Author Topic: Colibri Hummingbird Dynamic Sculpture - WIP  (Read 17512 times)

Offline kvom

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Re: Colibri Hummingbird Dynamic Sculpture - WIP
« Reply #150 on: February 14, 2018, 05:15:52 PM »
Screwdriver is too fast and too weak.

I disassembled the air-powered motor I got at CF to see if the reduction unit and turbine could be separated cleanly.  They do come apart, but the input to the reduction unit is the splined shaft of the turbine.  To use the gearbox I'd need to make an equivalent with 12 splines on a .300" diameter shaft.  Gearbox is 15:1, so input for 7 rpm would be 105 rpm.

In the interim, I decided to gamble $14 on a 7 rpm DC gearmotor via eBay.

Waiting on post office for lead weights and screws to finish build and test for real.

Offline kvom

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Re: Colibri Hummingbird Dynamic Sculpture - WIP
« Reply #151 on: February 15, 2018, 11:46:05 PM »
The Colibri plans call for a "crank" on the input shaft that's just a 2" diameter disk.  It's OK for turning the mechanism slowly, but almost impossible to do so smoothly.  Why searching for a motorized solution, I came up with this temporary manual idea.



1/2" hex brass rod 1" long.  Drill .251" hole 1/2" deep plus a 8-32 tapped hole for a grub screw 3/8" from the opening.  This fits over the end of the input shaft replacing the disk crank.  Then using a speed wrench with a 1/2" hex socket, the shaft can be turned with pretty good control of the RPMs.



The lead disks I ordered came in the mail today.  They have decent regularity as to diameter and flatness.  I faced the mating sides and drill a 1/4" center hole through each, then assembled on a brass rod with lots of loctite 620.  After a few hours of cure, I could mount on the lathe to skim turn.



Finish isn't bad (didn't get a pic afterwards).  Total finish weight is 7 pounds 1 oz according to my kitchen scale.  The 3" length is such that the counterweight probably hits the table at Colibri's maximum angle.  I'll need to measure, but the permanent base is 3/8" thick with a gap in the center, while my temporary base is 1/4" with no gap.  I probably need to remake the counterweight arm 1" longer and at a higher angle than the current one.

Offline b.lindsey

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Re: Colibri Hummingbird Dynamic Sculpture - WIP
« Reply #152 on: February 16, 2018, 12:08:40 AM »
How was the lead to machine Kirk? Just curious as I have never machined any?

Bill

Offline kvom

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Re: Colibri Hummingbird Dynamic Sculpture - WIP
« Reply #153 on: February 16, 2018, 12:17:54 AM »
Very soft - chuck jaws left depressions in the sides.  The insert I use for aluminum left a smooth finish.  Drilling the holes gave continuous stringers in the drill flutes.  Skim turning and facing left very fine, fluffy swarf.

Offline crueby

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Re: Colibri Hummingbird Dynamic Sculpture - WIP
« Reply #154 on: February 16, 2018, 01:03:21 AM »
A lot will depend on the alloy, impurities, etc. Only 'machining' I ever did on any was drilling holes for bolts to hold some lead blocks in place in a boat.

Offline kvom

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Re: Colibri Hummingbird Dynamic Sculpture - WIP
« Reply #155 on: February 16, 2018, 01:58:44 AM »
According to supplier it's 99.9% pure.

Purer than Ivory soap but still doesn't float.   :shrug:

Offline crueby

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Re: Colibri Hummingbird Dynamic Sculpture - WIP
« Reply #156 on: February 16, 2018, 02:06:16 AM »
According to supplier it's 99.9% pure.

Purer than Ivory soap but still doesn't float.   :shrug:
Just flashed back to Monty Python and the Holy Grail, "what else floats?"  "Very small rocks?!"

Offline kvom

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Re: Colibri Hummingbird Dynamic Sculpture - WIP
« Reply #157 on: February 16, 2018, 10:56:08 PM »
My brass 2-56 screws came in from AME go I was able to assemble the flower.



I also did some measurements to determine how far above the table the counterweight would be at full Colibri height.  It appears that the current weight  (7 lbs) would just fit.  While 8 lbs doesn't tip Colibri backwards, operating it with 7 lbs doesn't seem to require any significantly greater force.  So I'm going to go with that for now.  Here's the weight after turning.



I suppose a coat of black paint wouldn't hurt.

Offline crueby

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Re: Colibri Hummingbird Dynamic Sculpture - WIP
« Reply #158 on: February 16, 2018, 11:05:33 PM »
The flower looks great. It needs an oil dispenser to feed the hummingbird...

Offline Perry

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Re: Colibri Hummingbird Dynamic Sculpture - WIP
« Reply #159 on: February 16, 2018, 11:22:07 PM »
What a nice model that will be  :ThumbsUp:

Offline b.lindsey

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Re: Colibri Hummingbird Dynamic Sculpture - WIP
« Reply #160 on: February 17, 2018, 12:19:23 AM »
Looking great Kirk. Can't wait to see it in motion.

Bill

Offline kvom

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Re: Colibri Hummingbird Dynamic Sculpture - WIP
« Reply #161 on: February 19, 2018, 05:25:32 PM »
I wrapped the outer circumference of the counterweight with some steel (.004") sheet, secured with epoxy.  I figured the less skin contact I have with lead going forward the better.



The length of the counterweight seem just short enough to clear the table at its lowest point by a whisker.

My motor is at the local post office awaiting delivery tomorrow around noon.  It will be interesting to see if it has sufficient torque to operate Colibri.  Derek's notes recommend a synchronous AC motor.  There are several of these with 6W power and 5-6 RPM on eBay, so that's another option.  Of course, AC isn't often available at shows, although I did see some overhead outlets at CF. 

Offline crueby

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Re: Colibri Hummingbird Dynamic Sculpture - WIP
« Reply #162 on: February 19, 2018, 06:07:31 PM »
Good idea to encapsulate the lead. On my model boats I like to give the weights a coat of epoxy - ugly, but its usually inside the hull out of sight.

Looking forward to seeing it all go - hope the motor works out!

Offline kvom

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Re: Colibri Hummingbird Dynamic Sculpture - WIP
« Reply #163 on: February 23, 2018, 03:29:27 AM »
I received the DC motor earlier this week, cobbled up a coupling, and attached it to Colibri.  Using a 12V battery charger for power and holding the motor by hand from turning, I determined that it appears to have enough torque to drive the complete cycle.



Next time in the shop I will make a motor mount I drew up in Solidworks to attach the motor to the side fame.

Offline kvom

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Re: Colibri Hummingbird Dynamic Sculpture - WIP
« Reply #164 on: February 23, 2018, 11:17:42 PM »
The eBay page for the  motor contained a dimensioned drawing of the motor exterior, so it was simple to draw up a mount in SolidWorks and then machine it on the CNC mill.



Attached to the motor with the only M3 screws I had on hand.



To secure it from rotating around the shaft, the hole in the tail aligns with the spreader rod holes in the support frame.  Now I just need an extension to the rod to attach the motor mount.