Pikes Peak Race--Entering?

[Green Machine]

There are a number of guys i recognize now from the optigroups who have suddenly come to life on this thread....welcome guys....you guys should start your own thread like stealth did called "optibike owners thread". I am a little hurt none of these guys showed their faces when i was getting flamed when posting here my review of the optibike.....these opti loyalists should have come forward a long time ago when i was on the front line....battling the ES guys reviewing my opti...no support from anyone but a select few free thinking es members back then.....

Anyway wingnut nimbuzz is responsible for pulling this pikes peak ride out of the shadows....and then promptly disappeared in embarrassment once he realized his gigantic blunder ( he threatens the entire opti pikes throne)...and then all these other optiguys suddenly jumped in for reasons i can not yet comprehend.

So i know many es'ers may be a little lost reading this thread not knowing the history and the new players...these new players have come out of the shadows of the optigroup underworld. Only a few of us ES'ers are priveledged to know this dark world....me and tool. So let me fill you guys in.

Here is a breakdown of the optiguy's posting here now...there may be more...but these are the ones i recognize now:

Craig T. - Head of marketing for opti....the charismatic opti face man..the smooth talker..... the leader of the opti google groups. this is the opti version of TylerDurden....its like darth vader vs luke skywalker and craig is definatley luke. THere were some classic tyler vs craig jousts over on the optibike thread...among tylers jabs was THE longest post i have ever seen him write. Craig-skywalker is often quoted by opti loyalists with famous slogans like : "When the green flag drops the BS stops"....i notice optiguys often quote his quotes like this. such a skywalker this craigt guy....but craig likes to use a lot of german nazi rhetoric when he speaks...so he is kind of a combination between Luke Skywalker and Adolph Hitler if that makes sense....bare with me i am trying to come to grips with all this myself.

Nimbuzz- opti "ambaassador" for reals this guy is paid to sale bikes (although he may have lost that badge thanks to this thread) and my guess he is also opti security. He owns both powerful hubs and an opti and knows damn well the difference....but still believes that there is no ebike on the planet besides the opti that can take pikes. I believe he is paid to think this way.

Bike-on - A lopti loyalist....a big believer that opti will prevail in the pikes peak challenge...but not willing to bet more than a beer or a soda.

Remf - a free thinking opiowner who is also an owner of a stealth bomber....so he is open minded. He has seen the speed, power and range of a hub drive and is one of the few optiguys who can relate to the sphere mind set.He has said that if a stealth enters the pikes opti will lose....that is crazy talk over at the optigroups. An Ardent supporter of the Opti fitness and marketing program....a belief that an electric bike is WAY better exercise than a regular bike...but only when that electric bike is an optibike because you have to pedal so much to get any descent speed....come to think of it kind of a putz this guy remf.

Deerfencer - a personal friend with Craig T. according to personal email. Not an optiowner because he doesnt like the noise (will only say that in pm) ....but still a hard core opti loyalist...now he hasnt popped his head here yet...but did show his face a few times in the opti-review thread...one of the good opti-guys this one...i think he wanted to keep this thread on the down low as well.

Madscientist - Ken in the optigroups. This is the most electrical engineer type in the optigroups. In fact my theory is he his one of two in the optibike engineer equatioin...the 2nd being opti-ceaser and inventor jim turner who i heard is following this thread in the shadows furious. This is just my theory but i severely suspect mad scientist is on the opti payroll....ken please correct me if i am wrong. He was the one who gave me this heavy mumbojumbo about a 36 volt 20ah battery being WAY more efficent than a 72 volt 10ah battery despite them containing the same watt hours....anyways....he seems to have inside dope on the internal construction of the opti controller and motor. He impresses the optiguys with his technical suavy and impressive rich optiguy like writing swagger.

extremegreenmachine - A former opti-owner and former opti loyalist who is widely hated over at the optigroups as user "chessmonster". Caused the opti-groups to explode with 200 posts from optiguys all over the world in one week...an optigroup world record. There was more posts in that one week than in the last year at optigroups.The optiguys really turned on chessmonster...calling him an evil speed demon when he bitched that his opti was too slow. He retaliated by saying stuff like the optiguys should stick handicap stickers on their optis so they can legally ride them on the sidewalk and into grocery stores and install baskets on the back...he criticized the opti fitness program as one of the most crazy marketing schemes ever invented...that kind of stuff. The optiguys went bezerk...and out of nowhere ice cool optiguy craig suddenly stepped in to cool down the lipo like fire inviting chessmonster to breakfast in San Francico for one of those electric power meetings. After chessmonster was silenced and left, the optigroups went back down to 3 posts a week...probably bored, the entire opti clan chased the chessmonster over here to ES where all the action is....an angry bunch of optiguys this gang....like buzzing hornets or something.

And for the massacre that will happen at pikes peak this year....the optiguys can blame that dirty dog Nimbuzz and his kooky scheme of inviting the entire ES Gang to the Pikes Peak Challenge...a hard core gasser event that even Physics would have finished last. This just may be a foiled scheme gone bad...and now the optiguys come buzzing over like a angry nest of bees.

Oh and its true that team opti is planning to enter some "ringers" into this years ride...i heard it for sure. Mark my words team opti wont be riding stock bikes...you heard it here first. Tool was dead right on when he said it will be interesting where stock opti will finish compared to ringers.

Thank me guys for exposing this entire evil scheme of sending us to the wrong race, and also pulling all these optiguys out of the shadows...me and Tool should be awarded some kind of ES badge for this one....can i get one of those gigahurtz symbols by my name or something? Tyler?

 

[dogman dan]

Very entertaining to say the least.

I'm not so sure a steath bomber wouldn't melt down before 24 miles of 7-8%. I doubt it would make it if run WOT.

How many motors has remf melted down personally? I've done in 5 myself. Big long hills are really tough on any hubmotor pulling more than about 500-800 watts. The trick to making it would be to help by pedaling, and keep the motor at an equilibrium temp below the meltdown zone. So if in the end, the bomber is running similar wattage to the opti, it then just becomes a pedaling contest. Chances are though, that motor would take more watts longer, and win.

Carrying a big battery is not the problem. My death race bike packed plenty of wh to get to the top of pikes peak.

 

[nicobie]

Parts to build a purpose-built machine for a single event is like a little 5% expense in comparison to the time and labor.

Spoken like a true racer

 

[MadScientist]

Madscientist - Ken in the optigroups. This is the most electrical engineer type in the optigroups. In fact my theory is he his one of two in the optibike engineer equatioin...the 2nd being opti-ceaser and inventor jim turner who i heard is following this thread in the shadows furious. This is just my theory but i severely suspect mad scientist is on the opti payroll....ken please correct me if i am wrong. He was the one who gave me this heavy mumbojumbo about a 36 volt 20ah battery being WAY more efficent than a 72 volt 10ah battery despite them containing the same watt hours....anyways....he seems to have inside dope on the internal construction of the opti controller and motor. He impresses the optiguys with his technical suavy and impressive rich optiguy like writing swagger.

Eric, you truly are an idiot. No, I do not work for Optibike. Thanks for the laugh. Unfortunately you are, overall, far more annoying than funny. Still I figure one more post here to set the record straight is justified despite the adage "please don't feed the trolls".

Regardig your battery confusion, I am not the one who pointed out that running two batteries in series reduces efficiency at original power levels. That is elementary electronics. I'll explain it with detailed "mumbojumbo" if you can handle it, though. Also, I most certainly did not comment on the magnitude of the effect. That depends on battery resistance, among other factors, but I can say that it would be significant on an older Optibike like mine.

Please note that all the "internal information" about Optibikes I have posted is freely available from the same source I got it - the US Patent office. Check out the patent if you are curious. I have no reason to suspect any major changes in the actual bikes, and my comments have been made under that assumption.

And please stop with the Optibike against the world nonsense. Trying to stir up the pot. It is really sad that you just don't get the fact that participants in the Opti group love to see advancements in ebike technology, regardless of where they come from. You are the one fixated on Opti "winning" the Assault on the Peak, not us.

As to the "rich optiguy like writing swagger". Well, swager ... yes. But only because you are so dead wrong with nearly everything you write. As for rich, I note that you're the one with the ridiculous $9000+/- carbon racing bike that you never ride. For my part, I brazed my only road bike out of True Temper tubes, bronze, silver, and love in my garage. I'll tell you something else about my bike, it rides a whole lot better than that fancy Trek of yours. That's a fact.

Sheesh.

 

[Bike_on]

Xgreen,

Where were the Opti guys last month during your "Opti review"? We were sitting back getting amused by your commentary. To me Eric, you get a pass for now. You HAVE spoken beyond the pale to a few folks, but our goal is good ebik'n, and I see you intention to get the Opti faithful to press Boulder for more performance.

No, I will not be at Pikes....can"t do it from Maryland and a family of 7.

Opti owners are made of many engineers who appreciate the new technology. I am an electric as well.

DR

 

[John in CR]

10% efficient hubs is a ridiculous assessment. I blast up miles of a 7-9% grade mountain at 33mph+ into a stiff headwind on a weekly basis. I'm not sure it would handle 11-12% grades with 250lb me aboard unless I regear the pedal line to be able to assist between 25 and 30mph, but my 160lb son could do that ride with no pedaling without issue, and put the Opti in its overpriced place. The larger hubmotors can do the climb, and all it takes is the proper voltage and wheel size for the load and grade, so the motor runs in it's efficient band of operation between peak power and peak efficiency. The extra 10-15lbs of the drive system would be immaterial, so only the misinformed would bring that up. The few percent difference in motor efficiency is more than compensated for by the greater surface area, and the hubbie can also easily be ventilated to swing its ability to shed waste heat firmly in its favor. If the Opti really averaged only 12mph, then I have no doubt at all last year's winning time can be halved with a hubmotored ebike set up properly for the climb.

 

[Alan B]

Considering this grade is easily within hubmotor range, and that carrying sufficient battery is not a problem, this "race" comes down to cooling the hubmotor. If the Opti is putting out, say, 600 watts to the pavement, then the hubmotor must do at least that much. If the efficiency of the hubmotor while climbing this grade, is, say 50% then it will have to dissipate 600 watts. In the thin, low humidity air, this becomes the challenge. Folks don't seem to understand that their everyday experience is not transferable to these conditions.

This might be one case where two hubmotors make sense, front and rear drive. To increase the heat dissipation. Or use a larger hubmotor operated at below its normal rating to keep it cool.

This is not a race for overpowering a hubmotor. It will just fail to reach the finish. Cooling and efficiency are key. Choose a hubmotor setup that is operating at high efficiency much of the time (say 80%). Still the power dissipation capability is reduced, but there is less heat to dissipate.

Two hubmotors might also allow optimization for different speed ranges.

Development of some form of water cooling would change the whole game.

 

[John in CR]

Alan,

If a hubmotor is running the race it's only chance of survival, the same for any brushless motor, Opti included, is to run the motor in the rpm range that is above peak power, which occurs at half of no load speed. That's going to put efficiency between 70 and 80% for any motor worth using for such an attempt. A non-intuitive example of the correct motor choice is to use the high speed version of the new Xlyte motor in a comparably smaller wheel instead of using the torque model. That's because the HS will run at 80% efficiency at peak power using voltages of 60V and higher, compared to 70% for the torque model. Not only would the torque model produce 50% more heat, but turning at 40% slower rpm it would be less able to dissipate heat. Improper gearing is what knocked Luke out of the Death Race, though the motor may have had pretty burned out windings already. Dogman's issue was different, because he was underpowered for the speed he was trying to run. It was like the Opti trying to double it's speed with no change in the motor, something that would burn it up too.

If you try to go slower than WOT either by throttle or a speed control switch, then all you accomplish is putting significant stress on your controller thru current limiting and greatly narrowing your prime band of operation, along with reducing motor efficiency. A smaller wheel is the way to go to lower the gearing, just like the lower powered Opti has to do, though it has more gearing flexibility. With the hubbie you need to gear for the steepest section and carry enough battery for WOT the entire way.

 

[Alan B]

Good morning John, we agree on a lot of things.

Choosing the motor(s) is key. Wheel size is part of that equation. So is voltage and current. Changing from speed to torque models of a motor typically only changes the voltage and current relationship, not much else.

The only chance of survival is to operate the motor(s) below their heat dissipation capability.

Two motors double the heat dissipation capability. Each only sees half the load, so they can operate at half the power. So a four time improvement! (no, just double )

Running at WOT to avoid PWM losses is not practical, many things limit PWM duty cycle aside from the throttle. PWM losses are not the problem here anyway, the controller can be fan cooled, etc, and sized to survive. We are not talking about that much power.

If you really want to run WOT then just reduce system voltage, but you lose acceleration and top speed and have poor top end performance and no control.

Oh, don't forget to get a lightweight strong pedaling pilot who is accustomed to altitude to ride the bike. Every bit helps, keep that system weight down.

So pick the motor(s) and wheel size, voltage and current, and do the calculations and see what the dissipation is, and estimate if it melts. This is fairly predictable. It is hard to be certain about the dissipation capability, but we can at least see what speed and power consumption would result and what dissipation would be required.

 

[Green Machine]

Man those optiguys are a mean spirited ornery bunch...mean and nasty with no sense of humor. Using hard words like "idiot" "troller" etc. Imagine calling me a "troller" those 2 bit opti shadowers. Imagine i was going head to head with those beasts over at the optigroup with bunches of them feeding on me with the exact same stubborn mindset. Kens assertions that everything i write is pure wrong...that kind of garbage. The actual opti company guys were the only coolsters who seemed fun to meet...did meet them and they were cool.....poor opti management working with a really mean spirited demographic. You know you got to have a solid product when you are selling something that costs so much with a warranty to such a mean group of people. Hats off to opti for winning that crowd over.

You think the king of the hills riding on 13k best bikes in the world would be more humble...and nice to everyone thankful they are so rich.

Reminds me of a video some friends shot in the golf course behind my house playing with some golfers...i am going to slop playing with those optiguys...i might get hurt. My friend in the video got hit at close range with a golf club.

http://www.youtube.com/watch?v=hSdIaEDT1Hw

 

[John in CR]

Alan,

It goes without saying that no system gas, electric, or other has to run below the point where waste heat exceeds the system's ability to dissipate that heat. That threshold is crossed at two points, one at the low end (this is a race so that one should be ignored, but easing up a mountain babying the throttle is doing exactly that.), and the other at the high end where the motor needs to run higher rpm than it's peak power point for that voltage. Sure 2 motors is probably the easiest route, but even then, you want the right "gearing".

Spend some time with the Ebikes.ca simulator, because voltage and throttle position do impact efficiency. Also, running up mountains at high power and partial throttle is one of the surest ways there is to kill controller. Under certain conditions, partial throttle can even kill a controller at under 5mph on flat ground. Both the controller and motor are happiest running WOT at a speed that puts the motor in its prime band of operation between peak power and peak efficiency.

Gearing is a huge part of the equation, and the one most typically ignored with hubmotors, because people size the wheel for their bike, not the needs of the motor. The wider band of torque and efficiency than ICE's doesn't make them immune to gearing issues. In fact the fixed gearing of a hub motor, makes it even more important when pushing performance. Tweaking voltage and current limits are only part of the equation, with motor and gearing selection equally, if not more, important.

 

[Alan B]

John,

I pretty much agree with that.

Except on the WOT thing:

Spend some time doing the calculations for PWM electronics inside the controller. The ONLY way to limit phase current is to REDUCE the PWM duty cycle. There are many misconceptions about how this works. People solder their shunts and then wonder why the FETs blow up because the controller didn't have a true reading of current. Controllers are designed to use PWM all the time, not to be run only WOT. The PWM losses were designed to be within the ratings of the parts. The problem comes when folks put too much duty cycle in for the current back EMF, supply voltage and motor impedance (through fiddling parameters and shunts). The applied voltage minus back emf generates huge phase currents and overheats the FETs. Properly designed controllers with valid parameters don't have this problem. Even if the user slams the throttle on full they limit the PWM to a value that generates safe phase currents for the FETs. This throttling is critical at zero speed because that is where back EMF is zero and the phase currents are the greatest. When a controller blows right off the line, that just shows that the mods to it defeated its protection design and allowed significantly excessive phase currents. We really need some open controller designs to work with instead of hacking the closed code infineons!

One problem area may be this "block time" setting. If it really does disable phase current limiting during hard acceleration then the phase current limit is determined solely by impedances. In a high voltage low impedance system this can result in immediate fail for the FETs. It is not clear if that is exactly what it does, but these controllers weren't originally designed for the high voltage/low resistance systems we sometimes use them on, so we are straying outside their original design. While block time works fine on a low power system it may be death to the controller on high power.

In summary, if the controller is overheating, PWM is a small part of that heat, and the real problem is the controller is not sized for the job.

Anyway, we don't have to agree on this. Heard your ES Podcast the other day. Nice Job! Have a nice day.

 

[dogman dan]

I've climbed some huge hills by using half throttle. Talking 10 miles long, 8-10%. The key to it is pedaling to a speed faster than the motor alone gives you at that throttle setting. The same priciple applies to riding wot. Pedal up some more speed, and everything is getting less strain. Puts that motor in the happy place. I'm still a pedaler, so I do this habitually.

I don't always understand the motor and controller theory, but I do know this works. Motor may still fail, but the controller doesn't. So a guy on the bike that can pedal some significant watts at 12,000 feet would be a key item. I'm still good to about 9,000 feet. But I stopped playing hard at 14000 feet some time ago.

 

[Alan B]

One interesting question - is bottled oxygen too heavy to help here? A little O2 could help compensate for the altitude. Probably consume too much when working this hard, though, making it impractical. Maybe LOx? Nevermind. That might lead to other things.

 

[John in CR]

Alan,

You're missing some parts to the puzzle with the theoretical view of the controller operation. The Ebikes.ca simulator has proven quite reliable in predicting motor performance. The following 2 sims highlight my point that WOT should be the target throttle position. The WOT simulation shows a nice broad range of prime operation with a 100rpm range between max power and max efficiency. You'll also note that efficiency doesn't drop below 70% until over 150rpm below max power, giving a very wide range of good operation.
View attachment 1

Now look at what happens at 50% throttle. Peak power occurs well before the motor reaches good efficiency, so power is already dropping rapidly before efficiency gets to even 70%. It would be difficult if not impossible to try to maintain a speed in such a narrow band of prime efficiency, and would require an exact grade of hill to do so. Every change in grade is going to require a change in throttle, resulting in efficiency dipping dangerously low, because you'd actually end up repeatedly trying to accelerate going up hill. Since you're below 100% duty, the controller would be chopping the current into more pulses, greatly increasing stress on the controller. With a 25 mile climb the only question would be which would go first, the motor because it's running at far lower average efficiency or the controller because it's being stressed so hard. Take it from someone who blasts up steep mountains never below 25mph, you want your controller operating at or as close to full duty as possible, and you want your hubbie turning as high of rpms as possible under the heavy continuous loads of riding up mountains.

 

[Alan B]

John,

The ebikes.ca simulator is excellent, but it doesn't easily give the whole picture view of the parameter space. What we really want is a graph with the PWM, resultant speed, and efficiency for one set of gradient, load, etc conditions. From each of the ebikes.ca graphs we can get one point for this graph, so it takes a lot of graphing, calculating and replotting to get what we actually want to look at. You have to take one ebikes.ca graph, then intersect it with the load for the gradient and determine the equilibrium speed for that; then choose a different pwm setting and do the whole thing again. Not easy at all.

If you are running WOT in a real application it means your system voltage is too low. The PWM is merely converting the system voltage into a lower voltage for the motor. By running at 50% throttle you are operating the motor at half the voltage (which is quarter power, waay down the scale). The motor efficiency has to do more with RPM and load, so by reducing the throttle to 50% you have changed the RPM range into a range not efficient for that motor. Simply went too far. The motor needs to be selected for RPM/load for the application, then the voltage/current chosen to meet the needs of the load.

If you run WOT you will have no control of speed. Each change of gradient will change the speed.

PWM allows us to run a higher system voltage and control the voltage to the motor. There is a small efficiency loss in the controller associated with doing this, but in return we get control, which is important for a race.

There is a little heating in the motor from PWM, but again it is not a major component of the total heat.

Anyway, this obsession with running WOT is strange. Nobody likes a vehicle they have to run at WOT. Even you, John, talk about wanting to have some margin at the top. This is necessary for control and safety. The performance price we pay for doing this is not zero, but it is fairly small. It is not the primary driver of the efficiency issue.

I do agree that avoiding PWM will give a slight increase in efficiency. But it also deposits the maximum heat in the motor. In this race we have a limit on the heat we can put into the motor. We may need to be able to back off on the heat or the motor won't survive to the top. Do we drive our cars with the pedal floored all the time? Do we resize the engine for each trip?

At least that's my take on it.

And this whole WOT discussion is really beside the point. What is the point is, how will hubmotors do on this climb?

So, John, choose a motor and show us your calculations for the climb! Will your Clyte make it or melt? Let's assume the climb is a single gradient over the total distance, just for comparison purposes. Lets try different motor combinations to see what happens. Do some simulations! Use WOT to keep it simple!

Other folks, pick you fave combination (or the ebike you have) and do this same calculation. Use the ebikes.ca sim. For bike efficiency we need to use another sim. I don't have that link handy. Someone have it?

Let's do some modelling!

 

[TylerDurden]

2KW continuous without overheating will get the job done.

Ask DoctorBass to demonstrate it on his new dyno.

 

[Alan B]

2KW continuous without overheating will get the job done.

Ask DoctorBass to demonstrate it on his new dyno.

But will it stay cool at 10-14,000 feet? We had problems with computer equipment at these altitudes on a telescope project. Air doesn't cool very well above 9,000 feet or so. Of course DrBass will just put his dyno in his vacuum chamber and test it!!

 

[Alan B]

9C 9x7 Pike's Peak Ride Simulation

Using the simulator at www.ebikes.ca/simulator

Justin doesn't have the 6x10 motor in his simulator (frustrating, but MANY things are missing)

So I went with the popular Nine Continents 9x7 as a point of reference. I picked a 15S LiFe battery (no LiPo available there, though could enter custom values to get that, but not for this run):

Battery 48V 15S LiFe
Wheel 26"
Controller 40A
Throttle 100%

Then, over at:

http://www.mne.psu.edu/lamancusa/ProdDiss/Bicycle/bikecalc1.htm

I entered some specs for a typical ebike:

Rider 200 lbs
Bike 65 lbs
Grade 6.7% (from the ride info, average of entire climb)
Mechanical losses 5%
Air resistance .004
Rolling resistance .007

Then you do an iterative dance between the two programs to balance thrust versus traction force for the same speed to find out how fast it would go:

Drum Roll.. And the answer is:

Equilibrium at just over 20 mph!
Traction required 23 lb
Motor thrust 24 lb available (pretty near exact balance, so you can throttle back a tiny bit...)
950/964 watts depending on which you read
Motor efficiency 73%

This would indicate total power to motor 1320 watts

Motor power dissipation would be about 360 watts

So the real question becomes, how long would a 9C last dissipating 360 watts of heat? At 14,000 feet??

At this rate it would take 1.23 hours to reach the top
And 1.62 kwh of battery plus controller losses

Another question is will throttling back help reduce the power dissipation? This solution was at max throttle, and it was beyond the current limit point, so there was no PWM. But throttling back drops efficiency as well as traction force needed. Also air resistance drops. Where will it all end up??

If we drop to 15 mph (still enough to beat Opti... ) the traction force required changes to 21.5 pounds. So now we play with the throttle to match the simulator to 21.5 pounds of thrust at that speed. I find that at 75% throttle we have about 22 pounds of thrust at 15 mph on the simulator. Now what does that mean - pick the data off the new graph:

Motor efficiency 70%
Output Power 676 watts
Motor input power 966 watts
Motor heat 290 watts

Speed dropped from 20 to 15 mph (-25%)
Motor heat dropped from 360 watts to 290 watts (-19%)

So lowering the throttle DOES DROP THE HEAT IN THE MOTOR and this debunks the widely held WOT MYTH

At this rate it would take 1.63 hours to reach the top
And consume 1.58 kwh of battery plus controller losses

My apologies in advance if I made any mistakes. Find'em and we'll fix'em. This is how we learn. I ran many, many of these types of analyses when I was starting out a few months ago. Reading these graphs is tricky. Somewhere you have to intersect the graph with the increasing load from air resistance and climbing, so you don't really operate along these graphs but at one slice. Like load lines for tubes... The graph you operate along is not the same as this graph (though many folks don't realize that), and the actual operating graph is more difficult to construct as it has to model the bike as well as the motor and do hundreds of sets of intersecting sets of calculations. I recall swbluto did a bit more along these lines with his simulator.

 

[John in CR]

Going up mountains is totally different than riding on the street normally, and unless the hill isn't steep enough and the curves too sharp then WOT is where I prefer to keep my throttle pegged. That's because I know the minimum speed I need to maintain or exceed for minimum stress on my system. The proper gearing for such a climb would be where the motor is able to reach the rpm corresponding with peak power through the steepest sections of the route.

The error in your assumption is that the motor's performance curves are identical at WOT or at less than WOT or the lower voltages that partial throttle imitates. That's simply not the case, and lower voltages result in the similar poor performance that I demonstrated in the previous graph. The 33V A123 sim at WOT is almost identical to the 66V at 50%. The small losses of PWM are minuscule compared to what really takes place both in the controller and in the motor.

Go ahead and do your modeling. Personally, I'm not going to bother because I've taken my bike up enough grades and done enough simulations to know how to fill in the graphs for the in between points. To conquer this climb, I'd only need to know the length and grade of the steepest section, to make sure my wheel size gives me the appropriate gearing to maintain my target minimum rpm. For that kind of altitude, I'd go active with my cooling, and after that it's just a matter of budgeting my battery. I have a variety of grades available to me nearby of sufficient length for me to test even 20%+, and as long as I know I can handle the steepest section, then the rest will be a piece of cake, because lesser grades will require less power and the resulting higher rpms will result in higher efficiency. That's why gearing to handle the steepest section at an rpm above peak power ensures success with sufficient battery.

 

[itchynackers]

Sounds like we (endless sphere folk) need a couple of entrants. Each would use a slightly different strategy, so as to try to discover what would work, or not. Each entrant would discuss with the other their strategy (and stick to it during the race no matter what). Maybe someone would try WOT, the other attempts to average 20mph with pedaling, another 15mph with pedaling, etc... We don't want everyone going full-tilt-boogie up the hill (like in the Death Race). We just want to beat Opti, and the record.

 

[Alan B]

So, John, find the flaw in the detailed model posting just before yours. It indicates convincingly that reducing throttle reduces motor heat. WOT is fine, but heats the motor faster on the same gradient. This by Justin's own motor model.

Remember, the motor doesn't actually see the PWM. The inductance of the motor filters the PWM to a tiny ripple. It only sees voltage and current. PWM just reduces the voltage. Nothing magic. Just a convenient voltage knob.

 

[John in CR]

Alan, you didn't disprove any "myth". I never said WOT would always result in the lowest heat being dissipated at any moment in time. That's only part of the story, and one argument against it is the impossibility for you to determine a throttle position that results in 75% duty, because 75% throttle position isn't the same as 75% duty on a hill, and the speed switch won't do it either. Also, don't forget about the motor's lesser ability to dissipate heat at the lower rpm. Go ahead and ride up mountains at partial throttle and learn the hard way. The secret is in the gearing, not the throttle position.

 

[John in CR]

...and gearing for WOT at that same speed will result in lower heat being generated.

 

[Alan B]

John,

Finding the 75% point is easy. Just go 15mph and you'll be there.

We can go back and forth on this, but I just demonstrated two points on a contiuum that will show that reducing throttle reduces heat. That is the way electric motors work. If they didn't then reducing throttle would increase watt-hour per mile consumption, and we all know that doesn't happen. The standard motor graphs are misleading due to the varying load they represent, so making judgements from them is fraught with misunderstanding.

Now on the issue of motor RPM changing heat dissipation capability, that is an interesting question. I suspect you are correct there, but the function of speed is likely very weak. So it is not going to be all that different at 15 vs 20 mph. But I'll leave that to someone else to determine since we don't have any models available to us for that comparison.

Have a nice day, John. It has been fun going through the numbers again.