Heat sinks for hub motors?

[fatty]

Yes: understood: However, you negate something. Look at the average: Speed (25mph load)~ , and : Power ( reflecting the consumption): you will see they are both the similar league but the power average is quite higher with the thermal waste of 100A on tap at all times.. on a 35A hub motor. The system physically limits the power. ON the lower. So less consumption, even though with the ATF you would think the load is a little more from the drag. NO Load RPM went from 1.2A to 2A. Upon using the oil... On cold days it is noticeable, the increase in rolling drag. But... consumption lowered. I could zoom in on the throttle trace and we would see WHEN the CA3 was actually limiting the THout (on the lower ride).

These are identical rides.. ( route). And yes.. the actual discrepancy is noted that one, (( lower log, thermally limited, 100* soft and 150* hard,) and with rollback enacted) is compromised to a degree.... , even though the Aux amp variable is 100% on both logs.. the lower gets hot and limits power.. so no comparison.

Still, same average speed, time, route, distance and very similar peaks.. coincidences aside. Average temp is controlled in one, and not controlled in the other.. and I still got to the store in the same amount of time.

I didn't negate anything; in fact, I only gave a passing glance to the logs. Instead, based solely on the implausible conclusion (700W reduction), I concluded that the data --upon which that conclusion is based-- is therefore not comparable.
I appreciate this may be the best comparison data you have available, but in science, if you receive a prima facie implausible result, you have to explain the mechanism, or face the possibility that your data may not be correct.

We know reducing winding temperature reduces winding resistance, and therefore winding resistance loss.
Let's say the motor phase resistance is 0.2Ω at 20C; temperature coefficient of resistivity for copper is 0.0039/C; we'll use your 35A figure.

resistance final = resistance initial * [1 + temp coefficient(temp final – temp initial)]
resistance HOT = 0.2Ω * [1 + 0.0039/C(105-20)] = 0.2663Ω @ 105C
resistance OIL = 0.2Ω * [1 + 0.0039/C(69-20)] = 0.2382Ω @ 69C
1 - (0.2382Ω / 0.2663Ω) = 10.5% lower resistance -- GREAT!

winding resistance loss = A^2 * motor phase resistance
loss HOT = 35A^2 * 0.2663Ω = 326W
loss OIL = 35A^2 * 0.2382Ω = 292W
326W - 292W = 34W reduction -- still GREAT!
But an order of magnitude off from the 700W claimed reduction.

And since the math is easy at 100A, let's just say you rode around at 100A continuously
loss HOT = 100A^2 * 0.2663Ω = 2663W
loss OIL = 100A^2 * 0.2382Ω = 2382W
2663W - 2382W = 281W reduction -- still far less than half the 700W claimed. But shows how important resistance is at high current.

Also, this doesn't account for the 0.8A = ~60W oil drag

 

[fatty]

nonsense

I don't mind having a technical debate, but I honestly have no idea what you're getting at. Punctuation and staying on-topic would help.

Of course there are disadvantages to your friend's heavy e-motorbike. But that was never the question, and certainly not relevant.
The question was RWD vs 2WD.

In any case, weight transfer is not a "possibility" -- it's physics.
You do not "combat" weight transfer -- you learn why it occurs and what the practical effects are. In which case you'd conclude that 2WD is detrimental to performance.

 

[Chalo]

In any case, weight transfer is not a "possibility" -- it's physics.

It's physics that's applicable to stinking cars as much as it is to bikes. Audi put the issue to rest in the '80s. Tesla continues today. All wheel drive beats rear wheel drive unless the front wheels are in the air.

 

[Ďrãgøn~Fírë]

That's your problem fatty you haven't dont it so you jus dont know....... you jus concluded so basically be 1 theory dictates one outcome you assume it is the correct one without considering all the elements that play a direct role. So you jus assume which in itself is wrong. How about you try it. So take theory make it practical then test it and at that point you are then qualified to make your arguement with science fact not conclusion or assumption.

Look at how that weight has to be transferred. It's at a huge mechanical disadvantage then the average 1000w hubbie is on 30-40 nm and are you insane the heavier you make it the more force is required as the wheel has no leverage yet I do also I'm not a fixed variable I move depending on what I'm doing. And when someone agrees with you for conditions that may better adhere to what you are saying and you snottily and arrogantly tell them the ain't get a clue with shoddy research. When you clearly wont research what you are saying do I add hypocrisy too because that's what I conclude and no you started bigger is better then went with kryptonian law forgoing on any earthly laws of physics that dont adhere to you kryptonian laws of power transfer what do you expect.

And as an open minded technical discussion requires that both people take onboard what the other is saying I conclude fatty your glass is full

Sent from my SM-G950F using Tapatalk

 

[miro13car]

since this thread is about keeping hub motor from overheating ..
in intelligent drive motor must signal to controller that it overheats to protect itself , temp sensor is a must on all my ebikes.
touching, drilling holes in the hub ???

 

[fatty]

It's physics that's applicable to stinking cars as much as it is to bikes. Audi put the issue to rest in the '80s. Tesla continues today. All wheel drive beats rear wheel drive unless the front wheels are in the air.

I figured AWD cars would come up, but hoped it would be obvious as to why cars are a dramatically different implementation:
Cars have proportionally lower CoG and longer wheelbase, reducing longitudinal weight transfer. This should be obvious: whereas it is trivial to achieve 100% rearward weight transfer (and thus wheelie) an e-bike, this does not occur in cars -- they always maintain significant load on the front axle. Even my little racecar, if it did 0-60mph in 5s = 0.55g, would only transfer 290lbf to the rear, leaving the front tires with ~475lbf each. Taken to the extreme, you do see special show drag cars pull wheelies --so it is possible-- but these cars are universally RWD.

And in any case, AWD in cars is still primarily marketed, and indeed the primary actual benefit, to prevent getting stuck in snow and/or ice -- especially where tires have unequal traction.

 

[fatty]

That's your problem fatty you haven't dont it so you jus dont know....... you jus concluded so basically be 1 theory dictates one outcome you assume it is the correct one without considering all the elements that play a direct role. So you jus assume which in itself is wrong. How about you try it. So take theory make it practical then test it and at that point you are then qualified to make your arguement with science fact not conclusion or assumption.

Look at how that weight has to be transferred. It's at a huge mechanical disadvantage then the average 1000w hubbie is on 30-40 nm and are you insane the heavier you make it the more force is required as the wheel has no leverage yet I do also I'm not a fixed variable I move depending on what I'm doing. And when someone agrees with you for conditions that may better adhere to what you are saying and you snottily and arrogantly tell them the ain't get a clue with shoddy research. When you clearly wont research what you are saying do I add hypocrisy too because that's what I conclude and no you started bigger is better then went with kryptonian law forgoing on any earthly laws of physics that dont adhere to you kryptonian laws of power transfer what do you expect.

And as an open minded technical discussion requires that both people take onboard what the other is saying I conclude fatty your glass is full

Sent from my SM-G950F using Tapatalk

I did try it, through modeling & math -- read my posts.

Of what I can decipher, nothing you've posted is technical discussion. Again, punctuation and technical terminology would be helpful. I honestly don't know what you mean in the second paragraph.

I'd really recommend everyone read some of the foundational texts on vehicle dynamics like Gillespie or the Millikens texts. Staniforth is much less technical, but a good introduction.

 

[Chalo]

It's physics that's applicable to stinking cars as much as it is to bikes. Audi put the issue to rest in the '80s. Tesla continues today. All wheel drive beats rear wheel drive unless the front wheels are in the air.

I figured AWD cars would come up, but hoped it would be obvious as to why cars are a dramatically different implementation:
Cars have proportionally lower CoG and longer wheelbase, reducing longitudinal weight transfer.

They also have radically more power and power per gross weight than most of the e-bikes we're familiar with, which negates your argument. Any wheel that's on the ground and bearing some weight can apply power. High power e-bikes might wheelie off the line, but as RPMs increase, they set right back down and the front wheel can go to work.

 

[fatty]

They also have radically more power and power per gross weight than most of the e-bikes we're familiar with, which negates your argument. Any wheel that's on the ground and bearing some weight can apply power. High power e-bikes might wheelie off the line, but as RPMs increase, they set right back down and the front wheel can go to work.

No, power-to-weight doesn't negate the argument, because you're ignoring weight transfer.

If your front wheel sets right back down, then you're not accelerating at the greatest possible rate, and you can use higher volts in the rear to keep accelerating at the limit of control.

This is a waste of time. Read a book on vehicle dynamics so we can have an intelligent debate.

 

[E-HP]

No, power-to-weight doesn't negate the argument, because you're ignoring weight transfer.

If your front wheel sets right back down, then you're not accelerating at the greatest possible rate, and you can use higher volts in the rear to keep accelerating at the limit of control.

This is a waste of time. Read a book on vehicle dynamics so we can have an intelligent debate.

Sorry, I read through the thread but couldn't figure it out; what's your current ebike setup?

 

[litespeed]

So back to the original post......Hubsinks changed my world. I was running 14 KW (MaxE) through a QS205 3.5T motor which was great. Only problem was after a few hard miles I had to lay off because of heat.....then along came Sketch! I added Hubsinks and ferro fluid then I could run hard for 75% of the time......possibly longer but I was wore out before my motor ever got hot! I have a 20s15p 30Q pack.....that’s 45 amp hours so I can literally go for 50 miles driving HARD!

Just try the Hubsinks and ferro fluid......I promise you that you will be pleasantly surprised! Simplest, cheapest no possible leak solution. <mic drop>

Tom

 

[markz]

Whats the diameter and width and name of your tires?
Looks like motorcycle rims and tires to me.

Single speed works well for you?
Do you know the gear sizing front and rear?

With 3.5T QS whats your speed most of the time?

.

 

[DogDipstick]

power-to-weight

This is a waste of time. Read a book on vehicle dynamics so we can have an intelligent debate.

Recommendation? I mean, we aint calculating tire slip angle and cornering traction force, right? Measuring the temp of the tires and rolling them down hills on a timer next, eh? Lol.

Lol. Shizzle, like that, you know.

Fun facts: Ferrari F360 GTC Power-to-weight ratio: 472 hp/tonne (352 kW/tonne). Ferrari always loved that power to weight ration. F360 they began building purpose built for racing, available for purchase. For some reason, but they just srip a car of everything, add belts, extinguisher, and brakes, and call it a "Race car Ferrari" and charge like 200K$ more for the same car.

Another Ferrari fun fact: Originally based on the F430 Challenge, the F430 GT3 is a specialized racing car developed in 2006 by JMB Racing for the FIA GT3 European Championship and other national GT championships such as British GT and FFSA GT. It is mechanically similar to the F430 Challenge but has better-developed aerodynamics and more power.

The car uses the same 4.3 L V8 engine, tuned to produce 550 hp (410 kW; 558 PS), making the GT3 more powerful than its GT2 counterpart. However, due to the GT3 regulations stating that the car must have a power-to-weight ratio of around 2.6 kg/hp, the car weighs 1,219 kg (2,687 lb) in race trim (driver and fuel excluded), which is roughly 119 kg (262 lb) more than the GT2 spec car. Despite the higher power, it is significantly slower than the GT2 version; for example, in the 2007 Spa 24 Hours endurance race, in which both models were entered, the GT3 spec vehicles' best qualification time was around 8 seconds slower per lap than that set by the GT2 spec vehicle.

Ferrari seems to love that powa-to-weight ration. Honestly I think I can see why. I would rather have a 400 hp 2000 lb missile.. than a 3000 lb missle... all day. For my racing purposes. When I plan to go Ferrari racing.

Just like I would rather have a 400 lb (oil cooled) ZX 1000rr vs a 400 lb CB500 with all those (air cooling) fins. I am pretty sure I can make one go very fast around a track, and the other.. well... you know.

Maybe it is not a good comparison.



I do want to say I misspoke earlier..

It is not more 'efficient" power, as proven incorrect in the assertion, by fatty, earlier. The aiding in cooling did not make my consumption that much better. The Wh/mile figure dropped in the second log because of the thermal roll back. .... Not the cooling fins and ect.

......but the cooled hub gives the same or better power.. all around.. I meant to say. I get just as far, just as fast average speed. Even higher peaks, and even better , and do not notice the amperage throttleing by the CA because I still have those big peaks time to time.

 

[litespeed]

Whats the diameter and width and name of your tires?
Looks like motorcycle rims and tires to me.

Single speed works well for you?
Do you know the gear sizing front and rear?

With 3.5T QS whats your speed most of the time?

I have a 3.00 x 17 rear and 2.75x 19 front tires/rims. Shinko 241 tires. Traction is never an issue nor is flats!
Gearing is only good to 22mph at a really fast cadence. 52/16. I wish I could run a cluster or 2 speed front ring but I can not. Not sure of a way to get more gear.

I’m at a point where I don’t want to be noticed.....read->not stand out in the crowd! Most times when visible (semi empty streets/sidewalks) I’m in the 15 to 28 mph range. Ridding with bikers/joggers (public trail systems) then always under 20 mph. When by myself 30 to 65 mph.....catch me if you can!

Tom

 

[fatty]

Recommendation? I mean, we aint calculating tire slip angle and cornering traction force, right? Measuring the temp of the tires and rolling them down hills on a timer next, eh? Lol.

The foundational textbooks are
Fundamentals of Vehicle Dynamics by Gillespie
Race Car Vehicle Dynamics by Milliken & Milliken

Quantitative modeling is taught in
Fundamentals of Vehicle Dynamics and Modelling by Minaker
Road Vehicle Dynamics by Rill & Castro

I have all 4 and am happy to share -- just PM.

I agree that they should not be needed, given the intuitive observational examples I've given in this thread, but a more thorough understanding is always beneficial. And for those that would dismiss physics, perhaps these authorities will be more convincing.

 

[E-HP]

The foundational textbooks are
Fundamentals of Vehicle Dynamics by Gillespie
Race Car Vehicle Dynamics by Milliken & Milliken

Quantitative modeling is taught in
Fundamentals of Vehicle Dynamics and Modelling by Minaker
Road Vehicle Dynamics by Rill & Castro

I have all 4 and am happy to share -- just PM.

I agree that they should not be needed, given the intuitive observational examples I've given in this thread, but a more thorough understanding is always beneficial. And for those that would dismiss physics, perhaps these authorities will be more convincing.

I remember in high school watching my friend's cousin race his Yamaha 650 twin cruiser against a 1000cc sport bike across a long parking lot where my friend worked, maybe 1/8 mile before needing to brake hard. In theory, it should have been no contest. In the end, his cousin won, with half the HP of the other bike. He knew how to launch his bike, and it took off straight like a rocket.

Never forgot that, and won a lot of races because of it. The rider's position on a motorcycle is an active component impacting how it handles and performs. Has to be, the weight ratio is pretty high at 1/2, maybe 1/3, and so is the power to weight. On an ebike. the rider to bike ratio even higher, like 2/1 or more. If I lean forward on my ebike, and hit the throttle on anything but dry pavement, the tire will spin. I can mitigate that just by shifting my weight back a little, and get all the power to the ground, just like on a motorcycle. Sit upright and don't pay attention and maybe do an unintentional back flip. Three results; all about rider position and paying attention.

I think it's probably the same on a 2WD ebike, but imagine it would be even easier to manage that front/rear balance, since the front motor would help keep the back motor planted, when the rider weight is shifted forward. Might have to build one some day.

I don't know. It would be interesting to see how the references you cited analyze drivers shifting their weight around in their cars. I wonder if they cover that. It probably would be oversimplifying to assume rider position is static for motorcycles or bikes though. It's one thing if the driver is 1/20th the weight of the vehicle, and another it he's twice the weight and moves around, too.

 

[MadRhino]

The bike need to be built for the purpose and terrain that it will be riding. There is no general rule that universally applies. Today, I was riding on ice covered with slush and snow, with deep car tracks. How do you think I would have performed with a GP racing motorcycle?

 

[fatty]

I think it's probably the same on a 2WD ebike, but imagine it would be even easier to manage that front/rear balance, since the front motor would help keep the back motor planted

This is circular reasoning though. The front motor can only help keep the back motor planted by further accelerating the bike and transferring weight from front to back, thus unloading the front, which limits how much force that front motor can deliver.
This self-limiting compromise is inherent in all FWD vehicles.

 

[markz]

Even Justin Lemore uses a fwd hub motor.
For those that havent seen the video tour of their older location.
https://youtu.be/IxB2j-egWcQ?t=595
Lots of good info

 

[E-HP]

I think it's probably the same on a 2WD ebike, but imagine it would be even easier to manage that front/rear balance, since the front motor would help keep the back motor planted

This is circular reasoning though. The front motor can only help keep the back motor planted by further accelerating the bike and transferring weight from front to back, thus unloading the front, which limits how much force that front motor can deliver.
This self-limiting compromise is inherent in all FWD vehicles.

I would call it feedback that the rider incorporates to make weight adjustments with. Same principals used for riding any two wheeled vehicle. Kid's learn it intuitively. Bike leans one way, the kid turns his handlebars in that direction to correct, etc. You have to be active when riding on two wheels.

 

[fatty]

Even Justin Lemore uses a fwd hub motor.
For those that havent seen the video tour of their older location.
https://youtu.be/IxB2j-egWcQ?t=595
Lots of good info

But as he continues, it's a 25A, 40kph economy commuter, not a performance bike.

 

[fatty]

I would call is feedback that the rider incorporates to make weight adjustments with. Same principals used for riding any two wheeled vehicle. Kid's learn it intuitively. Bike leans one way, the kid turns his handlebars in that direction to correct, etc. You have to be active when riding on two wheels.

I appreciate the primacy of rider skill and positioning (see A Twist of the Wrist), but acceleration-induced weight transfer is fundamentally distinct from lateral rider movement for handling. Rider position can certainly modulate the rate of weight transfer, even advantageously, as you described, but the hard limits remain.

 

[serious_sam]

acceleration-induced weight transfer

So one thing that you glossed over is grip level. In low traction conditions, load transfer is limited. Even with a high CofG. When load transfer is limited to the point that load is carried by the front tyre, then adding drive to that wheel will increase acceleration.

This is common in slippery conditions (lower mu), and going up hills (lower normal force).

If your front wheel sets right back down, then you're not accelerating at the greatest possible rate, and you can use higher volts in the rear to keep accelerating at the limit of control.

So this blanket statement isn't always the case. It is only valid under specific circumstances.

 

[fatty]

So one thing that you glossed over is grip level. In low traction conditions, load transfer is limited. Even with a high CofG. When load transfer is limited to the point that load is carried by the front tyre, then adding drive to that wheel will increase acceleration.

This is common in slippery conditions (lower mu), and going up hills (lower normal force).

Well, I've acknowledged that previously in another thread. The reason I still don't think that loose surfaces are a slam dunk for 2WD is that the same fundamental rules still apply: by way of static weight distribution, the front wheel already has less weight and thus traction, and any acceleration (from front or rear drive) reduces that even further. And since the front wheel is also tasked with steering, the traction capacity for acceleration is again reduced even further. And your steering wheel is not the one you want spinning...
Not to mention the other compromises induced by FWD like torque steer and compromised suspension performance.

In short, if uniform surface conditions prevent significant acceleration, adding FWD isn't going to help.
The solution, again resolved definitively over the past 100 years, is simply to tire the RWD bike for the conditions: from sand paddles to studded ice tires -- both of which can achieve 100% rearward weight transfer.

 

[fatty]

There is no general rule that universally applies.

So this blanket statement isn't always the case. It is only valid under specific circumstances.

I'm not so sure about this. So far, I've been careful to limit my explanations to upright performance bicycles on surfaces where achieving 100% rearward weight transfer is trivial (140A into a DD45 Std).
But the fundamental limit to acceleration (that is, losing control at 100% rearward weight transfer) applies to all vehicles, from recumbent cycles to drag cars. Granted, it may take absurd power to get there, but it's certainly possible: "short" wheelbase drag cars & bikes have wheelie bars to keep the front end down to preserve steering. (low-traction surfaces addressed in previous post: tire to enable 100% rearward weight transfer)

I think this topic likely deserves its own detailed thread