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Marty Backe

My KS18XL Trials, Tribulations, and Failures

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2 hours ago, Marty Backe said:

These are long steep hills that I'm riding. The kind of hills where it's marginal that you have enough power to climb. Is that the kind of riding that you're doing?

I'll have to see if @Rama Douglas would be interested in riding with me on these same trails. Him on his production XL and me on the pre-production XL. Would be very interesting. We are both in the general ballpark, in terms of weight.

Another ride with Rama would be awsome! Its very true that your proving grounds are unmatched, but long steep hills are still long steep hills and mine did not break 70C. I just picked up an XL from @Nevin@Tec-toyz.com and I'll put it though the paces here and report back over the week on any differences in performance on a brand new XL.

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1 hour ago, Michael Tucker said:

Another ride with Rama would be awsome! Its very true that your proving grounds are unmatched, but long steep hills are still long steep hills and mine did not break 70C. I just picked up an XL from @Nevin@Tec-toyz.com and I'll put it though the paces here and report back over the week on any differences in performance on a brand new XL.

Every wheel will eventually overheat. I have overheated or personally seen every Gotway wheel overheat. If you've never seen your XL exceed 70-degrees, than you're not trying hard enough ;)

A long hill will not necessary overheat a wheel, but a long very steep hill will. I believe Overheat hill is steeper and longer than any equivalent hill in San Francisco, although I have not made a study of it.

I will try it again with Rama, hopefully.

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6 hours ago, Marty Backe said:

I do these rides to test the limits of the wheels. They are not meant to represent what most people do (but I do ride my wheels on this trail for pleasure too).

So it can be useful to know how the wheels react when they overheat and what kind of power (and low-speed torque) they have relative to other wheels.

yes @Marty Backe, this is really highly appreciated ! Actually I was expecting some posts/tests from you before I got my KS18L but you was playing with Z10 at that time :-)

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10 hours ago, Marty Backe said:

These are long steep hills that I'm riding. The kind of hills where it's marginal that you have enough power to climb. Is that the kind of riding that you're doing?

I'll have to see if @Rama Douglas would be interested in riding with me on these same trails. Him on his production XL and me on the pre-production XL. Would be very interesting. We are both in the general ballpark, in terms of weight.

The ride I did over Reseda to Will Rogers Park had some very steep sections I was able to do, but I tend to get off and walk, rather than push it too hard up those steeper hills... Without a backe-catalogue 😜 of wheels to fall Backe on, I'm not in any hurry to push my wheel to it's breaking point just yet...😎 

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37 minutes ago, Rama Douglas said:

The ride I did over Reseda to Will Rogers Park had some very steep sections I was able to do, but I tend to get off and walk, rather than push it too hard up those steeper hills... Without a backe-catalogue 😜 of wheels to fall Backe on, I'm not in any hurry to push my wheel to it's breaking point just yet...😎 

The wheels won't break :D I've never had a KingSong wheel fail on me. They just overheat. But I understand.

Calling any other KS18XL owners who live in Southern California :dribble:

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42 minutes ago, Rama Douglas said:

The ride I did over Reseda to Will Rogers Park had some very steep sections I was able to do, but I tend to get off and walk, rather than push it too hard up those steeper hills... Without a backe-catalogue 😜 of wheels to fall Backe on, I'm not in any hurry to push my wheel to it's breaking point just yet...😎 

You don't need to push it to the limit. it would be interesting to see if you get same tempature in same terrain. As long as you have an eye on wheel temp you could stop at any point wait a bit and turn back.

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4 minutes ago, Seba said:

It's absolutely possible to overheat KS-18L/XL by constantly riding up a steep hill. In these wheels heat is dissipated by the forced air moved by the tire inside a wheel cavity. MOSFET's are cooled by the aluminium radiator in form of plate. There is a rectangular hole in the top of the wheel cavity, and PCB assembly is mounted on top of this hole, so it's covered by this metal plate. This is similar idea like in KS-16. This plate is the main way to dissipate heat generated by transistors. This plate is also cooled from above by the centrifugal fan, forcing air to flow between this metal plate and the PCB. This is much less efficient, because there is a very limited air volume inside the board compartment. When air inside this compartment gets hot, effectiveness of cooling will degrade severely. Air inside this compartment also gets hot due to sun radiation (and black color doesn't help...).

 

Image 1 - Top view of the KS-18L/XL controller board. Cooling fan (on left side, below three capacitors) forces air to flow between radiator plate and PCB.

 

Image 2 - Side view of the KS-18L/XL controller board. TO-247 MOSFET transistors are mounted directly to the aluminium plate that works both as a PCB chassis and as a heat radiator. Bottom side of this plate is exposed to the wheel cavity, so it may be cooled by the air forced by rotating wheel.

Due to this design details, there is one important factor that can significantly affect heat dissipation ability. It's mud or dirt, that will stick to the bottom part of the metal plate. And this may be the cause that some wheels overheats easily and other not. This is also hardest part of the unicycle to clean, but you can try my wheel cavity washing method:

https://najednymkole.pl/en/how-to-wash-your-electric-unicycle/

 

There are no significant differences between first, presentation models and latest production units. At least when we talk about board  and wheel thermal design.

Great pictures and commentary :cheers:

And for the record, the plate on my shell is clean (except for road dust/dirt).

Edited by Marty Backe
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4 hours ago, Rama Douglas said:

The ride I did over Reseda to Will Rogers Park had some very steep sections I was able to do, but I tend to get off and walk, rather than push it too hard up those steeper hills... Without a backe-catalogue 😜 of wheels to fall Backe on, I'm not in any hurry to push my wheel to it's breaking point just yet...😎 

Just to be clear for everyone reading here, this isn't about how steep a hill a wheel can do. Pretty much any wheel can do extremely steep hills for a short time. My weak-cabled ACM that would certainly fry on Marty's hill can easily do 100% inclines for a few shorter moments, it definitely has the power to get up there.

This is about continuous power draw. Doesn't matter if that comes from hill incline, rider weight, whatever else. A steep hill can get you a high power draw, but the hill also has to be long enough (minutes of riding up) to make the power draw continuous in a meaningful way.

The questions are:

  • What's the highest continuous power draw that a certain wheel can do permanently (= without overheating or hardware failure, until the battery is empty, and forever with an infinite battery)?
  • For higher continuous power draws than that: How long can the wheel keep up a certain power draw, and what happens then (overheating, or in the worst case hardware damage)?
  • (Thirdly, but not that important: What the highest continuous power draw the wheel can do at all? This is limited by the battery and so crazy high with big batteries that it doesn't matter in practice.)

If I had too much money, I'd buy one of each wheel, and get one of these machines that are used to test a car's or motorcycle's braking strength. A German dealer did something like this with one of @US69's wheels (see here), and some Russians also did a lot of tests like that.

Lock each wheel in there, and simulate different rolling resistances to get arbitrary constant power draws. Then you can answer these questions for every wheel and make a diagram for each wheel how fast it overheats (or dies for extreme stresses, ideally it always overheats or warns first) at different power draws.

We don't have these diagrams, but we've got some isolated data points, for example:

  • @EUC GUY pushed a car with his MSX (extremely high power draw) for about 6 minutes (if I remember correctly) before it fried (motor cables melted from the strong current, didn't even have time to overheat).
  • He also rode up a pretty gnarly steep hill and the MSX overheated after like 13 minutes.
  • Marty rode up the overheat hill with his MSX and it cooly and easily did that. He could probably have continued like this for 3 or 5 times the length.
  • Marty rode up the overheat hill with his 18XL and it overheated after 80 seconds, didn't make it to the top.

(Both riders here are about normal weight and not super light or heavy, so these are quite representative rides.)

The higher the power draw/current is, the less environmental conditions (outside temperature) matter (because the heat can't dissipate fast enough either way) and the more the wheel's electronics' design/construction matters (they must not get hot quickly in the first place).

-

Long story short, the 18XL seems to overheat much faster (if it does overheat, not that easy to achieve) than the MSX. Which is not what I expected, I thought it would be as good.

That's why I'm also wondering about the 16X (and Nikola!) now, if newer wheels aren't automatically better like I hoped.

I was thinking (hoping) the result is due to Marty's 18XL being a earlier prototype model, but after @Seba's comment there don't seem to be many differences that could make this the explanation.

Looking forward to the next test! Maybe switch wheels so we also get Marty behavior on a production wheel.

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13 hours ago, Marty Backe said:

A long hill will not necessary overheat a wheel, but a long very steep hill will. I believe Overheat hill is steeper and longer than any equivalent hill in San Francisco, although I have not made a study of it.

It would be informative to put a "level" App on a representative part of the hill so a better understanding could be reached.  Might stop all the conjecture also.

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7 hours ago, Marty Backe said:

Calling any other KS18XL owners who live in Southern California :dribble:

I'm here but probably lighter and 100+ miles away... As stated earlier I do ride up lots of hills daily, so I might collect some data for a couple weeks and report back.

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2 hours ago, Smoother said:

It would be informative to put a "level" App on a representative part of the hill so a better understanding could be reached.  Might stop all the conjecture also.

I already posted the Google Map information for overheat hill, in the V10F thread. When it overheated people wanted to know more about the hill, how steep it is, etc.

I don't know how useful it really was. As @meepmeepmayer says, it's not the steepness of Overheat Hill that's important, it's that it's long enough to overheat most wheels.

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On 4/14/2019 at 5:28 PM, meepmeepmayer said:

The Inmotion V10 did better overall!

Huh? The V10F couldn't climb anything without over-heating. Over heating on the third of three brutal climbs doesn't concern me as I will never run into such a situation where I live. What does concern me is how it will handle 90+ temperatures this summer when doing 25+ mile rides. I will know in about two months or so. Is a MSX in my future. We shall see.

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