Electric assist upgrade / DD hub drag geared hub drag
- Thread starter wayover13
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wesnewell
100 GW
It does now. It didn't. Once you put in your location it will appear on all previous post.
Rassy
1 MW
Concerning radial lacing, when you put a large hub motor in a 20" wheel, or any motor in a 16" wheel, it is pretty much impossible to do anything but radial lacing, plus the spoke angle at the nipple would be too extreme even with single cross.
Abstract: a pair of older tandem riders, who have done some experimentation with electric assist, are looking to do an upgrade. They would like your recommendation for an efficient, low-speed, high torque system that could aid them in their ongoing long-distance touring aspirations.
Introduction
I'm getting ready to upgrade from a DD hub motor. This will be a long post explaining my experience with electric assist; what sort of bike I ride and why; what, more particularly, I'm upgrading from and why; and asking, finally, for suggestions.
I should start by stating that, though I now have a couple of years of experience with electric assist--having bought and installed my first kit a couple of years ago and having been using and troubleshooting it since--I definitely stand to learn a lot more about it. I remain quite sketchy on the electronics end of things, for example. So tips that involve a lot of electronics jargon and technical detail, while appreciated, are not going to be readily comprehensible by me. That said, I welcome any and all input and will try my best to understand things that may be a bit beyond my level of knowledge.
As to what sort of bikes I ride and why, we (the wife and I) are recumbent tandem riders. Apart from seeking more immediate health benefits from cycling, our larger goal in biking is to do long-distance touring. My initial hub-motor experiments were conducted to test the feasibility of using electric assist for long-distance touring. I was able to prove to my satisfaction that it is, in fact, feasible, though I came to realize some of the shortcomings of my first kit and am now looking to improve on it.
We have done a bit of unassisted long-distance touring, and it was largely successful. Neither of us are getting any younger, though, and with age, challenging terrain will become more and more of a hindrance. Electric assist, then, is meant to extend our touring capability yet further into our "golden years." And by "assist," I mean just that: we do not want to add a power source that will relieve us completely from the physical effort involved in cycling. Rather, we want something that can, under certain conditions, be used to augment our physical efforts. We want to keep pedaling and reaping the health benefits thereof for as long as our physical abilities will permit, but we don't want our waning physical strength to keep us from enjoying long and sometimes challenging rides.
This is a very important point I feel the need to stress here, since so many on this forum seem oriented toward high-performance systems and speed. This sort of thing is not at all our goal and, in fact, we are not looking for an assist that increases at all our top speed. The only sort of high performance we might be interested in is system efficiency, but that efficiency is going to be much more important, given our usage scenario, in low-speed situations (think hill climbing) than in any high speed situations.
The bikes and current assist system
Now, for the bikes. We have a two-wheeled recumbent tandem I'm aiming to electrify as well as our main touring rig, which is a three-wheeled recumbent tandem (delta trike). The DD hub-motor wheel is currently mounted on the tandem trike as the front wheel, and it is a cast aluminum 16" wheel that contains a 48-volt, 1000 watt motor. I've been using it with a 10 Ah lithium ion battery. The kit was bought off ebay. The trike has a 16" front wheel and 20" rear wheels, while our two-wheel recumbent tandem has a 20" front wheel and 700c rear wheel.
My intention, on buying the kit, was for it to be an "on demand" solution for challenging terrain. I did not realize at the time I bought it that it was a DD motor, nor did I really understand what that would mean in terms of the wheel's intended purpose. However a bit of initial inspection indicated to me that I would not, because of the added drag the DD motor causes when not under power, be able use it on-demand. In my initial tests, then, I had the wheel under power pretty much continuously, though I was using the thumb throttle judiciously, giving the motor just enough juice to make us go just a little faster than we would go with no assist. On hills, which is where I most want the assist to come into play, I would, of course, use more throttle.
With that set-up, I discovered I was able to get about 50 miles, on our relatively flat midwestern terrain, out of a full charge. I should mention that I did not use any sort of meter to monitor battery level and other data, but only relied on the LED's incorporated into the throttle, which emit green, yellow, or red lights to give a rough reading of battery level. This is something I intend to rectify when I upgrade, namely by adding a Cycle Analyst meter and learning how to read it.
We actually did some modest long-distance tours with this set-up. We found that, riding 20-30 miles at a time, then stopping to charge for a couple of hours or so, we could easily make 60 or more miles in the course of a day. It might be worthwhile to note that, between ourselves, our bike, and our gear, we are probably coming in at right around 500 lbs., give or take. I remain convinced that this sort of set-up will be perfectly feasible for the type of long-distance touring we hope to do.
The main weak point of this set-up though, it seems to me, is the DD hub motor. The big downside to it, as I see it, is that the point at which we most need it to assist us--namely on uphill grades--is the place at which it functions least efficiently, since we are gradually losing speed going up hills and the motor is forced to turn more and more slowly.
Possible upgrades
I have therefore begun to think that a geared hub motor, because of the typical 5-to-1 gear reduction they entail, may well provide a good solution to the issues we've experienced. These also create far less drag when unpowered: when covering flat terrain, then, the hub could more readily remain unpowered, thus leaving more battery for use on uphill stretches where assist is most needed. And, I would guess, increasing overall range per charge. And these motors come in low-torque configurations, which seems ideal for our usage scenario, wherein the main point of the assist is to alleviate some of the strain we experience getting our rig to the tops of hills.
Another possibility would be some sort of mid-drive assist. I've looked at eco-speed, which has much to commend it. I can see how it might be a much more efficient solution than would be a geared hub motor. But the price is a bit off-putting.
Then again, a friction drive has been suggested. I had actually initially though a friction drive would be the ideal system to use for our purposes. It remains an appealing possibility. But I have yet to find a production unit for sale, and the one I've found on this forum (eboost) looks like it has not been weatherized: though we would rather not ride in rainy weather, when doing long-distance touring, the weather conditions under which you end up riding are not dictated by you.
Something like an ezip motor also seems like it might be adaptable for my uses. Since I've just now begun looking at it I am unsure whether that sort of motor does free-wheeling, or whether it is an "always on" system. I'm leaning most strongly at the moment toward the geared hub-motor solution--perhaps a 20" MAC front wheel for the two-wheeled tandem and a MAC motor to lace into a 16" rim for the front wheel on the trike. I'm considering a 15Ah battery to share between the two since, for obvious reasons, we would never be riding both simultaneously. But I would have to have a duplicate set of associated electronics for the two (controllers, throttles, meters, etc.).
I am undecided at the moment whether to do a "roll my own" solution versus buying some kind of kit. The former solution seems like it could save me a bit of money as well as allow me more customization options. But since I lack a good grasp of the technicalities on the electronics end, opting for that approach could end up being more time consuming and might even involve more expense (ordering wrong parts by mistake, for example). The latter approach would likely be more expensive but carries greater assurance that things would be properly matched and would be more likely to work as a drop-in solution.
So, I've come here seeking advice of all kinds. Advice on parts, on approaches to my project, on vendors, and so forth. I will be most appreciative of any advice that may be offered.
Specific query, final note
To start off with a specific query, let me ask about torque arms. They seem to be recommended for most front-wheel hub-motor installations, and I can understand why. That said, I did not use them on my DD test rig and never encountered any situation when they might have benefited me. This is, I think, due primarily to the way I ride: I use the motor only for assist. The motor is almost never used as the sole force propelling the bike. So, given my usage scenario, do I really need to add torque arms to my bikes?
As a final note, I just want to stress again that we are not interested in going any faster on our bikes. An average pace of 15 miles per hour while on the bike is perfectly fine for our purposes: over the course of a full day of touring, that sort of pace could get us another 90-120 miles down the road, which is a very respectable daily average for this mode of travel. Any time we are going faster than that it should be, not because of the motor, but because we have a strong tailwind or we are on a downhill run--preferably with the motor disengaged. So whatever works most efficiently at speeds at or under 15 mph, and most especially on uphill grades, is what is going to be most fitting for our needs.
Thanks for reading and I look forward to receiving your input.
Introduction
I'm getting ready to upgrade from a DD hub motor. This will be a long post explaining my experience with electric assist; what sort of bike I ride and why; what, more particularly, I'm upgrading from and why; and asking, finally, for suggestions.
I should start by stating that, though I now have a couple of years of experience with electric assist--having bought and installed my first kit a couple of years ago and having been using and troubleshooting it since--I definitely stand to learn a lot more about it. I remain quite sketchy on the electronics end of things, for example. So tips that involve a lot of electronics jargon and technical detail, while appreciated, are not going to be readily comprehensible by me. That said, I welcome any and all input and will try my best to understand things that may be a bit beyond my level of knowledge.
As to what sort of bikes I ride and why, we (the wife and I) are recumbent tandem riders. Apart from seeking more immediate health benefits from cycling, our larger goal in biking is to do long-distance touring. My initial hub-motor experiments were conducted to test the feasibility of using electric assist for long-distance touring. I was able to prove to my satisfaction that it is, in fact, feasible, though I came to realize some of the shortcomings of my first kit and am now looking to improve on it.
We have done a bit of unassisted long-distance touring, and it was largely successful. Neither of us are getting any younger, though, and with age, challenging terrain will become more and more of a hindrance. Electric assist, then, is meant to extend our touring capability yet further into our "golden years." And by "assist," I mean just that: we do not want to add a power source that will relieve us completely from the physical effort involved in cycling. Rather, we want something that can, under certain conditions, be used to augment our physical efforts. We want to keep pedaling and reaping the health benefits thereof for as long as our physical abilities will permit, but we don't want our waning physical strength to keep us from enjoying long and sometimes challenging rides.
This is a very important point I feel the need to stress here, since so many on this forum seem oriented toward high-performance systems and speed. This sort of thing is not at all our goal and, in fact, we are not looking for an assist that increases at all our top speed. The only sort of high performance we might be interested in is system efficiency, but that efficiency is going to be much more important, given our usage scenario, in low-speed situations (think hill climbing) than in any high speed situations.
The bikes and current assist system
Now, for the bikes. We have a two-wheeled recumbent tandem I'm aiming to electrify as well as our main touring rig, which is a three-wheeled recumbent tandem (delta trike). The DD hub-motor wheel is currently mounted on the tandem trike as the front wheel, and it is a cast aluminum 16" wheel that contains a 48-volt, 1000 watt motor. I've been using it with a 10 Ah lithium ion battery. The kit was bought off ebay. The trike has a 16" front wheel and 20" rear wheels, while our two-wheel recumbent tandem has a 20" front wheel and 700c rear wheel.
My intention, on buying the kit, was for it to be an "on demand" solution for challenging terrain. I did not realize at the time I bought it that it was a DD motor, nor did I really understand what that would mean in terms of the wheel's intended purpose. However a bit of initial inspection indicated to me that I would not, because of the added drag the DD motor causes when not under power, be able use it on-demand. In my initial tests, then, I had the wheel under power pretty much continuously, though I was using the thumb throttle judiciously, giving the motor just enough juice to make us go just a little faster than we would go with no assist. On hills, which is where I most want the assist to come into play, I would, of course, use more throttle.
With that set-up, I discovered I was able to get about 50 miles, on our relatively flat midwestern terrain, out of a full charge. I should mention that I did not use any sort of meter to monitor battery level and other data, but only relied on the LED's incorporated into the throttle, which emit green, yellow, or red lights to give a rough reading of battery level. This is something I intend to rectify when I upgrade, namely by adding a Cycle Analyst meter and learning how to read it.
We actually did some modest long-distance tours with this set-up. We found that, riding 20-30 miles at a time, then stopping to charge for a couple of hours or so, we could easily make 60 or more miles in the course of a day. It might be worthwhile to note that, between ourselves, our bike, and our gear, we are probably coming in at right around 500 lbs., give or take. I remain convinced that this sort of set-up will be perfectly feasible for the type of long-distance touring we hope to do.
The main weak point of this set-up though, it seems to me, is the DD hub motor. The big downside to it, as I see it, is that the point at which we most need it to assist us--namely on uphill grades--is the place at which it functions least efficiently, since we are gradually losing speed going up hills and the motor is forced to turn more and more slowly.
Possible upgrades
I have therefore begun to think that a geared hub motor, because of the typical 5-to-1 gear reduction they entail, may well provide a good solution to the issues we've experienced. These also create far less drag when unpowered: when covering flat terrain, then, the hub could more readily remain unpowered, thus leaving more battery for use on uphill stretches where assist is most needed. And, I would guess, increasing overall range per charge. And these motors come in low-torque configurations, which seems ideal for our usage scenario, wherein the main point of the assist is to alleviate some of the strain we experience getting our rig to the tops of hills.
Another possibility would be some sort of mid-drive assist. I've looked at eco-speed, which has much to commend it. I can see how it might be a much more efficient solution than would be a geared hub motor. But the price is a bit off-putting.
Then again, a friction drive has been suggested. I had actually initially though a friction drive would be the ideal system to use for our purposes. It remains an appealing possibility. But I have yet to find a production unit for sale, and the one I've found on this forum (eboost) looks like it has not been weatherized: though we would rather not ride in rainy weather, when doing long-distance touring, the weather conditions under which you end up riding are not dictated by you.
Something like an ezip motor also seems like it might be adaptable for my uses. Since I've just now begun looking at it I am unsure whether that sort of motor does free-wheeling, or whether it is an "always on" system. I'm leaning most strongly at the moment toward the geared hub-motor solution--perhaps a 20" MAC front wheel for the two-wheeled tandem and a MAC motor to lace into a 16" rim for the front wheel on the trike. I'm considering a 15Ah battery to share between the two since, for obvious reasons, we would never be riding both simultaneously. But I would have to have a duplicate set of associated electronics for the two (controllers, throttles, meters, etc.).
I am undecided at the moment whether to do a "roll my own" solution versus buying some kind of kit. The former solution seems like it could save me a bit of money as well as allow me more customization options. But since I lack a good grasp of the technicalities on the electronics end, opting for that approach could end up being more time consuming and might even involve more expense (ordering wrong parts by mistake, for example). The latter approach would likely be more expensive but carries greater assurance that things would be properly matched and would be more likely to work as a drop-in solution.
So, I've come here seeking advice of all kinds. Advice on parts, on approaches to my project, on vendors, and so forth. I will be most appreciative of any advice that may be offered.
Specific query, final note
To start off with a specific query, let me ask about torque arms. They seem to be recommended for most front-wheel hub-motor installations, and I can understand why. That said, I did not use them on my DD test rig and never encountered any situation when they might have benefited me. This is, I think, due primarily to the way I ride: I use the motor only for assist. The motor is almost never used as the sole force propelling the bike. So, given my usage scenario, do I really need to add torque arms to my bikes?
As a final note, I just want to stress again that we are not interested in going any faster on our bikes. An average pace of 15 miles per hour while on the bike is perfectly fine for our purposes: over the course of a full day of touring, that sort of pace could get us another 90-120 miles down the road, which is a very respectable daily average for this mode of travel. Any time we are going faster than that it should be, not because of the motor, but because we have a strong tailwind or we are on a downhill run--preferably with the motor disengaged. So whatever works most efficiently at speeds at or under 15 mph, and most especially on uphill grades, is what is going to be most fitting for our needs.
Thanks for reading and I look forward to receiving your input.
dogman dan
1 PW
Most of what I had to say, was said on the other thread. Likely I'll merge that thread with this one, after it grows some and all the info will be in one place.
Do use a torque arm. Partly because gearmotors can twist harder, but mostly because it will be worth it when you need it. You will need it the first time a nut loosens. So far, you never had that happen, but when it does having a torque arm will help. At 30 bucks or so, it beats the hell out of twisted cut wires to the motor, which often short and blow the controller too.
For your application, it would be very hard to beat a mid drive motor. But the simplicity of just getting a slow wind Mac has definite appeal.
Do use a torque arm. Partly because gearmotors can twist harder, but mostly because it will be worth it when you need it. You will need it the first time a nut loosens. So far, you never had that happen, but when it does having a torque arm will help. At 30 bucks or so, it beats the hell out of twisted cut wires to the motor, which often short and blow the controller too.
For your application, it would be very hard to beat a mid drive motor. But the simplicity of just getting a slow wind Mac has definite appeal.
So far as geared hub motors I've looked at, the MAC looks like a pretty good candidate. They appear to have 3 models with 3 corresponding levels of torque/speed. But I'm not sure what, in terms of watts and volts, might be good candidates for my projects.
Someone on another forum remarked something along the lines of "human beings can only put out about 200 watts of energy, so any motor rated at 250 watts or more should work fine." But of course volts and amps play into this equation as well, and those are variables I don't grasp very well.
The MAC motor I looked at on em3ev.com, for example, is said to be a 500 watt motor that takes 36 volts. Would something like that be up to the task of assisting, up hills, two riders plus gear on a tandem? I'm kind of in the dark as to what controller I'd need for that as well.
Then, there's the question of the torque/speed options. As I think of this, I might need something like the 12t version of this MAC motor. The site lists the following regarding this motor: "Std. Front 12T, 200 rpm loaded." What the heck does "200 rpm loaded" mean? Does it mean 200 rpm (meaning wheel rpm's, I'd guess), is its optimal operating range under load? If I knew the answer to that question I could figure out, based on the tire's circumference, whether this hub motor seems suitable to my purposes. But as things stand I'm not able to get much out of this.
Someone on another forum remarked something along the lines of "human beings can only put out about 200 watts of energy, so any motor rated at 250 watts or more should work fine." But of course volts and amps play into this equation as well, and those are variables I don't grasp very well.
The MAC motor I looked at on em3ev.com, for example, is said to be a 500 watt motor that takes 36 volts. Would something like that be up to the task of assisting, up hills, two riders plus gear on a tandem? I'm kind of in the dark as to what controller I'd need for that as well.
Then, there's the question of the torque/speed options. As I think of this, I might need something like the 12t version of this MAC motor. The site lists the following regarding this motor: "Std. Front 12T, 200 rpm loaded." What the heck does "200 rpm loaded" mean? Does it mean 200 rpm (meaning wheel rpm's, I'd guess), is its optimal operating range under load? If I knew the answer to that question I could figure out, based on the tire's circumference, whether this hub motor seems suitable to my purposes. But as things stand I'm not able to get much out of this.
melodious
100 kW
How about the new stokemonkey mid drive kit? You may need to have your LBS install it with the proper mounts, gears, etc.
http://www.ebikes.ca/store/store_stokemonkey.php
http://www.ebikes.ca/store/store_stokemonkey.php
Looks like an interesting mid-drive option. But it's listed on that site as being out of stock. This http://www.ebay.com/itm/48V-450W-BRUSHLESS-MID-ELECTRIC-MOTORIZED-E-BIKE-CONVERSION-KIT-Belt-/190801361013?pt=LH_DefaultDomain_0&hash=item2c6ca5b875 on the other hand, is in stock. Anyone have any experience with that ecospeed mid-drive knock-off?melodious said:
MadRhino
100 GW
The Mac is a good and easy solution. I would recommend fitting a plain pedal assist sensor on the crank, and use the torque throttle function of the CA. Properly tuned, this setup will be very intuitive. You will not need to use a throttle, only a switch. When off, there will be no drag and the bike will feel natural; when on, it will add torque according to your cadence. The cadence to torque ratio will be set on the CA, and can be tuned until you find the perfect assistance for your preference.
Rassy
1 MW
Sounds like you are on the right track. While I love my mid-drive trikes, they were built to get me up the 15% grade to my house, and the 20% part in my own driveway without going to high voltage/high amperage systems. While touring you should seldom encounter grades over 10%, and if it wasn't for these steep local hills I probably would have stuck with hub motors. But just to finish up this comment, it's nice to have the motor running at an optimal RPM and not generating extra heat whether I'm going 5 MPH or 20 MPH.
My educated guess concerning the 200 RPM loaded means the hub RPM because there's a pretty good, probably about 5 to 1, reduction within the geared hub motors, so under 50 RPM at the wheel would be pretty slow. However, that number is still subject to a lot of conditions, such as wheel size and moving your tandem recumbent trike on level ground would result in a slower speed than a single lightweight guy on a regular bike. Also, remember that an electric motor pulls harder at slower speeds, and still runs okay without creating too much heat at about half it's unloaded speed.
It will be a couple of weeks before I get the Bafang powered BOB trailer I'm working on completed for some good hill climbing tests. Of course my total gross weight will be under 300 pounds so your thoughts about using a stronger setup makes sense.
To wrap-up, the rating of the motor, within reason, is less a factor than the battery and controller in determining how well the motor performs. So a motor rated by a manufacture at 36 volts as a 500 Watt motor will normally work good with a 48 volt battery and a 20 amp controller, pulling about 1000 Watts during heavy acceleration or hill climbing, and as long as the motor doesn't overheat no damage is done.
My educated guess concerning the 200 RPM loaded means the hub RPM because there's a pretty good, probably about 5 to 1, reduction within the geared hub motors, so under 50 RPM at the wheel would be pretty slow. However, that number is still subject to a lot of conditions, such as wheel size and moving your tandem recumbent trike on level ground would result in a slower speed than a single lightweight guy on a regular bike. Also, remember that an electric motor pulls harder at slower speeds, and still runs okay without creating too much heat at about half it's unloaded speed.
It will be a couple of weeks before I get the Bafang powered BOB trailer I'm working on completed for some good hill climbing tests. Of course my total gross weight will be under 300 pounds so your thoughts about using a stronger setup makes sense.
To wrap-up, the rating of the motor, within reason, is less a factor than the battery and controller in determining how well the motor performs. So a motor rated by a manufacture at 36 volts as a 500 Watt motor will normally work good with a 48 volt battery and a 20 amp controller, pulling about 1000 Watts during heavy acceleration or hill climbing, and as long as the motor doesn't overheat no damage is done.
Thanks for this suggestion: it certainly does sound appealing to have one less lever to fiddle with. Or at least to replace a lever with an on/off switch. I can't say I understand very well how what you propose would work, partly due to the fact that I've never laid hands on a CA, don't know a whole lot about its capabilities, and am somewhat challenged when it comes to technical details of electronics. But I've made a mental note of this possibility and will continue to try to understand how it might be implemented. If I'm unable to figure it out, I think I'll know where to ask for helpMadRhino said:
I definitely have not settled firmly on a geared hub motor. I'm still considering other options like a mid-drive. Mid-drive does seem a bit more versatile for reasons such as those you've stated.Rassy said:
Let me see if I understand what you're saying here: is it that the motor spindle, inside the hub motor, is spinning at 200 rpm, while the hub motor's shell (and thus the tire mounted on the rim attached to the shell) is spinning at 50 rpm's? That is slow. According to my calculations, on a 20" wheel with 1.95" tire on it, the bike would be moving at about 3 mph when the wheel's spinning at 50 rpm's: sound right? With the tire spinning at 200 rpm, on the other hand, I caculate that the bike would be going about 12 mph. If my math is anywhere close to correct, the motor spindle inside the hub would be spinning at about 1000 rpm's in that case.
Ok, time to display my electronics ignorance. I would be inclined to select a 36 volt battery for use with a 36 volt motor. I guess I'm wrong? The kit I currently have paired a 48 volt 10Ah battery with a 48 volt 1000 watt motor, which made sense to me at the time. But I don't, obviously, claim any expertise in this realm. Further explanations about matching battery and motor voltages, or not, will be appreciated.
Rassy
1 MW
I guess I wasn't too clear, but yes, the wheel would be what is turning at 200 RPM under power.
A comment about what MR said concerning using PAS instead of a throttle. If you were to go that route I would suggest that you also have a throttle available for a couple of reasons. If you have to make a cold start on much of a hill it can be real helpful to have a motor to call on without having to pedal first, particularly if you aren't in your lowest gear. Also, if you have a lot of start and stop required, such as in a residential area with a stop on each block, it can be nice not to have to co-ordinate both riders on the tandem through all the gears. Not from personal experience, but my son and daughter-in-law had a tandem a few years ago and really liked not having to get in the lower gears every time they had to stop, after I put a hub motor in their front wheel.
As far as using 36V motors at 48V personal experience is limited to a direct drive 36V brushed hub motor and the brushless Bafang motors. Before finding all the expertise on this forum about 6 years ago I was running a delta trike with a front 36V brushed hub plus two more 36V hubs on a two wheel pusher trailer, all running off of one throttle and about 100 pounds of SLA in the trailer. With some guidance, I tried running at 48V (Main guidance was what can you hurt, if the controller blows just get better ones). Turned out the pusher trailer at 48V without the front hub pulled my hills just as good as the three working together at 36V. My daughter-in-law is still using one of those original brushed motors on the front of the delta trike powered by a 48V Ping that comes off the charger in the mid 50 volts. She doesn't have many hills and didn't need or want the pusher trailer. If you do some searching on the forum you'll find where some guys have run motors at several times their rated voltage.
Edit: Most of the brushless controllers do have low voltage cut offs, so it can be important to match the controller to the battery for it to work properly. Also, if you put more voltage through a controller than some of the components can tolerate the controller will fail.
A comment about what MR said concerning using PAS instead of a throttle. If you were to go that route I would suggest that you also have a throttle available for a couple of reasons. If you have to make a cold start on much of a hill it can be real helpful to have a motor to call on without having to pedal first, particularly if you aren't in your lowest gear. Also, if you have a lot of start and stop required, such as in a residential area with a stop on each block, it can be nice not to have to co-ordinate both riders on the tandem through all the gears. Not from personal experience, but my son and daughter-in-law had a tandem a few years ago and really liked not having to get in the lower gears every time they had to stop, after I put a hub motor in their front wheel.
As far as using 36V motors at 48V personal experience is limited to a direct drive 36V brushed hub motor and the brushless Bafang motors. Before finding all the expertise on this forum about 6 years ago I was running a delta trike with a front 36V brushed hub plus two more 36V hubs on a two wheel pusher trailer, all running off of one throttle and about 100 pounds of SLA in the trailer. With some guidance, I tried running at 48V (Main guidance was what can you hurt, if the controller blows just get better ones). Turned out the pusher trailer at 48V without the front hub pulled my hills just as good as the three working together at 36V. My daughter-in-law is still using one of those original brushed motors on the front of the delta trike powered by a 48V Ping that comes off the charger in the mid 50 volts. She doesn't have many hills and didn't need or want the pusher trailer. If you do some searching on the forum you'll find where some guys have run motors at several times their rated voltage.
Edit: Most of the brushless controllers do have low voltage cut offs, so it can be important to match the controller to the battery for it to work properly. Also, if you put more voltage through a controller than some of the components can tolerate the controller will fail.
-dg
1 kW
Perhaps you should look at the simulator and see how the various motors work in the wheel size, weight, and slope you are interested in. The setting BMC-torque is more or less the same as a 10T MAC I think. But, given that you plan on running this only for climbing with 500 lbs I'd suggest the eZee V2 26" motor. According to the simulator this will handle more load without overheating than the MAC. In a 20" wheel the simulator shows this should be able to handle extended climbs of 10% without ever overheating assuming the two of you can add a couple hundred watts pedaling. At 36 battery volts it tops out at about 17 mph and at 48 volts about 22 mph. Which is pretty pretty slow but matches your stated goals as it climbs really well from around 7 mph up.
dogman dan
1 PW
This brings up something I have needed to educate myself about. More and more, motors are being sold as x rpm. But I have not made myself a chart that translates that to speed for various wheel sizes. To calculate that, I need the tire measurement x the rpm, to get a length in inches per minuite then convert to mph.
250w is a lot of assist. The catch 22 is that because most hubmotors turn too slow when climbing the steeper hills, they overheat. That overheating is sucking down 75% of your watts, leaving you with a lot less assist than you get when cruising on level ground. So depending on how inefficient you are climbing that hill, you might much prefer having 1000w at times.
A slow motor will drop its wattage draw as it speeds up, so if you can pedal up that hill at 5 mph, then you motor up another 10, a slow motor will then be in the efficient speed range and climb the hill cool. While a fast motor may remain "stalled" and keep pulling a lot of power, only to make heat with it unless it goes faster. So with the right winding, you can ride slower up the hill, making less heat.
The slow motor also will do better at leaving stop signs, so you might come to enjoy using it for getting up to 10 mph, then cruising under pedal power. Instead of lots of shifting.
In general, I've come to prefer a 48v battery, with a motor slow enough to keep top speed to 20 mph max speed on my commute bike. It climbs hills better than a 36v battery on a motor winding with similar top speed. At times you do need lots of power to climb well, and the 48v system has 1200w potential, while the 36v system has only 900w. This helps with the occasional short hill that is steeper than 10%. Long mountain passes do tend to max out at 8-10%. But short side roads and driveways to houses or to camp and picknick areas can be very steep
250w is a lot of assist. The catch 22 is that because most hubmotors turn too slow when climbing the steeper hills, they overheat. That overheating is sucking down 75% of your watts, leaving you with a lot less assist than you get when cruising on level ground. So depending on how inefficient you are climbing that hill, you might much prefer having 1000w at times.
A slow motor will drop its wattage draw as it speeds up, so if you can pedal up that hill at 5 mph, then you motor up another 10, a slow motor will then be in the efficient speed range and climb the hill cool. While a fast motor may remain "stalled" and keep pulling a lot of power, only to make heat with it unless it goes faster. So with the right winding, you can ride slower up the hill, making less heat.
The slow motor also will do better at leaving stop signs, so you might come to enjoy using it for getting up to 10 mph, then cruising under pedal power. Instead of lots of shifting.
In general, I've come to prefer a 48v battery, with a motor slow enough to keep top speed to 20 mph max speed on my commute bike. It climbs hills better than a 36v battery on a motor winding with similar top speed. At times you do need lots of power to climb well, and the 48v system has 1200w potential, while the 36v system has only 900w. This helps with the occasional short hill that is steeper than 10%. Long mountain passes do tend to max out at 8-10%. But short side roads and driveways to houses or to camp and picknick areas can be very steep
For the first scenario you outline, i.e., having to start from a stop on an uphill slope, I might be inclined, if the slope were steep enough, to use the assist from a dead stop. But experience thus far indicates that this will be a very rare occurrence: though I'm pretty sure I have done this at some point, I can't recall a particular instance. But it would be nice to have the possibility of doing so, as you suggest. But even with frequent stops in areas where inclines are less steep, I would be unlikely to use the motor to get going from a dead stop.Rassy said:
Yeah, I've seen posts describing that sort of thing. But these are hot-rodders, right? So, by definition, what they're doing isn't going to be of much interest for my scenario, will it? Where does over-volting (if such a word exists) cross into hot-rodding territory, and up to what point might it carry other benefits for my usage scenario? I'm in the dark on that question at the moment.
I'm pretty sketchy on controllers and what I'd need for my intended use. Trying to learn more, though.
Thanks.
I've looked at that simulator (at ebikes.ca). It looks really helpful, though it's a work in progress for someone with my limited technical training to understand parts of what it shows. The thing I'm not understanding at the moment is how you get any sort of heating/overheating information out of it: can you explain? A 26" wheel is not an option for the tandem trike: I have to use either a 16" wheel (front) or 20" wheel (rear) on it. I suppose I could put a 26" wheel on the two-wheeled tandem, but I'd rather stick with the 700c wheel size that's already on the rear. And my hope was, if I go with a hub motor on this rig, to have the (20") front wheel be the assist wheel. 7 mph seems to me a good climbing speed: it's about what we maintain on less steep grades without assist. Unassisted, we drop down to 5-6mph on steeper grades. I'd say we definitely will always be adding, between the two of us, at least a couple hundred watts on uphill runs. Thanks for your input; I'll be giving it more thought.-dg said:
Rassy
1 MW
You are right that the guys that use higher voltage and/or amperage are "hot rodders". I just mentioned this as an indication that the motor itself doesn't really limit the voltage and amperage, it's the controller and battery that determine the voltage and amperage. Of course the motor has physical limits such as overheating, magnets coming loose, etc.
Also, keep in mind that the motor's rpm is almost directly proportional to the voltage. So if a hub motor wheel has a maximum 300 rpm at 36V it will have a maximum 400 rpm at 48V, etc.
Also, keep in mind that the motor's rpm is almost directly proportional to the voltage. So if a hub motor wheel has a maximum 300 rpm at 36V it will have a maximum 400 rpm at 48V, etc.
-dg
1 kW
wayover13 said:
The heating information is in the information box toward the lower right labeled "Overheat in" and give the estimated time you can run that load and speed with out cooking the motor in minutes.
I never suggested a 26" wheel, I'm not sure why you mention it. For your purposes the smaller the better. Of course on a front you need enough load on the wheel to maintain traction.
Thanks for pointing out where that information can be found. I guess some of the graph's less comprehensible technical aspects had me intimidated such that I did not initially spot that. It shows the same result for for the BMC low torque motor, btw, if I'm entering the information correctly.-dg said:
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