2WD PHATGOOSE

Or perhaps I'll call it 2wd FATMON (any of these names taken yet? :idea: ) -It's the mongoose steel fatbike I've been working on and this will be the build thread.

In the meantime I have a question before I put the boards pack in their cases and reattach etc etc, hopefully completing the new battery setup, including controller mod.

0905170926a.jpg



Background: The old 12s spun the 29" dia tires way too fast (44mph), and the battery was sagging like crazy anyway on takeoff.

So I went with 9s 30c 15ah zippys, and removed controller LVC jumpers from pcbs for now. I knew there would be less wattage/power on 9s (without shunt mods) but figured the lower gearing would make it a wash, at worst. (I will link all the threads pertaining to this build which includes one on modifying with a trim pot or the proper resistor for custom LVC on non-programmable cheapo controllers.)

Anyway, 9s does 33mph HOC WOT and 29mph-ish WOT when discharged. Here's how I've been testing the battery: Medics hot glued together with neo magnets on back.

0905170926.jpg


It works great to see the cell levels as I flounce this thing and 'get used' to being the 'bms' for the new pack via total pack voltage Led.

SOo0o, I went from 4.10 avg to 3.85v resting - ~3.75v WOT with brakes on at maybe 10mph quite a bit and nothing got noticeably hot. And although NET I have more torque now than w/12s, that means the front tire breaks loose first when thrashing a hill, alot quicker than before.
With everything staying super cool while pounding on it (. . . what she said?), I figured permanently increasing amperage to the rear motor would make sense on multiple fronts.

So finally, here's my question:
I have tentatively wrapped 8 strands around the 3 shunts which should easily lower resistance by 33%, guessing visually by the volume of the copper VS the shunts. So I assumed that should give me about 1/3 more amps?

0905170924.jpg

Results of the testing the mod(read: thrashing, lol):
Battery depletion and sag as noted above, thrashing WOT (even with brakes) the whole time . . . .

70F ambient
75F fets
90F Rear hub
87F Front hub
Short <1ft runs of thin-ass phase wire: 72F.

Seems like I should keep adding copper? Or start adding solder?

But I don't wanna blow anything up. I notice a little increase in torque and better balance rear VS front, but judging from less than a 10% temp increase (3 deg F on maybe 10ah of 'testing'!) for the modded controller , it really didn't do that much.
Maybe I should mod both front and rear??? Hubs can survive fine up past 200deg iirc, so even @ 100F ambient I wouldn't expect the current setup to get much over 140F while thrashing it thru nearly a whole 'tank' of electrons?

I'd like the rear to still have more power VS the front, so IYO (in your opinion?) what should I do and are there any things 'not to do' that this bonehead might stumble upon lol?? Thanks!
 
Hi nuts, I know this was a budget build for you and you were also aiming for simplicity/reliability so I get the reason you went for dd hub motors. I thought about the 2wd with dd hubs and fat tires for a while and basically realised that maybe the front wheel only needed a smaller motor to give the extra traction I wanted. Also I was thinking that my bike would be doing a lot of low speed climbing in steep terrain eg. loose gravel or sand dunes where front wheel slippage will be a problem. That's why I went for geared hubs, and so far with the rear only and the torque sim pas controller it's been great on climbs and mostly I only use pas 1 or 2 with 3-5 being too easy to out motor the pedals. Still waiting for my front parts to arrive so can't comment on that yet.
With your shunts would it work to wire in a trim pot of say 0-10 ohms and then dial in and set when happy? Or if you don't mind spending more cash get a 1000w sine controller with pas and run it on the front so you can dial in the pas level you want. BMS battery sells a cheap sine torque sim controller that would do the trick pas 1 should add around 180w of assist and level 2 around 250w and it stays the same at all speeds so less chance of front wheel spinning out at low speeds.
Anyway good luck hope that magic smoke stays where it belongs :mrgreen:
 
When people call me 'nuts' it reminds me like I'm bugs bunny and they're calling me 'bugs'. Odd.

Anyway thanks. Yeah I'll explain my reasoning and results of specific build choices above, along with full parts list, thread links, and photos etc when I 'make' some time. I will be following your coverage on your specifics and choices that you provide too- put it here or link your build if you have one. I think video really helps people get an idea too. It has really helped me get into this and know what I want and how to achieve it.

A trimpot would be cool, but I didn't find any good writeups on this discombobulated forum of information. Not even anything really complete or definitive on shunt modding w/copper and solder. Hmm I didn't think to try utube! Oh well, I'm pleased with the results of:

16 strands and 12" of #4 solder for the rear
6 strands and 6" of solder for front

(I don't know the gauge of the strands, but they're from a 10ga wire that has about 20 strands - so they're fairly thick and stiff. Like from some automotive battery wiring I guess.)

Very noticeable power increase and very reasonable acceleration. Of course there will be video eventually to backup my claims. . .
I will do the same stress tests and report temp rise as well. I'm guessing to see another 10F in the hubs and another 5f on the controller heatsinks at 70F ambient, which is still babying everything I'm thinking.

I also found out my 2wd switch for FWD RWD works just fine. Though I haven't found a reason to leave 2WD. . . But the problem I experienced ended up being the positive battery lead disconnected from one controller, and it tried to get it's power thru the ignition wire lol. No wonder the wire got hot. I took a pic of where it fried it's insulation, but all seems well, and when finalizing I tape all connections for this very reason.

I think the last thing before I do the write up is to install the 4" travel fork with beefy arms/plates that double as top and bottom rack mounts. Soon, very soon.

bugs.jpg
 
Hey no offence meant there nutspecial. Cool I really want to see how you set up your front end as I am trying to decide whether to go rigid or not when I'm running a front motor. I am still waiting for my parts to arrive, once I have the motor I can order the spokes and get the front wheel drive going.
 
Hey no worries! I'll make sure to catalogue the susp fork install and then start with that above. Actually pulled the wheel this morning and mocked it up in the new fork, checking drop outs and spacing etc. Looks like no d/o mods at all, as long as I flip the big flanged axle nuts with flange out.
At this point I'm thinking of two 6" crescent wrenches (adjustable) to beef up d/o's. I have several 'motorcycle fork turnsignal mounts' from ebay that are decent clamping steel brackets to attach the arms and racks etc. And some wired led headlights down low on the fork/rack. I'd probably tack the wrenches' moving parts together with glue or weld. The only downside is they have to go to the insides of fork but are not that flat, so I'm not sure how everthing will tighten down yet. I might just try some basic shimming with those high compression plastic shims or a chunk of uhmwpe.

Oh that's an idea! Maybe I can heat up the wrenches enough and press it into the uhmwpe so there are not only really flat sides for the axle washers and inside dropouts, but it might freeze the adjustment thingy!
 
Those indicator brackets look like they will work well. I think I will order a couple of sets.
I have a couple of pairs of 12mm torque arms coming with my order from BMS battery which I think are designed to work with hose clamps but I would prefer to use a solid steel clamp if possible.
I think you might be better off to use a couple of cheap open end spanners rather than use an adjustable wrench (we call em shifters here in down under land :lol: )
 
nutspecial said:
Or perhaps I'll call it 2wd FATMON (any of these names taken yet? :idea: ) -It's the mongoose steel fatbike I've been working on and this will be the build thread.

In the meantime I have a question before I put the boards pack in their cases and reattach etc etc, hopefully completing the new battery setup, including controller mod.

View attachment 2



Background: The old 12s spun the 29" dia tires way too fast (44mph), and the battery was sagging like crazy anyway on takeoff.

So I went with 9s 30c 15ah zippys, and removed controller LVC jumpers from pcbs for now. I knew there would be less wattage/power on 9s (without shunt mods) but figured the lower gearing would make it a wash, at worst. (I will link all the threads pertaining to this build which includes one on modifying with a trim pot or the proper resistor for custom LVC on non-programmable cheapo controllers.)

Anyway, 9s does 33mph HOC WOT and 29mph-ish WOT when discharged. Here's how I've been testing the battery: Medics hot glued together with neo magnets on back.

View attachment 3


It works great to see the cell levels as I flounce this thing and 'get used' to being the 'bms' for the new pack via total pack voltage Led.

SOo0o, I went from 4.10 avg to 3.85v resting - ~3.75v WOT with brakes on at maybe 10mph quite a bit and nothing got noticeably hot. And although NET I have more torque now than w/12s, that means the front tire breaks loose first when thrashing a hill, alot quicker than before.
With everything staying super cool while pounding on it (. . . what she said?), I figured permanently increasing amperage to the rear motor would make sense on multiple fronts.

So finally, here's my question:
I have tentatively wrapped 8 strands around the 3 shunts which should easily lower resistance by 33%, guessing visually by the volume of the copper VS the shunts. So I assumed that should give me about 1/3 more amps?

View attachment 4

Results of the testing the mod(read: thrashing, lol):
Battery depletion and sag as noted above, thrashing WOT (even with brakes) the whole time . . . .

70F ambient
75F fets
90F Rear hub
87F Front hub
Short <1ft runs of thin-ass phase wire: 72F.

Seems like I should keep adding copper? Or start adding solder?

But I don't wanna blow anything up. I notice a little increase in torque and better balance rear VS front, but judging from less than a 10% temp increase (3 deg F on maybe 10ah of 'testing'!) for the modded controller , it really didn't do that much.
Maybe I should mod both front and rear??? Hubs can survive fine up past 200deg iirc, so even @ 100F ambient I wouldn't expect the current setup to get much over 140F while thrashing it thru nearly a whole 'tank' of electrons?

I'd like the rear to still have more power VS the front, so IYO (in your opinion?) what should I do and are there any things 'not to do' that this bonehead might stumble upon lol?? Thanks!
Click to expand...
You should just use 36 V controllers w/ 9S. The LVC for the 36V controller is 31V, which leaves the cells around 3.50V, a pretty good stopping point for LiPoly. Personally, I would never ride w/ LiPoly w/out a hard and foolproof LVC in the controller.
My experience w/ soldering shunts has resulted in the same gain every time. Pushing 2 shunts together and coating with solder lightly yields a 5 Amp gain. Adding more solder will not increase that. So pushing all 3 together and coating should yield an increase of 7.5 Amps. If you were to get the controllers w/ the LVC for 9S LiPoly, it wouldn't matter as you could pick the rating you want and not need to shunt mod. This would solve you "power distribution" problem as well, although I just use two throttles which works better and is more fun the the single throttle schemes I tried;
.
.
100_0028.JPG
A thumb to the inside of a left-hand, half-twist.


100_0029.JPG
Very intuitive and easy to use



BTW, the black Battery Medics are junk. It's the high quality blues ones you want.
 
Thanks for the info Motomech, I dig your setup man!

I'll reply more in depth when I get a chance- in the meantime any posts are welcome-
Any questions for someone doing a build etc or just PM and I'll post up whats applicable.

I gotta say it works really good. But it is a tractor offroad. The weight in the wheels, and in total, and rigid rear, and big ass tires. But it's just good enough torque and topspeed for offroad and pedalling down the road @ 30mph.
 
Answering a pm for some stuff used-

https://www.ebay.com/itm/Blackburn-Local-Spring-Clip-Front-Rear-Cycling-Bike-Pannier-Bag-Rack/124101263039?hash=item1ce502febf:g:jmwAAOSw4zJeSG5S

Blackburn front/rear racks, customized mounting

Ibera triangle frame bag (large, 3 straps on top) -don't see on ebay currently @ first glance
 
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