Author Topic: Motor and Electronics newbie questions  (Read 3995 times)

Captain Tetanus

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Motor and Electronics newbie questions
« on: July 10, 2017, 10:44:22 pm »
(Sorry for any repeat question I might have)

Hi all,

Just started the planning/gathering process for a 30 pound rear hinged flipper "Captain Tetanus", think Wheely Big Cheese but wayyy smaller and with protected wheels. The pneumatics warrent it's own thread, mostly worried about the geometry and what indivdual parts to buy but we arent that far yet. Here's current my noob questions and concerns:

1) Motors

I am taking the cheap route, grave robbing drill motors and gear boxes, 18v 550. Few questions here actually, first off will two of these motors yield passable speed and touque in a 30 pounder? I've read some stuff by other builders in this weight class that have had good results with this set up but I would love to hear everyones thoughts. Secondly, the motors I have commandeered have plastic first stage gears, while metal gears are prefered, I have not found a consensus to say plastic gears are a total no go. Is plastic acceptable for my needs? I like my cheap-o Harbor Freight stuff 8).

2) Electronics

Again I am a noob, I have a understanding of what is needed but when looking at a website shopping for parts I am just unsure of what will work and what wont or what is overkill. Can someone post links to the cheapest parts they can think of for a drivetrain control set up for this bot? On a similar vein what would be more cost effective a dual motor speed controller, like here or running two seperate ESCs with a mixer, like this? Also would the dual ESC I linked burn up with the 18v motors I plan to use and is a inverted controls channel possible with the linked Sabertooth?

Thats the pressing stuff right now, I want to build a mock-up frame to test the drivetrain on before moving forward to the nitty gritty of the weapon.

Regards

Coboxite

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Re: Motor and Electronics newbie questions
« Reply #1 on: July 11, 2017, 06:19:00 am »
1: The issue with HarborFreight drills isn't the plastic gears, though that is an issue. The real major problem is that the end carrier plate and the carrier pins are not hardened. Because of that, the main cause of failure is the end carrier pins either falling out, or shearing off. The slightly more expensive 18v drills(Black&Decker, Ryobi, Craftsman) do harden the end carrier plate and pins, and are far better suited for combat.


2: Please, PLEASE, for the love of god, stay way from any Sabertooth speed controller, they are vastly overpriced and way too fragile for combat at any weight class. Avoid at all costs.


For actually good ESCs for feathers, the cheapest that actually work is the hacked hobbyking TZ-85amp. You can either get the speed controllers from Hobbyking and hack them yourself, or get them prehacked.

MarkHarrison

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Re: Motor and Electronics newbie questions
« Reply #2 on: July 11, 2017, 08:17:41 pm »
Harbor Freight drills should give you adequate power for a weaponed 30 lb bot.  Both Kitbots and Team Tiki make wheel hub mounts for drill motors that work quite well. I would definitely suggest using one of these pre-made hubs rather than trying to rig up your own wheel mounting method.



As far as speed controls, the one you linked to is rated a bit under what you will need for a 30, and is definitely not adequate for combat. At a minimum you will need something in the 25A - 30A range. Two Botbitz 30A or 75A controllers with a Fingertech Tinymixer is the most common speed controller setup I've seen. Two of the 30A controllers and the mixer will run you about $100, and is probably the cheapest set-up you are going to be able to get away with. A little bit more expensive than that is the Scorpion XXL, which is what I used in my 30, before I switched to brushless.

Captain Tetanus

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Re: Motor and Electronics newbie questions
« Reply #3 on: July 11, 2017, 10:30:50 pm »
Fast replies, thanks!

The other issue I've already ran into is that I cannot find anyone who makes drill motor mounts anymore, kitbots no longer make/sell them. I will look into electronics suggested but have a look at these https://www.ebay.com/itm/162567732171 (sorry for the raw link) would these puppies work?

Mark are these the ESCs your referring to? http://ttrobotics.com/botbitz-30amp-esc/

Team Tiki has motor mounts
« Last Edit: July 12, 2017, 02:25:24 am by Captain Tetanus »

Captain Tetanus

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Re: Motor and Electronics newbie questions
« Reply #4 on: July 12, 2017, 01:50:57 am »
One other thing while it's fresh in my head, will the Fingertech mixer be able to handle the power my system will require? Battery suggestions?

MarkHarrison

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Re: Motor and Electronics newbie questions
« Reply #5 on: July 12, 2017, 06:39:09 pm »
Yes. those are the 30A escs I referred to. The Tinymixer is what I use in my 30. There are people who use them in heavyweights. They should be sufficient.

Turnigy batteries from Hobbyking are a good deal as far as batteries go. Something in the 2000 mah range should serve you well.

That Ebay esc is almost certainly crap. I've tried similar esc's, and generally they have no braking, reverse is less than half speed, and the rating are greatly inflated.