Looking for some advice on a new build please

[Eujangles]

Hello ES,

Thanks in advance for any advice you guys can give!

I recently sold an ebike from the stable, which has allowed me to take on a new build

Here's the plan so far:
-Light weight single-speed bike
-Q100H 201 RPM, rear wheel
-KU93 Controller
-48v 10ah

Here's my problems:
-I'd like to use an aluminum frame to drop some weight. I know that it is not recommended to do so, but I also know that there are people here who have done it successfully. Yes, I will use torque arms. What do you guys think? Is it such a big deal on rear dropouts, that are already meant to take some torque? Also keep in mind that I'm not dumping tons of volts into it, so hopefully the strain on the dropouts won't be so bad? I'm all ears if you guys think this is a bad idea...there are lots of great steel-frame single speeds out there.

-I'm a bit worried about the spacing on the 120mm dropouts with an aluminum frame, seeing as I can't exactly bend the aluminum if I need more space. Another ES member here (chas58) managed to fit the Q100 in some 120mm dropouts, and actually fell short, and had to use a washer to fill in the space: http://endless-sphere.com/forums/viewtopic.php?f=3&t=49691&p=738009&hilit=120mm+q100#p738009. So with that in mind, do you guys think it's a big risk for me to buy an aluminum bike, or does it look ok to you, since the q100 doesn't actually fill up the 120mm?

-I know some people here have had problems using the KU93 on the Q100, however, I think those people were likely trying to use it on the 328 rpm model. On the gf's bike, I have been running the original Q100 201 rpm, on the KU93 for about 3 years with no problems, which is why I am ok with doing it on my new build. However, do you guys think I should be worried that the 30% extra torque claimed by the Q100H will be too much power at 22A for those little gears? I'm open to just using another original Q100, but I like the black casing and am tempted by the higher torque of the Q100H, which is why I am hoping I can use it instead.

-I'm 100% open to suggestions for different controllers, or going up to the 260 RPM version of the Q100H, but I'm pretty certain I can't run that high RPM safely with the KU93 controller. I've looked into what some other people have done to accommodate 48v on the Q100H 260rpm, and it seems most of them have modified the living hell out of a KU63. I do not have the expertise to do this, so would just be looking for a stock controller that can handle the Q100H and 48v. I'm not too hung-up on pumping out amps (14-18 would probably be more than enough for me at 260 RPM), I just want a zippy bike with a top end of somewhere around 40km/h (I won't be upset if it's a little lower than this).

-Do you guys think I am better off going with the 260RPM model and getting a CA to limit the amps for the KU93 with?


Thanks again everyone!


P.S. If anyone out there sells modified KU63's that can handle 48v, please let me know! I'd love to have one of those at a lower amperage (14a-18a) so I could move up to the 260RPM model

 

[RVD]

maybe a dumb point but ebike and light weight don't really go together. how much weight would you save by going with aluminum and is it really worth it by the time you add in your motor + batteries?

but in any case, a nice set of torque arms would be fine.

 

[Eujangles]

Hi RVD,

Fair point, but I do think it will make a difference, only because I do lots of pedaling, and so every pound counts when I'm not laying on the throttle to get around. So the whole build is kind of based around losing every pound I can, which is why I am going with the Q100 instead of a motor better suited for 48v.

Something like my gf's bike is more or less what I want for myself: the thing is so light for an ebike (maybe it weighs at about 35lbs), and it's just a treat to pedal and so much more maneuverable than my old tank. So my line of thinking was "how sweet would it be to have that, but even lighter?"

That said, you're certainly not wrong about it...it won't make a world of difference at the end of the day, I'd just prefer for it to be as light as possible.

Thanks for letting me know that the torque arms should be sufficient, appreciate it!

Cheers,
Eugene

 

[wesnewell]

The downloadable drawing of the Q100H shows the axle channel cut for 134.2mm. If that's true, then it won't fit 120mm dropouts without shaving/filing the axle channels at least 10-14mm.

 

[Eujangles]

Hi wesnewell,

Thanks for the reply. That 134.2mm spacing includes an adapter that is meant to get the Q100 up to the more standard 135mm, as shown here by chas58: http://endless-sphere.com/forums/viewtopic.php?f=3&t=48848

He was able to remove the adapter and use a bearing to get the right fit with a single speed freewheel. I'm hoping to do the same, but my concern is that if it somehow winds up being a bit wider than 120mm, I can't really bend the frame safely. I'm thinking it probably won't be a problem, as when chas58 did it, he actually had room left to spare, hence needing the bearing. Then again, maybe I am just being silly wanting to use aluminum

Thanks again,

Eugene

 

[wesnewell]

If it's actually 119mm then it shouldn't be a problem. I think you'd be ok spreading the frame up to ~5mm. Maybe use a 3 spd freewheel.

 

[Eujangles]

Awesome, thanks wesnewell, much appreciated!

 

[motomech]

I'm no expert in the bicycle drive systems, but it seems to me that the OP has left something out entirely and chas58 only touched on. That is, the lack numerical range of fixie sprockets. Chas stated he was using a 16/42 ratio, which was ok for 15 mph. Yet the OP is talking about a top speed in the 40 Kph range. How does one pedal along with a 16T fixed gear? That would take a seriously large chain ring, would it not?
It seems to me, a much simplier way to approach this is to start with a CST motor.
Remove the two nuts outside the bearing on inside the spline housing and trim back said housing flush with brg. That gives a well-centered, drop-out width of 122 m/m. and add one flat washer and then we have 123 m/m.
Then use a Harris Cyclery spacer kit, which, if I read their info. correctly, allows the fitment of either a 11T or 13T fixed sprocket.
Maybe a little heavier than a single fixie, but it would retain the nice free hub mechinisum

 

[Eujangles]

Thanks motomech, that's a good point, and a problem I already have on the gf's bike. The Q100 I have in there just has a 6 speed freewheel and sits on the 3rd cog (not sure how many teeth, but it looks to be about the same size as the one chas58 was using), and yeah, it sucks on a flat when the motor outpaces the max pedaling speed. Nice on hills though, and my gf doesn't mind as she never goes fast anyways.

Can't I just go up to a bigger chainring, like 48T or 52T? I don't really know a lot about bike drive systems, so maybe there is some reason I can't?

Also, I won't be heartbroken if I don't hit 40km/h (or at least can't pedal with it). I'll probably never be going that fast on flats living in a city anyhow, I just like the extra power in the motor in case I need to take a lane and keep pace with traffic on side-streets. If I can get up to even 30km/h pedaling, with some extra juice to boost ahead with the motor (say at least 35km/h), I'll be happy.

 

[fellow]

Q100H 201rpm 36V with this 48V controller
http://m.aliexpress.com/item/1749495210.html?productSubject=Regeneration-Electric-Bicycle-Brush-less-Controller-48V-6-MOSFET&productSubject=Regeneration-Electric-Bicycle-Brush-less-Controller-48V-6-MOSFET&productId=1749495210&productId=1749495210&tracelog=wwwdetail2mobilesitedetail
will get you up to steady 30km/h-32km/h at 54.6V (13s lipo) without pedalling.

If you choose 7-speed freewheel, you can get 13t-28t. I use only 2 speeds, 28t at extreme hills, and 13t for everything else. 6 speed freewheels are 14t at most.