Sherman-S 3600wh: 100V, 20", suspension, 97lb

[RagingGrandpa]

29 minutes ago, meepmeepmayer said:

Glad that Veteran at least is sticking with TO-247 sized mosfets.

Eh, they're not... it's an ewheels typo.

(CAD clearly shows surface-mount components; TO 247 was through-hole)

  It's good tho  

On 9/11/2022 at 4:20 PM, RagingGrandpa said:

Ah. Well that must be HY3712 then

It's double the resistance of SherMax; and they're using twice as many of them to compensate. 
Looks appropriate and unremarkable to me...

[meepmeepmayer]

Well.. if everyone is going to smaller mosfets, I guess they must be ok Overheat hill will show.

[Paul g]

 

    Sherman S boards design seem to have copied the V13 Raptor with its layered FET architecture:

 

So not just Begode??

Edited September 16, 2022 by Paul g

[RagingGrandpa]

@Marty Backe bring on Overheat Hill 

I think surface-mount is a welcome trend, versus through-hole, because:

• Avoids through-hole soldering, which was performed manually with terrible variation for these backside-mount components.
• Fewer components (no screws; no goop; no SIL pad) means decreased cost and also increased manufacturing repeatability. 
• Avoids leg-stress from bolting components to a planar heatsink (improves durability).
• Potential for even better heat transfer out of the IC's, especially when used with an aluminum-substrate PCB. 

Those cheap chunky TO-247 HY5012's from the MSX era had rather unimpressive ratings, and were problem prone (lots of dead-on-arrival or early-failing controllers because of manufacturing defects). I'm glad to see progress here.

  

15 minutes ago, meepmeepmayer said:

smaller mosfets

... but twice as many of them!
 

Edited September 16, 2022 by RagingGrandpa

[Paul g]

3 minutes ago, RagingGrandpa said:

@Marty Backe bring on Overheat Hill 

I think surface-mount is a welcome trend, versus through-hole, because:

• Avoids through-hole soldering, which was performed manually with terrible variation for these backside-mount components.
• Fewer components (no screws; no goop; no SIL pad) means decreased cost and also increased manufacturing repeatability. 
• Avoids leg-stress from bolting components to a separate heatsink (improves durability).
• Potential for even better heat transfer out of the IC's, especially when used with an aluminum-substrate PCB. 

Those cheap chunky TO-247 HY5012's from the MSX era were slow-responding (read: inefficient) and problem prone (lots of dead-on-arrival or early-failing controllers because of manufacturing defects). I'm glad to see progress here.

 

• Yes
• Yes
• Yes
• And yes

All hail the beginning of a new era.

[Paul g]

From an older discussion I had with @enaon , I think we should credit KingSong as well, since the flat-on-the-board FET in the S18 seems to have started the trend. Engineers sought the benefits and reproduced it in a form or other in the next wheels. I’m not so good with older wheels, so please correct me if I’m wrong.

Edited September 16, 2022 by Paul g

[Rawnei]

1 hour ago, meepmeepmayer said:

Some quite nice info pictures on ewheels. The board seems to have two independent power inputs, presumably one for each battery on one side of the wheel.

Glad that Veteran at least is sticking with TO-247 sized mosfets. They are not, see next post.

Very informative but I'm missing the arrow that shows where the lead is. 😁

Edited September 16, 2022 by Rawnei

[RagingGrandpa]

12 minutes ago, Paul g said:

flat-on-the-board FET in the S18

Sorry... there is no Kingsong yet with surface-mount FETs  

 

Edited September 16, 2022 by RagingGrandpa

[chanman]

Was going to mention that I think the S18 is still through hole, but has slightly different approach to the heatsink.

Anyway I think there's some advantages to the SMD form factor, but I think for reliability I'd prefer to have bigger ones that handle more current and have more heat dissipation instead of having more small ones. Unfortunately that goes against marketing who wants to have the board with the most FETs on it.

[Paul g]

@RagingGrandpa In the S18 FETs are trough-hole but they bend the legs and lay them flat on the board, and I think is a much better design for cooling since it allowed for mounting on a flat heat sink underneath. So my impression is that this is what led designers simply to go for surface-mount without needing to bend FETs legs 🤷🏻‍♂️

Edited September 16, 2022 by Paul g

[Paul g]

26 minutes ago, chanman said:

Was going to mention that I think the S18 is still through hole, but has slightly different approach to the heatsink.

Anyway I think there's some advantages to the SMD form factor, but I think for reliability I'd prefer to have bigger ones that handle more current and have more heat dissipation instead of having more small ones. Unfortunately that goes against marketing who wants to have the board with the most FETs on it.

Doesn’t more FETs spread on a larger area dissipate heat in a fan-less design better than less on a smaller area which would necessitate a fan? I think it might work better even if it’s not impressive. 

[chanman]

7 minutes ago, Paul g said:

Doesn’t more FETs spread on a larger area dissipate heat in a fan-less design better than less on a smaller area

I think this is generally correct, the reliability I was referring to is not from better heat management, but from having fewer components that can each have manufacturing or assembly defects or other random failures. The total area involved could be similar though with the larger components.

Edited September 16, 2022 by chanman

[Paul g]

@chanman I noticed the poor heat dissipation problem can lead to components failure (FETs as well) in many cases so the easier is the cooling the better for me. I also prefer a fanless design over one with a fan. Less FETs with more power will occupy a much smaller area and would automatically lead to fan design in my opinion. For less FETs start using copper heatsinks? Maybe that will be the next step, since 24 FETs seem to have reached a limit. 

The heat dissipation is almost double for copper.

Source: https://www.gabrian.com/copper-vs-aluminum-heatsinks/ 

 

Edited September 16, 2022 by Paul g

[enaon]

1 hour ago, RagingGrandpa said:

I think surface-mount is a welcome trend, versus through-hole, because:

•  

I really like them too, but I think the sandwich approach on the boards is not on the path of a fanless system.

Edited September 16, 2022 by enaon

[Paul g]

9 minutes ago, enaon said:

I really like them too, but I think the sandwich approach on the boards is not on the path of a fanless system.

Good observation. All-in-one-board design is king. That is why I like so much the S18 design (that was followed by S20-22 muddied by bad FET choice). That thing is a work of art! Every little space on that use-all-space-we-have board is used savagely:

I think the KingSong engineers that designed that board need to be appreciated for their mastery.

Edited September 16, 2022 by Paul g

[RagingGrandpa]

Ya'll are great, love design chats  
My favorite part is when I reveal something I believe and then discover my understanding was incorrect based on more information from others, so please keep the questions coming.

1 hour ago, Paul g said:

copper heatsinks

Copper sucks as a structural material... 
It's great for conducting (electricity, and heat), but we need somewhere to conduct the heat to. So we also need lots of surface area for convection.
Using the structural (aluminum) parts of the unicycle is a great way to get this surface area.

1 hour ago, Paul g said:

poor heat dissipation problem

But overall, it's an operating temperature problem.

We can improve it in multiple ways:

1. by using electronics that release less heat during operation
2. by using a cooling system that can shed heat more quickly

(My FET comparison is becoming a bit of an eye chart, but #1 is what the "Total dissipation" column is about: how much heat is released during the same operating condition across various designs. Less watts here means less cooling is necessary.)

 

1 hour ago, enaon said:

the sandwich approach on the boards is not on the path of a fanless system

Why not?

As shown below, the "driver board" handles all the major heat-releasing electronics, and the "communication board" holds the sensitive brains separately. 
Provided that the driver board gets mounted to some big flat metal box, it'll sink the heat away from everything nicely. 
Even better if the driver board is an aluminum substrate, bolted to an aluminum box, for thermal expansion matching...

2 hours ago, Paul g said:

Edited September 16, 2022 by RagingGrandpa

[RagingGrandpa]

New stairs vid looks awesome too!

https://www.facebook.com/linnea.lin.14/videos/1068413547176617 

[Paul g]

18 minutes ago, RagingGrandpa said:

New stairs vid looks awesome too!

https://www.facebook.com/linnea.lin.14/videos/1068413547176617 

Nice! I hear some beeping there, but other than that it sounds like a quality (bike) suspension should sound, no clunky noise like V13- the prototype faze. 

[Paul g]

1 hour ago, RagingGrandpa said:

Why not?

As shown below, the "driver board" handles all the major heat-releasing electronics, and the "communication board" gets the sensitive brains. 
Provided that the driver board gets mounted to some big flat metal box, it'll sink the heat away from everything nicely. 
Even better if the driver board is an aluminum substrate, bolted to an aluminum box, for thermal expansion matching...

My opinion is that less sensitive parts linked with screws is better in a vibrating environment. And I love compact design- less material, less box to contain it- more fun.

Edited September 16, 2022 by Paul g

[RagingGrandpa]

14 hours ago, EMA said:

btw i still don't know how people could be interested in a brand after the "Abrams show" ... 

Thought-provoking, as I'm finding myself more encouraged about Leaperkim than the competitors lately.

Regarding Leaperkim:

• Sherman 18650 was an uncommonly successful 1st batch. I still own one (confessing my bias) and nothing has been replaced. We also got to see Leaperkim's sober attitude towards electronics. "Install a fuse? Yes, from batch 1! Should we use a name-brand fuse in a bolted fuse holder rated for it? Yes we should!" etc 
• Abrams was bad, but not for obvious design reasons. It seemed to be an unlucky combination, their new motors, motor sensors, and controls. Improved now, but the model's reputation is ruined. Marketing a 22" 97lb mud-holding machine as the "offroad king" made Leaperkim seem out-of-touch with how real customers use EUC's on trails... but we can still think of them as an "improved surfaces only" product company.
• SherMax 21700 was a significant and successful update to the Sherman platform. Stronger axle, thicker cables, and more acceleration. The main issue I've heard reported has been 3rd-party (Litech) BMS failures.
• Upcoming ShermS is showing an emphasis on simplicity. Straightforward suspension with few moving parts; traditional 100V system; incremental improvements to hardware. 

Regarding competitors:

• GW/BG/EB seems all over the place, trying 10 things at once and not minding if 6 of them fail. EX:Supension, Hero, EX20S, and Commander will certainly not be regarded as "successful products" in EUC history (despite each having a few loving owners). XM's chassis begging to become jammed with mud and debris, a disappointment for us offroad users accustomed to the abuse-loving (sometimes sacrificial) MSuper shell.
  Thankfully the hasty / sloppy decisions regarding fusing and pack design have nearly all been addressed now, after many mis-steps including Master 1st batch. Good cells, good assembly, monitoring, warning. Hard-earned lessons that threatened the company's existence. 
• Kingsong seems disinterested in class-leading electrical output. 16X gave up too much speed to gain torque, and dropped a lot of people because of it. S18 was crippled by its 3p pack (better with high-drain cells in 3rd-party packs now). S22's controller struggles to reach output levels typical of models from 2018. I'm out.
• Inmotion has made the complexity mistake twice in a row, with V11 (poor suspension durability and poor electrical system durability), and V12 (borderline negligence with electronics fundamentals, while spending time developing tons of slick new features). And now they're reaching even further from their comfort zone with 126V V13 and its groundbreaking speed range. Some hear "fastest man alive," others hear "daredevil."

There's no such thing as a perfect wheel...
But maybe this helps explain how we can remain optimistic about Leaperkim  

 

Edited September 16, 2022 by RagingGrandpa

[Planemo]

The wheel aint worth shit if the suspension is crap. Its been done by Fastech which is effectively a cheap no-name chinese brand (compared to Fox, Rockshox and even DNM) and theres been no confirmation that the forks are even servicable which would be a dealbreaker IMO (I do my MTB shocks every 50hrs as reccomended). Plus it seems the shocks are coil rather than air which limits setup re rider weight/terrain. I dearly hope the Sherman-S is a sucess but as an MTB'er I am very sceptical of crap suspension. The OG/Max Shermans are still a force to be reckoned with imo and until a suspension EUC comes out with proper MTB level suspension I'm not interested. We'll see.

[Jon Wall]

Not really fair to compare Mtb to Euc. Mtb is been around so long and has grown so much.  And has big money  sponsored pro events to justify its Innovations costs 

Euc is still new in comparison. And has so little money in this tiny hobby 

Fastace isn't top shelf level but rather more budget parts sure. If this new Sherman s  had $3500 Ohlins/Rockshock/Fox pro level mtb forks on it,  we would all complain about the $7500 price tag. 

I  am looking forward to this riding like a magic carpet for my old knees 

[Jon Wall]

And let's be realistic here.  Begode/ Gotway suspension is pure garbage entry level with thier digressive linkage.  So compared to  that this looks Cadillac 

[That Guy]

4 hours ago, RagingGrandpa said:

ShermS

SherS? Shersie?… :-)

[fbhb]

Check out this Facebook video posted by Linnea Lin of Leaperkim, testing the durability of what I would presume are the New Sherman-S rims:

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