Ultimate Torque DD Hub motor at 48V? Using as "Mid Drive"

[LI-ghtcycle]

Hello all, as some of you have seen, I have been trying to figure out the best way to get a high torque, hill climber that will move around a 150lb cargo/touring bike.

I looked into the RC route, and it seems to be over my head, and now I am looking into the "Mid Drive" DD Hub motor option, however, not your typical mid drive.

This motor will be running something around a 2 to 1 reduction or less using typical bicycle single speed chain, running a freewheel to a fixed cog attached to a Nuvinci hub.

My main purpose for this bike is to make the hills and weight of the cargo bike go away, I will be pedaling as much as I am able (there will be days when I can only offer 25% or less of the effort to get the bike down the road) but I want to at least be able to go normal bike speeds (typical bike, not 150lb loaded touring bike speed. ) up very steep grades I will face in a coast to coast trip across the USA.

My goal is to use as much off the shelf stuff as possible, I am willing to have a few specialty machined parts, but only ones that will allow the use of off the shelf typical bicycle parts.

My original vision was to over-volt a low voltage hub motor (24V over-volted to around 30V) but that has proven too impractical, and I am not wanting to make a "hot rod" that screams down the road, I want a "John Deer" that is still capable of 20 - 25MPH on the flat in most conditions, and hopefully will climb a 10% grade at 15MPH (but this isn't a need, just a want or hope hehe) with both the first stage of gear reduction going to the Nuvinci, and the Nuvinci hub being the final stage so that I can adjust the speed with under and over drive to get around 8 - 30 MPH no load speed, and according to various calculators, this will be ideal with a motor that:

A) Runs at about 300 RPM at in it's most efficient voltage/amperage,

B) Can put out 1300 Watts continuous with out getting too hot while I climb a long hill.

I will be most likely ventilating and active cooling the motor that will not be exposed to the elements, and will be controlled with an adjustable or standard 30A max controller, at 45V nominal or 1350 Watts.

The hope is that the Hub motor can be kept at it's ideal RPM's, (I will have my Trail Tech Vector to keep tabs on the temperature of the motor too) so that it is always near or at it's most efficient and that speed will be reduced to keep this efficiency if needed, but hopefully I will be able to get close to these goals by use of the 3.5 to 1 reduction provided by the Nuvinci.

These calculations have taken into consideration the weight being hauled (bike, rider, touring gear) of approximately 350lbs (actual should be 325, but I'm over building it) going 15 MPH up a 10% grade.

I had hoped that there would be a smaller DD hubbie that could be more compact than even a 9C since the motor should be running at it's best efficiency, but I can even go up to a X5 or X4 motor if that is going to make this work better.

Strength and performance is more important than weight, however, if I can stay to the weight of a 15lb 9C motor or less, that would be better than a 27lb X530x or X540x.

Price is also a factor as is availability.

Thanks!

 

[dogman dan]

Since you want compact, Clyte 408 or 409. Or even 4011. The slower the motor the higher you'd have to gear it.

Once you go gear drive, just about any winding would run cool compared to lugging in a rim. you simply adjust your gearing accordingly, and run the motor at the same revolutions as it would go in a rim with a light bike at full throttle. I think a 408 is the way to go. Ask Justin what is in the stokemonkey kits. In fact, why not just buy one of those?

Btw, A 9c front hub in 6x10 winding will do what you are asking. So would a 5305 At 48v it should, with pedaling help, grind up 10% grades easily for up to an hour at a whack. Possibly longer if ventilated. Just pull tape off the holes for the big climbs. In scenery like that, a 30 min ride and a 30 min enjoy the view break is not such a bad idea anyway. Once back on "normal" terrain a 6x10 would chug along at 18 mph on the flat all dang day in just about any weather.

 

[pdf]

The Stokemonkey in an Xtracycle is hard to beat. I've almost never started a do-it-yourself project and said at the end, "Yeah, all that money I saved was totally worth it!", esp. one that requires machining parts and custom fitting. Also, the result often ends up looking like heck and not working as well as the ready-made option. If you already have the bike and it is not an Xtracycle-converted frame or Big Dummy, then you might have to go a different route or get creative. The Stokemonkey is designed to go with one of these set-ups.

The Stokemonkey is built, mostly, of stuff you can get at a well-stocked bike shop. Most of the parts that would break or wear significantly are standard bike parts. The frame clamp and motor bracket are specialty parts, but I can't imagine anyone damaging these parts. They are seriously well-built. All the rest is off the shelf (freewheel, cabling, left side crank and ring). It really is a well-designed system. If any system will do what you want, I'm betting on the Stokemonkey. If it weren't for the hill-climbing, I'd seriously consider a large hub motor, but with that much weight, you are going to need all the gears or a big motor and the ability to shed heat (not to mention some monster batteries).

I have never toured with 150 lb bike but I have frequently carried that amount of weight home from the store (including the bike) up 15% grades. And I didn't do it at 15 mph. Carrying 150 lbs every day for the distance you've set is going to require a system with the bugs worked out or you can work them out yourself as you go. I now have 2750 miles on my Xtracycle/Stokemonkey system. The only significant problem I've had was a worn-out bottom bracket, but the one on the bike was a cheap one and the cage for the bearing basically came apart in the BB.

Please keep a log of your journey. I'd like to hear about it. if you haven't seen the Murtle the Turtle thread, check that out. Sounds like a kindred sprit.

 

[LI-ghtcycle]

Thank you both for your suggestions, and the main reason I would not go with the stoke monkey is the BB as jack shaft and no freewheeling crank, that is a real non-starter for me. I like the concept however, and I am definitely borrowing from their design. I was just at clever cycles yesterday, and I was impressed that they had so much stuff that I would want to have in stock, including a seat sandwich for mounting my B72 to the Tidal force seat post.

I haven't decided where exactly I will mount the motor, but I am most likely going to put it above the rear pannier rack ( I have those heavy duty basket panniers, and they are reinforced) or if possible, just above the Top Tube in front or just behind the seat post.

Heading soon to get my Nuvinci laced today, but gotta re-do my brake levers and shifters. I'll make a ghetto picture from a pic of my Tidal Force Frame to show you what I have in mind later today.

 

[pdf]

Cool. Can't wait to see what you come up with.

 

[John in CR]

... or if possible, just above the Top Tube in front or just behind the seat post.

The thought of rain gear or other clothing getting caught up in a spinning motor with chain sounds like a bad idea. You're virtually guaranteed to break a chain at least during testing, so I wouldn't want that motor or chain anywhere near any part of my body, especially my entertainment device. I've got all my reproducing out of the way, so it's just for fun now.

John

 

[LI-ghtcycle]

LOL!! :lol: :lol: :lol:

Good point John, If I did put it near the "play station" I would definitely have a complete chain guard around it, however, I might have found an even better spot, behind the seat-post with brackets between that and the rear basket panniers. Plenty of places to mount to there, and even if a chain brakes, the worst it would do it hit my back, but even then I think I would have at least a half-chain guard.

 

[Rassy]

pdf mentioned "Murtle the Turtle", except it is "Myrtle the Turtle".

http://www.crazyguyonabike.com/doc/myrtle

+1 on being good reading before going on a lone electric bike tour. Sylvia spent a night with my wife and me on her tour down the coast last spring.

I have mentioned before how happy I am with my 9C 6X10 that runs as a mid-drive though a Nexus 8 speed internally geared hub. I agree that a smaller diameter motor would be easier to install.

As far as weight, speed, etc., there are just so many variables. Since I am currently using a 10AH Ping, I usually go up the 15% grade in low gear at 6 MPH. This limits the max current draw to 15 amps. My input makes almost no difference.

If I use a higher gear and add some pedal effort, I can maintain about 10 MPH on the same hill, but the current draw goes up to the controller max of 23 amps. I am sure you could maintain higher speeds with the right batteries and controller, but as others have found out, there is a point where the 6X10 will smoke.

 

[LI-ghtcycle]

Thanks Rassy, good info, I have been debating the 8 x 8 VS 5 x 12, and everything I am seeing so far puts the 5 X 12 in the arena I want to be in, high torque, and hopefully this will translate to around 15MPH+ up a 10% grade with a heavy bike (This is with the proper gearing reduction and using the Nuvinci as final drive). The other day I was maintaining 20 MPH up about a 4 -5% grade with my 9 X 7, but that wasn't with any weight to speak of, it will be a lot different with a fully loaded bike.

 

[John in CR]

Thanks Rassy, good info, I have been debating the 8 x 8 VS 5 x 12, and everything I am seeing so far puts the 5 X 12 in the arena I want to be in, high torque, and hopefully this will translate to around 15MPH+ up a 10% grade with a heavy bike (This is with the proper gearing reduction and using the Nuvinci as final drive). The other day I was maintaining 20 MPH up about a 4 -5% grade with my 9 X 7, but that wasn't with any weight to speak of, it will be a lot different with a fully loaded bike.

Not for a mid drive. First, spinning faster means better cooling for the motor. You can gear to whatever you need via your chain reduction from the motor to the wheel. 2nd, an 8x8 has the best copper fill, 64 strands of copper on each tooth vs 60 for the 5x12. The 5x12 is a better climber in the same size wheel, but look at your wheel as whatever size you want it to be, and the 8x8 is the better more efficient motor due to better fill in what is otherwise an identical motor other than the gearing. You already have a 9x7, which will also work fine for your mid-drive.

 

[LI-ghtcycle]

Thanks Rassy, good info, I have been debating the 8 x 8 VS 5 x 12, and everything I am seeing so far puts the 5 X 12 in the arena I want to be in, high torque, and hopefully this will translate to around 15MPH+ up a 10% grade with a heavy bike (This is with the proper gearing reduction and using the Nuvinci as final drive). The other day I was maintaining 20 MPH up about a 4 -5% grade with my 9 X 7, but that wasn't with any weight to speak of, it will be a lot different with a fully loaded bike.

Not for a mid drive. First, spinning faster means better cooling for the motor. You can gear to whatever you need via your chain reduction from the motor to the wheel. 2nd, an 8x8 has the best copper fill, 64 strands of copper on each tooth vs 60 for the 5x12. The 5x12 is a better climber in the same size wheel, but look at your wheel as whatever size you want it to be, and the 8x8 is the better more efficient motor due to better fill in what is otherwise an identical motor other than the gearing. You already have a 9x7, which will also work fine for your mid-drive.

You know John, I'm a little slow, but I'm coming around.

I just came to this very same conclusion on my own!

I'm going to use the 9 x 7 that I have atm and see what happens when I run it. I also have pleasantly been surprised to find out that not only can I get fixed cogs that spin onto standard freewheel threads, I can get them cheap!

I know that there are probably cheaper sources, but considering these are heavy duty, I'm thinking they might be just the ticket!

http://surlybikes.com/parts/fixed_cogs/

I can simply "piggy back" one of these cogs onto the Nuvinci freewheel adapter, followed by the pedal freewheel, and vioula! I have a solid drive made from 100% off the shelf bicycle parts, and although I can't get the cogs at any old bicycle shop, I CAN get them pretty easy at specialty shops, and I can always carry a few with me on the road if needed.

The plan now is to run a 13T cog on the drive hub to a 22T cog (the EXACT tooth count my reduction needed! go figure! ) and now with the Nuvinci being the final drive, I can gear for as low as 7.4 or as high as 25.8 which will be plenty fast for my cargo bike!

If the 9 x 7 isn't ideal, I can change the gearing accordingly. Best part is I have the carcass of the exercise bike that I salvaged a freewheel I have, and it has a nice bracket already pre-fabbed for me to attach to basket panniers!

I ran out of time today, but in the next few days I should have time to get pics of the bike and such in the light so this will make more sense.

And the best part is, if I decide I want a bit more speed, just adjust the gearing! I'm thinking this will be perfect for my use as 7.4 MPH no load speed will translate to some seriously slow "Johndeer" gearing to take a heavy load up just about anything I will find along my trip, and I don't see why I shouldn't be able to make a solid 20 MPH even in a headwind with minimal pedaling at the top, and since none of this is going to put me way over the speed of a normal pedal cadence, I should have little trouble pedaling along.

P.S. Some will ask "why the fixed cogs?" answer? Regen braking to save my brakes on steep descents. 8)

 

[dogman dan]

Maybe I'm missing something, uninformed,. But would regen tend to unscrew that fixed cog from the motor? Mabye you can sort of locknut it on with a disk brake adaptor as the locknut.

I think the 9x7 will work fine, you just have to gear it to spin the motor the same speed as if in a 26" wheel at 25 mph. So when you are grinding a hill at 6 mph, the motor is spinning fast.

 

[LI-ghtcycle]

Maybe I'm missing something, uninformed,. But would regen tend to unscrew that fixed cog from the motor? Mabye you can sort of locknut it on with a disk brake adaptor as the locknut.

I think the 9x7 will work fine, you just have to gear it to spin the motor the same speed as if in a 26" wheel at 25 mph. So when you are grinding a hill at 6 mph, the motor is spinning fast.

You are exactly correct, it will want to unscrew. They make a lock-nut for these cogs, but I am thinking I will use a spare freewheel as a lock-nut just so I don't have to buy the lock-nut, and it will be a good way to carry around a spare.

I'm hoping to get the speed up closer to 15 MPH on a 10% but with all the weight, I will probably be going slower, but the main thing is I will have motor power to save my knees and if I am too fatigued, I can keep on the road, so even slow with little to now pedaling will be fine.

 

[John in CR]

Regen? Would the Nuvinci force you to pedal if you have no freewheel on the hub? My 3 speed Nexus is definitely not that way. ie The cog at the hub is fixed, but in normal designed use would coast without pedaling just fine. That means on mine definitely no regen with a mid drive unless I did something kinda awkward like run a second chain on the left side that freewheeled for motor pull, but not turning force from the wheel. That would probably get weird and problem filled with the 2 different rpms on the 2 sides.