Help picking a motor

[tonystark20]

So, since I've gotten into ebikes many years back I've had 5 different ebikes, 1 being a cheap scooter and the rest being custom recumbents.

I currently have a custom bike built (build thread: https://endless-sphere.com/forums/viewtopic.php?f=6&t=97601)
I recently managed to shear the axle on my qs 205. The bike has had other issues and things I'd like to change so I plan on building another frame, but this time I'm going to do it from complete scratch and use aluminum and build a full canopy for all weather driving.

I'm having trouble deciding what motor I should use.

top speed 40km/h minimum
voltage: I have two custom 74v 25ah sanyo 18650 GA battery packs (x2)
controller: ASI 4000 (I have the software so I can program it for any motor)
target weight: less than 75kg
efficiency: 20wh/km or less
trike will have full suspension
note: I'm 6'3" and weight 250kg

Stats from previous builds:
current trike ~105kg, 30wh/km qs205 ~12.365KV with 74v 50ah Liion ASI4000,
kmx trike - Golden Motor Pie 5, 44v 10ah 12s lipo, total weight ~45kg 26" rim = 12wh/km, 45km/h, not enough torque for hills
Unbranded steel frame - Golden MotorPie 5, 48v LiFePO4 30ah, total weight 60kg, 25wh/km, 45km/h, not enough torque for hills
Found this trike on youtube many years back it's what has initial fueled my idea (https://youtu.be/9na1kFdU9gs
Youtube velo: Crystalyte 3548, 60v, 20AH LiFePO4, 40A infineon controller (states ~200km range with pedaling) speed = 60-65km

my goal is to find a motor and rim size that can provide good acceleration and torque for hills but the efficiency for long trips. I have a J1772 connector that I use for long trips and my goal is to a long distance camping trip at some point but I need a range of 150km minimum, my goal would be to hit 20wh/km and then add a trailer for flexible solar panels.

A few motor I'm looking at are:
Another qs205 but with a slower KV wind (5t = 9.03kv or 4t+ = 10.63kv)
DD45_STD from grin with statorade added (8.8kv)
M3540R from grin with statorade added (9.5kv)
MTC3080R_TA from grin with statorade added (9.9kv)

for the motor I'd likely use a 20 or 24" wheel with 2 ply moped tire, for the qs I'd likely stick with the 17" motorcycle tire and the Shinko SR241 Dual Sport Tire I have on the current qs205.

Thoughts on motor options would be greatly appreciated, I'd even consider a mid drive, but I'd have to assemble a drive train for that as I use both forward and reverse on my trike (and would use it even more so if it had a full canopy as you wouldn't be able to flintstones it)

 

[dogman dan]

Re efficiency, no reason a fast, powerful motor cannot be efficient. Its not romping the throttle with lots of power on tap that does it. When you come to that mountain, climb it fast, and the motor runs efficient. It will take a lot of watt hours, if your bike is big, heavy, and not very aero. But keep up the rpm so you climb it at 15 mph, and you will climb it as efficient as you can. Climb it at 30 mph, then you pay for the poor aero. ( if that's the case)

But back in the valley, relatively flat, efficiency is not your motor, or your voltage, its purely your speed. At 15-18 mph, you can pedal up significant amounts of the total you are using, say 400w, and you pedal up 100 of it. The huge high powered motor is not going to eat more power,, only more speed will do that, less pedaling will do that, and more aero resistance will do that.

So its not your motor choice, if it has the power to get you up the hills when you need it. ( no pies) Its just your speed that makes it poor wh/mi. If you must use a small, low power motor on a big trike or cargo bike, then you must make it a mid drive, with low gears.

RE the winding. I have been a big supporter of the low speed wind DD motors. At first I was confused about how they work, and I no longer recommend them for 72v. I DO recommend them for 48v bikes that are built to go slow, and always go slow. The result is you can climb hills even slower, without overheat or inefficient rpm running up the hill. Still have to climb those hills at 12 mph or more though, the motors are not that slow.

You should not need any statorade, for the long trip. The key is going slow enough to get good wh/mi with your huge rig, and then having plenty of power to not run too low rpm up the mountains.

My target on long trips was 25 wh/mi. To hit that, I rode 15 mph as much as possible, on a cargo bike with horrible aero. I had enormous panniers on it, and weighed over 400 pounds with me on it. I carried 2000 wh of battery.. Real world wh, so with some of my batteries old, I carried about 30 ah of 48v. With that, I could do 70 miles, which out here in the desert, is the typical distance to the next place you find water and a plug. I HAD to make the range, or pedal in the last 20 miles on a 400 pound bike. They cycleanalyst was the key, It would show me a running average of my wh/mi. So if a mountain made me take 40 wh/mi, I would see if it returned to 25 on the downhill run. If not, I'd slow down even more. No water out there.

 

[tonystark20]

you can pedal up significant amounts

Awe... I'm trying to avoid pedalling... In all seriousness the new bike I'm planning to build will have a proper gear set so that I actually could pedal.

speed that makes it poor wh/mi

had a feeling my speed would be the big thing, according to my cycle analyst most of the time my average speed is 28km/h which was reading out the 30wh/km. the odd thing is is the lightweight trike I did with the pie was getting great wh/km and the average speed for that bike was was about 35km/h most of the time.

I do realize going slower would increase the range the only down side and reason I don't like going that slow is because the trike is 4ft wide... and the main trip I want to take is 4000km one way and at least one spot has 150km of no plugs. and most of the route is the trans canada highway... I'd like to not be going turtle pace if I can avoid it.

I have been a big supporter of the low speed wind DD motors. At first I was confused about how they work, and I no longer recommend them for 72v. I DO recommend them for 48v bikes that are built to go slow, and always go slow.

well that's a shame, but good to know. I used to run 48v but then I got the qs205 and switched to 72v, and I really don't want to swap all my gear for 48v. (the controller i have is 72, i have a 72v 10a 110v charger and 72v 25 amp 220v charger. plus all the wiring and contactors)

You should not need any statorade, for the long trip. The key is going slow enough to get good wh/mi with your huge rig, and then having plenty of power to not run too low rpm up the mountains.

I mainly wanted to add statorade because I truly enjoy having fun at times, plus there are some rather large hills near me where I could see it being handy. most of the time I'd maintain my 30 - 35 km/h speed on hills. the qs 205 was really nice for that, kinda surprised me at first to be able to accelerate going up hill.

Right now I'm leaning towards another qs 205 with a slower wind (as I don't feel the need to go 60km/h and the extra torque on the super large hills near me could be useful) I think combined with a lower vehicle weight and the canopy I want to build and swapping the tires for better rolling resistance should give me the performance I want.

Thanks for your candor.

 

[goatman]

youre 6ft3 and weigh 250kg. that's 550lbs and then you have the bike and trailers?

 

[tonystark20]

youre 6ft3 and weigh 250kg. that's 550lbs and then you have the bike and trailers?

Thanks for posting that, don't know where I came up with 250kg as my weight.
my actual weight is 120kg (which is about 264lbs which for the longest time is was 250lbs, so I clearly mixed up measurements)

I'm actually currently trying exercise more to slim down a bit, as I have a bit of a beer gut (it's a family trait unfortunately)

but anyways sorry about that as I realize that it would have a huge effect on motor performance having that much weight.

 

[goatman]

well your tall, the trike is going to be 4 feet wide and you snapped an axle on your last trike so I thought 550? maybe hes a sumo wrestler :wink:

 

[tonystark20]

well your tall, the trike is going to be 4 feet wide and you snapped an axle on your last trike so I thought 550? maybe hes a sumo wrestler

well that's a nice way of looking at it. Unfortunately the snapped axle was my fault - didn't have my dropouts tightened correctly after having done work on the trike.

sadly not the first time I've switched my measurements. I do work on so many things so I switch between measurements all the time. eg home construction I learned feet / inch growing up. then 3d printing in mm, and decimal inch in the machine shop (lathe and milling) and then there's automotive where manufactures can't make up their mind of what socket size to us eon a car - even worse if a car uses metric and fractional.

either way life goes on. thanks for the laugh though.

 

[amberwolf]

I used to run 48v but then I got the qs205 and switched to 72v, and I really don't want to swap all my gear for 48v. (the controller i have is 72, i have a 72v 10a 110v charger and 72v 25 amp 220v charger. plus all the wiring and contactors)

If you have a motor you wish to run at 48v (one that is wound for the speed you want at 48v), but a 72v setup, then assuming the controller is not a torque-throttle (current-throttle) simply limit your throttle voltage such that it only goes to 48 / 72 = 67% of full output. So you will get the same results as you would have if you were running a completely 48v system.

This can be done with a simple voltage divider on the throttle signal output, or set in the ThO section of the Cycle Analyst if you're using one.

And you can add a bypass button (or preset in the CA) that allows full throttle if you think you will ever need that full power and speed out of the motor, momentarily now and then.



If it's a current-throttle (torque throttle) then this isn't necessary, as you have better control of the power; you're not controlling the voltage that goes to the mtoor anyway--yo'ure controlling the current to it. So there's no need to limit the throttle voltage. You simply apply the amount of current needed for whatever speed you're going under the conditions then present.

You can add a speed limit if you like, assuming your controller has that, or you're using the Cycle Analyst.

 

[tonystark20]

If it's a current-throttle (torque throttle) then this isn't necessary,

That's indeed what I'm running, I have the ASI-4000 at my disposal, and I do have the programming software for it too.

I am using the cycle analyst v3 as well, and would like to get a thun sensor at some point.

The other thing I plan to do is use an arduino to have an extra bypass / control of throttle. the arduino would be interfaced with the cycle analyst serial port to get the current battery data, and through some sort of user interface, I want to add cruise control, that can maintain a set speed at a push of a button, as well as add a range mode, where I can tell it the distance I want, and in return it would have a light on the bike that would change color if I'm meeting the wh/km to reach my target or possibly override my input.

thanks for the information amberwolf

 

[amberwolf]

the arduino would be interfaced with the cycle analyst serial port to get the current battery data,

Remember that the CA doesn't "communicate" with devices like that, it just sends a continous stream of data at the rate you set in it, of (I think) the parameters you've chosen.

So the arduino will have to take that stream, and parse it for the correct fields, then keep storing that data and updating the variables it is acting on with that stored data, continously. (rather than just querying the CA for it when it needs it).


Regarding the THUN sensor--it only senses one side. (the left, IIRC), so if it's important that it continously sense torque, instead of only for half the pedal cycle, you'll want a Sempu, TDCM, or one of the other types.

And just because it has come up before with other posters being confused about this, the torque sensing BB does not have anything to do with torque throttle control.

 

[tonystark20]

Remember that the CA doesn't "communicate" with devices like that, it just sends a continuous stream of data at the rate you set in it, of (I think) the parameters you've chosen.

So the arduino will have to take that stream, and parse it for the correct fields, then keep storing that data and updating the variables it is acting on with that stored data, continuously. (rather than just querying the CA for it when it needs it).

I'm aware of this condition, I've run a test already just to see if I could see the incoming data, which I could. I haven't attempted the parsing yet, but as far as I know it's possible.

Regarding the THUN sensor--it only senses one side. (the left, IIRC), so if it's important that it continuously sense torque, instead of only for half the pedal cycle, you'll want a Sempu, TDCM, or one of the other types.

thanks for reiterating that, thankfully I'm aware of the left foot limitation of the THUN, should. Thun was the name in my head when I was typing but I'm aware of the other / better options available from ebikes.ca.

All great information for me to keep in mind, my priority will be to get some tools and then I'll be making a new build thread for this awesome machine to be. (big ticket item is an AC TIG welder for aluminum)

 

[dogman dan]

Re the slow motor, you can go ahead and run it at 72v. I just meant that at 72v, it will NOT have more torque, or more power than the faster wind running the same throttle setting. It will be slower top speed, and less total wattage. What happens is the motor reaches that point where it won't draw full load wattage, at a slower speed than the faster motor. So it starts backing off the power sooner, unless you overloaded enough to make it pull till it dies. But this effect, does lead to using a bit less power, extending range, but at slower speeds. It works, but to get real efficiency, you are slowing down, and running at speeds you only need 48v for. If all your shit is 72v, that's fine. you will just end up running at less throttle a lot, to get to that speed where you don't throw way your watt hours to wind drag.

But its advantage will be a couple mph slower rpm possible, without going into inefficient rpm, and overheating mode. Nothing wrong with statorade, I just meant that if you load it reasonably, you can climb the rocky mountains without overheating. The key thing here is just maintaining your speed up that mountain will enable the motor to run at its more efficient rpm and make climbing that mountain ok without needing statorade. But put some in if you want to cool the motor off quicker once you do top out. Or just do the holes, either one will greatly reduce your cool down time.

Re the riding slow. Its the only way to get over those long jumps between plugs. But with your CA guiding you, easy to ride fast as you like when you will get to a plug soon enough. I just wanted to emphasize that you can get 15 or 25 or whatever wh/mi with ANY size motor once on the flat, or 5% grade rolling hills. Its just a question of going slow enough that your pedaling does provide significant amounts of your total. At some point, range is infinite, if you go slow enough. But then of course, you are just pedaling a heavy bike. This is why my target was 25 wh/mi. Easy pedaling, but not pedaling around toting battery for no reason.

 

[tonystark20]

So, my current thought is that I'm going to buy the qs205 again with the 17" rim, I'm going to very likely have statoraide added and will buy the hub sinks at some point.

What I'm wondering is what winding to get.

I want preferable a 40-50km/h top speed.
the last motor was just above 4t (RPM 915) (60km/h without flux weakening - ASI4000, running 40amps)

the two options I'm looking at are
30*4T 72V 820RPM
24*5T 72V 650RPM