Fiddlers Green
http://www.fiddlersgreen.net/forum/

Gripe Atonement (No. 1 in sequence)
http://www.fiddlersgreen.net/forum/viewtopic.php?f=2&t=2872
Page 1 of 1

Author:  airportkid [ Wed May 07, 2008 4:11 pm ]
Post subject:  Gripe Atonement (No. 1 in sequence)

Having gotten into trouble in the topic below, accept my apologies, and for those who would like to be able to make propellors that look like this ---

Image

--- By way of atonement I've posted here the parts sheet of my scratchbuiilt 1/60 scale Avenger propellor ---

Image

--- and assembly instructions below. I hope you'll find this miniature a nice detail touch for future models, and not too terribly difficult to assemble. The blades are a photograph of an actual TBM propellor blade, with the Hamilton Standard decal enhanced by shrinking a full scale copy of the decal down to 1/60th. While the prop is a TBM prop, the general configuration is identical to many of the hydromatic propellors used on countless aircraft, with the only variation (for modelling purposes) the radius and aspect ratio of the blades, which can be easily adjusted to suit by using any photo editing software.

NOTE: You made need to enlarge the image here - the blades are 1-5/16" root to tip at 1/60th scale.


To begin - some nomenclature:

The blade halves need no introduction, but the rest of the parts do.

The blue-yellow stick figure at the right is the "spider" that the finished blades are glued to, both anchoring their 120 degree orientation from each other and their pitch. The spider gets folded up to 4-ply thickness for strength.

Just below the blades at the left are their three "root collars". These are wrapped around the blade roots and represent the main body of the hub.

Next to the root collars are the two "hub collars". They form the front and back of the hub (and are identical).

The cross-hatched parts are the three "hub flanges". These are folded over the edge of a piece of thin cardboard to give them thickness (and hence the cross hatched area to give you something large enough to fold). They're fitted between adjacent hub collars and represent the hub flange and its bolt bosses (note the tiny twin boltheads visible on each flange).

Finally, the piece at the bottom is the "piston dome". This is curled up and glued into the front hub collar, finishing the propellor. It represents the dome housing the pitch changing hydromatic piston. (The propellor is constant speed - a governor geared to the crankshaft maintains constant RPM by increasing or decreasing oil pressure against the piston in the dome, which rotates a cam that changes blade pitch. Desired RPM is set in the cockpit, which establishes a nominal pitch: flat pitch for high RPM (takeoff), and high (fat) pitch for low RPM (cruise). High RPM flat pitch produces lower airspeed but increased climb; low RPM high pitch produces high airspeed but decreased climb).


STEP 1.

Don't cut anything yet. Grab a scoring tool and score the following folds:

Spider fold lines.

Hub Flange fold lines (both of them - they're VERY close together, the thickness of a cardboard apart).

Hub collar fold lines (for doubling over).


STEP 2.

Now cut the sub assemblies apart, as below:

Image


STEP 3.

The blades are so thin it's best to pre-curl them while they're still together on the sheet, to prevent inadvertant creasing. Curl them up pretty tight - their roots will need to be full half cylinders when finished.

Image

Cut the blades apart, trim them not quite to the finish edge and tighten their curl even more (using a thin rod as shown).

Image

Trim them to their finish edges and curl their roots even more tightly (using a thinner rod as shown).

Image

Don't forget to tint their cut edges! A pencil is exactly the right shade and texture of color to use on flat black propellor blades

Image


STEP 4.

Glue the blade halves together. Let the roots dry as shown as an ellipsoid - don't try to make the roots cylindrical until the glue has dried.

Image

Glued and dried blades should look like this

Image

Image


When all the blades have been glued, you'll have the beginning of a first rate propellor!

Image


TO BE CONTINUED --- (Other duties call)

Author:  WII [ Wed May 07, 2008 4:40 pm ]
Post subject: 

wow!! :shock: :shock: I've wantin' to build more realistic props ever since I saw an old thread called "proper propellers" or something like that, but my attempt at scratch building one didn't work out.
with slight modifications these parts could be used for the F4F, F6F, SBD,
F2A, F4U-1...... maybe I'll build a few airplanes for a change...

Author:  oibbill [ Wed May 07, 2008 6:03 pm ]
Post subject: 

Wow..No atonement needed by me. I have mostly carved wooden props when appropriate. I am now building a Hellcat and am going to attempt your neat design. Thanks

Author:  possm_23 [ Wed May 07, 2008 6:33 pm ]
Post subject: 

thats an excellent post....thanks alot. :D :D :D

Author:  willygoat [ Wed May 07, 2008 11:35 pm ]
Post subject: 

SUPER- DUPER!!!! That's pretty neat. Thanks!

Author:  cmdr199212 [ Fri May 09, 2008 11:35 am ]
Post subject: 

Dude I love you! that will be a great addition to just about all of my models thank you thank you thank you!

Author:  John Dell [ Fri May 09, 2008 1:32 pm ]
Post subject: 

WOW! I'm going to try that on my B-24.

Author:  WII [ Fri May 09, 2008 2:17 pm ]
Post subject: 

do I dare try this in 1:87 scale? it would be really really tiny...

Author:  airportkid [ Fri May 09, 2008 5:04 pm ]
Post subject: 

WII wrote:
do I dare try this in 1:87 scale? it would be really really tiny...

I haven't tried it but if you used typing paper rather than cardstock, 1/87th may not be that hard to do. The hub flanges would be the only challenge - those little b***rds are already electron-microscope material at 1/60th scale - at 1/87th they could disappear altogether!

Try it out though - & let us know the results!

Author:  possm_23 [ Fri May 09, 2008 8:46 pm ]
Post subject: 

ohh yeah...by the way...you must have really good camera.....those are very crisp and sharp pics.... :D

Author:  airportkid [ Sat May 10, 2008 1:18 am ]
Post subject: 

John Dell wrote:
WOW! I'm going to try that on my B-24.

One side attribute of this design is that building a feathered prop is easily accomplished by simply gluing the blades to the spider at 90 degrees of pitch. You might try building one of the B-24's props feathered, and photoshopping burnt oil stains on the nacelle aft of the cowl flaps to simulate an engine smashed by enemy fire.

Author:  Tahutihotep [ Mon May 12, 2008 11:20 pm ]
Post subject: 

SWEET! i'll try that when i take in my B17 project. thanks airportkid!

Page 1 of 1 All times are UTC - 7 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/