My Sherman Trials, Tribulations, and Triumphs

[Marty Backe]

15 minutes ago, erk1024 said:

So a successful result would be that the board safely detects that it's overheating and goes into tiltback, right? Doesn't seem like a firmware fix will add more torque to the motor.

I'll know when I start riding with the new board, but I suspect that the power delivery will not be improved. From the one cryptic message I received, I believe the primary update is better heat monitoring.

Personally, I'd be satisfied if the wheel tilted-back and kicked me off the wheel as I was climbing instead of burning up. The Sherman is my dream come true for cruising and flattish off-road riding. It's not a wheel of technical off-road riding, IMO.

[Marty Backe]

30 minutes ago, Gadgetfann said:

All of us who have preordered sincerely appreciate the time and effort you’re putting forth to help make the Sherman a better, more reliable wheel.  I would have surely cancelled my pre-order and waited for one of the new Gotway wheels if not for your endorsement of this wheel, testing and ongoing feedback.  If one of these control boards results in a successful overheat hill test you’re going to make hundreds of us breathe a sigh of relief and feel better about spending our hard earned money.  We all owe you a debt of gratitude. 👍👍

There are substantive changes being made subsequent to my test failure. I can't say anything until after another test but everyone getting their Sherman from EWheels will benefit for sure.

[erk1024]

5 minutes ago, Marty Backe said:

I'll know when I start riding with the new board, but I suspect that the power delivery will not be improved. From the one cryptic message I received, I believe the primary update is better heat monitoring.

That's what I was thinking as well. Maybe they can squeeze a little more out of the motor? But a new controller and firmware fix is not going to add windings to the electromagnets, or make the magnets wider, or change the motor's heat dissipation, etc. Seems like there is a tradeoff between torque and top speed in motor design? (I know zero about electric motors.) It's fine to have different wheels for different use cases.

[meepmeepmayer]

In that second Sherman kill video, it fries after like 10 seconds on a very steep test hill. What temperature sensor is going to engage before it's too late there?

[Paradox]

When a wheel is pushed outside its design limits and fails it is not a problem with the wheel.  Its a problem with the test.  Yes, its great when a wheel performs well outside its design limit.  I am sure if you use this wheel within its capabilities it will be the best wheel you have ever owned.  The failure here was the wheel not sensing a higher current draw and heat buildup than it was designed for.   The heat buildup was unavoidable. It should have cut off before things started failing. 

Edited July 24, 2020 by Paradoxedgewater

[Alj]

15 hours ago, Esbu said:

About cooling and heat removal, I am asking myself, why EUC engineers are not inspired by heatpipe cooling mechanism.

 

Pipes solve a problem where you have heat source in one place and heat sink in completely different place (due to form factor limitation) which is completely not an issue here.

Here we have heat source directly attached to the heat sink (via poor silicone insulation coupling) and any additional layers such as heat pipes will make things only worse.

[Alj]

15 hours ago, Esbu said:

If it's just a piece of aluminum touching the chip, it looks like that piece of aluminum is right next to that temperature chip and acts as a "temperature flywheel". But I'm not sure.

Its not. This is one leg of the voltage regulator chip (like LM317 or similar). It has big size to transfer heat from the chip to the PCB board.  Given that there is OSCON cap and inductor next to it you probably looking at the buck converter circuitry.

 

Look up "SOT-223" on google images - its a standard chip enclosure used mostly for voltage regulators.

Edited July 24, 2020 by Alj
Typo.

[Alj]

1 hour ago, Paradoxedgewater said:

When a wheel is pushed outside its design limits and fails it is not a problem with the wheel.  Its a problem with the test.  Yes, its great when a wheel performs well outside its design limit.  I am sure if you use this wheel within its capabilities it will be the best wheel you have ever owned.  The failure here was the wheel not sensing a higher current draw and heat buildup than it was designed for.   The heat buildup was unavoidable. It should have cut off before things started failing. 

If that would be the case with the cars you car would explode if you press gas pedal too far to the floor when you climb hill. And there would be warning signs on the dashboard  such as "please do not press gass more than 90%, please do not accelerate to 100kmh if you water temperature is above 70% but you can accelerate to 120 if you water temp is above 50% and avoid breaking if you  rotors are hotter than 200C."  However you do not see those warnings because car is designed with bottlenecks in manageable places.

It is totally problem of the wheel. The wheel should not produce magic smoke no matter what used does. It is 100% problem of schematic design and software. "shut down" is too radical imo, there are softer ways of flow control such as slight tilting to limit max speed, make pedal angle "uncomfortable" for further acceleration which is about to push wheel to the limit.

[Mrd777]

3 hours ago, Gadgetfann said:

If Veteran can accomplish what Jason mentioned in his latest email about the Sherman, I’d consider Marty’s test successful.  Quote from the email... “Veteran is working on improving the firmware/controller combination in order to be capable of tackling the most grueling inclines without self-immolation.”

Yes, this is great but no mention of insulating the phase wires which seems imperative. I’m on the first batch, and hoping these improvements were made before shipping.

[Esbu]

1 hour ago, Alj said:

If that would be the case with the cars you car would explode if you press gas pedal too far to the floor when you climb hill. And there would be warning signs on the dashboard  such as "please do not press gass more than 90%, please do not accelerate to 100kmh if you water temperature is above 70% but you can accelerate to 120 if you water temp is above 50% and avoid breaking if you  rotors are hotter than 200C."  However you do not see those warnings because car is designed with bottlenecks in manageable places.

It is totally problem of the wheel. The wheel should not produce magic smoke no matter what used does. It is 100% problem of schematic design and software. "shut down" is too radical imo, there are softer ways of flow control such as slight tilting to limit max speed, make pedal angle "uncomfortable" for further acceleration which is about to push wheel to the limit.

If you drive up your car a steep hill very slowly at full throttle and your car radiator fan does not work, the temperature will rise and you will seize the pistons. This is proof that the most fundamental problem is cooling.

Back to Veteran Sherman.

The exposed mosfets are mounted too close to the edge of the heatsink. There should still be a piece of heatsink next to them, for better heat dissipation. The fans blow on the circuit board, but all the heat accumulates inside and there is no way to leave. Shifting the circuit board on the heatsink could be a partial solution for better cooling of exposed heatsinks mosfets. Next, I would put one fan in the front of the heatsink to blow through the heatsink. This should solve the problem: "the slower I ride, the less it will cool".

The main problem is how to remove heat as quickly as possible.

Edited July 24, 2020 by Esbu

[Marty Backe]

18 minutes ago, Mrd777 said:

Yes, this is great but no mention of insulating the phase wires which seems imperative. I’m on the first batch, and hoping these improvements were made before shipping.

Wait to you see my rebuild video. Rest assured, your worries will be unwarranted 

[Esbu]

1 hour ago, Alj said:

Look up "SOT-223" on google images - its a standard chip enclosure used mostly for voltage regulators.

Thanks for the explanation. I have never seen such a part before.

[Marty Backe]

1 minute ago, Esbu said:

If you drive up your car a steep hill very slowly at full throttle and your car radiator fan does not work, the temperature will rise and you will seize the pistons. This is proof that the most fundamental problem is cooling.

Back to Veteran Sherman.

The exposed mosfets are mounted too close to the edge of the heatsink. There should still be a piece of heatsink next to them, for better heat dissipation. The fans blow on the circuit board, but all the heat accumulates inside and there is no way to leave. Shifting the circuit board on the heatsink could be a partial solution for better cooling of exposed heatsinks. Next, I would put one fan in the front of the heatsink to blow through the heatsink. This should solve the problem: "the slower I ride, the less it will cool".

The main problem is how to remove heat as quickly as possible.

I'm not convinced that the problem was with the MOSFET's. Based on the extensive heat damage in the area where the power is flowing into the board, I believe the root cause of the failure was too much current (heat) flowing into the control board from the batteries. I do agree with your last sentence.

[mrelwood]

2 hours ago, Paradoxedgewater said:

When a wheel is pushed outside its design limits and fails it is not a problem with the wheel.  Its a problem with the test.

To me that sounds just like “look what you made me do!” as means to redirect the blame. No, if the user can dematerialize a vehicle equipped with an off-road tire by calmly riding off-road, it’s a badly designed product. The “design limits” have not been said excluding Marty’s overheat hill, quite the opposite, Marty was asked to stress the wheel. It’s absurd to expect that the rider would have to know the temperatures inside the wheel at all times when even the manufacturer is not capable of monitoring them closely enough. And it is well known that almost every other current wheel can manage the overhead hill just fine, either by riding all the way or forcing the rider off due to overheating. It’s not at all an unrealistic expectation from a current top-of-the-line EUC.

2 hours ago, Paradoxedgewater said:

Yes, its great when a wheel performs well outside its design limit.

It’s crucial that the wheel is capable of monitoring itself and at least warn the rider when the wheel is being used outside its design limits.

2 hours ago, Paradoxedgewater said:

The heat buildup was unavoidable.

It isn’t for many other wheels, why is it for the Sherman? Because of bad design.

2 hours ago, Paradoxedgewater said:

It should have cut off before things started failing. 

So you agree, the Sherman didn’t behave as it was expected?

[Esbu]

1 minute ago, Marty Backe said:

I'm not convinced that the problem was with the MOSFET's. Based on the extensive heat damage in the area where the power is flowing into the board, I believe the root cause of the failure was too much current (heat) flowing into the control board from the batteries. I do agree with your last sentence.

This is well known from your video. But the cables and the circuit board must have become very hot before melting. And most of all, the cables were burned closest to the circuit board. I think passive cooling is a very undersized and active cooling stupidly designed. If the heat does not build up and is removed from the circuit board quickly enough, the tin on the connections may not melt.

[Esbu]

20 minutes ago, mrelwood said:

It’s crucial that the wheel is capable of monitoring itself and at least warn the rider when the wheel is being used outside its design limits.

Pure truth.

[Alj]

36 minutes ago, Esbu said:

If you drive up your car a steep hill very slowly at full throttle and your car radiator fan does not work, the temperature will rise and you will seize the pistons. This is proof that the most fundamental problem is cooling.
 

First you get a warning on the temperature gauge. Then it will take awhile (probably an hour) for coolant to boil away before you seize the pistong. It is totally not an issue because i do not know a single person who would have experienced that.

[Alj]

35 minutes ago, Marty Backe said:

I'm not convinced that the problem was with the MOSFET's. Based on the extensive heat damage in the area where the power is flowing into the board, I believe the root cause of the failure was too much current (heat) flowing into the control board from the batteries. I do agree with your last sentence.

If controller did not shut down then the current was not excessive. Too much would cause voltage drop and controller shutdown.

The controller is intended to deliver as much current as battery can provide to the motor and that is what it was doing otherwise there is no reason to go bonkers with 100V battery voltage and beefy battery pack if you not going to use a half of it.

[Seba]

22 hours ago, Marty Backe said:

Does anyone know what the temperature sensor looks like that they probably use to monitor the board temperature? Can you spot it on this board and if so, where is it? My previous board disintegrated (heat damage) in the upper left section of the board.

Well, Veteran is using the same approach as Gotway - there is no dedicated temperature sensor. Instead, they just read temperature of MPU6050 IMU chip (the "gyro chip") that is located just below Bluetooth module (see picture below). Gotway and Veteran doesn't really measure MOSFET or heatsink temperature, but mainboard temperature. This is why both wheels may seem a "cool running wheels", but this is misleading. Veteran cooling is better than in Gotways, because Veteran is using two centrifugal fans blowing directly at MOSFETs. In case of Gotways, there is just an ordinary axial fan that is mostly blowing onto the top of mainboard, cooling IMU sensor in first place (actually this is why fan in some Gotways repeatedly turns on and off in a rapid succession). This leads to make mainboard cool quickly while the MOSFETs may be near to overheating. Using IMU temperature sensor isn't a sufficient to maintaing proper thermal management. 

For example King Song are using separate probe that is located close to the most hottest MOSFET (the one far away from cooling fan). Another example is a Ninebot One S2 that have a separate temperature probe that is attached to the heatsink.

[Esbu]

2 minutes ago, Alj said:

First you get a warning on the temperature gauge. Then it will take awhile (probably an hour) for coolant to boil away before you seize the pistong. It is totally not an issue because i do not know a single person who would have experienced that.

I think we're both talking about the same thing. In comparison to the car, I intentionally omitted the temperature warning against seizing the pistons - just as Sherman does not have such a mechanism.

Whether it's a car or a unicycle, every product should be protected from self-destruction by heavy use.

[Esbu]

1 minute ago, Seba said:

Veteran cooling is better than in Gotways, because Veteran is using two centrifugal fans blowing directly at MOSFETs.

The difference in cooling quality is not in the fans, but mainly in the fact that the Gotway exposes the heatsink through the body to the wheel. That's another thing I want my Sherman to have.

[Alj]

4 minutes ago, Esbu said:

I think we're both talking about the same thing. In comparison to the car, I intentionally omitted the temperature warning against seizing the pistons - just as Sherman does not have such a mechanism.

Whether it's a car or a unicycle, every product should be protected from self-destruction by heavy use.

I'm not comfortable with "heavy use" therm here. It assumes those "warnings on the dashboard". The user should be able to do anything. Its a human factor, you cannot control it. Well. of course if used decides to throw wheel from the cliff that is obviously user fault. But wheel should limit what user can do in order to save itself. Yes alarm as last resort.   But first we can start tilting pedals to avoid further acceleration. If user decides to climb overheat hill that is not "heavy use" if you do it with sane speed to allow wheel to cool off. It, however, becomes "heavy use" if you do not have such mechanisms in place.

[Marty Backe]

12 minutes ago, Seba said:

Well, Veteran is using the same approach as Gotway - there is no dedicated temperature sensor. Instead, they just read temperature of MPU6050 IMU chip (the "gyro chip") that is located just below Bluetooth module (see picture below). Gotway and Veteran doesn't really measure MOSFET or heatsink temperature, but mainboard temperature. This is why both wheels may seem a "cool running wheels", but this is misleading. Veteran cooling is better than in Gotways, because Veteran is using two centrifugal fans blowing directly at MOSFETs. In case of Gotways, there is just an ordinary axial fan that is mostly blowing onto the top of mainboard, cooling IMU sensor in first place (actually this is why fan in some Gotways repeatedly turns on and off in a rapid succession). This leads to make mainboard cool quickly while the MOSFETs may be near to overheating. Using IMU temperature sensor isn't a sufficient to maintaing proper thermal management. 

For example King Song are using separate probe that is located close to the most hottest MOSFET (the one far away from cooling fan). Another example is a Ninebot One S2 that have a separate temperature probe that is attached to the heatsink.

Great info. Thanks. So to be semi-effective they would probably have to add a bias to whatever temperature they read from the IMU. Hopefully they are doing something along those lines.

P.s. You have very good vision to be able to see through that Bluetooth board 

Edited July 24, 2020 by Marty Backe

[Esbu]

If anyone from Veteran reads this, contact me, I will help you design a much more efficient cooling. I have experience with cooling overclocked processors with air coolers with minimal modifications. My Intel Core i5 Sandy bridge can run at 5.3GHz and handle all benchmark stress tests.

[Marty Backe]

1 minute ago, Esbu said:

If anyone from Veteran reads this, contact me, I will help you design a much more efficient cooling. I have experience with cooling overclocked processors with air coolers with minimal modifications. My Intel Core i5 Sandy bridge can run at 5.3GHz and handle all benchmark stress tests.

Rest assured, nobody associated with Veteran is reading anything said here. And historically they are very insular and have no interest in being told how to improve their design. 

Don't hold your breath