Heavy-weight robot with tank treads.

Dave SDave S Posts: 22
edited 2004-12-07 - 14:20:19 in Robotics
Ok, I think my next project, which will be my first significant robot, will be a dual tank-tracked "heavy-weight" bot.· I am custom building a full aluminum chasis, this bot will carry a 12V (small UPS battery) that might way in the area of 2-4lbs. Down the road, this might need a larger UPS battery, around the 10lb mark.· Now, I need motors, and gearboxes that could move this.· The tread will be custom, not sure what they will be made from yet.

Basicly, I dont know what I should use to move this.· There is a dual motor/gearbox here http://www.robotstore.com/catalog/display.asp?pid=229·that claims, when geared high can put out 941 torque g/cm at·3 volts, (203:1 ratio).· I have no idea if thats enough, or should I be looking for 1500+ g/cm?

Any ideas?

Thanks
Dave

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2004-09-16 - 16:14:23
    Dave,

    ·· I don't think that product will work for you...I've seen it before, and the gears are all plastic.· That's great for bots a little larger than the BOE-Bot, but not by much...And since you're going to be driving tank-treads, you're going to need something stronger.



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    Chris Savage

    Knight Designs
    324 West Main Street
    P.O. Box 97
    Montour Falls, NY 14865
    (607) 535-6777

    Business Page:·· http://www.knightdesigns.com
    Personal Page:··· http://www.lightlink.com/dream/chris
    Designs Page:··· http://www.lightlink.com/dream/designs
    ·
  • JavalinJavalin Posts: 892
    edited 2004-09-16 - 16:55:31
    have a look at www.lynxmotion.com, on the gear head motors. I have used the GHM-12, at 12v and it is quite powerfull. Unloaded the current draw is about .1 amps, rising to about .5 / .75 amps at heavy load. Additionally they sell tires, and mounts etc.

    The Motor Mind C controller works well with these also.

    james
  • Dave SDave S Posts: 22
    edited 2004-09-16 - 17:29:42
    that is rated at 138oz/in torque. Anyone have any formulas they would like to share that could help my calculate how many oz/inch power I will need to move, for example 10lbs, without stressing the motors?
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2004-09-16 - 19:35:50
    Dave,

    ·· Until you have the frame designed and/or built, and know the weight of the tank-treads, you will be hard-pressed to come up with accurate figures as to how much weight you'll be moving, or how much torque will be required to move it.

    ·· I once built a robot with tank-treads I got from a toy, and although my bot was within the weight specs for the motors, and seemed to be within the torque specs for the motors, I found that driving the tank treads required more torque than driving wheels.



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    Chris Savage

    Knight Designs
    324 West Main Street
    P.O. Box 97
    Montour Falls, NY 14865
    (607) 535-6777

    Business Page:·· http://www.knightdesigns.com
    Personal Page:··· http://www.lightlink.com/dream/chris
    Designs Page:··· http://www.lightlink.com/dream/designs
    ·
  • Dave SDave S Posts: 22
    edited 2004-09-16 - 22:51:56
    Ok, when I say tank treads, I do mean a rubber/elastic type material about 36-42" long, creating about 1-1.5' of tread on the ground at any given time.

    I am going to start fabbing the aluminum frame this weekend, for reference, this bot will be basicly as large as a large shoebox, but with the 5axis robotic arm, and other stuff like my wireless video cam, the overall weight will quickly shoot up.

    Imma model a mock verson what I project it will look like, ill post pics, if anyones interested.. hehe

    thanks
    dave
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2004-09-16 - 23:25:03
    Sure, post away!· Might make it easier to help you figure stuff out if you also include dimensions.· Given what you said, I definately think that motor/gear box you mentioned wouldn't be enough.· If you're talking large shoe box for size, and you account for treads a little in front and behind, you could well be talking 3' of tread per wheel...I have seen some 12V motors with gear reduction that would work, but the ones I speak of may not be where I saw them anymore...Lemme check...

    Okay, the specs are a little different than I thought...Go to:

    www.bgmicro.com (A surplus house)

    And select the category MOTORS, and check out part# MOT1011



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    Chris Savage

    Knight Designs
    324 West Main Street
    P.O. Box 97
    Montour Falls, NY 14865
    (607) 535-6777

    Business Page:·· http://www.knightdesigns.com
    Personal Page:··· http://www.lightlink.com/dream/chris
    Designs Page:··· http://www.lightlink.com/dream/designs
    ·
  • Dave SDave S Posts: 22
    edited 2004-09-17 - 00:11:36
    Might have a change in plans, for starters, I think I may stick with 4wd (RC truck tires) and down the road, change over to tread, if the bot proves to be a success. But weight still is there, the bot will be 100% aluminum, which isnt bad, but isnt plastic either.

    Got a general question, I was wondering if a single Motor Mind C, could control 4 DC motors in pair (left/right)

    http://www.parallax.com/detail.asp?product_id=30001
  • cabojoecabojoe Posts: 72
    edited 2004-09-17 - 03:04:13
    I believe you would need two Motor Minds to accomplish that. And Chris is spot on about that gearbox, it's for toys.
  • WNedWNed Posts: 157
    edited 2004-09-17 - 17:07:07
    ·· For motors, you might want to try getting a set of electric window drives from a junk yard. They're 12v motors with·decent gearing and torque (sorry, I don't have exact specs.)
  • Dave SDave S Posts: 22
    edited 2004-09-17 - 19:02:27
    A few coworkers here suggested some cheap portable drill motors, but I dont know if these will give me the RPM's im looking for, my goal is to have the bot move at ~1-2ft per second, and judging from my windows, the bot would be moving more like 3-4 inches per second with that drive, unless I can regear it, which might end up costing more, and larger than just getting a spur geared robotics motor..

    Hopefully this weekend ill have my basic frame assembled, and will have a better idea with what I am dealing with.

    If the project goes as planned, it will have a robotic arm on its deck, with the ability to pick up, and carry a payload on its upper deck.

    I could see this taking months to complete, with my current workload at the office.. but a hobby is a hobby!

    [noparse]:)[/noparse]
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2004-09-18 - 00:29:05
    Dave,

    ·· Most of my projects end up taking months, just becauseof the lack of time I have to devote to them all! eyes.gif

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    Chris Savage

    Knight Designs
    324 West Main Street
    P.O. Box 97
    Montour Falls, NY 14865
    (607) 535-6777

    Business Page:·· http://www.knightdesigns.com
    Personal Page:··· http://www.lightlink.com/dream/chris
    Designs Page:··· http://www.lightlink.com/dream/designs
    ·
  • Dave SDave S Posts: 22
    edited 2004-09-18 - 14:51:50
    Hey

    I am interfacing a Analog joystick (Flightstick Pro, 1995) with my javlin, and I· have the X/Y axis working perfectly..

    Using http://www.parallax.com/dl/appnt/jav/class/AppnoteAnalogJoystick.PDF· for help, I cannot figure out how to get the buttons working.· The class has support fo buttonX and buttonY, butwhen I run the program, debug says buttonX is not pressed, and Y is always pressed, and no matter what··button I press, nothing changes.· The joystick has 3 buttons onstick, a 4 dir top-hat, and a trigger.

    Any ideas?· Is it possible that I need·to change the pins· around from the DB15F on the joystick to other· pins?

    Any hints?

    Jon Williams wanna jump· in· on this?? :-)
  • Dave SDave S Posts: 22
    edited 2004-09-20 - 11:18:15
    Chris,

    I was looking at those motors on bgmicro, you think 15RPM would be too slow?· The bots chassis (built already) is 16"x12"x5" rectangle 100% aluminum, very light at this point.· Add a 8lb battery (12V battery backup), a few lbs of motors, and tank treads..

    I cant find any calculator that can determine speed using tank treads, only wheels.· 4RPM at 3 volts, seems ungodly slow, but I dont know how that translates into treads..
    ·
  • JavalinJavalin Posts: 892
    edited 2004-09-20 - 12:49:18
    surely the tread speed is the same as if you were using wheels? If the motor is driving a 3cm diameter hub with a track on it, the track will move at rpm * (3cm * pi) = meter/minute?
  • Dave SDave S Posts: 22
    edited 2004-09-20 - 16:11:24
    Was that a question? hehehe track wouldnt be on anything less than 2 inches, anything smaller would make the bot pretty fragile.

    So, if the tracks ran on a 3 inch disc. That would equate to 141 inches per minute, or 2.3" per second. Eek, I need something like 30-50rpm, at that rate. I want the bot to be able to go REALLY slow, but also speed up to about 6-9" per second.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2004-09-21 - 00:00:48
    Dave,

    ·· There are no constants when working with RPMs alone, in terms of speed...The output shaft may rotate at 15 RPM, but, the speed of the unit will depend on the size of the gear or wheel attached to the shaft.· The gear or wheel, which will be driving the tank treads will affect the speed, based on it's size.· A larger wheel/gear will make the unit move faster.· A smaller one, slower.· So while the RPM is constant, the speed isn't, necessarily.

    I hope that helps.· And I was showing you one example of something that could work, I have actually seen many units similar to that one which were metal gearing and enclosures, designed to drive heavier loads than that one you asked about.· Hope that helps!·

    cool.gif

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    Chris Savage

    Knight Designs
    324 West Main Street
    P.O. Box 97
    Montour Falls, NY 14865
    (607) 535-6777

    Business Page:·· http://www.knightdesigns.com
    Personal Page:··· http://www.lightlink.com/dream/chris
    Designs Page:··· http://www.lightlink.com/dream/designs
    ·
  • Dave SDave S Posts: 22
    edited 2004-09-21 - 00:29:33
    I think I might give them a whurl.. I got to start somewhere, and at 10$, its worth a shot.

    Ill try two, see how good it moves, and if its fast, but lacks power, Ill run 4 of them.

    My biggest obstacle at this point is fabbing heavy duty treads.. all toy treads are plastic and small, so it almost has to be completely made from scratch..
  • Dave SDave S Posts: 22
    edited 2004-09-21 - 00:30:29
    Also, the chassis weighted in at 1 lb 2.2 oz.. I was pleased with that, it looks large, but is really light weight, and its really strong
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2004-09-21 - 20:16:45
    Dave,

    ·· Remember, 4 motors will draw alot more juice than 2 motors...With the weight you posted, if you can keep the tread weight down, you should be okay, depending on the speed.



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    Chris Savage

    Knight Designs
    324 West Main Street
    P.O. Box 97
    Montour Falls, NY 14865
    (607) 535-6777

    Business Page:·· http://www.knightdesigns.com
    Personal Page:··· http://www.lightlink.com/dream/chris
    Designs Page:··· http://www.lightlink.com/dream/designs
    ·
  • Dave SDave S Posts: 22
    edited 2004-09-21 - 20:31:02
    I figured that, Id start with two high torque motors that you mentioned before, they are a good start. The battery is a 10lb battery back ups from a APC system 12V 12Ah (GP 12120 F2)
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2004-09-21 - 22:56:58
    Well, good luck with the project.· If you have anymore questions, just ask.· Please post pictures if you can of your frame and stuff when you get the chance too...Might inspire some others!

    idea.gif

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    Chris Savage

    Knight Designs
    324 West Main Street
    P.O. Box 97
    Montour Falls, NY 14865
    (607) 535-6777

    Business Page:·· http://www.knightdesigns.com
    Personal Page:··· http://www.lightlink.com/dream/chris
    Designs Page:··· http://www.lightlink.com/dream/designs
    ·
  • macmanmacman Posts: 20
    edited 2004-09-22 - 16:08:30
    For what it is worth, several guys on the Yahoo Robotics Forum have been praising a 1/6 scale Stuart tank from Wal-Mart which retails for around $150 .
    The body is constructed from 1/8" plastic with solid plastic tread sections held together with steel pins, apparntly it is very suitable to hack, once top shell is removed there is plenty of space. I believe there is a review of one such conversion in the Servo magazine.
    If you really want more info I could try and find more details for you.

    Sounds like the makings of a cool project.

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    Regards Nigel

    Success is the ability to go from one failure to another with no loss of enthusiasm.
    Winston Churchill
  • Tom WalkerTom Walker Posts: 509
    edited 2004-09-22 - 17:38:15
    I believe that the tank was given the once-over in the September issue of SERVO.

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    Many are cold...

    · but few are frozen...
  • macmanmacman Posts: 20
    edited 2004-09-22 - 17:57:51
    Hi Tom,
    Thank you for the clarifaction, yes that is the model I was referring to, couldn't remember the issue though.

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    Regards Nigel

    Success is the ability to go from one failure to another with no loss of enthusiasm.
    Winston Churchill
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2004-09-23 - 22:14:12
    Is there an online source of this information?

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    Chris Savage

    Knight Designs
    324 West Main Street
    P.O. Box 97
    Montour Falls, NY 14865
    (607) 535-6777

    Business Page:·· http://www.knightdesigns.com
    Personal Page:··· http://www.lightlink.com/dream/chris
    Designs Page:··· http://www.lightlink.com/dream/designs
    ·
  • ToadToad Posts: 5
    edited 2004-12-05 - 16:58:51
    hi uys...as for the tank treads ..i have a bot that uses Harley-Davison triplex chains as treads ..I used greas to match the pitch and for motors I used the gearbox from a riding toy car...power wheels was the name of the company that makes them.......it all runs on a 1/8th inch aluminium frame...it was useing a Apple II motherboard--(old project) which I took off and am now setting it up for the Stamp Boe.....

    this set up can push a kitchen chair...easy...

    I think the drive ratio is about 400 to 1.....
    hope this helps
  • Tronic (Greece)Tronic (Greece) Posts: 130
    edited 2004-12-07 - 14:20:19
    Have a look on this 4 Kgr weight tank i made last weekeed!
    Is has two simple hacked servos to move it around...
    And of course BS2!!

    more pics and videos on this link:
    greekbotics.com/robot/forum_viewtopic.php?13.5237.40
    640 x 480 - 79K
    640 x 480 - 78K
    640 x 480 - 74K
    640 x 480 - 78K
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