Looking for opinions for next build: low power 52V daily

[daytonampco]

I have an old road Sentinel Whisper road bike that I positively love riding. I've done thousands of miles on the bike, jumped many curbs, and worn out the final gear on the rear cassette from speeding with traffic through Columbus in my early 20's. I'm not as good as I once was but I would like to bicycle more often. I face a four mile ride to both work and my final EE night classes with rather significant hills in between. I'd prefer to not end up drenched in sweat when I reach either location.

That said, I will also be doing a lot of flat land riding in my free time. I am not sure if I should look for a mid drive or hub motor. I would ask for the opinions and experience of those who have used both to help me decide what to do. My ideal power range is 250-350W.

Experience:

I have already built a ridiculous e-trike (RIP) and a silly fast 1500w 29er e-bike with a hub motor a lot of storage for roaming through the nearby woods. I have extensive electronic experience in competition car audio, SMD amplifier repair, and tube amplifier design and repair. I am a decent programmer as well. In short, I am not afraid to piece something together or modify something to save a few bucks.

The Problem:

#1: I am stuck using my spare Luna 52V 14s battery pack that fits neatly in my backpack. It maxes out at 58.8V on a full charge. As far as I can tell, this is my main restriction on set-ups available.

#2: I am stuck on using the stock size 27" (630mm) wheel so I do not need to change anything on the bike. It stops and handles great even with 20 lbs of groceries on my back.

Goals:

Minimize cost: I am working on my second degree, working, and have all the adult responsibilies - a house, a fiancee, two kids and one on the way.
Minimize weight: I want it to feel like a bike!
Minimize drag: My 29er is hard as heck to pedal and close to 100 lbs! I want this one to still feel and handle like a bicycle.
250W draw: I only need help on the hills. I do not really want or need any more than 10A draw.
Utilize PAS and hand controls if possible

Options:

Bafang/Cute hub motor:
-Pro's: Freewheeling capability to reduce drag, probably a top pick for me.
-Con's: I have not seen these paired with a 48V 250-350w controller but may have not looked hard enough.

GNG Gen 2:
-Pro's: 48V capable, reasonably low power, low center of gravity
-Con's: I have no knowledge or experience with regard to these kits

??? You tell me ???
-Pro's: ??
-Con's: ??

 

[SlowCo]

Maybe a small friction drive like Kepler built is an option?:
https://endless-sphere.com/forums/viewtopic.php?f=6&t=74269

 

[daytonampco]

Maybe a small friction drive like Kepler built is an option?:
https://endless-sphere.com/forums/viewtopic.php?f=6&t=74269

I really do like the idea of a friction drive. It seems inefficient to use a large motor for a modest 250 watts of assist and allows for a more subtle conversion. However, I do not have any fabrication tools at my disposal to build a mounting bracket for a motor. That is a pretty big hang-up.

 

[daytonampco]

After more searching I like the feature set of the Smart Pie 5. The integrated controller and bluetooth would be quite nice. Tidiness and tuning are important attributes to me. However I fear it is out of the budget indefinitely. Guess I'll put it on hold for a few years!

 

[dogman dan]

Get a small rear geared motor. GNG just overkill for 350w.

Pair with cheap as hell controller off ebay.

Battery is the problem, your big battery is too big to keep the bike light. Perhaps try lipo, even though that means investing in a charger just for lipo. 10s 5 ah will be about 4 pounds of battery. 36v. Fit that in your pockets, almost. It can carry in a large under the seat bag. This setup would keep the added weight to the bike very low, perhaps 12 pounds more. You'll have to lace the wheel yourself, to keep a nice rim and light spokes.

48v 250w controller? WTF? 48v at 10 amps is 540 watts, at least at full charge voltage anyway. (54.6v)

You can use a cheap ass 48v 15 amps controller with the small motors. But that will be about 700- 800w. That can fry them, but only if your ass is fat and the hills steep. You can run that on your current battery in a backpack.

 

[2old]

Look at Chas58's builds; seem to be right up your alley.

 

[Joe T.]

GNG Gen 2:
-Pro's: 48V capable, reasonably low power, low center of gravity
-Con's: I have no knowledge or experience with regard to these kits

??? You tell me ???
-Pro's: ??
-Con's: ??

I know the Gen2 can take 52V Luna battery. I have had good results with this kit + 52V battery.

 

[motomech]

Look at Chas58's builds; seem to be right up your alley.

Yeah, and crossbreak and muian

Minis, especially Cutes in bike like that have been covered a million times here. Search using searchwords like Cute, Q100CST, etc.

In a nutshell, the forks are too spindly for a frt. mounted motor(which is the easiest way to go.
So, to retain the bike's cassette, go with Q100C (201 low-speed).
On 48 V, in those big wheels, top speed should be around 20 to 21 mph. On 52 V, 22 mph, no pedaling. Pedaling should add 1 or 2 mph. All told, fast enough for that bike.
Elifebike bike sells a nice 6-FET 14A 48V controller. They are available on Ebay;

http://www.ebay.com/itm/36V-48V-250W-14A-6FET-ebike-Electric-Bicycle-Brushless-Motor-Controller-LED-/222273910100?var=&hash=item795499df0a

Battery packs in back packs is a bad idea.

 

[Raged]

Get a BBS02/BBSHD and use your existing battery. If you keep the battery in your backpack, the bike will easily be under 15kg and still have the nimble feel. There is no drag and install is easy (depending on your chainline) with integrated PAS and throttle control out of the box.

Sure it might cost a bit more up front, but you end up with a better result. There is more power for those times you simply dont want to pedal.

 

[LewTwo]

In a nutshell, the forks are too spindly for a frt. mounted motor(which is the easiest way to go.

Frame looks similar to my Mitaya CT-7000. A bit more curve to the forks. Not had any problems with my front hub system.
Having said that the 'rather significant hills" would benefit from mid drive that can take advantage of the gearing.

 

[dogman dan]

Those forks can easily handle a low power front motor. But if you do that, the bike will ride like it has 6 or 7 pounds on the front wheel. It won't curb hop for shit.

Rear motor, or mid drive. I doubt a BBs01 will fit your bottom bracket. Some weird size stuff on those vintage ten speeds.

 

[LewTwo]

A bit of internet research for Sentinel Bicycle Manufacturing Company

"Whisper" the frame was either made in Chatsworth CA or depending on the model it could have been made by Shikamura in Kobe Japan. We were the first company to produce quality lugged frames in the US - and eventually couldn;t compete with Taiwan and the ocmpany was sold to a division of Bendix Corp who rather quickly ran it into the ground and closed it down.

I would lay long odds that it has a British bottom bracket except that Sentinel is known to have used a crankset called a Shimano Front Freewheel System (FFS) crank. https://en.wikipedia.org/wiki/Front_freewheel

I did find one reference to a thread spec of "1.37 x 24 T.P.I." so I am back to offering long odds on the British BB.
However if your bike has this unusual system you might not want to modify it unless you completely replace the entire drive from BB case to the rear spokes. Typical of the comments that I found was:

"If everything works, don't fix it. If something is really broken, you'll have a very, very hard time finding spare parts. It would be better to replace the crankset and rear wheel with a single-speed or internal-hub gear system to restore the bike to usefulness."