Mini Hiryuu v2

[neptronix]

I'm rebuilding my main ride again because small wheels loses me on a hardtail due to bad NVH with the crappy roads we have here. I want to run high tire pressure for maximum efficiency and range because i find

Lessons learned from small wheels ( 26" and under ):

1. Great power per lb of DD hub motor, however, mid drive or dual geared hubs is just as good, minus regen
2. Weight balance of bike matters, >10lbs in the rear end = wagging, hard to handle, easily cross 70lbs, starting to become burdensome, evenly divided or central weight is so much better
3. Tire selection is limited but not stifling, great selection of thick tires, but ~100w of loss though, better to accept the use of sealant and use tall tires to minimize rolling resistance
4. Low tire pressure = big efficiency loss, big problem for a long range ride with today's battery technology, not an acceptable compromise to improve NVH
5. Seat post not good enough to provide large improvement on NVH on a hardtail, larger wheels is the better answer, add seatpost and it's even better

Therefore, in order to comfymaxx a cheap frame, the lowest path of resistance is diametermaxxing

The basis of v2 is a 21" size Motobecane Fantom Expert 29" from BikesDirect.
It's not light, but it's cheap ( $500 new shipped ) and has good geometry.



Wins on this bike:

1. 460mm chainstays; puts the rider a bit closer to the front wheel so the front susp can help a tad
2. Long reach means i can put more of my torso on the handlebars, this means also that a small front fairing would work
3. Fits a 50mm seat post
4. Lower than usual bottom bracket = better center of gravity and okay for the mostly street riding i do
5. Large reduction of un-suspendable road judder on bad roads vs 26", major improvement to rider's quality of life.

Problems with the bike:

1. 20mm internal rims are a poor match for the stock 29 x 2.25" tires so i will downgrade to 29 x 1.75
2. Fork too hard on the lightest setting, front NVH suboptimal. need an air fork again

Powertrain plan:

• Goal is to be able to sustain up to 35mph on semi-flat ground whenever needed and accelerate briskly, on 9-10lbs of total motor
• em3ev 52v 20ah batt
• Lightest.bike mid drive @ the currently crippled 900w power limit - may run external controller for 1400w since warranty's expired
• 4-5lbs super low turn count dual reduction geared hub on the front wheel at 350w max for nice safety margin on an aluminum air fork & no hub -> cassette interface shearing potential, AWD is bonus

Challenges to solve:

• Does a 4-5lbs front hub hurt front NVH?
• Effective front fairing
• Maybe tail fairing
• Perfect middle ground between minimum amount of rubber in sealant for adequate goathead resistance

More as it develops

 

[neptronix]

Okay so how is the bike going? Not great!

Weather has been total ass out here and i've only been able to ride a few times in the last 30 days.

I was bending these power pins on the lightest bike mid drive unit again so that they had tension against the connector wire, and the positive pin snapped, and can't easily be replaced. So now that motor is due to be modified for an external controller.

In the meantime, i think the weather will improve soon and i just need a motor. I spent all weekend trying to find a spoked up cheap ~500w geared hub and found that the USA market keeps getting more sparse. Can't find a 700c wheel geared motor that takes a disc brake in all of ebay either. Super frustrating.

Wanted the ebikes.ca Shengyi SX2 but even the standard winding is a little too fast for my 52v battery and the 29er wheel. I wanted something that did more like 25mph.

Somewhere in this extensive search i find that johnny nerdout has a shop now, so i bought a bafang kit from him:
https://www.johnnynerdout.com/product-page/hub-motor-wheel-kit-750w

 

[neptronix]

The kit arrived in 3 days, and i'm impressed with what i get for $350 shipped.



Even includes a light with some LEDs that look like a CREE type ( very powerful )



Wheel looks true out of the box - a rarity for cheap kits.
Motor wheel weighs 9.25lbs.
Spokes are 13 gauge - nice
Motor spins up to 30mph unloaded on a 52v battery with the wheel set to 28", that means loaded top speed should be ~25mph.
Controller has a super slow ramp up which is kinda annoying but not unexpected.
Display has 9 power levels and is cool looking.

A lot of bang for the buck, i see why bafang is popular!

 

[neptronix]

Up the short test track..



At 75% state of charge, and power level 9, i can hit a top speed of 26mph without pedaling. ( GPS verified )
With fervent pedaling and being in a tuck position, i can get up to 29mph on the flat.
Up a 4% grade, the motor slowed down to 25mph while pedaling fervently, but didn't get hot or warm over this short stretch. ( not a great test though, it's 45f outside )

The motor can draw up to 900w, according to the screen. This makes it equivalent to my firmware-hobbled mid drive.

Acceleration wise, i'd compare it to the lightest bike mid drive. It is pretty strong considering the tiny 18A controller.
It's 2x heavier though and feels like a serious downgrade in that aspect.
The throttle has a ~2 second delay between the time you twist it and the time it does something. Extremely annoying.
The motor is pretty quiet, reminiscent of a BBS02.

I think this might be a good candidate for running with a phaserunner, to dramatically improve the power delivery.

Once the temps get up, i'll take it up a long gradual hill that makes up the secondary test course and see how it manages thermally. If it shines, i might convert it to being controlled by the phaserunner.

 

[neptronix]

Side note about the comfort factor.

Going from a 26er to a 29er was a big upgrade and i'm glad i modernized.
I can pump the rear tire to 60psi and only start paying for it in the mid 20mph range on our local crappy roads.
That high tire pressure and narrow tire on the rear also = great rolling efficiency.
On a 26er it was always a tradeoff between NVH and efficiency, i could only tolerate 45-50PSI on the rear, and i lost a few MPH to that.

On the front, the low grade springer fork starts to handle like crap in the upper 20mph range but that's impressive, i can tell that upgrading to an air fork will have a huge impact and the frontend should be serene.

What sucks about these big wheels is that you lose torque with DDs and you can say goodbye to an appreciable amount of that motor's continuous power handling. So the most sane choice is geared motors or mid drives with wheels this big.

 

[99t4]

The throttle has a ~2 second delay between the time you twist it and the time it does something.

That would be a deal breaker for me. How do you even compensate for that? What could be the reason for it?

 

[neptronix]

That would be a deal breaker for me. How do you even compensate for that? What could be the reason for it?

I don't know. it's your ever present horrifically bad OEM tune that somehow became industry standard for the last 2 decades.

It has one job: be a motor that runs when my experimental mid drives fail me

 

[amberwolf]

The throttle has a ~2 second delay between the time you twist it and the time it does something. Extremely annoying.

Even the crappiest controller I've ever had didn't have that problem. Does it also take 2 seconds to release throttle?


I did have one that had extreme (>0.5s) delay responding to ebrake input (either pull or release), which made it too dangerous to use. (brake response should always be instantaneous)

All of the PAS-controlled ones have far too much delay responding to start or stop of pedalling (none of them do anything but on/off of full at the chosen assist level, unlike the way the CycleAnalyst does things), and those also have delay in brake response....but their throttles all respond "instantly".

 

[slaphappygamer]

I have that light too! It came with my turn signal kit. I like it! The light is pretty wide. I've been thinking about moving my light to the handlebars to get a bit more distance and less front tire shadow.


Mine also has a horn. Maybe yours does?

 

[bananu7]

Even the crappiest controller I've ever had didn't have that problem. Does it also take 2 seconds to release throttle?


I did have one that had extreme (>0.5s) delay responding to ebrake input (either pull or release), which made it too dangerous to use. (brake response should always be instantaneous)

All of the PAS-controlled ones have far too much delay responding to start or stop of pedalling (none of them do anything but on/off of full at the chosen assist level, unlike the way the CycleAnalyst does things), and those also have delay in brake response....but their throttles all respond "instantly".

It could just be a very, very slow ramp-on time meaning you don't feel much until a while later.

@neptronix does the display have a throttle icon? Does that icon come up immediately?

 

[neptronix]

Even the crappiest controller I've ever had didn't have that problem. Does it also take 2 seconds to release throttle?

It's kind of funny, it gives maybe 5% power for ~1.5 seconds then gradually ramps on power to 100%.
Power turns off in 0.25sec when the throttle is released.

I did have one that had extreme (>0.5s) delay responding to ebrake input (either pull or release), which made it too dangerous to use. (brake response should always be instantaneous)

Damn.. i have not tested ebrakes yet.. also haven't tested PAS.. i expect it to be laughable

I have that light too! It came with my turn signal kit. I like it! The light is pretty wide. I've been thinking about moving my light to the handlebars to get a bit more distance and less front tire shadow.

Mine also has a horn. Maybe yours does?

No horn, so jealous!
The light, it's meant to be mounted on a suspension fork's crown, no? I was thinking also the handlebar would be a better place so that cars know i am behind them at night.

@neptronix does the display have a throttle icon? Does that icon come up immediately?

No icon.

 

[amberwolf]

It's kind of funny, it gives maybe 5% power for ~1.5 seconds then gradually ramps on power to 100%.
Power turns off in 0.25sec when the throttle is released.

Well, that's better than no response at all for two seconds. Not by much, but...it means it is doing *something*.

It could be software, in which case you might be able to change it with the programming tools (I'm sure they're posted around here somewhere if it's possible with the controller you have),

But it could also be a simple low-pass-RC-filter on the throttle signal line, with a pulldown resistor on the controller side of that (to ensure it drops quickly when released). Thta would be easy to defeat, simply removing the capacitor (which would normally go to ground from the signal line); the series resistor and the pulldown resistor wouldn't need to be touched.

Damn.. i have not tested ebrakes yet.. also haven't tested PAS.. i expect it to be laughable

I'm sure the PAS is the usual on/off only crap, that just gives you the full output of whatever assist level it has. Other than the OSFW for certain controllers, and maybe VESC, the Cycle Analyst is the only way I know of to get variable-cadence-assist with a DIY kit not using a torque sensor, just a cadence sensor.

No horn, so jealous!

The "horn" on my Fusin kits' display/light module was...laughable. It was a piezo buzzer that would've been outshouted by the roadrunner with it's head wrapped in three feet of cotton. :lol: I don't think anyone other than the rider could've heard it, and not even that in traffic or with any wind noise.

mp mp

 

[neptronix]

Honestly it's a temporary kit while i build up the nerve to drill into my lightest bike mid drive, not worth improving!

 

[slaphappygamer]

No horn, so jealous!
The light, it's meant to be mounted on a suspension fork's crown, no? I was thinking also the handlebar would be a better place so that cars know i am behind them at night.

Yes. I mounted my light on the crown. I’m sure I can get creative and mount it to the handlebars.

The horn is kind of dinky. It’s probably in the light, but not wired up. I got a horn like this one…




…and wired it in instead of the dinky horn. This horn is amazingly loud for its size and gets attention. I haven’t reinstalled this since moving to cycle analyst/baserunner, but I’d really like to install this in my frame and hide it. I feel it’ll be loud enough even inside the frame.

 

[neptronix]

Checking in!

Ditched the old torque arm for a new 12mm grin unit so that i can have easier innertube changes and much less torture on the dropouts w/this small 12mm axle.



It's a nice 63F outside and the pollen has finally calmed to the level that i can tolerate.
Gave the Bafang 500w a nice torture test up some long 1-2% grades and short 5-7% grades, with only light pedaling.
Cycle analyst standalone on the 500w bafang kit says the max amps is 17.5A +/- 0.25A while hill climbing; about 900W average.

Couldn't feel any heat on the motor casing after a few miles of that + giving it 5 min to let stator heat soak outwards to the case.
My cheapo FLIR measured 97 degrees F or 36C
This is ideal bike riding temps, but.. i think the motor may be able to handle 20A, even as things get hotter.

And in typical Utah fashion, this regular 'puncture proof' bike tire went flat after the 3 mile ride. I'm off to order some Kenda Drumlins now.

 

[amberwolf]

And in typical Utah fashion, this regular 'puncture proof' bike tire went flat after the 3 mile ride.

need more rubber between your air and all that crap on the roads.

 

[neptronix]

need more rubber between your air and all that crap on the roads.

No kidding. Also for comfort purposes, more rubber = more better.
Kenda Drumlin or Journey are a nice middle ground, almost roll as fast as Schwalbe, but have much better ride quality.

The only thing that's off the table is the Kenda k-shield plus. Those things ride super smooth, but are heavy as sin, and eat something like 100 watts at 30mph versus a regular tire.

It looks like Stans has really low added rolling resistance. A switch to an expensive TPU or Latex tube would delete the added wattage loss. So that's cool.

Ref ( 25mm tire, 23mph ): TESTED: How Tubeless Sealant Affects Rolling Resistance

 

[2old]

Good luck and get ready for the recently released (on a bigger scale than what's been available to date) 32" systems.

 

[neptronix]

Good luck and get ready for the recently released (on a bigger scale than what's been available to date) 32" systems.

I've been mad about that ecosystem being underdeveloped for a decade now. I'm ready!

What would be better is to see 750d gravel/road tires be developed.. you could fit an existing bike that accepts 29 x 2.4" with these, if you run something like a small gravel tire... but every manufacturer of tire and rim won't sell anything.

 

[99t4]

DIY rear brake caliper mount spacers?

 

[neptronix]

DIY rear brake caliper mount spacers?

Yep, to counter the axle offset -> disc spacing problem inherent with this kind of axle.
With a proper 180mm adapter, i was only getting half of the brake pad to contact.