PDA

View Full Version : Take over the world at 0.45MPH? Not...



Adrenalynn
11-01-2008, 06:32 AM
So I built-up this very pretty Tri Track (Thanks Tyb!) and fired it up with dreams of 24"/sec. The specs apparently are based around some prior motor design. At 12v it's doing about half that. At 7.2v it's lucky to see 8"/sec. 8"/sec? Watch out for snails passing in the fast lane! That's about 0.45MPH for those keeping score at home.

So a little work on the drill press, a little gentle hacksaw application, and I present to you:

Your robot on Lynxmotion motors:

740

Your robot on Banebots motors:

741

Any questions?

Well, yeah, some... :

My biggest concern is whether or not the bearings on the LM cogs sets can handle the load and speed. They feel pretty smooth - I'm betting they can... I ran it for 10+ minutes on one track set and then ultrasounded the cogs and track pieces - they showed no signs of stress. Of course, we won't really know until I get the guts to put it back on the ground and run it for a bit. Another concern is something on the order of 10x the torque too, but that's another story.

Maybe it's the meds, but 101+ inches/sec makes me smile - nay - it makes me cackle with insane glee. You don't even wanna see this thing at 9.6v. *I* don't even wanna see it at 12v (which is kinda reaching the motors anyway).

I have video of the track running with the motor clamped down, but that's not going to be as exciting as putting this on the ground, so I'll try to shoot something new after a nap...

---

Anyone else madly "overclock" their LM TriTrack? You should try it. It'll make you cackle too.

4mem8
11-01-2008, 02:33 PM
Nice testing Adrenalynn, keep up the work, I'm interested in your progress.

Sienna
11-01-2008, 03:02 PM
Ooo! Good timing with this.

I just assembled my Tri-Track (yesterday and today actually), and was running it around on a 3S Lipo for a bit. Needless to say, I too was a little disappointed with the end speed.

Looking forward to seeing possible solutions to make this chassis move (faster)!

4mem8
11-01-2008, 03:18 PM
Depends on what you are using it for, In my case I need it slower.60-80 rpm for my project, and as Adrenalynn has stated just reduce the power to 7.2v for the 12v motors. Which is what I will do for my current project, But not able to do with my J5, as I already have installed a 12v pack and these are hard to get at right now.

Adrenalynn
11-01-2008, 04:33 PM
Thanks for the interest!

First test was a bit inconclusive. My big 7.2v NiMH was reporting 5.9v under no load. My R/C controller was all the way in the red for battery charge and got a little flakey on turning, I suspect. Even so, it was moving about 30"/sec. In a straight line it was crossing the 4' playing field in less than 2sec, flying over the 11/16" quarter-round like it wasn't even there. It was still very controllable.

To see what the actual speed looks like, I'll need to wait for these batteries to charge.

I do want to contact Banebots and find out what temp these motors should be at under moderate load. After 5min they're running about 115deg F (46C) in 68deg F (20C) ambient... I know my big motors get so hot they'll give you 3rd degree burns instantly, but it seems like these are running a bit warmer than I'd expect.

They stall at ~23A @ 7.2vDC. They seem to be running about 11A in a turn, 9A flat-out under ~5lb load. (They're rated for 18A stall @ 9.6v, I think. I'd need to go check their numbers) So the numbers seem pretty reasonable. Don't bother trying to run them on a 2x10 Sabertooth - it can't really deliver the 10A/17A it claims. It goes into over-current protection almost instantly at 9A. I probably need another ESC - right now I'm running it from a 2.5 x 80A RobotSolutions controller, which is AWESOME, but it's a "little" large.

First-test video as soon as I transcode it. New video when my batteries charge.

4mem8
11-01-2008, 05:37 PM
Damn, I just bought a 2 x 5 for this project, got a link to that motor driver you have 2 x 80 amp?

sam
11-01-2008, 08:09 PM
Wow! That looks pretty cool. It kinda puts me on edge with that 101+ inches per second...

You know, when a robot that size can go on the freeway it's not nececerly good. :wink:

Keep us updated, I want to knwo what will happen @ 7.2 volts.

Sam

Adrenalynn
11-01-2008, 08:28 PM
Well, that's 101+ in/sec at no load, which is only a bit under six miles an hour or so. I suspect it'd do a bit better at 9.6v - like maybe be able to maintain 6mph.

Even with the battery at 5v or so it was able to shoot across my 4x4' playing field in one blip of the stick.

I've finished recharging the batteries and reprogramming the motor controller, so I'll take it into the storage room after I eat.

4Mem - you *really* don't want a 2.5x80A controller for hobby motors. Too big and too heavy. It's meant for 300lb battlebot type robots. That thing will burst up to a couple hundred amps for a few seconds. Your 2x5 will work fine for the stock motors. The stock motors work [as well as they can] on my 2x10. These motors really want a 2x25. I just happen to have the 2.5x80 (http://robot-solutions.com/RS2/product_info.php?products_id=29&osCsid=a89087b95e06b59e4ce3c0ed194b07e6)laying around. ;)

4mem8
11-01-2008, 09:28 PM
ok, so my stock 50:1 Lynx motors are ok on my 2 x 10 controller, Sorry I re-read your post and saw the Banebot, different motors you were using to the Lynx. Thanks.

Adrenalynn
11-01-2008, 09:32 PM
Oh yeah, definitely. Yeah, I'm going for something a little more... sprightly.

One thing you will notice down at 75RPM is that the torque isn't there either. It wouldn't climb over a 1x2 on the low side when I tried it.

I haven't shot new video yet, but here's what the practically dead battery looked like (you can see it start to die completely by the end, where it can't even turn well). Even at 5ish volts you can see it really sit up at the beginning of the video.

http://www.jlrdesigns.com/first-test-new-motors.wmv [10MB windows media video]

[edit] Probably also worth noting: I just went over the cogs, tracks, pads, etc with 10x magnification and a bright light - zero sign of wear, everything looks brand new except for one tiny ding on one of the inside nylon push-rivits where it obviously clipped the quarter-round hard. But even that's not noticable at normal magnification.

4mem8
11-01-2008, 09:44 PM
Well, That's good news then Adrenalynn, The track system is good for our designs in hand.

4mem8
11-01-2008, 09:53 PM
Cool video Adrenalynn, So I take it this system will meet your needs for your project?

Adrenalynn
11-01-2008, 09:59 PM
I suspect so. Obviously the proof will be in the practice. I'll want to run it through with fresh batteries in a couple hours, and then finish the rest of the build-out. Realistically, I'll probably need to pick up a smaller motor controller given space constraints. The banebots motors/gearboxes are a fair bit longer, and really chew up the space betwixt the tracks. So another deck or two will be a must. The arm still has to actuate, so I'll probably go with vertical decks. Still a lot of work before I can even start programming. [sigh] But it's definitely getting closer every day! :)

Adrenalynn
11-01-2008, 10:43 PM
These need dialing back a bit at the speed controller. Too quick to be practical in a small space, but they'd be fun for chasing down your least favorite neighborhood cat. ;)

Tri Track doing 0-5mph-0 in a heart-beat: http://www.jlrdesigns.com/vroom.wmv

It IS pretty amusing. :)

sam
11-02-2008, 04:39 AM
Great video! You can even see the tracks are lifting from the ground when going backwards.

I also liked the other video where at the end it died. :veryhappy:

Adrenalynn
11-03-2008, 12:06 AM
Update: After 20 mins of beating on it like you see in the latest video, plus beating on it some more at 9.6v [gasp], the cogs and track show no wear what-so-ever. Not even the barest scratch or ding on the drive cogs. Ultrasound suggests the baseline structure is identical to any precision I can measure it. I can't guarantee long-term viability, but I have very high confidence.

There was one time at 9.6v where I wasn't certain if one of the cogs slipped or the motor controller burped. Given the lack of any visible wear, I suspect it was the later not the former...

For those following along at home, I'm using these Banebots motors (http://www.trossenrobotics.com/store/p/4224-20-1-28mm-Planetary-Gearmotor-RS-385-Motor.aspx). I do want to follow-up with Banebots directly and see what the nominal and max temps are. Since I have a bunch of spare pins, I will probably put a thermister on 'em since they're making me a bit nervous jumping up towards 120F under heavy [non-stall] use...

I think they're a bit under-rated for stall torque which under-rates them for stall-current (or vice-versa if you please) I measure 21A+ stalled, and 270ish oz/in. (n=2, so hardly a good sampling of motors). I've also seen them hit 908RPM @ 7.2v suggesting they spin a little faster too - which would dovetail in with the current numbers and makes a decent double-check against the numbers I'm observing.

As soon as I confirm the heat I'm observing is reasonable, I would strongly recommend these gear-head motors for any project where you can find enough traction to hook 'em up with the surface - and enough weight balance to keep it on the ground.

4mem8
11-03-2008, 12:33 AM
Ha ha, great to watch Adrenalynn, Sure would scare the cat!, Seriously though the heat would be very concerning to me, I hate heat build up anywhere on anything. What will you ultimately end up with motor wise? What speed are you aiming for? Why do those motors get so hot with no or limited load? Are you over powering them? knowing you I doubt it. curious.

farmBot
11-04-2008, 02:49 PM
I bought mine a year ago and got the older motors. I'm satisfied with the speed.

I'm also really impressed with the capabilities of the platform. I did donuts for several minutes in a pile of dirty clothes and never got tangled up. The leaf pile slowed me down since it sank, but it was cool just seeing my camera moving above the surface. And it easily crossed a 3" sweeper hose.

Adrenalynn
11-04-2008, 03:04 PM
Welcome to the forum!

I don't know the specs on the old motors, and you may be running at higher voltage than I'm able to (rule-bound for competition max voltages). The new motors at 75RPM @ 7.2v just wouldn't cut it for me. 75RPM * PI * ~2.5" /60 ~= 10"/sec... Not something that would have worked-out for me.

I agree though that the tracks/cogs/etc are very tough and functional.

Again - welcome aboard!

farmBot
11-04-2008, 03:26 PM
Thanks, looks like a good community.

I never measured the voltage while running, but it's a 7.2V pack. 1600 mAH and it runs for at least half an hours per charge.

Adrenalynn
11-04-2008, 03:52 PM
Nod. That'd give <10"/sec (load will lower the number) on the new motors - but I've heard the old motors were much more spritely.

Not as quick as my new motors though. ;) I can do 81"/sec under 5lbs of load given a second to come up to speed. That's pretty quick - but probably not practical for applications other than those like mine (timed competition)

mallster
11-05-2008, 05:41 AM
Thought this would be a good chance to sneak my first post in.
Have just thrown together a video of lynxmotion 3" tri-track with Banebots 36064-540's (64 to 1 planeterary) running backwards on a fully charged 12v nimh pack. Apologise for the lack of sound and looking at it now maybe should have put a sticker on the track to give some idea of speed.
Will post again once the thing is fully bolted together and the track tensioners are in.

4mem8
11-05-2008, 06:05 AM
Can't read your file for some reason, can you post your video to utube?

Adrenalynn
11-05-2008, 09:53 AM
Windows Media Video 9 inside a Zip. Works ok here.

Welcome to the forum, mallster!

The layout on those is much different than mine - is that an older bot revision or did you build the shorter sidewalls?

4mem8
11-05-2008, 11:38 AM
Damn, I have corrupt winzip files, Uninstalled it and now I cannot reinstall any version of winzip, keeps coming up with WZ.com file needed, that's really weird as that file is there in the registry. Argh software.

jes1510
11-05-2008, 11:55 AM
Give "Winrar" a try. It is pretty good software. I had to start using it on my Vista machine because the unzipping performance of Vista was terrible.

http://www.rarlab.com/

Adrenalynn
11-05-2008, 12:32 PM
7zip is free and will decompress "anything".

http://www.7-zip.org/download.html

mallster
11-05-2008, 04:53 PM
Adrenalynn- Just modified the original tri-track chassis by using the aluminium mounting bars to bolt the motor up a little higher. Planning to make a Wall-e with some sort of actuated suspension set-up.