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Author Topic: Electronic D/T for CLG  (Read 2550 times)
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climber
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« Reply #25 on: August 16, 2009, 03:10:35 PM »

Here's the prototype of the next version of my EDT with a new type of actuator. The unit you see here weighs 0.66 grams. With the capacitors added the ready to fly weight is 1.34 grams and can handle fly-offs of up to a good 8 minutes. The actuator generates about 150-200 grams of force and has a stroke of about 2mm (so you need a good latch). The metal tube on the right is the business end and when it D/T it moves to the left and compresses the spring.

This motherboard is going to be the basis for a number of FF doodads I've been working on. Depending on which components are soldered on it and which firmware it has it can act as an electric motor timed controller (limited to about 1 amp) or to drive a brushless motor controller with a servo signal. It can drive a servo for VIT and D/T functions instead of the actuator shown but will need a battery. They can be wired together with one handling a motor run and the other taking care of the D/T.

I still have a lot of development work to do but I thought you might find this interesting.

Craig
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Olbill
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« Reply #26 on: August 16, 2009, 04:54:01 PM »

It's very interesting! If/when you decide to sell these please put me on the list.
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Tmat
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« Reply #27 on: August 16, 2009, 05:54:37 PM »

Very interesting Craig!
So how does the new actuator work?

Tony
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climber
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« Reply #28 on: August 16, 2009, 08:55:02 PM »

Quote from: author Tmat
So how does the new actuator work?

I use flexinol muscle wire. With the wire I used you run a current of about 250 mA through it, it heats up to over 70 degrees C whereupon it shrinks up to 5%. The spring returns it to its previous length for another cycle. It's slow (takes about a second to finish retracting) and it's hard to use as a servo since it requires a lot of current to keep it in place but as a single function D/T it's difficult to beat its force to weight ratio. For my bigger models (coupe, P-30, Gollywocks, etc) it should be light enough to install directly in the tail for a pop-up stab. It won't really add tail weight since this entire unit is lighter than the extension rods and guides I used in my coupe and Gollywocks when I upgraded them to my previous version EDT.

The longer the actuator the longer the stroke. I am going to make a few tomorrow for cat gliders with a 10cm long actuator. It should weigh about 1.7 grams all up but have a stroke of 5mm or so. I plan to make some gliders much like Bernard's "Butter Cat" since I really like his D/T and trimming solution and plan to make some just for that.

I added provision for a start button and LED (so you'll know it's started) on the battery powered variants.
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« Reply #29 on: August 16, 2009, 11:36:41 PM »

Hi All,
Buttercat is finished here are some photos.....she weighs 35g balanced at ~55% :'(

The eDT seems to work very well and the installation is pretty clean.

I also show my foil...I tried to get her thin to drop the weight....did not work soo well.
TEST FLIGHTS SOON

B

That's a kit isn't it burnard? I must make one of these things. I really like gliders, and I especially want to make a DLG free flight glider.

The electronic DT is fantastic. I could not make a DT like this electronic one. I recently made my first Putty timer that was very successful. I thought that was a major accomplishment.

regards
Matthew
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Tmat
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« Reply #30 on: August 17, 2009, 12:50:53 AM »

Mathew,
Bernard's "ButterCat" was a design that he shared with us in the "5 panel wings" thread. The plan and some discussion about larger gliders are here :http://www.hippocketaeronautics.com/hpa_forum/index.php/topic,827.80.html
I copied the plan below from that thread for you. Hopefully, Bernard won't mind.
The thread also discusses my "LongCat" design (another large catapult glider).

I think making a large glider (over 20") is fun, but somewhat tricky. Making them light enough to get decent height is quite a challenge (as Bernard is finding out!).
I think that 16" to 18" is a much easier size for several practical reasons. They can be built to a reasonable weight without the need for very light balsa, and can be brightly colored for maximum visibility without worrying about the weight.

Tmat

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Tapio Linkosalo
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« Reply #31 on: August 17, 2009, 07:59:27 AM »


I use flexinol muscle wire. With the wire I used you run a current of about 250 mA through it, it heats up to over 70 degrees C whereupon it shrinks up to 5%.

Ok, two questions:

1) Where does one get this muscle wire?
2) Is the thermal expansion linear on temperature? In other words, if you get this 5% shrinkage on 70C warming, does it also expand 2,5% when going from room temperature to cold winter (+25C to -20C)? If it does, then one has to compensate for that... Maybe use a similar length of the wire, but unheated, to overcome the change in length due to different ambient temperature?
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« Reply #32 on: August 17, 2009, 12:47:36 PM »

Hi Tapio!

You wrote:

> 1) Where does one get this muscle wire?

I bought mine from robotshop.ca. It's expensive (>5 bucks a meter) but way cheaper than the geared motor in the previous version. The manufacturer is Dynalloy. http://www.dynalloy.com.

> 2) Is the thermal expansion linear on temperature?

Nope. Flexinol is a memory shaped alloy which undergoes a sort of "phase change" when a certain temperature is reached. The length does not vary much based on temperature until the magic 70 degrees is reached. Just after reading your post I tossed my prototype into my deep freeze which is about -15 C. My return spring keeps the wire under tension so if the muscle wire underwent any significant contraction or expansion when going from 18C in my basement to the freezer I should be able to measure it. Before going in the total length was 74.45mm and 74.73mm just after I pulled it out. It was in the freezer for 30 minutes.

By the way, ever since your questions on FFML I've subjected my D/T prototypes to the "freezer test" to make sure they work when cold!
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« Reply #33 on: January 04, 2022, 01:48:44 AM »

Craig

This timer is really interesting I can see how it would be great for small HLG/DLGs.
Did you ever product them in quantities? Are there some still available?
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