Advice for a first build

Deleted member 4366 · Feb 10, 2018

At only 60kg, a Q100 is a good choice. If you want a modal speed of 20 mph (32 km/h), you need around 260 rpm. The 24v 201 rpm one at 36v becomes too fast, especially with 700c wheels. For a front motor you want the 260rpm Q100H or the 201 rpm one and run it at 48v. You will probanly be OK with a 15 amp controller as you don't weigh much, but if you want an easier time at the expense of using more battery, you can go to 17 amps.

The best controller, in my experience, is the KT with the LCD3. That's the S06S from BMSBattery also obtainable from PSWPower and Aliexpress as sine wave controllers. Buy the LCD with the controller asva pair to ensure compatibility because there are different versions.

The battery you propose is OK, but it's quite expensive to make your first one because you have to buy special equipment. Unless you plan to get heavily involved and build more batteries, a ready-made one would be better. You can get a nice frame-mounted one for best weight distribution. Bear in mind that using constant 20 mph speed will consume about 20 to 25wh/mile, so 10Ah will take you about 20 miles max.

A rear motor is better, IMHO. It's quieter, safer, gives better handling and better traction. For a rear motor, you need the Q100C, which would mean the 201 rpm one at 48v to get the 260 rpm speed.

One torque arm should be enough because the Q100 doesn't give as much torque as some motors. It's really important to make sure that a front motor is installed properly, so if you go ahead with one, ask again when it arrives to avoid pitfalls.

Generally motors pull well up to about 75% of their no-load speed, then the power is a straight ramp down to zero at maximum rpm. How fast you go on the road depends on how hard you pedal. Don't forget that your actual battery voltage is arounf 40v when full, so a bigger battery will hold a higher voltage for longer and those extra 4 volts give a 10% increase in power anfd speed. Taking the 260 rpm Q100h, you get an otr speed of .75 x 260/201 x 1.1 x 28/26 x 25 km/h, which is around 29km/h. Assistance will then carry on, though decreasing to 38km/h. That's with a full battery. Multiply by 0.75 for an empty battery. If you need more speed than that, you need to go up a motor size to the Q128, in which case the rear 36v 201 rpm (actually 260 rpm) Q128c at 48v or the 48v 328 rpm one would be perfect.

anotherkiwi · Feb 10, 2018

If you are a strong cyclist to begin with set the cut off to 25 km/h and use the motor for starting off and climbing hills, that will get you maximum range.

If you want assist to 33-35 km/h a 36v Q100C rear motor with a 48v battery would be my choice too. Go for the 20A sine wave controller from pswpower because at assistance level 4 you will have a nice healthy 480 W and keep level 5 in reserve for when you have to go wild

The cells you chose don't have a high enough discharge, only 7 Amps. Look for something with 15 Amp discharge or more if you want to make a small and light battery.

I am running my mid-drive GSM set to cut off at 37 km/h at the moment and it is OK but I may turn it down to 33 km/h for more range. 45 km/h is lots of fun except for traffic, no one expects an old guy pedalling to be moving at speeds like that and they pull out in front of you at every single stop sign or roundabout...

Deleted member 4366 · Feb 11, 2018

Those shark batteries are not so easy to fit because the fixing holes are too high compared with those on your down-tube, which means you have to drill your frame and add your own rivnuts or do some bodge. The Dolphin ones are very straight-forward.

Thev Q100H is 2.2kg, the same as the Q100. Only the internal gearing and windings are different. Everything is interchangeable.

anotherkiwi · Feb 12, 2018

AviatorTrainman said:
Anotherkiwi said that 7 amp discharge is not enough. Is that only when used with a 20 amp controller? In a 4p configuration, that gives 28 amp max discharge, which seems like plenty for a 15 amp controller, like I have decided I will use.

15A / 4 = 3.75A or more than 50% of a 7A cells discharge, aiming for 33% or less is much easier on the cells and you won't sag as much on hills. Bigger power is always better, smaller weight is too so you have to find a compromise.

[QUOTE="AviatorTrainman, post: 423141, member: 22138"
- I have an 8-speed cassette which I am very happy with, and a rear q100 would force me to change that, which is also expensive, since I would need new index shifters, and possibly a new freewheel/cassette.
[/QUOTE]

A Q100CST allows you to keep your cassette.

I get your point with riding on snow, I have done that in the distant past. Personally I find a front motor to be very un-bicycle like to ride, some people get on fine with a front motor, it boils down to personal taste I guess.

Deleted member 4366 · Feb 12, 2018

Front wheel drive is not much good for slippery conditions. There's not enough weight on the wheel to get traction so it just spins. That effect is made much worse when you go uphill, which is when you need the help from the motor.

Woosh · Feb 14, 2018

AviatorTrainman said:
Okay, thanks for letting me know. I'll consider a rear wheel drive. How can I use a rear wheel drive and keep the weight balanced?

fit a downtube battery.
The weight of the battery is roughly same compared to the weight of the rear motor.

harrys · Feb 18, 2018

I like that ebay kit. I believe he's the only guy in the US with a low cost geared motor. I bought one from him three years ago and have 1300 miles on it. No troubles with the motor. I had the LED version with 3 level PAS, which is a bit crude but level 1 is perfect for me as it runs up to about 13 mph and shuts down. Allows me to ride at 12-14 mph. Throttle response is mild on 36V, but probably typical of a 500W motor with a 20A controller. About 20 mph top speed on throttle. Run on 48V, it will do 24 mph and feels pretty comparable to other 48V bikes I've ridden.

That was the old kit. I just bought the current one that you're looking. LCD version. Rear wheel. $209 USD. Free shipping. Last November, I paid $144 USD just for a Q128H shipped. No electronics. No wheel. This is certainly less money. He was out of stock since October on ebay, which is why ordered a Q128. When I saw he had stock last month, I ordered one. Came in two days as he ships out of Chicago.

The new kit with LCD has a 22A controller. Appears to be compatible with both 36V or 48V. 5 level PAS. I won't have it on a bike til April, but have run it on my bench and look forward to trying it out. I liked the LCD version, for more flexibility in battery voltage. Again, I haven't run it in real world conditions yet, but the previous motor was alright for me.

Deleted member 4366 · Feb 18, 2018

AviatorTrainman said:
I've got the full kit planned out, with everything except the battery and spokes coming from BMSBattery. It'll be 248 USD. However, I've been looking around, and I recently found this: https://www.ebikeling.com/shop/electric-bicycle-36v-500w-geared-rear-700c-kit-opt1, which would be 185 USD. Does anybody have experience with these ebikeling kits? It seems like it'd be a much better deal if it's up to the task.

It's a freewheel motor, so you'll be limited to 7-speed gears unless you want to do some other modifications. If you presently have more than 7-speeds at the rear, a cassette motor will be much better.

anotherkiwi · Feb 18, 2018

d8veh said:
It's a freewheel motor, so you'll be limited to 7-speed gears unless you want to do some other modifications. If you presently have more than 7-speeds at the rear, a cassette motor will be much better.

Looking at the DNP 7 speed freewheel I have here it looks like one could machine about 1.8 mm off the rear and front lock rings. I was wondering if an 8 speed 13-34 could be brought down to 37 mm stack height thus fitting one of the tiny Xiongda rear freewheel motors...

Deleted member 4366 · Feb 18, 2018

You can fit a DNP 8-spd, but it makes the motor wide on the one side, which off-sets the rim. You can compensate by dishing the wheel, but that means loose spokes on the non-drive side. Alternatively, you can compensate by adding a space to the opposite side, but then you need to stretch your frame even further, which then means that you have to sort out caliper alignment if you have a disc brake. There's loads of things you can do if you have the motivation.

7-spd would be OK if you changed over to a Shimano Tourney caliper and shifter - not as good as a Shimano XT cassette system, but they still work.

My point is really that if you have nice gears on your bike, it's probably better to pay a bit more for a cassette motor to keep them. It's going to cost at least £20 on top of the kit for a DNP freewheel, and that's about the difference between a cassette motor and a freewheel one, so it would make more sense to go with the cassette motor and keep your nice gears rather than downgrading to crappy 7-speed gears at the same cost, but with loads of hassle to install it all too.

People often only look at the cost of the kit without thinking about the overall cost to get there bike running how they want it. Cheap kits are great for cheap bikes.

anotherkiwi · Feb 18, 2018

Keeping the dishing to a minimum was my goal in getting rid of the 1.x mm or so and getting the 8 speed down from 38.9 mm to as close to 37 mm as possible.

There is already a 6 mm dish with the xiongda. As there is now a sensored option for this motor there ara a couple of wheels I'd like to build with it in. One is a 7 speed bike so no issue, the other would be better with the 8 speed.

anotherkiwi · Feb 19, 2018

I found this thread which I now remember reading a couple of years ago when I was building the freewheel Mxus bike:

https://endless-sphere.com/forums/viewtopic.php?f=3&t=62844

So it is possible to disassemble DNP freewheels and swap cogs around. Of course gear changing may be affected - some shifts might not be a smooth as before.

Deleted member 4366 · Feb 21, 2018

Read what I wrote in this thread, which highlights the advantages of a hub-motor system.

http://www.pedelecs.co.uk/forum/threads/which-one-chaps-carrera-crossfuse-or-oxygen-s-cross.30514/

To keep it balanced, crank-drives have the advantage that they can give high torque and high speed, but not both at the same time, though that advantage disappears if your hub-motor has enough speed and torque for what you want.

Woosh · Feb 21, 2018

d8veh said:
To keep it balanced, crank-drives have the advantage that they can give high torque and high speed, but not both at the same time, though that advantage disappears if your hub-motor has enough speed and torque for what you want.

that's the best summary I've read for a long time.

Advice for a first build

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