Axe motor/servo?

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GeorgeR
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Axe motor/servo?

Postby GeorgeR » Sun Sep 18, 2016 10:10 am

Looking at the aws videos on youtube there doesn't seem to be many axe/hammer bots, so just to mix it up I thought I'd have a go at making one, but was wondering about powering the axe.

My initial idea was to mod one of the high speed servos (turnigy 306 or emax es9256) for 180 degree rotation and use that to swing the arm. Do you think that would work, or should I be looking into a brushed gearmotor setup with a couple of limit switches? I was planning on a pretty big axe, roughly 10cm arm and 30g head.

cheers, George
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Occashokka
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Re: Axe motor/servo?

Postby Occashokka » Sun Sep 18, 2016 12:46 pm

Unfortunately the reason there aren't many is that they are very hard to make effective, most current axes use brushed gearmotors. You say a roughly 10cm hammer arm, Isn't that going to be rather tight in the cube limit?
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GeorgeR
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Re: Axe motor/servo?

Postby GeorgeR » Sun Sep 18, 2016 2:08 pm

Yeah, 10cm is going to be a tight fit, I think it can be done, and if not its going to be very close, I can definitely get a 9.5cm arm in.

I did see that some people had used gear motors before, but was thinking that a servo would be simpler as it wouldn't require external positioning switches. I guess I'll probably have to try some experiments to test the concept.
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Shakey
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Re: Axe motor/servo?

Postby Shakey » Sun Sep 18, 2016 2:40 pm

To be honest on an antweight axe you don't need limit switches. Just fire it off rudder. A gearmotor and Vex29 is probably your best bet.
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Re: Axe motor/servo?

Postby Skillz » Sun Sep 18, 2016 3:34 pm

That would be beautiful to see an effective axe robot
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GeorgeR
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Re: Axe motor/servo?

Postby GeorgeR » Tue Sep 20, 2016 7:17 pm

Gearmotors it is then. I'm going to get calculating and figure out the best option for gear ratios, and thanks for the Vex 29 recommendation, I hadn't seen those before.

It would be great if it does actually turn out to be effective, and if not the stupidly large axe should at least be entertaining to watch.
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Fenrir
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Re: Axe motor/servo?

Postby Fenrir » Wed Sep 21, 2016 10:21 pm

I actually had the idea to stick padlocks on a large Stanley knife blade axe head, as weights and maybe fit the motor with a gear missing some teeth on one quarter of the gear and fit the axe on a second gear connected up with an elastic band pulling it forwards, so when the gear spins the axe pulls back and then when it hits the point of no teeth it springs forwards, somewhat like Peter's football kicking robot, but with a second pinion gear instead of a rack.

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UserFriendly
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Re: Axe motor/servo?

Postby UserFriendly » Thu Sep 22, 2016 6:00 am

Shakey made a continuous axe mechanism here:
https://youtu.be/7n3GtLS1sWk

viewtopic.php?f=1&t=1754&p=56120&hilit=Continuous+axe#p56120

He might print you a mechanism...
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Hogi
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Re: Axe motor/servo?

Postby Hogi » Sat Sep 24, 2016 5:24 am

I've just ordered two turnigy 180 degree servos from hobbyking for a couple of axe weapons. I doubt they'll be particularly competitive though.
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