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i am making a line following robot. i have the option of selecting 11cm and 4cm wheels with 1000RPM and 3000RPM respectively. I want to know the advantages and disadvantages of the options. Please help.

user420528
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  • This is mostly robotics question and we don't do that here. Still I'll give you a pointer. The wheel diameter and the number of revolutions set the speed. With each revolution, the robot moves one wheel circumference. – AndrejaKo Oct 29 '11 at 12:45
  • not an amp or volt in sight. pure robotics. – JustJeff Oct 29 '11 at 17:20
  • i assumed this was a forum for both electronics and robotics. sorry. – user420528 Oct 30 '11 at 04:14
  • It was once called "Electronics and Robots". But now it's just "Electronics" – Rocketmagnet Oct 30 '11 at 11:37
  • @user420528, There is no reason to be sorry. It has been confused before. As you deal with problems involving electronics we are still here to help with it as much as possible, quite a while ago robotics was separated. This had a lot to do with users attempting to form another community and any questions that were asked here were taken from a complete electronics perspective anyway. It seemed the two did not fit perfectly.As a new stack exchange is still slowing moving in the pipes I hope you will help-[Robotics](http://area51.stackexchange.com/proposals/33197/theoretical-and-applied-robotics) – Kortuk Oct 30 '11 at 11:51

1 Answers1

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Summary:

  • About the only advantage I can immediately see in using the small wheels is that a much lower profile design could be built. (Say as low as 50mm versus 120 mm). If this is not an advantage to you I'd say that the large wheels were substantially superior for most purposes.

  • Because (apparently) of different gearbox options both wheels give about the same speed of about 20 kph.

  • The small wheels will result in extremely small ground clearance - perhaps about 10mm in practice.

  • The Large wheels will have perhaps 4 x as much ground clearance - maybe 40 mm+ depending in how much the body underhands the axle.

  • The large wheels will be much better for traveling over rough surfaces, small obstacles, carpet, grass etc.

Looks like two wheel size options paired with two gearbox options so speed and torque are about the same in each case.

Speed = RPM x 1m/60s x diameter x Pi

1000 rpm x 1/60 x 11 cm x 3.14 = 575 cm/s = 5.75 m/s =~ 21 km/hour = fast

3000 rpm x 1/60 x 4cm x 3.14 ~= 6.3 m/s ~= 23 kph = fast

So the small wheels give very slightly more speed and so very slightly less torque BUT there is not much in o=it.

More importantly, the larger wheels will be MUCH better at traveling overs rough surfaces and small obstacles and substantially better ground clearance..

A 4cm dia wheel has a 2cm radius.
If the robot has 1cm of its structure below the axle centre it will have 1cm ground clearance.

A 11 cm wheel has 5.5 cm radius.
With the same 1 cm underhang it give 5.5-1 = 4.5 cm ground clearance.
= 4.5:1 a better than with 4cm wheels.

Unless there were extremely good reasons to do not so I would choose the large wheels.

As this question will be closed on this site - I am at apptechnz gmail com <- add the missing bits.

Russell McMahon
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  • Even when this question gets closed the answer will still be there. You'll be able to edit it and OP can comment. Your e-mail address can be found in your profile (where it belongs), besides, Kortuk would remove it also when he noticed it. :-) – stevenvh Oct 29 '11 at 15:25
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    Just because Kortuk does it it doesn't mean some other Turkey has to upstage him :-). My email address does NOT show in my profile. I can see it. Other users report not being able to. No doubt there is an option somewhere allowing this but I can't find it. SO you have cut this user off from the boats. – Russell McMahon Oct 29 '11 at 15:51
  • Does too, you put it in your description. (The e-mail field itself isn't shown, like you said) – stevenvh Oct 29 '11 at 15:56
  • OK - so I've already worked around the brokenness apparently :-) - now how do I unbreak it so the email address shows? – Russell McMahon Oct 29 '11 at 16:16
  • I was just about asking this in meta! :-) – stevenvh Oct 29 '11 at 16:17