Strange oscillation in GT16

[Blackmagicman]

ok guys, thank´s a lot for your fast responding to my problems. I habe checked everything what is pssible from the outside. I nerver opened the wheel but i am absolute sure that the axle nuts are tight. The whell / motor ist absolute fixed. Very funny is also, that the wild wobbling only comes always in playing mode. Whith walking mode sometimes is possible to start a ride and than the wheel behaves absolute normal except the softer mode that don´t suits me well.

I think I wait for an answer of mr. yi chen an wait, what he advises.  Again thanks a lot guys!

[Hunka Hunka Burning Love]

I think @Scatcat also had some wobble issues with his GT16.  He ended up needing to replace his control board and motor which had a broken washer.  I haven't seen your video yet as I'm on iPhone.

[Iero83]

@Blackmagicman Is your GT 16 a V1 or V2? (V2 has different pads and very loud speed alarms). I think the firmware is different as well.

[Blackmagicman]

I think my GT16 is a V1, because of the padding and the alarms.I don´t know about the differenzes in firmware I must check this.  I wrote a mail to mr. Yi chen from rockwheel store, I got my GT16 from him. He is also busy with my problem and will let me know how to fix it soon. I appreciate.

[s.m.]

I ride the 1036Wh version of the GT16 for exactly 2 weeks and 412km. I did not look inside, yet but I think it's a V2. I Bought this wheel because of the 'playing mode' as I expected the rough stiffness known from my old RW GP14.

I'm very impressed of the huge power paired with excellent agility, weight and a good range.

BUT : SOMETIMES it starts to oscillate when I hit the ground coming from a sidewalk (curb height = 7-10cm) on low speed (when i cross a street on greenlight)

This happened now around four times and ended immediately after 1-2 seconds when I slowdown a little while I'm surprised.

So far I couldn't figure it out exactly and it will need some research on what situation this happens reproducible.

For now I think it's only on low speed while I give force for acceleration and jump downwards at the same time.

[Blackmagicman]

On 19.8.2017 at 10:56 PM, Hunka Hunka Burning Love said:

I think @Scatcat also had some wobble issues with his GT16.  He ended up needing to replace his control board and motor which had a broken washer.  I haven't seen your video yet as I'm on iPhone.

I got some mails from mr. yi chen now. According to him a loose motor axle is the reason for the terrific wobble problem. He sent me a video that should show me how to disassemble the wheel.  Maybe the motor axle is loose. I will check out this, but I am very busy during this week. I will try at next weekend and let you know.

[Slaughthammer]

Does Rockwheel use the same method as Gotway does to clamp the pedal hangers to the axle?

[Mrd777]

4 hours ago, Blackmagicman said:

I got some mails from mr. yi chen now. According to him a loose motor axle is the reason for the terrific wobble problem. He sent me a video that should show me how to disassemble the wheel.  Maybe the motor axle is loose. I will check out this, but I am very busy during this week. I will try at next weekend and let you know.

sounds good, I hope this is an easy fix for you, Please post the video as this will be helpful to others. thanks

[Scatcat]

On 2017-08-21 at 7:55 PM, Slaughthammer said:

Does Rockwheel use the same method as Gotway does to clamp the pedal hangers to the axle?

Nope, more like KingSong. The arm is in two parts, upper and lower, the upper connects to the lower with two very fat allen-bolts.

[Scatcat]

On 2017-08-21 at 7:41 PM, Blackmagicman said:

I got some mails from mr. yi chen now. According to him a loose motor axle is the reason for the terrific wobble problem. He sent me a video that should show me how to disassemble the wheel.  Maybe the motor axle is loose. I will check out this, but I am very busy during this week. I will try at next weekend and let you know.

The issue looks a lot like the one I had. Check the bolt-thing. But if it's not that, it may be the gyro on the board that has gone bonkers. Yi sent me a replacement board and that fixed the issue.

[Blackmagicman]

Hello together, enclosed a copy of the text I mailed to mr. yi chen:

hello dear friend yi chen,

I just found time to disassemble the wheel and I think I discovered the problem for all the issues and bad behaviour of my GT16!!  I suggest it is the connection of the pedalarms to the axle at both sides. The pedal arm connection has play there because of a bad mistake drilling that 2 holes for the allen srews too deep in the clamps. Although my weight is not at the upper limit, I am about 75 kg, the allen screws ( 8 mm, two at each side) that are fixing the clamp an so the pedal arm to the shaft are teared out of the clamp, because the holes are drilled too deep. The reduction is too deep and therefore the material (aluminium) left down at the ground of the drill hole is too small, so that the fit tears out. It is really bad produced, poorly made. It is just a little mistake which can have a big impact. I was very closed to a next faceplant if that clamps come off complete and the pedal arms with the footplates come all off.
 
 I will take a video  and some pictures soon to illustrate the Problem.

[US69]

31 minutes ago, Blackmagicman said:

Hello together, enclosed a copy of the text I mailed to mr. yi chen:

hello dear friend yi chen,

I just found time to disassemble the wheel and I think I discovered the problem for all the issues and bad behaviour of my GT16!!  I suggest it is the connection of the pedalarms to the axle at both sides. The pedal arm connection has play there because of a bad mistake drilling that 2 holes for the allen srews too deep in the clamps. Although my weight is not at the upper limit, I am about 75 kg, the allen screws ( 8 mm, two at each side) that are fixing the clamp an so the pedal arm to the shaft are teared out of the clamp, because the holes are drilled too deep. The reduction is too deep and therefore the material (aluminium) left down at the ground of the drill hole is too small, so that the fit tears out. It is really bad produced, poorly made. It is just a little mistake which can have a big impact. I was very closed to a next faceplant if that clamps come off complete and the pedal arms with the footplates come all off.
 
 I will take a video  and some pictures soon to illustrate the Problem.

Wenn ich Dir nen tipp geben darf....

Halt Dein Englisch so EINFACH wie möglich! Yi Chen ist wirklich top und hat nen guten Kundenservice...aber aus Erfahrung:

Mit so einer komplizierten Englischen Beschreibung wird das nix...dann lieber Video, mit ganz einfachen, trivialen Erklärungen...

Nur so...Yi Chen benutzt maximal irgendwelche Übersetzungs programme...und ganz ehrlich..bei deiner Beschreibung hab ich schon Mühe zu folgen!

 

:-)

[Scatcat]

6 minutes ago, KingSong69 said:

Wenn ich Dir nen tipp geben darf....

Halt Dein Englisch so EINFACH wie möglich! Yi Chen ist wirklich top und hat nen guten Kundenservice...aber aus Erfahrung:

Mit so einer komplizierten Englischen Beschreibung wird das nix...dann lieber Video, mit ganz einfachen, trivialen Erklärungen...

Nur so...Yi Chen benutzt maximal irgendwelche Übersetzungs programme...und ganz ehrlich..bei deiner Beschreibung hab ich schon Mühe zu folgen!

 

:-)

Well, if I get the german correctly I can only agree. For Yi Chen translating/understanding English is like me translating/understanding French. I studied French for a few years in high school and college, but haven't used it seriously in >30 years... Reading a post in French I get about 30%, more if it's simple, less if it's complicated.

And given how different the Chinese language are from the germanic and latin languages, translation programs suck.

[Scatcat]

49 minutes ago, Blackmagicman said:

Hello together, enclosed a copy of the text I mailed to mr. yi chen:

hello dear friend yi chen,

I just found time to disassemble the wheel and I think I discovered the problem for all the issues and bad behaviour of my GT16!!  I suggest it is the connection of the pedalarms to the axle at both sides. The pedal arm connection has play there because of a bad mistake drilling that 2 holes for the allen srews too deep in the clamps. Although my weight is not at the upper limit, I am about 75 kg, the allen screws ( 8 mm, two at each side) that are fixing the clamp an so the pedal arm to the shaft are teared out of the clamp, because the holes are drilled too deep. The reduction is too deep and therefore the material (aluminium) left down at the ground of the drill hole is too small, so that the fit tears out. It is really bad produced, poorly made. It is just a little mistake which can have a big impact. I was very closed to a next faceplant if that clamps come off complete and the pedal arms with the footplates come all off.
 
 I will take a video  and some pictures soon to illustrate the Problem.

Try to find a couple of washers that fit the allen-bolts, that should do the trick.

[Mrd777]

1 hour ago, Blackmagicman said:

 
 I will take a video  and some pictures soon to illustrate the Problem.

Please do this, it will be very much appreciated

[Scatcat]

On my first motor, I loosened the pedal arms to take it apart. When I screwed them back on, it was hard to get them tight enough. I ended up folding a piece of aluminium foil to add some bulk to the shaft. About four layers of foil placed on top of the flat of the shaft before screwing it on, which made it far easier to get it super-tight without any play.

The alternative would have been using so much force to screw them down I would have been afraid of doing damage to the bolt- or pedal arm threads.

So, make sure the problem is the bolts going to deep in the arms, not the hole being a bit too big. If there's still a visible crack between the upper and lower parts of the arm, you need a washer to compensate, otherwise you need to do as I did.

Of course you can order new pedal-arms from Yi Chen, and he'll probably send you them as replacement parts, but in the mean time you can test my solution and see if that solves the problem.

[Blackmagicman]

 @KingSong69: Thanks a lot for the tip that my detailed description was much to complicatet. Sorry for that, but my english is not so good and because my profession is automotive enineering it is very technical. In addition it is not easy to describe the Problem with words. Therefore I added a short video and some pictures and I hope these will help more than words to see the problem.

@Scatcat: Thanks for sharing my problems. That you tried to fix the pedal arms with aluminium foil shows that there is something wrong with the connection shaft/pedalarm with your wheel too. The pictures attached show that my upper parts of the pedal arms are bent and even cracked. The main problem is that the holes of the allen screws are bored too deep. There is only 2mm left at the bottom. The last picture shows on the right side how it would look when the hole was drilled as deep as it should be. If so there is 6mm material left at the bottom. The left side shows how deep the holes are drilled truly. They need not to be drilled as deep because that makes the clamps weak at the bottom so that they bent and crack.

Pedal_Arm Play.wmv

[Scatcat]

5 hours ago, Blackmagicman said:

 @KingSong69: Thanks a lot for the tip that my detailed description was much to complicatet. Sorry for that, but my english is not so good and because my profession is automotive enineering it is very technical. In addition it is not easy to describe the Problem with words. Therefore I added a short video and some pictures and I hope these will help more than words to see the problem.

@Scatcat: Thanks for sharing my problems. That you tried to fix the pedal arms with aluminium foil shows that there is something wrong with the connection shaft/pedalarm with your wheel too. The pictures attached show that my upper parts of the pedal arms are bent and even cracked. The main problem is that the holes of the allen screws are bored too deep. There is only 2mm left at the bottom. The last picture shows on the right side how it would look when the hole was drilled as deep as it should be. If so there is 6mm material left at the bottom. The left side shows how deep the holes are drilled truly. They need not to be drilled as deep because that makes the clamps weak at the bottom so that they bent and crack.

Pedal_Arm Play.wmv

It sure looks like your pedal arm top part is faulty. None of mine look anything like that.

[Scatcat]

15 hours ago, Scatcat said:

It sure looks like your pedal arm top part is faulty. None of mine look anything like that.

And just for the record, I withdraw my suggestion that a couple of washers would solve the problem. The distorsion and cracking means a new part is needed.

For Yi Chen, it would probably be enough to send a picture of the distorted and cracked part and say something like:

"The part in the picture is damaged and the pedal arm cannot be tightened enough to avoid play. That is probably the reason for much of my problems."

You can count on him pushing the information back up to the manufacturer, they have worked together for a long time.

[cbgti]

Just to be clear : Is this a "washer" ?

It's the upper part of the pedal arms? 

 

 

Rockwheel has the same system than Kingsong for the junction axle/pedal arm ?
I thaught that it was like Gotway (with shims)...

 

[Scatcat]

1 hour ago, cbgti said:

Just to be clear : Is this a "washer" ?

It's the upper part of the pedal arms? 

 

 

Rockwheel has the same system than Kingsong for the junction axle/pedal arm ?
I thaught that it was like Gotway (with shims)...

 

Correct me if I'm wrong, but Gotway to my knowledge has a one piece arm that is secured with a nut. The problems they've had is that the nut has lacked thread-locking, and so have loosened by vibrations. But even so, it is an inherently better system, that uses a single block to support the weight, instead of an upper and lower part.

And no, that is not a washer

A washer is a ring to put around the bolt, and the reason for my suggestion was that the hole was too deep. But if you look at the part, you see it has deformed and cracked, which is very bad. Part of the problem is that they use to heavy moment to make sure the screws are tight, and when you go over a certain pressure, the material bends and cracks.

While this is not an immediate danger, there is the potential of the crack widening eventually, and then the shit might really hit the fan... I noticed small deformations in my old pedal arms, that I just changed. They were tightened hard enough that I had to use a high leverage tool to get them loose. I actually bought a special rather expensive allen-bit, to make sure it didn't deform as I put my weight on the lever.  If you have to screw it on that hard, the manufacturer should consider another solution.

I discussed this with Yi Chen the other day, and he said that he have already brought this to the attention of Rockwheel, since he's seen a few cases of cracks happening. But the problem is much more prevalent in the west than in China, probably because we're on average heavier than the typical Chinese rider.

Note to self. If I ever design a EUC:

• Large diameter shafts.
• One piece pedal arms.
• Nice large pedals that provide real grip and relaxed foot positioning.
• No thread the needle cabling that are partly open to the elements!
• Large gauge cables overall.
• Redundancy wherever possible.
• IP65 as a minimum, preferably better - the ideal would be to make it submersible for at least 30 seconds or so.
• A shell that can take some real beating.
• Enough spacing between shell and wheel to avoid having every stone and debris sound like the whole thing is coming apart.
• Wiiiide tyre, 3" to 4".
• A motor with 50% more power than ever needed.
• Think through serviceability, to minimise the hassle of taking the wheel apart or changing parts.
• Spark protection in charging plugs and power leads.

Did I forget something?

[Blackmagicman]

It is the upper part of the pedal arm. When You look to the video you can see the pedal arm fixed together at the axle.I don´t know the system of king song and gotway.

Actually I am busy with building new clamps / upper parts without the mistake of the too deep drilled holes and additionally I will make them of steel instead of aluminium.

[meepmeepmayer]

24 minutes ago, Scatcat said:

Did I forget something?

Fully agree with you, but while we're at it...

24 minutes ago, Scatcat said:

 

• Large diameter shafts. No axle, because it's not necessary. Simple an open motor with lots of extra space for board, cables or whatever in the motor.
• One piece pedal arms.
• Nice large pedals that provide real grip and relaxed foot positioning.
• No thread the needle cabling that are partly open to the elements!
• Large Huge gauge cables overall.
• Redundancy wherever possible.
• IP65 as a minimum, preferably better - the ideal would be to make it submersible for at least 30 seconds or so. Why not make it completely watertight? Not sure if it would be much more effort than 30s watertight. Creek crossings on EUCs, here we come.
• A shell that can take some real beating.
• Enough spacing between shell and wheel to avoid having every stone and debris sound like the whole thing is coming apart. !!!!!!!!!!!!!!!
• Wiiiide tyre, 3" to 4". !!!!!!!!!!!!!!!!!!!!!!!!!!! Nice offroad tire like on a mountainbike or dirt bike. Does not have to be wide for width's sake though.
• A motor with 50% 100% more power than ever needed.
• Think through serviceability, to minimise the hassle of taking the wheel apart or changing parts.
• Spark protection in charging plugs and power leads.
• Pedal suspension and more ergonomic pedals.
• Traffic brightness front and back light, with different brightnesses from barely visible (for those lonely night forest rides) to "riding on a car road at night in horrible weather and must be seen". Freely variable color would be a plus.
• App that isn't easily beaten by third party offerings.
• Ride modes from super soft to hard as a rock.
• Big, fat batteries. 2000 Wh, 3000 Wh, 4000 Wh, ...

I'm sure we could come up with more, given more time and thought

[Scatcat]

2 hours ago, Blackmagicman said:

It is the upper part of the pedal arm. When You look to the video you can see the pedal arm fixed together at the axle.I don´t know the system of king song and gotway.

Actually I am busy with building new clamps / upper parts without the mistake of the too deep drilled holes and additionally I will make them of steel instead of aluminium.

1) Yes I know

2) That sounds like a very good choice.

[Scatcat]

4 hours ago, meepmeepmayer said:

Fully agree with you, but while we're at it...

I'm sure we could come up with more, given more time and thought

Shafts, pedals, and pedal arms

An open wheel solution is technically superb, but might introduce higher cost. The main goal here is providing enough space for heavy duty wires, and still provide enough strength to allow a heavy rider in the 120-140kg max weight range to use the wheel with absolute confidence. Same thing about pedal arms and coupling, and big ergonomic pedals. High strength and reliability coupled with natural stance and good grip. No worries about curbs, bumps, an terrain riding just because you're bigger than average. Suspension is a nice idea, as long as it is stiff enough and well enough engineered to not affect stability negatively.

Batteries, charging, cables, board and motor-power

Batteries should provide voltages high enough to straighten the torque curve. 30 cells in series provide 126V which makes a lot of sense - IF the rest of the circuit are designed to handle it. That means a board that can handle high voltage and a motor that can do likewise. Cabling and electrical design should be good enough to avoid problems with higher voltages. That also means connectors designed for the purpose, including charging ports - and spark protection, polar reversal protection and so on built in. Battery packs of 30 in series and 4 in parallel should provide 2500 Wh, more with more parallel packs. Cables should be fatter than actually needed, to avoid any tendency to overheat even under emergency power. Boards should have redundancy built in: Triple the gyros to avoid problems if one gyro fails. 12 MOS-FET is good, but should be separated into two discrete power circuits. If one set fails the other can take the brunt. This also means using larger MOS, like in GT16, to make each circuit capable of handling the energy without burning out. A self check should warn if the circuit is not A OK. You should still be able to drive home, but with periodical warnings.

The board should have a hefty heatsink, that is cooled from the outside. Heat pipes from known potential hot-spots can be connected to the sink to keep everything at reasonable temperatures.

The motor should be a lot stronger than currently. Even the GT16 with 2kW is in the lower range of what's acceptable. You should be able to run up a 40-50% incline without being afraid of a cut-out. A power break should only be limited by how much power you as a rider can handle, not how much power the wheel can handle. Acceleration is sometimes the only thing that keeps a rider out of dangerous situations - so for that too, more power is good. Lastly power, and the torque left when we run at cruising speed are the thing that saves us if there's a hidden pot-hole or other bump in the road.

Since more voltage and more power means higher maximum speeds, a reasonable trade-off is setting the top limit for speed-alarms and tilt-back at a point where at least 15-20% of the torque remains. That speed will still be significantly higher than now, so it is time to stop hunting the speed-limit-just-before-cut-out.

Shell- and interior design

The internal layout should be as simple as possible to make service as simple as possible. All wires should have simple runs without small holes to thread them through or compartments with connectors with too tight a fit to reach safely with your fingers.

No wires should be free to the elements and all compartments should be watertight, basically to a level where the wheel can be totally submerged for a time without water leaking in. All external connectors should be protected from water and dust.

The shell should be strong and stiff enough not to warp with asymmetrical weight, and strong enough to be able to take some falls.

Space between wheel and shell should be large enough to allow gravel and small debris to pass through without issues, and the inside of the wheel well should be smooth enough that no debris sticks to it.

The coupling of the wheel and pedal assembly to the shell should not rely on supertight squeezing of the pedal arms into recesses in the shell. Those are debris traps and creates problems when you have a flat and need to take the wheel off. A better idea is a smaller recess for stability combined with enough metal bracket backed screws to provide a strong and safe coupling.

Air ducts to provide cooling for the heatsink is a great idea and should be present, but should not provide a way for water to reach the internals.

Tyre, externals and interface

The tyre should be a lot wider than currently. A wider tyre provides a better cushion, and depending on the geometry it can be just as agile and energy efficient as a thinner variant. It helps in terrain, over curbs or down curbs, lessens the difficulty of cracks and pot-holes and make riding more stable, smoother and with better, less twitchy control.

Ports should have covers that are dependable and simple to use. There should be simple controls for turning the wheel on and off, without a risk of doing it involuntarily. A power-cut should be placed in the handle to be able to lift the EUC without turning it off.

Easily viewable LEDs for power levels are a must.

A strong headlight with modes for visibility (blinking light), medium brightness and high brightness would be very good. Giving the option of running safely in darkness and visibility in bad weather on roads with other drivers.

Side LEDs or night reflective surfaces helps with safety.

Ride modes should span from springy soft to very hard and aggressive.

The applications should not be an afterthought, but should provide controls for how the wheel works, how the alarms are set, and a power lock for motor power. Information should be viewable about temperatures, voltage, amperage, battery levels and health, percentage of max-power, current distance, total distance, and statistics for each ride saveable to be reviewed later. The application interface should not be made to look "cool" but should be designed for maximum clarity.

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We can always come up with more...