Page 1 of 3 123 LastLast
Results 1 to 10 of 27

Thread: Suggestions for DC geared motor

  1. #1
    Junior Member Newbie
    Join Date
    Nov 2005
    Location
    Noida
    Posts
    8

    Default Suggestions for DC geared motor

    I am building a wall climbing robot. It is a tracked vehicle(like packbot, talon) but when it encounters vertical surfaces in its path, it shifts to its wall climber mode.

    I have finished a proof-of-concept vehicle. Now, I am planning to build a functional prototype which I can show to the interested parties(companies, VCs, etc) as a product. As this would be the final design, I am taking extreme caution in buying the components for the same, especially the drive motors. I need your advise for the same.

    This is a wall climber so, the weight of the robot is critical. The final machine along with its payload would weigh 40 kgs Max. I am designing the robot with this weight specification. The weight of robot and payload could be traded with each other. This makes the selection of the right motors along with the gear boxes absolutely crucial. I have not been able to find a reasonable buy till now. I have checked markets like Lajpat Rai, Chawri Bazar, Mayapuri, Jhandewalan etc(all are located in Delhi). with no success. Most of the motors that are on sale are industrial in nature and unfit for robotics use.The best solution so far is the rotomag AB2-R with 148 kg-cm torque. The link is http://www.rotomag.com/PM3.htm. But this motor along with the gearbox is heavy(6.5 kg). The dealer was asking Rs 7,200 for it which is not very less than the imported ones with the same specification. Importing motor along with their gearboxes is prohibitively expensive. But, I would buy them if nothing works.

    Someone, please suggest a better alternative(price, places to look for, ratings)? I would be thankful(infact grateful) for the same.

    Motor(attached to its gearbox) requirement specification is:

    No. of Motors : 2
    Weight : 4kg(Max)
    rpm : 30-50
    voltage : 12-24 volts (Note: I will over volt them )
    Torque : 120+ Kg-cm
    HP : Any horsepower that satisfies above specification is ok.
    Email : prashant_chhonker@yahoo.com

    Regards
    Prashant Deep Chhonker

    P.S. : Any suggestions regarding above is welcome and appreciated

  2. #2

    Default Wall Climber

    Hello,
    We have made a Wall Climber project under our mentor docel since 2 yrs. We have presented our paper with the working model in several colleges last year like BMSCE, BIT, PESIT etc.,

    Our climber is aout 3Kgms. It is very difficult to maintain this Bot on the wall even with that weight.
    How do you manage a 40Kg climber on the wall??? We thionk it is very difficult to manage this :!:

    sas87
    avibond
    nag99
    robcop

  3. #3
    Administrator T-1000 vikas's Avatar
    Join Date
    Feb 2004
    Location
    Delhi
    Posts
    1,922
    Blog Entries
    14

    Default

    Have a look at this

    http://www.pololu.com/products/tamiya/0070/

    Produces 15kg of torque at 400:1 gear ratio.Gear Ratios: 4:1 5:1 16:1 20:1 25:1 80:1 100:1 400:1.Motor: RE-260
    RPM: 5040-6300 (5040 Max. Efficiency)
    Voltage: 1.5-3V (1.5V Recommended) (4.5 V max)
    Amperage: .64A
    Stall torque: 15 gcm

    But i would love to ask the same question as sas87 has asked.
    Vikas Patial

  4. #4
    Junior Member Newbie
    Join Date
    Nov 2005
    Location
    Noida
    Posts
    8

    Default

    Hello everyone

    sas87 wrote:
    How do you manage a 40Kg climber on the wall??? We thionk it is very difficult to manage this.
    Yes sas87, your observation is correct. Making 40kg wall climbers is an extremely complex task. But it is very much possible. I am saying it after doing it. The proof-of-concept(POC) vehicle can carry this amount easily(40kg includes it's own weight as well). The bigger challenges are ground to wall and wall to ceiling transitions. Imperfections in real world vertical surfaces (like crevices on walls, curvatures) is another big issue.
    POC's maneuverability is not up to the mark. I wish to correct it in the final product.
    I am writing an article on wall climbing robots. It should be ready by tommorow. Would address all the issues in it.

    Prashant Deep Chhonker

  5. #5
    Senior Member T-1000
    Join Date
    Mar 2005
    Location
    Bangalore
    Posts
    728
    Blog Entries
    7

    Default

    hi..


    just curious..

    but i would like to know what type of wall(i meant the surface) do you plan? and what type of gripping do you have? is the prototype meant for real life situations?

    any way it will be great to see a 40 kg payload up on the wall.
    .... I didnt do it ! ....

  6. #6

    Default

    What about if it falls off ?

  7. #7

    Default Wall climber

    Good question danger if it falls.
    Wall climbers are to replace and avoid danger to humans. 40kgs from a height will be fatal, if it hits anyone. Lots of power is needed to keep the bot attached to the wall. as [/b]allbits asked, it cannot be a "gripping" [b]Robot.
    The gripping involves microclaws and not easy to make. Walls are different even in the same construction practice. A rough wall will need a particular mechanism which will fail if granularity varies. all the mechanisms of grippers are patented and very costly.

    Active Grippers need heavy torque and must be driven by heavy motors. The range of such climber will be very less due to excessive power drain. PM3 motor will not be able to handle the force of gravity which will present downward pull of the weight. The maths and physics will not agree. minimum size of granules on wall willl should be 2mm if the gripper has to stay on the wall. If using welcro type gripper, then the size of grippers should be minimum 200 times the granules needed for grip. this is passive gripper and cannot be dynamic.

    This is our experience and we have dome a lot of work on the Climber. We are still struggling , after 2 years of very hard work :cry:

  8. #8
    Junior Member Newbie
    Join Date
    Nov 2005
    Location
    Noida
    Posts
    8

    Default

    Thank you everyone for the response.

    but i would like to know what type of wall(i meant the surface) do you plan? and what type of gripping do you have? is the prototype meant for real life situations?
    I am designing this machine for fire-fighting and military purposes (not for home or industrial use) and plan to sell it commercially. So, it should and would be able to climb surfaces like walls, wood, glass etc.

    Good question danger if it falls.
    Wall climbers are to replace and avoid danger to humans. 40kgs from a height will be fatal, if it hits anyone.
    Sas87, many thanks for sharing your experiences.

    Yes, even a 3 meter fall would be fatal for the machine and any human that happens to come in the way. But, all engineering systems are designed with certain tolerances and whenever they are exceeded, accidents happen (like in case of aircrafts, cars even computers).
    Anyway, I am designing this system for fire-fighting and military purposes (these are emergency situations). Accidents can be avoided by planning operations before hand.

    “Our climber is about 3Kgms. It is very difficult to maintain this Bot on the wall even with that weight.
    How do you manage a 40Kg climber on the wall??? We thionk it is very difficult to manage this ”
    First of all let me tell something about my robot.
    Vacuum based suction is the primary mechanism through which the robot would stick on the wall.
    Let's briefly discuss the theory behind this mechanism:

    Atmospheric pressure is the pressure above any area in the Earth's atmosphere caused by the weight of air. Standard atmosphere (atm) is a unit of pressure and is defined as 1.033 227 452 799 886 kg-force/cm2.This tells us that 1 cm2 area will experience a force of 1kg if it has vacuum on one side and atmosphere on another. Similarly 100 cm2 area would experience 100kg and so on. All the suction based wall climbers use this force to generate friction (or grip) between gripper and the vertical surfaces.

    Reference: http://en.wikipedia.org/wiki/Atmospheric_pressure

    This tells us that larger the surface that holds the vacuum, the larger would be force on it. Higher force means increased friction and better grip. The total area under the grippers of my robot is 300cm2 . I think this answers the query, how 40 kg can be supported on the wall.

    In case, the primary suction mechanism starts to fail (due to reasons like crevices, sharp curvatures, obstacles, smoothness or lack of it etc.) another drill based gripper mechanism kicks into action. This drill based backup provides exceptionally reliable grips on the wall (just drill a hole with a battery operated hand drill and put a nail inside and see how much weight can a single nail sustain before it bends or before the plaster comes off).

    PM3 motor will not be able to handle the force of gravity which will present downward pull of the weight.
    PM3 motor is absolutely useless as far as robotics is concerned (may be find some use in an industrial robot). By posting information about it, I wanted to tell that I couldn’t find a better one.

    Regards
    Prashant Deep Chhonker

    P.S.: I cannot discuss the design details because of IPR issues.

  9. #9

    Default

    Well that explains. We are using similar techniques. We are building fail-proof systems which will take the payload to 6kgs max.
    But drilling may be a problem before losing grip. The drill will try to push the vehicle away from the wall. But 40 kgs is still toomuch!

  10. #10
    Junior Member Newbie
    Join Date
    Nov 2005
    Location
    Noida
    Posts
    8

    Default

    Hi
    But drilling may be a problem before losing grip. The drill will try to push the vehicle away from the wall.
    As I mentioned in my earlier post, the area under the vacuum is 300 cm2. This gives me a combined downforce of 300kg on the surface of the grippers. This translates into the 300 kg force on the robot itself. Out of these 300kgs I can take few kgs of force to drill effectively(no issues).
    Well that explains. We are using similar techniques. We are building fail-proof systems which will take the payload to 6kgs max.
    But 40 kgs is still toomuch!
    Well, let's say you acheive your 6kg target. Then make 7 copies of your robot and combine them to get a total payload of 42kgs!!!
    By above, I mean that design, size and other factors decide the final payload.
    Sas87, can you send me the final report you made for the colleges. I would be able to answer your queries in a better way.

    Prashant Deep Chhonker

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •