Antweight crusher need help!

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PKW
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Joined: Wed Aug 31, 2016 9:49 am

Antweight crusher need help!

Postby PKW » Tue Apr 04, 2017 5:43 pm

Hi all i'm Paolo, from Italy, i know there is no root wars contest/event here but i really like this strange sport since i was a child and i decided to start building a small antweight hoping to be able to travel to UK and give it a chance to win a fight or two.

The only previous "experience" i have with combat robots are all my 1kg RC lego battlebots (featuring witch doctor, carbide, pulsar and killerhurtz replicas, you can find a bit more on my yt and twitter), and i first wanted to build a rubber-band powered flipper, but the mechanism would become too complex to be realized with the means i have (a dremel, electric solder, handdrill with points till 3.0mm and a site where i can order 3dprints) so i decided to start a 9kg crusher bot.

the original idea was to have a full iron and and a winch mechanism powered by a 1000:1 pololu motor, to have some great crushing power, but then i read that those motors will break on stall, meanwhile i was choosing the final shapes i've built some test chassis since my ant will be arduino powered and i need to code it, here the first result:

Image

that was a good one but with grabber-grade power, also the 6.0v voltage regulator i was using for the servo has a a minimum input voltage that will make the servo die even at 60% battery charge, and that wasn't good, so i ordered some 3D prints and build the real main weapon (with a 298:1 motor):

Image

size comparison:
Image

small vid with half charge AA batteries (more than double the power with the 7.4v lipo):

https://twitter.com/PKW_ITA/status/845365706216685568

but then something bad happened, i assembled drive together again and i start testing an iron point but the arm got stuck, i've found that winch axle wasn't really aligned and this (on stall) caused a gear tooth to break, also the motor itself stop randomly also during no load and no geabox rotation so i just gave up with the idea of the motor powered winch...

last image:

Image

so then i really need your help, what i want to do is to find a good moddable servo (at least 5kg*cm) to use in place of the motor, if a 7.4v tolerant i'll just use the servo motor and remove all electronics, if there will be only 6.0v tolerant then i want to use servo electronics and solder the arm potentiometer to is, use my 6.0v regulator and at leas have a sort of lipo/wepon cut-off on low battery power.

what do you think? THANKS in advice!
there are no robot wars competition in Italy... so i make mine lego robot wars competition in my home! :D

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PKW
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Re: Antweight crusher need help!

Postby PKW » Tue Apr 18, 2017 6:58 pm

Really no one can help me? :-?
there are no robot wars competition in Italy... so i make mine lego robot wars competition in my home! :D

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UserFriendly
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Re: Antweight crusher need help!

Postby UserFriendly » Tue Apr 18, 2017 7:42 pm

I really like your crusher design. Personally I would stick with the motor rather than the servo and include a current limiter to prevent stalling the motor.

If you are really keen on using a servo to check out hobby king :

https://hobbyking.com/en_us/servos/all.html?___store=en_us

A lot of them specify the voltage they operate on on the specifications tab.
Andy B - Team UserFriendly
Reading Cybernetics Graduate 1996
Trying not to take Antweights too seriously. I think I'm failing.
First AWS was 46.

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peterwaller
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Re: Antweight crusher need help!

Postby peterwaller » Tue Apr 18, 2017 7:46 pm

I think the reason people are reluctant to advise is that a good crusher is quite tricky and not many if any have been successfully built.
The problem as you have already found is that a stalled powerful servo is likely to break itself normally by stripping gears.
Also a stalled powerful servo is likely to draw more current than a standard regulator can supply so I would use a servo capable of 7.4v operation and run it directly fro the lipo.
As I mentioned in my gripper robot you would be better to have some form of spring in the linkage that would limit the load on the servo and avoid stalling it.
viewtopic.php?f=1&t=1933&start=630
This will limit the maximum crush you can get but with modern armour you are unlikely to actually crush another ant more just grab and hold it.
I like this servo EMAX ES9256 HV but it is only 4.5 kcm.
http://www.servoshop.co.uk/index.php?pi ... area=Servo
Hope this is of help and its a shame you have no one to do battle with ( I know they have done ants in Germany and Holland) but it looks like you are having fun anyway.
Look at that you wait all that time for a bus and then two come at the same time. (English joke)


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