Custom Full Suspension Flatbar Road bike build

[SamTexas]

No offense at all my friend (borrowing your line). I do promise to not discuss anything related to your expensive toy from this point on.

Looking forward to the comparison with the code 11.

 

[adrian_sm]

Not too surprised by the bomber stats. Bit like comparing a Prius to a WRX. Yes they are both cars, but to compare them just based on efficiency is a bit pointless.

More importantly, I am really looking forward to how the BPM efficiency stacks up. This type of hub motor is the main alternative to a friction drive IMHO. If they were just simpler and easy to install, and had similar efficiency to the friction drives, then the advantages of friction drives is going to be getting pretty slim.

- Adrian

 

[Samd]

Heya Kepler,
I just print 3d stuff thru shapeways in the netherlands (a division of phillips electronics in eindhoven). I model in google sketchup (free!), check the model in meshlab (free!) and upload it via their web-bot interface. Choose a material based on properties/tolerance/price. Pay via paypal for each cubic centimeter.
A few weeks later a UPS man appears at my door with my bits here in country Ballarat. Keeps the neighbours guessing....

I will bring some material samples. Alumide (nylon and aluminium powder mix) would be interesting - the final sandblasted surface might be worth a shot. And ABS plastic too. You could knurl a brandname in....

It can be pricy if you don't design a lot of mass out. Which is easier than in traditional design.
What's the diameter of your 3 phase motor?

SD.

 

[Alan B]

I would think a knurled aluminum thinwall tube would work out nicely for your friction layer. Easy to make on a lathe. Turn the outside, knurl, then turn the ID out to fit.

 

[Kepler]

I think it would be easier to just strip the motor, spin up the can in a lathe and use a knurling tool directly. I plan to try this in the near future.

In the meantime, I decided to attack one of my motors with a die grinder using a coarse bit. Results were a kind of dimpled finish that should provide a bit of improvement in grip in comparison to a the standard smooth metal finish.

 

[Samd]

Hmm, laser sintering is pricy. With a motor diameter of 80mm even a 30mm wide by 1.5mm thick laser sintered ABS knurled band will set you back 20+ bucks plus postage.

I have seen some shims made in the past by electrically contact welding metal fly wire to thin metal shim. I wonder if you could use contact adhesive to bond metal fly wire to flexible/thin metal sheet and cut out shims that were easily replaceable?

What about a rubber sleeve that stretches over your motor case?

I am still buggered if I can work out how you get the motor chassis to rotate while the wires don't spin. Maybe I am trying to hard to figure it out....

 

[amberwolf]

I am still buggered if I can work out how you get the motor chassis to rotate while the wires don't spin. Maybe I am trying to hard to figure it out....

Only one end of the can spins; the other is fixed to the axle/shaft (with the stator/windings also fixed to the axle/shaft)

 

[Samd]

Aha! Eureka moment for me! Thx for that!

 

[Samd]

Another idea, try googling "expanded metal tube"

Some Links:
http://www.alibaba.com/product-gs/334020215/stainless_steel_filter_mesh_tube.html
http://www.alibaba.com/product-gs/501273414/many_kinds_of_perforated_round_holed.html
Free samples.

If you can find a cheap ryco air filter at 80mm dia maybe you are in luck with a couple of steel cable ties from bunnings?

 

[amberwolf]

Do all outrigger motors with the wires on the output shaft end allow the can to spin?

By definition, the outrunner type of motor spins it's can. The inrunner type spins the shaft.

 

[Jimbo]

That is a quality build.....hats off to you, very nice indeed!

I'm thinking of doing something similar, maybe based on a full sus 29er or a full sus road bike (if they make them?) Perhaps a Moulton would be sweet....anyone done a Moulton conversion yet?

I love reading about quality builds like this - so much to inspire me to get out in the garage!

 

[Samd]

Been thinking more about this build as it seems really slick after having ridden alongside two on the weekend for 30km (and often behind!).

It struck me that the units seldom used peak power. And perhaps it was actually torque that mattered. So perhaps there is merit in halving the can diameter and doubling the rpm per volt rating?

Pros: Cheaper motors?, maybe better takeoff acceleration due to the ratio of can diameter to wheel dia?, lower weight, smaller size for stealth.
Cons: motor burnout? smaller bearings and shaft too small for loads? small can radius may reduce the ability to create friction contact surface?

I am thinking along the lines of these motors (38mm and 42mm can dia with 5mm shaft):
http://www.hobbyking.com/hobbyking/store/__14740__Turnigy_L3040A_480G_Brushless_Motor.html
or
http://www.ebay.com.au/itm/320797399417?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

I am posting because I am keen to see if anyone else has done a motor of smaller size again.
BTW let me know if you want me to move this to a seperate topic - hope I havent hijacked your thread Kepler!

 

[Hillhater]

Smaller dia motors generally produce less torque, so what you think have you gained in reduced "drive" diameter, you lose more in motor torque.
kepler has used 50mm dia motors before and they work fine , but samller means more rpm and more noise...
..Personally, i believe the bigger motors are a better solution, more durable, but its difficult to find them with low enough Kv to allow a high voltage/low amp set up.
The best solution , is EV Todds, where he uses the motor to drive a small roller (1" ?) in contact with the tyre. That allows higher rpms to be employed and obviously a better volt/amp ratio.
..but then you have a more complex drive with bearings, clutch etc to deal with. :?

 

[Kepler]

Forget about what the advertised power capability is saying. With these cheap motors its nowhere near it when dealing with bike drive application. Halve it and you are getting close. Look more at the weight of the motor. More weight typically means more copper and as such better ability to handle heat. You can get away with 500 gram motor but it needs to be limited to under 500W. The motor on this bike is a 750 gram motor and has a 63mm diam. From memory its a 240 kv motor. It would probably get away with 1000W limit but even at 800W continuous, it can get quite warm. I still recommend the 63-74 200kV as the best all-round choice. It will do 1000W all day and has a nice big skirt bearing supporting the can. Adrian had one of these on his bike.

 

[Hillhater]

I notice HK have a 6374 SK# motor with a 149 KV listed ...could be useful ??
http://www.hobbyking.com/hobbyking/store/__18184__Turnigy_Aerodrive_SK3_6374_149kv_Brushless_Outrunner_Motor.html

 

[Kepler]

I notice HK have a 6374 SK# motor with a 149 KV listed ...could be useful ??
http://www.hobbyking.com/hobbyking/store/__18184__Turnigy_Aerodrive_SK3_6374_149kv_Brushless_Outrunner_Motor.html

That one might be a good candidate for an 8S or even a 10S setup

 

[adrian_sm]

I have a few of the Turnigy Aerodrive SK3 - 6364-190kv motors. The build quality is really nice. But they are not 63mm diameter motors as the name would suggest but actually ~59mm. Good skirt bearing, and an internal fan as part of the can support, thicker magnet wire used than other HobbyKing motors.

The main thing that I didn't like about them was that the cooling slots in the can are on the edge of where the friction drives typically contact the motor. So they may allow more ingress of dirt. And the other is that they seem to have a higher pitch noise when running than other motors I like, which I find more annoying.

Sorry if getting a bit off topic.

- Adrian

 

[Kepler]

Ok, the BPM geared hub motor has been fitted and tested with its first full shakedown ride completed today. The ride was identical to what I had tested with the friction drive and I made a concerted effort to use the same riding style. Total distance was 30km each way.

So here are the results. (Drum roll)
Friction drive: Test 1: 6.6 Wh/km Average speed 27kph
Friction drive: Test 2: 7.5 Wh/km Average speed 29kph

BPM geared Hub drive: Test 1: 7.7 wk/km Average speed 28.7kph. (to work)
BPM geared Hub drive: Test 2: 8.7 wk/km Average speed 26kph. (home from work with a slight headwind)

I am really impressed with the performance of the geared hub motor. I have set this motor up with 15S Lipo so 60V hot off the charger. Being a Cole 11, it has no problems hitting 50kph at this voltage and pulls really well with my 12 fet Lyen still set at 40A. The hub motor setup has added 4kg to bike but pedals just as easily as the disengaged friction drive setup.

Negatives: Well the bike is now an electric bike rather then an electric assist bike. Also its lost much of its stealth appearance. Not so easy to fix a rear puncture now either.
Worth mentioning that this is not a cheap hub motor setup with the fully built wheel coming in at just under $500.00. That being said, I would still highly recommend one of these little power houses if a hub motor is on your shopping list.

 

[adrian_sm]

Looks pretty stealth to me. The controller sticks out a bit, but the hub hides nicely behind the cluster and disc.
The battery bag is a bit in your face, but you were running the same bag for the friction drive set-up too.

Economy stats were interesting. Not much in it, but appears to hand the friction drive the medal.

Couple of questions.
1) How close were the riding/throttle styles? Did you use the hub at all from a standstill?
2) 15S @ 40Amps or 2000+watts for the hub. What was the friction drive restricted to? I find with higher power setups, I tend to us the assist more for acceleration, than maintaining speed which kills efficiency.
3) What are the no load speeds of both setups?
4) How long does the wheel take to spin down from full no load, to rest when the wheel is in the air on both? It is a good sign that it feels free rolling on the road.
5) Is the 4kg weight gain including battery, or not? Bit unfair if it includes battery as the wh's may not be the same.

Anyway you look at it the efficiency stats for the bike in either guise are pretty darn good. Well done on a beautiful build.

- Adrian

 

[Kepler]

Looks pretty stealth to me. The controller sticks out a bit, but the hub hides nicely behind the cluster and disc.
The battery bag is a bit in your face, but you were running the same bag for the friction drive set-up too.

Considering I only had 3 x 5S 5000mah packs in there, the aerowedge could have been used no problems. Just that I was carrying a charger and extra tools just in case. Certainly the aerowedge will look much better in relation to a stealth appearance.

1) How close were the riding/throttle styles? Did you use the hub at all from a standstill?

Most take offs were with a little assistance from the hub motor, a definite advantage for the hub but with a consumption cost of cause

2) 15S @ 40Amps or 2000+watts for the hub. What was the friction drive restricted to? I find with higher power setups, I tend to us the assist more for acceleration, than maintaining speed which kills efficiency.

Friction drive was limited to 800W. I was very careful in the test to use only light throttle. I doubt I went over 800W during the ride. Because I had an adjustable throttle on my friction drive, I was using the friction drive to maintain speed also. I used the same riding style with the hub.

[3) What are the no load speeds of both setups?

I haven't checked this but I think the hub would win here.

4) How long does the wheel take to spin down from full no load, to rest when the wheel is in the air on both? It is a good sign that it feels free rolling on the road.

Spin down is very impressive. Like a normal bike freewheel.

5) Is the 4kg weight gain including battery, or not? Bit unfair if it includes battery as the wh's may not be the same.

I was carrying a similar amount of battery for both. The friction drive setup I was using on this bike was about a 1kg. The hub is 4.5kg and the controller is about 800G

Anyway you look at it the efficiency stats for the bike in either guise are pretty darn good. Well done on a beautiful build.

Thanks Adrian. I agree, the stats are great for both setups. To be fair, I think it is difficult not use the Hub more when riding even if you are trying not too. The power is seamless and as you pointed out, the drive is used off the mark.
I am surprised how close they actually are. After seeing SamTexas super economy figures, I was expecting kind of the same but it certainly wasn't the case for my setup. It could be argued that because mine is a high powered setup (couldn't help myself), this is causing the higher consumption. However, I was really careful to use very light throttle movements plus High Volt setups have a slight efficiency advantage also.

Need to mention the power available in this setup. I was shocked and super impressed. Being use to a 9kW Bomber everything else feels a little tame. This geared motor at over 2000 Watts feels more like 4000W and pops up the front wheel off the mark without a problem. Might need to hold a set of planet gears in stock just in case

 

[SamTexas]

After seeing SamTexas super economy figures, I was expecting kind of the same but it certainly wasn't the case for my setup. It could be argued that because mine is a high powered setup (couldn't help myself), this is causing the higher consumption.

Yes, mine's a 350W rated hub. BTW, I am not the only one reporting those super economy figures, there were at least two other members who reported even better economy than mine. Max power on that 350W hub never exceeded 750W (44.4V 18650 Lipo and 17A controller).

The problem with these tests, however consistently done, is that there are too many other varialbles at play. Terrain, weight, riding style, riding posture, wind condition, quality of the bicycle drive train, tire size, pressure and thread pattern. However back to back test using the same bicycle and same rider (like your case) is usually sufficient for relative comparison. I just wished you did not use the throttle on starts to keep it "apple to apple" with your friction drive.

 

[adrian_sm]

Can you use the new RC CA on both setups?

That would be able to enforce the same minimum speed, and limit power to the same limits which would be about as close as you can get.

Or just drop the amps on the BPM controller to match the friction drive power, and always pedal off from the lights.

 

[Kepler]

The RC CA's would need some modification to use with the hub motor so that isn't going to happen. I will re program the controller to 800W and run it on 48V for another go at this comparison. Also I will try not to use it until the bike is doing 12km which is the start point I was using on the bike with the friction drive. Thats about as fair as I can make it. To be honest, I dont think it will make that much difference though. Going by the "feel" at the end of the ride, both felt quite similar.

I am personally satisfied that the friction drive can match the very best hub setup when it comes to efficiency. In relation to a mix of efficiency and power on tap from a startup, the geared hub motor is clear winner. I dont think that would surprise too many people though

 

[SamTexas]

Also I will try not to use it until the bike is doing 12km which is the start point I was using on the bike with the friction drive. Thats about as fair as I can make it. To be honest, I dont think it will make that much difference though.

I think (purely from a technical standpoint) that the difference will be significant. Accelerating from zero is always the most power hungry portion of the ride. Good luck and have fun.

 

[SamTexas]

I will re program the controller to 800W and run it on 48V for another go at this comparison.

I'm not sure how much that'll help. Isn't it true that the motor windings are different for different motors? Aren't they supposed to be optimized for certain terminal velocities? Won't a V6 Camry consume more energy than a I4 Camry even when they are driven the same way?

I know for a fact that my DD 9c 2807 always consumes about 20% more energy than my 350W geared hub under the same riding condition. Although the average speed is the same, the 9c always accelerates faster.