A friend of mine gave me one of these, and I immediately looked it up, but can’t seem to find any real specs on it. I know I would have to gear it down significantly to use it in a robot.
What would be the best way to gear two of these down for robot use?
Would one of the Sabertooth 2x5 R/C controllers handle two of these or would I need the 2x10 R/C?
8-Dale
wat i would suggest is a RC truck differential from traxxas
KISS, why make it harder on yourself then it has to be?
wat kind of specs does the motor draw? or is that wat ur trying to figure out?
Yes, indeed, easier is preferred to harder. 
This is what I am trying to figure out, so I can get the appropriate motor controller for two of the Stingers. It might be fun to put these on W.A.L.T.E.R. but it would probably be extreme overkill. 
Now I am wondering if one of these Stinger motors would work for a two wheeled robot like W.A.L.T.E.R… If one wheel is set to drive forward and the other is set to drive backwards under normal conditions, controlling the speed and direction of the motor should allow the wheels to be synced up for forward, reverse, and turning. Does this sound workable? I want to convert W.A.L.T.E.R. from using CR servos to using motor(s) anyway, so this might be a cool experiment if it hasn’t already been done.
8-Dale
yea, mim sure that would sork, be tough though, and ud need wheelie bars for walter, and very big batteries 
i couldn’t find any information on the motors, nothing on howmuch they draw
and i looed for differentials but i couldn’t find any, it was like build ur own or shutup cause they were selling pinions and gears and stuff, but no whole ones
W.A.L.T.E.R. sometimes tries to do wheelies now.
My RS Hummer only has a single motor, so it must be possible to do. I just have to figure out how and if this Stinger motor has the same torque and range in both forward and reverse - this would be very important for a differential drive system.
well i mean, defferiantial, gear box, transmission, same thing that invlvles gearing the RPM down to a resonable speed
Stinger looks like a standard 500-sized hobby motor with bushings.
I would expect somewhere areound 28,000 to 30,000 RPM no-load at around 8 volts, while drawing impressive amounts of current.
It’ll be pretty similar to the types of motors commonly found in everything from R/C cars (which you knew) to battery-powered drills. They differ in the number of winds and length of the armature, but are all fairly standard design DC motors.
Don’t know what to suggest for that current draw, as I never really did much with that when I was racing, other than knowing that my speed control could easily handle the kind of draw that one of those would put up, even under load. I think that people often used 20- to 25-Amp fuses inline, when they used them, but that would allow full acceleration under a newly-charged battery, from a dead-stop, and continuous running under loaded conditions. The fuses would only ever really pop if Something Went Very Wrongâ„¢, and both the throttle was stuck on and the wheels were locked (hardly ever happened, due to fail-safes in the electronic speed controls).
The motor’s shaft should be a nominal 3mm diameter (appx. 1/8") with a flat, to accept the standard 'pinion-gear-and-set-screw combination that’s standard to R/C cars. They’re usually fed through a multi-stage transmission (don’t know the ratio for the various cars out there anymore) to get the power to the ground. All shafts in said transmission, particularly those close to the motor, should be supported on both ends, preferably by metal - ball bearings if you can get them. Plastic bushings are a pain to work with, and even the teflon ones need replacing far too often to make it worth the lower expense.
(LONG post follows, but I’m just dumping the contents of my brain on the whole differential-drive-from-R/C-parts topic, here)
As to using them in a robotic application:
You’ll certainly want to gear them down - a whole lot - in order to use them for anything that’s indoor-safe. The transmissions they’re usually used with provide several very tall stages of gearing before feeding the power into a differential or three to split the power up to the wheels. Two-wheel-drive vehicles will just have the one diff, while most 4WD units will have a center diff to split power front-rear, and then one at each end, to split it again, this time left-right. Some toy trucks will only split left-right at each end, feeding power equally front-to-rear.
For differential drive, you could use R/C car transmissions, and approach it a few ways:
The easiest and most straightforward would be to get two motors, two transmissions, disable the differentials (fuse the gearing inside, effectively locking the output shafts together with the driven ring), and use one for each side of the bot. You could even hack off (or leave off, depending on the design) one of the driven axles, to save space. This is the approach that I would use if I were building a treaded/differential base from R/C parts.
You could get away with using one motor for both sides, but then you’ll need to get tricky. Use the stock R/C transmission, preferably with a geared differential (ball-type diffs don’t like this kind of abuse at all). Rig the outdrives of the tranny to drive one side of the bot each. Place a brake of some sort (nitro-burning R/C trucks frequently use disc brake packs) onto each side, to be controlled either independently by two servos, or alternately by one servo linkage. You turn by braking one side or the other, while power continues to be fed to the other side. The way the differential works wil mean that the unbraked side will speed up as the braked side will be slowed down. If you use two independent brakes (mechanically easier than the one servo solution), make sure that you aren’t braking both sides at once while the motor is running, or you’ll just be wasting power, and imposing load on a motor that wants to burn anyways. An obvious downside to this approach is that you can only stop one side while the other drives forwards or backwards; you can pivot on one tread/wheel, but not spin in place.
You could get VERY clever, and use a setup similar to above (one transmission with geared differential), but rig a mechanical reversing module on one or both of the tranny’s outdrives. This would allow you to pivot in place, but at the cost of a lot more weight an mechanical complexity.
Yes, I’ve thought a great deal about this, as I had designs on making a treaded platform back in the 1980s and 90s, when I was actively racing. The electronics weren’t nearly as streamlined as they are now, and the absence of Internet sources made it difficult to know what was out there (not to mention that the lack of electronic commerce made it hard to get what little that was out there at the time).
Finally: Hands-on is the best way to get a feel for how things work. Go to your local hobby shop, and have a look at the electric R/C trucks on display (that is, if they have any out - most seem to be going all-nitro these days). That will give you a fairly good idea of what’s going on inside the trannies, and you can figure the rest out from there. Nitro trucks have similar transmissions, but with different gearings, due to differing speed and power outputs between electric motors and nitro engines. I’ve noticed that many trucks these days have multi-speed transmissions, which makes things a bit more complex, and are unnecessary for the sort of application you’re looking to use them for. While at the shop, ask if you can see “The Big Parts Reference” that shows the exploded views of the trucks. Some might not let you see it - they can sometimes be really anal about that, as though it’ll give away some trade secrets or something. If you’re very lucky, and the hobby shop guy likes you, you might get him to agree to let you have the old copy of the catalog when the new one comes in.
Apologies for the long and rambling post. Hope there’s at least something in there that you’ll find useful.
No apologies needed! You have given me a lot of stuff to think about. For some reason, I seem to be prone to coming up with interesting and odd ideas for robots, and this seems to be another one of those.
I actually want to get an E-Maxx one day, and there is a lot of support for modifying it into a robot, gearing it down, etc. This one motor differential drive thing will probably be another long term project for me and I will probably end up just using standard LM gear motors and a Sabertooth controller for my first venture into using motors for locomotion.
I just thought there might be an easy way to make use of stuff I already have (the Stinger motor) for W.A.L.T.E.R. but apparently it is much more complex than I thought. I still want to do this at some point though because it has me intrigued for some reason.
8-Dale
It’s a 540 size slightly modified motor, according to the Traxxas website, 20 turns.
Wow, a person could get some serious torque out of this if it could be geared down far enough. I was affraid the current draw would be extreme, since even my RS Hummer only gets around 30 minutes maximum runtime from an LM 7.2V 2800 mAH battery pack.
Well, so much for using a Sabertooth 2x10 R/C to control this beast then. Dang, this might be more expensive a project than I can handle. But then, now that I think about it, all robot projects are pretty expensive if done right, and it takes me months to build one robot due to limited income.
This describes it well!
It still seems like this should be simpler than it is sounding though. Wouldn’t it be possible to do as I was thinking, and just run two horizontal drive shafts from the main motor shaft, with one turning clockwise and the other turning counter clockwise? All the gearing down would be done before the horizontal drive shafts connect to the motor shaft. But then, this really is a transmission of sorts, isn’t it, except with wheels turning in opposite directions (like the CR servos in W.A.L.T.E.R. now)? This should also still provide for rotation in place.
8-Dale
Oh, yes indeed. I understand that the E-Maxx is quite a popular platform for rover projects, including eMagellan-type autonomous agility contests. Having a pre-engineered platform, complete with robust suspension and steering mechanisms certainly offloads a lot of the design work from the builder, allowing them to concentrate on the sensor and programming angles of it.
I myself have a standing order at the local hobby shop to give me a call if an E-Maxx in decent condition comes in for sale in the consignment cabinet. There’s been only one so far, and that had a corner that was in questionable condition. My plans will likely require the parts from two working trucks, so I probably could have salvaged enough to make it work, but I was a little bit thin on project money at the time, and the rebuilt corner made me cringe from a mechanical standpoint (countersunk chassis screws that were “handy”, used to hold on suspension components where shoulder-bolts should have been, mismatched parts from the other corners, etc.). I passed on that one, but still have him keeping an eye out for another, should one come through. Unfortunately, the new ones only appear to be available as combo deals, including a 3-channel radio and R/C speed control, which would all be ballast, so far as my project is concerned, to be removed as quickly as possible, in order to make room for actual brains and important stuff. I’d love to be able to get a new unit without the extra expense of the radio gear, but apparently, he can’t order them that way.
I was bitten by the R/C bug when I got the great deal on the RS Hummer (one working, one non-working for parts), battery pack, charger, all for the price of a single Hummer. I haven’t taken it out and ran it for awhile though. It has a single motor drive and a single steering servo, which is where I got the idea of the single motor drive from. Hmmm, I am thinking some of the parts from the non-working Hummer might be useful here.
I have something different in mind for a Robot Magellan robot. I just have to build a prototype and see how it works, then refine it until it works as I want, and then repeat until I think I am ready to build a final version.
I have seen some pretty good deals on eBay, but haven’t looked for awhile because I am no where near the time when I want to buy one.
8-Dale
The motors could draw 20 amps stall! 
(earlier…)
I’m afraid that I’m having a little bit of difficulty seeing what you’re talking about, here. The “usual” configuration that you’ll see in R/C vehicles is to reduce the output prior to the differential, where it is split and delivered to the driven wheels. This is by no means set in stone, however. The transmission of the old RC-10 race car, manufactured by Associated, had an oddball tranny, which split the power right off the first stage of reduction, then sent it through a pair of idler stages before sending it out to the wheels. Yes, it was clunky and awkward, but it worked successfully for many years before they redesigned it to be more like the usual setup.
http://www.rthtg.net/i/transmissions.gif
If I understand you right, it sounds like you’re thinking of doing something similar to the old RC-10 tranny, but I’m not sure I understand how you’re planning to get both forward-back and rotational motion out of just one motor.
After thinking about this more, I realize that my basic idea or at least my way to implement it has a fundamental flaw. All I would get is the ability to turn in place at variable speeds. I would never get any forward or reverse motion of the robot. It would just spin.
The reason it works in my RS Hummer, is that both wheels are being driven in the same direction at all times. In a two wheeled rover, the wheels need to both be able to go the same direction as well as in opposite directions or different speeds for turning.
I don’t think a differential drive can work with just a single motor on a two wheeled rover.\
I wonder how heavy a payload two of these Stinger motors could handle…
8-Dale
It could, but you’d most likely have to resort to some sort of differential braking or clutching mechanism. This is how bulldozers got differential drive using a mechanical drive system before the evolution of the hydrostatic drive.
The older bulldozers I have driven used a series of clutches to selectively engage the treads (one main clutch, and two side clutches), and differential braking (one for each side). You would disengage the clutch and stomp on the brake for the tread on the side that you wanted to slow down, and it would slow or stop that side, while the other side drove forward, causing the dozer to turn, in the skid-steer arrangement we’re familiar with. Only thing was, you could only turn in the width of the dozer, since they were both being driven through the same drivetrain. In the sketch I posted above, this would be equivalent to putting a pair of servo-controlled brakes where the arrows are leading out to the driven wheels, allowing you to stop one side or the other while still applying power to the unbraked wheel.
That depends entirely on how far you’re willing to gear it down. You’ve got a whole lot of revs to work with there, and you can build a gear train with as tall a ratio as you like, so long as you realize that more torque == less speed.
The motors could handle a very heavy load if geared properly. Yeas you need two motors to go in forward and revers on both sides with seperate reduction. You would also need a 20 Amp per side speed controller. Parallax has a 25 amp controller with forward and reverse for $50. It is single motor but the twopack is $80.
parallax.com/detail.asp?product_id=29150
Yay, post 200!!!
Only 800 more to go!
Oh, I know! It’s the torque I am thinking about. I bet I’d get some incredible torque and still be able to get decent speed out of the Stinger motors. They are not very expensive either.
8-Dale
If I need that kind of current handling, I think I will go ahead with my motor mount project and build in mounting for an Open Servo board. Then I can have Open Servo Motors, and the controller will be completely Open Source.
8-Dale
