Woods Fat-E-Bike build log.

pullin-gs

1 kW
Joined
Jul 31, 2009
Messages
395
This is my fourth e-build and first off-road mid-power E-Bike.
Here are my initial planning notes from 3 months ago:
E-Bike is purpose-built with these capabilities in mind.
*) Budget is $1500.
*) Engineered as off-road capable for state/national park offroad riding......Primary challenge for a Florida woods-bike is low weight while being sure-footed in loose sand.
*) Fat tire platform with 26x4" rims. Allows bike to "float" (Regular mountain bikes sink or dig-in) on sand trails & fireroads.
*) Need power to push through loose pack trails. Will most likely use 2170 cells. 52V arrangement. 70 cells (14Sx5P) build?
*) Low speed torque. Expect a bigger geared rear hub motor will do well. I dont want a mid drive.
This should do nicely for 1500w, 2000w max. https://www.aliexpress.com/item/4001314078195.html

*) I will use this frame: https://www.framedbikes.com/products/framed-minnesota-2-0-x5-crankset-fat-bike-frame-kit
*) I will use a Bolany "fat" mountain bike air fork.
*) I like performance and simplicity of generic Chinese controllers, so will be going with a 60V 50A+ controller of some sort.
*) Rims/spokes/tires get decided on after I go over motor and frame.
*) Battery&electronics will be enclosed in custom aluminum case which shaped to fit tightly in the frame triangle.
*) Will need to buy disc-brakes package, head bearing kit, crank bearing kit, peddles, crank, chain, chainring.
*) Top speed not much concern. 25MPH would be nice.

I thought long and hard about going with an enduro full suspension build, but in the end I decided to go light with aluminum hard-tail fat-bike MTB frame.
 
Day-0 of build. February 10 2010.
Engineering is complete.
Modeling (Visio pack/frame-layout drawings, rim/spoke/hub calculations, frame strength/use-requirements, drivetrain controller/pack/motor scaling) went well and suggest that my selected components will meet my needs to a T.
Design/Engineer/build-once -OR- Wing-it/build-it-more-than-once!
Everything is ordered. Most core components have arrived.
Samsung INR21700-50G batteries arrived yesterday! Tough to get these in the states for good price. I paid .50c on the dollar.
Samples tested in line with OEM specs (not counterfeit)! Chinese make fakes...but fakes nowhere near specs of real Samsung cell.
Will use 70 for my 52V 25AH pack-build (this was changed at a later date.....story why is below).
Pictures:
Bare bike frame, and the boxes are the other parts such as rims, motor, fork, etc.
Frame DID NOT come with headset, bottom bracket or crank. The ones that are in pictured frame I bought separately.
Other picture are the Samsung INR21700-50G 5000mah cells I will use.
I started heat-shrinking each bare cell and prep ends for welding last night...will post pack details in a separate post below.
Pack&electronics will be enclosed in aluminum box that fits inside frame's "triangle".
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Day-10 (Feb 20)....things coming along.
Laced rim to hub motor
Prepped frame for internally routed brake and shifter cables
Fabricated battery and aluminum battery case (this took days to complete!). Turned out nice though.
Cells all tested great with at least 5.0AH capacity.
I received all the brake components (hydraulic, 200mm front rotor, 160mm rear) and mounting hardware.
Tested motor and electronics. All tested fine.
Selected 1500W 50A 48V-72V controller.
MAJOR PROBLEM discovered when I tested motor: Vendor sent wrong motor! Motor's copper windings are wound for high speed, not high torque. KV is MUCH TOO HIGH!
Not sure if I can use it or not. I can lower pack voltage (slows down motor) and increase current with more parallel cells (more torque)?
Right now motor spins 26" wheel at 40MPH unloaded......I engineered bike drive-train&battery for 25MPH max speed high-torque for pushing through Florida sand on trails.
I'm skeptical I can make this motor work. Have contacted vendor and asked them to replace with correct winding that I ordered.
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Need torque-arms.....dont like any of the options available for sale, so I manufactured my own.....
Fashioned them from 1/4" steel plate.
The frame's rear brake caliper mount is very stout and very accessible, so I decided to use it as anchor point for a torque arm.
I took some measurements and laid out the design in Microsoft Visio.
I love Visio for this sort of work. I can print final design to scale and simply use printout as a pattern to guild all metal work.
A machine shop would be nice to have access to....however in the end all tasks for this build can be completed with simple hand tools. For this job I used a ryobi cordless angle grinder with cutting blade, a file, power drill, cobalt bits, mechanical dial caliper, and center punch.
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Triangle alumimum case build.
I spent more time planning and building this than any other system on this build.
In the end the attention to detail rewarded me well.
I started out by locking in on components and laying them out in the space available in frame.
I had to file off all the cable guides and frame fittings to give me more space. Will be routing cabling inside frame instead.
I was able to buy a single aluminum plate (1/16" x 15x15") and cut out both triangle sides from it. Again, Visio to the rescue in laying out dimensions for all components, printing a SCALE blueprint for each side, and cutting the plate to the printout.
Items which go in triangle include:
Power panel (5A 12v circuit fuse, 8A charge port fuse, 40A battery fuse)
48V to 12V converter....powers lights, fans, ampmeter, and other accessories.
Connectors for halls, throttle, windings, brake, lights
50A controller
Triangle 30AH 44V pack.

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Front wheel, brakes, fork....
I went with a 32H front 26x4" fat rim, 36H 26x4" rim rear.
Zero offset.
I used ebike.ca spoke calculator and order 14G spokes from my go-to spoke maker (eBay seller "childhood_dreams" ).
Laced wheels turned out great and trued-up nicely.
For the front fork, I purchased a Balany Fat Bike Air Suspension Fork 26*4.0"
https://www.ebay.com/itm/224171429805
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Nice build! :thumb:

pullin-gs said:
MAJOR PROBLEM discovered when I tested motor: Vendor sent wrong motor! Motor's copper windings are wound for high speed, not high torque. KV is MUCH TOO HIGH!
Not sure if I can use it or not. I can lower pack voltage (slows down motor) and increase current with more parallel cells (more torque)?
Right now motor spins 26" wheel at 40MPH unloaded......I engineered bike drive-train&battery for 25MPH max speed high-torque for pushing through Florida sand on trails.
I'm skeptical I can make this motor work. Have contacted vendor and asked them to replace with correct winding that I

Read the last post from Bullfrog on this thread:
https://endless-sphere.com/forums/viewtopic.php?f=3&t=109778

It's not about the kV or unloaded speed. If the internal reduction ratio of your motor is the same as every motor(winding) of this type they could have sent you, the torque that the motor can output is the same. But the phase amps need to be higher to achieve that.
 
pullin-gs said:
SlowCo said:
Nice build! :thumb:

pullin-gs said:
MAJOR PROBLEM discovered when I tested motor: Vendor sent wrong motor! Motor's copper windings are wound for high speed, not high torque. KV is MUCH TOO HIGH!
Not sure if I can use it or not. I can lower pack voltage (slows down motor) and increase current with more parallel cells (more torque)?
Right now motor spins 26" wheel at 40MPH unloaded......I engineered bike drive-train&battery for 25MPH max speed high-torque for pushing through Florida sand on trails.
I'm skeptical I can make this motor work. Have contacted vendor and asked them to replace with correct winding that I

Read the last post from Bullfrog on this thread:
https://endless-sphere.com/forums/viewtopic.php?f=3&t=109778

It's not about the kV or unloaded speed. If the internal reduction ratio of your motor is the same as every motor(winding) of this type they could have sent you, the torque that the motor can output is the same. But the phase amps need to be higher to achieve that.

Thanks for the note. :)
Agree, Indeed gear reduction is same for G062 motors.
KV is a function of RPM, gear ratio, and voltage to achieve said RPM. Being that ratio is constant, the only factors influencing KV for the G062 is voltage and given RPM at said voltage.
There are indeed two G062 #turn options that I know of for stator winding.
The 20" motor I received has lower turn-count (higher KV) than motor I ordered that is targeted for 26" builds.
Agree that torque can be same when amps are raised....that is why I built a pack with higher AH capacity....and controller with higher amp rating. I also dropped voltage to drop KV (speed) of motor to bring back in line with my target speed all while maintaining target torque.
https://www.rotordronepro.com/understanding-kv-ratings/#outer-popup
"Torque is determined by the number of winds on the armature and the strength of the magnets. A low Kv motor has more winds of thinner wire—it will carry more volts at fewer amps, produce higher torque"

That is why I changed my pack's originally designed "S/P" (I had not welded pack yet, so no big deal) geometry to a pack with higher AH capacity (and higher max current)....and controller with higher amp rating. I also dropped pack voltage to drop KV (speed) of motor to bring back in line with my target speed all while maintaining target torque.
The principle reason I had concerns about using this motor was that the phase cables feeding the motor are the weak-link in this whole engineering excersize: Cables ARE SAME for all winds of motor.
As you state " phase amps need to be higher to achieve ".
Yes, it would appear so, however herein lies the problem: I can indeed increase phase amps, and get a bigger controller and get a beefier battery, but motor phase cables and motor connectors can not be changed out.
Anyway, I ended up using the motor. It performs very well actually. I would have rather gone with a higher KV and higher voltage pack though. Modeling (ebike.ca) puts torque at 105NM (vs 75NM) with higher KV motor and 52V pack using same 35A max controller.
 
Done! (almost) with new scratch-build using G062.1000 Bafang motor!
This build turned out FANTASTIC!
It eats up the off-road soft&loose Florida sandy state park trails and forest roads.
I decided to keep the motor and adjust pack&controller to accommodate higher KV.
Originally I was going with a 14S5P pack, but since KV was much higher than specs or ordered (I received a 20" motor vs 26" version I ordered) I lowered pack voltage and upped AH.
The controlle's LVC had to be adjusted down as well for lower voltage pack.
Top speed is 33.0 MPH. Weighs 64lbs.
Hydraulic brakes work great. The cables/hoses/wires mostly route internally to frame.
30 days after I started build I did my 1st ride using a 7AH pouch-cell pack. I fried my 30A on/off switch on first ride....so yanked it and put on a 90UC loop plug key instead of switch.

I got my confidence up to try a 30 mile OFF ROAD ride yesterday with new pack. No issues at all.
I received a lot of curious looks of approval from offroaders/ATVers/dirtbikers though!
LVC kicked in at 42V, so I left about 50% of my pack's capacity on the table.
I hacked the LVC on my generic 50A controller down to 38V last night.
I'll post a few other notes on brakes, electronics (12V power system for accessories).
Power delivery from pack maxes out at 1600W. I could go higher, currently I have controller strapped at 35A maximum. The stock cheap china controller is rated for 50A. I kind of like the way it is now. It is a very "well balanced" build and has performed beyond my expectations. Motor did not get too warm after one hour of hard riding today.
I run my tires at 6 PSI in the woods, and 10PSI around town.
Fat-tires soak up terrain and work well with hard-tail build.
Got some "arm-pump" pain I need to sort out....will adjust bar height and maybe change grips.
This is a throttle-only build, so I will not be taking it on the bike paths.
Wheelies are strange compared to dirt bike that has engine braking all the time.....will have to learn a better technique.
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Great job on the tq. plate! :thumb:

There should be a way to "mate" the (enclosed) controller base to the rear plate of the aluminum battery box for better heat dissapation if necessary.
 
Here is the buld-sheet.......total price came in UNDER BUDGET(!) @ 1583.29!
Total time spent was 80+ hours.
You can buy a pretty nice E-Bike for around 2K, so no money made here.....but the end result is a quality product that I simply could not purchase (anywhere) which is tailored to my specific needs and performance.
Build list:
Frame: Framed Minnesota 2.0 18". 175mm ODA rear hub 142.00
Front Fork: Bolany fat Air 135mm Straight 140.00
Headset 28.6mm fork, ZS44 (44mm press fit cup) 12.00
Fork headset spacer set 9.00
EC90 Carbon Handlebar 31.8x700 riser: 30.00
EC90 Handlebar stem 12.00
Seat post/clamp 30.9mmx400mm 25.00
Seat 16.00
Motor: Bafang RMG062 1000W 48V CST Geared motor: 243.00
Controller: 1500w/60v (modded LVC for 12S 44v) 30.00
Battery 21700 cells: QB27100 x 72 275.00
Battery cell spacers 20x13P honeycomb 21700 18.00
2x 15x15" aluminum plates for ebike triangle box build 42.00
.5x.5 1/16th aluminum angle 8-feet 8.00
Nickel Strip Tab 0.15mm x 22.7mm offset 18.29
12V regulator for ebike lighting, USB charger, power meter 16.00
Front Rim 26" 32H 80mm 55.00
Front Spokes kit 36.00
Front wheel hub 28.00
Rear Rim 26" 36H 80mm 55.00
Rear Spoke kit 36.00
Rear 8SP cassette 18.00
8 speed SRAM SP-830 chain 14.00
8-Speed Rear Derailleur Schmimano Altus 23.00
Bottom Bracket 100mm SRAM GXP 42.00
2X tires 26x4 80.00
Rotors 203mm front (and 203mm IS adapter), 160mm back 25.00
Hydraulic brake set 53.00
12V Motorcycle LED Headlight 15.00
2x fat tire tubes 26x4 22.00
Hydraulic brake service tools (cutter, baby oil, crimp ends) 20.00
Misc stainless steel fittings, steel plate for torque arm 25.00
TOTAL 1,583.29

Modeled performance for pack/controller/motor combination selected:
 

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Great result :thumb:
To improve the "bicycle feeling" in the future you might want to consider (a) PAS (capable controller) so you don't need to (but can) use the throttle. If you program each assist level with max. speed but increasing amps per step you can choose how much assist you want in each situation. And still override with the throttle if necessary. Just a thought.

pullin-gs said:
The principle reason I had concerns about using this motor was that the phase cables feeding the motor are the weak-link in this whole engineering excersize: Cables ARE SAME for all winds of motor.
As you state " phase amps need to be higher to achieve ".
Yes, it would appear so, however herein lies the problem: I can indeed increase phase amps, and get a bigger controller and get a beefier battery, but motor phase cables and motor connectors can not be changed out.

The trick that some DD hub motor modders did/do is to cut the phase wires where they exit the motor and crimp/solder much thicker wire from there to the controller. Not only the resistance of the wires will drop but the thermal conductivity will increase. So the heated phase wires inside the motor will be able to shed their heat to the thicker outside wires.
 
SlowCo said:
Great result :thumb:
To improve the "bicycle feeling" in the future you might want to consider (a) PAS (capable controller) so you don't need to (but can) use the throttle. If you program each assist level with max. speed but increasing amps per step you can choose how much assist you want in each situation. And still override with the throttle if necessary. Just a thought.

pullin-gs said:
The principle reason I had concerns about using this motor was that the phase cables feeding the motor are the weak-link in this whole engineering excersize: Cables ARE SAME for all winds of motor.
As you state " phase amps need to be higher to achieve ".
Yes, it would appear so, however herein lies the problem: I can indeed increase phase amps, and get a bigger controller and get a beefier battery, but motor phase cables and motor connectors can not be changed out.

The trick that some DD hub motor modders did/do is to cut the phase wires where they exit the motor and crimp/solder much thicker wire from there to the controller. Not only the resistance of the wires will drop but the thermal conductivity will increase. So the heated phase wires inside the motor will be able to shed their heat to the thicker outside wires.
Great suggestions......thanks.
PAS is something I dont want really, but may need in order to keep forest rangers at bay. Dirtbikes and ATVs are illegal unless tagged. MTBs are OK as are Class-III ebikes. I think I"ll be OK with the wires for now at 35A. If I decide to turn up the amps I may have to revisit.
 
Selected electronics:
The controller is a $33 "Multi-voltage" 1500W 50A controller.
https://www.ebay.com/itm/164234142888
I had intended building with 1 14S pack, but ended up building a 12S instead.
I modified the "48v" LVC to accomidate lower voltage cutoff needs of 12S pack.
I soldered a 1M resistor in parallel with the primary 120K voltage divider resistor (Not the 48V resistor) to lower resistance (which lowers voltage divider voltage which feeds pin-38 of controller CPU. Note that this mod changes LVC of ALL voltage options rendering LVC no good for all other voltages.
I also modded max controller max amps to 35 amps (stock amp max is 50A) for time being. Depending on results I may up amps a bit. Motor will indeed handle it, but I really dont need to do it because e-bike performance is stellar as is right now.

The motor I am using is a Bafang G062-1000-dc 1000W geared hub motor.
https://www.aliexpress.com/item/1005001656761614.html?spm=2114.12010612.8148356.9.25256cb6COTIfd
KV came in much higher than expected, so order at your own risk. Review performance was much LOWER than I am seeing:
https://ebikereviewer.com/index.php...-and-comparison-bafang-dapu-shengyi-and-more/
Review and specs state 23MPH expected speed w/26" wheel. I'm seeing 33MPH actual with 42V pack.....thus the reason I changed pack from 14S down to 12S.
VERY nice motor. Performs strong (I can go 1500W all day.....gets warm, but not hot to touch).

All accessories (fans, lights, 5V USB charge port) are 12V powered using buck DC converter.
https://www.amazon.com/LIVISN-Water...e+72v+48v&qid=1617066277&s=electronics&sr=1-3

Headlight:
https://www.ebay.com/itm/CREE-U2-30...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
Very bright, and has flash, low, high modes of operation.
I ditched the mount and bolted them to a plate that attaches to the handlebar stem clamp.
High-speed 12V cooling fan for battery box:
https://www.ebay.com/itm/Delta-DC-4...12SHB-Brushless-Axial-2-Wire-Fan/332071133493
 
How is the bolony fat bike fork holding up? Im looking to change my forks on my bike. I just street ride. Lot of waves and some minor pot holes on the road i ride.
 
I’ve had good luck so far with this fatbike fork from AliExpress. It’s similar to the ebay one you’re asking about. You can get it in all black which is nice. About $125 including shipping for the no remote version. It will accommodate tires slightly over 4”. I have bulldozers labeled at 4.7” and they fit because the tire is really only 4.3” wide on 80mm rim med-low pressure.
 

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1000-mile update.
Bike is performing as it did when I first road it in March.
Battery capacity is still 100% and motor is performing flawlessly.
My controller amp-max cutoff is 35Amps (measured), not 50-amps advertised.
Maybe I'll up it to 40Amps with a shunt-mod?
Fat-tire really absorbs road bumps/dips great!
I keep tire air pressure at 6PSI rear and 5PSI front. This is a great balance for 65lb bike with 175lb rider.
The few times I have taken rides on paved surfaces, I up PSI to 15 in both tires.
My typical ride is 35 hard-miles 100% off-road for over 2 hours. I stick to the forest roads and jeep trails.
I leave early and pack a lunch. Rarely ever see jeep-traffic.
I have never ridden it on a bike path (I have another e-bike for casual rids) and only ride hard-top roads to get between forest areas.
The Bolomy fork is holding up well. I have never needed to top-off air yet.
The frame is bullet-proof! Very happy with performance.
Most importantly, I have never been stranded.
I have taken several hard falls and each time bike was fine.
The worst crash was when bike endoed coming off a 6-foot drop (road washed out after flood).
Last week I crashed when right-side of handlebar was grabbed by a vine loop that was hanging from tree along trail. I was going pretty fast and got thrown over handle bars and bike went end-over-end.

Things I may do in future:
Get mud-fenders for back and front.
Add rear light....power it from existing 50V-to-12V DC converter.

My tool back-pack that I always take with me includes:
High-volume foot air-pump
Patch kit
New tube
Bike tool with all hex wrench sizes used by bike
Lunch and power-bars.
Water bottle.
Small sunscreen tube
Phone and ID and contact numbers to call if I am incapacitated.
Map of area I am riding.

What I wear when riding off road:
Blue jeans
Long sleeve shirt
Leather riding gloves
Quality MIPS bike helmet
Sunglasses w/rear-view mirror
Ankle supporting fitness shoes or boots.
 
Well that turned out great!

Couple questions:

Did you really get that frame for $150!!?! That’s a good deal if so!

Also, how are the cells put together? What are those insulators?

Again, great job on the build
 
Woods Fat-E-Bike in action.
25 miles of Jeep-trails ride video through Citrus Wildlife Management Area.
90 miles of forest roads, 50,000 acres.
[youtube]https://www.youtube.com/watch?v=v9e7vcZStVw[/youtube]
 
I have a Maltronics spot welder. Version 2 or 3?
Highly recommend.
I use a 3S3P 24AH LIPO pack to power it.
https://malectrics.eu/product/diy-arduino-battery-spot-welder-kit-v3-2-2-full_bundle_car_battery/
I dont recall paying this much though....they have gone up!
 
2000-mile update.
Bike is performing as it did when I first built it.
Battery capacity is around 90% capacity compared to new.
Motor is performing flawlessly.
Spokes have needed tightening on several occasions. Wheels rue up easily each time.
Rear tire is showing a bit of wear.....I need to rotate front with back tires.
I keep tire air pressure at 6PSI rear and 5PSI front. This is a great balance for 65lb bike with 175lb rider. I have had 2 pinch-lats on rear tire.
I up PSI to 15 in both tires when on road-trips
My typical ride is 30 hard-miles 100% off-road for about 2 hours. I stick to the forest roads and jeep trails mostly.
I have recently started ridding it on a bike paths for workouts (no e-power) when my road-bike is not with me (summer vacation trips I take ebkes, not road bike). I can average about 13 MPH for 2 hours at a time. On road bike I average 17 MPH for two hour rides. I was surprised that I could actually ride it on path without getting worn out.
The air-fork is holding up well. I have never needed to top-off air yet.
Most importantly, I have never been stranded!
I have taken several hard falls and each time bike&rider were fine.
The worst crash was when bike endoed coming off a 6-foot drop (road washed out after flood).
I was rear-ended by a pickup truck pulling a trailer while riding paved road back home from forest. Put me in the hospital. Bike handle bar snapped and broke right hydraulic brake lever. Frame got scratched up. Broke throttle and headlight.
I went down another time when right-side of handlebar was grabbed by a vine loop that was hanging from tree along trail. I was going pretty fast and got thrown over handle bars and bike went end-over-end.
 
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