Bike Racer - Motorpacing eBike Build - Feedback? (Q100@48v)

Long time lurker, first time posting. I have been kicking around an idea since last year, and I think I will put it in motion this year, and I need some advice from the community. (I know little about ebike issues, but hit me if you have questions about bike racing tactics / stuff - I would be happy to help)

I am a US criterium racer, and getting upgraded to Cat 2 for 2016. There is a fair amount of guys that I race against that use "motorpacing" to help develop crank / leg speed at race pace. Short simple explanation: pedaling at 270 watts (human) at 28mph in a group with a 53 tooth crank and 14 tooth cassette, creates a specific demand on the legs to accelerate that gear in the ebb/flow of cornering / racing. (Without the draft, 28mph would take 350-ish watts-human, and is not a realistic solo training pace for very long)

The speed of race pace creates a very different leg / crank acceleration than pedaling at 270 watts (human) at 7mph up a hill with a 39 tooth crank and 23 tooth cassette. So, when people motorpace, they follow a moped or motorcycle at race-type speeds. (That also teaches you about drafting more efficiently) There are many different types of motorpacing workouts that can be done, but the basic premise is working your legs at race speeds. I do not have access to a moped and willing driver during my training hours, so this has never been an option. I saw some videos about ebike speeds last year, and it got me thinking - I can use a ebike hub to supplement my pedaling power, and to mimic the power of riding in the draft of a pack at race speeds.

So, I have been reading (a lot) but my build is not something I have seen replicated. (I am 5'10", 170lbs, with a 20lb training bike w/o hub or battery) So, here are the build principles:

1. The motor is only used to supplement pedal power, where I am pedaling fairly hard (no less than 230 watts-human)
2. The motor is only used when the speed is between 20mph and 32mph (top speed can be in the low or mid 30s)
3. The motor is only used on flat ground or slight rolling hills - no hill climbing (I live in Kansas!)
4. The battery should power the build for around 60 minutes or a little more, but will likely not be used at full-throttle
5. The "donor" bike will have 700c wheels, 700x28 tires, rim brakes, STEEL front fork, and Shimano 11-speed group (this means I must use a front ebike hub)
6. The build needs to be $500 or less, because I am a poor bike racer - I will sacrifice longevity and range (otherwise I won't be able to do it)

So, I think that I need the following:

1. A geared front hub
2. With winding/gearing that will go around 400rpm
2. At 48v (maybe 36v?)
3. With 350-500 cruising watts
4. Using a 10ah battery
5. Cruise control of some sort with a dead-man switch, or switches retrofitted to existing shifters
6. I have no idea about controllers, wiring, battery management, etc

So, I am leaning towards using:

Front Hub options:
Cute Q100 - either 36v 328rpm or 24v 201 rpm - with both motors volted at 48v to get desired RPM
Bafang BPM Code 8 or Code 9, maybe 10?

Battery ideas:
48v10ah bottle battery, like: http://www.greenbikekit.com/lithium-battery/li-ion/48v-10ah-li-ion-e-bike-frame-battery.html

Other parts:
No clue (controller, display, cruise control, wiring connectors, battery management, etc)

Any feedback help from the community would be great! Thanks!

This might give you some useful insight.

http://electricbikereport.com/electric-bike-cheating/

Maybe this thread gives an alternative idea (friction drive):
https://endless-sphere.com/forums/viewtopic.php?f=6&t=74269

SlowCo said:

Maybe this thread gives an alternative idea (friction drive):
https://endless-sphere.com/forums/viewtopic.php?f=6&t=74269

Click to expand...

I really like the idea of friction drive. For my bike, it could be mounted on the seatpost (27.2) or by the BB like Kepler did. The issue is that nobody sells it in "silly bike racer" kit form that I can plug in and bolt on. I have seen some pieces / parts being sold, but nothing that seems turn-key-ish. Maybe my Google-fu needs work?

If you care about the motor being quiet, get the new MXUS small geared hub with the helical gears, if you care about maximum possible efficiency, get the Q100H with the dual reduction that allows the motor to spin a little faster while still having the same output RPM for the wheel.

The flat land criteria means you can be happy with 36V, which allows a smaller and lighter battery pack, using the max range cells. I don't remember which control panel had the most "assist levels", but one of the Bafang units had 9 assist levels, when taking input from a pedal sensor (PAS). Check out Keplers light commuter build...

https://endless-sphere.com/forums/viewtopic.php?f=6&t=55225

Front hub a good idea, unless you get a rear motor that can actually take a cassette. You need your race gears.

350 ish, about the right rpm. and 48v

Don't go with a pedelec, or PAS, you need the instant and more control of a throttle.

You need a watt meter, preferably a Cycle analyst, and a controller that will direct plug in with it. Why? Because you need a bit more input, to get your pedaling wattage right. With experience, you will figure out your targets. Then you can use the CA to at least monitor the motor wattage on the fly, and adjust the throttle accordingly. Otherwise you can easily fall into the trap of pedaling a nice high cadence, but not enough effort for good training. With the CA, you can set limits on the motor as you desire, making this trap harder to fall into.

Since this is for racing, budget is limited only by how much you want to win. don't cheap out. Go to Grin Technology, and get a nice kit including the CA. The Ezee kit.

Unfortunately, this won't help with drafting, but by applying a bit too much wattage, you can still hit that same cadence and effort level as you have in the fast peloton, and run miles and miles of training at that pace, all by yourself. Use a second watt meter on your pedals, to know what your output is. Likely you have that already. Set your effort and speed to your liking, then adjust the throttle to maintain that sweet spot of effort at that cadence.

This is exactly how experienced e bike riders cruise, though possibly at lower speed. You have a cadence and level of effort you like. You hit that speed you desire to cruise, then adjust the throttle constantly to maintain the same speed, cadence, and level of effort uphill, into the wind, whatever. The result is a very nice workout at the level of effort your body likes. The body definitely hates those sprints, and when you are old and tired like I am, it realllly hates a sprint effort up a hill.

Only his budget of <$500.- will prove difficult to stay under...

Little Bill said:

I really like the idea of friction drive. For my bike, it could be mounted on the seatpost (27.2) or by the BB like Kepler did. The issue is that nobody sells it in "silly bike racer" kit form that I can plug in and bolt on. I have seen some pieces / parts being sold, but nothing that seems turn-key-ish. Maybe my Google-fu needs work?

Click to expand...

There is the Hidden Power kit http://hiddenpower.eu/en/products/standard.html .. I have no experience with it other than they will drop the price substantially once you start communicating with them .. almost ordered two, but then decided to try a mid-drive first ..

spinningmagnets said:

If you care about the motor being quiet, get the new MXUS small geared hub with the helical gears, if you care about maximum possible efficiency, get the Q100H with the dual reduction that allows the motor to spin a little faster while still having the same output RPM for the wheel.

The flat land criteria means you can be happy with 36V, which allows a smaller and lighter battery pack, using the max range cells. I don't remember which control panel had the most "assist levels", but one of the Bafang units had 9 assist levels, when taking input from a pedal sensor (PAS). Chack out Keplers light commuter build...

https://endless-sphere.com/forums/viewtopic.php?f=6&t=55225

Click to expand...

The noise doesnt matter to me at all. The unit will live on my training bike during motorpacing periods of time and will be obvious to all onlookers. I really like the friction drive idea, but I am not convinced that it would give me the juice I need at 30mph ish. The hidden power kit looks promising, but I dont see any specs on its rpm / wheel rpm, plus it blows my budget by double.

Erk, I should have read better, and even just assumed he wanted it all for $500.

Hmm, for 500 I'd motor pace you for quite awhile. Any ebikers in your area? Ten bucks an hour, 50 one hour workouts.

You can get something in a kit for a few hundred. For the speed you want it will have to be 48v. Not a 24v leed kit. At 30 mph it will take about one ah per mile. A cheap ass, straight from alibaba 48v 20 ah battery is about 400.

So you need to spend more like 600-700, to get enough battery to ride a full hour. And actually, the 20 ah will really only last about 40-50 min, hauling ass.

Buy as much battery as you can afford now, like 15 ah, then add another 15 ah later. 30 ah will get you that one hour workout.

This isn't your typical ebike rider, the OP is going to be using a couple of hundred watts max at high speeds to merely assist already vigorous pedaling so the standard rules about amp hours and miles aren't going to apply (unless he gets lazy and stops pedaling of course).

A relatively small pack should do what the OP wants for an hour ride at maybe 150 watts average, 200 to 250 watt hours at 48 V so about 5 AH or 12s 2p Samsung 25R cells.

Ok, so needing 1000w to cruise at 30 mph, he'll pedal up double the wattage than most do. A rider hiding in the peloton going 30 uses about 250w or so. If he jumps out front and breaks the wind, then he's not going to last one hour.

So figure he'll need about 700w at least still. So now lets calculate a cheap ass alibaba 48v 20 ah. First thing, you ain't getting a 20 ah. It will put out more like 17 or 18 ah.

So 18 ah x 50v is 900wh. So about an hour of run time out of 750wh, and a few min more from the last 150 wh. That's if it's flat, and there is no wind at all.

Now, if he wants to work harder than he would in the peloton, then he could go two hours on the 900wh.

I may be wrong about the wattages riding in the peloton, a criterion is a shorter race so they may run harder than I think even hiding in the wind shadow. The calculations get tricky, because watts to pedal 30 mph is less than the watts to electric motor 30 mph. But he won't get a long top speed workout from a 10 ah battery. He needs a 20 to get a long workout, of that I'm certain sure.

He'll need at least a cheap blue watt meter from ebay, so he can see what wattage the motor is assisting. Limiting watts won't do much good, because as the motor reaches the rpm for that (500W?) limit, if he keeps pushing a lot faster he'll just be pedaling away and the motor will only be pulling about 50w. Or it may even just start to freewheel. The motor shell doing 350 rpm, the core 250.

So he needs to adjust the throttle constantly, so the feel on the pedals is right, using the motor for most of the speed, then pushing for 2-3 mph more without pushing the pedals so hard it feels like he's leading out the peloton.

I was going by the numbers the OP quoted for wattage and then doubling the difference for what he thought he needed, 270 for in the peleton and 350 or so for the solo rider at 28 mph. He's going to be in a full tuck with all the roadie aero bells and whistles. So he was talking 70 watts additional and I was adding 150 watts. The Grin simulator says that 270 watts is good for 20.7 mph on a race bike in a tuck, I know how obsessive racers can be and I suspect the OP knows what he's talking about regarding watts for speed in full racing trim.

I am a US criterium racer, and getting upgraded to Cat 2 for 2016. There is a fair amount of guys that I race against that use "motorpacing" to help develop crank / leg speed at race pace. Short simple explanation: pedaling at 270 watts (human) at 28mph in a group with a 53 tooth crank and 14 tooth cassette, creates a specific demand on the legs to accelerate that gear in the ebb/flow of cornering / racing. (Without the draft, 28mph would take 350-ish watts-human, and is not a realistic solo training pace for very long)

Click to expand...

Yeah, I forgot to account for the tuck. But when I was racing on the kart track, I needed 1000w to go fast. I had the seat low, bars upside down, you know the boardtracker setup. A tuck lower than a bike racers. But the straights were so short on that track that I don't think I ever wound out to cruise wattage. I was always in an acceleration or deceleration mode. So I was always pulling 1000w, or none.

That experience must have skewed my idea of what it will take him to cruise, in a tuck, I'm assuming full speed of 27-30 mph or so. If he can put out 250w pedaling, then he's likely to be seeing 500-600w on a wattmeter, to get 27 mph cruise. So a 48v 15 ah battery could get him a full hour ride. But he'll still like a bit longer workout, with 48v 20 ah.

I appreciate all of the feedback. I am thinking that Jonathan and Dan are both tracking on the idea nicely. I have found a Q100 front motor, that is rated at 328rpm @ 36v. If I use 48v, my estimates put that at 400rpm. (no load) With a 700c wheel, the no load mph appears to be around 32mph. The idea of motor efficiency makes the loaded speed of 28mph (with me pedaling hard, on a road bike, in an aero position / drops) seem about right. Does that jive?

I am unsure of the controller and cruise control. What controller will do 48v with max current of 15-20A? (will likely be using less than max 100% of time) I have looked at the KU series of controllers, and the KU93 / KU63 (new style) will not handle the rpm. (see threads about it shutting off) I also need some form of cruise control, and I have no idea how that gets integrated with the controller or as an add-on.

Cruise is going to be tricky because you want to simulate being in a pack and the effect of drafting is going to vary with speed, normal ebike cruise is almost going to be the inverse of what I suspect you need, less help at lower speed and more help at higher where drag would be greater out of the aero advantage of the pack. Some kind of torque based throttle with torque increasing with speed sounds about right. Trouble is torque based controllers tend to be expensive, about half of your desired total expenditure or more.

The Q100 sounds great but you might want to consider going to 14 serial or 52V rather than 48 just to make sure you have enough torque left at high speed.

You are certainly right to doubt my understanding of ebike cruise! So, will it hold amps steady, or does that change with RPM or load? I could also put a cheap motorcycle cruise clamp on the throttle and use the ebike brake levers to kill the throttle.

I am looking at these two controllers:
http://www.elifebike.com/peng/iview.asp?KeyID=dtpic-2012-37-QE34.0KCJE
http://www.elifebike.com/peng/iview.asp?KeyID=dtpic-2012-8W-QNK2.073KQ
(I dont think I want EABS? - I am guessing that doesnt allow the motor to freewheel when the throttle is off?)

If that system's EABS is liek the one on my controllers, it just means that when you engage the brake, it doens't just cut off the motor, it also actively brakes the wheel. Not just by "regenerative braking", which typically gets less and less force as you slow down, but by actively powering against the direction of motion, all the way down to very slow speeds.

Using that alone, on the two rear wheels of SB Cruiser, a pretty heavy trike, I can stop from 20MPH in a couple of trike lengths or so. (I can stop in about one length or so if I also use the front rim brakes at the same time).


But it doesnt' keep me from coasting, just letting off the throttle, without hitting the brakes.

spinningmagnets said:

If you care about the motor being quiet, get the new MXUS small geared hub with the helical gears, if you care about maximum possible efficiency, get the Q100H with the dual reduction that allows the motor to spin a little faster while still having the same output RPM for the wheel.

The flat land criteria means you can be happy with 36V, which allows a smaller and lighter battery pack, using the max range cells. I don't remember which control panel had the most "assist levels", but one of the Bafang units had 9 assist levels, when taking input from a pedal sensor (PAS). Check out Keplers light commuter build...

https://endless-sphere.com/forums/viewtopic.php?f=6&t=55225

Click to expand...

q100h are already super quiet with sine wave

Freewheeling is already built into the motor, controller has nothing to do with it, EABS or not. Since the motor freewheels the EABS won't do anything but suddenly stop the motor when engaged, you won't even notice it most likely, at most you'll feel a slight jolt as the motor rapidly brakes.

As for the throttle, put a variable resistor with a knob you can adjust with a finger or thumb while riding and connect it to your throttle wires. If you do this make sure you have the brake disconnect switches wired in, you can buy ones that go on the brake cable so you can keep your existing levers which are almost certainly superior to the ebike ones.

Like you were saying, likely you will be running at 100% throttle, so you don't really need cruise so much as a throttle you can just hold easily at WOT.

I'm not sure how to work this with drop bars, and a thumb throttle that works best with drop bars. With flat bars and half twist throttle it's easy. jam the grip against the throttle, and make it sticky.

But one option would be a very simple on off throttle, essentially a doorbell button like switch on the grips. Pedal to 15 mph, hit the switch, and off you go. It would need to be something easy to just grip the bars, and engage the switch.

Which controller you want I don't know, but you need something that won't have a speed limiter. Just a bare bones 20 amps 48v controller. Tons of them on ebay.

Re the freewheeling motor, if you are strong, you'll find yourself outrunning the little geared motor. (if the motor rpm is not high enough) Then the motor spins happily away at no load, and you are doing it all. This happens to everybody going downhill, but you might be doing it on the flat. A larger motor will be able to go faster and have less tendency to do this. It might be best to use a direct drive motor, but that would be heavier of course, affect the bike handling more.

I should have mentioned that about outrunning the motor sooner, but I just didn't think of it till somebody mentioned freewheeling.

Well, I am still arranging my ideas and thought I would bump the post. I am leaning towards a over-volted q100 that will do 400ish rpm at 48v, and likely run it at 500w or less. My bet is that I wont be running it at wide open throttle, since I will be doing specific speed workouts, pedaling my ass off. I am leaning towards a 10ah battery due to costs.

I would like the friction idea, but the cost seems high.

Little Bill said:

I appreciate all of the feedback. I am thinking that Jonathan and Dan are both tracking on the idea nicely. I have found a Q100 front motor, that is rated at 328rpm @ 36v. If I use 48v, my estimates put that at 400rpm. (no load) With a 700c wheel, the no load mph appears to be around 32mph. The idea of motor efficiency makes the loaded speed of 28mph (with me pedaling hard, on a road bike, in an aero position / drops) seem about right. Does that jive?

I am unsure of the controller and cruise control. What controller will do 48v with max current of 15-20A? (will likely be using less than max 100% of time) I have looked at the KU series of controllers, and the KU93 / KU63 (new style) will not handle the rpm. (see threads about it shutting off) I also need some form of cruise control, and I have no idea how that gets integrated with the controller or as an add-on.

Click to expand...

I have found a Q100 front motor, that is rated at 328rpm @ 36v. If I use 48v, my estimates put that at 400rpm. (no load) With a 700c wheel, the no load mph appears to be around 32mph. The idea of motor efficiency makes the loaded speed of 28mph (with me pedaling hard, on a road bike, in an aero position / drops) seem about right. Does that jive?

Click to expand...

Those numbers seem about right.
But I want to correct an assumpsion you made early in the thread. That is, the possibility of using the drive system "part time".
Even a sm. free-wheeling motor like the Cute and a light weight battery will be felt when pedaling with the system off. You will want to keep some power(abeit, very little @ times)on all the time.
The best way to do this is to use a sine wave controller/display that provides 5 range, "torque imitation" PAS. The 5 ranges are limited by Current, rather than speed limited(the more common method). This action, combined with the 5 ranges, provides the maximum versatility. The PAS limit can be adhusted on the fly.
BMS Battery does not offer a sine wave controller that will live on 48V, w/ the exception of the new intergrated/dolfin style battery combo, so that is what you want to use;
This appears to be the least expensive one;

https://bmsbattery.com/ebike-battery/784-48v116ah-case-08-bottle-panasonic-battery-pack-battery.html

It should have a 20 mile range for the planed useage. More range, more money.

I supplied a friend w/ that battery(but not w/ the controller)and it has held up ok, but there is little doubt the more expensive packs with the Panasonic cells are a worthwhile upgrade if the budget can be streached. The chargers supplied with these batteries are junk and will likely need replacement at some point. Options here to is buy one of the dedicated chargers from BMS Battery with this order or to buy when it fails. Luna Cycle, here is the States has some decent chargers @ a reasonable price.