My Sherman Trials, Tribulations, and Triumphs

[Marty Backe]

3 hours ago, MrRobot said:

@Marty Backe did you add silicone back over the connections on the control board after reassembling? What kind did you use? 

I only added a dab of "silicon" (bought from the hardware store) to the hall sensor connector.

Also, it's important to reapply the heat shrink tubing over the motor wires. It prevents the screws and wires from loosening from the control board posts. If you don't, figure out some other means of assuring that the wires won't come loose.

[MrRobot]

8 hours ago, Marty Backe said:

I only added a dab of "silicon" (bought from the hardware store) to the hall sensor connector.

Also, it's important to reapply the heat shrink tubing over the motor wires. It prevents the screws and wires from loosening from the control board posts. If you don't, figure out some other means of assuring that the wires won't come loose.

What a nightmare. Do you know what size heat shrink tubing I'd need? 

Edited September 30, 2020 by MrRobot

[Marty Backe]

12 hours ago, MrRobot said:

What a nightmare. Do you know what size heat shrink tubing I'd need? 

Not exactly, but it looks over 1/2-inch. Basically, it needs to be large enough to go over the large posts that the motor wires are screwed into.

[FreeRide]

On 9/22/2020 at 8:38 AM, Toshio Uemura said:

Didn’t know they do any. I always thought someone at the end of the production lines just put a little round sticker „QC passed“ (QC = Quacktacular - Something that tastes as good as a duck, but doesn't quite reach the high standards of ducktacular.) on every wheel not knowing why and what it means. 😆 

What makes you think they do this at the end of the line?

[Matthieu Thegrey]

Hey @Marty Backe I just read the whole topic, you made an amazing job testing this machine. But I have finally not been able to get the conclusion of the reason of that impressive burned motherboard on your first hill climbing test. Did you finally managed to undestand?
Is it because the moto cables melted down, causing a short that in reaction destroyed the motherboard? What should be fixed now with the bigger cables.  Or do you think it was temperature related (the motherboard got too hot, what caused a component to fail and finally catch fire?).

Thank you !

[null]

Indeed, there is a similar looking case over at the French forum, the cooling was obstructed by rain gear and the tire encumbered with mud (as far as I understood), which could replicate Californian temperature and a strong uphill. The fried board looks the same, with missing battery cables, capacitor on the loose and even partly melted fan.

Edited December 23, 2020 by null

[Matthieu Thegrey]

Yes, I would like to understand the reason for these cases, in order to either increase cooling or whatever would help.

[meepmeepmayer]

1 hour ago, Matthieu Thegrey said:

Yes, I would like to understand the reason for these cases, in order to either increase cooling or whatever would help.

This has little to do with outside temperature or obstructed cooling or whatever. The motor power cables simply are too thin for certain high currents that appear under extreme stresses (continuous very steep uphill).

Usually the motor cables melt their insulation, short together, and the short blows up the rest of the board like a mosfet or a capacitor. You can tell because the cables are melted together, which probably wouldn't happen from a mosfet or other component frying and producing the original short.

To prevent this, Gotway (they had the same problem 3 years ago) and Veteran simply added fiberglass insulation sleeves (this stuff doesn't melt or burn, these white sleeves you see around the motor power cables and in some other spots). The first Shermans didn't have that insulation. I very strongly believe the Sherman in the French example was one of the first ones because the fried board looks extremely similar to what happened to Marty's test Sherman on overheat hill.

With this insulation, while the cables are technically still too thin (electronics that get that hot are simply too small for the purpose) nothing really can happen. Under high stresses, the next weakest component that would break are a mosfet or a capacitor, and it appears the overheat alarm kicks in before these die.

So TLDR, with the fiberglass insulation, this frying won't happen, no need to worry with the current Shermans as far as I can tell

Edited December 23, 2020 by meepmeepmayer

[Matthieu Thegrey]

Thank you a lot, I will pass the message to the french forum, your experience is very helpful !!

[fbhb]

1 hour ago, meepmeepmayer said:

With this insulation, while the cables are technically still too thin (electronics that get that hot are simply too small for the purpose) nothing really can happen.

When @Marty Backe received the replacement motor from Veteran, after the OHH incident, he noted that Veteran had indeed increased the cable thickness along with the addition of the fiberglass insulation sleeves!

All batches since the very early ones have now had this upgrade, Along with a fuse on each of the 2 battery banks to prevent the extreme high currents that caused control board failure! 

[null]

@meepmeepmayer : Martys board didn't short the motor cables though, they had started melting (hence he waited for the new motor) but they didn't show any trace of short.

If you look at Martys video, you can see it is at the arrival of battery current to the board everything is fried. The discussion went long and wide, with Martys theory being that the patch was probably too small for that much current, which Chriull, who's main theory was blown caps don't rule out here  The original discussion starts around here.

(the motor cable picture on the French forum is Martys "melted but not totally" )

Edited December 23, 2020 by null

[Matthieu Thegrey]

There is one thing i don't understand: the board is protected by fuses on each side, and the current spike happened anyway (and it does'nt seems like just a tiny one, seeing how the capacitor has been blowned away). How is it possible? Even if the short happened on the entrance of the moterboard, the fuse should have blown. Is it possible that these fuses are just too big caliber to protect the board from current spikes? In this case, it seems we could easily fix this by  replacing them with lower caliber ?

OR could it be temperature related? The temperature rises slowly in the motherbaord chamber, then a solder fails, the capacitor fails and releases it's stocked current suddenly... ?

Edited December 24, 2020 by Matthieu Thegrey

[.....]

9 minutes ago, Matthieu Thegrey said:

There is one thing i don't understand: the board is protected by fuses on each side, and the current spike happened anyway (and it does'nt seems like just a tiny one, seeing how the capacitor has been blowned away). How is it possible? Even if the short happened on the entrance of the moterboard, the fuse should have blown. Is it possible that these fuses are just too big caliber to protect the board from current spikes? In this case, it seems we could easily fix this by  replacing them with lower caliber ?

Just tossing a guess, but perhaps the fuses werent protecting as the current thru them wasnt so much a spike as a prolonged current. Again, just a guess. But is it possible the fuses will pass current that is below their break point and pass it for an infinite duration? Perhaps this amount of current over time, can heat board parts. Once heated, maybe board parts begin to lose their ability to function and short or blow, even tho they are under the current required to blow a fuse. If you slowly turn up the heat, the frog will boil before he jumps out. Turn it up fast and he's outta there. Perhaps its 'frog' style fuses?

Im enjoying this discussion, its great to read all the interesting ideas and data. I wonder how many companies invest as much time as this simple thread has... in problem tracing?

Edited December 24, 2020 by ShanesPlanet

[Jesse]

Hello, I have a question for which I’m looking for an answer. Sometimes and most times when I ride my Sherman it makes a small vibrating sound- I’ve read the above posts and am wondering if this is the torque ripple mentioned- my true question is out of concern for the longevity of my unit. So here it is: if what I am experiencing is torque ripple- is this bad for the unit or basically normal and if it is bad what can be done about it? When it happens my mind immediately goes to maybe I should recalibrate the wheel, but I know absolutely nothing about tech other than I love to ride it. Is there any maintenance I should be doing on the wheel like keeping it clean? Thanks for any responses/suggestions. 

[Planemo]

My Sherman is as smooth as butter at all speeds. I have seen some that have a badly aligned tyre, maybe this is the problem with yours? Mine happened to be very good when I recieved it so I have never touched it. In fact I dont ever want to deflate it until its worn out!

If you're unsure, lift the wheel and post a vid of the tyre at around 10 to 15 mph and we will give you an opinion.

[Kekafuch]

6 hours ago, Jesse said:

Hello, I have a question for which I’m looking for an answer. Sometimes and most times when I ride my Sherman it makes a small vibrating sound- I’ve read the above posts and am wondering if this is the torque ripple mentioned- my true question is out of concern for the longevity of my unit. So here it is: if what I am experiencing is torque ripple- is this bad for the unit or basically normal and if it is bad what can be done about it? When it happens my mind immediately goes to maybe I should recalibrate the wheel, but I know absolutely nothing about tech other than I love to ride it. Is there any maintenance I should be doing on the wheel like keeping it clean? Thanks for any responses/suggestions. 

Do you have attachments to the Sherman? Like seat? Do the vibrations happen this in all modes or just certain modes? 
 

probably need to have it video documented in order to get better assistance. 

[Jesse]

The tire is aligned properly, has no wobbles or anything out of place. But yes I did get a seat, I will run it without the seat and see if this makes the difference. I keep the wheel in hard mode. I appreciate the feedback, thank you.

Edited February 2, 2022 by Jesse

[fbhb]

43 minutes ago, Jesse said:

But yes I did get a seat, I will run it without the seat and see if this makes the difference. I keep the wheel in hard mode. I appreciate the feedback, thank you.

If the vibration is mostly felt when riding seated and in Hard Mode, then the Hard Mode/seated riding combination will be the cause of the issue. If you try switching to Medium Mode does the vibration go away when riding seated?

I have just personally fitted a seat to the front and rear Roll bars of my Sherman, but I ride in Medium mode now having been made aware of this some time ago, but I also used to ride in Hard initially!

The ride has always been smooth for me on my Sherman, but maybe your issue is elsewhere if Medium mode does not correct it. Report back with your findings, so we can help?

Edited February 2, 2022 by fbhb

[Jesse]

I will thanks so much, these threads are all new to me and I do appreciate it he help. I live in Denver and we’re getting slammed with a snow storm so it might be a week before I can get back on the wheel. As soon as I can I will, and I’ll do a range of tests involving switching modes with the seat on and also taking the seat off. The seat is very low and hardly used, basically only for a rest on long long rides otherwise it’s dead weight. Thanks so much I’ll be back soon:)

oh and the vibration/noise is felt/heard when I’m standing and not seated, it doesn’t happen all the time, I feel like it’s more when I’m going slower. I’ll get some video the next time I’m on the wheel, promise.

Edited February 2, 2022 by Jesse

[Planemo]

I have read numerous reports of Shermans vibrating when in hard mode with a seat. I dont know exactly why, I presume that without the flexibility of legs when standing, some kind of feedback loop gets set up when the wheel is trying its hardest to remain absolutely level.

I also read that when the same people switched to medium the problem went away. For sure, I have never had vibrations when seated (a home made one on the rollbars) but I have never used any other mode than medium so I cant confirm personally. Let us know what your findings are, it would be interesting!

And you say your seat is heavy...how heavy out of interest?

[Jesse]

No the seats not heavy, it’s from a guy in the UK. I think his name is Brian, a quick google and he’ll come up. It’s a foam seat on top of wood backer with vinyl and snap clips, it might weigh one pound, what I was trying to say is the amount of time I’m on the seat is about 5%, so for the majority of the ride it’s not being used and is just dead weight. If it’s causing the problem I’ll just ride without it, I’ll try switching the modes tho. And the seat is way to low anyway, I’d like to find one that’s adjustable or more like a traditional unicycle; when you ride a traditional unicycle- when you pedal and your foot bottoms out on the pedal- your almost standing. IMO it should be similar on a EUC, not so that it’s tight on yer bum the whole time but being able to drop down a couple inches and sit here and there would be nice- then rise for anticipated bumps and such. 

[Planemo]

Yeah I know the ZoomWheels seat, its not overly heavy as you say. My diy one is pretty similar I would think.

I do hear you on the height. I'm 6'1 and for sure the seat is a lot lower than I would run on a bicycle but it is what it is. To have a seat on the Sherman at a height like a bicycle would be a bit of a pain for overall size/handling when standing, not to mention it would look a bit crap imo. I like the sleeker looks with it low, despite it not being optimal for comfort.

I dont use mine much either, but I tend to leave it on there anyway as I really dont think it hurts range, I dont often need the trolley handle (although I trimmed the front clips to make it easy to lift up) and its nice to have it there if I fancy it.

[Freeforester]

1 hour ago, Planemo said:

Yeah I know the ZoomWheels seat, its not overly heavy as you say. My diy one is pretty similar I would think.

I do hear you on the height. I'm 6'1 and for sure the seat is a lot lower than I would run on a bicycle but it is what it is. To have a seat on the Sherman at a height like a bicycle would be a bit of a pain for overall size/handling when standing, not to mention it would look a bit crap imo. I like the sleeker looks with it low, despite it not being optimal for comfort.

I dont use mine much either, but I tend to leave it on there anyway as I really dont think it hurts range, I dont often need the trolley handle (although I trimmed the front clips to make it easy to lift up) and its nice to have it there if I fancy it.

Just wondered whether there might be any scope for removing  the clips from the seat underside and fitting a ‘sarkozy’-type (I hesitate to use ‘style’ 🤔) height ‘improver’ and reattach the aforementioned clips, in order to raise the seat by an inch or two? 6’ + myself, though have plumped for the EUC Market Alexa seat (currently awaiting delivery).

Edited February 2, 2022 by Freeforester

[Jesse]

I made a box out of aluminum (I’m a welder) for the seat to sit on and give it some height, and also a place to store gloves and such, about another five inches higher. When it was all done i put it on and turned the wheel on and it went crazy, I turned it off immediately and abandoned the box idea. I put the seat back to the way it was originally and there were no issues except for this vibrating a little here and there. After all this correspondence I’m sure the vibration is due to the seat, I’m not sure what kind of interference is occurring but I’m not taking any more chances. Soon as the snow melts and I can get back on I’ll take some video for you all to see and pretty much abandon the seat. 

Edited February 2, 2022 by Jesse

[meepmeepmayer]

1 hour ago, Jesse said:

When it was all done i put it on and turned the wheel on and it went crazy

That's strange. I wonder what the reason is. Electrical interference? Somehow the seat puts (mechanical) stress on the board?