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Post by deniseg17 on Oct 2, 2015 10:01:50 GMT
Hello everybody! I'm new here. I just had an idea for a Halloween costume and don't know how to bring it to life. I would like to make a peacock tail which will go from down and contracted to open and expanded using animatronics instead of pulling on wires. I have 400 feathers (don't know if I'll use them all), some of which are 6ft long, attached to a fan. The mechanism would be hidden with feathers and attached to a belt to make it removable. I would like the control to be either wireless or would be attached to the front of the costume, so it would need to be small. I've made a tail before that just laid flat and it only weighs about 1 pound or less. I think it would be cool to have a tail which looks like an actual peacock tail. I'd post a picture, but the one I have is >1MB, sorry. Any help with this project would be greatly appreciated.
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Post by Honus on Oct 2, 2015 18:14:40 GMT
I know how to do it. I'll make a couple of drawings for you tonight.  The biggest thing you have to worry about is the amount of leverage on the mechanism since the feathers are so long. Have you thought about where you would put the batteries? Since I'm going to recommend you use digital servos for this due to their better holding power you'll need to use NiMH or NiCD batteries due to the increased current draw- regular alkaline cells aren't going to cut it in this application. Wireless control is doable but you could also just use a small pushbutton switch on the front of the belt. It would be a lot less expensive than wireless and it would be really clean since everything could be self contained on the belt. |
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Post by deniseg17 on Oct 3, 2015 12:25:28 GMT
The push button is fine. I can get the batteries. Even though the feathers are light, I forgot about the drag of the 6 foot ones.
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Post by Honus on Oct 5, 2015 6:55:32 GMT
Sorry for the late reply- this weekend was a bit nuts with scheduling! So I've been thinking about this and just doing some rough back of the envelope calculations if your complete set of feathers weighs one pound with a maximum extension of 6ft. that's 16oz. x 72 (6ft. in inches) = 1152oz. That's roughly the equivalent weight your servo that has to raise the feather tail will see- imagine trying to lift a broomstick just by holding onto the very end of the stick. Essentially we're trying to lift one pound with a 72 inch long arm. Servos are rated in oz/in so if a servo has a rating of 350 oz/in that means with a one inch long arm it can lift 350 ounces. If you have a two inch long arm on that servo the amount of weight it can lift will be reduced by half or 175 ounces. The catch is that is the stall torque rating. That means that it can just barely lift 350 ounces with a one inch long arm (or 175 ounces with a two inch arm) and it will probably stall the servo trying to do it. When a servo stalls the current draw goes up dramatically, sometimes frying the servo control board if the servo stays in the stalled condition for too long. Ideally you never, ever want to stall a servo. So for your tail we get a rough calculation of 1152 ounces but the reason I say that's rough is because not ALL of the weight is at the end of that 72 inch long tail- only a percentage of the weight is at that extremity. Since you want a margin for error and you want the tail to move without struggling I'd go for a 7:1 ratio geared servo drive like this for raising the tail- www.servocity.com/html/spg7950a-cm_servo_gearbox.htmlThat setup will provide plenty of power and give you a nice controlled slow/smooth movement that will be very graceful. You could attach it directly to a wide belt using some aluminum sheet stock and that would give you a good solid base. You would then attach another similar geared servo to the output gear/shaft that would make the tail fan open and close. I'll make you a drawing asap and hopefully it'll make sense. |
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Post by Honus on Oct 6, 2015 18:31:52 GMT
OK so here's a quick diagram that shows how it would be done- hopefully this makes sense. You have one geared servo drive that raises and lowers the tail. This is connected to a two gear servo drive that opens and closes the tail. On the two gear drive the gears have to rotate in opposite directions in order to make the feathers fan out and collapse- the servo rotates one gear and that gear drives a second gear of the same size so both sides of the tail open and close at the same speed. All of this can be built using the pre made geared servo drives from Servocity. To add the second gear to the tail fan servo you'll need to make a mounting plate and use a couple of bearing assemblies to support the gear. I think the mechanism could be covered with feathers if you were to put a cover over it first so the feathers don't get jammed in the gears. You may also need some kind of back brace in order to better support the weight of the tail as it raises and lowers. Of course the drawing is just a quick sketch and isn't to scale or anything- it's just an idea as to how you would do this and I'm pretty certain it would work fairly well and give you a nice controlled motion. The effect would be pretty spectacular.  |
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Post by deniseg17 on Oct 16, 2015 18:41:11 GMT
Thank you so much for all your help. Just got back into the country. Don't know if I'll have enough time now to do this for this year. May take me the next year to pay for/build it. Also, still waiting on the feathers to be delivered. Have about 400 on the way.
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