Cheap urban FS DD beater

D

daytonampco

100 mW
Joined
Jan 11, 2016
Messages
47
Location
Dayton, Ohio
I've got a serious lust for something fast and nimble to thrash on this season. Sadly, I don't have the budget for a mid drive, let alone a proper FS MTB to mount it on. So it's time for a zippy beater bike to ride off curbs, do small jumps, and ride to classes over degrading roads and sidewalks without feeling guilty.

I have some decent building blocks: a Yuyang King 60A Bluetooth controller from Luna, a cheap Mongoose FS MTB with functional disc brakes, and a 52V/20Ah Luna battery on my other bike I can stick in a backpack.

Enter the eBay $152 1kW generic 9C clone(?). Looks to be the same as my Conhismotor though the phase wires may be smaller/need upgrading. With the Luna controller downtuned to 50A it should scoot. Shipping info suggests it'll be here on Friday.

I'll use this thread as a general build blog once the motor arrives. I expect it to go together quickly with the most time spent on the controller wiring and setup.

Here's the donor bike: No, those 26x3 tires do not fit on the rear. But I had to try! :mrgreen: I will probably purchase some Hookworm 26x2.5's down the road.

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One nice thing about a cheap ass FS bike, that rear swing arm is steel. Weld new dropout plates on it lengthening it 2" or so, and then the 3" tire will fit. 8)

Run the motor at 2500w, and it should hold together ok, if you can limit amps to 40 amps it will overheat a bit slower without losing any top speed. This has become my power level of choice for fun street riding, 52v 40 amps/2000w. Top speed actually legal here, and plenty of perk without excessive short range.

On the other hand, if your planned rides are only about 8 miles per session, I would not hesitate to give it 60 amps. 3000w is about the limit for those type motors. I've run them a lot with 72v 40 amps, but in summer I got tired of cooking off the halls so I would run 72v 20 amps till cold weather returned.
 
FluxZoom, after a lot of googling, it is a Mongoose Snare, a $300 Walmart bike.

Dogman dan, my first thought when attempting to fit the tires last night was to extend the dropouts. My LBS is run by a really nice guy who does great custom work. I'll have to ask him about that since my welder is MIA at a buddy's. If it's not much more expensive than a $64 set of hookworms, I'll seriously consider it.

There are a couple hurdles to using those tires with my skinny MTB rims. The beads set okay in my garage but I don't know how they'd handle with lateral loads at speed. I've only tested the tires up to 20 mph on an old Worksman trike with wider wheels. Clearance is also an issue. Small deformations in the front tire cause the edge of the tread to rub ever so slightly on one side or the other. I can trim it safely but if I have or develop any bearing slop in the front hub it could be unusable anyways. The more I talk about it, the better Hookworms sound... :wink:

My other bike already runs 52V/30A (33A peak) without issue. I wanted to build something with a little (a LOT) more torque this time. 8 miles is actually my max ride around town. I'd love to push 60A but my Luna BMS is limited to 50A continuous, 80A peak. I'd rather not exceed 50A continuous for that reason.
 
Spinningmagnets, I will definitely take the ferrofluid tip. I plan to ride this bike much less conservatively than my other. I may as well upgrade the phase wires when I have the motor open. I guess I won't be pushing it that hard yet... Reasoning is found below.

It's a 14S7P Samsung 26f pack I bought before I knew much about ebike batteries, C ratings, or any of that fun stuff. I wasn't thinking about the fact that I should keep my battery draw limited to 40A to respect the limitations of the pack until you mentioned that.
 
Please don't ride a 2.5kW motorcycle on the sidewalk. I wish I didn't even have to say it, but evidently I do.
 
I won't be hooning the thing on a sidewalk. There a few points where I have to go on a sidewalk to avoid oblivious college kids more consumed with their cell phones than where they're going at 50 mph on a stretch of road known for continuous OVI's. I'd be riding a 50 lb bike at <10 mph on the sidewalk under human power at that point. No different than riding my road bike with loaded panniers except for saving myself some butt pain.

I understand your concern for the safety of pedestrians and those on the sidewalks but I only act a fool off of public pathways when there is no risk to anyone but myself.
 
daytonampco said:
I won't be hooning the thing on a sidewalk. There a few points where I have to go on a sidewalk to avoid oblivious college kids more consumed with their cell phones than where they're going at 50 mph on a stretch of road known for continuous OVI's. I'd be riding a 50 lb bike at <10 mph on the sidewalk under human power at that point. No different than riding my road bike with loaded panniers except for saving myself some butt pain.

I understand your concern for the safety of pedestrians and those on the sidewalks but I only act a fool off of public pathways when there is no risk to anyone but myself.
Click to expand...

How is this different from riding a GSXR-750 on the sidewalk at under 10mph? The pedals make it OK? :?:
 
We're now attempting to compare a 50 lb bicycle ridden under human power on a sidewalk to a 400 lb 200 mph sport motorcycle? The hyperbole astounds me.

That GSXR rider doesn't go hauling ass at 180 mph through suburban streets, they save it for the track. (I hope.) The rest of the time they operate it like a normal motor vehicle and obey the laws of the road. Like that rider, I will ride this like it is a normal bicycle and obey the laws set forth for bicyclists, including restricting my power until I'm in a situation where I can take advantage of it - off the road, in the woods, on private property, or on the trails.

FWIW I ride along with electric assist at 15-20 mph on surface streets 99% of the time and I don't use my motor on the sidewalk. I still fail to see how that's any different than riding my human powered road bike with loaded panniers that I can pedal up to 15-20 mph consistently. It is just as capable of being danger/nuisance to others if I ride like an idiot. It's my responsibility as the rider to be courteous, cautious, and maintain safe riding habits.

Let me pose this question: Would it be more okay if I were to ride a factory 90 lb 250w SLA ebike or my loaded road bike down the same stretch of side walk for the same reasons (dangerous stretch of road) simply because I can't turn on my phone and go "MOAR POWERRRRRR!!!"?
 
I'd like to clear up my position on ebike power. I ride safely and carefully on my ebike. I do not "hoon" on public paths, and no pedestrians or bicyclists are ever in any danger when they are around me. That being said...

I am constantly surrounded by 3,000-lb vehicles that are being driven by texting smart-phone zombies. Every single one of them will "feel" incredibly sad and embarrassed if they killed me by accident. If they only crushed my knees and hips, but still allowed me to live...I'm sure they would be equally concerned about the "incident".

When one of these vehicles comes near me, I want to have as much power as I can afford. My car can achieve a top-speed of over 100-MPH, and yet I have driven it in the various speed-limited streets according to the posted speed limit (typically between 25-75 MPH). The local police pass by me all the time when I am in my car, and on my ebike, and so far...they appear to be unconcerned.

I support safe behavior, but I will never support unsafe power limits. If someone hoons in a no-hooning zone, they should get a hooning ticket, not an over-power ticket.
 
So... you'd be cool with a hot rod Harley on the bike path, as long as the rider is appropriately slow and considerate? How about a dump truck?

If it's over the regulatory limit, it's a moped or a motorcycle. Every place has clear rules for those.

You might believe that the lane is no good unless you can break the speed limit like all the car drivers do, all the time. But in fact, real cyclists have been taking the lane with only muscle power to propel them, for longer than cars have been there to threaten them. Not developing a backbone isn't a public problem. Breaking a very reasonable law because you can't be bothered to develop a backbone is a problem, though, for more people than just you.

If we can't say no to motorcycles on bike facilities, what are we to say about 4WD trucks roosting in a schoolyard? Access is either something you can prohibit or it isn't.
 
While those baseless comparisons would make great news headlines they are far from rooted in the reality of the situation. Clearly this is an emotional argument and I am done taking part in it.

Back to building an e-bike!

Look! A frame with no wheels.

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These combination brake shifter units might present an issue with throttle fitment.

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Just don't ride your lame little moped on the sidewalk and we're cool.

Shifter pods like yours make more room on the bars for the grips. Otherwise, a bar with a bend that close to the end might not have enough room for everything. However, the shifter will foul the bar when it's adjusted to some angles, and that can be inconvenient.

I tend to use a CW style bar when I want BMX rise but have to fit MTB controls on it. Because the grip section of the bar doesn't bend, it allows much more room to fit things.
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The BMX bars for my lame little moped were leftovers in the garage. I'll try to make them work before I start throwing more money at it. Thanks for the idea, I may well have to go that route.

There is still plenty left to do:

1) Receive motor and check for damage
2) Hook up controller and pair with phone to determine overall functionality for initial setup
3) Purchase torque arms
4) Purchase statorade
5) Determine hall/phase wire combination
6) Upgrade phase wires (if they are 12ga like my other motor and I do not run it at my batteries limits I may as well wait until I get a more capable battery)
7) Shorten and solder wires and connections
8) Tidy things up
9) THRASH
10) Fix what I just broke
...
34) 26x2.5 Hookworms to help cushion the motor and myself

These tires will have to do until I have the hookworms. I kind of like the look but I might be the only one. :mrgreen:

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Those white-walled tires look pretty slick with the white fork. Looks like you'll have a comfortable upright riding position, should be a nice cruiser when it's finished!
 
I like to run those same tires on my street rides. Cheap, easy to replace without a trip to a bike shop, and just enough tread that when newer, they can go do a short bit of dirt road or shortcut on a dirt trail through a park ok.

Usually that tire is made by Innova,, then branded Bell, or whatever.
 
Thanks for the compliments on the ride eleven6 and nutspecial. I would have gone for 24" but the 26" kit was way cheaper than a 24" kit or buying a motor and spoking up a wheel. Maybe I'll look into that in the future.

Dogman dan, how do they hold up to bumps and potholes? I like them better than the knobbies but still think I might need more volume to hold up to a hub motor. I once cracked the rim on a front hub motor from a 1kW kit hitting a pothole on a standard Bell branded cruiser tire at 40 PSI.

On a tangent here but fiance has been telling me that she's interested in an ebike. Turns out the guy I sold my spare kit/Luna batt to is selling it on CL for $100 less than he paid. I'm buying it back tonight! :mrgreen:

Here's the build updates...

The phase wires on this motor are inadequate. Here they are next to the controller wires set up for testing combinations.

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Hall sensor test setup. Used a couple of pins/connectors from a burned up controller. I will shrink wrap the exposed bits before I start the actual testing around.

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Temporary power switch bypass using more bits from the burned up controller.

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Motor in the bike for hall/phase testing later on tonight or tomorrow. Having the second battery back will make this a lot less of a PITA.

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Update:

I borrowed my 52V triangle pack for initial setup. I paired the phone and found a throttle that didn't throw an error. I made sure phase and battery current were set as low as possible (50%) before I did anything. And... stutter!

I looked up a chart of all the hall and phase combinations from another thread on ES. I was on my 4th combination and got it! Well, sort of... I swapped the green and yellow phase wires and it ran right. The no load current was 1.4A and it was spinning in reverse. I switched the reverse setting to "negative" in the app and we are good to go! I calibrated it roughly and got an approximate top speed of 52 mph. I'll calibrate it properly when it's all put together.

Interesting tidbit: The second combination of phase wires I tried during testing was swapping the blue and yellow. The 9 year old walked out as I blipped the throttle and we both jumped when it spun up. The motor's max RPM had increased by 60% hitting over 80 mph according to the semi-calibrated speedo. The combination was not correct-the no load current was too high and it ran rough at low RPM. It consistently spun up with that configuration about eight times before it stuttered leaving me even more confused. I am not quite sure what happened to increase its max RPM so drastically. Did I accidentally do something crazy with the timing?
 
You hooked up a Luna controller per the wire colors and it just stuttered on the allinone ebay kit? That's a bummer.

I'd want to think Luna got their wires right, but allinone had probably sold hundreds of their kits too.
 
This controller is advertised as plug and play with a cyclone motor. I knew I could be in for a challenge when mating it up to any old eBay motor. I feel lucky since all I did was match up the halls and experiment with the phase wires. It could've been way worse.

I have the motor in the bike now with the brake and a 7 speed freewheel fitted (photos to come). I am currently working on attaching the controller and a project box for wiring to the bottom of a Schwinn seat post rack. I seem to have lost the spacers/shims since I used it on my last build... D'oh! Time to improvise...

Update:

Cleaned up all of the connectors I do not plan to use so I can fit the wires into a small project box.

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I chopped up some PVC pipe and fit the rack to the seat. I then mounted the controller to the seat and tucked all of the wires into the box. The small switch is power on/off.

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Here's the bike set up for initial testing.

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I ran the bike with my Luna 52V/20Ah Samsung 26f battery in a backpack. I used the small watt meter shown in the picture above. It has been relatively accurate when I tested it in the past. With the controller tuned to 50% power it peaked at about 25 amps draw according to the meter. I cranked it up to 80% battery and phase current and saw about 30 amps peak. I then got risky and tried 100% current setting and saw about 34 amps peak draw. Either the controller is overrated, my tiny phase wires can't handle the juice, or my battery is at its limitations. It did not feel any more powerful than my other bike. In fact, it felt a bit slower. That's okay though. Here's why:

My fiance asked me for an e-bike a little while back. This one is set up to be simple, comfortable, and light. It can be tuned down so that it is not excessively powerful. I should be good to mount the Luna Slim Line NCRB 52V/13Ah pack I just bought back this morning to the rack and let her go to town on.

I guess I'll save the excessively powerful build(s) for when I have excessive amounts of money to blow. I guess I'll be back in 18 years when all the kids are grown up. :mrgreen:

More updates:

Here it is as I was painting the controller a more subtle color. My other bike is a sleeper. This one won't be.

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Definitely not a sleeper. That battery looks so goofy on there. It looks like a cheap China bike now lol!

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Here's the other one for comparison.

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Final follow-up before a ride review this coming week:

This bike is now hers. I have the controller configured at minimum hall/battery current (50%) with the slow start set at maximum. It doesn't pull a full 30A from this battery either as configured either. Instead it settles in the low 20's at full tilt. That's okay. It's got plenty of power for her first e-bike and I won't need to modify it at that performance level.

Moral of the story: I've learned my lesson on cheaping out. If you want performance, just don't. If you want a daily rider or commuter, go right ahead! :mrgreen:
 
Don't wait 18 years lol! A little bit of lipo goes a long way- about 250$ can easily juice up an 18fet for some fun playtime! I just spent about that (already have 200$ in balance and bulk chargers), and they're happy (so far) with 7kw :shock:

It's a great 2nd ride or for the significant other, I just don't want to see you miss out on a desired 'thrasher'.
 
I've checked the pricing and availibility of LiPo's and see I can get serious range and power output for a lot less than my LiPO4's. But those LiPo horror stories on ES scare the pants off of me. I can't constantly monitor the batteries while charging. We have three kids and I am liable to get distracted for hours on end. Just seems a bit risky to me, even if I charge and store them in ammo boxes or the like.

My desired thrasher will probably be a FS mid drive of some sort. That is truly the direction I want to move in. I'm currently in the process of liquidating some rare old tube amps I've acquired and repaired over the last few years. When I sell off the majority of them I can afford to build or buy my own high powered bike with a decent amount of cash left over to fluff the bank account. It'll take a little while but I'm sure I'll be back to do it the right way next time. :wink:
 
One more little follow up:

We took our bikes around the block for a quick test ride. Apparently she was procrastinating trying it out. I'm guessing she didn't want me to be disappointed if she hated it. I was ready to strip all the e-bike parts off if she did, so no big deal there.

Early on the ride her story was that an e-bike defeats the purpose of bicycling because you don't have to pedal it. After went right up a difficult hill at 15 mph with power to spare she suddenly changed her story. That's a win in my book.

So much for the beater bike... but if the lady's happy, I'm happy.

PS - my bike with the 29'er wheels and 30A controller is definitely zippier than hers was with the 60A controller cranked to 100%. I'm just guessing the smaller phase wires on her bike were the main issue there. They'd get warm too fast for my liking with the controller turned up. Under minimum power settings they seem to do just fine so I won't be splitting it open anytime soon.
 
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