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Slow Melty Brain


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motas



Joined: 02 Feb 2019
Posts: 3


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Slow Melty Brain

Hey all,

Apologies for the technically non robowars question, but it's the best place I could find to ask!

I'm about to start building my first "real" robot, and I'm looking at building a giant slow motion melty brain which will work as a spreader. The current design of the robot weighs around 50kg, so obviously can't spin as fast as a typical melty brain robot. My question is, will translational drift work okay at very low rotational speeds? I'll be using 3 large wheels and alternating which two are on just like a normal melty brain would.

My second question, is can anyone recommend a decent motor which would be able to move a robot of this size? I need to use 3 and I would ideally like to find a "standard" sized motor which I can easily source later on, the chassis will be expensive so I don't want to change the motor mounting if the motors need replacing. Is there an appropriate standard mounting hole spacing and shaft size I can use? I am planning on using 12V brushed motors and SLA batteries as weight is an advantage in this application.

Thanks!

Post Sat Feb 02, 2019 2:14 pm 
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Knightrous
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Joined: 15 Jun 2004
Posts: 8497
Location: NSW


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A slow spinning melty brain is actually easy to build as you are not trying to speed up and slow down wheels at thousands of rpm and you will be able to use existing PWM speed controllers (Instead of resorting to high speed SSR's or specialist high frequency input ESC's).

Probably to give people more information so they can provide you with better feedback, can you tell us your location and the rule set you are planning to building to?
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Post Mon Feb 04, 2019 8:42 am 
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motas



Joined: 02 Feb 2019
Posts: 3


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Thanks Knightrous,

This actually isn't for a robowar at all, but it is the only place I can find ANY information on melty brains. I am trying to build a robotic rake and roller which will grade and compress a sand area, hence the high weight and low speed. I can't find any information on anything like this.

Post Mon Feb 04, 2019 9:11 am 
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shakesc



Joined: 14 May 2012
Posts: 62
Location: UK


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You can go big

http://www.robotwars.tv/competitors/season-9/week-1/nuts-2/

You could go slow but my question is how much friction on the ground will you have (sand / gravel)?
We found Nuts translational control sensitive to the ground friction

Post Mon Feb 04, 2019 9:14 am 
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motas



Joined: 02 Feb 2019
Posts: 3


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There'll be quite a lot of friction, with 50kg of pressure and prongs sticking into the ground. I thought there might be a slipping component to translational drift which required some speed to overcome, but since I'm going so slow I may also be able to reverse motors as needed to get a bit more sideways movement.

Post Mon Feb 04, 2019 8:02 pm 
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Knightrous
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Joined: 15 Jun 2004
Posts: 8497
Location: NSW


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Have a look at Open Melt - http://www.nothinglabs.com/openmelt/
It's the most complete and open control software for "Melty brains" currently.

Your purpose sounds like it will need an accurate amount of data for heading and control. Since you are at low RPM, you could likely use a combination between accelerometer, gyro, magnetometer and wheel speed sensors.
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Post Thu Feb 07, 2019 10:06 am 
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