eBike mod ideas

KenC

100 µW
Joined
Mar 20, 2012
Messages
9
Hi,
I am a old fat geezer whom had just had a taste of motor-assisted bicycle and I want more.
A month + ago, I started an experiment on low power ebike by converting my Dahon Boardwalk into a front geared hub motor. The battery pack is 48V 12AH, ON/Off Throttle only with brake sensors. The battery and controller are stuffed in a waterproof handlebar bag, Something really straight and simple.
I use it to run errand around town and join spirited rides in the evening hitting 30~40km/h for 80km rides with young and strong Lycra laden cyclist along the highway, you can imagine how wide a grin is on my face :D
Now that I am out riding more, I am surprise that I actually got some decent workout and my breath and legs got stronger. I call the experiment a complete success. #except for heating problem with the controller and hub motor.
For my second build, I need something to cool the controller and the hub.

After weeks of endless-sphere I had come to this point.
My objective is to ride gentle 5% gradient for 30km continuously. 120kg rider, 15kg bike, 20" (406) wheels, front geared hub motor. speed doesn't matter but I do understand that the motor will be happy if I keep it 20+km/h.

Controller
The controller is the easy bit, water/weather proof (by applying nail polish on the PCB and silicone the controller case), mount it on the bike frame and let natural air do all the work. if it doesn't, I will add as many heat-sink on the casing to make it works.
Actually, I reckon waterproofing the wires are more challenging... Yes, a Sine wave FOC controller if I can find one for hub motor. 20A with 5 levels if I can find any.

Geared Hub Motor
I will stick to geared front hub. for convenient sake. If it works here, it will work elsewhere.
The hub will receive oil bath mod with ATF. I learnt that the coil varnish is rated to 150C, I also know wire rubber insulation for most high temperature electrical wires (for motor phase and halls) are 120C. so this leads to my design max. temp cut-off of 110C. Theoretically, any water ingestion should boil out at that temp given enough time, which is a bonus. Not forgetting to coat all wires and plug all holes with high temp RTV liquid gasket paste which usually has 250C temp rating. Use rubber seal bearing for the external hub bearing.
From many oil cooled hub projects I read on the forum, it seems that an air breather valve is missing from most projects. Breather valve is an old tested way to equalize internal pressure due to heat and expansion of the air and oil in the hub which could cause bleeding bearings and dripping wires, they are used everywhere, eg, transmission gearbox, engine block, differential gearbox, motor gearbox, gas tank, diesel tank, etc. The breather valve I found looks like a M6 bolt with holes drilled into it and built-in 0.07bar relief valve and oil filter, it should keep the oil in and water oil of the hub. not forgetting it can breath 300ml/min.

Thermometer
While I am at it, I will install dual BBQ probe to monitor the coil and controller temperature.

Heat sink
Solder/blaze on vertical air fin on the hub (unlike the Hubsink which is radial fin), at least double up hub surface area if possible.

While I am at it,
find a good looking battery case....

These are about everything that I could think off for the mod, what else other sensible stuff can I incorporate into this build?. I am open to all suggestions while I am at it....

You comments and suggestions are most appreciated.
 
Hehe. That is only your 2nd. Soon enough, you will want more power and speed, a bigger frame that has no door hinge in the middle, good disc brakes and bigger wheels...
 
MadRhino said:
Hehe. That is only your 2nd. Soon enough, you will want more power and speed, a bigger frame that has no door hinge in the middle, good disc brakes and bigger wheels...
A third no door hinge frame had been located... LOL :lol:
Before that, lets get rid of the heat first. :twisted:
 
Solving the heat best is to go bigger. Bigger controller, bigger wires, bigger connectors, bigger motor. Small things don’t shed heat much. They can be helped, but only so much as to survive a little longer.
 
MadRhino said:
Solving the heat best is to go bigger. Bigger controller, bigger wires, bigger connectors, bigger motor. Small things don’t shed heat much. They can be helped, but only so much as to survive a little longer.
Or smaller rider....
That being said, I consider pushing tiny geared hub motor an engineering challenge, if we can achieve to pump 50Amp into an 250W hub motor, we can do a lot more for big DD motors.
 
If you don’t mind killing them...

I have filled a whole garbage can with fried motors, testing the limits. We are many here to have spent a lot of time and money to find out how bad is too bad. Most of them motors are well documented now. Just copy what had been done best with yours, yet reliable.
 
MadRhino said:
If you don’t mind killing them...

I have filled a whole garbage can with fried motors, testing the limits. We are many here to have spent a lot of time and money to find out how bad is too bad. Most of them motors are well documented now. Just copy what had been done best with yours, yet reliable.

Would love to follow your foot steps. If I can find those documents…
I am not here to reinventing the wheel. Just need some pointers for more essential work while I am at it.
 
There's a thread "oil cooling your hub, not snake oil", IIRC, with a lot of good info.

Justin_LE has a thread for Definitive Testing of heating and cooling of hubmotors that has more.

There are some threads about Ferrofluid / Statorade that have some info.

Hubsinks are an option for the larger diameter motors; you can find the sale thread and see if they're avaialble for smaller diameter motors. (or you can DIY your own).

http://ebikes.ca/simulator has a number of hubmotors you can setup in various systems and conditions, and see where the overheat points are.

Controllers need to be out in the open air to shed heat, unless you setup some other cooling method, so if you have yours in a bag, then overheating can be expected under a number of conditions.

Waterproofing them is difficult unless they are potted, but conformal coating can help, and is often sufficient depending on conditions it's used in. A recent discussion in one of the Mobipus threads talks about differences between those methods, as do other threads, like the Phaserunner thread by Justin_LE in the Items For Sale - New section.

Mounting them so the circuit board is at the top is often enough; it means any water that does get in doesn't pool on the board. (mine are mounted that way under my SB Cruiser trike; it doesn't get wet often, but sometimes when it does it's a complete dunking of everything underneath, because we typically have either drizzles for hours to days, or flash floods, and not a lot between those, and then complete dryness for most of the year. Havent' had one fail from water intrusion there so far, even though they are not sealed or waterproofed (except for the SFOC5 under test)).


Regarding how much current you pump thru a motor: at some point you reach saturation of the cores, and further current makes more heat and less work. The simulator linked above can help show some of that; the Definitive testing thread explains some of it, as do other threads I dont' recall titles of right now.

Small geared hubs heatsoak quickly, as there isnt' enough thermal mass. Hall sensors are easily damaged by this, but sometimes they dont' fail, they just stop working until it cools down (did this to my Dayglo Avenger's Fusin 350w hub pushing almost 4x that power thru it frequently, damaged my fork's dropouts (and the hub wiring) from spinout, and eventually broke the clutch but hadn't yet fried the motor or halls at that point. started to test ATF filling, but life and other stuff intervened, and never got back to do that).
 
You'll have a very hard time... "soldering/brazing"... fins to an aluminum hub motor. Thermal epoxy and/or a clamping system is a much better method.
 
So far as good looking battery bags for a cruiser, Amazon has several leather and hard case bag options for motorcycles, in the $50 range per pair.
 
You don't need to do anything exotic like cool your motor. Just buy something big enough. Even something like a 1.5kw nominal motor could probably take your use all day. 1KW if it's cold.

You can also look into a mid drive if you want more of a install and maintenance challenge. The advantage of a mid drive for you is you can use a small and light motor to do what you want by running it thru the bike gears.

It's not clear to me if your setup uses torque sensing or not, but if not, you'll want to upgrade to that ASAP if you like to pedal.
 
KenC,

I have a friend who will only use steel front forks on a front-wheel drive system. He reports breaking some aluminum forks in-flight, with predictable results, especially when using the stronger motors. Just a thought . . .
 
There shouldn't be a problem as long as proper mounting procedures are followed, and sufficient and properly mounted and designed torque arms are used.

Often you can get away with less precise stuff (I used wrenches and hose clamps successfully for a couple kW on CrazyBike2's front wheel in an alloy fork; the rear wheel was in clamping steel dropouts), but it's less guaranteed to prevent issues.

There are a number of threads dealing with the torque arm vs dropouts issue.

If they're breaking at a point other than the dropouts, then they might've been able to break just from braking forces (this has happened on a number of fork designs over the years, without power assist involvment)
 
classicalgas said:
You'll have a very hard time... "soldering/brazing"... fins to an aluminum hub motor. Thermal epoxy and/or a clamping system is a much better method.
The thermal epoxy I'm able to get my hands on don't have good thermal conductivity. Also not for outdoor use...

Sent from my Moto G (5S) Plus using Tapatalk

 
amberwolf said:
There are a number of threads dealing with the torque arm vs dropouts issue.
If they're breaking at a point other than the dropouts, then they might've been able to break just from braking forces (this has happened on a number of fork designs over the years, without power assist involvment)
Amberwolf,

The issue was not with dropouts and torque arms. My friend reports that the non-steel forks were breaking.

Put any metal tube in a vice, press down hard, and relax. Repeat endlessly. Depending on the load applied, after a certain number of load cycles, the tube will break. Do the same test again, but this time press down, relax, pull up, and relax. The tube will break *much* sooner, when you might have expected the number of load cycles to be about half of the first number. The number of load cycles (up and down) will be far less, instead. Normal braking loads are exactly what the bicycle front forks are designed to handle. Adding the pull of a motor is often not an anticipated load for most forks, and it's done in the "wrong" direction.

The studies of these types of tests are the origins of the term "engineers." It was the railroad engineers who developed this branch of mechanical science, because they were breaking the driving rods on the first locomotives. You should know, those steam locomotives had double-acting pistons, so the driving rods both pushed and pulled, to move the train. It was in the best interest of the engineers to use the minimum of weight in the driving rods, without breakage of those rods.

Bottom line here: to me, a steel bicycle fork seems like a prudent choice for use with a strong front-wheel drive motor. Feel free to use any fork that you may choose, of course.
 
Eh, frying hub motors is fun. But when you get tired of it, just get a big rear direct drive motor, that really makes your bike into a moped. It does cost some cash though, mostly for the battery that can handle it.


You can break alu forks with front motors, but dual torque arms and using c washers makes it ok for low powered motors. It Does wear out forks crazy fast though, running a frontie on a shock fork. Some will just jam up and never work right too. That's why I said get a big powerful rear, when you want to be more than a bike.

Get your controller outta the damn bag. With a fender, mounting it just under your ass behind the seat is a very dry spot. Fender keeps the splash off, and your ass makes a rain shadow when moving. Bag it seat and all when you park in the rain.
 
"The thermal epoxy I'm able to get my hands on don't have good thermal conductivity. Also not for outdoor use..." Then clamp with thermal grease. Heating the casing of a hub motor enough to solder(ever tried to solder aluminum? It's not easy) much less weld, fins to it will distort it, damage magnets, etc. You'll need to pull the stator and all wiring, too. That's why all the proven schemes for adding fins to hub motors use clamps/ cold bonding.
 
My objective is to ride gentle 5% gradient for 30km continuously. 120kg rider, 15kg bike, 20" (406) wheels, front geared hub motor. speed doesn't matter but I do understand that the motor will be happy if I keep it 20+km/h.

Controller
The controller is the easy bit, water/weather proof (by applying nail polish on the PCB and silicone the controller case), mount it on the bike frame and let natural air do all the work. if it doesn't, I will add as many heat-sink on the casing to make it works.
Actually, I reckon waterproofing the wires are more challenging... Yes, a Sine wave FOC controller if I can find one for hub motor. 20A with 5 levels if I can find any.

Been there, done that. Did my first frt. mounted geared mini about 8 years ago w/ the stellar, but a little hard to get, MXUS. Then mostly different variants of the Q100(Cute).

Controllers-I use a big 9-FET square-wave that only maxs out @ 20 Amps and I can keep in a bag no problem, but if you go w/ a sine wave, your weather challenge would be the display as much as the controller. They are weather resistant, not water proof. There are weather-resistant kits(MXUS), but short of that, the best approach for most E-bikes is for the the rider to wear a big poncho and cover the components w/ it and to just not ride in heavy rain.

I will stick to geared front hub. for convenient sake. If it works here, it will work elsewhere.
The hub will receive oil bath mod with ATF. I learnt that the coil varnish is rated to 150C, I also know wire rubber insulation for most high temperature electrical wires (for motor phase and halls) are 120C. so this leads to my design max. temp cut-off of 110C. Theoretically, any water ingestion should boil out at that temp given enough time, which is a bonus. Not forgetting to coat all wires and plug all holes with high temp RTV liquid gasket paste which usually has 250C temp rating. Use rubber seal bearing for the external hub bearing.
From many oil cooled hub projects I read on the forum, it seems that an air breather valve is missing from most projects. Breather valve is an old tested way to equalize internal pressure due to heat and expansion of the air and oil in the hub which could cause bleeding bearings and dripping wires, they are used everywhere, eg, transmission gearbox, engine block, differential gearbox, motor gearbox, gas tank, diesel tank, etc. The breather valve I found looks like a M6 bolt with holes drilled into it and built-in 0.07bar relief valve and oil filter, it should keep the oil in and water oil of the hub. not forgetting it can breath 300ml/min.

Complete waste of time.
A frt. mounted motor becomes starts to become a handful around 1000 Watts. I had a Q100H run by a Lynn 25 Amp Mini-Monster on 14S LiPoly(around 54 V nom.) and I could "lite up the tire" if I wanted to. Uphill starts, especially when the pavement was damp, required a deft touch to keep the tire from spinning. Also, at that power level, motor "hammering" starts to become a concern.
My point here is, one really can't run enough power thru a frt. mount to require any need for motor modifications, even w/ the diminutive Cute. Besides, my experience w/ over-heating geared motor problems, due more to extreme hills, not super high system Wattage, shows up, not in the motor or controller, but in the wires between. First the phase bullet connectors melt, then the phase wires themselves. The best way to protect from mini-motor system over-heating is to be careful about matching the motor speed range to the "over the road" speed desired and to be reasonable about the the steepness and duration of the hills trackled(Know and live by the 1/2 max speed when climbing rule).

That being said, I consider pushing tiny geared hub motor an engineering challenge, if we can achieve to pump 50Amp into an 250W hub motor, we can do a lot more for big DD motors.
Amps, by themselves, don't really mean much, as what is a concern is Watts. There has been plenty of documentation here of over-Volting geared minis to get a higher top speed(why would one "over-Amp" a mini?). One of the most notable goes back years when mckeefer decided he would over-Volt his MXUS to destruction. I think he had worked his way up to either 16S or 18S (LiPoly) when he cooked the windings. But the same results always crop up. Above 14S, the returns diminish quickly unless there is an like increase in Amperage to carry the motor up the power curve to the no-load point. And that spells destruction.
The limits of mini motors are well known and in the same way it's possible to make a moped go 50 mph by replacing pretty much every motor part w/. a custom piece, the costs build quickly build up and it become a "project".
For 90% of the mini-motor users here, if you need to go 25 mph, you will be better served to go w/ a bigger motor, like a MAC. The exception are those "road racer" types that can put a lot in w/ their legs. The same w/ hills. If your mini-system won't maintain at least half of the top speed(in the flat) up a hill, you need a system w/ a bigger motor.
Or two minis:)
 
FWIW, with the common ebike controllers (that cannot measure phase current and thus cannot really limit it), over volting is effectively the same as over amping, because increasing the voltage, using the same throttle settings, generally causes higher currents.

(which is why you get higher torque out of a the same motor at higher battery voltages than lower ones, all else the same).
 
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