Samd
10 MW
+1 kepler. Thanks for articulating what I could not after a loooooong week.
i'm still having problems with your definition. what is "true assist" again?wayover13 said:...This is what I am calling "true assist," i.e., a system designed only to assist the rider, not to allow him to use his bike as something closer to a motorcycle. The aim of true assist, rather than being how fast the motor can propel the bike or how far the battery can take the motorized bike with no pedaling by the rider--which really aims at maximizing assist--is to determine what minimal amount of assist is going to be enough to ease the rider's exertion in difficult terrain.
dictionary said:as·sist
/əˈsist/
Verb
Help (someone), typically by doing a share of the work.
Yeah, as I've admitted, there's certainly subjectivity involved. If you looked at the Tetz web page for which I provided a link, that can give some further orientation to the concept as I'm formulating it. The Hilltopper kit, at least so far as the catchy name they've chosen to market it with is concerned, also embodies a similar aim. I felt the need to try and enunciate this concept here since, as I mentioned, so much of the thrust of e-biking seems oriented toward high-performance kits that make a bicycle into something more like an electric motorcycle. Against such a backdrop, I wanted to make it clear that, for my own uses, the motor's role will be minimal--it being primarily used to keep me from driving myself too hard getting my bike (with wife and gear) to the tops of grades.GCinDC said:i'm still having problems with your definition. what is "true assist" again?
sounds more like "minimal assist".
or just assist?
Yeah, I've used the phrase "minimal assist" in describing my aims as well. As I've mentioned elsewhere, what this means for me is that the motor is not doing anything most of the time--including not adding excess drag. Where assist is needed, which will be primarily on uphill grades, the motor provides assist--accounting for perhaps as much 50% of the force propelling the bike to the crest. Then the motor disengages again until the next uphill grade.dictionary said:as·sist
/əˈsist/
Verb
Help (someone), typically by doing a share of the work.
i have no idea how other pedelec or torque sensing systems work, but i mainly just wanted to write to say the expression "true assist" bothers me, and is not at all descriptive. sounds purely subjective...
Again, while, for my purposes, an on/off switch seems as though it could be an improvement to the ideal system as I envisioned it* because it would further simplify things, it's not really related to true or minimal assist as I'm trying to define it. In any case, it's nothing I intend to implement in this upgrade, so we can set it aside in this discussion.dogman said:I keep getting the idea that he wants "no think about it" assist except to turn it on and off. Pedal assist, + power level switches is pretty close to that.
It's definitely a pita to try to ride a system designed for 20-25 mph at 10 mph. 15-20 mph not so bad, but below 10 mph you lack throttle control. It goes to on- off 100w. You get this jerky, too much too little thing going on. I think that's what he's hating.
Great to see others are doing electric-assisted touring. This is our primary aim and is why I'm researching assist systems. I'd say our assist proportions should be something more like 80/20 human/electric--that because we intend to use the assist almost solely for help getting up grades. It should be disengaged most of the time outside those conditions. Maybe I'll upgrade to the Thun BB at some point in the future, but for the initial phases of my intended upgrade I'll be sticking with a throttle.Diamondback said:im using what i consider a "true assist" setup on my trike.
im running an ezee geared hub motor on 12s lipo (50.4v fresh of the charger), with a CA V3 and Thun BB.
i can easily get less than 3wh per km on most solo rides, and even when loaded up touring, i can get 6wh/km.
more often than not, i get home having provided more watts than the electric system has. it's usually close to 50/50 human vs electric.
most often it's more l like 65/35 human / electrons.
for one example, i recently did a 186km weekend tour and used only 19.1ah to do the distance, and that was loaded up with 14% hills in the mountain passes.
i am about to leave (tomorrow morning actually) for a 1200km 19 day tour.
Yeah, I've horked up a few of those in my day. I don't think I have many left to hork.-dg said:The above is really good advice for OP's request. I have a very similar cycling background and age etc to the OP. Generally I am interested in making assisted bikes rather than electric motorbikes. I don't have a tandem but am planning a cargo bike so the question "how do I get my older-weaker self and 150 lbs of compost up the hill to my house without horking up a lung?" has been something I've thought a lot about.Warren said:I grew up in Wisconsin, but spent the last 39 years in Virginia. My wife and I rode our RANS Screamer tandem for a decade, in the mountains of Virginia. After several knee surgeries, and a knee replacement, she has decided to quit riding. If you have a tandem with a 20" front wheel, and only want to use assist for climbing, there is no point in getting a mid-drive. You are making this way too complicated.
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Get the 12T, in a 20" wheel for an ~15 mph top speed on 52 volts. Get this pack.
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With this setup you will never have a problem climbing the steepest, longest climbs. You will never be tempted to use it for anything other than climbing, and perhaps starting from a dead stop. With the built-in freewheel in this motor, on a tandem, you won't even know the motor and battery are there, until you use it.
Interesting comments. I've actually got two bikes, one of which is being upgraded and the other of which I will probably add an assist system to later--both recumbent tandems. Climbing at 9 mph suits our pace just fine, that being a few miles per hour faster than we climb without assist (we can drop down to 5-6 mph on tough grades). I'm going to make a conservative estimate that our output wattage will be 300 instead of 250: as I mentioned, I like a brisk aerobic workout and am usually finding I need to restrain myself from working too hard. My wife is a lot weaker than me, but she does pretty good at keeping up a moderate pace for long periods. For the record, the hub-motor wheel I'm replacing on the bike I'm upgrading is a 16" (front) wheel, not a 20" wheel.A similar but lower budget, somewhat quieter, alternative to the suggestion from Diamondback that is even slower because it uses lower voltage would be: a 36 or 48V Bafang BPM front motor in a 20" wheel, a 25 amp controller and a 20+Ah battery in the neighborhood of 30-ish volts. You want a no-load speed of around 12-13 mph.
Assuming 440 lbs gross weight, and 250 watts pedaling input total, this combination will climb a 12% grade at 5 mph and is most efficient on a 5% to 6% grade (very common highway slope) around 9 to 10 mph. By 12 or 13 mph the motor is doing nothing which is what you are asking for. For example, with this setup you can climb Rabbit Ears pass (which I still remember from my cross country, 7%, 3000 ft gain) at 8 mph. It would still be a hard climb, but practical, not torture. All these combinations work without overheating the motor according to the simulator.
Get the motor first and measure the speed with a known voltage and then order the battery with the right voltage to get the no load speed around 12-13 mph. A Ping would be a good fit for this as he can make custom sizes, eg 33 volts last I checked. Since it's a tandem you can afford the space and weight. But anything 20+ah around 30-ish volts will work. This application is not going to demand much from the battery as long as it is big enough to be useful.
I think the control issue in this case is pretty simple. Thumb throttle with auto-cruise control, or almost even just an on/off button. Given that you only want it when you have a hill to climb, that the power is limited by the low current, and that it won't go very fast anyway, you are almost always going to want most or all of it. I'm assuming you can accept climbing 7% at 9 mph at full throttle instead of 7 mph at part throttle or 3.5 mph on your own.
Try out the ebikes.ca simulator, it is great for this sort of design exploration. For your criteria I used a 30 V 20 Ah battery, the 25 A controller, 20" wheel and the Bafang BPM motor (this is the 36 V motor, the 48 would be slower yet, you can scale the battery voltage to see some of the effect)
The stokemonkey was recommended to me in another thread on these forums and does look interesting. But it appears to be out of stock: supposedly it was going to be available again in the spring, but not much of spring is left and it's still listed as out of stock. They are located in Canada though, and I think their spring starts somewhere in early July or so, doesn't it?Warren said:The Stokemonkey is the only mid-drive I would consider buying. It is quiet, and durable. You could mount it to run off a second chainring on the stoker's left crank.
wayover13 said:Climbing at 9 mph suits our pace just fine, that being a few miles per hour faster than we climb without assist (we can drop down to 5-6 mph on tough grades). I'm going to make a conservative estimate that our output wattage will be 300 instead of 250: as I mentioned, I like a brisk aerobic workout and am usually finding I need to restrain myself from working too hard. My wife is a lot weaker than me, but she does pretty good at keeping up a moderate pace for long periods. For the record, the hub-motor wheel I'm replacing on the bike I'm upgrading is a 16" (front) wheel, not a 20" wheel.
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When you mention measuring "speed with a known voltage and then order the battery with the right voltage to get the no load speed around 12-13 mph," I presume you mean maximum no-load speed? I.e., with the throttle wide open? The only way I could really measure speed doing this as a sort of bench project, as I assume you're suggesting, would be by using the CA, correct?
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But there are disadvantages, e.g., fixing flats on your hub-motor wheel can be a pain since it's wired to the bike; I know that from experience
Interesting proposition. So you would say the MAC 36 volt 500 watt 12T motor I was considering would be overkill, given the usage scenario I've described?-dg said:The 16" wheel and 300 watts makes this even project easier and more elegant. No need for a big motor like the BPM. Get the Bafang SWXK5 or SWXK (same except for disk clearance) and run it with with the small 6fet controller and a 15 Ah (or more) 36 volt battery. I have this motor and controller on my wife's bike and it has no load speed of 27 mph in a 27" wheel at 48 volts and is quiet, smooth and reasonably strong. In a 16" wheel it would have no-load of 16 mph at 48 volts or 12 mph at 36 volts which is exactly what you want. And, with all the extra leverage it would climb a tree. The advantage of the big motor is that it can dissipate heat when you lug it, but with a 16" wheel and a controller limited to 14 amps you won't be lugging it.
Yeah, that connector looks like it could negate one of the cons of using a hub motor. But it seems to be offered only with the SWXK5 and, while the SWXK5 is listed as being sensored, it's the SWXK they list as having the option of being either sensored or sensorless (not that I really understand what sensorless versus sensored means, mind you). So it looks like one can't have one's cake and eat it too with respect to these two motors, correct? Definitely no need for full throttle from a dead stop on this bike, no.The Greenbikekit version of the SWXK and SWXK5 comes with a "waterproof connector" near the motor so it is easy to disconnect the to remove the wheel. I've attached a photo of my wife's SWXK in a 700c wheel. The connector is the bulge in the middle of the cable. Just cut the zip ties, unplug the connector and remove the wheel. Keep a few extra zip ties to replace them. Or use string or velcro or tape or something. I recommend ordering the sensorless version if possible as it is very smooth and as long as you don't need full thottle from a dead stop it will be perfect.
Certainly would be great to lower the weight this kit adds to the bike. My current DD hub motor/wheel must weigh about 20 lbs. (it's in a cast aluminum wheel).This motor weighs just under 3 kg and will let me pedal up a 12 % grade for a few blocks and I'm out of condition and weigh 270 lbs these days. I don't think it would be happy doing that for a long time in the 700c wheel, but in a 16" wheel and with under 15 amps input it should be fine.
Yes, the MAC would be total overkill. I recently tried another members bike with the MAC and it was a beast. Very impressive, but totally overkill for your situation. It is also louder than the Bafang motors I've heard so far. Not as bad as my mid-drive, but still objectionable at least to me.wayover13 said:Interesting proposition. So you would say the MAC 36 volt 500 watt 12T motor I was considering would be overkill, given the usage scenario I've described?
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Yeah, that connector looks like it could negate one of the cons of using a hub motor. But it seems to be offered only with the SWXK5 and, while the SWXK5 is listed as being sensored, it's the SWXK they list as having the option of being either sensored or sensorless (not that I really understand what sensored versus sensored means, mind you). So it looks like one can't have one's cake and eat it too with respect to these two motors, correct?
dogman said:Overkill is good when the hill is long enough and steep enough. That's why I recommended it. The extra time it will take to heat soak it will make all the difference on a longer hill.
Bear in mind, I tend to think in terms of worst case scenario because I ride them all the time. So I tend to recommend like the person will ride up 10 miles of 8-10% grade, AND, it will be 100F with a 20 mph headwind.
The smaller motor will do fine for lesser days, till it hits that headwind. Then it stalls the motor, and overheats. BUT, and this is a huge but, in a 16" wheel, it will take a hell of a lot of hill, and a lot of wind to stall even a smaller motor.
Nevertheless, I stick by the recommendation for a larger motor for one crucial reason. TWO people will ride that bike. It's a lot of weight to lug up steep hills. Stall that little motor, and you will overheat it very fast. Mo betta to get a motor that won't stall, because on that horrible day, you can just feed it more power. Most of the time though, you'll be fine with less than 250 watts.
On the other hand, a smaller gearmotor is very cheap. It won't cost you much to try it.
I generally agree that overprovisioning is prudent which is why I started out suggesting the BPM. However, I still think they will be happier with the mid-sized motor:-dg said:dogman said:Overkill is good when the hill is long enough and steep enough. That's why I recommended it. The extra time it will take to heat soak it will make all the difference on a longer hill.
Bear in mind, I tend to think in terms of worst case scenario because I ride them all the time. So I tend to recommend like the person will ride up 10 miles of 8-10% grade, AND, it will be 100F with a 20 mph headwind.
The smaller motor will do fine for lesser days, till it hits that headwind. Then it stalls the motor, and overheats. BUT, and this is a huge but, in a 16" wheel, it will take a hell of a lot of hill, and a lot of wind to stall even a smaller motor.
Nevertheless, I stick by the recommendation for a larger motor for one crucial reason. TWO people will ride that bike. It's a lot of weight to lug up steep hills. Stall that little motor, and you will overheat it very fast. Mo betta to get a motor that won't stall, because on that horrible day, you can just feed it more power. Most of the time though, you'll be fine with less than 250 watts.
On the other hand, a smaller gearmotor is very cheap. It won't cost you much to try it.
And how, exactly, does one output the varying known voltages to the motor so as to test maximum no-load speed? Is there some device that can be purchased for a reasonable price that will do this? I now understand the cycling computer part of your proposal and do have one laying around that I could use for such a test.-dg said:Yes, no load speed is wide open throttle with the wheel off the ground. Real speed on flat ground will be about 80% of this more or less depending ... To measure it, assuming it's not in a wheel, put the motor in a fork or stand or something so you can run it and just use a bike computer calibrated to the size wheel you want and stick or tape a magnet to the hub. Run the motor and hold the computer pickup near the magnet, no-load speed will be on the bike computer.
wayover13 said:And how, exactly, does one output the varying known voltages to the motor so as to test maximum no-load speed? Is there some device that can be purchased for a reasonable price that will do this? I now understand the cycling computer part of your proposal and do have one laying around that I could use for such a test.
-dg said:I partly agree with the general sentiment but, I think they will be happier with the mid-sized motor:
- They are doing these rides now, either without assist, or with a motor that is entirely unsuited to the application.
- The OP has expressed a strong preference for "true assist" and desire to minimize involvement with the motor. I don't think a large motor meets the user experience goals for the OP.
- I believe that they can get away with using the mid-sized motor. Given a no-load speed of only 12 mph and a controller limit of 15 A and 300 watts of rider input they will be going too slowly to keep the bike upright before they bog that motor.
This has the potential to turn out as a sort of chicken/egg dilemma: you need a battery to test the motor to see what sort of battery you need to buy for the motor. But I do have the battery pack I got with my original DD hub motor and it should still have some life in it. It was originally rated at 10 Ah and 48 volts. I could probably use it for such a test and extrapolate from there.-dg said:I use my battery as the voltage source. Just measure it's voltage with a Watts Up, CA, or voltmeter or whatever. Given the voltage at the start of the test and the speed tested you can then calculate the speed at any voltage you want.
chas58 said:I tend to go with this. If the bike is going to be used mostly without the motor, a small 2.2kg Cute Q100 with a 14amp controller and a no-load speed of 12mph would be just right.
I did a lot of research before making my purchase decisions, ultimately choosing the Heizmann 500 watt hub motor and building an A123 AMP20 battery pack. Got the motor, controller & throttle through Heinzman US and sourced the cells through Victpower. http://www.heinzmannusa.com/components.html. victpowersales@victpower.cnwayover13 said:I've looked at hub motors and thought seriously about ordering one: they're definitely the simplest solution and could serve my needs adequately.... What I've been hoping to find as I try to finalize my upgrade decision, is relevant hard data.