Dual "fast wind" mini-motor build

[motomech]

I put this in this section because, as far as I know, this is the first documented 2WD install using the "328" "fast wind" mini-motors and one of the initial test results is a little suprising to me. But it shouldn't have been as the Ebike CA's simulator had predicted it.
But first, the install, which consisted of two Ananda Q100 36V 328 motors. These kits come with a very small 15A controllers. Except for exchanging the main battery to controller connectors to 4 mm bullets, the kits were installed "as supplied' and not modified. I did install an extra bearing in the un-supported end of the DNP freewheel.

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Both kits were very easy to install. The 9-speed DNP free wheel fit in the standard drop-out with a plain washer inside the chain stay on each side.
The rear disc. lined up without drama, but the rim was slightly off center. As supplied, it needed truing and a spoke adjustment, so I combined those two operations with a bit of "dishing"[a misnomer here, as I only moved it over a few milimeters].
The frt. kit was, if anything, even easier to install. The wheel was ok out of the box and I had already clearenced[filed]the drop outs to fit a MXUS geared motor.
Fitting the mini- motor's 12 mm axle does not require 'deepening" the drop-out to center the axle as does a 14 mm axle. Only a small amount of widening and contouring to match the half-round portion of the axle. With the correct size round file, a few passes is all that is needed.;

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And since the Q100 has a smaller diameter than the MXUS, it didn't have any of the brk. rotor/caliper to motor interference issues the first install did.
Although I had several styles of torque arms to try, niether frt. nor rear, left nor right offered any easy mounting options, so I didn't use any, I did use the supplied "torque washers" on all four corners. These are thick spacers with a "tab" that fits in the open drop-out end, offering a little more material to resist rotation than the axles alone do.;

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As I have mentioned, this bike had been fitted with a MXUS frt. motor and since that was my first and only foray onto Ebikes, I will be comparing the MXUS[with the stock 17A controller and also with the apply named Lyen Mini-Monster controller]with the Q100 motors, singly, and combined.
The only change to the platform is the substitution of the original 26" wheels for a pair of 24 inchers. This is a large framed bike and with my 29" inseam, I always felt as if I was riding a step ladder. The 24" tires are Skinny Kats from Bike Tires Direct

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"Pepe", the test mule with the MXUS.;

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Pepe, with dual "Cuties".;

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The "rat's nest" of connectors go in the bag.;

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The frt. controller goes inside with the wiring, the rear was placed in a sm. mesh bag which went into one side mesh pocket.

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The left switch is the main/rear motor on/off and the right controls the frt. motor. I use a Lyen left-hand, half-twist throttle , so it is easier for me to reach down with my right hand.
I used the most simple of throttle options, only paralleling the signal wire from the main/rear controller over to the aux./frt. controller. The frt. motor will not run if the main controller is turned off, so frt. motor only is not an option. An interesting operational note is, the frt. system can be dis-engaged with the throttle held open, but can only be brought back on-line if the throttle is closed and re-opened. Having the frt. system switch on the H.bars would have been more convienent, but I only had one and I'm using it to arm/disarm the cruise control[on rear system only].
Temp gauge is on the controller in the bag.
Some wiring details.;

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[motomech]

Well, I'm having too much fun to start compiling hard data, so that will come later. For now, just thoughts and impressions.
This morning, I wanted to get a work-out on the way to Macdonalds , so it was rear motor only for the three mile round trip. The first thing noticed is how quiet the Q100 36V is. At half power, a walker three feet away wouldn't know it running. It's also very smooth with no throttle twitchyness at all. Just grab a handful and shift up and down according to load and speed. Of course, noise and twitchyness are things one would associate with power and at 12S Lipo and 13 to 15 Amps, there isn't much. And with this controller, what you see is what you get. The CA reports no wild peaks when hitting the first steep part of a hill, MaxA never excedes 15.5A. The Lyen 23A controller coupled with the MXUS, by contrast will see peaks up to a 38A
The Q100 with the KU63 controller seems soft and friendly, almost feminine. The MXUS with it's 17A controller[peaks in the 20'sA]has a bit of attitude. It growls at you if you "dog" the throttle too much at too low a speed and in a race, it will walk away from the Q100 and it's controller anytime, anyplace.
All this makes for a wonderfully blissful pedaling experience with the Q100 until the first hill comes into view.
My test hill is in the 10 to 12 % range.
The MXUS will churn it's way up with what help I can provide at about 9 mph with the stock controller and 12 to 13 mph on the Lyen. It's not liking it and let's you know, but it digs in and does it. With the Q100 and Ku63, I wasn't a third of the way up when it was clear that without getting into a gear that wasn't readily available to me, we weren't going to make it, so at 5 mph and falling, I made a u-turn and headed back down.
Ok, so a 2.3 Kg, high speed motor with current limits of 15 Amps trying to haul a 250 lb. rider doesn't climb well, not exactly ground breaking news. But how would it climb on two motors?
We'll have to wait and see because I took the long way around, up and up to where the water and radio towers are. It's a long gradual decent of a few % back to my neighborhood, but starts out flat. With moderate pedaling, the top speed seems to be in the 20 to 21 mph range. It's not hitting the rpm wall, it's just running out of power. Kind of like the Nascars with the carb restrictor plates. The induction system is capable of rev'ing to the moon, but the carb openings are holding it back. In this case, it's being current limited.
All this is plain to see on the EbikeCA simulator. using the favorite mini sub. motor, the Ezee, in this case the 20 incher, with the throttle @ 97%, 46V, 13A, we see the power curve is more like a plateau. Instead of a peak that one would see with a more focused motor, the power line past the no-load mark continues horizonally. It's this proximity opf the power line under the load line that makes this a great assist motor. A strong cyclist can reach down and continue to have assist two, three or more mph past the no-load.
As speed increases up to 25, 26 and eventually 29 mph, the CA tells me that the motor/controller is still trying to input. It's reading 200 Watts at 30 mph!

Next, 2WD drive

[motomech]

2WD is a blast, it's hard to stay out of it.
The Hill can be taken at 12 mph pulling 1200 Watts, showing "never overheat" on the Ebike Ca sim.[only 600 Watts though each motor]. Truely a case of each motor helping the other to stay in a reasonably efficient range[72%] and losing too much to waste heat.
Where the dual drive system really shines is off the line. The throttle response is smooth and controlable. A skilled rider could do great "stupid Ebike tricks" with this set-up.
My morning route takes me across a couple athletic fields[before school]and up one grassy slope, wet with dew. And with the frt. mounted motor I would usually spin-out near the top. In 2WD it motors up with nary slip. Even with the "street" tires I'm running..
Top speed runs, flat, no wind or pedaling, produce 26 mph on 12S, 28 mph on 13S. So, it looks like 30 mph is doable on 14S[and I weight 250 lb.s!]. One motor speed remains the same on either 12S or 13S, 20 mph. I knew, since one motor was "current limited", that there would be a significent increase when switching into 2WD, but I did not expect gains of 6 and 8 mph.
I'm very happy with the results and the versatility of this build. One motor drive is perfect for assist and the second motor is great for "squirting" across busy intersections and the ocassional "killer" hill.
Using one small geared "fast wind" motor comes with limitations, but by coupling a pair together, these limits are overcome, actually turning them into strenghts.
Also, once I started running the MXUS sensorless with a hard-hitting controller like the Mini-Monster, I started having concerns about the gears. Too much throttle with the motor not sync'ed-up and I could almost feel the teeth of the gears gnashing. One can only hope that be sharing the load, two low-powered gears motors will not suffer "teething problems".
One area where motor synchronicity doesn't seem to manifest is in efficiency. I'm seeing low 20's Wh on one motor and and low 30's on two. The single MXUS would do as well as the single Q100, even running higher currents. I'm thinking the MXUS with the rider pedaling in the high teens/low 20's mph would hard to beat in conserving battery power.

I also think, that for Dollar value, this set-up matches up well with any single larger geared motor, with only the BMP costing less.
And the argument that 2WD is overly complicated doesn't wash in this instance. If anything, this approach is more simple, at least on this chassis. No need for custom torque arms. The throttle was a one wire deal and since each system retains moderate power levels, I retained all the stock connectors, even wiring each controller though it's own 30Amp automotive switch.
And at these power levels, there is no need to mess with frt. to rear power differential. There is no tendencey for the frt. to over-power the rear. The bike now has a "taunt and planted" feel it didn't have with a single higher powered frt. motor, although much of that must be attributed to the switch to 24" wheels and the excellent Skinny Kat tires[these deserve their own review].
Overall, this should keep me happy for awhile. Except for shunts, they keep beckoning me, with whispers of "mod me", "mod me"

[WhatcomRider]

Thanks for the report, motomech. I have been intrigued by the idea of running dual "Cuties" for quite some time now. I am glad to see that you are doing it and are pleased with the results. I am not sure if this is technically correct, but my view is that each motor pulls half of the air resistance load as well as half of the gross weight up inclines, resulting in a speed boost over a single motor. My first build might consist of a dual setup with the same motors in 20" wheels on 16S LiFePO4, so I run the simulator using the 20" eZee motor and wheel at 52V (16S) / 15A / 50kg (110 lbs), the latter being ONE HALF of my estimated bike+rider weight. I like the way both the efficiency and power curves are relatively flat from 50% to 100% speed, and that the motor power is around 600W max with efficiency above 75% in the whole of that range (12 to 24 mph). The eZee motors are built to sustain that level of power (presumably not overheating even on a 25% grade in a dual 20" setup!). Of course the cheaper and lighter Q100s are not going to perform that well, but perhaps ATF (oil) or other creative cooling methods could boost their performance. Then there is the question of how well the gears (double planetary, IIRC) are to going hold up while running over their rated power. Perhaps in the future - after your inevitable mods - you will be able to give us a better idea of the power handling capability of these motors in your nifty setup.

[motomech]

Thanks for the report, motomech. I have been intrigued by the idea of running dual "Cuties" for quite some time now. I am glad to see that you are doing it and are pleased with the results. I am not sure if this is technically correct, but my view is that each motor pulls half of the air resistance load as well as half of the gross weight up inclines, resulting in a speed boost over a single motor. My first build might consist of a dual setup with the same motors in 20" wheels on 16S LiFePO4, so I run the simulator using the 20" eZee motor and wheel at 52V (16S) / 15A / 50kg (110 lbs), the latter being ONE HALF of my estimated bike+rider weight. I like the way both the efficiency and power curves are relatively flat from 50% to 100% speed, and that the motor power is around 600W max with efficiency above 75% in the whole of that range (12 to 24 mph). The eZee motors are built to sustain that level of power (presumably not overheating even on a 25% grade in a dual 20" setup!). Of course the cheaper and lighter Q100s are not going to perform that well, but perhaps ATF (oil) or other creative cooling methods could boost their performance. Then there is the question of how well the gears (double planetary, IIRC) are to going hold up while running over their rated power. Perhaps in the future - after your inevitable mods - you will be able to give us a better idea of the power handling capability of these motors in your nifty setup.

Now that I have some time riding this set-up, I can go back and look at the parameters I was using in the sim. and play with the varibles and see what changes will rectify the actual results with the predicted results.

...but my view is that each motor pulls half of the air resistance load as well as half of the gross weight up inclines, resulting in a speed boost over a single motor.

If I half my weight, the climbing results on the sim go way askew of the real results. Much closer to use the actual number in the sim. I believe that Justin, in his genius,had made allowances for wind and rolling resistance so I consider that pretty much a non-factor. Not much we can do about it anyway.
I'm seeing that the thing that makes the most difference is Current. If I reduce the value the 13 Amps, all the climbing performance results seem to fall into place. Also, the sim" Batt. Power reading of 660Watts is almost exactly what I see as a one motor Max on the C.A.[2 motor 1280Wmax].
Using,
52V
13A
330 lb.
24" wheel
MTB
I get,
1 motor 10% climb below 5 mph-true
2 motor 10% climb 12.5 mph-exactly
I believe the biggest gain in 2WD climb is because each motor is helping the other maintain a higher rpm and thus, in a high efficiency level.
Then, if I reduce the Current even further to 10.5A[everything else the same] and run the top speed numbers, I get these sim results,
one motor 21 mph-actual 20 mph
two motor 27.5 mph, actual 28 mph
I'm not savvy enough about this stuff to understand why, but I need to ck. the Wmax-2 motor, top speed next time I'm out.
so If we use the same "correction factors" with your proposed build.
52V,
13A,
20" wheel,
220 lb.s
MTB,
we get,
one motor 10% climb-9.5 mph
two motor, 10 % climb-19.5 mph!!!
Climbs like a Mountain Goat.
A further correction to 10.5 A, we get,
one motor top speed-21 to 22 mph,
two motor top speed-25 to 26 mph
Still, a very nice range indeed.

The eZee motors are built to sustain that level of power (presumably not overheating even on a 25% grade in a dual 20" setup!). Of course the cheaper and lighter Q100s are not going to perform that well,...

Of course lighter mean less mass to absorb and transfer heat, but I don't think "cheapness" is a factor here. I've been inside these critters and they seem well built and engineered.

but perhaps ATF (oil) or other creative cooling methods could boost their performance. ...

Tried it, the ATF poured out the right side bearing, all over the disc...fail

Then there is the question of how well the gears (double planetary, IIRC) are to going hold up while running over their rated power.

My sense is, that on the street and no curb jumping, no gear problems. I used to ride the MXUS off road and with these low powered motor, it's not power that's going to strip the gears, it's load stress. And it's pretty easy to know when you are doing that. You can almost feel them getting ready to bend. And my understanding is, that the compound gears, with more surface area, have the potential to be more durable.

Perhaps in the future - after your inevitable mods - you will be able to give us a better idea of the power handling capability of these motors in your nifty setup

Once you have one of these kits in your hands, it becomes pretty clear where the choke-point is. These kits use a tiny 9-pin connector for the lower motor controller junction and while they are super convienent, they don't allow much room for wiring. I'm guessing the phase wires in the supplied lead are 22 Awg and the Halls are a thread-like 26 Awg.
So I suspect the wiring inside the motor melting would be the Achiles Heel for these things. The archives here confirms this. High mileage or over-voltled mini motor seem to suffer hall wire damage first. In the case of Russell's[the dual fast wind cute idea was his] over-volted and well used Bafang, the gears looked fine.
Bottom line, at less than $80, plus shipping for a motor ASM., I wouldn't fret too much over the Q100's reliablity.

[dogman]

Interesting read. I keep meaning to get around to a dual motor bike but never seem to do it. When I feel perky, I end up going for a romp on the trail bike instead.

Been planning to try dual 2810 nine continents on my longtail cargo bike. That would mean 2000w to climb hills, but more likely no more than 600w to 800w would actually pull through each motor. Like your setup, time to overheat, infinite. Yet able to haul a bike load of weight up that hill.

Keep the data coming, it's priceless.

[kfong]

A dual motor setup with the smaller geared motors is the only thing left for me to want to try once I get my mid drive hub motor finished. My only concern is how well these gears hold up with trail riding abuse. They are cheap enough to try, but I'm not convinced they can last since the gears look to be just plain nylon. For regular street riding I'm sure they are fine, but it's the trail riding capabilities that I'm interested in.

[cal3thousand]

I like what you're doing here. Getting ideas...

[motomech]

Interesting read. I keep meaning to get around to a dual motor bike but never seem to do it. When I feel perky, I end up going for a romp on the trail bike instead.

Been planning to try dual 2810 nine continents on my longtail cargo bike. That would mean 2000w to climb hills, but more likely no more than 600w to 800w would actually pull through each motor. Like your setup, time to overheat, infinite. Yet able to haul a bike load of weight up that hill.

Keep the data coming, it's priceless.

Thanks D.man, kudos mean a lot to me coming form you.
Not much to report, did a cross town run yesterday where I had to deal with traffic. To maintain the pace, I was switching back and forth between 1 and 2 motors. As one would expect, power useage was right in the middle of one vs. two, in this case, 27 Wh's.
I want to try the MXUS sensorless up frt. with the Ananda rear. I have a feeling the rear motor would supply just enough of a "push" that sensorless start-up sync issues would disappear. But there are connector issues that I need to work around first.
In the same vain, I've been mulling over what would be the best set-up for light duty trail riding.
My thinking at the moment is this,

Seat height be damned, it's got to be 26" wheels, I'm already hitting the pedals and the chain ring in street riding.
If I was starting from scratch, I would probably go with a pair of MXUS motors. Cell_man's wheels are stronger built than the BMS Battery hoops. A pair of MXi[plural?]would be stronger performing than a pair of Cutes, with the survival rate of the gears being inversely proportional to the power applied.

EDIT, Cell_man no longer carries the MXUS kits. Up-coming 2WD off-road build using the EZee 400W geared on rear, mini on frt. in the works.

[motomech]

double post

[Russell]

Hello Motomech,

So you did it...DUAL CUTE's...very cool

The more I think about the advantages of two small motors compared to one larger motor the more I like the idea! Some day I will replicate your setup but for now I'm still working out the details on my latest build.

One question; what caps and FETs are in the KU-63 controllers?

-R

[WhatcomRider]

I know the question was directed to Motomech, but I suggest you take a look at this impressive web page where you can get photos, specs, schematics, and mod tips for the KU63 controller: http://www.avdweb.nl/solar-bike/electro ... oller.html.

The 36V power rail caps are rated at 63V and the six 2SK4145 MOSFETS are rated at 60V / 84A / 10 mΩ MAX.

[teklektik]

Not much to report, did a cross town run yesterday where I had to deal with traffic. To maintain the pace, I was switching back and forth between 1 and 2 motors. As one would expect, power useage was right in the middle of one vs. two, in this case, 27 Wh's.
...
A pair of MXi[plural?]would be stronger performing than a pair of Cutes, with the survival rate of the gears being inversely proportional to the power applied. But in the end I just went with another pair of Q100's, but 201 winds.
...
And taking a page out of your book, I'll have two pair of controllers, one pair stock for summer and a pair I can shunt mod for winter. Or 1200 to 1300 Watts-summer and 1800 to 1900 watts for winter.

Very interesting build. I would recommend that you strongly consider getting a CA v3 on there with a limit switch so you can throttle the two motors back to the power of one. I find that the two motors run together at half power outperform a single motor at full power - it seems they are hand-holding each other up into a better efficiency point giving better usable power for the same watts. I was originally just switching between one and two motors as you are doing, but recently added the two-motors-as-one mode and it's a hit .

Also, the throttle ramping on the v3 is a real game-changer for gear motors - you can go WOT off the line and it just eases away smooth as can be w/o shredding clutches and gears.

A CA Vaux limit switch would also let you get away without the two seasonal sets of controllers - just build up one pair with 'winter' capacity and let the CA limit them back for summer mode. I appreciate you are going for a simple setup, but the new CA v3 is a huge improvement over the previous model and well worth the minor complication. Also, by using it to source the power for your throttle, you can get around your current issue of needing a particular controller active to juice the throttle.

Anyhow - just a thought

[motomech]

Hello Motomech,

So you did it...DUAL CUTE's...very cool

The more I think about the advantages of two small motors compared to one larger motor the more I like the idea! Some day I will replicate your setup but for now I'm still working out the details on my latest build.

One question; what caps and FETs are in the KU-63 controllers?

-R

So I guess you saw Cassino's web site on KU63's. He seems rather obsessed about that little controller

[Russell]

I've been happy so far with the controllers I've purchased from BMSbattery, they're inexpensive and feature-packed, but I've never used the little KU63. The two KU93's I have (a 48V and a 36V) both use 63V caps and 9 HY1707P mosfets (70V/80A, Rds on = 0.06 mohm).

-R

[motomech]

Not much to report, did a cross town run yesterday where I had to deal with traffic. To maintain the pace, I was switching back and forth between 1 and 2 motors. As one would expect, power useage was right in the middle of one vs. two, in this case, 27 Wh's.
...
A pair of MXi[plural?]would be stronger performing than a pair of Cutes, with the survival rate of the gears being inversely proportional to the power applied. But in the end I just went with another pair of Q100's, but 201 winds.
...
And taking a page out of your book, I'll have two pair of controllers, one pair stock for summer and a pair I can shunt mod for winter. Or 1200 to 1300 Watts-summer and 1800 to 1900 watts for winter.

Very interesting build. I would recommend that you strongly consider getting a CA v3 on there with a limit switch so you can throttle the two motors back to the power of one. I find that the two motors run together at half power outperform a single motor at full power - it seems they are hand-holding each other up into a better efficiency point giving better usable power for the same watts. I was originally just switching between one and two motors as you are doing, but recently added the two-motors-as-one mode and it's a hit .

Also, the throttle ramping on the v3 is a real game-changer for gear motors - you can go WOT off the line and it just eases away smooth as can be w/o shredding clutches and gears.

A CA Vaux limit switch would also let you get away without the two seasonal sets of controllers - just build up one pair with 'winter' capacity and let the CA limit them back for summer mode. I appreciate you are going for a simple setup, but the new CA v3 is a huge improvement over the previous model and well worth the minor complication. Also, by using it to source the power for your throttle, you can get around your current issue of needing a particular controller active to juice the throttle.

Anyhow - just a thought

Honored Sir that you would drop in. I have drooled over and studied your spectacular 2WD Yuba build on more than a few occasions. It's quality of craftsmanship certainly something to aspire too.
I need to start reading about C.A. V3, but frankly this years Ebike budget is dwindling. The Lipo Gods have not been kind to me as of late and I have had to buy more of the spiteful stuff recently.
At any rate, by the time I finish reading the 30 page[and growing]thread on the V3 and understand it's functions, it will be next year and I can up-grade. It's funny, even though I don't use the functions of my Sm. Screen CA, I've become rather attached to it. Destined to be a classic.

[motomech]

Jeeze, what's up with these dual posts?

[motomech]

Ok, more changes, I just can't leave anything alone.
Well, there were a couple of things that were bothering me about the dual fast wind build, one mechanical and the other electrical.
First, the electrical.
We talked about the 'interaction effect" of running two like systems in conjunction and I think I was experiencing one of an undesired nature.
Namely, the throttle feel. Running both systems at the same time produced a harsh feeling twitchiness that I didn't care for. Just not smooth and I know it's not the throttle itself because I have used the Half-twist with the MXUS/Lyen mini-Monster combo at approx. the same power levels and while it's sensitive, it's more pleasant in feel. I haVen't touched the shunts and we are talking about a combined 30 Amax.
Perhaps any "harshness" in the controller's operation is acerbated when they are summed. Another area of the combo that left me a little cold was the mid-raNGE performance. Although it would fairly well leap off the line and pull amazing top speeds, there was a pronouned lull in the upper mid-range. Perhaps upping the controllers output would have bolstered the flat mid-range, I already wasn't liking the throttle and I didn't really want to change the rear drive because...
So it was time to step back and think about my original intent and goal, which was to build a really nice pedal assist that also had some back-up and some performance enhancing capability.
The Q100 "fast wind" rear running solo on 12S is just that, a really nice assist set-up in the 18 to 22 mph, dead quiet and smooth as silk. But as a stand alone unit, it is at times, out of it's element starting and climbing in a 24" wheel on a almost 300 lb. gross MTB. For a really fit cyclist of moderate stature, this would be a perfect assist motor. Throw some Volts on it, leave the the controller stock, and he or she could have great satisfaction of pedaling up World Class cycling speeds.
But for me, I don't need the 26 to 28 mph speeds the Siamesed motors provide, so my sense was to combine systems with different parameters.
Revisiting the MXUS up front...
But first, a word about 36V mini's;
If the 36V no-load speed of the "201" slow wind is 230 rpm[and I believe it is] and the 328 fast wind is 270 rpm, the MXUS falls neatly in the middle at 250 rpm. If for no other reason than it's the most equitable compromise, makes it probably the best choice for a single mini motor application, at least for the majority of users.
So what if I put some mid-range back into the equation?
I already knew that running the Q100 sensorless on the KU63 controller is painless, if fact I couldn't discern any difference, with or without Mr. Hall's sensors. How would the MXUS do sensorless on the KU? Well, athe dded motive force of the rear motor helped by getting things rolling, as well as the low power level, but every now and then, it would get out of step and "stub it's toe". So no, no sensorless magic in the KU. Performance wise, not much difference from the dual Q100's the same stock controllers, same 12 mph climbing The Hill and 26 mph top speed. But remember the MXUS is in a 26" wheel opposed to the Q100, which rides in a 24". Perhaps the wheel size trade-offs balance out the "wind" differences or perhaps at these power levels, the differences are too small to quantify. One change imediately noticable, smoother throttle response.
MXUS in 26" wheel/Q100 in 24" rear;

SAM_0678.JPG (69.89 KiB) Viewed 2064 times

To be continued...

[motomech]

Ok, so I have the MXUS/Lyen Mini-monster combo on the frt. and with twice the power available than the Q100/stock controller it replaces, "Pepe" is a whole different beast to ride. There is still some start-up sync'ing issues with running the MXUS without sensors, but usually the impetus from the rear gets thing rolling smoothly. Idealy, there would be a slight delay where the frt. would come on a second later. Still, if I just grab a handful of throttle, the MXUS will spin and in general, just overpowers the q100 rear, That, plus reaching down to flip a switch to activate/deactivate the frt. motor is not very convienent. Once engaged, I'm inclined to just leave it on and that's not how I want to use it, so a throttle set-up rethink was in order.
Since my backround is more mechanical than electrical, I choose to try a simple mechanical solution first. It looks like this;

SAM_0689.JPG (47.96 KiB) Viewed 2036 times

I added the BMS Battery kit's thumb throttle up close to the half twist, retaining the half twist for the rear and using the thumb for the frt.. The motion using both is very natural because it's the same motion;

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The button on the thumb throttle is wired to the E-brake and I try to make a point to deactivate it when not in use. Should the twist/rear be activated accidently, I can pretty much hold the bike in place, but should that happen with the frt., the bike is going to launch somewhere. And dismounting or moving around the bike, it's easy to snag or lean against the thumb throttle. The switch to the right is the cruise, which for some reason, activates immediately. That;'s ok, no waiting and it still deactivates normally.
All in all, I'm very happy with this arrangement, everything is right there and it works well with my intended use of this Ebike. And that is, running the rear only about 90% of the time, using the frt. only for starting up a hill, sprinting across a busy intersection and various types of climbing. For say, a grassy bank, I can "jam" them both and get a good launch and back off the frt. as I approach the crest, the point where the frt. may want to start spinning. On a long climb, especially one with curves or changing road surfaces, this set-up works great. Hit the cruise control almost from the start and let the rear add it's 650 Watts continuously and use the frt. as an "assist for the assist". "Driving" with the frt. motor, so to speak. With the thumb throttle, it's easy to add 50 Watts, 100, 200, whatever on top of the rear's 650 Watts. Also works well on long straights, to maintain my desired low 20's mph cruising/pedaling speed while bucking head winds.
To be continued...

[anarce]

motomech, I enjoy your posts so I opened this thread for the first time. I'm a noob and haven't read much about 2WD bikes yet, but I had a thought (dangerous!) after reading through this. I wonder what would the performance be like if you went back to a 26" tire on the front? How would the power balance be with both motors running at the same time? The rear motor would give you more torque off the line and push you up to speed, and then maybe the front would pull you up to a higher speed and help fight the wind resistance as you go faster. I've seen other bikes on here where people use a smaller tire in back, but I'm curious how that would work with 2WD and how it would affect the efficiency.

[motomech]

motomech, I enjoy your posts so I opened this thread for the first time. I'm a noob and haven't read much about 2WD bikes yet, but I had a thought (dangerous!) after reading through this. I wonder what would the performance be like if you went back to a 26" tire on the front? How would the power balance be with both motors running at the same time? The rear motor would give you more torque off the line and push you up to speed, and then maybe the front would pull you up to a higher speed and help fight the wind resistance as you go faster. I've seen other bikes on here where people use a smaller tire in back, but I'm curious how that would work with 2WD and how it would affect the efficiency.

Yes, If I was doing it over, I probably would have gone with a 26"-frt./24"-rear, although I think the fast wind in the 26" wheel would be too tall, even with some help from the rear.
When I selected the original components, I had 2 things in mind. Using 2 of the same, simplest kits out there. And changing from 26" wheels to 24" wheels.
The wheel change was prompted by the height of the MTB, it's a 20.5 inch frame and with 5" of rear wheel travel, the seat is way up there[I'm 5'11", but with a short 29" inseam]. It also has a very high top rail, so that even off the seat, I can't really flat-foot it. But what I found, to my suprise, is that it's too low with the 24" wheels, I can't pedal though a corner without the pedals hitting the pavement. part of that problem is due to the soft rear suspension. It's an air shock and as they are want to do, it looses a bit of pressure over time and after a week or so it's back down to 95 psi form where I set it at 125 psi. I have this little hand pump, but it's lame. I recently aquired one of these and now it's easy to keep the shock where I want it;

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So to recap, I didn't really like the throttle feel of two identical Q100 kits hooked together by a "one wire" throttle. I don't think I imagined it either as it was the first thing I noticed when I first rode it..
The easiest way I can think of to describe what was going on is to use an analogy comparing an electric motor system to a sound system. We all know the sound reproducing systems do not have a perfectly linear freq. response[not that our ears would like that anyhow]and due to introduced artifacts, there are peaks and valleys and usually,, they are considered distortion. Usually[but not always], the less expensive the system, the more distortion. In this case, one low-powered system doesn't produce anything unfavorable to be noticable, by running the two Q100 systems in sync., the result was to amplify any "distortion" that resulted from the interaction of the motors and controllers.
I don't want to make a big deal out of this. as anything to get the two systems out of lock-step would probably make the issue disappear. It could be running a "fast wind" and a slow wind" motors together would do it, or mixing wheel sizes, or isolating the throttle by using two or simply running one throttle signal though the Cycle Analyst.
But I've moved on and probably won't take the time to re-install the 24" Q100 frt wheel to try out any of these "solutions.
I went back to the MXUS 26" frt. because that is what I had on hand. And while the lowly BMS Battery 15A controller worked fine with the MXUS, I went with the hard-hitting Lyen Mini-Monster because the power is addicting
But in making these changes, I completely changed the goal of this build from trying to make one Ebike "pedal assist" set-up better, to making two Ebikes[maybe even three, depending on how one looks at it].

So this is what I have now;

System #1[rear only]-Docile pedal assist that only "sees" an Amax of 17 Amps and is capable of returning W/hr numbers in the low 20's[looking to improve that as I get in better shape].
or
System #2[combined system #1 and #2] A peppy system that on 14S see peak Amps of 50 and total Wattage peaks close tio 2K/W. With a top speed of over 30 mph, it's getting close to being capable of dealing with traffic, something I rarely do. Having a relatively powerful frt. motor on the frt. for street riding is actually fun once you get accustomed to it. An example; This morning, I had to blend into traffic for a few blocks, so I came around a slow corner doing maybe, 10 mph, and punched both throttles and the frt. tire started spinning for a couple of revolutions, cool. This is heady stuff for a guy who has been using a single mini on 48V/17A for the last couple of yearo
But it comes at a price. Much of this is abusing my small Zippy 15C packs and consumption climbs up into the high 30's W/hr.s.
So like most everyone else here before me, I've ordered more Lipo[Turnigy 20C this time, to be built into larger packs].
Also comes the concern about how long the MXUS would tolerate this behaviour if if became the regular way I ride.
But far and away, the best use is to steel myself with some disclipline, and stay on the rear motor only and only use the frt. when needed. One area, maybe not needed, but enjoyed, is using the frt. to reduce "rowing though the gears". On the rear system alone, I find that I need to use at least 5 or 6 gears to maintain momentum. With a little judicious use of the frt. three gears will do nicely.

So that about sums up where I'm at now with this set-up.
Things that I still need to do include;
Getting that 48T chain ring hanging on the wall mounted.
Consolidating my Lipo all to 12S[I have various sm. packs at 12S, 13S and 14S, I just had to try every possibility out. Should have taken Dogman's advice and started and stayed with 12S ].

[Samd]

+1 subscribed.

I have one of these controllers, 24v 350W - found the info very handy.

[motomech]

Seeing double.

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The weight of the batteries quickly broke a single stand....

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Same single motion with foot lowers and raises the stands.

[Samd]

Hey there,
you mentioned that you are running 14s, but elsewhere people say not to take the KU63 over 50 volts. Am I reading right?

Cheers.

[motomech]

Yeah, I did run 14S for a while, it turned the Cute into a tiger[cub] with a top speed around 26 mph.
It's been really hot here[in the high 90's F] and today during a routine inspection I found this;

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That's the insulation on the kit supplied phase wire connectors that are starting to melt.
I will be replacing the stock connectors with Andersons or 4 mm bullets, but I figure the wires themselves would be right behind in terms of melting.
No more 14S, although I don't know if this happened on 12S, 13S or 14S.
This is with the stock controller that never really pulls more than 15.5 Amps.

Motor never really gets hot, but the controller and wires sure do.
The wires are too small a gauge to get any real power to the Q100 I.M.O.
EDIT-the melted bits was caused by running the fast wind motor at slow speeds, it's this combo. that really heats up the controller.