Crawler tracks

Share your building instructions or ask questions about constructing your robot
marcoloca
Posts: 12
Joined: 19 Jan 2012, 16:32

Crawler tracks

Post by marcoloca » 19 Jan 2012, 17:24

(Is it written correctly? :oops: )

Hi again,
I need some explanations about the crawlers. As my teacher said, they're absolutely better than normal wheels in moving on an inclined plane, but there are some things I am not certain about.
We (again, I and my team) build it but sometimes they creak and maybe this means that the robot must spend more energy for moving the engines... What do you think?
Of course, as I said, with wheels the robot will never pass the climb...
I don't know, any suggestions?

Thank you all who will answer me soon!

mattallen37
Posts: 1818
Joined: 02 Oct 2010, 02:19
Location: Michigan USA
Contact:

Re: Crawler tracks

Post by mattallen37 » 19 Jan 2012, 22:35

Tracks often do introduce more friction than wheels, but are often easier to design for. With tracks, you can easily make a skid-steer, and all motor power can go to driving the tracks (you don't need to waste resources for a steering motor). Wheels often have a large diameter, making them harder to drive (you need torque, which means more tolerance issues).

Tracks can be the best option, but it depends on the surface you will be driving on, and the tracks/wheels/design you have.
Matt
http://mattallen37.wordpress.com/

I'm all for gun control... that's why I use both hands when shooting ;)

mightor
Site Admin
Posts: 1079
Joined: 25 Sep 2010, 15:02
Location: Rotterdam, Netherlands
Contact:

Re: Crawler tracks

Post by mightor » 20 Jan 2012, 06:36

At my robotics club we have competitions and the robots with the tracks often find themselves unable to make a pivot turn on the rubber mats due to the friction. I've seen tracks split or just come off the little wheels. Keep that in mind :)

- Xander
| My Blog: I'd Rather Be Building Robots (http://botbench.com)
| RobotC 3rd Party Driver Suite: (http://rdpartyrobotcdr.sourceforge.net)
| Some people, when confronted with a problem, think, "I know, I'll use threads,"
| and then two they hav erpoblesms. (@nedbat)

marcoloca
Posts: 12
Joined: 19 Jan 2012, 16:32

Re: Crawler tracks

Post by marcoloca » 20 Jan 2012, 15:13

mattallen37 wrote:Tracks often do introduce more friction than wheels, but are often easier to design for. With tracks, you can easily make a skid-steer, and all motor power can go to driving the tracks (you don't need to waste resources for a steering motor). Wheels often have a large diameter, making them harder to drive (you need torque, which means more tolerance issues).

Tracks can be the best option, but it depends on the surface you will be driving on, and the tracks/wheels/design you have.
Well, I think it's the best option too, because probably (I'm not really sure) the robot will drive on a smooth surface... We already built a track and we need to build the other, but we stopped to think if it's a good choice... It's a track based on three circles (one of them is a bit more high than the others) and it's quite tight [is this a good thing?]

Another thing, do you think we'd better connect all the three "circles" (it's not the right term, I now) to the same motor, or is better to make move only one circle? And if yes, which of the three (anterior, posterior or middle-high)?
mightor wrote:At my robotics club we have competitions and the robots with the tracks often find themselves unable to make a pivot turn on the rubber mats due to the friction. I've seen tracks split or just come off the little wheels. Keep that in mind :)
Sorry, I can't understand what you mean with "on the rubber mats"... You mean that the tracks show problems on a not-smooth surface?

mightor
Site Admin
Posts: 1079
Joined: 25 Sep 2010, 15:02
Location: Rotterdam, Netherlands
Contact:

Re: Crawler tracks

Post by mightor » 20 Jan 2012, 18:14

If the mat provides too much grip, the tracks have trouble turning the robot on the spot. There is too much friction and you end up either running the track off the cogs or, worse, snapping them. I've seen it happen.

- Xander
| My Blog: I'd Rather Be Building Robots (http://botbench.com)
| RobotC 3rd Party Driver Suite: (http://rdpartyrobotcdr.sourceforge.net)
| Some people, when confronted with a problem, think, "I know, I'll use threads,"
| and then two they hav erpoblesms. (@nedbat)

h-g-t
Posts: 552
Joined: 07 Jan 2011, 08:59
Location: Albania

Re: Crawler tracks

Post by h-g-t » 20 Jan 2012, 18:19

Interesting experiment on traction here - http://www.philohome.com/traction/traction.htm
A sophistical rhetorician, inebriated with the exuberance of his own verbosity, and gifted with an egotistical imagination that can at all times command an interminable and inconsistent series of arguments to malign an opponent and to glorify himself.

marcoloca
Posts: 12
Joined: 19 Jan 2012, 16:32

Re: Crawler tracks

Post by marcoloca » 20 Jan 2012, 18:49

mightor wrote:If the mat provides too much grip, the tracks have trouble turning the robot on the spot. There is too much friction and you end up either running the track off the cogs or, worse, snapping them. I've seen it happen.
But, as I said, the surface will be smooth and I think the friction won't be I problem... I hope! However, we have an arena (quite the same of the one of the competition) where we can try robots, maybe I'll try and then I tell you how was the performance...
h-g-t wrote:Interesting experiment on traction here - http://www.philohome.com/traction/traction.htm
Thank you! Very interesting!
I think that the performance will be fine, the data are average good (for what we have to do... It's a junior competition, not a professional one!)

mattallen37
Posts: 1818
Joined: 02 Oct 2010, 02:19
Location: Michigan USA
Contact:

Re: Crawler tracks

Post by mattallen37 » 20 Jan 2012, 20:17

You don't want the tracks too tight. Whether you are using the track links or rubber tracks, you want some slop in them (but not enough to make them slip or come off).
Matt
http://mattallen37.wordpress.com/

I'm all for gun control... that's why I use both hands when shooting ;)

hassenplug
Posts: 346
Joined: 27 Sep 2010, 03:05
Contact:

Re: Crawler tracks

Post by hassenplug » 20 Jan 2012, 21:29

marcoloca wrote:Another thing, do you think we'd better connect all the three "circles" (it's not the right term, I now) to the same motor, or is better to make move only one circle? And if yes, which of the three (anterior, posterior or middle-high)?
The circles are wheel hubs.

Personally, I wouldn't power all three hubs. As long as one hub is turning the track, two or three won't make it turn "more", and adding gearing to connect all three may add friction, which would not be good.

I would connect the motor to the middle hub to give it good ground clearance, but only if the track goes around 90 degrees of the hub. Less than that, and it may slip.

Hope that makes sense.

Steve
---> Link to lots of MINDSTORMS stuff under my picture --->

marcoloca
Posts: 12
Joined: 19 Jan 2012, 16:32

Re: Crawler tracks

Post by marcoloca » 22 Jan 2012, 18:28

hassenplug wrote: The circles are wheel hubs.

Personally, I wouldn't power all three hubs. As long as one hub is turning the track, two or three won't make it turn "more", and adding gearing to connect all three may add friction, which would not be good.
Yes, this make sense, thank you! We'll try this, I think...
I would connect the motor to the middle hub to give it good ground clearance, but only if the track goes around 90 degrees of the hub. Less than that, and it may slip.
Sorry, I don't understand "goes around 90 degrees of the hub"...

mattallen37 wrote:You don't want the tracks too tight. Whether you are using the track links or rubber tracks, you want some slop in them (but not enough to make them slip or come off).
They're not too tight, of course, just enough I think =)

Post Reply

Who is online

Users browsing this forum: No registered users and 2 guests