Full Suspension Leaf Bike 1500W Build

[GoFastGus]

Hey y'all, I finally started on my second ebike build. I just pulled the trigger on a 2004 Kona Stinky Primo frame and a Fox DHX 4.0 shock off of Ebay (here's the original listing). $280 including tax and shipping, so not a bad deal if everything turns out to be in decent condition.

My current plans:
Motor: Leaf Bike 52V 1500W hub motor. I'm planning on a lower turn count, but I need more data about the relationship between a battery's ratio of Volts to Amps and the rpm per Volt of a motor in order to produce optimal acceleration.
Battery: Between a couple of options

1. Risunmotor 52V "45A" 20AH. ~$400 including tax and shipping. This battery appears to use DMEGC 50E cells, which are advertised as having 5AH of capacity and 3C of discharge. According to Batemo.com, these cells have a max continuous discharge of 8.91A and a max continuous power of 30.4W. This battery got me past 40mph on a hardtail, but I'm
2. EM3EV Jumbo Shark, ~$750 including shipping. Seems like the better option, but I need to learn more about it. All of their matieral on the page talks about the Samsung 35E version. The dropdown menu rates it up to 30A, but the marketing says it can discharge 40A continuously. If it actually could discharge 40A continuously, then that might be the pick for me. At the moment I'm leaning towards the 50A version. I assume it uses Samsung 50E cells, but I'd need to double check before I put any money down.

Controller: I’m leaning towards a Sabvoton 45A controller, or if I can't get away with 50A on a 45A controller, the 80A version. It would be nice to have a controller that had a motor temp sensor plug, or one that was programmable. Above all, it’s gotta be affordable and compatible with the other parts. I’m open to alternative suggestions.
Display: TFT 750C is my first pick. I’d settle for a UKC1. Getting a CA eventually would be wise, but it’s a lower priority.
Fork: Marzocchi Bomber 888 or Monster T. Maybe a Fox 40 if I can get a good deal on one.
Shock: if the DHX 4.0 doesn’t fit, I’ll need to find something with adjustable rebound only. It’s my understanding that coil shocks can take more abuse than air shocks, but I need to learn more.
Wheels & tires: 26” front, 24” rear with Hookworms. Probably at the limit of speed or grip with these, but DOT wheels and tires are another $200+
Drivetrain: easiest thing is bottom bracket pegs, but a single speed might be useful for a good 60’. Once again, low priority, will be taken care of later.

This bike will be 3 season streetable, but not a full on commuter. Still trying to decide if I want to do a back rack or anything. Let me know what you think!

 

[neptronix]

What's the top speed you're looking for?

I built this same bike with a 4T winding, but i had RC Lipos and therefore feeding the 4T copious amounts of amps was no problem.
You need a battery that can dole out 60A to feed that winding.

If you go with a 5T then a 3C 20ah battery and maximum amp limit is 45A might work okay.


I would gravitate towards em3ev becauese they use quality cells and construction techniques. They are much less likely to randomly blow up than a battery of average to low quality. The price differential more than justifies itself.

 

[GoFastGus]

What's the top speed you're looking for?

60mph is my hard max, that’s when I’d no longer trust bike suspension and brakes to reliably work.

I built this same bike with a 4T winding, but i had RC Lipos and therefore feeding the 4T copious amounts of amps was no problem.
You need a battery that can dole out 60A to feed that winding.

If you go with a 5T then a 3C 20ah battery and maximum amp limit is 45A might work okay.

Thanks for sharing your experience! If I’m running max 50A continuous from an EM3EV battery, it sounds like I want at least a 4T winding?

I would gravitate towards em3ev becauese they use quality cells and construction techniques. They are much less likely to randomly blow up than a battery of average to low quality. The price differential more than justifies itself.

That’s worth noting, thanks! Better construction and longer use cycles make for lower cost per mile?

 

[neptronix]

60mph is my hard max, that’s when I’d no longer trust bike suspension and brakes to reliably work.

That requires 8000W of power so you would need not only a bigger battery but way bigger motor.

Thanks for sharing your experience! If I’m running max 50A continuous from an EM3EV battery, it sounds like I want at least a 4T winding?

Maybe :/
This winding guzzles amps.. it'll probably do 40mph on a 26" wheel with 50v battery, consuming ~40A steady on the flats. The problem is if you have significant hills, the 50A max might not be enough.

If you do not live in a hilly area, it'll work well.

If you go with a 5T, you get a max speed is closer to 35mph, and 50a is plenty with accelerating, you'll probably use 30A cruising.

That’s worth noting, thanks! Better construction and longer use cycles make for lower cost per mile?

The main benefit is much lower chance for a random death metal pyrotechnics show, significantly longer battery life, and less hassles due to low quality.

One thing makers of cheap batteries do is fail to match the cells. That choice in itself ensures the pack will die early.

 

[GoFastGus]

That requires 8000W of power so you would need not only a bigger battery but way bigger motor.

That’s worth noting, thanks! Is it worth considering a second pack down the line to add more amps?

This winding guzzles amps.. it'll probably do 40mph on a 26" wheel with 50v battery, consuming ~40A steady on the flats. The problem is if you have significant hills, the 50A max might not be enough.

South central WI is mostly rolling hills, so I could probably get away with 50A, given the local topography.

If you go with a 5T, you get a max speed is closer to 35mph, and 50a is plenty with accelerating, you'll probably use 30A cruising.

Thanks for some more data! Does a 5T winding significantly improve the 60’ of a bike compared to a 4T winding?

 

[99t4]

Don't forget also that the motor is usually most efficient near its top speed (85% if I'm remembering correctly).

 

[GoFastGus]

Don't forget also that the motor is usually most efficient near its top speed (85% if I'm remembering correctly).

Leaf Bike claims a max efficiency of 90.5%, so I have high hopes.

 

[99t4]

The motor's efficiency varies over the RPM range, usually most efficient (peak efficiency) between 80-90% of its max unloaded speed (copper losses equal core losses).

I was trying to point out that your desired 60 MPH top speed means your 60 MPH capable setup will be running at lower efficiency at lower speeds (maybe the speeds you will be riding at most of the time?).

 

[neptronix]

Leaf Bike claims a max efficiency of 90.5%, so I have high hopes.

I have to be honest, this is a bluff. It's a rating in a 20" wheel, and this 9C clone type design was originally designed for 20" wheels.. which almost nobody runs. It's notably lower in a 26".

In reality you can expect a peak in the 87% range and an almost bizarre ability to continue ramping the speed up
But you will have to manage thermals!

I didn't even find the limit at 8kw because keeping the frontend on the ground was a challenge with non-FOC controllers back then.

 

[E-HP]

Thanks for some more data! Does a 5T winding significantly improve the 60’ of a bike compared to a 4T winding?

If you go with the 5T and higher voltage, it will be extremely quick, and demand less current.

 

[GoFastGus]

I have to be honest, this is a bluff. It's a rating in a 20" wheel, and this 9C clone type design was originally designed for 20" wheels.. which almost nobody runs. It's notably lower in a 26". In reality you can expect a peak in the 87% range and an almost bizarre ability to continue ramping the speed up

I was thinking about a 24" wheel, but I imagine my peak efficiency would still be around 87%.

But you will have to manage thermals!

I was planning on buying/making some ferrofluid and 3D printing a knockoff hubsink. At that level, battery and motor temp sensors are probably essential.

I didn't even find the limit at 8kw because keeping the frontend on the ground was a challenge with non-FOC controllers back then.

Why do non-FOC controllers struggle to keep the front end planted?

 

[GoFastGus]

I was trying to point out that your desired 60 MPH top speed means your 60 MPH capable setup will be running at lower efficiency at lower speeds (maybe the speeds you will be riding at most of the time?).

Sorry about that, that point flew right over my head the first time. I spent most of my time on my last build riding between 20 and 35mph, so I should probably try to get some data about what the motor's efficiency looks like at that RPM.

 

[GoFastGus]

If you go with the 5T and higher voltage, it will be extremely quick, and demand less current.

Once I get the frame I'll be able to mock up battery fitment better, but my guess is it will struggle to fit much bigger than a 52V downtube or a 60V triangle battery (I still need to find a good distributor for the latter). If I'm going beyond what a reputable manufacturer can make for me for under 4 figures, I think that a custom RC LiPo pack would fit my needs better.

 

[GoFastGus]

Got the bike frame last night! First off, it's a lot more red than I expected. Lots of scratches and paint nicks, but the welds all look ok.

Some basic frame dimensions:
Top tube: shock brain starts ~15" from the head tube welds, top tube is ~18.5" from the head tube weld to the seat tube.

Bottom tube: ~25" from the head tube welds to the opposite end of the bottom bracket, ~23" to the near side of the bottom bracket.

Seat tube: ~17.5" from the bottom of the bottom bracket to the seat post clamp. It's hard to see, but the interior tube to tube is ~12"

Parallel line to Seat Tube: ~9" between the inward-facing sides of the bottom tube and the top tube.

Therefore, I have a triangle about 9" by 15" by 18" where I can fit a battery. I need to make a cardboard template this weekend and measure everything out more precisely.

Speaking of, I've narrowed down my battery choices a little more.
For a 4T motor, I would go for a 52V 50A triangle battery from EM3EV. So far, it looks like this would fit, but I need to double check with a cardboard template.
For a 5T motor, I would go with a 72V 40A triangle battery from Grin. This one looks like it would get really close to the shock, so this one definitely needs a cardboard template.

Hub motor is gonna be this Leaf Bike wide 26" 1500W, unless I want to build a wheel. I've never built a wheel, but I think I'm going to have to learn how sooner or later.

Still trying to figure out a good fork. I've heard from relatives who are into biking to avoid forks with cut steerer tubes. However, I can't find a used fork without a cut steerer tube. Any advice about steerer tube length? I haven't been shopping for headsets yet, so I can only throw a shot in the dark about how tall headsets are.
Here's the head tube length: ~5.5"

Thanks for all the advice and information!!

 

[scianiac]

You might want to consider the bike geo depending on your speeds. My Leaf bike is a 2010 about giant glory DH and so was probably a fair bit more slack than that bike to start and I backed the rear shock way down and tied it to squat the back and slacken it out more. Feels pretty stable now although I don't go that fast, probably can do 40mph+ easy, 4T @ 72V but I feel more comfortable at around 20-30 I think. The 24/26 will slacken it quite a bit idk if a 24/27.5 would be too much but might be an option, depends how steep the HT angle is to start.

 

[A-DamW]

@GoFastGus are you totally set on a hubdrive?

This looks like a prime candidate for a left hand middrive Lightningrods setup.
You will retain all of the suspension characteristics, and be able to adjust gear ratios, and retain regen.

And if you use one of the larger motors, higher continuous power.

 

[phobos]

Still trying to figure out a good fork. I've heard from relatives who are into biking to avoid forks with cut steerer tubes. However, I can't find a used fork without a cut steerer tube. Any advice about steerer tube length? I haven't been shopping for headsets yet, so I can only throw a shot in the dark about how tall headsets are.

This frame has a straight steerer, not tapered, so you have to fit an older fork or get a headset with external bottom cup that fits a larger bearing supporting tapered standard. The external bottom cup will extend your headtube by ~2cm. Measure everything twice before buying and cutting anything.

I had to fit an uncut 26.5cm steerer tube fork with the tapered bottom cup installed and it reached the top of the stem within 2-3mm with one 25mm spacer.

 

[E-HP]

Got the bike frame last night! First off, it's a lot more red than I expected. Lots of scratches and paint nicks, but the welds all look ok.
View attachment 384718
Some basic frame dimensions:
Top tube: shock brain starts ~15" from the head tube welds, top tube is ~18.5" from the head tube weld to the seat tube.
View attachment 384719
Bottom tube: ~25" from the head tube welds to the opposite end of the bottom bracket, ~23" to the near side of the bottom bracket.
View attachment 384720
Seat tube: ~17.5" from the bottom of the bottom bracket to the seat post clamp. It's hard to see, but the interior tube to tube is ~12"
View attachment 384721
Parallel line to Seat Tube: ~9" between the inward-facing sides of the bottom tube and the top tube.
View attachment 384724
Therefore, I have a triangle about 9" by 15" by 18" where I can fit a battery. I need to make a cardboard template this weekend and measure everything out more precisely.

Speaking of, I've narrowed down my battery choices a little more.
For a 4T motor, I would go for a 52V 50A triangle battery from EM3EV. So far, it looks like this would fit, but I need to double check with a cardboard template.
For a 5T motor, I would go with a 72V 40A triangle battery from Grin. This one looks like it would get really close to the shock, so this one definitely needs a cardboard template.

Hub motor is gonna be this Leaf Bike wide 26" 1500W, unless I want to build a wheel. I've never built a wheel, but I think I'm going to have to learn how sooner or later.

Still trying to figure out a good fork. I've heard from relatives who are into biking to avoid forks with cut steerer tubes. However, I can't find a used fork without a cut steerer tube. Any advice about steerer tube length? I haven't been shopping for headsets yet, so I can only throw a shot in the dark about how tall headsets are.
Here's the head tube length: ~5.5"
View attachment 384728
Thanks for all the advice and information!!

I’d return it. Battery space is too tiny for a battery that a 4T would need unless you go lipo. What’s going on with those rear dropouts? They don’t look very beefy , and the left looks broken. It there a hanger? Does it support disc brakes?

 

[GoFastGus]

You might want to consider the bike geo depending on your speeds.

This is my first time tuning suspension, so I’ll take all the advice I can get.

I backed the rear shock way down and tied it to squat the back and slacken it out more.

Do bike tires benefit more from squat or antisquat when the suspension is loaded?

The 24/26 will slacken it quite a bit idk if a 24/27.5 would be too much but might be an option, depends how steep the HT angle is to start.

Head tube angle is 67° according to the 2003 catalog. Axle to crown length is 557mm. At this point I’m leaning towards a 26”/26” setup to start closer to square 1 with suspension tuning.

 

[99t4]

When working with your cardboard battery templates, don't forget to figure in at least minimal dense foam along the edges to protect the battery from vibrations and shock. Highly recommended.

 

[scianiac]

Do bike tires benefit more from squat or antisquat when the suspension is loaded?

Those are for the most part not relevant for a hub motor. What I meant was I lowered the rear to slacken out the fork even more to make it stable at high speed.

Head tube angle is 69° to my memory, I’ll double check. At this point I’m leaning towards a 26”/26” setup to start closer to square 1 with suspension tuning.

I wouldn't worry too much about suspension tuning, if you are actually going to be using it on really rough terrain no amount of tuning will make a hub motor that heavy ride nice and you should build a mid-drive. The effect the 24/26 will have on suspension will be basically nothing vs the change of head tube angle will be noticeable and at any speed over say 20mph you will want it to be slacker for it to be stable.

 

[GoFastGus]

This frame has a straight steerer, not tapered, so you have to fit an older fork

I’m currently looking at early 2000s Marzocchi forks, which are 1-1/8” straight.

or get a headset with external bottom cup that fits a larger bearing supporting tapered standard.

Is there a benefit to a tapered fork over a straight fork?

The external bottom cup will extend your headtube by ~2cm. Measure everything twice before buying and cutting anything.

Good advice!

I had to fit an uncut 26.5cm steerer tube fork with the tapered bottom cup installed and it reached the top of the stem within 2-3mm with one 25mm spacer.

Some good data, thanks!

 

[99t4]

Is there a benefit to a tapered fork over a straight fork?

• Extra stiffness and durability there at the bottom of the steerer tube and bearing which sees higher loads than the top.
• Allows for larger diameter downtube (more stiffness).
• Planned obsolescence.

 

[GoFastGus]

I’d return it. Battery space is too tiny for a battery that a 4T would need unless you go lipo.

I might have been able to get away with a bigger battery in a frame that has the shock mounted on the top tube. That being said, a strong head tube that could take a dual crown fork was a higher priority for me than battery space.

What’s going on with those rear dropouts? They don’t look very beefy , and the left looks broken.

They’re not beefy at all, I agree. Ideally, I’d like to make torque arms out of 1/2” mild steel and use grade 10.9 or 12.9 fasteners. The exact dropout and axle length of the motor will determine the exact specs of the torque arms. The left doesn’t look broken, I had the same thought. Its’s fully painted and my finger can’t feel any sharp edges as if it sheared. I’m inclined to say that’s just how they are.

It there a hanger?

No, but there is a place for one to bolt in on the right.

Does it support disc brakes?

Yes, the left side has a post mount bracket.

 

[GoFastGus]

When working with your cardboard battery templates, don't forget to figure in at least minimal dense foam along the edges to protect the battery from vibrations and shock. Highly recommended.

Good call! Is that still necessary if the battery comes in a plastic case and will be stored in a battery bag?