Mini Hiryuu - Mid power ebike

[neptronix]

Well, i've done it all on two wheels and have been off an ebike for 5 years lately because constant goathead flats defeated my will to ride. I moved to bikes with motorcycle tire compatible wheel sizes ( semi-recumbents ), but found all 3 bikes too difficult to electrify without serious fabrication. One problem after another.

Decided to go back to my roots this time and build something that isn't a motorcycle on a bike frame. Just an ebike for ebiking, until i have the means to build a hot rod recumbent.



So i've decided to take a cheap bike from bikeisland, and throw some parts at it. Except i want to iterate on my recipe from 2011.

Goals for this build:

- Stealthy look like my old build
- Enough power for 28mph continuous, with bursts to 35mph for safety when bike lane disappears and dumps me into traffic ( happens all the time out here )
- Significantly longer range for adventuring
- Substantially quieter
- Higher ride quality ( my main problem with the old hardtail )
- A lot more efficient ( My ol' 0.5mm lam MAC motor peaked at 83% efficiency back in the day )
- Better flat protection - willing to consume watts to move extra sealant/rubber, this is the only part of the efficiency of the bike we're willing to compromise.

Ingredients for the acoustic bike:

Bikeisland Gravity Basecamp: $138 shipped
Suntour NCX seatpost - $100
NOS Rockshox TK Solo Air 100mm - $130
Maxaraya BMX handlebar - $75
Long stem - $20
Comfort grips - already in the bike parts box
Aluminum cranks - already in the bike parts box
em3ev frame bag - already in the bike parts box
Kenda Journey K-shield Plus 26 x 1.75" + 1.95" tires - $80 shipped
Fat butt seat - $50

Total invested so far: $593



With all of the heavier parts of the bike replaced, the acoustic version came out pretty good, just about the same weight as my previous hardtail and does ride better so far.

Electric details forthcoming.

 

[skeetab5780]

Nice build! I like the KISS mentality when it comes to a commuter!

Love the classic old Watt meter on the top tube, i miss having that

 

[neptronix]

Yea.. i love simplicity too.. moreso now that spend 14 hours a day on the computer running a few companies' IT / Web dev departments. The last thing i want to interact with when i'm not on the clock is computer software, lol..


Ok.. electrics..

To maximize ride quality, we want the lightest motor we can get away with.
Normally, i'd go back a MAC, but the higher efficiency, lower weight, smaller profile, and lower noise of the Shengyi SX2 is super appealing.

The main concern is how much heat the Shengyi can shed VS the MAC. We know the gears and axle won't be as strong, so we can never push the motor as hard, but as long as we do 35mph on flats for a few miles when we need to, we good!

We don't have any thermal modeling on this motor, but construction is very similar to the MAC, so it's safe to say the way heat works in this motor is similar.



We're going to assume we can get an approximate idea about heat by subtracting 'batt power' from 'motor power', the difference indicating efficiency.

Let's do a couple comparisons on heat:

35mph top speed. MAC = 176W heat, Shengyi = 147W heat. Which one melts first? it's probably a tie because the shengyi has a smaller shell and axle for which to dissipate heat with.



Cruise speed, MAC = 97w heat, Shengyi = 73W heat, both should be able to sustain this indefinitely.



Hill climbing, MAC = 238W heat, Shengyi = 261W heat.... uh oh! neither can do this for long.



The Shengyi should be running a little cooler on the flats, so when it takes the hill, it has a head start on not overheating, but probably overheats in half the time as the mac in this climbing scenario anyway due to the smaller case/axle. :/

Let's try a 24" wheel and see what happens in that hill climbing scenario.
MAC = 217W heat, Shengyi = 227W heat, not bad!



OK, what about the 24" on the flats at top speed?
MAC = 176W of heat, Shengyi = 144W of heat.. these motors should survive it.



So by going with a 24" x 2.4" tire, we drop 34W of hill climbing heat off the Shengyi and 24w off the MAC.
It seems like some cooling modifications could make the Shengyi, for heat purposes, just as capable of a climber.

Ideas on how to improve the thermals

1. Throw ATF into the Shengyi. The Shengyi has better water sealing, so it's very possible i'd experience less dripping than most geared motors. I want to explore this last.
2. Heatsinking - geared motors shed a majority of their heat through the axle. It may be possible to put a heatsink on the axle and see a minor drop. There may also be some hot spots we can find on the case which would be ideal places to put additional heatsinks. It's worth firing up a thermal camera to find them.
3. Add insanely thick phase wires to help the motor heat wick out into the wires, not because we need lower draw.

#2 + #3 might be impactful enough to at least match the MAC. But the Shengyi Axle and case are smaller, so we need to do better than just removing 10 watts of heat. We probably need more like 25W out.

What about puncture protection in a 24" wheel?

This is a huge problem. We need a big 24" tire that is super puncture proof. The most puncture proof tires don't come in 24" sizes.

A few candidates for this:
- Schwalbe Pick Up 24 x 2.35" - 1150g
- Kenda Drumlin Cargo 24" x 2.4" - 1223g

Compare this to our choices in 26 x 2.0"
- Schwalbe Marathon Plus - 1100g
- Kenda Cargo - 1205g
- Kenda Drumlin KS-plus - 1371g

OK, we could use a Kenda Cargo, and a little sealant to make up for the rubber deficiency VS a Kenda Drumlin KS-plus. The only problem is, we may have a little higher rolling resistance than the KS-plus as a consequence of choosing a 24" because of that.

BRR seems to think the added rolling resistance is very small for sealants. But this is at bike speed, with a higher speed tire. We can probably think of this additional ~2 watts as more like 5 watts.

https://www.bicyclerollingresistance.com/specials/road-bike-tubeless-sealant

It may be possible to remove some of this extra sealant wattage by using a TBU tube or something like it. Worth trying because we need all the headroom we can get.

Conclusion

Shengyi SX2 on a lot of volts is the efficiency / power to weight ratio king it seems. I certainly want one
I want to give some credit to @tnoller5972 for bringing some good real world high power observations to my attention

 

[neptronix]

Ok, after much thought and re-calculations..

I have a lightest bike 1000w mid drive.. it's 3 lbs lighter than the SX2 and supposedly has high efficiency. Supposedly it's the power to weight champ of mid sized motors. Why not try it first eh..

Looks like the lightest mounts up on my bike with a 48T chainring.. i don't have ideal gearing in the rear ( 13T lowest cog ) but with some changes i think i can get up to 30mph on this motor and not have to worry as much about thermals when scaling a mountain/hill.



The one part that sucks is that it's gonna be noticeably louder and the stealth factor is pretty mid. I'm curious to see if that can be improved on.

Battery on the way to commence the build.

 

[nicobie]

Glad to see you back on a bike!

Congratulations, you'll live longer now.

 

[neptronix]

Thanks pardner.. i really need it!

After more thought and calculations i realized that on this bike the gearing that makes the lightest mid drive hit 35mph peak is going to continue to be elusive and frustrating. In addition, it has other problems that will require tinkering to resolve.

The SX2 is a really sweet motor but Grin doesn't have any rims with vbrake capability and regen would probably tip it over the edge, heatwise. I love the efficiency but it's cutting it too close to rely on regen braking to replace my rear brake. A headwind may melt it.

The GMAC is awesome but the rolling efficiency at mid speeds ( 30mph ) is ~85.5%. I could not get confirmation that the current batch of motors has 0.27mm lams and also which version was on the ebikes.ca simulator so i may end up with lower than 85.5% efficiency and that would suck.

Leafbike has a new 500w geared motor that's supposedly >85% efficient, but it's the weight of the mac and there's no dyno graph and specs don't seem accurate. My 'no specs, no buy' rule applies here.

The new all axle rear in a 24" cruises at around 86.7% efficiency @ 30mph on 52v. I get a couple extra miles out of this and have a great 'heat budget' for strong regenerative braking, meaning i can remove the mechanical brake like i did with this bike's ancestor and maximize the range i can get out of regen as a result.

I still want to run the lightest.bike mid drive on this bike once the long list of issues with it is sorted. But that may be months down the line and i must go and enjoy this very brief period of nice weather we get in Utah!

 

[99t4]

The SX2 is a really sweet motor but Grin doesn't have any rims with vbrake capability and regen would probably tip it over the edge, heatwise.

Don't they do their wheelbuilding in house? See if they'll lace it to a vbrake-compatible rim of your choice. Or buy the motor alone and you do the wheelbuild-- it's not that difficult.

 

[neptronix]

Don't they do their wheelbuilding in house? See if they'll lace it to a vbrake-compatible rim of your choice. Or buy the motor alone and you do the wheelbuild-- it's not that difficult.

They do. I looked at all their rims available. i was surprised to see none vbrake compatible. i'd have to ship them a rim which would increase the expense factor. sx2 is probably too wimpy for me anyway.

I've never done a wheelbuild, don't have the equipment, and don't have a local shop willing to work on an ebike wheel anymore. Just one of those things i don't do enough to invest in.

I ordered a triangle pack from em3ev and they came back with an email to me letting me know they have potted, UL certified 21700 packs now which they are just finishing final testing on. So looks like i'm getting em3ev's next generation battery. Way cool!

 

[Epithemeus]

They do. I looked at all their rims available. i was surprised to see none vbrake compatible. i'd have to ship them a rim which would increase the expense factor. sx2 is probably too wimpy for me anyway.

As someone who wants to order a motor from them (when I can budget it) and has V brakes I'm confused. All the rims I've looked at on the site say rim brake compatible in the specifications. Am I missing something?

 

[neptronix]

I think i have to say i stand corrected. Maybe.

A black wall is usually the sign of a rim designed not for vbrakes, therefore has a thinner wall and less heat dispersion as a result to save weight. This is the case 9 times out of 10.

The pictured rim on ebikes.ca's site has a painted wall and no wear indicator, so i'm not sure if there is a misprint in the listing or the image.



On Weinmann's website, the zac19 listing has no wear indicator, but a bare surface. They sell both a model for disc and one for vbrake.




Generally speaking none of the rims on ebikes.ca had a bare sidewall in the 24"-26" range and it looked from here we had no vbrake compatible rims in that category.

Doesn't matter to me, regen on the all axle in a 24" should be plenty strong.

 

[neptronix]

TBH if you are using regen who cares, electric brake > any kind of friction brake.

What motor are you looking into?

 

[Epithemeus]

Thanks for the info! I realized shortly after I posted that I don't need to worry though, forgot for a sec that I'm local to Grin so bringing my own rim isn't an issue Learned a bit more about rim brakes from your post though, this is my first bike with them since I was a kid and never thought about wear indicators.

I did the no rear brake only regen on a past bike, it's pretty nice not having that extra point of maintenance. I didn't even have variable regen and it still worked great. I don't really want to do that for this bike since I'm often hauling my kid in a trailer so I want to have as many braking options available even if in practice I don't end up using them.

Haven't decided for sure what motor I want and is partly going to depend on budget. I think I've ruled out the smaller geared motors like you because I want more oomph but other than that I think anything is game. You can be sure I'll be posting looking for opinions once I've got some cash

Now I'll be quiet so I don't derail your build thread

 

[amberwolf]

TBH if you are using regen who cares, electric brake > any kind of friction brake.

Well, for me, that would be true only if you have all of these:
--variable regen (most controllers don't, and are only on/off at full force of whatever they are factory-designed with, so it doesn't give the control needed for suboptimal traction conditions, etc)
--sufficient regen braking current to provide enough braking force to be able to lockup the wheel under maximum traction conditions, so that useful for your situation, etc.
--a form of electric braking that can use battery power to actively hold the wheel locked in place once stopped

Almost no regen brake I've used on either a regular bike or my cargo bikes/trikes has had anything like the kind of force or control required to replace an actual correctly-functioning mechanical brake (rim or disc).

Even the dual Phaserunners I'm using on SB Cruiser's rear wheels do not have the force needed, though that is probably more down to the limitations of the battery charging current, and they brake down to zero but don't hold the wheel locked.

 

[neptronix]

NP!

Super Hiryuu had 1kw of regen in the rear and a 203mm disc brake up front. I used the rear regen for easily 90-95% of my total braking. The oversized disc was there for just in the case of emergency if the controller or battery failed. If you really yanked on it, it could stop the bike alone at OK speed. I usually ran that bike around 40-45mph so it needed that powerful brake.

Keep in mind this was all street and only ridden in the dry so for offroad or rainy conditions you probably want variable braking or to limit the regen to right where the bike barely doesn't skid in adverse conditions and use the front mechanical brake more.

If your budget is thin i'd strongly recommend the RH212. It is a lot cheaper than the all axle and roughly as efficient. The extra poles give it more torque in a 26"-29" wheel than the typical 9C design. This higher torque means higher efficiency when climbing. it's lighter than the leafbike hub i used to run yet still has great overvolting capability.

If you have pretty flat roads ( isn't BC kinda hilly? ) and no expectations of >30mph then the SX2 standard winding in most wheel sizes on a lot of volts would be badass, not so much a torque monster but a speed monster for it's size.

 

[neptronix]

Well, screw me for ordering bike parts during the busy season.

Getting the em3ev battery 2 weeks from now.
All axle motor been in production hell, i would guess more 2 weeks.
Lightest bike mid drive parts? no ETA

Lesson learned: order things in jan/feb even if the rain/snow is unrelenting!

 

[Chalo]

I think i have to say i stand corrected. Maybe.

A black wall is usually the sign of a rim designed not for vbrakes, therefore has a thinner wall and less heat dispersion as a result to save weight. This is the case 9 times out of 10.

No, it's only a sign that the rim hasn't been machined after joining the ends. So it can just as easily be in indication that the sidewalls are thicker than if they had been machined.

The giveaway of a disc specific rim (or as I like to call them, coaster brake specific rims) is a sidewall that's curved, sloped, or otherwise unsuited to serve as a braking surface.

The pictured rim on ebikes.ca's site has a painted wall

If it's Weinmann and black and not specifically noted as having powdercoat, then it's most likely anodized (therefore suitable for rim brakes).

 

[neptronix]

I've read in numerous places that rim sidewall width varies based on a disc and non-disc version. It can be a few mm difference, which would have a substantial effect on how much heat you're making when braking.
Some manufacturers have different widths, some don't.

I wasn't willing to email both grin and weinmann to find out.

Anyway the grin wheel and em3ev battery both shipped today, yeehaw!

 

[neptronix]

Grin all axle in a 24" wheel arrived today.. looks fantastic and i love the weight of it



Still waiting for a battery from em3ev, can't wait to give this motor a spin!

 

[nervagon]

GRIN all-axle laced to a 24" should be pretty great. And that would be the config for my cargo bike, so I am very interested.

 

[Chalo]

Grin all axle in a 24" wheel arrived today.. looks fantastic and i love the weight of it

View attachment 351722

What rim is that?

 

[neptronix]

What rim is that?

Alex DM24.

 

[Chalo]

Alex DM24.

Badass. I wish I could still find any of those.

Back in the day, I used a pair of black DM24s in 24" to build up on drum brake hubs for a chopper bike for my sister.

 

[neptronix]

GRIN all-axle laced to a 24" should be pretty great. And that would be the config for my cargo bike, so I am very interested.

If you have a lot of weight to push you might want to consider the RH212... a 24" wheel is where it makes peak power/efficiency thanks to the taller stator and a couple more poles. Ideal option if you have a standard 135mm dropout an don't need easy wheel switchability because you don't live in flat tire hell like i do.

On the all axle, you could also send grin a 22" rim to spoke up and use a 18" moto tire or 22" BMX tire and gain some additional torque, which would get you very close to RH212 power levels but without the weight.

This motor is small but produces some amazing power in a 20" wheel; the closer you get to that, the better!

 

[nervagon]

If you have a lot of weight to push you might want to consider the RH212... a 24" wheel is where it makes peak power/efficiency thanks to the taller stator and a couple more poles. Ideal option if you have a standard 135mm dropout an don't need easy wheel switchability because you don't live in flat tire hell like i do.

On the all axle, you could also send grin a 22" rim to spoke up and use a 18" moto tire or 22" BMX tire and gain some additional torque, which would get you very close to RH212 power levels but without the weight.

This motor is small but produces some amazing power in a 20" wheel; the closer you get to that, the better!

141mm QR (boost for quick-release) dropouts, unfortunately.

 

[neptronix]

Bummer!