Running Twin Motors

Ok time for a bit of a discussion.

would running two motors give a higher top speed than running one motor (assuming you aren't reaching the no load speed of the motors?)

I'm just wondering if these assumptions are correct or not:

running two (for argument's sake) pumas would:
1. increase speed
2. increase acceleration
3. be more reliable than running double the power through one motor

There would obviously be a slight hit in performance being the extra weight of the 2nd motor.

my theory would also mean the following:
that two pumas with two 72v 35a controllers would provide as much speed as one puma at 72v 35a?

Discuss.

BiGH said:

Ok time for a bit of a discussion.

would running two motors give a higher top speed than running one motor (assuming you aren't reaching the no load speed of the motors?)

I'm just wondering if these assumptions are correct or not:

running two (for argument's sake) pumas would:
1. increase speed
2. increase acceleration
3. be more reliable than running double the power through one motor

Click to expand...

1. Assuming both are using the same voltage, top speed will remain the same.
2. Yes, two will be like having one with double the torque, except it won't rip out the front/back of the bike.
3. Yes, but your batteries will still be the single point of failure. It would make for a good backup though. Your motors would live longer.

There would obviously be a slight hit in performance being the extra weight of the 2nd motor.

my theory would also mean the following:
that two pumas with two 72v 35a controllers would provide as much speed as one puma at 72v 35a?

Discuss.

Click to expand...

Great or insane minds think alike. My next project plan after my electric ATV is a two wheel drive 406 bicycle, but I'm going to turn it into a motorcycle. The 406 on my current e-bike can spin the wheel over 65 MPH @ 72 volts, so if it had the torque (or steep enough hill) I could go anywhere a car could go provided I stay off the Highway/Interstate where the speed limit is 70 MPH and above.

It's going to be two 72 volt 20/35 amp controllers with one throttle feeding both. 406 in the front will be the 20 amp controller, the 406 in the back will be using the 35 amp controller. That project will be a lithium battery pack hopefully some 20AH 37 volt packs with the 40 amp max current. I'm going to put the two in parallel to make a 40AH pack @ 72 volts. Of course disc brakes all around, 700C wheels, double wall rims 10ga spokes, etc.

So it will be like having a motorcycle with a some big motor running 55 amps @ 72 volts (3960 or more watts). It will have to be "DOT" registrable so it's going to have the windshield, blinkers, brake lights, headlights, etc.

Yes, very expensive, it's going to be like buying a motorcycle. Except this one is going to be under 100 lbs and hopefully fast enough to keep at 55 mph speed limit with burst good enough to merge and dart across traffic. I know safe has gone into detail about the best way to design a motorcycle and he has the experience with it to know, but mine is going to be a close copy of my current one. Maybe it's just me, but going 40 to 50 mph on my e-bike is really no sweat for me as far as handling, braking, etc. I've never had an event happen that had me worried, anything behind a crash involving a car pulling out in front of me, but none on the tech side of will my motor or wheel fail while riding.

Hi,

I agree with knightmb on question 2 and 3 but I think there will be a minor increase in speed as the combined motors will reduce the load allowing a greater speed. Probably not much, 3 to 5 mph, maybe ?????

I can't see that there would be much inprovement in overall performace on road, but off road this sounds like a lot of fun

Ian

I agree with Ian that you'll enjoy a slightly higher top speed by using two hubmotors, just like when also pedaling any single-gear ebike system (if the rider can peddle fast enough that is).

Two Puma's with dual 72v35a controllers is my dream dirt bike system too. For tackling really steep dirt trails as I plan too, 72v35a total power is not enough, IMO. For riding at up to 35mph on fairly level pavement, it's plenty.

Hey guys,

Xy, i think dual pumas at 72x35 would be more than enough power - indeed im only going to be using 1 motor at that power and i think it will be plenty - when you are offroad there is no hitting 35mph anyway - 25 is probably the best speed i will achieve on the terrain i ride and the power is just to help uphill.
when i do finally get my hands on a puma controller i'll video what you can do with one motor at that power - indeed i was really impressed at just 36v with the pumas ability to climb, i could get up hills and banks i couldn't do with pedal pwer alone previously!!

Cheers


D

deecanio said:

Hey guys,

Xy, i think dual pumas at 72x35 would be more than enough power - indeed im only going to be using 1 motor at that power and i think it will be plenty - when you are offroad there is no hitting 35mph anyway - 25 is probably the best speed i will achieve on the terrain i ride and the power is just to help uphill.

D

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Well, apparently we need 4000 watts at the wheel to go 27mph up a 25% paved grade, which means ~5000 watts into the wheel. Considering the dirt, and the extra power needed for acceleration, I don't think 5000 watts is at all excessive -- hopefully it's enough to assure a sprightly ride to 20mph up a 25% unpaved grade.
http://www.kreuzotter.de/english/espeed.htm
The Puma sounds like a great motor, but its performance is not going to magically exceed the laws of physics.

I live at the foot of the Cascade mountain range, not far from Mt. St. Helens and 11,000-foot Mt. Hood. Not that I'm planning to climb Mt. Hood with my bike anytime soon, but there's plenty of steep hills I do plan to, and I'd like to design my system to climb a mountain just for a point of design reference, and to keep the possibility open.

Apparently, the highest mountains you got on your tiny island are 3000 feet, and I'd assume less steep.
http://en.wikipedia.org/wiki/Mountains_of_the_United_Kingdom
http://www.walkingenglishman.com/mountains.html

Fully loading a Puma at 72v 35A offroad up steep trials will likely overheat a Puma I fear (assuming constant use of 2.5KW).

yes xy, my tiny island cannot compare i'm afraid - it certainly would be amazing to see a bike with dual puma's and how it performs.
like jozzer sais though the puma cannot take the power an x5 can so when you say 5000w do you mean split 2500 per wheel?
its a very interesting idea, i'd like someone to try it

cheers

D

deecanio said:

yes xy, my tiny island cannot compare i'm afraid - it certainly would be amazing to see a bike with dual puma's and how it performs.
like jozzer sais though the puma cannot take the power an x5 can so when you say 5000w do you mean split 2500 per wheel?
its a very interesting idea, i'd like someone to try it

cheers

D

Click to expand...

Yes, split in half so that each gets 2500W -- which I understand from Knoxie and Jozz is still going to waste lots of heat energy, and possibly kill the motor. In this regard, I might be better off just feeding 5000W to a single rear-wheel X5. But for a dirt bike, I love the idea of all-wheel drive.

ChopperMan said:

Hi,

I agree with knightmb on question 2 and 3 but I think there will be a minor increase in speed as the combined motors will reduce the load allowing a greater speed. Probably not much, 3 to 5 mph, maybe ?????

I can't see that there would be much inprovement in overall performace on road, but off road this sounds like a lot of fun

Ian

Click to expand...

I realize now I should rephrased my response, I'm reading my original response and it came out wrong, *smacks forehead*

Having two motors will raise the top speed of the bike, but it won't double or triple it in anyway. If the motor can take you up to 35 mph on level ground and you put another motor on (assuming the batteries can take the load), your top speed should increase, but not beyond the rotation speed of either motor since they don't add, they "blend" their speed together. So twice the power and given air resistance and such, your top speed will increase to the point that both motors hit the torque wall against air resistance.

If my 406 @ 72 volts with a 20 amp controller can achieve 45 mph on level ground, then two motors, say running another 20 amp controller, would probably achieve the 50 mph + speed with ease. To me, logically it seems that having another motor would be like taking the original motor and just doubling up on the current, but I think it's a little more complex than that. Having two motors would help for efficiency in the system. Instead of one motor having a ton of amps being forced down it (and probably producing a lot of heat), you have two motors working together, within their own restraints they would be more efficient than the single trying to do it all.

An excellent point. Sharing the current, two motors should be more efficient than one of either. However, it gets more complicated when the dual motors are different than the single motor. At a given current and speed, is two Pumas less efficient, more efficient, or the same as a single X5?

Practically speaking, would my dream dirt bike be more efficient with a single X5 running 5000 watts, or dual pumas each running 2500 watts?

xyster said:

Practically speaking, would my dream dirt bike be more efficient with a single X5 running 5000 watts, or dual pumas each running 2500 watts?

Click to expand...

Methinks dual motors... twice the heat dissipation.

xyster said:

Practically speaking, would my dream dirt bike be more efficient with a single X5 running 5000 watts, or dual pumas each running 2500 watts?

Click to expand...

I would put my bets on the latter, sure the X5 can handle the power, but since the dirt bike is likely going to be pulling some amps to go up steep inclines and just all out fun it may shorten it's life if heat becomes a problem.

I think the bottom line would be, is the X5 more efficient at 5K than a Puma at 2.5K? Also, in the sense that it's a dirt bike, two wheel drive would be very unique. How many front/back drive dirt bikes do you see? I've never seen any, it's usually back only.

knightmb said:

Having two motors would help for efficiency in the system. Instead of one motor having a ton of amps being forced down it (and probably producing a lot of heat), you have two motors working together, within their own restraints they would be more efficient than the single trying to do it all.

Click to expand...

Agreed.

TylerDurden said:

xyster said:

Practically speaking, would my dream dirt bike be more efficient with a single X5 running 5000 watts, or dual pumas each running 2500 watts?

Click to expand...

Methinks dual motors... twice the heat dissipation.

Click to expand...

But the X5 must be close to twice the diameter of the Puma, and at 25lbs versus 16lbs for the dual-Puma, the X5 has more thermal mass to buffer the heat too. We know Lowell runs his at 6000 watts for short sprints with no overheating, whereas Knoxie and Jozz report the Puma starts overheating at 2500 watts. But we don't have quantitative info about how long either can run near peak power.

So how about it? Can any Puma user tell us for how long the Puma can run a sustained 2500 watts without overheating? And maybe Lowell can let us know for how long the X5 can handle 5000W without overheating? Let's define "overheating" as 'too hot to hold a hand on indefinitely'.

Just so my question doesn't get lost...

What's the lightest weight 250 watt hub motor?

knightmb said:

ChopperMan said:

Hi,

I agree with knightmb on question 2 and 3 but I think there will be a minor increase in speed as the combined motors will reduce the load allowing a greater speed. Probably not much, 3 to 5 mph, maybe ?????

I can't see that there would be much inprovement in overall performace on road, but off road this sounds like a lot of fun

Ian

Click to expand...

I realize now I should rephrased my response, I'm reading my original response and it came out wrong, *smacks forehead*

Having two motors will raise the top speed of the bike, but it won't double or triple it in anyway. If the motor can take you up to 35 mph on level ground and you put another motor on (assuming the batteries can take the load), your top speed should increase, but not beyond the rotation speed of either motor since they don't add, they "blend" their speed together. So twice the power and given air resistance and such, your top speed will increase to the point that both motors hit the torque wall against air resistance.

If my 406 @ 72 volts with a 20 amp controller can achieve 45 mph on level ground, then two motors, say running another 20 amp controller, would probably achieve the 50 mph + speed with ease. To me, logically it seems that having another motor would be like taking the original motor and just doubling up on the current, but I think it's a little more complex than that. Having two motors would help for efficiency in the system. Instead of one motor having a ton of amps being forced down it (and probably producing a lot of heat), you have two motors working together, within their own restraints they would be more efficient than the single trying to do it all.

Click to expand...

Yes sorry i didn't phrase my question perfectly.... what i mean is this: (which you hvae answered above).

Assuming that your NO LOAD speed is say 80kph on the motor (it won't spin faster than this)

and you LOADED speed on the flat is say 55kph at 72v35a then it should give you a similar speed as though u were running 72v70a. (note i didn't increase the volts - as this governs TOP NO LOAD speed).

therefore guestimating: two pumas at 72v35a would be more efficient than one puma at 72v70a (assuming it was possible) which should overcome some / all of the weight increase of a 2nd motor.

But as fletcher said you're still governed by the no load speed of the motor.

xyster said:

An excellent point. Sharing the current, two motors should be more efficient than one of either. However, it gets more complicated when the dual motors are different than the single motor. At a given current and speed, is two Pumas less efficient, more efficient, or the same as a single X5?

Practically speaking, would my dream dirt bike be more efficient with a single X5 running 5000 watts, or dual pumas each running 2500 watts?

Click to expand...

not sure - it'd be very interesting to find out actually!

i'm looking at this very seriously. Puma has 2 features in it that really will help in real world scenarios:

1. - gearing -
2. - freewheel. i found that when i was going downhill on the 408 i would still apply power up to the no load speed in order to avoid "magnetic braking" due to the motor inducting current into the wires. You loose quite a bit of speed down hills. I found my bike would hold a about 35kph and not go faster, where as other bikes ive had (non electric) would accelerate due to gravity pulling down the hill.. Crystalyte owners check out knoxie's latest video of the puma - how long the freewheel spins the wheel - wish my 408 did that :S


here's some "haydon" logic for you all:

if you were going to run one large motor with a lot of current - you're likely going to have to run a 2s2p pack (assuming each pack is 36v11ah or something) to provide the necessary power density to reduce the C rate you're draining the pack.

So this isn't going to be any different to running two motors - with 2s1p on each. = no extra battery cost

and does offer *some* redundancy -you could run one motor, or select only good packs of batts

the extra cost comes in the new motor - but then you get less wear and tear on the motor.

Safe- i'd love to tell u what the lightest motor is - i can only guess tho - i'm guessing the nanomotor is right up there, but still i'd prefer the puma -much more speed potential.

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.

safe said:

I might yet join the "hub motor" crowd... :wink: (at least on one bike)

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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

xyster said:

But the X5 must be close to twice the diameter of the Puma, and at 25lbs versus 16lbs for the dual-Puma, the X5 has more thermal mass to buffer the heat too. We know Lowell runs his at 6000 watts for short sprints with no overheating, whereas Knoxie and Jozz report the Puma starts overheating at 2500 watts. But we don't have quantitative info about how long either can run near peak power.

So how about it? Can any Puma user tell us for how long the Puma can run a sustained 2500 watts without overheating? And maybe Lowell can let us know for how long the X5 can handle 5000W without overheating? Let's define "overheating" as 'too hot to hold a hand on indefinitely'.

Click to expand...

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.

BiGH said:

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?

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Yeah, I don't see why you couldn't. Your goal being to balance out two different type of motors. It's easy when you have two clones, but your setup you'll certainly want balance or else one motor will be doing all the work while the other slacks around playing with the EMF monster.

tchapin said:

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.

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exactly seems an easy thing to do.

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


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