Pikes Peak Race--Entering?

Folks, has this discussion been of any value? It looks to me like a 9x7 would get too hot on this climb, but a pair of them might do it easily. I invite someone to do the analysis for this case. It is pretty easy, just look for half-thrust from each motor and find the operating point on the motor graph. Can a pair of $250 hubmotors best a $16,000 Optibike on its home turf???
 
Very entertaining.

John and Alan both make good points. It's a good mental exercise before the proof. And a perennial debate. :lol:


I'm not sure lower throttle always lowers heat... it always lowers power, but it also shifts the proportion between current to voltage.

Volts go down, but amps (where the heat comes from) go up. Combined with current-limiting further reducing duty-cycle, things can get hot.
 
When the motor drops to too low a speed, efficiency will drop. But it matters not whether PWM is used, or a lower system voltage. PWM is not the problem, motor speed / efficiency is. At least that's one way to look at it.

Too bad it wasn't easier to plot out the whole operating curve. Swbluto could do that in his simulator. He has most of the machinery. Doing this one point at a time is a bit of trouble.
 
Let's caculate another point or two on this operating curve, continuing from above.

10 mph requires 20.4 pounds of thrust.
Adjust throttle to 54% to attain 21 pounds of thrust.
Motor efficiency 60%
Output Power 428 watts
Total motor power 713 watts
Motor heat 285 watts


5 mph requires 19.8 pounds of thrust
34 percent throttle produces 20 pounds of thrust
motor efficiency 46%
motor output power 207 watts
total motor power 450 watts
motor heat 243 watts

Below 5mph the smart ebiker gets off and walks. Clearly this motor needs to be run at 10-15 mph. But we already knew that. We just didn't know that it was okay to do that at less than WOT.

So the trend we see is that motor heat always decreases as throttle is reduced. There may be a little bump on this curve but it is not the bit feature folks seem to think.

Motor efficiency is dropping, but is approximately 50% or better above 5 mph on this gradient. Motor efficiency certainly never drops to anything like 10% for this case until well below 5mph.

It is pretty amazing how well a one speed system can work with an electric motor. Elegant simplicity, operating in near silence, and an amazing range of performance!
 
Alan,

You're still missing that gearing through changing wheel size is the route to ensuring success, not blowing your controller and motor trying to go up the mountain at less than full throttle. Gear that sucker to the speed you want at WOT up the steepest section at get 80% efficiency instead of the stupid 46% and 60% efficiencies you're calculating. Partial throttle is the route to failure, not success, because you'll only succeed in blowing your controller, burning up your motor, and if you're lucky enough not to, then you will have had to carry a lot more battery that was necessary with proper gearing.

The bottom line is that hub motors can easily output more continuous power than the motor on Opti, and that's all it boils down to. In order to do that, it requires proper gearing through wheel size, and you simply can't take a normal ebike set up for flat land riding and use partial throttle, and expect to succeed.
 
Very very interesting guys. For sure, the 2810 motor in 20" rim for the win over the same motor in 26". That ones got to be true.

One thing I don't see you guys including in your discussion of WOT v part throttle. Time changes in the equation. THAT is why the partial throttle works. BTW, you won't be climbing much above 5 % at half throttle in any case. At half throttle on a steep hill, you will bog down into the really heat making power zone of the motor. To sucessfully climb hills at part throttle, you still have to maintian a minimum speed. That speed will be slower for a slow wind motor, and it will be slower for a small wheel. So with a 2810, and 20" wheel, you'd have a great chance of being able to WOT it anyway.

But the bottom line on part throttle, is you change two variables in the equation. You lower the total watts in. Because of the stuff discussed above, the % of watts in heat may increase, but because total watts is less, the motor may still be needing to shed less total heat. You betcha that sweet spot is very very narrow. Pedaling up a bit more speed as I was saying earlier makes that sweet spot wider. But then you have also slowed down, this increases the time in the equation, and simply gives the motor more time to shed x number of btu's.

So you can climb a hill cooler by slowing down, IF the hill is going to take more than 1/2 hour to climb. Short hills, like 2 miles or less, are usually climbed coolest by simply charging them WOT, and getting it over with. Then on the top, the motor watts can drop, and allow the motor to cool.

Bottom line, it all depends on the length of the hill. A really long hill, say 5 miles or longer has to be handled differently than one that is only 2 miles long.

Lastly, climate matters. Cooling on pikes peak could be a problem if it's 10% humidity that day. Or you could be riding in the rain in August, easily, and have great heat transfer.
 
John in CR said:
Alan,

You're still missing that gearing through changing wheel size is the route to ensuring success, not blowing your controller and motor trying to go up the mountain at less than full throttle. Gear that sucker to the speed you want at WOT up the steepest section at get 80% efficiency instead of the stupid 46% and 60% efficiencies you're calculating. Partial throttle is the route to failure, not success, because you'll only succeed in blowing your controller, burning up your motor, and if you're lucky enough not to, then you will have had to carry a lot more battery that was necessary with proper gearing.

The bottom line is that hub motors can easily output more continuous power than the motor on Opti, and that's all it boils down to. In order to do that, it requires proper gearing through wheel size, and you simply can't take a normal ebike set up for flat land riding and use partial throttle, and expect to succeed.
Click to expand...

John, I'm not missing that. Just choosing examples that are interesting to me. This is a demonstration calculation, from that you should move on to choosing others to optimize things. You are free to choose your own. Let's see your calculations, instead of this theory. Show us some data.

As I have shown, partial throttle is not the big problem some people have been led to believe. If your system won't handle partial throttle then you've got the wrong controller or configuration. Repeating old wives tales won't make them true. If you don't like partial throttle then change your system voltage to match. It's that simple. It is not the throttle setting that matters, it is the motor speed. Need to keep the speed up to keep the efficiency up, but more importantly need to keep the total heat lower than the dissipation capability for long climbs. If your motor can dissipate only 300 watts in the above example you'd be better off running partial throttle and keeping the heat output down, even if efficiency drops slightly. These are not short hills that you can charge up, it is 24 miles of climbing. Different from the daily commute stuff. You need to manage the total motor heat budget.

I invite you do to do the calculations, John, instead of making unsubstantiated claims. Show us some numbers. Show us where WOT makes less motor heat than 75% throttle, for example. Everyone already knows that smaller wheels get more torque from hubmotors. That's obvious.

Have a nice day, John.
 
Alan...John....

While you guys are squabbling over all this technical mumbo jumbo, i am in a life or death struggle to watch my neck against the optibike evil forces. Check out the email i got this morning from that rascal dog nimbuzz admitting his evil scheme:

Nimbuzz wrote: Eric, I absolutely do not accept my downgraded character!! On ES you
busted me for being a secret security drone for Opti who set out a
plan with Jim Turner to get the ES guys into the wrong race with gas
cars so they would be liquidated thus eliminating competition. (This
is all true folks) I fully admitted to that criminal action and
exposed my former CIA ties. I will accept nothing less than being
Opti's official "dangerous" hitman. Even if you are way to smart for
me, busting me left and right--I'll succeed with one of my insidious
plans--you just wait!!
Click to expand...
 
Two Motor Simulation

Just for fun, I took a look at two of the 9x7 motors. Other parameters as before.

At 25 mph it requires 25 pounds of thrust on this gradient
requiring 1306 watts
each motor generates 14 pounds of thrust for 28 pounds total
at this speed efficiency is 82%

total motor power 1630 watts (815 per motor)

total motor heat 326 watts or 163 watts per motor

Might just work. (Even in 26" wheels).
 
So who is entering their standard hub design??? I have a couple steel framed, 16" wheeled bikes my kids don't ride if you need that extra torque to succeed.
 
Too funny anybody thought we were dumb enough here at ES, to enter the wrong race. I WAS looking at it at first, and realized instantly the opti bike must have been in some other event. I just didn't know what it was. But some of us have bikes that do belong in that race to the clouds event. :twisted:

Dual 2807 hubs shoud make it up the hill. 1200 watts would do it, and if you only fed each motor 600, then you'd be unlikely to reach an equilbrium temp above 200F. I wish I had the funds to try dual 2810's on that hill.
 
Alan B said:
As I have shown, partial throttle is not the big problem some people have been led to believe. If your system won't handle partial throttle then you've got the wrong controller or configuration. Repeating old wives tales won't make them true. If you don't like partial throttle then change your system voltage to match. It's that simple. It is not the throttle setting that matters, it is the motor speed.
Click to expand...


Actually... Partial throttle can and do make a massive negative impact. The simulators assume a switching freq that is high enough to never saturate, so current control never has over-shoot (like it does in real life).

On motors like John's, which have a higher KV than the x5302, light throttle loads equal cooked motors and controllers. I personally know this from experience, both with running his controllers until they were flesh-searing hot and blew up, as well as running the motors until the heat was so great they started to make squeaking noises from the thermal distortion causing parts to interfere.

What makes them magic-smoke-producing hot? Rolling through the city in low speed traffic at light throttle loads. What makes the controller and motor run pretty cool and stable? Blasting along at 50-60mph at full throttle.
 
Hi Luke,

If the switching frequency is low enough that there is substantial PWM ripple on the motor I would say the controller and motor are not really suited for each other, and agree that Justin's model may not cover that (though he does use actual inductance and frequency parameters, apparently). Many problems will occur, and efficiency will be low at most throttle settings. Operating John's 50 mph motors at 5 mph is a pretty outside case though, and even this modelling does show at low throttle the heat is not dropping off much. Operating these motors at low speed is not efficient. I don't think it would matter if it was done with low voltage DC or PWM. The problem is the speed, not the PWM. The motor is being operated essentially at stall speed. Do we blame the throttle, PWM, gearing or the operational speed??
 
Alan B said:
Do we blame the throttle, PWM, gearing or the operational speed??
Click to expand...


Well, we know the simulator can't calculate for the transients. We know in real-life in light-throttle partial throttle cruising, the controllers want to boil and the motors start smoking. At wide-open, they zip around happily issue-free until the battery goes flat. These are the things we know for certain, I've been there and experienced it in person.


I recall a time with SWbluto where he was claiming partial throttle on the RC ESC's could only place less stress on them etc, I told him in practice, it's where things turn plasma. It took somebody (one of the high level EE's here) creating a switching loss map calc, current bucking calc to show him on paper the thermal losses at light throttle could be something like 85watts of heating light throttle, and 20watts of heating when WOT. He still didn't believe it, and it took an article from Castle Creations warning of and explaining to avoid light throttle loading as much as possible, as it's when the controllers/motors tend to fail. Most common failure I see being helicopter guys just trimming out a bird at like 10% throttle on the ground with a heli that handles monster abuse all day at high throttle loads, yet just twirling with almost no load the ground, the controllers explode into plasma, leaving both motor and controller a charred mess.


When real world testing doesn't match the theory/calculation, we can't pretend we don't see the empirical evidence, we gotta re-write our model to account for whatever effects we were missing. (like in the case of Justin's great calculator, which works great for 95% of ebikes, but has no way to deal with the over-shoot events and transient effects that occur in a setup like John's.)
 
Alan B said:
Luke, maybe we need to help John find the right controllers for his monster motors? Might be possible to solve this problem. Seems like he's pushing the controller too hard, it needs more margins and different PWM frequencies.
Click to expand...


Absolutely agree. I've got a large size Sevcon gen4 ordered for him. :)
 
liveforphysics said:
Alan B said:
Luke, maybe we need to help John find the right controllers for his monster motors? Might be possible to solve this problem. Seems like he's pushing the controller too hard, it needs more margins and different PWM frequencies.
Click to expand...


Absolutely agree. I've got a large size Sevcon gen4 ordered for him. :)
Click to expand...

You've got waay too many nice toys. :shock:
 
My motors just highlight the controller issue. It doesn't change the simple fact that the relationship of the power and efficiency curves changes for the worse with lower throttle. As a matter of fact, they change for the worse as you increase the turn count in the windings of an otherwise identical hubmotor, which I eluded to earlier regarding ideal motor selection being counter-intuitive when it comes to long hills. I was forced into this analysis last year as I started increasing power, because my motors were eating controllers.

Anyone really interested in how these motors perform should play around with the ebikes.ca simulator. Compare the motors with the most extreme winding differences, such as the Xlyte 404 vs 4011 and the 5302 vs 5305. Use the max voltage selection 66V in the simulator to really highlight the differences. It quickly becomes obvious that the lowest turn count motors are far better motors, because not only are they capable of greater power, but their prime operating range is very broad. For a real eye opener take the 5302 and pair it with just a 20A controller and 66V and see how broad and how well matched the power and efficiency curves are. To succeed with that kind of set up, you just have to make sure you can maintain a certain speed up hills.

BTW, guess how many motors I've burned up...None
 
I ride the mountain everyday, in various conditions and grades. Nothing like having to slow down in a climb, to quickly heat a hubmotor and a controller to their limit. I have a short experience of E-bikes and little technical knowledge in electronics, but I know for sure that it's not by riding at partial throttle that one can finish this very long continuous climb.

Use a heavy hubmotor, ride it as fast as it goes, monitor temp, bring some water to cool it quick enough to shorten the necessary overheat pause, and you might make it to the top faster than anyone else. Most of all, don't underestimate the Ah needed in such a long climb, for one could easily fall short of power to make it.
 
On the race last year, a Kalkhoff Pro Connect:
Starting with a fully charged battery, I lost the first of three charge indicator lights after 7.5 miles of moderate climbing. The second red light went out at 14.5 miles. The final light began to blink at 18.5 miles and the motor essentially cut out.

Fortunately, I had the forethought to pack an extra battery! I pulled off to the side of the road to switch batteries only to have the vicious winds topple me over, spent battery in hand, which of course went flying down the road. I retrieved the spent battery, loaded the fresh one and continued up the road. At mile 23.4 I saw the first riders descending from the summit, two riders in full winter ski gear on Optibikes,
Click to expand...

Some of the race results on this thread here:
http://endless-sphere.com/forums/viewtopic.php?f=25&t=20061&start=15#p307181

And the official race results here... although they missed listing some of the bikes as electric:
http://www.outtherecolorado.com/blogs/2010-assault-on-the-peak-results.html
 
MadRhino said:
I ride the mountain everyday, in various conditions and grades. Nothing like having to slow down in a climb, to quickly heat a hubmotor and a controller to their limit. I have a short experience of E-bikes and little technical knowledge in electronics, but I know for sure that it's not by riding at partial throttle that one can finish this very long continuous climb.

Use a heavy hubmotor, ride it as fast as it goes, monitor temp, bring some water to cool it quick enough to shorten the necessary overheat pause, and you might make it to the top faster than anyone else. Most of all, don't underestimate the Ah needed in such a long climb, for one could easily fall short of power to make it.
Click to expand...

MadRhino,
Thanks for adding your own real world results.
 
I could never do this race. The top is over 14,000ft? I'd surely get nasty altitude sickness.
 
I don't disagree with Luke at all, but suspect that what he's observed was a not pedaling style of riding.

I still maintian that you can climb a big long hill cool enough by throttling back. But you MUST also pedal that thing enough to put the motor back into the "happy place". If you don't, you will melt er down. At full thottle blasing along on flat land, you use few watts, you see this on the CA. At 3/4 throttle, you see the same effect, IF you pedal up to a speed that allows the motor to work less. No doubt the controller is getting hotter than at full throttle. But what the controller "feels" is as though it was not climbing a hill, but just motoring down the road on the flat, in economy mode. Which doesn't make a controller well matched to its motor melt down. I've never had my controllers get abnormally hot climbing a large mountain at 3/4 throttle. Half throttle is never enough for a big hill, so I never tested that in real world. Always at least 3/4 throttle, and 10% sections would take full throttle anyway.
 
What about the Bionx System?

I rode a Trek a while back that was outfited with a Bionx System, and the controller will only implement power to the motor upon your pedaling. It puts out various percentages of your effort based upon what you program.

It can match your energy with 25%, 50%, 100% and 200%. But if you stop pedaling the motor won't work beyond two or three seconds.

So, if you're pedaling the whole way, and the motor is matching your power (100%), will the motor still overheat?
 
Of course, you can always overheat yourself to save the motor. :mrgreen:
Nevertheless, this kind of altitude climbing is not for everyone pedaling and aerobic abilities.
 
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