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Misc / Robotics with Python
« Last post by Fingerpuk on November 12, 2016, 07:15:09 AM »

I'm new here, and I'm new to robotics. Before the question a little background on me - I run a design studio in London, I have a physics and programming background, and my first career was as a 3D modeller for the visual effects industry. So I can handle code, and I can handle CAD (I use Rhino and Autodesk) but I'm very new robotics. I did a small stint with practical effects so understand servo control, and I also own a small 3 axis mill but am looking to upgrade to the PocketNC.

Quite frankly I'm bored. My son is interested, and as I want him to learn computer science, robotics, and AI I want to help him as much as I can. I like Python as a basic language so I wondered if there was a way to communicate easily via Python to a controller that will let me hook in off the shelf sensors and servos, and get data back? I like to idea of being able to do basics, but also handle complex calculations on the host computer.

I've read up on all the search results you get for Python and Robotics, but I'd love to hear form anyone who has it working rather than reading sales material.

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Mechanics and Construction / Re: Carbon fiber advice for UAV looking design
« Last post by Avadon77 on November 09, 2016, 04:54:38 AM »
Carbon fiber and fiberglass will both work just as well for your project. You're not going to be shooting a missle at this thing or hitting a barrier. Carbon fiber clearly much tougher than fiberglass but either would work. I've laid up both and thin carbon fiber lays up just like fiberglass. Previous commentor is right, it is more expensive so most hobbyists tend to use smaller bits of it but it's readily available on ebay and amazon in various weights.

The trick with getting good carbon fiber results is to use a really good epoxy resin

I reccomend you buy C&J Epoxy resin.. the gold standard of epoxy resin to lay up fibgerglass and carbon fiber. Dries glass clear. Worth the money. You can even sandwich layers of fiberglass and carbon fiber or if you want to get really serious you can even do carbon fiber and kevlar. But if I were you'd i'd lay it up in laybers of fiberglass and some carbon to get the stiffness you want and thickness.

anyway those are my 2cents
Mechanics and Construction / Re: Anybody make their own wheels?
« Last post by Avadon77 on November 09, 2016, 04:48:11 AM »
Looking at the cover of your book that looks like they came off of a big wheel.. you know those electric cars they buy for the kids. You can find those at garage sales and goodwill stores from time to time. They make horrible tires for robots because slippage on hard plastic wheels means you can't use encoders on the wheels. You really need something with good rubber which is why i suggest the contact wheels. Failing that I'd go for some kind of penumatic wheel (something like a real tire.. maybe handtruck wheels, wheel barrow wheels, or garden cart wheels. You can find run flat rubber tires in the dimensions you're looking for 10-14" if I recall. Might be worth a look?
Mechanics and Construction / Re: Anybody make their own wheels?
« Last post by Avadon77 on November 08, 2016, 11:26:29 PM »
Also look on Aliexpress for 14" wheels. I source a lot of good robotics stuff out of there.
Mechanics and Construction / Re: Anybody make their own wheels?
« Last post by Avadon77 on November 08, 2016, 11:23:09 PM »
Hmmm, never messed with that OS. I'm still using raspbian. My main problem is with wheels is that the only 14" diameter I can find are either way too heavy, or too narrow to keep from sinking because of weight. This sucker is going to have some mass to it. Aslo, I'm not willing to spend over a  hundred bucks on cheap plastic. lol

When it comes to making wheels I've never decided to do it because there's only a few billion wheels on the market for robots and industrial machines. The only time I've ever seen where people make "wheels" is where they make their own hub/sprocket combinations for tracked vehicles and even a lot of that can be done with off the shelf chain sprockets. So I really don't see the reason to make wheels.

look at all these wheels!

How fast is this robot going? Are we trying to do 35 mph or 3.5 mph?

You can get really large contact wheels 12" and higher from many suppliers if you're talking about precision, Aluminum billet wheels with duro70-80 rubber on them (think car tire hardness rubber). They're not cheap but they'll last forever

I got some of my wheels from my friends at Beaumont who I also get my sanding machinery equipment from.

I'm sure if you search you can find a 14" contact wheel.

Now if you're talking more of a pneumatic/offroad wheel than tractor supply as mentioned, Big R, MSC/Grainger has tons of wheels too.
This is a huge broad question. If you're trying to build a wheeled robot I suggest you start with a robotics chasis. Do not try to use an RC Car or Truck because they are very difficult to adapt for most people. You'll probably want a motor or servo on each wheel.

There are tons of wheels here
Mechanics and Construction / Re: Tracked Vehicle Control Arm angle?
« Last post by Avadon77 on November 08, 2016, 11:09:41 PM »
These road wheel arms on these two robots (Green is FIRST robotics team robot and the other is a Darpa Suspension robot) have a much higher angle.

So I'm wondering should the arms be much lower like 15dgs on the Abrams and other military tanks or should I be much higher like many other robotics chasis? and what is the difference?

Mechanics and Construction / Tracked Vehicle Control Arm angle?
« Last post by Avadon77 on November 08, 2016, 11:01:41 PM »
I'm building a tracked robot and trying to figure out what angle the axle arms/control arms should be set at? I measured the M1 Abrams tank and the road wheels are all set to 15dgs except for the leading wheel which is set at 40dgs.

But then I looked at other robotic tracked vehicles and they look to be around 40-60dgs. Is there some special angle? Of course this dictates how the suspension will work as well.

any clue what angle these axle supports should be placed at?

Mechanics and Construction / Re: Robot wheel/omni Directional Wheel
« Last post by Avadon77 on November 08, 2016, 10:07:35 PM »
what are the dimensions of those wheels?

I've never used Omni's and I'm hoping I can get the following answered as well as your questions.

*What are the trade-off's with larger vs smaller rollers on the omni wheels. I see some that have a ton of tiny small wheels and others which only have 3-4 rollers. What is the pro vs con with this?
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