Running Twin Motors

[safe]

yes i fully agree - the puma will need some thermal managment added to it i believe. Esp if there are lots of these team hybrid kits going around with people trying to wring 2500w out of them all day every day.

Enter MCL into the hub motor world... :wink:

 

[xyster]

Thanks for the pic, BiGH. I'm imagining something like that with pedals, the motors in both wheels, and the batteries all packed midframe.

 

[TylerDurden]

FWIW:

http://www.makezine.com/blog/archive/2007/06/electric_bike_project.html?CMP=OTC-0D6B48984890

 

[Jozzer]

I decided to split my post into two - it was getting too large.

Guys i think i'm going to build a bike with two motors. and i'm going to further complicate matters (esp with oil hitting these stupid levels)...

i've currently got a 408 with the new wizz *no bang* clyte 35a controller.
to this bike i'm going to add a puma front motor running either puma 35a controller or another new cylte one.

another question for the group - would it be possible to wire in a "front or rear bias" trimpot? to say offer different throttle signals to the front and rear motors?

Esp for xyster's dirt bike idea - it would be mad to be able to select 50/50 power distribution or say 25/75 or something



Looks like insted of going for a single X5 with lots of mods (my initial plan) dual pumas will be done

summary dual pumas vs x5:
pros of dual pumas:
freewheels, gearing, = increased efficiency, more reliable

cons:
cost, weight (vs one motor alone)
pros of x5:
INSANE power handling

cons of x5:
less efficient, controllers would require modification = no warranty, motor itsself is rediculously heavy

You WONT get a warrenty for a Puma at 72v either, yet alone at 35A!
I keep saying it, for reliable everyday use not much more than 1500w for a Puma, 2kw at a push and with thermal cutouts, and 2500w if you dont mind buying a new motor every now again!
X5 isn't that heavy for the power it puts out when used to the max...especially since if 2kw isnt enough, then you are talking about replacing a trials bike/crosser, and if you want to put that much power down in such a trying environmnet then perhaps a motorcycle frame/wheels/brakes would be more up to the job. You are also beginning to get into the price range of an Etek (2 Puma's+2 controllers)....you could get some 15HP+ out of an etek, and weight comparison with 2 puma's and 2 35a controllers vs an Etek isn't far off either..

 

[safe]

I'm sure there are cheap Chinese hub motors somewhere that operate at fairly low power ratings. If you could buy two cheap Chinese hub motors and then trick them out with overvolting and MCL you could roughly double the power for the same heating. So in effect whatever rating you start with goes up 4x. (two motors, both producing double power) Using MCL will cut your low end torque, but if you use pedals that would be the preferred time to pedal anyway. (on a hill you just have to help out a little) So I see this as something that is very possible to do and it really comes down to locating the product at the right weight and price. I'd say that a 250 watt - 500 watt hub motor should be able to be found in the 5-8 lb range (I know that 7.7 lbs exists) and then if the price can be in the $75 each range then you have the makings of a deal. If the price starts getting into the $200 range per motor then you might as well stay with a chain and use the higher quality stuff like the PMG 132 or Etek.

 

[Xase]

2 wheel drive motorcycles have been around for around 50 years now. check out http://www.Rokon.com. I had one for a while. will go right up a tree. I even found a guy that converted one to electric . The originals ran a 6 hp 2 stroke motor and toped out around 25 mph. These are for the true back woods guys that want to drive where a person can't even walk.

Here's a pic for u xyster - inspiration for ur future bike!:

http://www.eatmydirt.com.au/articles/416

Where do you keep finding these awesome pics?
I googled around for this dirt bike and found a cool French video of it racing a WRX. Too bad they weren't on dirt!
http://calientestolanu.wordpress.com/2007/09/13/yamaha-wr450f-vs-subaru-impreza-wrx-grn/

 

[BiGH]

thanks

i did a google search for "yamaha 2wd bike" cause i remember there being talk a log time ago about 2wd bikes - and checked out the 3rd link -and yeah there u go.

TD - awesome find they look like 4 series motors! thats basically what i was thinking of minus the thunderbirds look. edit: also found this on the site: http://www.makezine.com/blog/archive/2005/11/how_to_bicycle_frame_protectio.html


SAFE - interesting point regarding the etek etc. (fearing the storm ahead) i'd prefer to say away from chain drive at the moment, its awesome and clearly more efficient, however I believe its best for dedicated project bikes like yours. I'm after at least a semi stealth bike!


what about 2x 408 motors vs a 5304? that would also be an interesting match. for comparison purposes.

according to ebikes.ca:
408 weighs 6.9 kg (2@13.8) $270.00 + $295 =$560
5304 weighs 10.95kg $470 for a rear wheel

i don't think the 408s would be a match for the 5304 but would certainly be interesting to try hehe - also had an evil thought - what about two 5302s - that would be a great high speed death machine

 

[xyster]

what about 2x 408 motors vs a 5304? that would also be an interesting match. for comparison purposes.

according to ebikes.ca:
408 weighs 6.9 kg (2@13.Cool $270.00 + $295 =$560
5304 weighs 10.95kg $470 for a rear wheel

i don't think the 408s would be a match for the 5304 but would certainly be interesting to try hehe - also had an evil thought - what about two 5302s - that would be a great high speed death machine

FWIW, the hubmotor simulator shows two 408's in 24" wheels, each at 80v35A, generate almost exactly the same thrust, and have about the same top speed, as a single 5304 in a 20" wheel at 80V70A.

 

[BiGH]

hmmm very interesting!!! Thanks Xy.

lkooks like this might be a good way for people who are not willing to crack open the controller to get good performance from their machines.

if only the 4 series wasn't as heavy as it is :s wonder what the new 408 v2 is like

two cannons would also be interesting, again not sure on weight or power handling.

 

[Anonymous]

Hello All

I have final got some time off now V2 design is complete. So I thought I would catch up on the latest goss.

I hope you do not mind me including my 20cents worth.

Parelling motors and generators has been around for years. The major problem generally is mis-match in specs causing "hunting".

So rather than try and have the two motors operate in unison load why not consider the following. After my comments I will offer some possible ways to achieve.

I propose you run one motor as the "base motor". This motor is used to get to a certain point, at which time it is operating at base load, which would also be the most efficient point for the motor to operate.

At this time the second motor is brought on line. It will run up to match speed and start providing assistance by adding 'top up' power/torque.

As already pointed out, two motors will not dramically increase speed, just power and torque. So great for higher head wind, over coming air resistance to increase speed and better hill climbing.

I feel this may be a better approach as the mis-match in specs becomes unimportant (conceivable to use different power rated motors) and allows the base motor to operate at most efficient point over a greater range of operation.


How to do this. We are all aware of current limiters in one form or another. So a current limiter "output signal' is monitored to trigger the control of the second motor. At this point the base motors speed control is switched to a fix value resitance to correpsond to base load. The throttle then takes control of the now online second motor.

The ideal solution is purpose designed electronics, not overly complex but beyond most here I would think. So a way to "try" this might be to use a basic 4 led voltage monitor, as this would offer some relationship to current. Tap off at the appropriate LED and power a small relay via it. the relay will serve to keep power off second motor until needed. At this time it will switch over and do a number of 'tasks'. First switch base motor to base load, then provide power to second controller and finally switch throttle control to second motor.

Further enhancements would be to swap which motor is the base motor.

I may be over simplifying the solution but I jsut hoped to add some food for thought.

 

[Johnbear]

I have had 2 dual motor bikes. They are very powerful. The top speed did not increase, however they have controllers that govern the top speed to comply with the 32km per hr Canadian law. I am reconstructing one bike with a larger wheel, 24- to 26 and I should get a bit more speed. The controllers are 20amps * 2 - 40 amp draw maximum. Overall it was a very efficient machine. - very heavy. I have run out of juice - like peddaling a tank.

 

[BiGH]

I have had 2 dual motor bikes. They are very powerful. The top speed did not increase, however they have controllers that govern the top speed to comply with the 32km per hr Canadian law. I am reconstructing one bike with a larger wheel, 24- to 26 and I should get a bit more speed. The controllers are 20amps * 2 - 40 amp draw maximum. Overall it was a very efficient machine. - very heavy. I have run out of juice - like peddaling a tank.

yes top speed didn't increase but it sounds like your controllers were the limiting factor there.


My understanding of it is this:
the maximum speed the bike (with two motors) can go is determined by either the controller (if speed limited) - or the no load speed. if one motor got you to 100% of the maximum speed no load then there is no point adding a 2nd to increase speed cause ur already operating to the limit. if your limits are higher and you can't easily reach them - then thats when the extra power from a 2nd motor will help - resulting in reaching higher % of the max no load speed.

eg:

if my 408@48v has a no load speed of 40kph and my speed on the flat (loaded) is 30kph. The most gain adding a 2nd motor can give is 10kph.

however if i have a 406@72v and the no load speed is 70kph and loaded flat speed is 50kph, then there is scope to increase another 20kph.


then the things that limit the amount of an increase in speed also start to factor in - max current draw of batteries/controller, wind resistance, rolling resistance etc, which will limit how close to the no load speed you get to.

Hi Woody,
You make a very interesting point actually - i think however that flexability in the motors is what is really needed. something like a semi-independant throttle. so:

you can select to use one motor (front or rear) or both using a gradient of % of either - say 20% front 80% rear etc etc.... or 0% front 100% rear. that way if u were going at speed, and wanted to increase your speed you could slowly lower the dampening factor of the wheel that isn't powered fully. What could also be intersting is a combination of hub motor and elation!heck if you were crazy enough u could have 3 motors

 

[BiGH]

FWIW, the hubmotor simulator shows two 408's in 24" wheels, each at 80v35A, generate almost exactly the same thrust, and have about the same top speed, as a single 5304 in a 20" wheel at 80V70A.

How did you have 2 408s? i couldn't get it to work the right values out. This could then therefore be an option to have normal sized 26" wheels yes? how would two 408s in 26" rims compare to a 5304 in a 24" same total power?

 

[Anonymous]

Why stop at 3. Two hubs and cascaded elations lol

Why do people get V8 and not straight 4. They both have top end speed above legal. the reason is abilty to approach that speed quicker, or to maintain a higher speed against nature's resistance.

Same for turbo and super charging. If was just about speed then would not need them

BiGh, think outside the circle. What you are suggesting is not unachievable. think RC toys. They have trimpot to balance left/right, etc.

All that is wanted is achievable with electronics. Once I have eLation running well mechanically (which I belivee V2 will), I hope to focus on what I used to do for a living. I am actually Electronics engineer, not mechanical as some people think

So once I get back to it, I hope to design or enhance ebike control system concepts and operations.

All this is good food for thought.

Cheers

 

[BiGH]

BiGh, think outside the circle. What you are suggesting is not unachievable. think RC toys. They have trimpot to balance left/right, etc.

All that is wanted is achievable with electronics. Once I have eLation running well mechanically (which I belivee V2 will), I hope to focus on what I used to do for a living. I am actually Electronics engineer, not mechanical as some people think

i'm trying i'm trying
mind is elsewhere too studying hard to get out of uni -master of laws and bachelor of science- last semester in both.

i'm just kinda happy working within the box on this your electronics sound cool though, and very much looking forward to the new elation v2 (esp if it fits flatbar road bikes)

 

[Jozzer]

I have had 2 dual motor bikes. They are very powerful. The top speed did not increase, however they have controllers that govern the top speed to comply with the 32km per hr Canadian law. I am reconstructing one bike with a larger wheel, 24- to 26 and I should get a bit more speed. The controllers are 20amps * 2 - 40 amp draw maximum. Overall it was a very efficient machine. - very heavy. I have run out of juice - like peddaling a tank.

yes top speed didn't increase but it sounds like your controllers were the limiting factor there.


My understanding of it is this:
the maximum speed the bike (with two motors) can go is determined by either the controller (if speed limited) - or the no load speed. if one motor got you to 100% of the maximum speed no load then there is no point adding a 2nd to increase speed cause ur already operating to the limit. if your limits are higher and you can't easily reach them - then thats when the extra power from a 2nd motor will help - resulting in reaching higher % of the max no load speed.

eg:

if my 408@48v has a no load speed of 40kph and my speed on the flat (loaded) is 30kph. The most gain adding a 2nd motor can give is 10kph.

however if i have a 406@72v and the no load speed is 70kph and loaded flat speed is 50kph, then there is scope to increase another 20kph.


then the things that limit the amount of an increase in speed also start to factor in - max current draw of batteries/controller, wind resistance, rolling resistance etc, which will limit how close to the no load speed you get to.

Hi Woody,
You make a very interesting point actually - i think however that flexability in the motors is what is really needed. something like a semi-independant throttle. so:

you can select to use one motor (front or rear) or both using a gradient of % of either - say 20% front 80% rear etc etc.... or 0% front 100% rear. that way if u were going at speed, and wanted to increase your speed you could slowly lower the dampening factor of the wheel that isn't powered fully. What could also be intersting is a combination of hub motor and elation!heck if you were crazy enough u could have 3 motors

You wont get that close to no load speed, since the closer you get the less current the motor can draw, and at the speeds your talking, you need alot of current. It would certainly help, but no load speed would be unnatainable (without a 80kph tailwind) IMHO

 

[Freddyflatfoot]

Did we get an answer on the lightest 250 watt hub motor?
I have seen one at about 2.3 kg's, marketed in the UK as the Nano.
Maybe several others around, like the motor used on the Ezee Torq, and the Protanium system as used on the new Schwinns.
I'm also looking for a lightweight motor, so if we can find a good one, then we can share where can get a motor supplied?
Thanks
Rob

 

[safe]

Did we get an answer on the lightest 250 watt hub motor?
I have seen one at about 2.3 kg's, marketed in the UK as the Nano.
Maybe several others around, like the motor used on the Ezee Torq, and the Protanium system as used on the new Schwinns.
I'm also looking for a lightweight motor, so if we can find a good one, then we can share where can get a motor supplied?
Thanks
Rob

Well the Nano passes my test as far as weight. (2.3 kg 5 lbs) I'm wondering what difficulties would crop up trying to overvolt a geared hub motor like that. It seems a contradiction to have a brushless but then geared hub motor... the brushless angle increases the efficiency, but the geared part might improve the torque, but reduce the efficiency. Hmmmm....

The Nano is the one on the left... (hard to find a good picture of it)

 

[xyster]

FWIW, the hubmotor simulator shows two 408's in 24" wheels, each at 80v35A, generate almost exactly the same thrust, and have about the same top speed, as a single 5304 in a 20" wheel at 80V70A.

How did you have 2 408s? i couldn't get it to work the right values out. This could then therefore be an option to have normal sized 26" wheels yes? how would two 408s in 26" rims compare to a 5304 in a 24" same total power?

Use the custom input fields and then double the thrust results for two motors in your head, and double the amps for one motor in the sim. Go try it. Hit the "enter custom values" link, and change the torque button from N-M (newton-meters of torque) to Lbs (pounds of thrust). Thrust depends on wheel size, torque doesn't, so thrust is the better measure when one is comparing different wheel sizes. I've found that real-life top speed (for the 5304 anyway) is right about where peak power is. I don't know if this holds true for the other motors too.

 

[Xase]

Parelling motors and generators has been around for years. The major problem generally is mis-match in specs causing "hunting".

So rather than try and have the two motors operate in unison load why not consider the following. After my comments I will offer some possible ways to achieve.

I propose you run one motor as the "base motor". This motor is used to get to a certain point, at which time it is operating at base load, which would also be the most efficient point for the motor to operate.

At this time the second motor is brought on line. It will run up to match speed and start providing assistance by adding 'top up' power/torque.

As already pointed out, two motors will not dramically increase speed, just power and torque. So great for higher head wind, over coming air resistance to increase speed and better hill climbing.

I feel this may be a better approach as the mis-match in specs becomes unimportant (conceivable to use different power rated motors) and allows the base motor to operate at most efficient point over a greater range of operation.


How to do this. We are all aware of current limiters in one form or another. So a current limiter "output signal' is monitored to trigger the control of the second motor. At this point the base motors speed control is switched to a fix value resitance to correpsond to base load. The throttle then takes control of the now online second motor.

The ideal solution is purpose designed electronics, not overly complex but beyond most here I would think. So a way to "try" this might be to use a basic 4 led voltage monitor, as this would offer some relationship to current. Tap off at the appropriate LED and power a small relay via it. the relay will serve to keep power off second motor until needed. At this time it will switch over and do a number of 'tasks'. First switch base motor to base load, then provide power to second controller and finally switch throttle control to second motor.

Ahhhh..... I see. Kind of like a senquential twin-turbocharger setup, right?
http://en.wikipedia.org/wiki/Twin-turbo#Sequential_Twin-Turbo

 

[Xase]

Did we get an answer on the lightest 250 watt hub motor?
I have seen one at about 2.3 kg's, marketed in the UK as the Nano.
Maybe several others around, like the motor used on the Ezee Torq, and the Protanium system as used on the new Schwinns.
I'm also looking for a lightweight motor, so if we can find a good one, then we can share where can get a motor supplied?
Thanks
Rob

Yeah, when I saw safe's posts the first thing that came to my mind was the new Schwinns as well:
"the electric drivetrain weighs in at about 10 lbs"
"Schwinn Protanium Mini Motor with alloy shell, 24v, 180 watts continuous; 250 watts max"
http://www.schwinnbike.com/products/bikes_detail.php?id=889

 

[GGoodrum]

Fascinating stuff, really.

I've wondered about how a two-motor setup would be controlled, and have the load truely shared. It seems that one would always be working a bit harder than the other, unless they are perfectly in-sync.

I have a slightly different dual-motor application in mind. I want to bolt two 20" bikes together, into a quad, and run two 5303s. I think this presents a slightly different problem, because the if one hub motor is going a little faster with the same throttle setting, it will want to drive in a circle if corrective steering is not applied. I can see this could be corrected with calibration trim pots, but would this work with the Hall Effect throttles?

-- Gary

 

[safe]

I've wondered about how a two-motor setup would be controlled, and have the load truely shared. It seems that one would always be working a bit harder than the other, unless they are perfectly in-sync.

A motor that works harder gets hotter.

A hotter motor runs less efficiently so it produces less power.

Seems to me that like global warming and ice ages these things have feedback loops that tend to stabilize things over time. One motor runs stronger for a while and gets hotter (carrying more load) then it falls back down and the other motor rises to take the load and on and on...

 

[Rassy]

GGoodrum, I don't think you would notice a side pull. I made my first two wheel, two motor trailer last year for a cheap mb. I had seen adds for comercial two wheel power trailers that just had one wheel drive. I connected both battery packs in parallel so both controllers would be sucking from the same voltage at all times. One controller might have been better, but I wanted the full 35 amps available to each motor for hill climbing purposes. Anyway, it worked great, tracked straight, and, except for the power, couldn't even tell the trailer was there.

 

[Geebee]

GGoodrum, I agree with Rassy about the offset drive having no effect.
My delta trike has independent rear brakes and I can brake on one wheel without any pull to that side.
Several trike manufacturers build trikes with single side drive and the only time it affects steering is when the road is steep enough to unload the front wheel allowing it to slide sideways under power, thes tend to be trikes with extreme rear weight bias.