Gee Bee Racer.

The Wasp was the first engine produced by Pratt & Whitney and it was completed December 24, 1925 at the new Pratt & Whitney Company; Pratt & Whitney had formerly been a longtime machine tool manufacturer.

Building a new engine was a risky adventure following World War I. The market was flooded with surplus airplanes and engines.

Pratt & Whitney saw the future to be the lighter air-cooled radial engines in the 400-500 hp range.

Pratt & Whitney told the NAVY of their project and the Navy assured them if such an engine could be produced, the navy would be highly interested.

When the first engines were tested, they were rated at 410 hp. The Wasp proved so successful that the US Navy ordered 200 engines in October 1926.

Before the sixth Wasp was even produced, they were already working on a new and larger design, the Hornet. By 1928, the military version of the Wasp was producing 450 hp; by 1933 power was up to 550 hp and eventually reached 600 hp.

The Peashooter used the -27 model which was rated at the 550hp from research I can find.

Here are some cleaned up photos used for the basic design photo used for this project:




More to follow!

Mike

[mbauer]

Ok, here are some interesting things. Some new tools to help with the several hundred small parts associated with this build project.

The small parts were changed several times throughout the design/build process. It seems so simple now that I have a almost complete model. Over 4-months total time has been spent designing the P26A Peashooter.

How many small parts can a huge P26A rubber band model have?

Over 261 cooling fins for this project! Researching photos and info, found several different versions with cooling fins of different counts.

Then re-read the history in the post above. The more power came from changes in the cooling fin from machining at first to changes in casting/forging.

The casting could explain the really wild fin patterns.

Look at this closeup photo of the R1340 on display; Please note the top cylinder look compared to the others-can you see the difference in the cooling fins?

Now if you go to this link, you will see a photo of an earlier version with not so many fins. Guess which version I used to make the project model?

Pratt & Whitney R-1340 Wasp

Yep, bottom fin count alone went from 26 to 10-each. Top fins had to be different outside sizes to make the correct shape.

The heads drove me crazy in 2D designing. You'll soon see my answer for these design failures. Not exactly to scale, but finally able to go forward with project. This one area has seen much paper wasted!!!!! Most of design hours, about 2-months worth, were for the heads. Sorry, they are not to scale.

Going to re-do the engine as a stand alone model. When done it should be a fully rotating model. Will base my 3D training on a re-production of this engine. It will have moving parts, even led lights to simulate spark plugs firing.

What? Spark Plugs firing? Yep, got interested enough in this engine model part of project, I want to design a rotating model.

To further step forward with how it will be printed. Not anything to unusual here. Well, remember a model called the Visible V8 Engine?

How can a model of the Pratt & Whitney R1340 be made into a Visible Radial 9 model? Already bought and delivered: double packs of size 11x17" (20-sheets per pack=40 total) and letter size (200-sheets total) of overhead projector transparencies for inkjet printers.

Thinking of the Ferrari V12 Engine build here at PM gave me the idea for this project.

Engine design/build project will be down the road. Photos of P26A build project are following.


I'm lazy. No, way am I going to cut 261 washers out for cooling fins.

Went to local hardware store. Bought set of Arch hole punches. Cost $72 to be able to use two of the set.

Main cylinder ring was changed to 3/4" diameter (dia). Bottom set of cooling fins are 1" dia. That means the paper is only 1/8" wide.

By using both the 3/4" hole punch and trying to center the 1" hole punch on the hole left by the 3/4" began punching out cooling fins. Way easier/faster than cutting with knife or scissors!

However, downfall was none were centered properly. Meaning cylinder fins took on their own shape, once glued to the cylinder tube.

Still used ten of the best to make a prototype build of a cylinder.

The next fins needed larger outside diameters to give the proper look.

The Arch style hole punches for these sizes soon reached over $250 and had to be ordered online. Most hole punch kits stop at 1" diameter.

Mayhew Pro 66002 hole punch kit to the rescue. Yes, I'm lazy enough to spend $274 + $84 for shipping to buy one kit!

Why the Mayhew? One strike creates washers. Two hole punches can be added to the same heavy duty strike handle. Everyone is perfectly centered.

If I'm going to build a working model, going to need cylinder fins, might as well get it now! Merry Christmas to myself.

Took 3-hours of using my hardwood club, made special for this project, and the different size outer diameters to complete the total of 261 fins needed. Awesome! Hole punch kit goes all the way to 2", for this project biggest size used was 1-5/16", so bigger builds can happen.

Can only guess at how many hours cutting by hand would of taken.

Photos follow:

First photo is Arch hole punch, 3/4" size in use. Even using scissors to cut outside diameter, if the inside 3/4" isn't lined up = offset cooling fin.


Engine case printed on special photo paper. Lots of color configurations were tried for this part of project. A medium blue gave it this look. A turquoise blue was my favorite, but just didn't look right with the "aluminum" look of the cylinders I found.

You can see how shiny the photo paper is, the cylinder parts in the back ground changed. wasted paper did not make me happy-thought the design was solid. Found too many issues with that version of the heads-way to many small parts to make with complicated folds-none were square when completed:


The following photo has many things going on:

Cutting Matt was bought special to be able to speed design-print-cut/build parts at design desk. Stopped going back and forth to hobby desk. (Created whole new issue: Where did the knife go-is it on the design or hobby desk? How it end up half way? Know how it got into the kitchen by the coffee pot-just wish it hadn't taken 20-minutes of looking in the hobby area)

Engine case parts including the balsa wood former that attaches to the Fuselage firewall. Rolled tubes on plastic straws? The cylinder tubes are being held in pre-shape condition by rubber bands.

The cardstock heads are shown. These are the final completed shape-interesting journey to get here.

My favorite new cutting scissors:


Completed Engine case ready to cut out cylinder holes:


Finished case setting on fuselage firewall location. The firewall has a 3/16" balsa pattern underneath the fancy gold metal flake paint, that the engine balsa pattern slides into. Already looking way better than the R1340 photo option teased about earlier:


A couple of cylinder fit photos, you can already see the aluminum shine look to the cylinders-same look for cooling fins:




More to follow!

Mike