Alan B
100 GW
Already covered, apparently insignificant.
2WD (Two-Wheel Drive) FAQ
- Thread starter Kingfish
- Start date
liveforphysics
100 TW
AussieJester said:
Yes, but it's really surprisingly small compared to the other losses.
What isn't small though, is how awful a front hub bike feels to ride. It's like you have to just crash it into obstacles and things rather than hopping up over whatever you want. And then it just spins out if you dump useful power into it...
Alan B
100 GW
How does the weight of a mountain bike fork, wheel and smallish front wheel gearmotor compare to the weight of a motorcycle front fork and wheel?
AussieJester
1 TW
Okedokie.... :wink:
Yes, being cracked over in a corner then getting
on the throttle with a front frock would be scary
Front end feel would be terrible surely. I can see use for it
In slow muddy offroad conditions for sure
Would scare the piss out of me riding at any speed
On the road though....good luck to those using
Or thinking of building a trip wheel drive bike...
KiM
Yes, being cracked over in a corner then getting
on the throttle with a front frock would be scary
Front end feel would be terrible surely. I can see use for it
In slow muddy offroad conditions for sure
Would scare the piss out of me riding at any speed
On the road though....good luck to those using
Or thinking of building a trip wheel drive bike...
KiM
Alan B
100 GW
The OP of this thread made a 2500 mile trip a few weeks ago with dual hubmotor drive. Didn't seem to be a problem.
John in CR
100 TW
amberwolf said:
If cogging of an unpowered motor is the same as powered it's minor anyway, and reaches a fixed plateau as Justin analyzed some time back. If it was significant that mean that the Xlytes with the splayed stators, which cog far less would be significantly more efficient than other hubmotors, but they aren't? All losses are already part of the existing efficiency curves anyway, and as LI-ghtcycle proved running his 9C as a mid-drive with a NuVinci, hubmotors don't run anywhere near peak efficiency except for a small time. Sure there may be commuters running WOT on flat roads for long continuous distances, but they aren't the norm, and for them the only significant benefit would be that having a 2nd motor leaves them never broken down.
While riding around at a cruising speed some bikes may approach peak efficiency with one motor, as I've said the second motor will make little difference in that case. That's not what people looking at a second motor are looking to improve. They're looking to climb hills better or accelerate harder. There's also guys running their motors in a stressful manner who are more common than you're giving credit, and who are running at peak efficiency at cruise that is poor due to too large a wheel as shown in the following graph, a 2807 9C in a 26" wheel with a battery sagging to 93V drawing 39A and edging just above 40mph on flat roads. Note the efficiency at cruise of 78.7% .
That's at cruise on a flat road too, ie the absolute best case for that system, and a second motor is going to increase efficiency to 84% or so at that speed. Then every hill, every headwind, and every acceleration will have even greater improvement.
BTW, my 2nd ebike had a front hubbie running at 3kw peak, and it didn't exhibit any traction or handling issues even in beach riding or on sandy trails either. Sure the weight there was an issue on bumps, but having that front motor pulling instead of pushing it through anything soft or around turns on pavement were a definite plus. As long as the axle torque is addressed, my only real issue with front hubs is the potential for plug braking with a controller failure, so I would stay away from motors with strong regen braking, ie high turn count motors. As far as unsprung weight is concerned, the motorcycle fork assembly I'm using for my 2wd front end had a wheel, brake disc and caliper that weigh about as much as my hubmotor and wheel.
Once I get around to building a dirt ebike, the call of 2wd will be hard to ignore, so hopefully a tough, powerful, and durable geared hubbie becomes available in a 10lb or less size. In the meantime, 4-6kw in the front of my low and long streetbike will work fine and definitely run at greater efficiency and performance than now, since the time I run at fixed speed is seconds, not even tens of seconds. The added weight and better tire, along with the pulling front, will definitely give me more confidence in the curves.
AussieJester
1 TW
Alan B said:
Good for the OP... he could of done the same 2500 miles with one motor too
DogMaN has proven higher poweredfront frocks are dangerous when cornering fast they slip and that was on a high traction Kart track the slick
roads or worse wet roads would be dangerous, i like to ride reasonably fast when i go out for blats about the neighbourhood
i like to feel what the front wheel is doing when i am cornering as i am sure many do, i don't want it breaking lose when i'm mid corner and on a nice lean angle powering out of a corner...(Matt.P has some nice video shot from behind me leaning the bike riiiigth over when cornering on a snakey section of the cycle path on last weekend's group ride
) I have confidence in the front end when i can feel what is happening, i would lose that with a heavy ass frock rumbling about on the front end...If they were any better/safer/advantageous for road use majority of road going motorcycles would be using two wheel drive, been tested by major manufactures in the past, how many mass produced non prototype on road 2wheel drive bikes you seen Alan B? I dont care one iota about efficiency if i need more range i add more lipo, simple... so personally i see no advantage
in two wheel drive the added complexity, weight and cost just doesn't make any sense to me...
KiM
Alan B
100 GW
This thread is not about front hubmotors. It is about 2WD hubmotors which are quite a different thing. Setting up a balanced 2WD power system on a bike produces a different vehicle than a front or rear hubmotor bike.
There have been attempts at two wheel drive motorbikes but the mechanical problems are difficult. With hubmotors the problems are minimal.
A single rear hubmotor on a heavy cargo bike towing a trailer 2500 miles would not have worked as well for KingFish as the dual setup he used which allowed him to achieve much higher average speeds. He has done a big trip with one hubmotor and with two and you can read about it in his several threads on the subject. He has more miles under more conditions with a dual hubmotor than most folks will get to, so it may be worthwhile to read about his experiences. He is also commuting on wet Washington pavement so he can speak to spinout problems if he has them.
For me a front hubmotor is interesting because I have had overheating and traction problems at 10 to 15 percent grades. California has a lot of steep stuff. Some of the roads I ride my ATV on make the hair stand up on the back of your neck. I didn't appreciate a little hill in Marin causing my ebike to lose traction, fall down and nearly melt my motor - I want more capability but maintain the quiet and stealth of hubmotors. With a strong rear hubmotor plus a smaller front geared freewheeled hubmotor I may be able to achieve that in a simple ebike. When I don't need the front hub I can easily remove it and return to my standard front wheel. Or not, as the small front hubmotor is not that heavy or visible. I agree with you that I don't want the front motor to be high powered, and I don't need it to operate at high speed. So I will configure it to work below say 15 mph and produce about 2/3 the power of the rear motor. Above that speed it will freewheel and not consume much power.
There have been attempts at two wheel drive motorbikes but the mechanical problems are difficult. With hubmotors the problems are minimal.
A single rear hubmotor on a heavy cargo bike towing a trailer 2500 miles would not have worked as well for KingFish as the dual setup he used which allowed him to achieve much higher average speeds. He has done a big trip with one hubmotor and with two and you can read about it in his several threads on the subject. He has more miles under more conditions with a dual hubmotor than most folks will get to, so it may be worthwhile to read about his experiences. He is also commuting on wet Washington pavement so he can speak to spinout problems if he has them.
For me a front hubmotor is interesting because I have had overheating and traction problems at 10 to 15 percent grades. California has a lot of steep stuff. Some of the roads I ride my ATV on make the hair stand up on the back of your neck. I didn't appreciate a little hill in Marin causing my ebike to lose traction, fall down and nearly melt my motor - I want more capability but maintain the quiet and stealth of hubmotors. With a strong rear hubmotor plus a smaller front geared freewheeled hubmotor I may be able to achieve that in a simple ebike. When I don't need the front hub I can easily remove it and return to my standard front wheel. Or not, as the small front hubmotor is not that heavy or visible. I agree with you that I don't want the front motor to be high powered, and I don't need it to operate at high speed. So I will configure it to work below say 15 mph and produce about 2/3 the power of the rear motor. Above that speed it will freewheel and not consume much power.
AussieJester
1 TW
Different strokes for different folks i guess...I ride for pleasure not so much commuting
great distances 25km max and im done, but i like to do it quickly and have fun doing it
not limp along ...anyhoot, leave you too your dual frock setups best of luck with them ... :wink:
KiM
great distances 25km max and im done, but i like to do it quickly and have fun doing it
not limp along ...anyhoot, leave you too your dual frock setups best of luck with them ... :wink:
KiM
John in CR said:
Probably true; I was just suggesting the experiment for anyone to see for themselves, if they liked. (assuming they have two bikes and two wattmeters available).
John in CR
100 TW
amberwolf said:
My motors cog pretty good, but it's really just a matter of getting past the initial low speed stuff. If Luke thinks about it, he'll realize how small it is, because he towed me for a mile or so when I ran out of juice on the road. The tow was accomplished holding onto his shoulder, and that was also overcoming a bit of head wind plus rolling resistance of both tires plus wind resistance at towing speed of 20mph+. Whatever excess was cogging resistance of the motor, which couldn't have been much power being transferred through that "tow connection", especially since my out of cycling shape legs did the work for a half mile or so before Luke realized I was missing. He was quite distracted by the bee that had flown up his nose and stung him while in there, so I was happy he realized I was missing at all. 8)
el_walto
10 kW
I'd just like to say that my 2WD got me to work using the same AH as my 1WD in a shorter time. This is because my 1WD would cog like crazy and get really hot as i live on the bottom of a giant hill.
I used one throttle with two controllers for a couple weeks without any noticeable problems. Maybe this worked because I had 2 batteries, one going to each controller.
I used one throttle with two controllers for a couple weeks without any noticeable problems. Maybe this worked because I had 2 batteries, one going to each controller.
The Mighty Volt
1 MW
Does 2WD have application? Yes.
Where?
On extremely heavy broken ground, like rocks or scree, where the bike comes to rest with one of the wheels free of the ground and with no traction.
In that circumstance, power is applied to the grounded wheel to try and free the bike.
Apart from that, I have to go with the conventional wisdom which holds that a single, reliable, rear-wheel drive with good thermal properties remains the best way to go.
Where?
On extremely heavy broken ground, like rocks or scree, where the bike comes to rest with one of the wheels free of the ground and with no traction.
In that circumstance, power is applied to the grounded wheel to try and free the bike.
Apart from that, I have to go with the conventional wisdom which holds that a single, reliable, rear-wheel drive with good thermal properties remains the best way to go.
Kingfish
100 MW
A little History & Perspective:
Single-wheel drive eBikes are cool; not long ago I started out with a FWD eBike – although that is a half-truth:
The kit for the second eBike (the one I call P0) that I constructed came from eBikes.ca and it was ordered-up as a 2WD: One throttle, two CAs, two controllers (I think they were the 25A 6xIRLB4030 and highly modified), and two (F/R) 9C 2806 hubs. The assembly was arrested cos the curious part of my spirit took over and I disassembled the rear 9C hub to find out how it worked
and that’s how my first eBike became a FWD, although secretly I still pined away for a 2WD! The frame of the eBike I ride today (P1) was purchased at the same knowing it was going to become a 2WD – that was back in 2009. I took the FWD eBike (P0) to California on the first road trip as 10S18P LiPo; it had all the batteries over the rear tire which proved to be a mistake as it lead to five broken spokes; the bike and I weighed over 350 lb.s. The value of weight distribution was not lost upon me, nor was the overheating motor.
Advocacy:
A single-wheel (or axle) drive makes good sense for many reasons beyond economy, simplicity, and pleasure: It’s what most of us are used to seeing being driven. Our cars are essentially rear- or front-wheel driven (ignoring the differential effects for the moment) single-axle drive. We understand the principle, it’s easy to manage, fun in the rough, in the turns, and on race day! I have owned many single-driven vehicles: Cars, Motorcycles both On- & Off-Road, a Sand Rail, and even a Honda Odyssey modified for full race (bummer that it had no reverse). I am an advocate of this configuration!
Alternatively, I also enjoy pushing the envelope and wish to explore 2WD bikes and AWD. I own a 4x4 truck which is a godsend in the PNW, although today it’s hoisted on blocks cos in 2009 I overtly made the decision to “go green”. To be honest, I’ve customized my 4x4 to the point that the next mods would have taken it into racing… That’s when the eBike bug bit. :wink:
The PNW is a steeply hilly place; the only level stretch of ground it seems is crossing the I-90 Floating Bridge over Lake Washington. We commonly experience blustery winds, two hundred words to describe rain, three words to describe sunshine, sometimes no summer at all (that’s three consecutive days of sunshine between July or August), and much of the time cloudy dark winter. It’s cold here, though due to the maritime clime and two large lakes it rarely drops below 23°F/-5°C for extended periods. That condition however spells for a lot of Black Ice.
I was 18 years old the last time I owned a street motorcycle (a fun story all by itself). Lacking recent experience, I asked my motorcycle-driving peer last month how he deals with crappy Seattle weather: He said “I take the car to the P&R and ride the Bus.” That just blew me away! Why not create a 2WD motorbike with traction tires?
And now you know a bit about my next project. I like what 2WD offers, plain and simple
Three pages of comments and weighing in:
I find it amusing that some of these posts on this thread go to lengths doing out 2WD: Say what you want, but unless these individuals own one and experienced scores and hundreds of miles over those wheels… how can they expect their opinions could have any value? I would appreciate if these young lads with their copious eBike knowledge would go drive one and then weigh in with meaningful experience. Be real: A couple of miles screwing around down a dirt track do not add up as “experienced”. If the intent is to derail or debase 2WD et al then I suggest they start another thread focused on just that subject because this one is not arguing which is better: I am not interested in that debate because it’s already predefined that we’re here to share, discuss, and improve our 2WD experiences. 8)
Once again: The purpose of this FAQ is to demystify the concepts, point to relevant topics, and provide concise answers. I do not claim or imply that 2WD is the panacea for the masses. I do not claim or imply that “2WD is more energy-efficient than single-wheel“ and vice versa, although I do believe this is a crude statement that requires qualification. Can we talk instead about practical applications and solutions?
Finally, it is with good fortune that I have survived my recent 2WD trek. I have much to say about it objectively, and I am here to contribute. Let’s work together and share the knowledge!
Thanks, KF
Single-wheel drive eBikes are cool; not long ago I started out with a FWD eBike – although that is a half-truth:
The kit for the second eBike (the one I call P0) that I constructed came from eBikes.ca and it was ordered-up as a 2WD: One throttle, two CAs, two controllers (I think they were the 25A 6xIRLB4030 and highly modified), and two (F/R) 9C 2806 hubs. The assembly was arrested cos the curious part of my spirit took over and I disassembled the rear 9C hub to find out how it worked
and that’s how my first eBike became a FWD, although secretly I still pined away for a 2WD! The frame of the eBike I ride today (P1) was purchased at the same knowing it was going to become a 2WD – that was back in 2009. I took the FWD eBike (P0) to California on the first road trip as 10S18P LiPo; it had all the batteries over the rear tire which proved to be a mistake as it lead to five broken spokes; the bike and I weighed over 350 lb.s. The value of weight distribution was not lost upon me, nor was the overheating motor.Advocacy:
A single-wheel (or axle) drive makes good sense for many reasons beyond economy, simplicity, and pleasure: It’s what most of us are used to seeing being driven. Our cars are essentially rear- or front-wheel driven (ignoring the differential effects for the moment) single-axle drive. We understand the principle, it’s easy to manage, fun in the rough, in the turns, and on race day!
I have owned many single-driven vehicles: Cars, Motorcycles both On- & Off-Road, a Sand Rail, and even a Honda Odyssey modified for full race (bummer that it had no reverse). I am an advocate of this configuration!Alternatively, I also enjoy pushing the envelope and wish to explore 2WD bikes and AWD. I own a 4x4 truck which is a godsend in the PNW, although today it’s hoisted on blocks cos in 2009 I overtly made the decision to “go green”. To be honest, I’ve customized my 4x4 to the point that the next mods would have taken it into racing… That’s when the eBike bug bit. :wink:
The PNW is a steeply hilly place; the only level stretch of ground it seems is crossing the I-90 Floating Bridge over Lake Washington. We commonly experience blustery winds, two hundred words to describe rain, three words to describe sunshine, sometimes no summer at all (that’s three consecutive days of sunshine between July or August), and much of the time cloudy dark winter. It’s cold here, though due to the maritime clime and two large lakes it rarely drops below 23°F/-5°C for extended periods. That condition however spells for a lot of Black Ice.
I was 18 years old the last time I owned a street motorcycle (a fun story all by itself). Lacking recent experience, I asked my motorcycle-driving peer last month how he deals with crappy Seattle weather: He said “I take the car to the P&R and ride the Bus.” That just blew me away! Why not create a 2WD motorbike with traction tires?
And now you know a bit about my next project. I like what 2WD offers, plain and simple
Three pages of comments and weighing in:
I find it amusing that some of these posts on this thread go to lengths doing out 2WD: Say what you want, but unless these individuals own one and experienced scores and hundreds of miles over those wheels… how can they expect their opinions could have any value? I would appreciate if these young lads with their copious eBike knowledge would go drive one and then weigh in with meaningful experience. Be real: A couple of miles screwing around down a dirt track do not add up as “experienced”. If the intent is to derail or debase 2WD et al then I suggest they start another thread focused on just that subject because this one is not arguing which is better: I am not interested in that debate because it’s already predefined that we’re here to share, discuss, and improve our 2WD experiences. 8)
Once again: The purpose of this FAQ is to demystify the concepts, point to relevant topics, and provide concise answers. I do not claim or imply that 2WD is the panacea for the masses. I do not claim or imply that “2WD is more energy-efficient than single-wheel“ and vice versa, although I do believe this is a crude statement that requires qualification. Can we talk instead about practical applications and solutions?
Finally, it is with good fortune that I have survived my recent 2WD trek. I have much to say about it objectively, and I am here to contribute. Let’s work together and share the knowledge!
Thanks, KF
Rassy
1 MW
Well stated KF. Back in 2007 when I joined the forum I had already put together my second multi-drive unit, a delta trike with a front hub and a two hub pusher trailer. I don't remember the details, but there were some quick comments concerning it could always be done better with just one "proper" motor. Then there were numerous incidents where controllers were destroyed and spokes were breaking, etc. due to too much concentrated power and weight. Of course most everything was sla then and "BMS" wasn't part of our everyday vocabulary.
Anyway, more to the point, I think we should all encourage everyone to try whatever they want without being too critical. And when we detail our own experiences it should be in a sharing spirit and not presented as the only way to do it just because it's working good.
If I ever decide to go on a multi-day trip with my mid-drive trike, I plan to pull my BOB trailer with a Bafang in the 16" wheel with it's own battery and separate throttle. This will give me lots of cargo space, extra power for really steep hills, and a redundent system if something breaks on the mid-drive system.
So even though building a 2wd bicycle is no longer a goal, everything else about multi-motor builds still interests me.
Looking forward to your two wheel drive motorcycle build.
Anyway, more to the point, I think we should all encourage everyone to try whatever they want without being too critical. And when we detail our own experiences it should be in a sharing spirit and not presented as the only way to do it just because it's working good.
If I ever decide to go on a multi-day trip with my mid-drive trike, I plan to pull my BOB trailer with a Bafang in the 16" wheel with it's own battery and separate throttle. This will give me lots of cargo space, extra power for really steep hills, and a redundent system if something breaks on the mid-drive system.
So even though building a 2wd bicycle is no longer a goal, everything else about multi-motor builds still interests me.
Looking forward to your two wheel drive motorcycle build.
hjns
100 kW
Hi KF,
Thanks for the great faq, and everybody else, thanks for the great discussion! I learned a lot when reading the whole thread!
I guess I am the target public for the faq: a 2wd-wannabe, not burdened by any real electronics/ev skills, let alone experience. Now, the most valuable info for me is really that a 2wd is very well possible, and the problematic areas have clearly been defined. Also, front and rear motor must be matched for kv and current, but Methods told me that in another thread already.
So, as soon as I have a better fs frame, I will order a 9x7 and another of Lyen's 136v 12 fet, and I can experince for myself the difference (if any) myself.
Thanks for the great faq, and everybody else, thanks for the great discussion! I learned a lot when reading the whole thread!
I guess I am the target public for the faq: a 2wd-wannabe, not burdened by any real electronics/ev skills, let alone experience. Now, the most valuable info for me is really that a 2wd is very well possible, and the problematic areas have clearly been defined. Also, front and rear motor must be matched for kv and current, but Methods told me that in another thread already.
So, as soon as I have a better fs frame, I will order a 9x7 and another of Lyen's 136v 12 fet, and I can experince for myself the difference (if any) myself.
SHARKBITEATTACK
10 W
Good info, I would love to build a nasty offroad 29er ebike someday. I haven't read through the entire thread yet, but you don't necessarily need 2 separate motors to have 2wd...
[youtube]a6KVWfI11OA[/youtube]
[youtube]a6KVWfI11OA[/youtube]
hjns
100 kW
Hi KingFish and others,
I have had a nice PM conversation with -methods, and he recommends me to have a 2WD combo, where the fronthub is providing approximately 70% of the torque as compared to the rearhub, to prevent a slipping front wheel. This makes sense to me.
Now, I have a rear HT3525 and a Lyen 150V controller at 30S. So, -methods recommended to me a 9C 2810 fronthub, and told me to simulate it running a 2805 at half the voltage and twice the current. The simulation is below:
According to this sim, front torque is indeed about 70% or rear over the complete velocity range. I was just wondering what other's experiences are, and whether people have been adjusting their choices around motor kv's to this.
I have had a nice PM conversation with -methods, and he recommends me to have a 2WD combo, where the fronthub is providing approximately 70% of the torque as compared to the rearhub, to prevent a slipping front wheel. This makes sense to me.
Now, I have a rear HT3525 and a Lyen 150V controller at 30S. So, -methods recommended to me a 9C 2810 fronthub, and told me to simulate it running a 2805 at half the voltage and twice the current. The simulation is below:
According to this sim, front torque is indeed about 70% or rear over the complete velocity range. I was just wondering what other's experiences are, and whether people have been adjusting their choices around motor kv's to this.
Kingfish
100 MW
Depending on the application, the front wheel will slip more than the rear in most conditions. Through experience, the rear needs equal-to or more power, and not the other way around. To prevent the front from slipping, I placed more battery weight forward and less over the rear.
Perhaps the intention of the PM is to underrate the power to the rear wheel which would in essence provide an alternate solution when the weight cannot be sufficiently shifted to overcome slip – and that would be acceptable as well with the rear still providing assistance.
The one sticky part of the proposal that has me confuzzled is that the front wheel operates at essentially full-voltage whilst the rear runs at ½ which is difficult to imagine in practice: Why split your battery pack so? Think instead to keep all voltage the same and simply adjust the current to suit.
~KF
Perhaps the intention of the PM is to underrate the power to the rear wheel which would in essence provide an alternate solution when the weight cannot be sufficiently shifted to overcome slip – and that would be acceptable as well with the rear still providing assistance.
The one sticky part of the proposal that has me confuzzled is that the front wheel operates at essentially full-voltage whilst the rear runs at ½ which is difficult to imagine in practice: Why split your battery pack so? Think instead to keep all voltage the same and simply adjust the current to suit.
~KF
hjns
100 kW
the differences in volts and amps is to compensate for the lack of 2810 motor in the sim. The sim only has the 2805, but the performance of the 2806 at half voltage amd double amps is similar the 2810 at 126v 45amps.
So, thanks for your input! My intention was to indeed have 126v and 45amps going into both motors. With the 2810 in front, it would deliver approx 70% of the torque delivered by the rear ht3525.
So, thanks for your input! My intention was to indeed have 126v and 45amps going into both motors. With the 2810 in front, it would deliver approx 70% of the torque delivered by the rear ht3525.
Kingfish
100 MW
hjns said:
Ah, got your thinking now! Thanks 8) ~KF
grindz145
1 MW
I love 2wd for two reasons: Power and Power. Obviously not going to be efficient.
I'm really looking forward to my 2wd build. 5304 +9C 9X7. Should be brutal...
Thanks for the FYI kingfish.
So did you just parallel all 3 throttle signals without issue?
I'm really looking forward to my 2wd build. 5304 +9C 9X7. Should be brutal...
Thanks for the FYI kingfish.
So did you just parallel all 3 throttle signals without issue?
Rassy
1 MW
grindz145 said:
In all cases the multiple controllers were sucking off of a common battery pack.
There have been comments in the past by experts that understand controllers that this technique could lead to problems. I tried it years ago and used it a lot and never had any problems, so ignorance is bliss.
This question probably was to KF, but I have paralleled all 3 throttle signals on both two and three controller systems, both brushed and brushless with no problems.
In all cases the multiple controllers were sucking off of a common battery pack.
There have been comments in the past by experts that understand controllers that this technique could lead to problems. I tried it years ago and used it a lot and never had any problems, so ignorance is bliss.
Alan B
100 GW
I have not done this yet, but have been following a number of 2WD builds. Here is my suggestion/plan:
Connect the controller power grounds together very close to the controllers. You want those controllers at the same ground potential. Hopefully within inches of the controllers. The battery feed should be common, heavy, and split very near the controllers.
Connect the ONE throttle wire between the controllers. Determine which controller is the "main" controller (probably the rear drive), and connect the throttle to that controller and run the one throttle signal wire across to the secondary controller. I would twist it with the throttle ground wire on its way to the secondary controller to provide some shielding (or use shielded cable), but not connect the thin ground wire at the secondary controller.
I would not connect the other throttle wires together. Connecting throttle 5V or ground connections together is asking for a problem. It won't necessarily be a problem immediately, but if there is ever a connector glitch or a big voltage spike and the battery current gets diverted onto the throttle wires it will do a lot of damage to the control part of the controller. For safety put a small resistance in series with the throttle lines, say a few K ohms. This might prevent a problem in one controller from damaging the other controller. You want to send the throttle voltage over to the second controller, but if for some reason there was a large voltage difference you want to limit the damage current.
Note that if the two motor/controller combos don't have roughly the same throttle voltage to ground speed curves they won't share the load all that well. They don't have to be precisely matched, but if one is significantly different from the other the sharing will be lopsided.
Connect the controller power grounds together very close to the controllers. You want those controllers at the same ground potential. Hopefully within inches of the controllers. The battery feed should be common, heavy, and split very near the controllers.
Connect the ONE throttle wire between the controllers. Determine which controller is the "main" controller (probably the rear drive), and connect the throttle to that controller and run the one throttle signal wire across to the secondary controller. I would twist it with the throttle ground wire on its way to the secondary controller to provide some shielding (or use shielded cable), but not connect the thin ground wire at the secondary controller.
I would not connect the other throttle wires together. Connecting throttle 5V or ground connections together is asking for a problem. It won't necessarily be a problem immediately, but if there is ever a connector glitch or a big voltage spike and the battery current gets diverted onto the throttle wires it will do a lot of damage to the control part of the controller. For safety put a small resistance in series with the throttle lines, say a few K ohms. This might prevent a problem in one controller from damaging the other controller. You want to send the throttle voltage over to the second controller, but if for some reason there was a large voltage difference you want to limit the damage current.
Note that if the two motor/controller combos don't have roughly the same throttle voltage to ground speed curves they won't share the load all that well. They don't have to be precisely matched, but if one is significantly different from the other the sharing will be lopsided.
Kingfish
100 MW
On my system:
A better solution is to provide a solid independent +5V supply and use that to drive both controllers, bypassing the local 5V regulator circuit. And if I went that far... might as well replace the +12V supply as well. But then we’re getting into 2-channel controller design discussions and less about 2WD
But if you want to talk about 2-channel controller designs, maybe we aught to spin those threads back up! :wink: :lol:
My ½ watt, KF
- Both controllers share GND through the Battery connection. The controllers are wired very close together; about 12 inches apart if measuring the wires.
- I have a “primary” controller that drives all the dashboard controls. Except for Throttle, all of these controls share the same single GND.
- Throttle gets +5V, GND and Signal (SP) from the primary controller. The Signal is then forked to the “Secondary” controller SP pad, and I do not share the any other throttle wire.
- This setup is workable with some flaws: I noticed that if I really get on it with WOT going up an incline that the battery voltage will sag for a moment which likely affects the output of the 5V regulator; the primary will have signal/throttle but the secondary will drop out – unless I feather the throttle.
A better solution is to provide a solid independent +5V supply and use that to drive both controllers, bypassing the local 5V regulator circuit. And if I went that far... might as well replace the +12V supply as well. But then we’re getting into 2-channel controller design discussions and less about 2WD
But if you want to talk about 2-channel controller designs, maybe we aught to spin those threads back up! :wink: :lol:
My ½ watt, KF
