2WD (Two-Wheel Drive) FAQ

Good stuff guys.

• +2 Both motors equal. The field tests agree
• +2 Both controllers equal. Likewise with above I agree completely, although with different power settings to avoid contention. The alternative is a <hint hint> multichannel (initially-dual) controller that understands and compensates when one wheel slips more than the other. Downgrading the front will prevent slippage; the amount though depends upon the terrain and environment and tires. If it were an easy option, I would like to change the ratio of sharing on-the-fly so long as contention was managed. See next item.
• +1 on the Unified Throttle; work needs to be done here to create a commercial offering. As a wishful feature, imagine a secondary ring that could be set on-the-fly that balances attenuates the signal of A||B from 1:1 to < 1. The idea came to me from an old A/V receiver that had two volume controls: Gross & Fine on concentric rings. The load-sharing ring would simply attenuate the selected (or perhaps non-favored) signal. This in my mind would provide quite a bit of control, and complement the 3-Way current control. Ah, here's a thought: The Throttle and 3-Way should be unified as well – right where the thumb can get to it. :wink:

Hmmm <rub chin>, now if only we had cruise control with persistent presets…
<slurp coffee> KF

Hi all,

Just reporting back about my experiences.


I have tried 2WD with front 9C 2810 and rear HT 3525 on 20S3P for a couple of weeks. Initially, I had the 9C axle rotating out of the front dropouts, destroying the dropouts of my Fox TALAS fork. Cause was identified as too much torque and not enough torque arm (only one). After fixating with 2 torque arms, no issues there anymore. I used the unified throttle with dual Hall sensors to 2 Lyen sensorred 12 FET controllers, fed by a single 20S3P pack. The throttle would give first a signal to the rear and at a speed of about 5km/h would also start driving the front motor. Total bike weight was about 30kg including two motors, 2 controllers, 10kg lipo pack.

In short; I did not like it.

Advantages
Hill climbing was super. Just great, and with 10% hills, I felt I could climb forever. None of the motors would even get warm. I could climb them with speeds over 45 km/h, and not even going WOT. Never tried WOT, because all hill-roads here are snaking around the hills, so 45 km/h is already quite fast.

Pulling the trailer with the kids was also super. And biking with a lot of wind was - due to the large weight - also super, with great tracking.

Disadvantages
However, for commuting and drafting through traffic, such a heavy bike is just not fun. It might as well be a scooter. The real advantage of an E-bike for me is it's capability to go where scooters and motors can not go or are not allowed to go. And these are precisely the parts of the road where a lighter bike makes a difference. Therefore, I removed the front 9C motor and the second controller, and continued biking with "just" the rear HT 3525. Initially on 20S, now also on 30S, reaching speeds >70km/h (42mph). On my 2WD, I would feel very insecure at those speeds. 50km/h was really the max. Now, with the lighter bike, 75km/h is a nice challenge, but does not feel unsafe.

Another disadvantage I noticed was the difference in front wheel and the effect on front suspension. With each bump, the front suspension had noticable difficulties dealing with it. No change in front suspension configuration (increase/decrease air pressure, rebound, more/less sag, etc) could get rid of that. Also, the added mass in the front wheel made it much more difficult to deal with more technical parts of an off-road bike trail. I do not have a lot of experience with that, but without the front motor I can much better deal with off-road trails.

Conclusion
So, I reverted back to RWD, and I will probably stick with this configuration. 2WD was a good experience and learning curve for me. Time to move on.

many thanks for sharing your experience Henk, very interesting!

@hjns: Yes, thanks, that was alot of explanation, but very valuable to me. :wink:

So Henk, you got a front wheel for sale now ?

Hi all,

I am happy to see that some people find my experience useful.

No, the front 9C 2810 is not for sale. Within two months we will be moving to a house in a much more hilly area (Dornach-Gempen). Therefore, I will probably try 2WD again as a "plugin". That will then really be a balance between going uphill with superspeed versus going downhill with the added weight of the second motor. I have a feeling I know the answer, but I just don't want to give up on 2WD completely... :x

I think it is important to emphasize in this FAQ that there is probably a huge difference between a high power 2WD setup and a low power 2WD setup. My high power 2WD setup was based around a rear HT3525 at 20S (74V) and with a front motor added to it. This setup was meant for high speed (40mph) commuting, with the occasional 10% hill, and the even less often off-road experience. The HT3525 is about 8kg, and the 9C 2810 slightly less. Therefore, having both motors made for superfast hill climbing and less for off road.

Now, I can imagine that a low power 2WD will handle completely different, especially with the V3 CA and a nice torque sensor as described here. If one would have a 3kg motor in front and a 3kg motor in the rear, together with a 5-6kg lipo pack, I think the weight would be very much less a factor. Of course, 3kg extra in the front is still significant, but here the disadvantages of the suffering handling would maybe offset by the advantages of the 2WD hill climbing.

DIfferential Buffer for Throttle

The large currents flowing through the resistance of the ground cables between the controllers causes their throttle signals to vary. Using a differential buffer amplifier will re-reference the voltage to the controllers ground even when the grounds are varying with respect to each other. I suspect this is causing Kingfish's occasional "shutdown" of his slave controller as it sees throttle input voltages exceeding the allowed max value in some circumstances.



Note that there are many differential amplifier chips out there and not all are suitable for this application. This unit needs to run on 0 and 5 volts and be able to handle a differential input signal below its own "ground". Most of these parts are surface mount but there are a few through-hole parts. Surface mount may be necessary to get the required features.

You can construct a differential amplifier with an operational amplifier and precision resistors, but the precision required for good performance is difficult to attain. Differential amplifier chips are laser trimmed so the resistors match accurately.

Thank you Alan B. I would not have understood this issue a week ago, and it is only because of the very recent work we've been doing on Solving the Variable Ebrake-Throttle Problem that I am able to comprehend the value of Op and Differential Amps. 8)

Very appreciative and well-said, KF

had a look but couldn't see this being asked before

why not just run a more powerful controller, and then power both wheels in parallel ?
(no sensors, or only one wheel with hall sensors)

I've been thinking more and more about 2wd... and this would make it nice and easy... no throttle problem or wheels trying to go different speeds etc.. ?


for me, I think I'd run the rear wheel as it is now, with it's hall sensors, and then just parallel the front wheel in with the 3 phases going to the rear wheel

and jump from a 2kw controller to a 4kw controller
(or even more powerful)

knighty said:

...

why not just run a more powerful controller, and then power both wheels in parallel ?
(no sensors, or only one wheel with hall sensors)

I've been thinking more and more about 2wd... and this would make it nice and easy... no throttle problem or wheels trying to go different speeds etc.. ?

...

Click to expand...

This only works if the two BLDC motors are mechanically phased the same at all times (or are brushed type motors).

I want to make a dual Q100 road bike but the shipping costs from BMS Battery have gone waaaaay up. I'm in Sydney Australia which is relatively close to China and they want $500+ just for shipping to send two wheel kits @ $126 a piece. The total was nearly eight hundred and fifty bucks! I tried to buy a $5 throttle and the shipping was $95!

Seriously, for $850 I could fly to China, spend two nights in a hotel, go to a trade expo and fly home with the Q100's in my hand luggage. (If I had the time) :? .

So my question is; Are there any other suppliers of the Q100 motors that have more reasonable shipping prices?

Try green bike kit : 420$ for 2 Q100, one front and one rear @115$ each.

http://www.greenbikekit.com/

Those may be the same company:
http://www.endless-sphere.com/forums/viewtopic.php?f=3&t=44684
as well as ecitypower.

Or they might simply be run by ex-employees of BB/EP

This bike is about to be three wheel drive with pusher a trailer ,,, three hubs in three 29ers with three disk and regen brakes
[youtube]uJwfntUt3Z0[/youtube]

I want 50mph up hill
Stage three includes
upgrading all wires
Ceramic bearings
Hempfiber aero kit

That is some great riding Corbinfiber but you have to admit those are pretty short hills. What happens on a mile or 2 of 10%? Looks like "melt city" for the motors.
otherDoc

I live in hollywood los Angeles and you know the mountain with the hollywood sign? I traverse it 15 miles at WOT 35-40 mph and the motors and controllers barely warm up,, my third motor i hope will get me closer to 50mph up it,,, and the third Disc brake will be nice going down it

Just a brief note. In the past week I noticed a tiny small fact that I have driven over

5,000 Miles as 2WD!

Hoisting a beer (at home) in celebration of this minor milestone on the advocacy for 2WD.

It's not for everyone. Just those that dig it. :wink:

Cheers, and well... more cheers! KF

Kingfish said:

5,000 Miles as 2WD!

Hoisting a beer (at home) in celebration of this minor milestone on the advocacy for 2WD.

Click to expand...

2WD=7500mi - and a celebratory beer whenever possible!

Hey everyone first post.

I was wondering if it was feasible to use a 2WD setup on a two wheal push trailer. From what i have been reading it seems that one motor is always going to want to make more torque than the other. And obviously in this kind of setup you would need both motors making the exact same amount of torque regardless (within reason) of RPM

Hi JB

Welcome to ES

With regards to pusher trailers: It didn’t work out for me. Whether it was due to the design or configuration, my attempt (from the first time I tried to go to California in 2011) was forestalled by the tremendous uncontrollable torque along the length of bike and trailer. This issue was eliminated by applying two design corrections: By stiffening of the tubular trailer frame via structural foam injection and by moving the motor from the trailer to the bicycle – effectively creating the 2WD ebike.

Moving the motor to where both are fixed on the same frame eliminated the possibility of being overdriven by rearward force. In my mind, a pusher-system should alleviate some of the drag although not to the point of becoming the prime mover - least the tail wag the dog.

By suggesting having two motors on the trailer would imply that very thought: That the trailer is the prime mover. Is there a plan to have a motor on the ebike as well? If so – it will have to apply more than 50% of the power in order to properly lead.

That aside, it might be easier to have one trailer motor driving a differential rather than synchronizing the torque of two independent motors along the same axis. The 2WD recumbent-trike guys might have a better answer.

Curious, KF

There have been various pusher-trailer threads and designs here on ES and elsewhere, some of which are 2WD. I don't have direct experience with them, but some have had the problems KF had above, and couldn't use them as intended because of it. Others do not have the problem or else they just live with the issues and learn to ride it out.

On my planned 2WD pusher trailer (discussed in one of my Flatbed Kennel Trailer threads I think Mk2), it probably won't be the only power on the bike, and will simply be powered so it can take some or most of the load of hauling huge heavy things around (where now that's done by the bike's 2WD motors). The bike itself would still have it's own motors with probably sufficient power to take over if necessary, albeit at lower accelerations and speeds than with trailer power too.


One thing to keep in mind is that it also matters where you attach the trailer hitch, and how that affects the way forces pushing forward along the bike frame will affect the bike's own drive and traction.

If you ahve a seatpost mount, it's going to try to push the rear wheel up and off the ground.

If you have a mount that is lower to the ground than most of the mass of the trailer, and is behind or at the rear axle mount, it should try to push the rear wheel down into the ground which could lift the front wheel off the ground, especially during braking of the trailer load.

If you have a mount that is only on one side of the bike, it may try to push that side of the bike away from the center of direction of travel, sideways, during straight travel. During turns, it depends on which way you turn how it will then behave.

If you have a mount that pushes along the axle line of the bike and along the center of mass of the trailer, and is at or behind the rear axle mount, and is at the center (and/or attached to both sides of the bike) it is probably the best balance of forces, applying most of the pushing thru the bike in a way that does the least to force you to constantly correct steering and weight distribution.


Keep in mind I haven't actually gotten my pusher trailer(s) done enough to actually test any of the above; it's just my thoughts based on others' posted results.

Hi Kingfish and Amberwolf. Thanks for the reply

I'm sorry for the lack of detail in my original post as I was still reading other threads in other tabs and my head was still swimming in all the new information I had found. My question above was in regard to just one facet of a much more complex project I have in mind for a long distance touring rig. The idea is to take the concept of a tear drop style trailer and further shrink it to a bicycle size trailer. As insane as that may seem I do my road trips in late winter and very early spring since I fight wild fire in the summer for extra income. So I honestly do want a hard sided shelter to sleep in. And tents get old as I almost live in one late July to mid September. So this things going to be heavy, probably on the order of 200 to 250Lbs. But I do have some experience with building light weight camp trailers from a previous job. Where we made them out of laminated foam board over a steal sub frame. However I digress.

My plan is not to have the trailer be the prime mover. But I have to admit I don't have the towing rig fully pined down. What I do have is a older Trek ride plus with its Bionx drive system and a failing battery. One thought that comes to mind is to remove the cells from that battery and set up the old battery case up as a adapter to use a external pack. But that leaves me with still having a 350W motor and it locks me into using a 37V LiMn pack or a 36V LiFe pack with a different charger. To be honest the only reason I'm considering this route for a tow rig is because I love the way the Bionx system operates while riding. The better option for the tow rig would be to start over on another bike and build something with a larger motor probably running around 800 to 1,000W with a 48V system. And then I won't have a peddle assist like I do with my existing bike. In both cases I think its desirable to have power on the trailer its self so the motor on the bike won't have to work as hard on the mountain passes we have out hear on the west coast. In the first case I was thinking to only run the motors on the trailer at 100 to 125W each and in the second case I could go up to 250W each. And only when going up hill. And I was planning on using gear drive motors with a free wheal.

I honestly think the best use of my time and money this fall or winter will be to get the tow rig sorted out. I'm just trying to get a better understanding of 2WD drive systems for when and if I decide to ad motors to the trailer. And I like learning from other peoples experience. It saves a guy time money and frustration.

Oh Kingfish I did find and read about your road trip to California. It was truly inspiring and I think I can do the same. I just have to do it before the weather gets nice.

First a note: I think it would be best to move your questions/etc to a new thread so your project isn't buried in a FAQ; more people might see it and help you that way. If you like I can do that for you and then PM you and any repliers here with the link to it.

JoeBaker said:

To be honest the only reason I'm considering this route for a tow rig is because I love the way the Bionx system operates while riding. The better option for the tow rig would be to start over on another bike and build something with a larger motor probably running around 800 to 1,000W with a 48V system. And then I won't have a peddle assist like I do with my existing bike.

Click to expand...

Well, if you're going with a different bike/motor setup anyway, you could buy the Cycle Analyst v3 and THUN (or other supported) BB torque sensor, and make a setup that works similar to BionX but with much easier adaptability to different motor, controller, or battery setups. You can also use regular Pedal-Assist Sensors (PAS) that just sense pedal rotation rather than force on the pedals, but that one won't work quite like the BionX system does. It'd be significantly cheaper, though. But either way it can be used with basically any controller or motor or battery. Also, you can keep a throttle with it, too, so that if for some reason (injury, etc) you can't pedal at all you can still use the system to get somewhere.

Ebikes.ca is the place to go for that setup. There is also a thread about the whole thing here:
http://www.endless-sphere.com/forums/viewtopic.php?f=4&t=37964
which also has links to FAQs about it and an unofficial manual and setup wiki page/etc.

In both cases I think its desirable to have power on the trailer its self so the motor on the bike won't have to work as hard on the mountain passes we have out hear on the west coast. In the first case I was thinking to only run the motors on the trailer at 100 to 125W each and in the second case I could go up to 250W each. And only when going up hill. And I was planning on using gear drive motors with a free wheal.

Click to expand...

If I were building it so that it isn't hte prime mover, but basically is trying to make the trailer a non-load to the bike, I'd want to put a sensor setup on it that determines load on the hitch/tongue, and roadspeed of bike's driven wheel, and trailer's driven wheel(s), and throttles the trailer motor(s) so that they do not push any harder than is necessary to try to match the roadspeed and/or keep the load on the tongue zero, or minimally positive, but never negative.

Or, I would have a separate throttle for the trailer system on the bike, and simply learn to control it that way myself, whiel also operating the bike's motor system (either by pedals or a separate throttle or both).

The first is essentially how I want to do mine, but I don't think I can actually build that with stuff I have around already, so I will probably just learn to do the latter instead.

Hello, I am a user of a 2WD e-bike. It's powered by 2 x Q100 36V/201rpm and 2 x 36v/14A controllers. It is perfect for my region, the Alpes. But I would like a bike equipped for much more speed, still with uphill ability. So I was thinking of 2 x Q100 24v/328rpm and 2 x 36V/23A controllers. I have simulated this configuration on the ebike.ca simulator and it looks perfectly OK: max speed 53 km/hr, no overheat up to 7.5% grade.
Has anyone tried this configuration? Or do you have any concern with it?
Thanks.