Jonathan Tolhurst Posted February 21, 2017 Share Posted February 21, 2017 Definitely a silly question (and I'm not suggesting anyone try this @EUC Extreme ) but could a modified Electric Unicycle (whose control board algorithm was programmed not to cut out when the wheel exceeded approximately 45 degree angle) be ridden on a "wall of death"? If Yes, How fast would you have to ride on a circular wall with a diameter of 10 meters with a combined wheel/rider weight of 100Kg? Would some of the forces involved prevent or restrict a rider from leaning forward on the pedals? Link to comment Share on other sites More sharing options...
Mono Posted February 21, 2017 Share Posted February 21, 2017 Isn't the angle measured with respect to the downforce rather than gravitational force? Otherwise we couldn't ride sharp turns without the danger of a cut-out. If the downforce exceeds 45 degree you probably anyway slide down the wall. The downforce must always point through rider and wheel, otherwise the rider falls off to the side. It seems to me that the necessary speed is independent of the weight of the vehicle. v = sqrt((gr)/µ) seems to be the magic speed formula with g=9.81m/s^2, r=radius, µ=friction coefficient≈0.5, so 30km/h might do, see Link to comment Share on other sites More sharing options...
dbfrese Posted February 21, 2017 Share Posted February 21, 2017 1 hour ago, Jonathan Tolhurst said: could a modified Electric Unicycle .... be ridden on a "wall of death"? I dunno. But I'd like to see you try! Link to comment Share on other sites More sharing options...
steve454 Posted February 22, 2017 Share Posted February 22, 2017 3 hours ago, Jonathan Tolhurst said: could a modified Electric Unicycle (whose control board algorithm was programmed not to cut out when the wheel exceeded approximately 45 degree angle) be ridden on a "wall of death"? Maybe if it was a modified wall of what you said Link to comment Share on other sites More sharing options...
Chriull Posted February 22, 2017 Share Posted February 22, 2017 13 hours ago, Jonathan Tolhurst said: Definitely a silly question (and I'm not suggesting anyone try this @EUC Extreme ) but could a modified Electric Unicycle (whose control board algorithm was programmed not to cut out when the wheel exceeded approximately 45 degree angle) be ridden on a "wall of death"? If Yes, How fast would you have to ride on a circular wall with a diameter of 10 meters with a combined wheel/rider weight of 100Kg? Would some of the forces involved prevent or restrict a rider from leaning forward on the pedals? 12 hours ago, Mono said: Isn't the angle measured with respect to the downforce rather than gravitational force? Otherwise we couldn't ride sharp turns without the danger of a cut-out. If the downforce exceeds 45 degree you probably anyway slide down the wall. The downforce must always point through rider and wheel, otherwise the rider falls off to the side. Also, it seems to me that the necessary speed is independent of the weight of the vehicle. EDIT: v = sqrt((gr)/µ) seems to be the magic speed formula, so 30km/h might do, see ... Would be great to see a video, if it works out - if the 30 km/h might do it should be possible with the newest wheels! One restriction could be the tires?! Most EUC's used to have children BMX tires designed for a max weight of around 40 kg. So especially for riding in a Wall of Death the tire carcass/sidewall could be way too weak to carry (almost) the whole weight "sideways"... ;( Link to comment Share on other sites More sharing options...
Mono Posted February 22, 2017 Share Posted February 22, 2017 7 hours ago, Chriull said: So especially for riding in a Wall of Death the tire carcass/sidewall could be way too weak to carry (almost) the whole weight "sideways" It is as "sideways" as riding a curve, the difference is only that the downforce (which pushes the CoG onto the contact patch) is larger. Link to comment Share on other sites More sharing options...
pArmitage Posted February 22, 2017 Share Posted February 22, 2017 Sounds like a classic, "Hold my beer" situation. Link to comment Share on other sites More sharing options...
EUC Extreme Posted February 22, 2017 Share Posted February 22, 2017 It is possible. I have many requested permission to race in this. No one refuses. I do not understand why. My Gotway is fully capable of it. Horizontal can run. Link to comment Share on other sites More sharing options...
Ch.Eng.62 Posted February 22, 2017 Share Posted February 22, 2017 I really think it is non possible. The speed of the wheel is function of the angle with the Z axis (vertical line) When the wheel is in the cage the direction of the Z axis is rotaiting. Never mind in which plane, vertical or horizontal My opinion only Link to comment Share on other sites More sharing options...
Hunka Hunka Burning Love Posted February 22, 2017 Share Posted February 22, 2017 I could see how one could disable the auto-shutdown over a certain degree tilt feature in firmware, but how would one apply enough forward lean pressure if gravity is pulling sideways? That's an interesting physics question to think about. I could see rolling around the lower half of the sphere, but as you approach the horizontal equator area how can you maintain a forward lean? Link to comment Share on other sites More sharing options...
Tomek Posted February 22, 2017 Share Posted February 22, 2017 1 hour ago, Cheng62 said: I really think it is non possible. The speed of the wheel is function of the angle with the Z axis (vertical line) When the wheel is in the cage the direction of the Z axis is rotaiting. Never mind in which plane, vertical or horizontal My opinion only you're forgetting about the centrifugal force, the very same reason why the guy in the video doesn't fall down with his bike when upside down. for the wheel sensors (and the rider) at a certain speed it will "feel" as if the gravity is pulling towards the outside of the sphere. So, in other words, the centrifugal force will fool the wheel to think that the Z-axis is turning as you ride upside down... of course the force will not be exactly perpendicular to the surface of the sphere, because there will always be the gravity component, going up will feel like you're going uphill and going down will feel downhill, upside down, you'll feel much lighter, and on the bottom you will feel super heavy. Link to comment Share on other sites More sharing options...
Ch.Eng.62 Posted February 22, 2017 Share Posted February 22, 2017 By the way it depends of the sensors (which I do not know). If the sensor is like a gyroscope, it will try to maintain the direction to the universe (or axis Z will be steady), so it isn't working in our case. But if it is as accelerometer, probably it will be directed to the centre of the Earth, or centrifugal forces. I don't know. Probably it is possible. Link to comment Share on other sites More sharing options...
Mono Posted February 22, 2017 Share Posted February 22, 2017 51 minutes ago, Cheng62 said: By the way it depends of the sensors (which I do not know). If the sensor is like a gyroscope, it will try to maintain the direction to the universe (or axis Z will be steady), so it isn't working in our case. This seems what the OP suggested. However, if the universe is the reference frame, an EUC that works in China should only work upside down in the Argentina. Even worse, it should only work a few hours per day (or night) in upright position anywhere. Link to comment Share on other sites More sharing options...
Rehab1 Posted February 22, 2017 Share Posted February 22, 2017 3 hours ago, Hunka Hunka Burning Love said: I could see rolling around the lower half of the sphere, but as you approach the horizontal equator area how can you maintain a forward lean? I believe @EUC Extreme is already determining the best methodological approach to perform this stunt. Act 2: Tight rope ride over Niagara Falls! I believe @Jonathan Tolhurst knew all along that EUC Extreme would take the bait. Link to comment Share on other sites More sharing options...
Ch.Eng.62 Posted February 23, 2017 Share Posted February 23, 2017 6 hours ago, Mono said: This seems what the OP suggested. However, if the universe is the reference frame, an EUC that works in China should only work upside down in the Argentina. Even worse, it should only work a few hours per day (or night) in upright position anywhere. Yes, if it is working 24/7, but every switching OFF/ON, the sensor is initialized. I have tried to operate quadcopter on board a ship when it is rolling and pitching. Because first seconds, after switching on, the sensor is not initialized properly, after that the quadcopter is like a drunk Link to comment Share on other sites More sharing options...
EUC Extreme Posted February 23, 2017 Share Posted February 23, 2017 I do not think of any reason why would not be possible to drive the barrel horizontally in a circle. This almost do it. Is added to a speed .. I have every intention to try this. Now, at the moment there is a request to an abandoned ball to the owner, to get them to drive there. But I can not get the person to contact. Link to comment Share on other sites More sharing options...
Smoother Posted February 23, 2017 Share Posted February 23, 2017 @EUC Extreme that was just too much fun ! I'm SO going to look for a skate park around here. Who's your friend? Back to the subject; it appears science would not allow a wall of death EUC ride, but @EUC Extreme and friend seem almost to have achieved it here. Yes I know they're not going rounded and round a vertical tube, but they get close. Maybe it would work, after all, did you know that scientists have proved that the bumble bee cannot fly? Link to comment Share on other sites More sharing options...
Frode Posted February 23, 2017 Share Posted February 23, 2017 8 hours ago, Cheng62 said: By the way it depends of the sensors (which I do not know). If the sensor is like a gyroscope, it will try to maintain the direction to the universe (or axis Z will be steady), so it isn't working in our case. But if it is as accelerometer, probably it will be directed to the centre of the Earth, or centrifugal forces. I don't know. Probably it is possible. I think it probably is a combintion of the two. The accelerometers maintain the vertical over time, the gyro maintain the orientation over short time (short time means seconds to sub seconds). Gyros will always have a drift over time (over hours to minutes, maybe even faster for simple and inexpencive ones) that must be compensated for in some way. Just my thoughts... Link to comment Share on other sites More sharing options...
Ch.Eng.62 Posted February 23, 2017 Share Posted February 23, 2017 2 hours ago, EUC Extreme said: I do not think of any reason why would not be possible to drive the barrel horizontally in a circle. This almost do it. Is added to a speed .. I have every intention to try this. Now, at the moment there is a request to an abandoned ball to the owner, to get them to drive there. But I can not get the person to contact. It will be very interesting. Good luck Link to comment Share on other sites More sharing options...
Frode Posted February 23, 2017 Share Posted February 23, 2017 3 hours ago, Cheng62 said: Yes, if it is working 24/7, but every switching OFF/ON, the sensor is initialized. The earth is rotating 15 degrees an hour, so in the east-west direction the tilt will be very off vertical in relatively short time if the universe is the reference. If I tilt my King Song KS-16 in the forward or backward direction and then turn it on, it will slowly (within some seconds) align itself to the vertical drection. How can it sense the vertical direction if it only has a gyro? Link to comment Share on other sites More sharing options...
esaj Posted February 23, 2017 Share Posted February 23, 2017 1 hour ago, Frode said: If I tilt my King Song KS-16 in the forward or backward direction and then turn it on, it will slowly (within some seconds) align itself to the vertical drection. How can it sense the vertical direction if it only has a gyro? The gyros are multi-axis, for example the MPU-6050, which is used in many wheels, has 6 axes (3-axis gyro + 3-axis accelerometer): https://www.invensense.com/products/motion-tracking/6-axis/mpu-6050/ The MPU-9250 is 9-axis (3-axis gyro + 3-axis accelerometer + 3-axis magnetometer). I don't know if that's used in wheels, the magnetometer axes are reference to the magnetic poles of the Earth (so kinda like a 3-dimensional compass). The reason for using gyro + accelerometer seems to be that gyros tend to "drift" during use, but the accelerometer data can be used to offset that, as used in "sensor fusion" algorithms to enhance the resolution/precision. The accelerometer can also be used to sense which way is down (at least when stationary), because the gravity will pull the axes vertical to ground downwards at constant acceleration (if a single axis isn't exactly vertical, two or more axes will receive a fraction of the acceleration), my best guess is that's what's used in the wheels to detect the "0-position" at start up. The above is a microcontroller detecting the direction of gravity using a 6-axis accelerometer/gyro, not at a very good precision (could also be due to the low resolution of the led-matrix), but I guess the principle is the same. Link to comment Share on other sites More sharing options...
Tomek Posted February 23, 2017 Share Posted February 23, 2017 On 2/23/2017 at 9:51 AM, Frode said: The earth is rotating 15 degrees an hour, so in the east-west direction the tilt will be very off vertical in relatively short time if the universe is the reference. If I tilt my King Song KS-16 in the forward or backward direction and then turn it on, it will slowly (within some seconds) align itself to the vertical drection. How can it sense the vertical direction if it only has a gyro? It has an IMU, which consists of gyros and accelerometers combined. Accelerometers measure g-force, which is the "gravity" force as perceived by the device (i.e. in a free falling state it would be 0, in super-acceleration it would be multiple times the earth's gravity etc.). gyroscopes measure change of orientation in a way unaffected by the g-force (i.e. in a car riding straight and accelerating, the g-force makes you feel as if the car's front moves up, but the gyro doesn't record that perceived rotation change). AFAIK, the question is thus if the EUC controller uses only accelerometer data (that would make it totally fit for the wall of death) or a combination of both (that may, or may not cause trouble, depending on how much the gyro data is factored in, i.e. the gyro data could only be used to reduce jitter on accelerometer data). It can't use only gyro data, because that's always relative, i.e it has no objective point of reference, and not too accurate due to drift over time (i.e. turning back and forth with a same angle a few times will not bring you back to the original angle values) Link to comment Share on other sites More sharing options...
Smoother Posted February 23, 2017 Share Posted February 23, 2017 @Frode wrote..If I tilt my King Song KS-16 in the forward or backward direction and then turn it on, it will slowly (within some seconds) align itself to the vertical drection. How can it sense the vertical direction if it only has a gyro? I've watched my 14c do the "ouch my back, it's so hard to stand upright, but I'll try, ahh, ahh, ahh, that's better" after starting it on a tilt. Very amusing, it reminds me of...me, when I get out of bed, or get off the couch, or get off the toilet, or get up after a face plant or...... edit. Written while @esaj was writing his " more" technical response. So redacted as necessary Link to comment Share on other sites More sharing options...
Frode Posted February 23, 2017 Share Posted February 23, 2017 2 hours ago, esaj said: my best guess is that's what's used in the wheels to detect the "0-position" at start up. Exactely! And also when running. So wether it is possible to drive an EUC in the "wall of death" (i.e. tilt it more from the vertical than the preset turn off without it turning off) will depend on how the values from the accelerometers and the gyros are used. It might adjust the reference for the gyros to a new "vertical" given by the accelerometers, or it may use the accelerometers combined with the gyros to keep better track of the space coordinates (with less drift). My guess is that the truth is somewhere in between, that it will slowly readjust the vertical (slow with respect to typical movements for a typical user). I would not count on it not turning off when it reaches the turn-off tilt angle. I would rather expect it to do exactely that - turn off (because the tilt angle changes too fast for it to adjust to a new "vertical"). But I don't know. Only a peek into the algorithms of the controller - or a test with the speciffic EUC to be used will give the true answer. A test could be without a rider, for example swinging it around in a rope til it reaches the turn off tilt angle with respect to the true vertical. Link to comment Share on other sites More sharing options...
Smoother Posted February 23, 2017 Share Posted February 23, 2017 On 23 February 2017 at 0:53 PM, Frode said: A test could be without a rider Or a trained monkey. No, I'm not volunteering....I'm not trained.? @Rehab1 "abandoned ball" look up a few posts. See the spherical cage? That type of ball, only abandoned. Must have been at chernobyl or pripyat. ? Link to comment Share on other sites More sharing options...
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