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ashwinmudigonda
04-29-2008, 01:47 PM
Hi all,

I want to build a track bot that will follow me wherever I go. I have the big picture in mind; I am starting to iron out the details.

I am interested in this chassis:

http://www.trossenrobotics.com/store/p/3172-Robby-RP5-Chassis-Only.aspx

My question is what other motor related parts will I need to get to get a differentially steerable track bot?

Adrenalynn
04-29-2008, 01:54 PM
I don't think the chassis you're looking at is a "follow you wherever you go" kinda chassis. Unless you go really slow over flat ground without obstacles larger than a few tenths of an inch. ;)

Can you define your "big picture" better. You're not actually thinking about walking down the street, over curbs, up stairs, anything like that, right?

ashwinmudigonda
04-29-2008, 02:07 PM
The bigger picture is that I will build a Laundry Bot (to carry my load) with bigger tracks that will use the successful firmware I would have developed on this scaled track.

For now, I want this to follow me as I walk down the corridor of my office.

Adrenalynn
04-29-2008, 02:19 PM
I would suggest looking at something larger. These are very small and very limited. I first looked at them for Robocross. They use the tiny little plastic tamiya gear box motors, as memory serves.

Droid Works
04-29-2008, 02:25 PM
You probably want something more like this for tracks: http://www.trossenrobotics.com/store/p/5167-Track-3-Wide-x-21-Links.aspx

Unless money is no object then you want this:
http://www.trossenrobotics.com/store/p/3173-MMP-30-Mobile-Platform-2-Motor-Tracked-.aspx

ashwinmudigonda
04-29-2008, 02:33 PM
Well, money is an object! The first link is only of the tracks. Where could I find a chassis to wrap it around?

Adrenalynn
04-29-2008, 02:35 PM
Look at the bottom of that page for "related items" and you'll find the sprockets and the idler. From there, you'll start looking at the motors and motor controllers.

Please save yourself some additional pain, and avoid the Traxster.

What is your budget for the base portion, btw?

Droid Works
04-29-2008, 02:39 PM
Well, money is an object! The first link is only of the tracks. Where could I find a chassis to wrap it around?
You could buy a piece of aluminum, a couple motors and other odds and ends to make one your self or. buy a pre made one like this: http://www.lynxmotion.com/Product.aspx?productID=577&CategoryID=109

ashwinmudigonda
04-29-2008, 03:26 PM
Thanks for those leads, guys. This community really is worth the time. I was wondering how to figure this stuff by myself.

Well, I have a PIC board and few PICs lying around here at work. So I figured about 100-200$ should do for a small prototype 'bot. I just wanted to get back to Bot firmware development and I thought this would be a cool project to start from. I work at a place where if a "product" is sufficiently innovative (or marketable), I could beg for some more money to make it happen. But for now, I am on my own.

Maybe, this is the time to learn to use the CNC machine the Aero-boys have been bragging about!

Another question I have: To control the motor, won't I need some sort of encoder?

Droid Works
04-29-2008, 03:31 PM
Thanks for those leads, guys. This community really is worth the time. I was wondering how to figure this stuff by myself.

Well, I have a PIC board and few PICs lying around here at work. So I figured about 100-200$ should do for a small prototype 'bot. I just wanted to get back to Bot firmware development and I thought this would be a cool project to start from. I work at a place where if a "product" is sufficiently innovative (or marketable), I could beg for some more money to make it happen. But for now, I am on my own.

Maybe, this is the time to learn to use the CNC machine the Aero-boys have been bragging about!

Another question I have: To control the motor, won't I need some sort of encoder?

Allot of us own our own CNC machines they have really come down in price. If your ever in the market for one this is a pretty good deal.This is the one I use :
http://www.sherlinedirect.com/index.cfm?fuseaction=product.display&Product_ID=185

Adrenalynn
04-29-2008, 03:39 PM
Another question I have: To control the motor, won't I need some sort of encoder?

I noted a motor controller above. Two options: A motor controller that accepts serial or similar and the second option is a motor controller that accepts servo input, and a servo controller.

Of course, you can also go into continuous rotation servos, and skip the motor controller and go straight to a servo controller.

I personally like the flexibility I get from straight motors with a motor controller

Encoders come into play when you want the motors to tell you how far they've gone by counting shaft revolution.

I had a parts list together for an order I'm about to place here that would have everything needed except the metal (which could just be a flat sheet) for a two wheel drive/front caster design.

Alex
04-29-2008, 04:06 PM
Have you seen the ridiculously cool RoboTrax XL yet?

http://www.homebot-robotics.com/Purchase.html

Adrenalynn
04-29-2008, 04:47 PM
It does look insanely cool, but I couldn't find anything resembling specs?!?

metaform3d
04-29-2008, 05:36 PM
It does look insanely cool, but I couldn't find anything resembling specs?!?Here (http://www.homebot-robotics.com/uploads/RoboTrax_Datasheet.pdf)?

LinuxGuy
04-29-2008, 05:57 PM
Of course, you can also go into continuous rotation servos, and skip the motor controller and go straight to a servo controller.

I personally like the flexibility I get from straight motors with a motor controller.
I agree completely. I needed to convert W.A.L.T.E.R. to using motors when he gained too much weight for the CR servos to handle moving around. These motors I am using now will be fine for the duration, I think. I will still have to keep things at 1/3 speed for quite awhile after W.A.L.T.E.R. goes operational again, which I hope will be before September, so I have some testing time.

8-Dale

Adrenalynn
04-29-2008, 06:46 PM
Can't say where you found it - but nice find!

I think I'd take Lynxmotion's far more modular system in a heartbeat.

- Variable length vs fixed length
- Variable torque/speed vs pre-determined torque/speed
- Exposed construction vs unknown construction
- Multi-section track that's repairable vs monolithic track of unknown reliability
- Less expensive including lexan platform vs more expensive excluding platform [in kit form]

I'm thinking it's much less uber-cool than it appeared at first blush.

Alex
04-29-2008, 08:24 PM
it's just too bad that lynx doesn't make a more heavier duty version (ie. non-lexan) of these modular tracks. We would see some really bad ass robots then.

Adrenalynn
04-29-2008, 08:38 PM
Agreed - but do you think the rubber on that robotrax looks tougher?

JonHylands
04-30-2008, 08:42 AM
It would be trivially simple to replace the lexan panels on the Lynxmotion kit with something much stronger, like say 1/8" aluminum.

I just measured the side panels on BrainBot's tracks, and they are 8.75" long and 3.75" high, so I could mill a new set out of aluminum plate on my Sherline CNC mill. And of course, as soon as you can do that, you can start messing with the configuration of the sprockets, and end up with something more like the robotrax kit if you prefer that arrangement.

- Jon

Alex
04-30-2008, 08:52 AM
Agreed - but do you think the rubber on that robotrax looks tougher?It "looks" tougher, but there's no way to know for sure unless we had them side by side. I still totally agree with you with your points on why the Lynx trax are better.



I just measured the side panels on BrainBot's tracks, and they are 8.75" long and 3.75" high, so I could mill a new set out of aluminum plate on my Sherline CNC mill. And of course, as soon as you can do that, you can start messing with the configuration of the sprockets, and end up with something more like the robotrax kit if you prefer that arrangement.


The plates would be fairly easy to mill, yes. But I'm talking about a purely, non-plastic modular track system (gears, plates, tracks (but with some grip element applied), etc.); Not a whole platform to mount a robot on, simply modular tracks that can be mounted on any robot/platform. We've been wanting to see someone/some company build this for quite some time so that we could stock it:D

ashwinmudigonda
04-30-2008, 10:13 AM
Steering this back to my situation, I have decided to get the motor and track package and build my own chassis. I will attempt to control the robot by using feedback from 2 spaced IR receivers which will track the transmitter worn by me. I am in a dilemma between the GM8 & GM9.

http://www.trossenrobotics.com/store/p/5336-Gear-Motor-and-Tread-Package-GM8.aspx
http://www.trossenrobotics.com/store/p/5337-Gear-Motor-and-Tread-Package-GM9.aspx

Both are similar in performance but markedly different in construction. Is there an advantage of one over the other?

Alex
04-30-2008, 10:54 AM
Steering this back to my situation,

Sorry about that. I think we all have ADD here or something (including myself);) With all the brilliant minds here, each of us gets a flood of ideas and have a tendency of hijacking threads.

It's great to hear you came up with a decision!

Adrenalynn
04-30-2008, 11:26 AM
Those look like the same tracks as are on the Traxster (Alex/Dave can confirm?)

Due to their fragility, I strongly suggest you consider a different solution. This is from my own experience with _three_ sets of those tracks (assuming again that they're the same as the Traxster tracks)

Alex
04-30-2008, 01:05 PM
Those are the same tracks as are on the Traxster. But the Traxster comes with metal sprockets (or are the called cogs?) whereas the GMTP comes with plastic. What was your weight limit for this version of your bot?

LinuxGuy
04-30-2008, 01:15 PM
Those are the same tracks as are on the Traxster. But the Traxster comes with metal sprockets (or are the called cogs?) whereas the GMTP comes with plastic. What was your weight limit for this version of your bot?
They are called sprockets. :happy: The Lynxmotion tracks (http://www.lynxmotion.com/Product.aspx?productID=577&CategoryID=109) are supposed to be able to handle at 50 - 100 pounds.

8-Dale

Adrenalynn
04-30-2008, 03:07 PM
I was running a 4lb 2oz Traxster. I had posted my experiences in another thread. Beautiful 'bot until you get to the tracks that can't even handle the torque put out by the Traxster's motors (in my experience of n=6 tracks)

Sorry - short message, they're calling my flight (on a whirlwind US tour to get back in time for Maker Faire)

devilDroid
05-02-2008, 07:16 AM
Allot of us own our own CNC machines they have really come down in price. If your ever in the market for one this is a pretty good deal.This is the one I use :
http://www.sherlinedirect.com/index.cfm?fuseaction=product.display&Product_ID=185

drool~~

devilDroid
05-02-2008, 08:04 AM
They are called sprockets. :happy: The Lynxmotion tracks (http://www.lynxmotion.com/Product.aspx?productID=577&CategoryID=109) are supposed to be able to handle at 50 - 100 pounds.

8-Dale

Just read through the thread and wanted to confess that I'm thinking about doing something similar.

We bought two junked wheelchairs a while back with building an RC lawnmower in mind. We recently questioned the original purpose, though. Our yard is two acres. It would take one of us hours to mow it with a bot and result would never look as good as when the guy across the street does it.

So now I have motors looking for a purpose.

I read about ashwinmudigonda's follow-me bot idea in the Introduce Yourself thread and thought it sounded really cool. I could skip the RC idea and delve straight into self-computed motion. For it to be the most useful, I'd like to be able to use it indoors and out, for housework and gardening. It would have to be able to go up indoor, wooden stairs without trashing the varnish.

Anyway, not trying to be a copy-cat or to hijack the thread. Just thought I'd let you guys know that I'm lurking. Oh and the Lynxmotion tracks look really, really cool. :)

Adrenalynn
05-02-2008, 08:57 AM
Even the lynxmotion tracks would not appreciate something with the torque of wheelchair motors unless massively derated (by dropping power). Those wheelchair motors have a TON of torque...

How about off-road tires?

Feel free to make another thread and we'll all chime in, just like this one... ;)

ashwinmudigonda
05-02-2008, 09:18 AM
Hey devildroid, glad to find a companion in distress! I am ordering the track kit today. I hope to keep pictures and the code open to all. Let's see where it goes. I am sure I will run into obstacles when I design the follow me part.

devilDroid
05-02-2008, 12:50 PM
Hey devildroid, glad to find a companion in distress! I am ordering the track kit today. I hope to keep pictures and the code open to all. Let's see where it goes. I am sure I will run into obstacles when I design the follow me part.
Yay! I can learn from *your* mistakes. It's so much cheaper that way. >;)

devilDroid
05-02-2008, 12:52 PM
Even the lynxmotion tracks would not appreciate something with the torque of wheelchair motors unless massively derated (by dropping power). Those wheelchair motors have a TON of torque...

How about off-road tires?

Feel free to make another thread and we'll all chime in, just like this one... ;)
Good ideas. Thanks!

LinuxGuy
05-02-2008, 02:30 PM
Even the lynxmotion tracks would not appreciate something with the torque of wheelchair motors unless massively derated (by dropping power). Those wheelchair motors have a TON of torque...
I can attest to that! Mine got me stuck almost all the way under my computer desk and I couldn't get free until the neighbor upstairs came and helped me. That's the one time I was greatful I had left my door unlocked. My abdomen hurt for almost two weeks afterwards. I couldn't reach my phone either.

8-Dale

devilDroid
05-04-2008, 09:13 AM
I can attest to that! Mine got me stuck almost all the way under my computer desk and I couldn't get free until the neighbor upstairs came and helped me. That's the one time I was greatful I had left my door unlocked. My abdomen hurt for almost two weeks afterwards. I couldn't reach my phone either.

8-Dale
You use a wheelchair? Have you made any modifications to it--upgraded the tires, etc--so that it can better navigate multiple terrains? Can you climb steps with it?

I'm half thinking about leaving the wheelchair as-is for the chassis.

Adrenalynn
05-05-2008, 10:28 AM
You could probably do much worse for a chassis. Nicely balanced, the batteries are already fixed where they probably ought to be, good strong sturdy production frame, drive system already worked-out... I can see a lot of benefits.

LinuxGuy
05-05-2008, 11:59 AM
You use a wheelchair?
Yes, when I need it, I use it. No stair climbing ability. Luckily though, all our city buses are lift or ramp equipped.


Have you made any modifications to it--upgraded the tires, etc--so that it can better navigate multiple terrains? Can you climb steps with it?
I don't think the one I have is one that can be easily modified. It has two casters front and rear (total of 4) with center wheel drive. The casters would have to be modified to change the center wheels if the wheels are larger than the originals. My chair is not usable now though, and I need it due to balance issues. :(

8-Dale

devilDroid
05-06-2008, 08:23 AM
Thanks so much for the input. :)

jes1510
05-08-2008, 11:19 AM
I bought this chassis (http://www.trossenrobotics.com/store/p/3172-Robby-RP5-Chassis-Only.aspx) to replace a broken one on a small robot and received it yesterday.

I am pleasantly surprised. The motors seem to be of a good quality and very "Torquey". It comes with a 6 x AA cell battery holder that is perfect for small machines. The base seems very stable and able to climb a fairly steep grade using the 6 cell power supply. Ground clearance is about 1/4" so it isn't going boulder hopping but it seems just about perfect for small indoor robots.

I was using a tamiya tread kit and the dual motor gear box for the chassis on my indoor robot. I had around $30 in parts in the chassis and many hours of tears designing and putting together the chassis. I really wish I had found this one first. The price is reasonable and shipping was very fast.

Thumbs up!