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21
Robot Videos / Re: FingerTech's new wheels - Wheely?!
« Last post by mklrobo on August 28, 2015, 02:56:21 PM »
 8) Cool !
Great Job on Big Blue!   8)
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Mechanics and Construction / Underwater Thrusters
« Last post by Lacrosse24 on August 28, 2015, 11:54:02 AM »
If I have a flat floating object roughly 6 feet long about a foot and a half wide weighing around 9 pounds, and it had 2 underwater thrusters fixed on the bottom side of the back end of this object with each thruster having around 9 pounds of thrust, what would its top speed be or can you even figure it out with this information.
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Electronics / Transmitter and Reciever for Thrusters
« Last post by Lacrosse24 on August 28, 2015, 08:02:06 AM »
I'm trying to find a reciever and transmitter that is compatible with my underwater thruster setup so I am able to remotely turn the thrusters on and off.  The transmitter would have to be waterproof because it would be on person while in the water.  The transmitter would be no more than probably 15 feet from the reciever at all times.  The setup picture is in the attachments except I'm trying to use 2 underwater thrusters and I'm not sure how to combine the wiring so they would run off he same battery, ESC, and reciever.  Does the transmitter and reciever have certain specifications that depend on the motor, if so, here are the details of each thruster.  It's a DC motor with a max power of a 150W, max voltage of 12V, max thrust of 3.8kg, rated current of 12A, max current of 30A and I'm already sure you need at least 12.5 amps per thruster coming from the battery if that means anything relating to the transmitter and reciever.  Thanks a lot hope to hear from someone soon!  ;D
24
Robot Videos / Re: FingerTech's new wheels - Wheely?!
« Last post by bdeuell on August 28, 2015, 07:46:49 AM »
I purchased those exact mecanum wheels (i think about 5-6 years ago). a word of caution with heavier loads the press fit rollers can slide off the pins during use. this gets quite annoying when you need to stop the robot and search for the little washers and rollers that keep falling off.

The reason i actually purchased them was to construct a prototype/test platform robot before designing and building custom 14" mecanum wheels.
https://www.youtube.com/watch?v=DKQWQICFGW8
The application of these mecanum wheels is a little different than I have seen anywhere else as we only used them on the front wheels to allow for more accurate and efficient turning with a four wheel drive robot. Usually they are used to make an omnidirectional robot.

Other than robots I have seen this type of wheel used on forklifts
25
Robot Videos / FingerTech's new wheels - Wheely?!
« Last post by mklrobo on August 28, 2015, 06:15:00 AM »
 ;D Hello!
Check out this video about a new type of wheel, and their capability!
https://www.youtube.com/watch?v=DhNm0FOIiG0#t=58
Fingertechs angled wheels. Enjoy! (Hope the address brings you to it)  ;D
26
Mechanics and Construction / Re: new here... howdy. Also, multi-stage belt drives?
« Last post by mklrobo on August 28, 2015, 05:15:45 AM »
 ;D Hello!
I would like to introduce a comment on your indication of a research vector in this arena.
I  have found some good mechanical books for idea generation, such as;
Ingenious mechanisims, for designers and inventors, volume 1 - 10.
Schaum's outline series, theory and problems of Machine Design.
I like to tip toe through  mechanisims, from time to time, as it is fun to examine inventions.
Good luck!   ;D
27
I don't see why you need low backlash for a skateboard but to be fair i dont ride one. if your system really only experiences load/torque in one direction this isn't really an issue. if you get rid of this requirement it opens up your drivetrain options considerably.

Hey man, I'm not on the robot forum because I'm building skateboards. The skateboard was just my inspiration. It's pretty impressive watching a skateboard propel a 200lb man up a 25% grade. I just saw that and thought, man, that would be an awesome actuator. All these skateboards come with a belt on each motor and a 1:2 reduction ratio. I just think I probably need more, unless my math is wrong.

we get lots of variety in what people post on this form and the non robotic topics can be anything from electric bikes to animated sculptures.

I am interested to hear more about what you are actually working on, I apologize if it is in your original post but i read it a few times and i'm not quite sure. Drive mechanisms are very interesting subject and i still have a lot to learn. I toyed with a few ideas in the past to create low cost high performance drives for robotics but never went anywhere with them.

Just a large format digital robotics actuator. Ideally, something precise enough to be used in a robot arm (similar to universal robotics arms, not big industry car assembly line arms). Also, preferably with a good torque to weight ratio, so it can be used to build large walking robots.

I just don't see a lot of this stuff in the market right now, so I'm exploring the idea. I figure once I get the mechanical/electrical stuff worked out, I can wire it into a CAN bus or something and make a bunch of them and just play around with inverse kinematics and such.

I've never worked with real industrial robot arms and I'm a software guy, so programming them interests me. I've got a few projects around the house it would be interesting to automate (lampwork, mostly).

This is more of a research vector for me at the moment than an implementation thing. However, once I find something I like, it'll become an implementation thing quickly and I'll stop researching much at all. Just kind of how I operate.
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Mechanics and Construction / Re: new here... howdy. Also, multi-stage belt drives?
« Last post by bdeuell on August 27, 2015, 12:16:14 PM »
I don't see why you need low backlash for a skateboard but to be fair i dont ride one. if your system really only experiences load/torque in one direction this isn't really an issue. if you get rid of this requirement it opens up your drivetrain options considerably.

Hey man, I'm not on the robot forum because I'm building skateboards. The skateboard was just my inspiration. It's pretty impressive watching a skateboard propel a 200lb man up a 25% grade. I just saw that and thought, man, that would be an awesome actuator. All these skateboards come with a belt on each motor and a 1:2 reduction ratio. I just think I probably need more, unless my math is wrong.

we get lots of variety in what people post on this form and the non robotic topics can be anything from electric bikes to animated sculptures.

I am interested to hear more about what you are actually working on, I apologize if it is in your original post but i read it a few times and i'm not quite sure. Drive mechanisms are very interesting subject and i still have a lot to learn. I toyed with a few ideas in the past to create low cost high performance drives for robotics but never went anywhere with them.


29
Misc / Re: Can hobby roboticists save A Country's industry?
« Last post by cyberjeff on August 26, 2015, 09:09:23 PM »
8) Awesome input!
I am exploring my own leg system, and it is quite energy demanding.  :'(
I was hoping some robotic tech could create a humanoid robot (like Chappie) to
do the manual labor.(Farming, small business labor)  ;)

I've spent a lot of time studying cats lately, what their skeleton looks like and how they move. So, I have a very good idea of why they are built the way they are and why the skeleton moves as it does. A good bit of why quadrupeds are stable on 3 legs has to do with where the center of gravity is. The weight of the head and neck brings this forward to not far behind the shoulders. A quadruped can not walk without a head extending out and shifting the CG forward. I've plotted this out on plain old graph paper!

 After plotting footfall patterns for walking I found that the cat is statically stable over a good bit of 3 legged positions, it is at the extremes of the walking gate that momentum must carry through.

Bipeds are different and rely on the foot to be statically stable, it can never statically balance on 2 points. Now, take a look at Mossimo:

https://www.youtube.com/watch?v=-qrLOtgYIWs

Mossimo does not actually walk like a human, the legs never stretch out, and are in fact closer to the rear leg of a quadruped. Note also the large feet (which is unneeded in a quadruped). Note also how it shifts it's torso  back and forward to adjust the CG.

  What I am suggesting is that you plot out leg and body movements and tipping points and see what you discover. You can not build a successful biped or quadruped without the geometry being correct,  the architecture has to follow the math. What happens is that most people build out of what robot parts are available and the geometry and CG gets pushed back in importance where as it should be the first concern, not the last.

With my quadruped I had a real starting point as I went from nature, and what I found is that nature does things for good reasons. We need to consider the why and learn from it.
30
I designed a multistage belt drive a little over a year ago. I used GT2 belts for their anti backlash properties. In hindsight it probably wasn't the best approach to the problem. My opinion is that by the time you add tensioners to the design it creates too many components to be ideal compared to other technologies. When you have multiple stages it is difficult to tension the belts by moving one of the shafts which means tensioning using an idler pulley.

Fair enough.

Harmonic drives are an awesome mechanism; low backlash, high gear ratios, and low weight. they are available  however i think they are still covered by patent so the price is high and the sources limited. I used some steppers with harmonic drives before i think they ran about 1.5K each with encoder. also i think 1:32 is actually a bit low for harmonic drives.

Yup. Freakin patents, man. I see whole servos going on ebay for like $150, but it's all piecemeal. Ratios are weird, no idea how to control them, etc.

if you really need low backlash I recommend looking into cycloidal drives. they are supposed to have low backlash and high reduction ratios. however i have not found a good source for them, i did run across an industrial supplier but i'm sure price is prohibitive there. however they may be a little easier to fabricate than a harmonic drive.

Ugh. Ok. I'll take a look.

I don't see why you need low backlash for a skateboard but to be fair i dont ride one. if your system really only experiences load/torque in one direction this isn't really an issue. if you get rid of this requirement it opens up your drivetrain options considerably.

Hey man, I'm not on the robot forum because I'm building skateboards. The skateboard was just my inspiration. It's pretty impressive watching a skateboard propel a 200lb man up a 25% grade. I just saw that and thought, man, that would be an awesome actuator. All these skateboards come with a belt on each motor and a 1:2 reduction ratio. I just think I probably need more, unless my math is wrong.
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