Tecumseh engine - what horsepower? What's the direct coupling you used? Is it rigid? Does the mini alternator have mounting holes on the face, or are you going to use the side-mount holes?
""I also experimented with some smaller spider couplings to connect the alternator to the engine. Though they were rated for much higher RPMs than I was using, a small misalignment sent some parts into the air. I wasn't standing along the axial line of rotation, so I didn't get hit. Before any schoolchildren get to see this I'll need to build a shield around the coupling"".
Yea they always need a shield
If you ever need such a thing again, use·Kawasaki Jet Ski engine couplers. Also one watercraft company that's no more, used a variation of a "Pilot Bushing" for the center of the coupler. But since most engines are rubber mounted, the male portion was a ball shaped piece of "Delrin"··(machinable plastic) and the female side was just a hole for it to fit in.
Also for axle shafts or power output shafts use a QD Bushing.
Also I was wondering if you thought this project was a success?
It looks like you found out that alternators can really draw or require·a lot of hp to in order to produce power. Did your final design produce more amps, than the total of all your current draws in a full load condition?
Ken,
Honda 2.5 hp , I'm just using a alingment bushing to do some measuring. I am looking into a flexable coupler that can handle RPM's , capt. quirk had some good suggestions . I'm hoping to use the existing mounts that are on the alternator.
Yes, it was a success [noparse][[/noparse]by my measures]. With a 1.5 HP engine I was producing about 30A of continuous current at 12V. If I do the math correctly then this is about 360 watts and a 1.5 HP engine produces about 1100 watts if it were 100% efficient. The low efficiency is a result of adding resistance to the alternator's field to reduce the current output. I took the field outside of the alternator and put some big resistors on it. If I didn't do this then I may have had about 60% efficiency - not sure. I'd say that 40A of power is plenty to run a robot and more than I needed which is why I reduced the field current. I don't know how practical it would be to run a robot for an hour on batteries with 40A of current draw, but it would be a darned heavy robot.
My next robot includes three MR11 halogen lights on the front since I've got power to spare. I'm hoping to get some pictures up this weekend, before Brian outruns me with his new concept.
I'll take your suggestions on the couplings, too. Good ideas.
What I like about a hybrid design is that you get hassle-free power, ready to go anytime, lighter weight, and the convenience of electric motor control devices like the HB-25s. It's a nice combination in my mind. I probably made all kinds of mistakes on the project, but I'm an experimenter when it comes to this stuff. I'm actually better behind a desk but we all know there's really no reward like building something to show off. It's·a fun challenge.
These projects take a lot of time, though.·I quit a lot of other activities (like exercising) and missed out on a few family gigs just to keep my robotic projects going.
Ken Gracey
Parallax, Inc.
Post Edited (Ken Gracey (Parallax)) : 3/22/2007 4:17:04 AM GMT
Just an FYI on charging voltages, Most small bikes and skis only require 1 amp for battery charging after all loads have been subtracted(break even point). Newer batteries like the Orbital, often require a different charging rate that I believe is closer to 3 to 4 amps. Most larger bikes and ski's like Polaris and likely the 950 rotax Sea Doo are normally around the 3 to 4 range, but I have seen 10. Seems like real overkill, but when ride time is short and use of the starter is high, I'm sure there's a need.
360 watts = .36 Kw·* 1.341 = ·.48276 HP at what ever rpm, Plenty of potential left.
Also, from what Brian was talking about, there is many other smaller motorcycle and watercraft solutions out there and additional flywheel weight maybe benificial and allow an electric starter. And there are much less expensive alternators from NAPA available, if you ever need more info on model vrs·pricing, my wife is the Manager of one and it's close to home.
Thanks for taking the time to answer
Bill
Post Edited (Capt. Quirk) : 3/22/2007 7:44:53 AM GMT
Below is my second prototype of this project. The electronics are not yet installed, but you can see where they sit in the front of the robot. I've made several improvements to the original design. These improvements include a clutch-free system, a better layout (batteries are under engine), lower center of gravity, integrated Ping sensors (six of them), halogen lights, smaller wheels (these are from summer roller skiis and Razor scooters) and a superior caster design which should be wobble-free at high speed. I also switched to the Robin Subaru engine, which is a·better performer IMO compared to the Honda mini 4-stroke engines.
There is still lots of room for improvement, but I'm happy with the results since it's a significant step forward from my last iteration. This particular version was put together as a trade show demonstration for next week's Embedded Systems Conference. A Propeller chip will display the sensor values on a monitor. It's a neat demo - a small robot image is drawn by the Propeller in the middle of the XGA display. Distance to objects are shown with bar graphs placed where each Ping is located on the robot.
I haven't run it on fuel yet, but once I do you'll see videos on this link.
The ideas, code and drawings·are free for the taking if you want to make something like this on your own. I haven't got more details together yet, but I shall post them on this thread as I have the time. It helps to have access to metalworking tools, but·if·you decide to use a pulley between the engine and alternator this project could be done with a drill press and welder. The direct coupling method requires·some machined parts (the way I did it - others may have a way around that·challenge).
Sincerely,
Ken Gracey
Post Edited (Ken Gracey (Parallax)) : 3/27/2007 4:47:03 AM GMT
I love your engineering style. Functional and elegant.
I'm looking at the electronics orbiting around a power plant, and have to ask.
Do you need to take any interferences precautions with both a spark plug firing and creating electricity with a generator?
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- - - PLJack - - -
Perfection in design is not achieved when there is nothing left to add. It is achieved when there is nothing left to take away.
Ken, ·· If you have not already you should hook the throttle control to a servo and let the unit idle when the DC motors are not being ran and it should provide to the micro and when the micro needs to move the DC motors it can rev up the gas motor. I like this so much that i am working on a very simular setup to power my sons Powerwheel riding toy so I dont have down time waiting on the batteries to charge.
It's under R/C in this video. However, you can't hit anything because it has a Propeller retrieving data from six Ping))) sensors mounted in the chassis.
I'd like to sit in my office and watch this robot do laps around our office building, which is my goal this summer.
Very cool! Is the gas motor like the size that's on weedwhackers? For us budget-challenged, need to find some good 2nd hand source of motors and generators. Keep up the good work, this is really amazing!
cheers- Scott
There are two engines that work well in this application. The Subaru Robin EH035 1.6 HP engine costs less than $200 and the Honda GX35 1.6 HP engine is about $230. But I've bought both of them off of eBay for less than a hundred bucks each. Indeed, these are EPA-mandated "weed-whacker" engines. They're 4-stroke engines - very quiet, lower emissions, reliable running ability, and easy to mount.
You can also find alternators from eBay, even new ones for about $100.
For motors, I have about ten (10) of these Groschopp 12V planetary gear motors 150 RPM which I'll sell for $40 each. But, again, back to eBay where I found them. There are some great 12V geared motors on eBay.
Parallax is planning a motor/wheel/mount for 12V mid-sized robots that will be $100 per side. These should be out pretty soon, no later than July. But I have to tell you that although the cost seems high, for 8x the cost of a servo and molded wheel you'll get a lot more robot to play with!
I bet you could put something together for less than $300 total if you tried. Seems like a lot of money, and it is, but it's nothing compared to an R/C airplane considering the ongoing return on investment after you "crash" it. I could always be talked out of a few HB-25s for free if somebody wanted to make a similar robot. . .
Props that is one of the most beautifuly machined robots i have ever seen.
Wow( im·A.D.D. )·this is Awsome i am currently working on a project similar to this but a little larger scale, i have a honda 24HP running 4 200 HO alternators that power 4 etek burshless motors and charge 8 hawker batteries. But i wish i had seen this sooner it would have saved me a ton if i had known about being able to create an external regulator, would happen to be able to describe how to create a higher current one? I have never been much a guru when it comes to embed-E, all the help would be appriciated, its a blast coming to this forum. YOU GUYS ARE AMAZING !!!!!!
side note if this seems all alittle overboard, im currently attempting to break the record for distance traveled by remotly oberated vehicle wich is currently 87 miles, and im going to attempt to break it with 347(AK is a big state), and i did check military and NASA stats to make sure they didnt already have it but a majority of thier vehicles travel AI much of thier trips.· Any ideas any of you have to make it more efficiant would be greatly accepted, i would post pics but most of its in pieaces due to lack of sponsors at the moment but ill post something as soon as i have it together.
Thanks StampNut2. I enjoyed your web page! Wow. It makes me think about the next 25 years entirely differently. When you think about it, each robot takes a year or more, so 25 years really isn't that much time, is it? Unless we're some kind of prolific Italian artists from the 1800s it seems like our robo-output is actually quite limited. Simple projects truly take a lot of time to do correctly, don't they? This doesn't discourage me, though. I'll still "do your best" as they say in Boy Scouts. The changes you've seen in 25 years in robotics are quite large, especially when you consider microcontrollers are more useful to the masses than they used to be.
Chipper, I think you can extend your driving range for your robot significantly by doing two things:
- use a hybrid approach to minimize power to weight ratio
- find a properly geared motor and match it to the right wheel size - forget about low end torque if you're on pavement
- regulate the alternator externally
Best of luck. Considering my robot will run for 1.5 hours on a tank of gas (storage could be increased) at 7 mph, it can go at least 10 miles. And the tank only holds perhaps 20 oz of fuel. There's no reason you couldn't carry a gallon or more.
Ken, Thanks for your comments, I do enjoy building robots, but my programming is limited [noparse][[/noparse]knowledge] and this holds me up big time. I envy those that can do both.
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Great site, as well as some very intuitive projects going on here. I love it!
I ran across your site in the process of trying to find a servo (or get a better idea for building one) for controlling the steering on a remote control car (1/3 scale) that I am conceptualizing at the moment, and found the hybrid power plant, which is essentially the heart and soul of another project I was working on recently to help out with power issues during hurricane season. I read the article and noticed the section about safety and just had to throw in my 2 cents on the subject -
You mentioned this:
" I also experimented with some smaller spider couplings to connect the alternator to the engine. Though they were rated for much higher RPMs than I was using, a small misalignment sent some parts into the air. I wasn't standing along the axial line of rotation, so I didn't get hit. Before any schoolchildren get to see this I'll need to build a shield around the coupling. "
I wasnt so lucky in the line of rotation department.
Long story short, I was using a weedeater engine, and forgot, but was reminded (by sheering the first key) that I needed to keep pressure on the flywheel to keep the engine in running order. All I had at the time was the clutch discs, so I used one of them as a nut. Big mistake, as can be seen in the pictures. The flyweight that is pictured is the one that I believe bounced off of my skull, the other was never found.
You also mentioned:
" I was prepared for most of the accidents, but didn't quite anticipate the fire on my desk. "
While I didnt have the fire, Ironically, I too was prepared for the possibility of this thing flying apart - in fact it was the last thought in my mind as I wandered around the back side of the engine in preparation to goose the throttle a little bit. "I need to be careful with this" ... I never made it that far - I was intentionally behind the engine, out of the line of fire, but then I made the mistake of reached up with my hand over the top of it, and just before I put my finger on the throttle lever, I peered over the top of the engine to assist my brain with the placement of the finger, and SPROING! It flew apart.
$6000 in hospital bills later (good thing for insurance, huh?) and a broken tooth (which I am still dealing with trying to get fixed), I am fortunately able to say that it wasnt any worse than it was, but easily could have been. If I had been successful at opening the throttle, things could have been moving MUCH faster.
I want to make it known that I dont post this as any form of scare tactic or anything, but I would absolutely HATE to see (or hear) of anyone repeating my fate. I would not wish it on anyone, and it is completely avoidable. I felt compelled to tell my story because I read somewhere later in the thread that people with lower budgets want to be able to find ways of doing these projects as well.
This is exactly the thought process I was using when I was designing my generator, so I just want to say this:
Well-advised precautions. You just can't be careful enough, especially when working with larger robots. Even if they don't hurt their creator they can hurt observers or other fixed objects like cars or glass.
My next project is also considered "dangerous". You see, we have a BIG bear problem where I live. Take a look at the photo below. This picture was taken last summer on my deck. All three of these bears became big problems. In fact they're all dead.·They break into homes and take food, and they have forgotten how to hunt. I live in one of the only homes in a valley of 500 homes that has not been broken into (we have over 180 bear break-ins this last summer). Every single neighbor of mine has had bears in their homes. A bear can cause $50K of damage. In fact, this afternoon I have to help board up a neighbor's home who has been invaded by bears during their absence.
Bears that obtain food gestate shorter, have multiple births, and associate homes with food. Terrible cycle. This problem is of much local controversy. If you want to see how bad it is, BBQ a salmon and leave it outside. You'll have a bear in minutes.
Until today, I have been using pepper spray in their face, paint ball weapons·on their butt, air horns, electronic barking dogs, etc. They've now become used to all of my defense tools. There are only two things that work at this stage: a big dog, a 50-caliber weapon coupled with a "shoot, shovel and shut-up" policy, and pepper (capcaican) spray. I don't want a dog because we are often gone for Parallax work, and I can't have a gun around here because California is a bit "left" in that regard. My last, and final line of defense will be pepper spray. If you can get them at close range (less than 10') your problem is solved, big-time.
My current design consists of a Ping))) sensor, BS2 and·a servo coupled to a pepper spray bottle. The only problem is that it doesn't know the difference between children, bears, and dogs. I will build in a·system for my children so they can shut it off, but I can't do much for the neighborhood pooch, who is supposed to be on a leash anyway. I'll place this device at the back door, where they are most likely to·enter.
When this pepper spray goes off you'll be coughing and dropped to your knees with snot rolling out of your nose. Bears react in a similar way. In fact, we had one visitor at our home this summer who opened up the pepper spray and pulled the trigger. Complex character and I'll leave his issues at that. The house was evacuated for two hours while everybody·dealt with pepper spray that got into their lungs·and eyes. Sounds terrible, but we're desperate to solve this problem.
I hope to share this prototype really soon here on the forums.
Heh, sounds like an interesting set of circumstances, to say the least. I guess it is notable to say then that nature should also never be underestimated either, even though physics is a form of it.
As for visitors opening cans of pepper spray, hahaha I know a few people like that - just cant keep their hands to themselves, and sometimes it gets them into serious trouble. My recent encounter was curiosity taking over for an acquaintance when he picked up an airhorn. Not nearly as much "fun" in the aftermath department, just a startled toddler.
Its a shame you had other people around - sometimes in THOSE circumstances, they make you just want to teach them a lesson... If it were to happen in the garage for example, "whoops, i must have leaned up against that closer button" ... not that they'll ever learn LOL
Anyway, I am curious to see this anti-bear device... any chance it will go mobile?
Comments
Tecumseh engine - what horsepower? What's the direct coupling you used? Is it rigid? Does the mini alternator have mounting holes on the face, or are you going to use the side-mount holes?
Cool project. . . keep going!!
Ken Gracey
Yea they always need a shield
If you ever need such a thing again, use·Kawasaki Jet Ski engine couplers. Also one watercraft company that's no more, used a variation of a "Pilot Bushing" for the center of the coupler. But since most engines are rubber mounted, the male portion was a ball shaped piece of "Delrin"··(machinable plastic) and the female side was just a hole for it to fit in.
Also for axle shafts or power output shafts use a QD Bushing.
http://www.alliedbearings.com/downloads/QDbushings.pdf
http://www.masterdrives.com/masterbookPDFs/qdbushingpages.pdf
http://www.martinsprocket.com/PDF/b-3.pdf
It looks like you found out that alternators can really draw or require·a lot of hp to in order to produce power. Did your final design produce more amps, than the total of all your current draws in a full load condition?
Honda 2.5 hp , I'm just using a alingment bushing to do some measuring. I am looking into a flexable coupler that can handle RPM's , capt. quirk had some good suggestions . I'm hoping to use the existing mounts that are on the alternator.
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Thank's Brian
www.truckwiz.com
·"Imagination is more important than knowledge..." ·· Albert Einstein
Yes, it was a success [noparse][[/noparse]by my measures]. With a 1.5 HP engine I was producing about 30A of continuous current at 12V. If I do the math correctly then this is about 360 watts and a 1.5 HP engine produces about 1100 watts if it were 100% efficient. The low efficiency is a result of adding resistance to the alternator's field to reduce the current output. I took the field outside of the alternator and put some big resistors on it. If I didn't do this then I may have had about 60% efficiency - not sure. I'd say that 40A of power is plenty to run a robot and more than I needed which is why I reduced the field current. I don't know how practical it would be to run a robot for an hour on batteries with 40A of current draw, but it would be a darned heavy robot.
My next robot includes three MR11 halogen lights on the front since I've got power to spare. I'm hoping to get some pictures up this weekend, before Brian outruns me with his new concept.
I'll take your suggestions on the couplings, too. Good ideas.
What I like about a hybrid design is that you get hassle-free power, ready to go anytime, lighter weight, and the convenience of electric motor control devices like the HB-25s. It's a nice combination in my mind. I probably made all kinds of mistakes on the project, but I'm an experimenter when it comes to this stuff. I'm actually better behind a desk but we all know there's really no reward like building something to show off. It's·a fun challenge.
These projects take a lot of time, though.·I quit a lot of other activities (like exercising) and missed out on a few family gigs just to keep my robotic projects going.
Ken Gracey
Parallax, Inc.
Post Edited (Ken Gracey (Parallax)) : 3/22/2007 4:17:04 AM GMT
360 watts = .36 Kw·* 1.341 = ·.48276 HP at what ever rpm, Plenty of potential left.
Also, from what Brian was talking about, there is many other smaller motorcycle and watercraft solutions out there and additional flywheel weight maybe benificial and allow an electric starter. And there are much less expensive alternators from NAPA available, if you ever need more info on model vrs·pricing, my wife is the Manager of one and it's close to home.
Thanks for taking the time to answer
Bill
Post Edited (Capt. Quirk) : 3/22/2007 7:44:53 AM GMT
Below is my second prototype of this project. The electronics are not yet installed, but you can see where they sit in the front of the robot. I've made several improvements to the original design. These improvements include a clutch-free system, a better layout (batteries are under engine), lower center of gravity, integrated Ping sensors (six of them), halogen lights, smaller wheels (these are from summer roller skiis and Razor scooters) and a superior caster design which should be wobble-free at high speed. I also switched to the Robin Subaru engine, which is a·better performer IMO compared to the Honda mini 4-stroke engines.
There is still lots of room for improvement, but I'm happy with the results since it's a significant step forward from my last iteration. This particular version was put together as a trade show demonstration for next week's Embedded Systems Conference. A Propeller chip will display the sensor values on a monitor. It's a neat demo - a small robot image is drawn by the Propeller in the middle of the XGA display. Distance to objects are shown with bar graphs placed where each Ping is located on the robot.
I haven't run it on fuel yet, but once I do you'll see videos on this link.
The ideas, code and drawings·are free for the taking if you want to make something like this on your own. I haven't got more details together yet, but I shall post them on this thread as I have the time. It helps to have access to metalworking tools, but·if·you decide to use a pulley between the engine and alternator this project could be done with a drill press and welder. The direct coupling method requires·some machined parts (the way I did it - others may have a way around that·challenge).
Sincerely,
Ken Gracey
Post Edited (Ken Gracey (Parallax)) : 3/27/2007 4:47:03 AM GMT
··· Looking very slick....will be a great trade show item!
··· Now, just put a set foot rests and handlebars on it and go hunting Segways!
· Cheers,
·Tom
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Tom Sisk
http://www.siskconsult.com
·
I'm looking at the electronics orbiting around a power plant, and have to ask.
Do you need to take any interferences precautions with both a spark plug firing and creating electricity with a generator?
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- - - PLJack - - -
Perfection in design is not achieved when there is nothing left to add.
It is achieved when there is nothing left to take away.
·· There among LCD displays is Ken's over-sized Boe-Bot!!
·· Check it out.
·Regards,
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Tom Sisk
http://www.siskconsult.com
·
·· If you have not already you should hook the throttle control to a servo and let the unit idle when the DC motors are not being ran and it should provide to the micro and when the micro needs to move the DC motors it can rev up the gas motor. I like this so much that i am working on a very simular setup to power my sons Powerwheel riding toy so I dont have down time waiting on the batteries to charge.
This is a very cool Project and i saw the very cool·video that you posted
Very very nice
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··Thanks for any·
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Sam
I posted a short video of the second prototype of this project:
http://www.youtube.com/watch?v=iXPhkvJw6BQ
Ken Gracey
Parallax, Inc.
One question, What or Who is steering? Is it being driven by remote control? acting autonomously? or executing preprogrammed instructions?
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Brian Meade
"They who dream by day are cognizant of many things which escape those who dream only by night" - Edgar Poe
It's under R/C in this video. However, you can't hit anything because it has a Propeller retrieving data from six Ping))) sensors mounted in the chassis.
I'd like to sit in my office and watch this robot do laps around our office building, which is my goal this summer.
Ken Gracey
I'd like to sit in my office and watch this robot do laps around our office building, which is my goal this summer.
·Ken Gracey
You do not seem to have a hole lot to do if you have time to do this·............................
I'd like to sit in my office and watch this robot do laps around our office building
That would be fun to do and lot of work to get this robot do laps around our office building
All kidding aside this a GREAT PROJECT And a good video to watch
Keep up the good work and Thanks for sharing this Project
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··Thanks for any·
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Sam
Post Edited (sam_sam_sam) : 5/24/2007 2:25:20 AM GMT
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Whit+
cheers- Scott
There are two engines that work well in this application. The Subaru Robin EH035 1.6 HP engine costs less than $200 and the Honda GX35 1.6 HP engine is about $230. But I've bought both of them off of eBay for less than a hundred bucks each. Indeed, these are EPA-mandated "weed-whacker" engines. They're 4-stroke engines - very quiet, lower emissions, reliable running ability, and easy to mount.
You can also find alternators from eBay, even new ones for about $100.
For motors, I have about ten (10) of these Groschopp 12V planetary gear motors 150 RPM which I'll sell for $40 each. But, again, back to eBay where I found them. There are some great 12V geared motors on eBay.
Parallax is planning a motor/wheel/mount for 12V mid-sized robots that will be $100 per side. These should be out pretty soon, no later than July. But I have to tell you that although the cost seems high, for 8x the cost of a servo and molded wheel you'll get a lot more robot to play with!
I bet you could put something together for less than $300 total if you tried. Seems like a lot of money, and it is, but it's nothing compared to an R/C airplane considering the ongoing return on investment after you "crash" it. I could always be talked out of a few HB-25s for free if somebody wanted to make a similar robot. . .
Ken Gracey
Parallax, Inc.·
Wow( im·A.D.D. )·this is Awsome i am currently working on a project similar to this but a little larger scale, i have a honda 24HP running 4 200 HO alternators that power 4 etek burshless motors and charge 8 hawker batteries. But i wish i had seen this sooner it would have saved me a ton if i had known about being able to create an external regulator, would happen to be able to describe how to create a higher current one? I have never been much a guru when it comes to embed-E, all the help would be appriciated, its a blast coming to this forum. YOU GUYS ARE AMAZING
side note if this seems all alittle overboard, im currently attempting to break the record for distance traveled by remotly oberated vehicle wich is currently 87 miles, and im going to attempt to break it with 347(AK is a big state), and i did check military and NASA stats to make sure they didnt already have it but a majority of thier vehicles travel AI much of thier trips.· Any ideas any of you have to make it more efficiant would be greatly accepted, i would post pics but most of its in pieaces due to lack of sponsors at the moment but ill post something as soon as i have it together.
p.s. Sry for stealing your thread
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Never give up when things go wrong.
robosapienv2-4mem8.page.tl/
Chipper, I think you can extend your driving range for your robot significantly by doing two things:
- use a hybrid approach to minimize power to weight ratio
- find a properly geared motor and match it to the right wheel size - forget about low end torque if you're on pavement
- regulate the alternator externally
Best of luck. Considering my robot will run for 1.5 hours on a tank of gas (storage could be increased) at 7 mph, it can go at least 10 miles. And the tank only holds perhaps 20 oz of fuel. There's no reason you couldn't carry a gallon or more.
Ken Gracey
I have not been following this thread to closely. But I am interested in the technology
How are you controlling the speed of the engine? Mechanical and electrical.
A brief description of the closed loop control system would be nice.
SJW
·
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Whit+
"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
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Never give up when things go wrong.
robosapienv2-4mem8.page.tl/
Great site, as well as some very intuitive projects going on here. I love it!
I ran across your site in the process of trying to find a servo (or get a better idea for building one) for controlling the steering on a remote control car (1/3 scale) that I am conceptualizing at the moment, and found the hybrid power plant, which is essentially the heart and soul of another project I was working on recently to help out with power issues during hurricane season. I read the article and noticed the section about safety and just had to throw in my 2 cents on the subject -
You mentioned this:
" I also experimented with some smaller spider couplings to connect the alternator to the engine. Though they were rated for much higher RPMs than I was using, a small misalignment sent some parts into the air. I wasn't standing along the axial line of rotation, so I didn't get hit. Before any schoolchildren get to see this I'll need to build a shield around the coupling. "
I wasnt so lucky in the line of rotation department.
Long story short, I was using a weedeater engine, and forgot, but was reminded (by sheering the first key) that I needed to keep pressure on the flywheel to keep the engine in running order. All I had at the time was the clutch discs, so I used one of them as a nut. Big mistake, as can be seen in the pictures. The flyweight that is pictured is the one that I believe bounced off of my skull, the other was never found.
You also mentioned:
" I was prepared for most of the accidents, but didn't quite anticipate the fire on my desk. "
While I didnt have the fire, Ironically, I too was prepared for the possibility of this thing flying apart - in fact it was the last thought in my mind as I wandered around the back side of the engine in preparation to goose the throttle a little bit. "I need to be careful with this" ... I never made it that far - I was intentionally behind the engine, out of the line of fire, but then I made the mistake of reached up with my hand over the top of it, and just before I put my finger on the throttle lever, I peered over the top of the engine to assist my brain with the placement of the finger, and SPROING! It flew apart.
$6000 in hospital bills later (good thing for insurance, huh?) and a broken tooth (which I am still dealing with trying to get fixed), I am fortunately able to say that it wasnt any worse than it was, but easily could have been. If I had been successful at opening the throttle, things could have been moving MUCH faster.
I want to make it known that I dont post this as any form of scare tactic or anything, but I would absolutely HATE to see (or hear) of anyone repeating my fate. I would not wish it on anyone, and it is completely avoidable. I felt compelled to tell my story because I read somewhere later in the thread that people with lower budgets want to be able to find ways of doing these projects as well.
This is exactly the thought process I was using when I was designing my generator, so I just want to say this:
Never underestimate physics! It *WILL* win!
Please be careful!
Steve
Well-advised precautions. You just can't be careful enough, especially when working with larger robots. Even if they don't hurt their creator they can hurt observers or other fixed objects like cars or glass.
My next project is also considered "dangerous". You see, we have a BIG bear problem where I live. Take a look at the photo below. This picture was taken last summer on my deck. All three of these bears became big problems. In fact they're all dead.·They break into homes and take food, and they have forgotten how to hunt. I live in one of the only homes in a valley of 500 homes that has not been broken into (we have over 180 bear break-ins this last summer). Every single neighbor of mine has had bears in their homes. A bear can cause $50K of damage. In fact, this afternoon I have to help board up a neighbor's home who has been invaded by bears during their absence.
Bears that obtain food gestate shorter, have multiple births, and associate homes with food. Terrible cycle. This problem is of much local controversy. If you want to see how bad it is, BBQ a salmon and leave it outside. You'll have a bear in minutes.
Until today, I have been using pepper spray in their face, paint ball weapons·on their butt, air horns, electronic barking dogs, etc. They've now become used to all of my defense tools. There are only two things that work at this stage: a big dog, a 50-caliber weapon coupled with a "shoot, shovel and shut-up" policy, and pepper (capcaican) spray. I don't want a dog because we are often gone for Parallax work, and I can't have a gun around here because California is a bit "left" in that regard. My last, and final line of defense will be pepper spray. If you can get them at close range (less than 10') your problem is solved, big-time.
My current design consists of a Ping))) sensor, BS2 and·a servo coupled to a pepper spray bottle. The only problem is that it doesn't know the difference between children, bears, and dogs. I will build in a·system for my children so they can shut it off, but I can't do much for the neighborhood pooch, who is supposed to be on a leash anyway. I'll place this device at the back door, where they are most likely to·enter.
When this pepper spray goes off you'll be coughing and dropped to your knees with snot rolling out of your nose. Bears react in a similar way. In fact, we had one visitor at our home this summer who opened up the pepper spray and pulled the trigger. Complex character and I'll leave his issues at that. The house was evacuated for two hours while everybody·dealt with pepper spray that got into their lungs·and eyes. Sounds terrible, but we're desperate to solve this problem.
I hope to share this prototype really soon here on the forums.
Ken Gracey
Parallax, Inc.
Heh, sounds like an interesting set of circumstances, to say the least. I guess it is notable to say then that nature should also never be underestimated either, even though physics is a form of it.
As for visitors opening cans of pepper spray, hahaha I know a few people like that - just cant keep their hands to themselves, and sometimes it gets them into serious trouble. My recent encounter was curiosity taking over for an acquaintance when he picked up an airhorn. Not nearly as much "fun" in the aftermath department, just a startled toddler.
Its a shame you had other people around - sometimes in THOSE circumstances, they make you just want to teach them a lesson... If it were to happen in the garage for example, "whoops, i must have leaned up against that closer button"
Anyway, I am curious to see this anti-bear device... any chance it will go mobile?
Steve