# Spinning Prop Simulation



## Brent Gair (Jun 26, 1999)

Not an idea I really advocate.

Trying to simulate a spinning prop on a model is rarely successful. There's no good way to do it...just some ideas more ridiculous looking than others!

But I was reading a thread about this on another BB and it seemed like an intriguing challenge. Even though I don't like the idea, it seemed to interest enough people that I thought it might be a fun idea to try.

I slapped together a small experiment to test my ideas. Well, it's not altogether successful but I've learned a few things that will point me in the right direction.

I used an acrylic disc about .10" thick. Spun in on the lathe and held Scotchbrite against it to purposely create a texture to simulate rotary motion. I over did that idea and the prop disc is more opaque than it should be...but that's a lesson learned. I also had to make a new spinner from aluminum stock as I was not about to chop up the good kit prop. Acrylic paint was applied from the backside of the disc.

The idea needs a lot of development but, at least, it's no worse than most other ideas . The real satisfaction came from the speed with which I was able to test out my concept. The big investment in tools is starting to pay off. I got this idea late last night and, by the time I went to bed, I had the new aluminum spinner epoxied to the acrylic disc. The ability to prototype new ideas...even if they aren't completely successful...so quickly is quite handy. Better to kill 2 hours on a bad idea than 2 days.

So here's a link to the first of TWO photos. Hit "next" from the the picture in this link to see the second photo.

http://groups.msn.com/Margaret6547/miscellaneous.msnw?action=ShowPhoto&PhotoID=71


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## John P (Sep 1, 1999)

Kinda works!
Can you turn the edges of the disk so they're sharp? The only thing that takes me out of the illusion in those pics is the hard, square edge.


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## Brent Gair (Jun 26, 1999)

Hmmm...

Perhaps it a bad photographic angle or reflection...but disc faces at the edge were shaved with a coarse (can I say "bastard") file while spinning on the lathe. There's a soft radius on the edge.


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## John P (Sep 1, 1999)

Yeah, now that you mention it I can see that it's radiused. I can still tell it's a solid object with an edge, though. Like you said, tough to do.

When Dad was in the Pacific, he sent home a little cartoon carving of him in his plane, including a spinning prop made from clear acetate with spin lines scratched in. It was actually pretty effective, but in a cartoony way. It'd never work for real.

Here:
http://www.inpayne.com/dad/rock.jpg


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## Brent Gair (Jun 26, 1999)

You're dad was a talented guy. Funny thing about my father...he was always into motorcycles and airplanes when he was young but I never saw him work with his hands in the last 20 years of his life.

Anyway, the reason the spinning prop idea interested me (though, it's still not something I would use other than if absolutely required for a diorama) is that I saw this in a thread about the subject:

http://s96920072.onlinehome.us/ISL/Prop_Blur/review1.48/PropBlur_review.htm

Incredibly, this was the best idea that people could come up with...photoetched prop blades. I've seen these before but the discussion refreshed my memory. I dunno. Taste is subjective and maybe these really do look good. In my opinion, the idea is pretty weak.


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## John P (Sep 1, 1999)

Yeah, that looks pretty stupid. Maybe if it was translucent.

btw, Dad also did a bigger version of that sculpture, but with a motor to turn the prop:
http://www.inpayne.com/dad/float.jpg
:lol:


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## Jastor (Nov 8, 2003)

*why make it look like it spins?*

I think your example is among the finest I've seen! Definitely on the right track!

But if you don't like making it _seem_ like it's spinning, why not make it spin for real:

http://www.finescale.com/fsm/objects/pdf/motorizedspitfire.pdf


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## Brent Gair (Jun 26, 1999)

Thanks for compliment, Jastor.

Several people have suggested actually spinning the prop. My intial reaction was, "Who needs the aggravation?" My spinning prop simulation is a simple "plug in" replacement for the stock prop.

But I must say that the idea is starting to grow on me. It's not that I have any real desire to display models with spinning props. However, as an engineering challenge, my interest is piqued.

When I did this project, it was just because it represented an interesting challenge and I thought I could make use of some of the tools I've acquired in the last year. The lathe allowed me to do things that aren't practical for many modelers (an obvious example being the fact that I could manufacture a replacement spinner from aluminum and not have to sacrifice the kit prop).

Now that I think about it, the REALLY spinning prop also represents some possibilities to do some unusual work. I'm not interested in just sticking a motor in a model. There's nothing wrong with the idea...but it's already been done by people who are better model technicians than I am. However, I do have the capability of manufacturing unusual mechanisms. I have a stock of special plastic used for making bearings and bushings. I can make metal shafts of any diameter. I can even build simple universal joints.

What I need is some kind of off-beat model that most people wouldn't think of motorizing. No point in sticking a motor in the nose of Spitfire or P-51 if others are doing it very nicely. I could do a project where the motor is in an unexpected location and is connected to the prop with a long, hidden shaft. 

Hmmm...have to check my stockpile.


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## Jastor (Nov 8, 2003)

You're welcome! As I said, I think your example was excellent. The photoetch set that was posted is absolutely terrible, though I think it would look great on a cartoonish model.

I think perhaps a motorized Wright Flyer might be a challenge! There you've got one source of power moving two props. That gives some opportunity for an interesting linkage.


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## Roguepink (Sep 18, 2003)

I read a similar article in a FSM some time back. It used some airbrush techniques, and less scuffing on the disc. Maybe use the airbrush to paint the prop blur and hit it with a Testors flat clear laquer?


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## Brent Gair (Jun 26, 1999)

I have that FSM article.

Although the effect is well done, it continues the most common flaw of the clear disc technique.

The plastic used in the FSM article is .015" sheet. In 1/48 scale, that describes a prop arc less then 3/4" thick from front to back. In 1/72 scale, it's a 1" depth. That's just way, way too thin. That's always bothered me.

The prop on a real aircraft, depending on the pitch, might reasonably be expected to create an arc 3", 4" or more thick. I used .10" thick acrylic on my disc which gives a scale arc thickness of 4.8"....just about right for a Corsair.

But I do have work to do. I think the scuffing technique is correct but I over did it. The ones in the FSM article are TOO clear. The ideal look could probably be achieved by splitting the difference between their under done look and my over done look .


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## Roguepink (Sep 18, 2003)

Yeah, it needs to be more clear. At speed, you would visually see through the spinning area, but it would be diffuse. I'm sure if I consulted my physics notes, I could lay out the science behind it.

I'm still using the kit props, not showing them spinning. I put my 1:72's on their wheels anyway, and many props have detail (such as the markings on a P51 prop blades).


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