Gotway MCM4 HS 680WH, purchased at 09May 2016 - range and speed test

[Belly laughing]

I tested the speed, range along mountain road in S. Korea.

What I found is the range is highly dependent on amount of hills, rider's weight, speed of wind, especially the speed of the wheel and acceleration

My weight: 67 kg

Model used: Gotway MCM4 HS 680WH, 2016 version

 

I hope you to know that in each ride I tried my best effort to maintain the speed in narrow range

(1) 1st picture:

range traveled: 18.7 km 

duration: 1hour 11 min

the number of hill: lots of hills ( more than 200 hills)

battery consumed: 40%

the speed range when I saw on iPhone app: 28km/h - 33 km/h 

acceleration: hard ( I tried to catch up cycles, cars. all cycles were gotten past.)

wind: strong headwind ( up to being able to keep my eyes opening)

calculated range: 46.8 km = 29.08 miles

 

(2) 2nd picture

range traveled: 16.6 km 

duration: 1hour 31 min

the number of hill: lots of hills ( more than 200 hills)

battery consumed: 30%

the speed range when I saw on iPhone app: 33km/h - 38 km/h 

acceleration: hard  ( I tried to catch up cycles, cars. all cycles were gotten past.)

wind: strong headwind (weaker than above)

calculated range: 55.3 km = 34.4 miles

 

(3) 3rd picture

range traveled: 21.7 km 

duration: 1hour 49 min

the number of hill: some of hills ( about small 20 hills and large 10 hills)

battery consumed: 30%

the speed range when I saw on iPhone app: 20km/h - 25 km/h 

acceleration: moderate 

wind: no headwind

calculated range: 72.4 km = 45.0 miles

 

Because I could not record all ranges by the cycling app I have traveled, I can not say the above is precise.

However, based on several measurement of distance (calculated on gps map) when I almost used up the battery ( until 20% left ),

I can tell that the above calculation is roughly correct.

How about the ranges of your MCM4 or KC16, KC14?

 

PS. I heard 3rd warning alarm around 35-38km/h (21.8-23.6mph) from my MCM HS when the battery is between 80-100%   Is it normal?

 

[The Fat Unicyclist]

Wind, weight, speed and hills... Always the biggest factors.

And always so different from the manufacturer tests (performed in an enclosed space, on a polished and leveled floor, at half speed, with a featherweight jockey).

It would be interesting to see some real world comparisons with just one factor changed...

• Same course / wind, different speed. 
• Same course / speed, different wind. 
• Same distances, different inclines. 

And so on...

[WakefulTraveller]

It appears that the range drops significantly when going at top speed; the most efficient speed is probably around 25 km/h. I myself rode the MCM4 HS 680WH a distance of 9 miles going close to top speed most of the way, and the battery dropped from around 90% to 50%. I wonder if this large drop is due to the inefficiency of the motor at top speed, or if it's due to the actual current needed to maintain those high speeds.

As for speed, with my weight being a little more than yours, I've only been able to get around 18mph at top speed. Whereas, I'm able to get 19mph on my MCM3 (that only has one battery pack). I believe that this ~1mph difference could be due to how I have the weight distributed on the EUC (the placement of the battery packs and the trolley handle), and the angle that I have the horizontal alignment set to, making the EUC more prone to wobble back and forth. 

[Belly laughing]

I totally agree the opinion with WakefulTraveller about top speed in heavily affecting range of the wheel.

The most strange thing I noticed is that the speed on iPhone app is bloated a lot.

When it is indicating 25km/h(15.5mph), I feel like 20km/h(12.4mph).

Even when I reached almost the limit– I couldn't test more than this being afraid of unexpected, precarious cut-off – which is 36-38km/h(22.3-23.6mph), it felt like going at 31-32km/h(19.5-19.9mph).

[Mono]

On 5/28/2016 at 9:17 PM, WakefulTraveller said:

the most efficient speed is probably around 25 km/h

How do you figure this? I would think it should be considerably lower.

[WakefulTraveller]

18 hours ago, Niko said:

How do you figure this? I would think it should be considerably lower.

I suppose that it depends on how much you accelerate, stop, or slow down, and whether you're riding on a windy day or not, and other conditions, but I do believe the optimal speed is fairly high. Someone here did a test to find the optimal speeds, and that's what I'm basing my guesstimate on. 

[Jurgen]

@WakefulTraveller mass has less impact than speed; slower is more efficient, the kinetic energy equation, says it all: E_k = ½mv²

[WakefulTraveller]

Just now, Jurgen said:

@WakefulTraveller mass has less impact than speed; slower is more efficient, the kinetic energy equation, says it all: E_k = ½mv²

Keep in mind that the electric unicycle is constantly balancing the rider, which requires a lot of torque. To go the same distance but slower will make the EUC have to do more work to keep you upright. The optimal speed is certainly not at < 10 km/h.

[Mono]

1 minute ago, WakefulTraveller said:

The optimal speed is certainly not at < 10 km/h.

How do you know? 

[WakefulTraveller]

7 minutes ago, Niko said:

How do you know? 

Here is an example with Tesla cars:

As you can see the speed when it is most efficient is between 10 and 30 mph with the roadster and between 15 and 35 for the Tesla.

While this is a poor comparison for a number of reasons, it goes to show that slower isn't always better. 

[Mono]

21 minutes ago, WakefulTraveller said:

Keep in mind that the electric unicycle is constantly balancing the rider, which requires a lot of torque.

What does "a lot" mean, and how do you know that the energy needed for balancing does not depend on speed? I have been taught that it does.

[Jurgen]

4 minutes ago, WakefulTraveller said:

Keep in mind that the electric unicycle is constantly balancing the rider, which requires a lot of torque. To go the same distance but slower will make the EUC have to do more work to keep you upright. The optimal speed is certainly not at < 10 km/h.

good point, if you manouever a lot at low speed ( back forth etc) this will of course drain the batt rapidly; A big guy going slow could drain more that a light guy going faster, butspeed has an exponential effect so it should kick in rather quickly.

[Mono]

16 hours ago, WakefulTraveller said:

Here is an example with Tesla cars:

As you can see the speed when it is most efficient is between 10 and 30 mph. 

While this is a poor comparison for a number of reasons, it goes to show that slower isn't always better. 

Scaling this graph down to a 1kW machine with 20mph max speed and minimum consumption of about 20Wh/mile, I wouldn't be at all sure that the most efficient speed of an EUC is above 5mph.

The data in this thread

suggested that the most efficient speed is <= 15km/h.

One last number: air drag is probably somewhat above 15W at 15km/h and 70W at 25km/h, that is somewhat above 1Wh/km and 3Wh/km, respectively.^1 Consequently, below 10km/h drag should only have a marginal influence.

^1 http://www.gribble.org/cycling/power_v_speed.html 

[WakefulTraveller]

25 minutes ago, Niko said:

Scaling this graph down to a 1kW machine with 20mph max speed, I wouldn't be at all sure that the most efficient speed is above 5mph.

The motor on an EUC doesn't just become less efficient at higher speeds. In other words, if you placed a new motor capable of higher speeds into an EUC, the efficiency would be about the same, if not less, at the same speeds, except for perhaps at top speed of the original motor. However higher speeds do result in significant energy loss because of poor conversion and heat and whatnot, and I'm certain that Tesla cars are more capable of managing these variables, thereby making them more efficient at higher speeds.

[Mono]

7 minutes ago, Jurgen said:

good point, if you manouever a lot at low speed ( back forth etc) this will of course drain the batt rapidly

that's for sure, but it doesn't really help to find the most efficient speed. Though I could imagine that an experienced rider will have a markably lower efficient speed, because he can go smoother at low speed.

[Shoe73]

On May 28, 2016 at 0:13 PM, The Fat Unicyclist said:

Wind, weight, speed and hills... Always the biggest factors.

And don't forget tire pressure. I suspect this has a much bigger effect than it gets credit for. 

[The Fat Unicyclist]

2 hours ago, Shoe73 said:

And don't forget tire pressure. I suspect this has a much bigger effect than it gets credit for. 

Good point! 

And is it just me, or does it seem to others that most EUC lose tyre pressure quite quickly?

This is something I would like to resolve. 

[esaj]

4 minutes ago, The Fat Unicyclist said:

Good point! 

And is it just me, or does it seem to others that most EUC lose tyre pressure quite quickly?

This is something I would like to resolve. 

I checked the pressure maybe once a month last summer, while it usually had gotten lower, it didn't go really low (don't remember exact numbers, though). Probably related to how much the rider weighs, how high pressure you usually use (I'd imagine higher pressure drops faster) & valve quality...

[Mono]

21 minutes ago, esaj said:

I checked the pressure maybe once a month last summer, while it usually had gotten lower, it didn't go really low (don't remember exact numbers, though). Probably related to how much the rider weighs, how high pressure you usually use (I'd imagine higher pressure drops faster) & valve quality...

The weird thing I observed consistently with bicycle tires: when I was riding daily, I rarely needed to add air (maybe twice a year or so). When I didn't ride, the air was gone within a few weeks. I suspect that moving the tubes keeps them softer and airtight.

[esaj]

1 minute ago, Niko said:

The weird thing I observed consistently with bicycle tires: when I was riding daily, I rarely needed to add air (maybe twice a year or so). When I didn't ride, the air was gone within a few weeks. I suspect that moving the tubes keeps them softer and airtight.

Could be, I haven't actually checked how much lower the pressure has gotten over the winter (especially since the motor & tire were in a cold garage over the winter)

[Belly laughing]

9 hours ago, Niko said:

The weird thing I observed consistently with bicycle tires: when I was riding daily, I rarely needed to add air (maybe twice a year or so). When I didn't ride, the air was gone within a few weeks. I suspect that moving the tubes keeps them softer and airtight.

@Niko Yeah I felt the same with you.  The tube silant 'Slime' could help you in this sense if you also care about flat tire as well.  It also helps to make tire tightly sealed.  I hope it would work for you. 

[Jurgen]

@The Fat Unicyclist

I have the same impression.

I guess small tire = less air; using the same valve as on a big tire at the same pressure, the small  tire deflates more rapidly (leak flow rate remains the same)?

I'm not a specialist on tire valves, so I might be overlooking something here.

[Belly laughing]

On September 24, 2015 at 11:40 PM, Daan said:

Whaa -- thanks for all your help!  but I wish you could be more clear about how the alarms work  and how they sound; I think this is what you are trying to say:

level 1:  happens at 23 km/hr
level 2: happens at 25km/hr
level 3: happens at 28km/hr, cannot turn this off
level 4: happens at 30km/hr, cannot turn this off -- you should stop speeding at this point for safety
level 5: happens at emergency situation: low battery, too much battery draw (hill too steep, too fast), too much battery recharge (going downhill on full battery) etc.

Is this correct???

Can you perhaps also say how the different alarms sound? Does each have a different sound?

Can you also confirm that the level 5 emergency alarm also happens on low battery, or when going downhill on a full battery? (i.e. not just when going too fast)

 

 

 

I bought Goway MCM4 HS 680Wh on 09May2016.

1st alarm starts at 23 kph ( GPS 19kph), going off double beeps

2nd at 25 kph (GPS 21kph), triple beeps

3rd at 35 kph based on app speed. (GPS 34 kph), continuous beeps.

Is it normal?

I had no problem or crash until I pushed it to 38kph so far: I have tested this over 300km.

 Very weird...

[mhpr262]

On 31.5.2016 at 9:28 PM, Jurgen said:

@WakefulTraveller mass has less impact than speed; slower is more efficient, the kinetic energy equation, says it all: E_k = ½mv²

Kinetic energy has nothing at all to do with energy consumption, especially not when travelling at a steady pace. It is wind drag that is responsible, especially with the extremely un-aerodynamic position one assumes on a wheel.

That diagram from the Tesla just proves that electric motors definitely have a sweet efficiency spot as far as rpms are concerned. My experience with electrically powered RC models supports this - some motors, especially the modern brushless ones can get hot or even burn out when underloaded as as easily as when overloaded. The culprit are the eddy currents. The slower the better is definitely wrong.

That is, however, a totally different can of worms than the question of how much energy is wasted for additional balancing when going a medium speed that is optimal for the motr versus higher speed at lower efficiency but less balancing needed because you don't ride as long.

[Jurgen]

5 hours ago, mhpr262 said:

Kinetic energy has nothing at all to do with energy consumption, especially not when travelling at a steady pace. It is wind drag that is responsible, especially with the extremely un-aerodynamic position one assumes on a wheel.

That diagram from the Tesla just proves that electric motors definitely have a sweet efficiency spot as far as rpms are concerned. My experience with electrically powered RC models supports this - some motors, especially the modern brushless ones can get hot or even burn out when underloaded as as easily as when overloaded. The culprit are the eddy currents. The slower the better is definitely wrong.

That is, however, a totally different can of worms than the question of how much energy is wasted for additional balancing when going a medium speed that is optimal for the motr versus higher speed at lower efficiency but less balancing needed because you don't ride as long.

Thanks, you are right about the equation not being appropriate for the point; at a steady pace on a perfectly smooth surface, it's just the wind and wind drag.

The faster you go however, the more wind drag you get, so slower is more economical.

Also, the steady pace is far from steady on real roads, EUCs don't have cruise control and it's a constant balancing act (with weight probably having an important effect), so as you pointed out finding the 'sweet spot' for an EUC is not so easy as there are a lot of variables.