Alan B wrote:Or get a Cromotor. Wait, this is a 2wd thread. Never mind.
Ian wrote:Alan B wrote:Or get a Cromotor. Wait, this is a 2wd thread. Never mind.
Hi Alan - read thru the cro thread and too big n'heavy for me I think- although I will keep an eye on people's experiences of it for lower speeds and modest power levels like mine.
Anyways apologies if my post was not totally on-thread but it is an attempt on my part to resolve the right design 2WD in my particular circumstances. Which I think is defintely worthy for 2WD. I am satisfied that using 1 battery of correct capacity, 2 identical controllers and 1 throttle is straightforwards and tried and tested. The evg frame fortunately is robust with strong front forks so again a good candidate. I need something similar in efficiency as my current 9c, at speeds 22mph and under. I get around 2 miles per ah in normal use, which is WOT on the hills, fairly easy cruising, then all the downhills.
At this time, I don't think there are even that many choices. 2 x 9C is to heavy. 2 x magicpie too heavy. 2 x smaller DD hubs might work but too much drag? Are there any mid-size DD hubs however, worth consideration for a 'middle of the road' 2wd setup?
So what I see as the only real choice is 2 of the 500w geared from cellman or 2 smaller geared hubs such as bafang. I don't know if a smaller geared hub even when doubled up will be strong enough or temp resistant over the long haul, so I would like to read anyones experience or crunch some numbers as it is definitely a stealthy look and good weight. 2 x cellmann 500w seems on paper to be the best choice. It means that weight remains about the same as my current 9C and also means I can configure my battery packs to go down to 40v and attain a capacity of 40ah, use a slow torque winding to get around a 22mph top speed, and tackle steep hills at a 'sweet spot' for each motor, around 12 to 14mph at say 800w draw on each for no longer than 1/2 to 3/4 of a mile at a time.
The benefits seem to be that I would gain greatly (in comparison with the 9c) from thermal efficiencies when going majorly uphill, freewheeling with pedal assist on the flat helps a bit more, and never overstressing the system at any point. Even at my highest theoretical draw of 20amp per motor, I am still only 1C on the battery pack, and when cruising on the flat from 18mph to 20mph, I would still expect to use only 350w combined or 175w on each hub - total 9amps on the battery or under 1/4c. Therefore, I should get a theoretical range of 70 -80 miles minimum on level road, is that correct?
Well I will keep learning and looking through all the posts and see what others have already experienced!
wojtek wrote:If i refer to auto industry, the whole point of AWD is when you lose traction in some wheels, the other will take over.
The only useful usage that would increase fun considerably would be to have AWG off road trike, used in extreme offroad conditions and on snow [putting aside the complexity of 3 WD]
I can't really see enough benefit of putting 2 motors on a standart bicycle. Put aside all the technical and mathematical calculations that some of geniuses has done here [full respect]
rojitor wrote:Ever since i turned my bike on a 2wd i noticed more stable rides, the weight at the front wheel makes a good balance, on top of that i can keep top speed climbing,sometimes i even pass gas motorcycles going uphill and i always know i can make it to home if i have a problem.Maybe with a cromotor or 54xx at the rear it is not so cool, time will tell.
Alan B wrote:The Cromotor is so wide there is little room for freewheel cogs and would not fit in most front forks. But 2 of them would be quite interesting.
Ian wrote:asked for quote from cellman for 2wd setup based on fishamsterdam feedback, who has 500w rear and 350w front and likes it. hoping for 1000w torque on the rear and same on the front but front doesn't appear to be available, so it may have to be one of his 350w with the matched rpm winding I figure?. Still if you can actually run 800W continuous rear and 300W continuous front, keep at a respectable (and efficient) 13mph to 15mph with a spot of pedaling, and it all works thermally in the summer for 12 mile from 900ft to 2800ft, then I am in. Also asked lyen about a custom dual motor controller - be cool to just have one unit, programmable for both motors and not ridiculously massive like that crystalye dual controller, don't see why not he's an electronic wiz. will post how it goes and what options are recommended by the pros.
Ian wrote:Ian wrote:asked for quote from cellman for 2wd setup based on fishamsterdam feedback, who has 500w rear and 350w front and likes it. hoping for 1000w torque on the rear and same on the front but front doesn't appear to be available, so it may have to be one of his 350w with the matched rpm winding I figure?. Still if you can actually run 800W continuous rear and 300W continuous front, keep at a respectable (and efficient) 13mph to 15mph with a spot of pedaling, and it all works thermally in the summer for 12 mile from 900ft to 2800ft, then I am in. Also asked lyen about a custom dual motor controller - be cool to just have one unit, programmable for both motors and not ridiculously massive like that crystalye dual controller, don't see why not he's an electronic wiz. will post how it goes and what options are recommended by the pros.
Cellman replied re 2wd drive setup. He recommended 500w rear and 350w front, matched motors so for me a 10t wind running at 40v will get me over my 20mph target cruising speed. Shipping is $150 x 2 though. So figure around a grand to get set up. It seems like this is a very strong & reliable option and I like the idea of being able to get spares too just in case, although I'm not a high power user, for me its just for relaxation and watching the scenery
I also am considering the idea of cellman 1000w rear motor and mxus 350 min-motor on front, but with two seperate throttles. Would cut down on the overall noise and also perhaps be more efficient, once you get real world experience of the 1000w motor's thermal limits up hills, then it would be a simple matter to just dial in another 400 to 500 watts of pulling power from the front wheel. I would have thought a combined 1200 watts from 2 brushless geared motors spinning at high rpm to be faster and more efficient up any hill in comparision say to my 9c 2810 pulling 1200watts up same hill, which is still good but really likes to be running at 14mph or more and so you got to run at high voltage.
I see e-bike kit are also saying they are working on a warrantied dual drive (in their faq). Also hightekbikes do dual drive systems so am checking in to that.
I did ask Lyen about just one controller for both motors. I know he does one buts it's quite big. He will get back to me after his race and perhaps it is possible to downsize and even develop a controller that's programmable for both motors.
Hangdog98 wrote:So I've been following this with keen interest and I started to do so because I wanted to experiment with dual Q100's on a road bike running a single battery. When I began this journey into 2WD I was hypothesising that two motors would provide double the available torque of one motor OR for my application, the same torque at half the Amps on a given hill, with half the heat, give or take. This is my reason for considering two motors though I'm still not sure if this is correct. Can anyone provide this answer
If you feel compelled to tell me that I only need one motor twice the size, please try and resist the urge, I get that. I want very small lightweight under-stressed geared hub motors for this build.
Regarding the throttle(s), I planned a mechanical solution instead of an electrical one by grafting the two throttle mechanisms together on the one twist grip, keeping their wiring intact and running them to their respective controllers. Has anyone tried that solution?
Kingfish wrote:Generally you will consume more power than one motor doing all the work, and less than two motors sharing the load. The best use of 2WD is starting off the line and hill-climbing. The least benefit is when cruising on level ground; often one motor just tags along and lets the other take the load – or they go into contention if the two wheels and controllers are set identical. To prevent contention on my ebike, I deliberately set each wheel to a different physical size, and overtly set the power-levels different as well which worked out pretty dang well.
If you are looking to gain efficiency – this is not the thread for you. The fact is that 2WD can and does provide about twice the torque to the ground over a single motor at the same power; two motors individually set to X-wattage will push roughly twice as fast as a single motor set to X-wattage. Another way to look at it: 2WD will get off the line and climb hills faster and cooler than a single-wheel at twice the power; two motors using a total of X-wattage will outperform (though at an economic price) a single motor at the same X-wattage. The downside to 2WD is that you have twice the weight and twice the freewheel drag, but then you get twice the regen braking.
There is no free lunch: 2WD will use more power than a single-wheel drive.
It’s also a heck of a lot of fun! KF
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