volavoile Posted October 29, 2016 Share Posted October 29, 2016 At 40 km/h, the air drag requises more than 900 Watts. With current lisses, it me ans you have less than 300 watts left! Cx 1,7 Area 0,5 1,2kg/m3... Do the calculation! Link to comment Share on other sites More sharing options...
zlymex Posted October 29, 2016 Share Posted October 29, 2016 3 minutes ago, MoNo said: It would be interesting to know the max current as a function of speed to compare with the measured current and get an idea of the torque reserve. Actually there are two currents: One is the supply current(Is) for which I measured. The other is the armature current(Ia) for which Gotway measured and may limit, and I think this current can be measured by app such as Wheellog. 'Ia' is governed by the speed-torque curve, 'Is' is usually smaller than 'Ia' especially at low speed. I've estimated the relationship of the two, and also put them onto the speed-torque curve for different riding scenarios. However, there are some refinement before I show it here. . Link to comment Share on other sites More sharing options...
yourtoys7 Posted October 29, 2016 Author Share Posted October 29, 2016 On 10/28/2016 at 4:03 AM, volavoile said: @yourtoys7, just a few questions.... What is your Weight? Was there a slope where you falled? 170, very little uphill. Link to comment Share on other sites More sharing options...
volavoile Posted October 29, 2016 Share Posted October 29, 2016 Below a calculation of what could be a safe spped limit on our wheels in order to avoid sudden cut off. The speed is the one you will be able to switch from flat to small slope of 10%.... as you can see, speed is much slower than what marketing says! ? Link to comment Share on other sites More sharing options...
volavoile Posted October 29, 2016 Share Posted October 29, 2016 Weight in kg.... sorry, I am French! Very little sloop, like 5%? With your weight, and a 5% slope, max speed shall be 30! Link to comment Share on other sites More sharing options...
Mono Posted October 29, 2016 Share Posted October 29, 2016 3 hours ago, volavoile said: Below a calculation of what could be a safe spped limit on our wheels in order to avoid sudden cut off. The speed is the one you will be able to switch from flat to small slope of 10%.... as you can see, speed is much slower than what marketing says! ? How do you compute the necessary power for a given speed on flat ground? Link to comment Share on other sites More sharing options...
Cloud Posted October 29, 2016 Share Posted October 29, 2016 3 hours ago, volavoile said: Below a calculation of what could be a safe spped limit on our wheels in order to avoid sudden cut off. The speed is the one you will be able to switch from flat to small slope of 10%.... as you can see, speed is much slower than what marketing says! ? How did you calculate that? You may need an adjustment to the calcs, unless i misunderstood the graph or the criteria for safety. I am 100, sometimes more with clothes and backpack and i rode ks14 800w quite often at 30kmh and reached up to 33kmh with no cutouts. Maybe i was pushing my luck a bit, but the graph suggests that the safe speed for me is below 13 kmh? Or is this in mph? Link to comment Share on other sites More sharing options...
volavoile Posted October 29, 2016 Share Posted October 29, 2016 French, so km/h and kg!? In fact, I broke seriously my shoulder last February, and since EUC is so good, I needed to understand why.. because NINEBOT'S explanation where not clear. I still do not know if it was a technical fault or else... the fact is faceplate at approximately 20 km/h without any bips nor tilt back. I've been looking in forums main causes of accidents in order to make the best choice for my next EUC... Main causes are : 1- Pilot goes obviously through the limits or alarms (or didn't ear it), 2- cut off of the wheel without alarms (looks like my accident or @yourtoys7's one....)... and for me, this is obviously due to the fact of a too optimistic behaviour of the pilot... 3- fail of the pilot 4- failure of the wheel itself (rare after BMS Modifications! ). The idea of the second one is that the companies are far too optimistic on their wheels performances... and when you run highest speed, you have no margin left in order to raise a very small climb, or the Euc cannot support the power accéleration in order to provide the tilt back. So as soon as you switch from flat to slope, you are over the nominal, and the 0,5 s peak cannot help you! (Ecxcept if you are a 45 kg chinoise pilot) So for the calculation, I add Required power in order to climb the small slope (5% or 10%) related to the weight Power for the air drag And I compare it to the mechanical available power (test shows that 75% of electric power is transformed in mechanical power). The result is clear, and explains many of the accidents, including this one. A fixed limit of speed, or an alarm based on 80% of power for all pilots cannot be considered as a safe limit since the weight of the pilot has a huge impact. My conclusions (of course, you can agree or not... this is just a personal calculation based on simple and optimistic hypothesis) : Ninebot or any 500W wheels cannot ride safely at 25 km/h with a 90 kg pilot, Most of wheels are too optimistic concerning their performances, Constructors shall aware more on some point to be considered by the pilots :weight influence, slow down BEFORE climbing a hill, even a 10 m long Hill ? Of course, as @Cloud says... it is possible to ride 30 for him, on flat.... but when at this speed you face a slope... be prepared to loose your teeth! ? you just have no safety margin... Power's safety for wheeler... If you do not want metal in your bones, ride safely! Link to comment Share on other sites More sharing options...
Hunka Hunka Burning Love Posted October 29, 2016 Share Posted October 29, 2016 I'm no orthopedic surgeryologist or woodworkingologist, but those two screws next to the lower one appear a little too long? Maybe @Marty Backe can comment. Link to comment Share on other sites More sharing options...
volavoile Posted October 29, 2016 Share Posted October 29, 2016 I hope you could understand the idea despite my poor English! I'lI put the excel file later. Link to comment Share on other sites More sharing options...
volavoile Posted October 29, 2016 Share Posted October 29, 2016 Just now, Hunka Hunka Burning Love said: I'm no orthopedic surgeryologist or woodworkingologist, but those two screws next to the lower one appear a little too long? Maybe @Marty Backe can comment. In fact, it is not the one I have in my shoulder, but it looks like.. and I agree for the size of the screws.... mine look better... but the same before surgery.... 4 pièces! If I can find the real picture, I could be interested in your professional point of view!??? Link to comment Share on other sites More sharing options...
Marty Backe Posted October 29, 2016 Share Posted October 29, 2016 1 hour ago, Hunka Hunka Burning Love said: I'm no orthopedic surgeryologist or woodworkingologist, but those two screws next to the lower one appear a little too long? Maybe @Marty Backe can comment. I'm no doctor. I don't even pretend to be one Link to comment Share on other sites More sharing options...
Hunka Hunka Burning Love Posted October 29, 2016 Share Posted October 29, 2016 But you have great wood working videos! It's pretty much the same. Just think of it like repairing a broken stool or table leg... PS: BTW if you ever want to be a board certified physician, I know a guy who's good with documents that I can hook you up with. http://forum.electricunicycle.org/topic/5718-sweden-bans-cameras-on-drones/?do=findComment&comment=67470 12 minutes in you can see the hardware they use... (Not for the faint of heart) https://youtu.be/8tD1PD69_7Y Link to comment Share on other sites More sharing options...
Marty Backe Posted October 29, 2016 Share Posted October 29, 2016 3 minutes ago, Hunka Hunka Burning Love said: But you have great wood working videos! It's pretty much the same. Just think of it like repairing a broken stool or table leg... Well in that case I would certainly ask for my money back because they obviously picked the wrong size of screw. Amateurs! Link to comment Share on other sites More sharing options...
Cloud Posted October 29, 2016 Share Posted October 29, 2016 2 hours ago, Hunka Hunka Burning Love said: I'm no orthopedic surgeryologist or woodworkingologist, but those two screws next to the lower one appear a little too long? Maybe @Marty Backe can comment. Maybe they wanted to go all the way thru with the screw so they can out a nut on it on the other side Link to comment Share on other sites More sharing options...
The Fat Unicyclist Posted October 29, 2016 Share Posted October 29, 2016 7 minutes ago, Cloud said: Maybe they wanted to go all the way thru with the screw so they can out a nut on it on the other side That isn't where you want your nuts... Link to comment Share on other sites More sharing options...
Hunka Hunka Burning Love Posted October 30, 2016 Share Posted October 30, 2016 1 hour ago, Cloud said: Maybe they wanted to go all the way thru with the screw so they can put a nut on it on the other side Let me fix that slight Freudian slip for you Cloudy Cloud. Actually, with further medical thought, maybe they are going transcortical to help ensure good anchorage. You don't want screws popping out all over the place after all. The medullary bone is softer and doesn't make for great retention for fixation screws. Either that or they ran out of medium length screws, and the next visit to Home Depot won't be for a little while. Link to comment Share on other sites More sharing options...
steve454 Posted October 30, 2016 Share Posted October 30, 2016 @volavoile what firmware version are you on? The latest version claims to fix problem of vehicle power on misoperation. I am hoping that means no cutoff before a warning like tiltback or beeping. @yourtoys7 that is a nice looking app you were showing with the top speed achieved. I wish Ninebot app had that feature. Is that an android app, I would really like to have that. Link to comment Share on other sites More sharing options...
volavoile Posted October 30, 2016 Share Posted October 30, 2016 @steve454, this phenomenon is on every wheel, whatever the firmware version: You are on a flat road, and you ride far below highest speed.... no bips bips, no tilt back! Suddenly, you have a gentle Hill to climb..... not big, you feel comfortable with this! So, you do not slow down, and you stay as straight as a I. What happens? The wheel has the information to continue at the same speed, so immediately, the power will change from a nice 200W to a 750W..... over the nominal 500W! In this condition, it has only the peak time, let's imagine it can be something below 0,5 second, to inform you that you must slow down before.... it cut off due to immediate over power. Of course, no possibility to make any tilt back... because in order to provide it, the wheel must accelerate, and it will increase a little bit more the consumption of power! FACEPLANT,,,,,,!!!?? The same thing with bicycle electrical or not) : since there is no speed regulation, it will decelerate in order to adjust to the maximum power available! Peak power is only a marketing issue, something you can use to go over a bump, but that's all! This is what I think now! Link to comment Share on other sites More sharing options...
MaxLinux Posted October 30, 2016 Share Posted October 30, 2016 3 minutes ago, volavoile said: Suddenly, you have a gentle Hill to climb..... not big, you feel comfortable with this! So, you do not slow down, and you stay as straight as a I. What happens? The wheel has the information to continue at the same speed, so immediately, the power will change from a nice 200W to a 750W. I don't know what most of you do, but whenever I go uphill, even on gentle hills, I never try to keep the same speed. I allow the wheel to slow down. Link to comment Share on other sites More sharing options...
16bitSprite Posted October 30, 2016 Share Posted October 30, 2016 15 minutes ago, MaxLinux said: I don't know what most of you do, but whenever I go uphill, even on gentle hills, I never try to keep the same speed. I allow the wheel to slow down. Exactly right. a EUC is not a bicycle. Slowing down is a must before tackling a slope. Anyone coming from a bicycle background (which let's face it, is most of us) needs to forget the habbit of speeding up before hill climbs, even small ones. Its a recipe for a faceplant. You will get very little to no warning beeps that the wheel is struggling as the change in battery drain can be very fast almost instant. I've even had cut outs going over speed bumps on my 300watt wheel. Slow right down before any hill and start accelerating slowly as you climb. Do not go any faster than you are willing to fall off and expect a cut out at any second. Link to comment Share on other sites More sharing options...
volavoile Posted October 30, 2016 Share Posted October 30, 2016 Great if you do it! Ut on many accident description, people didn't consider they had to do it on a couple of meters long slope... and so didn't undersrand why they kissed the ground! you want to go through the obstacle with inertia... bad idea! Link to comment Share on other sites More sharing options...
Marty Backe Posted October 30, 2016 Share Posted October 30, 2016 3 hours ago, 16bitSprite said: <snip> Slowing down is a must before tackling a slope. <snip> Unless you ride a Gotway Link to comment Share on other sites More sharing options...
16bitSprite Posted October 30, 2016 Share Posted October 30, 2016 9 minutes ago, Marty Backe said: Unless you ride a Gotway Of course with a Gotway, Everest is a mere bump in the road. Link to comment Share on other sites More sharing options...
EricGhost Posted October 30, 2016 Share Posted October 30, 2016 I see this post as many others as a further confirmation that a safer situation against faceplant on a EUC is related to : higher engine power, slow speed and therefore higher torque available. Going a bit in excess If you're limited at 25kmh with a 1500w engine and almost trice of the torque of your actual 500w you'll not faceplant on any slope but maybe a 50% or more Link to comment Share on other sites More sharing options...
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