Curious, before you purchase these motors, consider this. The torque on that motor is almost enough to move a car. consider what you want this bot to do. if your just talking normal locomotion, I think this is over kill I roughly calculate (correct me if I'm wrong) the speed of your bot, with 8" wheels to be 242' per minute. or 4' per second. that is fast. yes the HB-25's will give you good control of those motors. but speaking from experience. those motors are way over kill. not only are they overly powerful, but the power requirements will be high to support that.
I'm telling you this because I had to rebuild my bot 3 times to get it in a usable state. it really is quite surprising how small a motor is needed for a protect.
Compare a commercial product to something your planning on building, usually the tiniest motor will work. I would look at a bunch of sites and find a smaller gear head motor, a smaller motor will make your batteries last longer (or use a smaller battery). also you have to keep in mind that with those motors spiking to 21 amps at start up, could reak havoc for the rest of the devices your powering.
I liked your models, may I ask what you used to create them?
just trying to save you some headache down the road. been there done that!
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"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster
It's rated at 98 inch pounds, so it should be able to move the robot along at a good pace ( on a flat surface: no mountain climbing for this bot). Keep in mind the amp rating. Lets say that in normal operation it uses 10 amps. If you battery gives 5aH that is less than 1/2 an hour of run time per charge. You battery is given at 14 aH. Thats 1.4 hours of running time. A little short, but acceptable. However, you may want to take a look at some lead acid batteries. You can get about 28 aH for the same price as that one. I think the company is Genisis, but I'm not sure. I saw some at Fry's on the bottom shelf in batteries. You'll have to do some searching for a charger, but thats the nature of the game. Anyway, be sure to get a seperate battery for the electronics.
One of the best ( and most cost effective) tools on a bot are electronic button bumpers. Are you going to use them? You could even build them completely out of wood...
I guess I should clarify, I didn't mean pull a car, I made a bot from practically the same motors, and it ran into my car and pushed it, as far as it could.. I was quite shocked. I think you'll be surprised just how strong these motors are. you know what your after more than anyone, just letting you know what I ran into.
I'd agree with the 2nd battery for the processor and other items.
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"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster
Did you try hooking it up to a truck like the guys in the QuadRover demonstration? It was amusing to see the little thing that looks like an air compressor pulling Japan's best.
That motor looks to be a worm drive motor, which would be my very last choice for a power drive. Very inefficient power transfer (high power loss), quick-wearing with any load (it was only a windshield wiper oscillator) and potentially strange robot drive dynamics. Worm drives are self-locking, they don't coast like spur or helical gear transmissions do. When you remove power from the motor, it's like putting on the brakes. It may be OK for very light loads on a robot used infrequently, but I'd consider a different gearmotor. The kindest thing I can say about worm drives is that they are the cheap and compact, with the fewest number of parts.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ ·"If you build it, they will come."
Why would you please anyone and if you wanted to keep your budget under 400 you need to tell us, I for one am not a mind reader let alone a post reader as seen in some of my other answers.
Sorry Curious, I might have started things on a bad note. but you posted your design for what I assumed was a peer review. In the end don't worry what we think. go with your gut and have fun doing it.
I was glad to see someone else desingning in sketchup. I'm trying to get all of the Parallax parts drawn in full scale. I have several in Google's 3dwharehouse. and I'll add more when I have access to the parts.
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"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster
CR: My new favorite motor is a $50 electric bike motor that puts out 250 watts peak. Have a look at http://tncscooters.com/product.php?sku=106105 , which is a 24-volt unit. I used·the·36-volt version of this motor on·my bike and it is amazing. Scary powerful, and this is the smallest motor they offer. This motor has one stage of gearing, and you can use the existing drive pinion with bike chain, or attach a wheel directly to it. They also have plenty of direct-drive motors that come with chain pinions or belt pulleys, see http://tncscooters.com/partsdb.php?type=ES. Presumably you want two motors·in your robot, so these motors would be overkill, but you could even ride on it if you like. They have several 24V controllers· ranging from $18 to $30 (with reverse) that are designed to use a 5V Hall-effect throttle sensor. I haven't modded one of those yet, but I suspect someone here can make recommendations how to interface·to a Stamp.
BTW, those motor specs say 2750 RPM no-load before gearing down (7.182 ratio) so the shaft no-load output is about 383 RPM on 24 volts. Depending on your needs, the motors·may operate off of 12 volts instead of 24.
A 24-volt system will use less current than an equivalent-power 12-volt system, so you can get by with two smaller 12V batteries in series. There are inexpensive smart chargers for lead-acid batteries available on eBay and also from that website http://tncscooters.com/product.php?sku=101140
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ ·"If you build it, they will come."
To clarify, there is one stage of gear reduction built into this 250W motor, so your output shaft (which has a nice, removeable 9-tooth cog for standard 1/8" fixed-gear bicycle chain) is turning at 383 RPM, no load. You can also use chain drive to larger cogs on your wheels for further gear reduction (lower RPM, higher torque).
Wheel diameter obviously affects your drive speed, smaller wheel means slower speed. Someone mentioned 8" diameter wheels above. The OD of the aluminum case around the output shaft is just under 3 inches, meaning that you could run a 4" diameter wheel and have a half-inch of case ground clearance in the extreme.
Your motor controller will give you very good adjustability, even at very low speeds.
You could also run this motor at half speed (and half torque, for 1/4 the peak power) on 12 Volts, depending on how much power you need for your application. Two of these motors at 12 volts would be about like a single 125 watt motor. That's still a LOT of power for a robot, and these motors would last forever in that low voltage configuration.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ ·"If you build it, they will come."
"Presumably you want two motors in your robot, so these motors would be overkill, but you could even ride on it if you like."
Sure would make doing the debug easier...
For the chain, you could buy commercial ( http://www.robotmarketplace.com/products/roller_chain.html·), but it is rather expensive. You could also get chain from old bicycles. Either buy a bicycle cheap and tear it appart for the chain, or find an old one that nobody wants anymore. You'll probably need to give the chain and sprockets some TLC, but the metal underneath the rust should be fine. Another benefit is that you could use the wheels for something.
You should use wheels. There are no real cheap commercial treads available (see my thread in the sandbox "Finding the right tread..."), and wheels are much easier to use anyway. They are a bit more limited in mobility (and coolness factor), but at the size you need, they are about $4000 cheaper.
curious_roboticist, the shaft diameter will depend on which motor you buy and when you get the motor you can measure it or it will be stated in the specs. Most of us are glad to help when you have problems but why not do some of your research yourself. Sorry if that sounds harsh but it is the only way to learn this stuff.
Forums are for support, not complete project design. If you want that, there are thousands of contractors that can do that sort of thing for you. Being a "noob" means that you have to know your own limitations, and spend most of your time learning the ropes.
Comments
An HB-25 is $49.99 (that's 2 for $99.98) and it's 25A continuous for sure.
More the reason to go with the HB-25.
·
I'm telling you this because I had to rebuild my bot 3 times to get it in a usable state. it really is quite surprising how small a motor is needed for a protect.
Compare a commercial product to something your planning on building, usually the tiniest motor will work. I would look at a bunch of sites and find a smaller gear head motor, a smaller motor will make your batteries last longer (or use a smaller battery). also you have to keep in mind that with those motors spiking to 21 amps at start up, could reak havoc for the rest of the devices your powering.
I liked your models, may I ask what you used to create them?
just trying to save you some headache down the road. been there done that!
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"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster
DGSwaner
One of the best ( and most cost effective) tools on a bot are electronic button bumpers. Are you going to use them? You could even build them completely out of wood...
Post Edited (SRLM) : 8/17/2008 7:54:24 AM GMT
I'd agree with the 2nd battery for the processor and other items.
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"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster
DGSwaner
Did you try hooking it up to a truck like the guys in the QuadRover demonstration? It was amusing to see the little thing that looks like an air compressor pulling Japan's best.
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·"If you build it, they will come."
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- Stephen
I was glad to see someone else desingning in sketchup. I'm trying to get all of the Parallax parts drawn in full scale. I have several in Google's 3dwharehouse. and I'll add more when I have access to the parts.
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"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster
DGSwaner
BTW, those motor specs say 2750 RPM no-load before gearing down (7.182 ratio) so the shaft no-load output is about 383 RPM on 24 volts. Depending on your needs, the motors·may operate off of 12 volts instead of 24.
A 24-volt system will use less current than an equivalent-power 12-volt system, so you can get by with two smaller 12V batteries in series. There are inexpensive smart chargers for lead-acid batteries available on eBay and also from that website http://tncscooters.com/product.php?sku=101140
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·"If you build it, they will come."
Post Edited (erco) : 8/19/2008 11:26:13 PM GMT
Wheel diameter obviously affects your drive speed, smaller wheel means slower speed. Someone mentioned 8" diameter wheels above. The OD of the aluminum case around the output shaft is just under 3 inches, meaning that you could run a 4" diameter wheel and have a half-inch of case ground clearance in the extreme.
Your motor controller will give you very good adjustability, even at very low speeds.
You could also run this motor at half speed (and half torque, for 1/4 the peak power) on 12 Volts, depending on how much power you need for your application. Two of these motors at 12 volts would be about like a single 125 watt motor. That's still a LOT of power for a robot, and these motors would last forever in that low voltage configuration.
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·"If you build it, they will come."
"Presumably you want two motors in your robot, so these motors would be overkill, but you could even ride on it if you like."
Sure would make doing the debug easier...
For the chain, you could buy commercial ( http://www.robotmarketplace.com/products/roller_chain.html·), but it is rather expensive. You could also get chain from old bicycles. Either buy a bicycle cheap and tear it appart for the chain, or find an old one that nobody wants anymore. You'll probably need to give the chain and sprockets some TLC, but the metal underneath the rust should be fine. Another benefit is that you could use the wheels for something.
You should use wheels. There are no real cheap commercial treads available (see my thread in the sandbox "Finding the right tread..."), and wheels are much easier to use anyway. They are a bit more limited in mobility (and coolness factor), but at the size you need, they are about $4000 cheaper.
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- Stephen