Heat sinks for hub motors?

[fatty]

Bigger isnt always better my friend with 5k 3.5t qs motor with a 3k controller and some 60+ah battery pack ( there were some 350 cells used to make his pack I really haven't done it justice) and he could never understand how my cheap ass 2x 1000w hubmotors 1800w controllers and a cheap ass pair of 60v 12ah batteries could keep up

2WD can only provide benefit when the tires are on unequal traction surfaces, such that the tire on the loose surface loses traction and begins to spin, while the other tire on the solid surface maintains traction. It should be trivial to understand this fundamental concept: any acceleration must cause a load transfer to the rear, thereby unloading the front. If the front is still has sufficient traction to generate additional acceleration, that acceleration will further unload the front.

Bigger rear is always better.

 

[fatty]

Thanks for all the input guys! I would rather hot rod a small motor to have the lighter weight. My motor is not overheating so there’s no reason to buy a bigger motor. I started this topic not because I have heat issues, I was simply looking for suggestions whether these heat sinks are efficient. Maybe I mentioned above I’m new to building E bikes so all this is new to me. I will go with the Statorade Ferrofluid and the heat sinks. Also I’ve ordered a 72V battery and I want to be prepared for any extra heat.
Thanks for all the suggestion E-bikers!

Small motor for lighter weight + heat transfer fluid + hubsink = heavy motor with terrible aero = profit?

If your motor is not overheating and there's no reason to buy a bigger motor, then there's also no reason to hubsink the small motor.

 

[Ďrãgøn~Fírë]

I wouldn't like to fix a leaky roof with that argument fatty. Though there is some merit to what you say it's far too exaggerated. Once both wheels gain traction they work brilliantly together (besides which better weight distribution better results) giving huge acceleration to the point where cars have to scream past full power roaring engine p!ssed driver wondering why hes doing 50mph in a 30 zone breaking the law to overtake a bicycle. Oh and the beach is great fun along with the muddy fields and largely hilly areas with steep slopes to climb but then what would I know I only ride my bike and obviously have no actual clue how it works. Oh and upto near 40mp it severely outperforms my petrol motorcycle but again what do I know

 

[fatty]

It's not saving a few lbs... It is doubling the power to weight ratio or greater.

No, a better estimate is 34% increase in continuous current, not counting additional drag friction.

 

[fatty]

It's not saving a few lbs... It is doubling the power to weight ratio or greater.

Of the motor, maybe. What's the percentage difference in system weight including the rest of the bike and you?

You're not even thinking in the right direction on this. If the power-to-weight ratio of the motor itself increases, then the increase in power-to-weight ratio of the system must be even greater, since the increase in motor weight becomes a much smaller fraction of the overall system weight:

Weight for the heat transfer fluid: 650mL for a 9C. At 0.85g/mL, that's 550g into a 6.3kg motor, for 6.9kg total:
(1800W/6.9kg) / (1200W/6.3kg) = 37% increase in power-to-weight ratio

On a 100kg bike+rider:
(1800W/100.6kg) / (1200W/100kg) = 49% increase in power-to-weight ratio


With 10 years and 8000 posts, you have a responsibility to at least try.

 

[fatty]

I know I only ride my bike and obviously have no actual clue how it works.

Obviously.


Look, I'm not saying your bike doesn't work. And there can be reasons to add FWD -- like you already have the parts.
But grade-school Newtonian mechanics shows why there is no advantage to adding FWD. Everybody building an ebike should be able to realize this, at least on a conceptual level.

 

[Ďrãgøn~Fírë]

Ok I'm not great with words and like I said what you said does have merit when I go wot from low speed there is a slight but brief rise on the front wheel but that's it. I'd love to say I go wot n wheelie down the road but that jus simply doesn't happen. Admittedly on take of the front wheel for a second spins b4 it gains traction an looks great for a moment then I have to hold on tight as I fly off down the road but theory and practice are 2 completely different things I can say this is I have 4 hubmotors 3 x 1000w and a rear 1500w and have tried both single rear and front. 1 hub on 48v is quit slow picking up its speed but holds it well once it's there 1 hub at 60v is almost like acceleration with 2 at 48v and 2 on 60v is something else again eventually I'll probably end up on 72v but my aim is to hit 50mph on 60v 1st.

Maybe you should try for yourself and see what it is that others mean my mate swore blind you could never get more power from soldering shunts he jus couldn't see it. It's only there to measure current he would say and after giving up on trying to explain that yes they measure current and the soldering trick that measurement.! but after I bought 2 identical controllers from ebay 36/48v 1 was 35a(I gave him that1) the other was 45a and the only difference in the 2 was the blob of solder on the shunts he open his mind.

Look realistically a battered and deep fried Mars bar should not be edible but hey who am I to argue with a nation. My mind is open to what you are saying but the reality is it works very well and I'm not the only one who would tell you this do your own experiments and see for yourself and make your own informed decision

It might be once I have a suitable frame and completed all my modifications that more of what you are saying comes thru in practice I should certainly expect to see more front wheel lifting results as I head into 72v or higher

 

[fatty]

...when I go wot from low speed there is a slight but brief rise on the front wheel but that's it... Admittedly on take of the front wheel for a second spins b4 it gains traction...

If the front wheel spins, then it is not contributing to acceleration.

I can say this is I have 4 hubmotors 3 x 1000w and a rear 1500w and have tried both single rear and front. 1 hub on 48v is quit slow picking up its speed but holds it well once it's there 1 hub at 60v is almost like acceleration with 2 at 48v and 2 on 60v is something else again eventually I'll probably end up on 72v but my aim is to hit 50mph on 60v 1st.

...but after I bought 2 identical controllers from ebay 36/48v 1 was 35a(I gave him that1) the other was 45a and the only difference in the 2 was the blob of solder on the shunts he open his mind.

You are seeing a benefit because your rear motor is underpowered. Which again, is not to say that your setup doesn't work, but rather a higher-power rear motor would accelerate faster for the same system weight.

Acceleration is fundamentally limited once weight transfer = 100% to the rear, when the front lifts into a wheelie. Any greater acceleration and the bike just flips over backwards. Bikes might flip around 100lbf or ~150Nm. With a ~1Nm/A motor, you need ~150 phase amps.

It might be once I have a suitable frame and completed all my modifications that more of what you are saying comes thru in practice I should certainly expect to see more front wheel lifting results as I head into 72v or higher

You should study more -- this is a very basic error.
More volts won't lift the front wheel. More volts only keeps the front wheel lifted faster while you've got the phase amps to lift it in the first place.

 

[fatty]

So either all the engineers in the world are doing it wrong, or you're doing it wrong, or you have an edge case that nobody else has bothered to design for. Personally, I doubt it's option one.

They certainly do. Lol.

i did consult with my engineer. You edgy one you. We see em all the time in our industry.. of engineering.

You, however, could just google to see that.

https://www.google.com/search?safe=off&client=firefox-b-1-d&sxsrf=ALeKk01YLk_JcbMPi555SfwuL_Hl4YUJBw%3A1611510431155&ei=n7INYPmLCbGWwbkP7OSe8Aw&q=oil+cooled+electric+motor&oq=oil+cooled+motor&gs_lcp=CgZwc3ktYWIQARgAMgQIABBHMgQIABBHMgQIABBHMgQIABBHMgQIABBHMgQIABBHMgQIABBHMgQIABBHUABYAGDJYWgAcAJ4AIABAIgBAJIBAJgBAKoBB2d3cy13aXrIAQjAAQE&sclient=psy-ab

Chalo, you are wrong. And or probably not an engineer.

Personally... I doubt it is not both.

Also, don't mind Chalo, the resident troll.

 

[DogDipstick]

Also, don't mind the resident troll, Chalo.

Troll with datalogs, fvcker.

Here is a datalog of a hub motor that is not cooled. Overvolted and with some very powerful batts. 100a limit, 72v battery. This hub fried in 700 miles and was refitted with new hall sensors. Thermal rolback was enacted, and the hub a was then filled with ATF and equipped with sinks. Then performance datalogged again. Over a thousand times. Oh yeah, did not leak, literally, a drop, Chalo.



This is the result of the thermal management. better power, more even averages, in temperature. Same hub. Same load. Only thing is different is the hub has 250mL of ATF in it, and equipped with sinks. Same very powerful, long lasting cheap battery. ( NOT leaking, Chalo.... ) .



More power, reliability, and performance. Better power from a 17 lb hub,, that, the 3Kw model comes in at 29 lbs for. Almost 2x the weight. Here is an early log with no limiting: You can see the (red) heat line trace creeps up slowly on the top log:... Until it gets into the danger zone and never really goes back down.

This (these) ride(s) looked like a fun one. Human power and Human tq. is also recorded. Along w everything else.

This hub consumed 20Wh/mile less upon cooling and thermal rollback. All that power and amps do make heat. Wasted heat. Energy you see come from the batt,but doesnt make you go any faster or accelerate harder. ZJust wasted away in heat.

Went from 70-80Wh/mile to about 40-50Wh/mile in the summer. Better or same power output, but more efficiency. YOu can see the PID loop trying to control the extremes of temperature at the lower log.

Does a decent job. I have the 29 lb motor 3Kw rated to datalog next in line. In hand.

For a few thousand mile since. I have run this light hub at 4x-8x its original OEM label rating. 80% of that is cause the oil and the thermal properties I know well. I did monitor shell temps, too, at the same time.

I got a few thousand of similar logs showing performance.

 

[Chalo]

It's not saving a few lbs... It is doubling the power to weight ratio or greater.

Of the motor, maybe. What's the percentage difference in system weight including the rest of the bike and you?

You're not even thinking in the right direction on this. If the power-to-weight ratio of the motor itself increases, then the increase in power-to-weight ratio of the system must be even greater, since the increase in motor weight becomes a much smaller fraction of the overall system weight:

Weight for the heat transfer fluid: 650mL for a 9C. At 0.85g/mL, that's 550g into a 6.3kg motor, for 6.9kg total:
(1800W/6.9kg) / (1200W/6.3kg) = 37% increase in power-to-weight ratio

On a 100kg bike+rider:
(1800W/100.6kg) / (1200W/100kg) = 49% increase in power-to-weight ratio

I'm not talking about a hot motor versus the same motor hot and oily. I'm talking about a hot oily motor versus one that's bigger and running in a more efficient range so it can make the same power as the oily one, but without nonsense.

 

[Ďrãgøn~Fírë]

Ok fatty here from where I'm standing you degree in kryptonian law came off the back of a Kellogg corn flake box you so conveniently ommit anything that does not add to your arguement so you can have both barrels.... ok so 1st apply the law of gravity 2nd apply the laws of friction 3rd apply the law of tension. 4th apply the laws of equal and opposite reactions 5th apply ridder position do I need to carry on do you need to go back to school and take your degree again. Since you threw all the basics and every other part of the equation out the window. Here now I take your play book and close my mind to what you are saying.

Wow you are arrogant

Ok so you dont know what I've researched why I researched it or whom I have spoken to in that research or the questions that were asked so seem we are back in school basic current is it.

Electricity explained ohms restrict the flow of electricity and and volts push amps

Ok so 72v Carrie's it's own current value which is around 5000watts though we try to manipulate this as much as we can to out advantage

Wait for get your calculator out so now what are the amps and watts of a 72v controller shall we say mid range 2000w and 40amp so that's 84v x40a = 3360 (oh no what happened to 2000watts) and that's 84volts because that's what a 20s charges too! now that's not even taking into account of max phase amps which can be as high as 2 or 3 times battery current so if we take my battery pack and dont worry fatty I will be gently! And times its max current which is 67v × 60a × 2 = 8040watts wow that cant be right surely not unless I guess the controller limits at said ampage so for my 1800w controllers 67v x 28a x 2 = 3752 or would you prefer to work it all out at nominal voltage because you like to omit everythings that doesn't suit you.....

Pull your head of the ground. And here science in a nutshell you take a theory then you study it then you do practical experiments to determine weather your theory is correct then you apply that to the real world .....so real simple like..... theory -practical- real life meaning actual world and all the laws of physics maths and everything else in between.

Now get off your backside stop theorizing do actual experiments learn about the real world and the forces that ride in it. talk to part manufacturers and do the right research please and come back with fact. Not jus well you cant do that because kryptonian law says so go back to basics.


But then what do I know I'm completely un educated I cant work a calculator or understand v x a =

 

[Eastwood]

Small motor for lighter weight + heat transfer fluid + hubsink = heavy motor with terrible aero = profit?

If your motor is not overheating and there's no reason to buy a bigger motor, then there's also no reason to hubsink the small motor.

Terrible aerodynamics lol Yeah technical the aero would be decreased but in real world application that equals to nothing!

Also I’m adding the higher power battery so if the motor is already running on the hot side I will have overheating issues. So it’s super necessary for me to buy the heat sinks Unless I want to spend hundreds of dollars more buying a new motor which it sounds like you think is the only option.

 

[Chalo]

Terrible aerodynamics lol Yeah technical the aero would be decreased but in real world application that equals to nothing!

Above 20 mph, aero drag consumes a majority of motor power, and above 30 it's almost the only factor that matters. I don't know if this is relevant to your application, because I don't know how fast you go. Above 30 mph, the extra drag caused by pedaling exceeds the amount of power most riders generate by pedaling.

Also I’m adding the higher power battery so if the motor is already running on the hot side I will have overheating issues.

More battery energy will not make your controller deliver any more instantaneous power/heat to the motor than it already does. Metering/limiting power is the controller's job.

 

[Eastwood]

Also I’m adding the higher power battery so if the motor is already running on the hot side I will have overheating issues.

More battery energy will not make your controller deliver any more instantaneous power/heat to the motor than it already does. Metering/limiting power is the controller's job.

There’s nothing aerodynamic about riding a bicycle. Especially riding a downhill mountain bike with my body position straight up in the air as a windshield. Heat sinks will make no difference in my application as far as reducing the aerodynamics.

Also I didn’t suggest more battery power would allow my controller to deliver more. Having a higher voltage battery will spin the wheel faster so therefore I will have more heat. I’ve recently upgraded my controller to a Sabvoton controller and I would like to run at 72v now coming from 48. so yes I will have more power with the bigger battery because I have the controller to deliver it :wink:
Also will be running more current to the motor with my new larger BMS

 

[fatty]

Wait for get your calculator out so now what are the amps and watts of a 72v controller shall we say mid range 2000w and 40amp so that's 84v x40a = 3360 (oh no what happened to 2000watts) and that's 84volts because that's what a 20s charges too! now that's not even taking into account of max phase amps which can be as high as 2 or 3 times battery current so if we take my battery pack and dont worry fatty I will be gently! And times its max current which is 67v × 60a × 2 = 8040watts wow that cant be right surely not unless I guess the controller limits at said ampage so for my 1800w controllers 67v x 28a x 2 = 3752 or would you prefer to work it all out at nominal voltage because you like to omit everythings that doesn't suit you.....

But then what do I know I'm completely un educated I cant work a calculator or understand v x a =

None of this addresses weight transfer, most of it is incomprehensible nonsense, and there are too many errors to correct (except the conclusion) -- but you're still completely missing the point. I wasn't criticizing you or your ride. People here build all kinds of crazy contraptions.

But that doesn't change two-wheeled vehicle dynamics: adding FWD to RWD does not improve performance; it adds weight that would be better added to the rear where it actually would improve performance. There may be other rationales for 2WD, like redundancy, but performance isn't one of them.

You clearly didn't think through my post on weight transfer, but I'm not sure why you have an aversion to doing so. You say you currently have enough phase amps in the rear to unload the front and it spins for a second -- does a freely-spinning wheel contribute force for acceleration? Of course not. Now imagine that you put those phase amps into the rear instead of freely spinning the unloaded front -- what would happen? The front would get a little higher for a little longer, right?

 

[fatty]

This hub consumed 20Wh/mile less upon cooling and thermal rollback. All that power and amps do make heat. Wasted heat. Energy you see come from the batt,but doesnt make you go any faster or accelerate harder. ZJust wasted away in heat.

Went from 70-80Wh/mile to about 40-50Wh/mile in the summer. Better or same power output, but more efficiency.

Good post with data. However, there is simply no mechanism for the conclusion that heat transfer fluid improved ride efficiency by 40%. That's not even plausible.
Indeed, these two logs are not comparable: the latter, oil-cooled log is run at 40% lower power. Of course the resulting Wh/mi is lower.

Heat transfer fluid only allows higher temperature-limited continuous power, or longer temperature-limited peak power.

 

[fatty]

There’s nothing aerodynamic about riding a bicycle. Especially riding a downhill mountain bike with my body position straight up in the air as a windshield. Heat sinks will make no difference in my application as far as reducing the aerodynamics.

...Which is why adding rotating paddles is a terrible idea. You are that incorrect they will make no difference. Try heat transfer fluid first, like low-viscosity silicone oil.

Also I didn’t suggest more battery power would allow my controller to deliver more. Having a higher voltage battery will spin the wheel faster so therefore I will have more heat. I’ve recently upgraded my controller to a Sabvoton controller and I would like to run at 72v now coming from 48. so yes I will have more power with the bigger battery because I have the controller to deliver it :wink:
Also will be running more current to the motor with my new larger BMS

Don't mind the troll, though it may be helpful to very clearly talk him and future readers through your understanding. Higher voltage, even on the same controller, will indeed spin the motor and thus wheel faster. Simply spinning a motor faster doesn't generate more heat, correct? After all, unloaded motors draw hardly any power. But the power needed to overcome aero drag, which increases with the cube of speed, does generate more heat -- exponentially more heat. Again, this is why adding rotating paddles is a terrible idea.

 

[Eastwood]

the power needed to overcome aero drag, which increases with the cube of speed, does generate more heat -- exponentially more heat. Again, this is why adding rotating paddles is a terrible idea.

Every person I’ve spoke with and every video I’ve seen has been positive feedback on the heat reduction. So suggesting it will be a terrible idea will be interesting to see what happens once I install them. I’ll keep everyone posted once I install them :thumb:

 

[DogDipstick]

Just wasted away in heat.

Went from to about in the

Better or same power output, but more efficiency.

Good post with data. However, there is simply no mechanism for the conclusion that heat transfer fluid improved ride efficiency by 40%. That's not even plausible.
Indeed, these two logs are not comparable: the latter, oil-cooled log is run at 40% lower power. Of course the resulting Wh/mi is lower.

Heat transfer fluid only allows higher temperature-limited continuous power, or longer temperature-limited peak power.

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.

For the record:

Upper log (Bare hub)
AVERAGE: 105*C
PEAK:197*C

Lower log (cooled with ATF, and power limited, by CA3.14 thermal PID loop, so yes, not strictly comparable....)
AVERAGE:69*C
PEAK:113*C

Average speed: 25MPH

 

[amberwolf]

the power needed to overcome aero drag, which increases with the cube of speed, does generate more heat -- exponentially more heat. Again, this is why adding rotating paddles is a terrible idea.

Every person I’ve spoke with and every video I’ve seen has been positive feedback on the heat reduction. So suggesting it will be a terrible idea will be interesting to see what happens once I install them. I’ll keep everyone posted once I install them :thumb:

Fatty may be misunderstanding the aero issue--the hubsinks will have nearly zero aero impact vs the total aero impact that the entire bike and rider do.

You could probably stick actual paddles (like for a rowboat) in the spokes of your wheels, so they stick out like something from Ben Hur, and still have less impact than rider position does. :lol:

However, as has been noted by Fatty and others...if you don't use something to fill the air gap between stator and rotor, all the hubsinks will only really cool the rotor and magnets. They won't do much for the part that's generating the heat--the stator itself, which is not connected thermally to the outside world except thru the tiny axle.

Ferrofluid is a minimal-drag (inside the motor, not aero) way of "fixing" the airgap problem between stator and rotor, to help heat out of the stator. Other fluids (see the threads "oil cooling a hub, not snake oil" and "definitive testing on heating and cooling of hubmotors" among others) help to varying degrees, but may require enough more fluid to do the transfer that they add much more drag to the motor (taking more power to spin it, and making it harder to just pedal it without power).

 

[Ďrãgøn~Fírë]

No I'm not opposed to the possibility of weight transfer I took to start an open mind to what you were saying and gave some merit and agreed a little then you made it perfectly clear that you have a closed mind and every 1 but are wrong.

Why bigger isnt always better

My friend has a stealth bomber frame with 5kw 3.5t qs rear hub a 16s 20p+ plus battery lovely forks with a thru axle wheel and a 3kw controller - which neither of us can pick up off the floor and struggle to lift together and we cant pass over gates and fences mine I can and have to regularly pick it up and carry it Upstairs. he still has to pedal on a steep slopes to maintain performance though a bigger controller would solve that where as I only need to lean forward I don't pedal anywhere.

To quote north Wales police, we view what you are riding as a crosser motor bike and if we se you riding it like that again we will confiscate it.

Ha he cant go anywhere in public faster than 14mph where as I go 30mph more if the roads speed limit alows. I have raced a police Van uphill and have overtaken police cars around town when I am stopped it's only because they want to know about the bike as their curious. 4 of us pulled up on llandudno promenade and while 3 of us on bicycles raced around in wot pulling skids an having a riot the one on the stealth bomber got dogged at 5mph by the police and had no fun with the lads.

It's easy to sit there and preach and tell people you are wrong because your theory says so. Did you know if I lean forward n put a little extra weight on the front the wheel does not spin freely (that is rider position) or when I throttle normally the front wheel does not spin freely (that's just obvious)but that's no fun. So basically you would characterise a whole bike ride on 1 second of showing off go the girls and onlookers! AND I NOTED HOW KEENLY YOU IGNORED BASIC PHYSICS.

So how would you combat weight TRANSFER?

Well to start with you can make the front heavier! Oh yes like you said I already have then theres weight distribution I.E. putting the batteries in the middle.

Then we could look at the physics side of things.
To begin with it's at a mechanical disadvantage. Then let's look at the motion of the wheel and how rotation on that surface creates friction.(also here we could cover the engineering of tarmac and tyres there function and rolls they play) which would play a negating role. as the front wheel is pulling and the frame is a bar you have tension this tension would also play a negating role.

Then theres gravity and wait why am I arguing with you you obviously have this argument a lot I might have an open mind to what you are saying but how can I ignore science fact I'm doing the experiments not you!

If there was no performance benefit I would have no choice to go out and buy bigger but I'm not the one who had to spend big to keep up his battery cost him more to make than all the parts on my bike put together so why should I buy bigger instead of improving further what I already have!.

As for the calculations i always do 2 sums nominal voltage and actual voltage surely you must know the difference. While we are on the topic do you know why the industry uses the nominal math on all its spec? Urm gee regulations makes things look smaller yes but if u did factual calculations on most of the regulation kit it wouldn't be legal! Did you know that it's the industry standard to regulate 1000w hubmotor to 750w and they do this with the length and thickness of the phase cables and they do this for the American market.
If you dont believe me about voltage having it's own current value you are very welcome to go bigcurrent bms and argue with them!

You need to open your mind if you wont have an open mind at least have the decency to find out first hand get of ya backside and get science fact on your side.

I am often wrong about a lot of things and when I am I hold my hands up and admit it. I would rather have mutual open minded discussion than argue. But I wouldn't dare tell a person they are wrong if I haven't found out first hand first and dont have all the facts as it tends to make you look stupid a lot more stupid than if you hold ya hand up and say you have a good point.

I am opposed to being told I'm wrong by someone who wont find out for themselves. Look jus find out for yourself do the experiments if it pleases you you can always rig the results with a small front and big back.

 

[fatty]

Every person I’ve spoke with and every video I’ve seen has been positive feedback on the heat reduction. So suggesting it will be a terrible idea will be interesting to see what happens once I install them. I’ll keep everyone posted once I install them :thumb:

Oh, they certainly reduce the motor case temperature quite effectively -- they're spinning aluminum heatsinks.

That's just probably the least desirable method of improving thermally-limited performance.

 

[fatty]

Fatty may be misunderstanding the aero issue--the hubsinks will have nearly zero aero impact vs the total aero impact that the entire bike and rider do.

You could probably stick actual paddles (like for a rowboat) in the spokes of your wheels, so they stick out like something from Ben Hur, and still have less impact than rider position does. :lol:

Oh, upright bicycles are certainly not aero-optimal. But since there are compelling reasons to use them, we shouldn't make the aero problem worse by adding devices that solely intend to increase drag.

And I disagree they will have nearly zero aero impact. The aero impact of wheels can't be overstated: just box-section to 60mm deep rims is 23w at only 40kph. I could see adding rotating paddles being 10 times worse.

 

[Ďrãgøn~Fírë]

And here's the legal side of things if the police take him to court over his bike he will lose his driver's license because in the uk a ebikes with throttles that does more than 14mph but under 30mph is a moped which ha can ride on grandfather rights how ever mopeds still need to be mot,d taxed and insured no tax is 6 point on license no insurance is 6 points that's his license gone already then theres points for no mot plus fines court cost etc etc

Anything over 30mph is classed as a 125 motor bike and you need a motorbike license or cbt to ride in public so on top of everything as mentioned above you now have to add driving without a license which can also carry prison sentences

Fred's fastest strava speed is 43mph! He would lose his bike his license face fines and possible imprisonment. Bigger is definitely better

Yes I might do 40mph on the road in front of the police and not be bothered by them isn't because I'm not afraid of losing my bike license because I am and I love my motorbike (oh my motor if I tried to take off in wot on that it would flip half too 2/3rds throttle and shes dancing like a stallion awesome)

When I'm doing 42mph flat out in front of the police I'm clearly on an apollo hard tail mountain bike and I am just a novelty that they like to ask questions and a laugh about what the bike does and they love the 2wd fascinated because many own their own motorbikes. When Fred's doing 20mph hes clearly on a motorbike and is viewed as such