Sunder's Damn the Torpedoes Build

[Sunder]

Well. It's finally happened. I'm admitting I'm wrong. The Q100 328rpm isn't suited for a 700c, 1kw build. Yes, people told me this, but for 4 and a bit months, I sat smug on my 45km/h bike, that cost me loose change.

It lasted me 5 months, but finally, something has broken (most likely the gears or the clutch, given it still works, but now vibrates like something best kept in the bedroom). Given Cheap, Fast and Reliable. I chose cheap and fast, and while I enjoyed it for 5 months, I can't use a bike for a daily commuter if it's going to break randomly every 4-6 months, which is what this build has done. (Last motor also lasted about 6 months, then burned a winding)

So given Cheap, Fast and Reliable, I'm now choosing Fast and Reliable and damn the torpedoes. So, I need your help to help me design my next build.

Budget Excluding Battery - $2000
Hard Limitations - Must use my existing 12S batteries, must use my existing frame
Preferences - Geared rear motor hub, small and silent as possible. 1250W daily, so designed for 1500w+

My first thoughts were:
Bafang SWXH - Oil filled. Buy two. One for immediate use. One to modify for later power upgrades. ($300?)
2kw Sinewave controller (??)
Cycle Analyst ($300?)
Thun Torque Sensor ($350?)
Zipp 808 Rear, 404 Front Carbon Fibre Wheels ($600)
Miscellaneous labour and parts (Wheel building, cover removal tool, spare clutches etc) $200.

That should come close to $2k. If it goes over by a couple hundred, I don't mind as long as there's a reason.

Technical Justifications - If I can somehow program the CA and the Thun sensor to make me move say 2-3km/h before applying any power, then the stress on the gear/clutch should be substantially reduced. Since I want to do some long (70km) high speed (45km/h+), low incline rides, and I want to get fit, then having a Thun sensor can help me manage my power usage, and I can gradually reduce my dependence on the battery.

How would you improve this? I want to order by the end of the week, as the bike is annoying the crap out of me, even though I can keep riding it. I appreciate any input, as this time I will listen to anyone who has proven experience in any of these technologies, rather than try to prove them wrong for a few months

Thanks in advance.

 

[Drunkskunk]

Forget trying to make those cute little motors do the job of a big motor. To handle 1000+ watts of power, you need a motor that can take that abuse. A Mac or BMC 500w is the place to start.
The rest of you plan sounds fine

 

[Hillhater]

Why geared motor ?
If it were me, and looking for reliability, i would keep it simple ( less chance of problems)..
so, go with a DD hub...more reliable and quieter.
forget the torque sensor..not needed !
Not waste money on CF rims ( you have a heavy motor in there anyway) and they are just "show pony" kit on a commuter.
CA.. if you feel the need.

Spend the saved cash on a spare wheel/motor and controller,.. ready to swap in incase of any problems.
:wink: :wink:

PS ..we all learn from our mistakes.
I think you should first investigate why your geared motor failed ( It may just be some damaged wiring) .. before you go off in a new direction.

 

[Sunder]

Noted. That's one option, though I don't really like the extra height and 2kg it has over the SWXH.

It's also more expensive, with one shipped from Cellman being more than two of the SWXHs.

Does anyone have any experience pushing the SWXH over 1kw? There are guys on the internet who have pushed it to 1500 regularly, and 1800 for short periods, but even they admitted metal shavings in their oil after 1000km.

 

[Sunder]

Why geared motor ?
If it were me, and looking for reliability, i would keep it simple ( less chance of problems)..
so, go with a DD hub...more reliable and quieter.
forget the torque sensor..not needed !
Not waste money on CF rims ( you have a heavy motor in there anyway) and they are just "show pony" kit on a commuter.
CA.. if you feel the need.

Spend the saved cash on a spare wheel/motor and controller,.. ready to swap in incase of any problems.
:wink: :wink:

PS ..we all learn from our mistakes.
I think you should first investigate why your geared motor failed ( It may just be some damaged wiring) .. before you go off in a new direction.

Size and weight is the main issue. Right now, very few people can tell I have an electric bike. It only weighs a little more than a bike some stuff in the panniers.

If there was tiny direct drive motor about the same size as a geared hub, I'd even take a cut in power to make it work.

Also, at 45km/h, 50mm rims save about 8-10% power as compared to 15mm deep rims. It's not a lot for a powered bike, but considering how fast efficiency falls off at high power levels, I thought it could make a bigger difference, and make the motor more reliable. I'm not doing it for weight. I'm doing it for aerodynamics, but I am easily negotiable on that part.

Why do you feel the torque sensor is not needed?

Thanks so far for your advice. Right now I'm leaning towards a Mac Motor, as an 8T would be perfect, but the weight and size is still getting to me.

 

[Hillhater]

Why do you feel the torque sensor is not needed?

An unnecessary complication...Keep things simple for reliability.
Why do you feel you need one ?

 

[neptronix]

If you want the smallest and most powerful hub motor, get the greyborg / zelena volzila 800w unit, or get a Q128H, which is rated at 800W officially, double the power of the Q100.

It's not a very efficient motor, but it is the most powerful hub motor for it's size at the moment. Dyno sheet is attached.

A MAC motor would be dramatically better than these small geared motors though. No problem going 50km/hr and above, with tons of torque and high efficiency while you beat on it since it was designed to pull that power from the start.

 

[Sunder]

Why do you feel the torque sensor is not needed?

An unnecessary complication...Keep things simple for reliability.
Why do you feel you need one ?

Smoother delivery of torque, as there will be a relationship between how much the chain is pulling, and how much the motor is pulling.

 

[Sunder]

If you want the smallest and most powerful hub motor, get the greyborg / zelena volzila 800w unit, or get a Q128H, which is rated at 800W officially, double the power of the Q100.

It's not a very efficient motor, but it is the most powerful hub motor for it's size at the moment. Dyno sheet is attached.

A MAC motor would be dramatically better than these small geared motors though. No problem going 50km/hr and above, with tons of torque and high efficiency while you beat on it since it was designed to pull that power from the start.

Now that's one I hadn't considered. Rated at 800W, it should take short bursts of ~1250 Easily. Thanks.

The thing is, I don't think I really need something the size of the Mac motors, even though it would be nice. If a 350W Q100 can do 1kw for 5 months, then surely the Q128H can do 1kw safely, with short bursts up to 1250w.

 

[DAND214]

No comment on the Cute128h or any of the Cute.

Dan

 

[Samd]

If you were running 15s I'd say there's new BPM in my shed down south that arrived Friday you can have for $250 plus freight - it's not much heavier than the SWXH and it'll live happily on 1500 watts / 45kph.

Are you running 700c wheels?

 

[neptronix]

The difference between a big motor and small motor will be seen in power in versus power out. For your Q100, giving it 1000W was not getting you anywhere near even 700W when pushed that hard. A good fraction of that power was being made into heat, and you weren't getting anywhere near the range possible.

If you're gonna be cheap, go with the BPM that the fella above is selling. It's not the best motor for tall wheels, but it'll be an improvement. You'll get a lot more power to the wheel per watt inputted.

The big downside to the Q128H is it's 145mm dropout requirement. You could remove one of the nuts one one side, shave 7mm off the other, and drop it into a 135mm dropout if you kept to say, a 5 speed freewheel however.

 

[Sunder]

Okay, so to sum up:

MAC 8T would be the best technical solution, but poor on the handling and aesthetics. It's 2.2kg heavier, and about 5cm taller, meaning it can no longer hide behind my freewheel.
Q128 would just suit, but I need to modify my dropouts. Probably not possible.
SWXH would also just suit, but there are some known issues with the clutch running at 1500kw+ so might not improve reliability anyway. However, I could get around this by having two wheels, essentially a "warm spare", as well as some spare clutches.

There is one last option. My wife wants me to try dropping off the power to sub 750w on a Q100, and gaining efficiency rather than power. (So better wheels and tyres, possibly better drive train, and shift to drop bars) I think she prefers I don't try to keep up with traffic, especially when I have our son in the baby carrier.

To be honest, I'm personally kinda torn between the Mac 8T and the two SWXH. However, I know that happy wife = happy life, and it might be worth destroying another Q100 just to eliminate that option and keep her happy.

 

[neptronix]

The worst option you should chose should be a Q100H, as it's more powerful.
Q128H does not require modifying your dropouts if you modify one side of the axle.

How about dual Q100H's? put a disc brake on the front one to help hide it. About the size of a small drum brake or generator anyway.

 

[Sunder]

The worst option you should chose should be a Q100H, as it's more powerful.
Q128H does not require modifying your dropouts if you modify one side of the axle.

How about dual Q100H's? put a disc brake on the front one to help hide it. About the size of a small drum brake or generator anyway.

Sorry, help me understand this? Q100H is more powerful, how does that make it a bad choice? If I survived 5 months with a standard Q100, wouldn't a slightly more powerful Q100H be better?

 

[neptronix]

It's the worst choice because you are still abusing a small motor so far past it's design and therefore it'll be disposable just like your last motor. Maybe it'll be headed to the junk bin in a longer period of time though

 

[Sunder]

It's the worst choice because you are still abusing a small motor so far past it's design and therefore it'll be disposable just like your last motor. Maybe it'll be headed to the junk bin in a longer period of time though

Ah, so it'll take longer to prove to my wife that lowering the power isn't work Got ya

 

[-dg]

I think the BPM is the motor for you. None of the little motors will handle that kind of power level and be fully reliable. The MAC will, but is a bit big, a bit loud, not really discrete. The BPM is very efficient, almost as strong as the MAC, and just enough smaller and quieter to not scream, hey, e-bike coming through. Although if you are going 45km they will probably be onto you anyway. Btw, a new BPM is about $125 plus probably $70 shipping from China, so $250+shipping seems kinda high.

A code 10 BPM should work out about right.

As for rims, get any style aluminum rim you like. You can get aero enough for hundreds less. You may also find it hard to find 36 hole drillings in carbon rims. Personally I don't believe carbon fiber is a suitable material for safety critical consumer products. It's no big deal if your tennis racket breaks. Aircraft have stringent inspection protocols. Bikes don't get inspected and get a lot of abuse too.

I think your real problem may be finding a suitable controller, all the sine wave controllers I've seen are smaller. Let us know what you find.

 

[Sunder]

As for rims, get any style aluminum rim you like. You can get aero enough for hundreds less. You may also find it hard to find 36 hole drillings in carbon rims. Personally I don't believe carbon fiber is a suitable material for safety critical consumer products. It's no big deal if your tennis racket breaks. Aircraft have stringent inspection protocols. Bikes don't get inspected and get a lot of abuse too.

I think your real problem may be finding a suitable controller, all the sine wave controllers I've seen are smaller. Let us know what you find.

Thanks for your input. For the time being, I'm trying a 800W sinewave controller with a Q100H with a spare prelaced wheel. I'm reusing the current rim I have for one motor (622 x 30 with a 37mm tyre, 25mm tall) and a 622 x 15 with a 23mm tyre, 50mm tall (aluminium) for the spare. Budget has been severely reduced, but I will still have a workable bike.

It seems while I may have damned the torpedoes, the wife dropped some depth charges If this doesn't suit, then later in the year when we have a bit more cash, I can do the build as I originally wanted.

 

[wesnewell]

Sorry to be so late to the party, but the thread title just didn't get my attention. I don't know what you call fast and cheap, but these are reliable motors. I've got over 16,000km on mine and been running it on 24s lipo (on 72V controller) for the last 22 months up to 70kph for short runs. And they're in Sydney. Take you're pick of many they have.
http://www.ebay.com.au/itm/Electric-Bicycle-E-Bike-Conversion-Kit-Cycling-48V-1000W-Rear-Wheel-LED-Light/130824344528
http://www.ebay.com.au/itm/Electric-Bicycle-E-Bike-Conversion-Kit-Brushless-Motor48V-1000W-Rear-Wheel-Rack-/150956506830