Just love the way you guys think--if it doesn't exit, build it. Yeah! That's the way I like to think. It does get frustrating at times. Everyone wants to make a buck and I just want to
solve a problem. There are these things called e-zip two wheeled electric scooters and some use LiO batteries. Some have 500 watt motors. I was thinking the seat post of same could be lashed (old boy scout leader) to the x-frame of a fold up manual chair, to thus push (power) the manual chair. Of course, I'd have to hold the scooter tiller to steer it. I have seen something similar, but the guy who built it, SuperX or something like that, told me he never tried the e-zip scooter angle. I like modular gadgets that can be added or subtracted at will and serve multiple purposes. So many hoist, jacks and lifts used in industry would be useful in assitive tech, if smaller and lighter. In fact, smaller, lower, lighter powerchairs in general would be good. Saw a cool cone shaped, modern looking prototype once on a Japanese site. Made sense to me.
Granny
by Burgerman » 13 Oct 2010, 03:17
JoeC's wife already has a proper powerchair or two for full power and full range etc. This is just an easy way to make a portable chair for shopping purposes. And an experiment for fun and learning.
The proper manufacturers are very backward and slow to embrace new technology like the hobby people as soon as its available. EG lithiums, brushless motors etc as JoeC is doing.
The problem here though for manufacturers is that unlike the batteries used in the scooter you are talking about, these lithium polymer batteries are not safe to use unless you know exactly what you are doing. They can burn or explode if charged incorrectly or cells are not balanced etc. But they have better energy density, and much better power to weight than the lithium ion in that scooter. And they are much cheaper too!
Its the same with full sized all day powerchairs like mine. I developed it to do all things properly. Its smaller and better indoors than most indoor only chairs that use smaller batteries. And yet truly outdoor all day and off road capable like the huge X5 which feels like a bus indoors. The real manufacturers cannot compete with it and yet I built it in my bedroom.
Frankly I dispair of their lack of innovation and daft prices. They all seem pretty clueless.
See here the old X5 beater! http://www.wheelchairdriver.com/Quickie . e-f55s.htm and I am building a new 12.75 mph, 14,000 watt and up to 300 amps and 36 volts one now! They seem incapable so we do it ourselves on here.
Here is (will be) the new one, and just as small indoors as the other one. http://www.wheelchairdriver.com/ultimat . ir-mk3.htm
by JoeC » 13 Oct 2010, 03:34
To be honest, she gets quite worried when she hears "lithium", and I doubt that I'd get her to sit on top of these things.If I get the system debugged, drivable, stowable for the car, and otherwise in good shape, I will probably have to spend a small fortune on some lithium iron phosphate batteries because they are so much safer, and I can show her this kind of video to demonstrate it:
In contrast, this is the kind of thing you risk with a lithium polymer battery-
Even though we all carry smaller versions of these in our cell phones, I doubt we'll see a day when they're generally accepted as safe for use in powerchairs. More likely we'll see some improvements to a less volatile battery, and some company will be brave enough to pioneer that. The more expensive, bulkier, heavier, safer batteries do still have some major advantage over lead acid based batteries. Even though they're not as good as lithium polymer in terms of power or storage per weight, they are superior to lead acid in this respect, and can last for many more cycles before replacement, potentially offsetting the higher cost.
I am keeping my eye on the Valence batteries. If the electric motorcycles really take off, these will be produced in large enough numbers to drive cost down and provide incentive for the manufacturer to improve performance.
JoeC Posts: 2359 Joined: 13 Jan 2010, 18:54by Burgerman » 13 Oct 2010, 03:45
That will be more expensive, bulkier, etc. The lipos are safe if you dont puncture them and keep them balanced and use a GOOD charger that is very accurate like the hyperion I use for everything now. http://www.wheelchairdriver.com/hyperion.htm Scroll down see lipo balance graph.
No clue on prices of the new one yet by the way.
And charge the batteries off the chair with a lipo safety sack. Then no worries. Its east to do since they are tiny! You could even use a lipo safety sack on the chair just in case. I would sit on that and not worry.
by Burgerman » 13 Oct 2010, 03:57
I wanted to fit 40 of those which is why I worried. I still may do it.
Remember my metal safety box idea? Well it must work because thats exactly what these guys are using in full sized electric flight! And they are very safety consious. http://yuneeccouk.site.securepod.com/PowerMotor.html
Must sleep. its almost 4 Am here!
by JoeC » 13 Oct 2010, 04:07
Great site- awesome to see someone is doing this with manned airplanes now! And being thousands of feet in the air in a tiny fiberglass shell with 184 pounds of LiPos? Yes, I'd say they had to think long and hard about safety!
I'm aware that the lithium iron phosphates are inferior, but sometimes compromises must be made. and when a marriage is involved then sometimes the variables do not all have engineering units attached to them, if you know what I mean!
JoeC Posts: 2359 Joined: 13 Jan 2010, 18:54by Burgerman » 13 Oct 2010, 04:40
Overcharge one drastically on purpose in a lipo sack fixed to a wheelchair and show her the worst case scenario that should never happen. Then let her decide? They are cheap enough to do a test on a chinese ebay one! Likely she will see the puff of smoke and say "is that it"?
But yes I know what you mean.
by JoeC » 13 Oct 2010, 04:51
Yes, you remember what it's been like with something as simple as pneumatic tires! She's not an engineer- but that doesn't make her any less fun
Wow it's late there- thought you'd be gone ages ago!
JoeC Posts: 2359 Joined: 13 Jan 2010, 18:54by JoeC » 13 Oct 2010, 15:05
It looks like this guy's done a very relevant project in relation to what I'm working on: http://members.cox.net/fvdm/
I was already planning on milling some aluminum tube like that as a support structure, and had a rough idea of using a single stage timing belt as an intermediary between the motor and the friction wheel. Milling that kind of thing is easy for me- and it will give me some flexibility in gearing, and make the motor bearings much happier to be well supported and evenly loaded.
JoeC Posts: 2359 Joined: 13 Jan 2010, 18:54by Ramblin Granny » 14 Oct 2010, 01:51
I hear you Burgerman and I fully agree with you. Backwards and saddled in the States with Liability and over regulation. I'll take your hint about the Quickie-Sunrise-f55s.htm I don't need a chair in my little house any bigger than the GoGo and have a rather short life expectancy. Really just want an all terrain for grass, gravel, dirt, rocks etc. and the lower to the ground the better. A low, lightweight, powerchair with very easy to change out wheels, for all terrains, would be great. It will be years before they make same. As you know, I don't share your concerns about LiO batteries, been using 23 grams of LiO , 24 volts, 9.6 Ah for 2 years now on my travelscoot with no problems what so ever, and I live in a very hot climate. I still love the way you and JoeC go about just doing what needs to be done. Experimenting is always fun and a learning experience. I can still think clearly and tell others how to build things I want, but don't have the agility or strength to build things myself anymore.
Granny
[quote="Burgerman"]JoeC's wife already has a proper powerchair or two for full power and full range etc. This is just an easy way to make a portable chair for shopping purposes. And an experiment for fun and learning.
The proper manufacturers are very backward and slow to embrace new technology like the hobby people as soon as its available. EG lithiums, brushless motors etc as JoeC is doing.
Ramblin Granny Posts: 61 Joined: 16 Aug 2010, 16:15by Burgerman » 14 Oct 2010, 02:39
I don't share your concerns about LiO batteries, been using 23 grams of LiO , 24 volts, 9.6 Ah for 2 years now on my travelscoot with no problems what so ever, and I live in a very hot climate.
Granny, lithium ion batteries as your travel scoot uses are better than lead acid. And pretty safe and used in laptops etc for years.But they are relatively heavy and cant make big currents (amps) compared to the lihium polymer batteries or LiPo that we are talking about in this thread. The model plane industry for eg do not use lithium ion as its too bulky, heavy, and cannot make big currents required. Even though they are hugely safer.
LiPo batteries are much more "powerful" and dangerous! And they have no metal case. They offer a much better energy solution to lithium ion batteries as used in your phone/laptop/travel scoot.
The least good lithium technology and the safest is athird up and coming one called lithium phoshate.
All three are different and all are "lithium ion" batteries. Your lithium Ion travel scoot batteries are in a metal "can" for eg. And cannot easily be punctured. A lithium polymer battery has no case, and is in a bag. It can easily be punctured which causes hugw fireforks as oxygen gets to the lithium! And they have a much better lower resistance structure and can be discharged at huge currents. So have a much higher C rating. Hope that clarifies some of the differences!
by Burgerman » 14 Oct 2010, 02:59
Added -- my NEW powerchair currently under construction uses a roboteq controller (300 amp capability!) as it is 3 times more powerful than a "powerchair controller", and it will let me easily move to lithium phoshate or lithium polymer in the future.
As such it is being built with both control system and motors and battery compartment to allow me to use these at up to 50 volts. The chair will do 12.75 mph with 3 lead acid batteries with MORE torque and 3 times more power than say the off road X5 has. And yet still it is as small as any indoor only powerchair! It can be used in the same tight areas as say prides new Q6 "the edge" which has small batteries and is useless outdoors. Like all 6 wheel platform chairs othe than the X5. Which is huge. If I ca do this with existing old technology and lead batteries what the hell are invacare/pride/sunrise etc on exactly?
Companies like invacare and pride dont have a clue. They just keep knocking out the same old underpowered 24v rubbish with some fancy marketing, tiny changes and some new "colours". I have been watching the same rubbish repeated year on year since I landed in a wheelchair 13 years ago. NOTHING really changed other than they got some fancy pointless colour screens. And a miserable extra intermittent 20 amps. About 100 less than needed. They still design by comittee and build overweight underpowered oversized railway engine engineered oversized powerchairs. And they cannot see it.
by JoeC » 03 Jan 2011, 21:52
Bringing this thread back.
It looks as though I've found an individual who is willing to sell me a number of A123 cells at a reasonable price, a bit better than the market rate. If this goes through, I think I'll be building a pack with eight in series. It's going to be quite laborious in comparison to the large prismatic format, but worth it if I can break the pack into a few airline friendly chunks.
I've been looking at my ultralight project and decided that the way I want to do it now is with a standard powerchair controller and a pair of the small size of magmotors. I already have two duffel bags (literally) stuffed with powerchair controllers and joysticks, so that part is free. The magmotors only weigh 3.8 pounds and should provide great performance. A single stage belt reduction to a friction wheel should be acceptably quiet, and not sound like you're running down the street revving a cordless drill. Just looking at my schedule and budget, I can't justify slogging through the hobby stuff right now. So- eight pounds of motors, some weight for brackets and a reduction, three or four pounds for powerchair controllers, and ten to twenty pounds of A123 batteries. The whole chair should weigh less than 70 pounds with better range any speed than anything comparable, and I'll have no headaches associated with the hobby stuff. I'll also have a predictable budget and timeline, and more assured reliability (important considering who this is for).
For anyone curious about what scared me off the hobby stuff, here are my reasons-
-Joystick processing. All the hobby ESCs and E-bike controllers require a button press to indicate reverse. In addition to a V-tail mixer, I'd need to come up with a way of triggering reverse when required.
-Current limit. The hobby ESCs that I found would do 1,000+ amps until they explode if the right conditions came up. They don't really have current monitoring so they can't do PWM current limiting. I would feel the need to use a slip clutch or some other method (other than a fuse) to be totally sure that they weren't able to do anything to melt wires.
-Sensors need to be added. You can get RC car motors with them installed, but they rev to very high RPMs for their power and would have too much noise and reduction. The low RPM outrunners could have them added without too much trouble, but it's more development work and uncertainty on the final cost of the project.
An interesting way around the first two items would be the dual channel brushless Roboteq that's coming out this spring. It will be $700, and let you make the most out of the biggest outrunners, which only cost $220 per pair compared to $600 for the magmotors. For somebody starting out without a duffel bag full of controllers, the budget is about equal between a powerchair controller with magmotors or a Roboteq with RC motors.
JoeC Posts: 2359 Joined: 13 Jan 2010, 18:54by Burgerman » 03 Jan 2011, 22:41
-Joystick processing. All the hobby ESCs and E-bike controllers require a button press to indicate reverse. In addition to a V-tail mixer, I'd need to come up with a way of triggering reverse when required.
-Current limit. The hobby ESCs that I found would do 1,000+ amps until they explode if the right conditions came up. They don't really have current monitoring so they can't do PWM current limiting. I would feel the need to use a slip clutch or some other method (other than a fuse) to be totally sure that they weren't able to do anything to melt wires.
Button push for reverse? News to me. I have speed controllers all over the bench, and even V tail / elevon mixers. No buttons in sight!
Current limit usually relies on the motor not drawing as much as the controller can give. Wich works well?
But your way will work too!
by JoeC » 03 Jan 2011, 22:59
I was getting advice from the E-bike guys, and what I thought I was hearing was that both the E-bike and the RC controllers require a button for reverse. I am 100% sure that the E-bike controllers need it; the importer/sell told me this was the case, and I'm sure he would have been glad to make some sales if it was going to work out with easy bidirectional control. Maybe I was mixed up about the RC controllers.
One was recommended to me here: http://www.hobbypartz.com/ezbrescfor18.html and now that you mention it, the user manual does make it look like it will do what I want.
Might need to reconsider this. Again.
Or maybe not. Familiarity with most parts of the system will improve the odds that I'll get it done in a timely fashion, and it means less weird things will crop up. My wife does not appreciate weird unexpected things happening with her powerchairs, even if they make good learning experiences.
JoeC Posts: 2359 Joined: 13 Jan 2010, 18:54by Lord Chatterley » 04 Jan 2011, 02:45
What about these motors-
Lord Chatterley Posts: 2915 Joined: 06 Jan 2010, 13:12by Burgerman » 04 Jan 2011, 03:28
There are lots of these. These ones are not that efficient for brushless and the usual problem. Price and easy availability with full specs for 2? Not possible?
And they are too big diameter by half inch yo fit the 6 inch wheels I use As small quantity buyers (unlike WC manufacturers), we have no power and must buy easily available over the counter gear. Manufacturers do have these avenues but no clue.
by pattherat » 04 Jan 2011, 03:29
I don't know if this will help, but here is the original patent for the zinger:
pattherat Posts: 118 Joined: 15 Jun 2010, 01:19by JoeC » 04 Jan 2011, 03:35
It might be useful to someone out there, but I don't think it's useful to me. It requires a brushless controller, it doesn't have a weight listed, and my best guess is that it will be expensive to import. Don't get me wrong- it looks like it has a lot of performance potential due to its neodymium magnets and hub style construction, it just doesn't look like the cheap/light/easy to integrate/easy to buy thing that I'm looking for in this particular project.
On the subject of hub motors, I see that Golden Motors is still updating their website. Although I haven't been able to get a sales rep on the phone in any of my previous attempts, I might have to try harder. Their prices are great, although I'm not convinced of the quality. If the performance is low but the build quality is OK, that might balance out due to the reduced weight of the lithium batteries and light weight of my wife. I'm not risking an order until I can at least speak to a human.
Good thing this project isn't under a tight time constraint or anything.
JoeC Posts: 2359 Joined: 13 Jan 2010, 18:54by JoeC » 04 Jan 2011, 22:36
Good news, I spoke with a human at Golden Motor. She is checking with the factory to tell me the motor's resistance and momentary peak torque. The website's spec sheet shows a peak torque of 24 N-m, and with a wheel diameter of 13.8 inches that's just over 30 pounds of pushing force. Considering I can get well over three times the pushing force from the motors we use for sports, I am highly skeptical that this hub motor can be useful. Sure she weighs less than 100 pounds, and I can save 80+ pounds by going with lithium batteries, but that's still at least 180 pounds to move around with two motors giving 30 pounds of thrust each. On paper that's just enough to get her over the steepest legal slope for a ramp. Since the whole world's been re-paved to conform to the law, that should be just fine!
Seriously though, my hope is that they'll come back and tell me that the motor can produce two or three times the torque shown in the dynamometer plot, and can handle two or three times the current shown without burning out (and tell me a resistance value that supports such a claim). I won't cry about lousy efficiency at high load, as long as it'll do it. For $150 per motor they're cheap, and would be a nicely integrated package. They're over 15 pounds each with tires though, so other than price and ease of mounting to a lightweight frame I'm not sure it's worth bothering with compared to the other options.
JoeC Posts: 2359 Joined: 13 Jan 2010, 18:54by JoeC » 07 Jan 2011, 07:45
No word from Golden Motor yet.
I've been looking into the RC motor option some more, and I am actually starting to feel more confident about it. As a friction drive it has a fairly well defined slipping point between the knurled friction wheel and the rubber drive wheel, and it will take a lot of effort to keep the two from slipping at high force. Consider this motor with a 3:1 drive belt reduction:
Sure it could draw 500 amps if it was stalled, but the friction force at the interface of the knurled wheel would be (by my math) 600+ pounds at full throttle. It would start to slip way before then! I don't need to create an elaborate clutch mechanism to prevent the RC motor controller from burning out, I already have a simple one in the form of a friction drive wheel. In fact, if the interface friction is only able to hold about 150 pounds, it should start slipping well before 1/4 throttle (and well before 100 amps). I'll definitely need to look at an exponential joystick curve and a little delay to keep this thing from jumping like a wild thing, but when it comes to power and performance it's better to have it and not use it than to need it and not have it!
I like the motor that I've linked because it has a higher efficiency, lower weight, and lower no-load current than the Magmotor. It operates at lower speed for lower acoustic noise and simpler reduction, and it's $250 cheaper! Saving $500 on motors is a big deal, even if it means $300 in RC parts to make it all work. Glad I still have an oscilloscope, because I have a feeling it might be useful for figuring out how to install sensors on this outrunner.