Hub "Mid Drive" Build

[Rassy]

Well, now I understand probably the main reason that the stoke monkey is a LH drive. Since I am using the motor, or hub to turn the sprocket, instead of a chain turning the hub, the motor's torque is now un-threading the sproket!

Yep, That's why my mid-drive hub motor is "backwards" and the chain wraps under the sprocket. When my first freewheel gave out I did exactly what you did, but the lockring only had to keep the sprocket from unscrewing when I was pedaling without using the motor. I had used lock-tite and it worked fine until I got the ENO, but even after using it for a while it was still pretty easy to get it off, so without some sort of a key lock I wouldn't expect it to work against the power of the motor.

[LI-ghtcycle]

Well, now I understand probably the main reason that the stoke monkey is a LH drive. Since I am using the motor, or hub to turn the sprocket, instead of a chain turning the hub, the motor's torque is now un-threading the sproket!

Yep, That's why my mid-drive hub motor is "backwards" and the chain wraps under the sprocket. When my first freewheel gave out I did exactly what you did, but the lockring only had to keep the sprocket from unscrewing when I was pedaling without using the motor. I had used lock-tite and it worked fine until I got the ENO, but even after using it for a while it was still pretty easy to get it off, so without some sort of a key lock I wouldn't expect it to work against the power of the motor.

Yeah, I am thinking the realistic solution will be a splined cog, and having this now damaged thread converted into a splined shaft with a similar pattern as the Nuvinci's freewheel adapter.

I would be still unable to take advantage of regen braking even if I just ran it LH drive, so I'll see what I can work out.

I got some heavy duty lock tight, but I'm not going to trust it unless it holds up to about as much force I can put on it by hand with a chain whip to take it apart, and even then, it's tenuous since I know that the hub motor will put out much more torque!

[LI-ghtcycle]

Well, I am going to try it out, the lock-tight seems to be holding, but I think in the end I will either end up using some form of splined drive, but if the lock-tight will hold, I can live with that.

I also like how the track hubs do it, having a left hand threaded lock ring that contacts the track cog in such a way that if it tries to loosen, it just tightens up the lock ring, however, that would require turning the hub case, and if I can avoid going to that length, I will.

Most likely I will end up using something like either the curry electro drive or other motor that normally turns a bicycle chain, possibly a cyclone motor (the 1000-3000 Watt one with no gear head) but for now, I will test this one out.

[amberwolf]

You could just dremel out a deep rectangular groove in the threads, parallel to the axle, on both the hub threads and the sprocket (or freewheel) threads, and then insert a steel block into that groove. It'll act as a locking pin to keep them from moving.

Make it a bit longer than the groove so you can pull it out with vise-grips or similar, and you can then relatively easily remove it for repairs or gearing ratio changes. Use loctite on it to keep it from just falling out if you like, but mostly the forces across it's short side by the opposing faces of the groove will prevent it from moving along it's length.

[LI-ghtcycle]

You could just dremel out a deep rectangular groove in the threads, parallel to the axle, on both the hub threads and the sprocket (or freewheel) threads, and then insert a steel block into that groove. It'll act as a locking pin to keep them from moving.

Make it a bit longer than the groove so you can pull it out with vise-grips or similar, and you can then relatively easily remove it for repairs or gearing ratio changes. Use loctite on it to keep it from just falling out if you like, but mostly the forces across it's short side by the opposing faces of the groove will prevent it from moving along it's length.

Yeah, I could do that, but if I get that involved, I would want a more "off the shelf" replacement sprocket, otherwise if I broke down on the road, I would need to dremel out the replacement sprocket too.

[LI-ghtcycle]

Got some rides in finally!

Really put it through the paces, took it across the street to an extra long drive-way that is well paved and was a bit disappointed, the flat road speed is the same, the motor just can't give me any more than it's already got at this voltage (12S, 44V of 25-50C Nano Tech LiPo).

I should have realized that, but seeing the 38 MPH no load speed got me excited!

Now, the important part! Climbing the hills. Fortunately for me, I have a 8% grade ravine about 2 blocks from my house, so I could do some hill climbing in the lower gears, and again, the motor is the same, so it didn't really climb any better, maybe gave me 1 MPH more going up the hill, but as JRH's says:

Volt up, Gear down!

I am going to do this very thing, I am thinking that I should have a no-load speed closer to 28-32MPH on the high end, and that will bring my low end gearing down where I need it, 10 MPH on the bottom end isn't really what I was looking for, so I will be buying another cog or 2 (hopefully used this time!) next I will try a 12T or 15T depending on what they have used.

***EDIT**** Well, looks like the smallest track cog nominally I can buy is probably 13T, so that's not going to work especially if I volt up, so I may indeed look at the possibility of going for a slower winding motor like an 8 x 8 if I stick with a hub motor, because I'd rather have more "low gearing" than high.

[John in CR]

Here's my LH 9C mid drive solution. Note that once I test run and I'm happy with the gearing, if I think I need any more rear brake than regen, then I'll use longer bolts and spacers and put my 203mm disk on. That rear 44t is 183mm, so I may be able to squeeze my caliper. If not, I'll just go down a size. My front is a 28t giving me effectively a 13.5" wheel for the hubmotor with the 3"x20 Kendas (21.25" OD) I'm running on the bike. I'm gearing it so low because it's getting a high voltage controller with 148V fresh off the charger, so I should get billy goat climbing with a 9x7 in a 13.5" wheel and plenty of current, and a top speed of about 45mph.

I'm using chainring size sprockets so I can run bike chain without concern, because there's so much less force on the chain than something like a Cyclone that eats chains. Once I dial it all in, I'll probably go to a 218 chain, but this will do for now and gives me regen. Note that a 3rd hand is very helpful for clamping the sprockets to the cover and brake disk for accurately marking the holes and a caliper a must, at least for me.

The holes in the 9C cover are for centrifugal flow ventilation. I expect to push near 10kw into it, so it will need cooling, and turning over 1krpm the motor will be its own fan blowing right at the windings.

9C mid drive sprocket LH.JPG

(36.41 KiB) Downloaded 78 times

[spinningmagnets]

a "keyed shaft" is actually a great solution for a standard RH freewheel on a LH-sprocket mid-drive. An ENO freewheel could have the groove cut in it with a standard hardware store file. The square cross-section pin is called a key, and two of them would hold enough torque that you'd never come close to breaking them at the power levels you have mentioned.

[LI-ghtcycle]

Here's my LH 9C mid drive solution. Note that once I test run and I'm happy with the gearing, if I think I need any more rear brake than regen, then I'll use longer bolts and spacers and put my 203mm disk on. That rear 44t is 183mm, so I may be able to squeeze my caliper. If not, I'll just go down a size. My front is a 28t giving me effectively a 13.5" wheel for the hubmotor with the 3"x20 Kendas (21.25" OD) I'm running on the bike. I'm gearing it so low because it's getting a high voltage controller with 148V fresh off the charger, so I should get billy goat climbing with a 9x7 in a 13.5" wheel and plenty of current, and a top speed of about 45mph.

I'm using chainring size sprockets so I can run bike chain without concern, because there's so much less force on the chain than something like a Cyclone that eats chains. Once I dial it all in, I'll probably go to a 218 chain, but this will do for now and gives me regen. Note that a 3rd hand is very helpful for clamping the sprockets to the cover and brake disk for accurately marking the holes and a caliper a must, at least for me.

9C mid drive sprocket LH.JPG

Nice! Just curious, is the reason for using smaller wheels as much for climbing as it is acceleration? I'm going to have to re-evaluate my gearing if the combo I have now has any trouble climbling hills with a fully loaded bike, but otherwise I might just go with a slower winding to make up for my limited gearing choices. I could always have Staton make a custom 44T Nuvinci FW adapter sprocket too.

You know, on second thought, I think I have the gearing right after all! I forgot to figure in for voltage sag and minimum voltage, i.e. 3.4V per cell, x 12s = 40.8 V, and that puts my gearing right back on target! I do need to try this with a full load however, until then, this is just conjecture.

I'm liking your set up John, I will have to see how it goes for ya, I think that would be a great set-up for my licensed E-Bike!

[LI-ghtcycle]

a "keyed shaft" is actually a great solution for a standard RH freewheel on a LH-sprocket mid-drive. An ENO freewheel could have the groove cut in it with a standard hardware store file. The square cross-section pin is called a key, and two of them would hold enough torque that you'd never come close to breaking them at the power levels you have mentioned.

Yeah, that would be a solution for sure, but I still think having my hub machined to use the same standard FW right-hand thread and LH threaded locking ring (slightly smaller diameter so that it is on the same shaft).



http://www.sheldonbrown.com/gloss_tp-z.html#track

In fact, now that I think about it, it probably wouldn't be that hard to find a trashed track hub that still has good threads on it, and have some form of machining done on my hub motor cover so that it could be press-fit onto it!

That would be a ton easier than having him turn the threads onto my hub cover, and I could get a steel hub (I hope!) so that I would have stronger threads!

[John in CR]

Nice! Just curious, is the reason for using smaller wheels as much for climbing as it is acceleration?

Neither. I can gear to whatever I want. My reasons for the smaller wheel on this DH bike are:
1. Space- It frees up enough space in the original swingarm to mount an RC drive, and that's 3" less length I had to add to my DIY swingarm.
2. Lower the bike- With the original 26" wheels the darn thing was so high, I had to stand on one pedal for a rolling start and swing my leg over to mount the bike. That may be okay at the house, but big me with another 30lbs of groceries would be begging for something worthy of youtube fame. Plus what am I going to do at stop signs and red lights if I can't put my feet on the ground? Sure I could learn the balancing trick, but I deal with a lot of 20mph+ crosswinds. No, I want a custom cruiser and lower is more aero anyway.
3. More tire clearance - On the rear I can lower stuff even more as well as add more travel. On the front it gives me enough space to hang at least 1kwh under the down tube.
4. I could only find these tires in 20" and they give my SuperV a real super motard look. I have no need for stealth, because as long as I'm electric (no ICE > 49cc), have pedals, and less than 4 wheels, then legally I'm a bicycle, period, as it should be. Actually I'm in a better legal position that a bike, because bicycles are prohibited on a few highways, but I'm not because I can maintain the 40kph min speed.

[TylerDurden]

Well, now I understand probably the main reason that the stoke monkey is a LH drive. Since I am using the motor, or hub to turn the sprocket, instead of a chain turning the hub, the motor's torque is now un-threading the sproket!...
I got some heavy duty lock tight, but I'm not going to trust it unless it holds up to about as much force I can put on it by hand with a chain whip to take it apart, and even then, it's tenuous since I know that the hub motor will put out much more torque!

Have you considered running the motor in reverse and using the chain in a figure-8?

[LI-ghtcycle]

Well, now I understand probably the main reason that the stoke monkey is a LH drive. Since I am using the motor, or hub to turn the sprocket, instead of a chain turning the hub, the motor's torque is now un-threading the sproket!...
I got some heavy duty lock tight, but I'm not going to trust it unless it holds up to about as much force I can put on it by hand with a chain whip to take it apart, and even then, it's tenuous since I know that the hub motor will put out much more torque!

Have you considered running the motor in reverse and using the chain in a figure-8?

Thanks Tyler, I had not thought of that! I would think this would get tricky however with the chain line and keeping it from rubbing against it's self?

The lock tight seems to be holding for now, but in the near future I plan on either getting my hub turned for the LH threads of a track hub lock ring or to press on part of a track hub.

[Rassy]

LI-, what Tyler said is similar to what I did, except instead of making a figure 8, which might be tough to do, I added an idler above the motor. And instead of running the motor backwards I just flipped it over so the wires come out on the right side. Since the 9C I have was threaded on both sides, it was then ready for a freewheel or track cog.

In your case, you could actually put two idlers over your motor. Actually just above the freewheel, one fore and one aft, would work. The aft one would be to make the chain wrap around the motor sprocket and the fore one would allign the chain with the sprocket on your wheel. These idlers would not require much support since they would just be on the return side.

[LI-ghtcycle]

LI-, what Tyler said is similar to what I did, except instead of making a figure 8, which might be tough to do, I added an idler above the motor. And instead of running the motor backwards I just flipped it over so the wires come out on the right side. Since the 9C I have was threaded on both sides, it was then ready for a freewheel or track cog.

In your case, you could actually put two idlers over your motor. Actually just above the freewheel, one fore and one aft, would work. The aft one would be to make the chain wrap around the motor sprocket and the fore one would allign the chain with the sprocket on your wheel. These idlers would not require much support since they would just be on the return side.

Kewl, options are good, but I still think making my threads same as a track hub would be simpler.

[LI-ghtcycle]

Ok! Got my first real trip in today, and it started out like Gilligan's Island, and ended 3 hours later! (Ok, I DIDN'T get marooned on an island, but the wind nearly blew me back to Portland on the return trip!)

I took a bigger chance than I should have, and paid a bit for it, I mean I test road the bike Saturday, rode to church Sunday, and did I think to top off the battery?! .... no

So anyway, I got down the road a mile or two with about 2 hours before closing (City Bikes, my favorite destination on a Sunday Afternoon!) and although it was pretty windy, it was nice out, and I thought, since later in the week is supposed to be so wet, I should go today and look at what they have for front pannier racks.

What I DIDN'T realize at the time going North, was that the "little wind" didn't seem so bad because it was a south wind, and was pushing me along!

So, I normally try to not use more than 8-9 AH's of my 12 AH pack for longevity of the LiPo (maximum charge cycles) and I was starting a 40+ mile trip with 3 AH's already used!

So I thought, ok, no biggie, save the power for the hills, but then I got the E-Bike grin going and you know the rest!

One thing that was pretty sweet, was that "wasted" no-load speed going up to 38.7 MPH? Well, it came in QUITE handy going down Linn at 35+ and being able to actually have the motor help!

I have never before had a buss stop along this bombing run down the hill, and this time I was able to get right back up to speed thanks to that "wasted" gearing.

Good thing I was in a hurry and took the elevator since I wouldn't have stopped to check the fender I put on to help keep clothing out of the gap between the hub motor and my saddle, but it turns out it was a REALLY good thing that I decided to use a plastic one, because my back-pack was pushing it down enough to cause the plastic to have slot cut through it on the edge of the hub!

So I trimmed it and away I went!


Well, since I was in a hurry, I thought I would show this motorcycle that I could move too on the 20MPH alley leaving the elevator, and I pulled him and kept ahead of his !?!!?!?! silly self for 2 of the 3 blocks much to his surprise, and of course this wouldn't do, so he had to pass me to save face!

About another 1/2 mile and I trimmed some more, took a short run with no noise problem solved!

Then it started to rain! But it's ok, I remembered that I had a ski suit to wear (more of a shell, not heavily insulated) , and I figured that would be more than enough protection if it got serious, and fortunately for me, it was just a drizzle that never got serious, just enough to cool me down as I rode.

Being in a rush, I skipped the scenic route and rode on one of the busiest roads around 99E, so I didn't hear the tell tale sound of plastic being sawed again by the hub motor until about another mile or so, and at this point I just took the silly thing off.


I made it to City Bikes with about 19 miles on the clock, (had about 3 when I started, but I probably had at least 2 more the day before) and lucky for me, they had just about every front rack I had looked up on-line plus a few more!

Sadly, none of them fit the bill, too narrow, too flimsy, too whimpy to fit over my extra wide Big Dummie forks!

I was very pleasantly surprised at all the positive attention my bike got from the people at the shop, both workers and customers, everyone wanted to know everything about it! (I guess this shouldn't have surprised me too much since this is a shop primarily frequented by commuters, not "hipsters" or other bicycle purists) I am used to a slight attitude from most of the employees (I think it's just part of the "I'm tough, don't mess with me or try to tell me anything about bikes, cuz I've heard it all, and truthfully, many of them have) I seemed to have earned some respect.

SO .... I almost gave into the urge to buy some cheap used thing so I could ride with my back up straight, and then I realized that I could just put the fanny pack (this was what was actually touching down on the hub motor) on the rear rack, and being the blond that I am, I completely forgot this logical solution and headed to their second store in the hope there would be some rack at the "new stuff" store that would fit the bill.

The first time that the motor had worn through the fender, there was a nice polished edge to one side of the hub, and that was it since I was careful all the rest of the way to Portland, and it stayed that way.


I have to say I REALLY LIKE this set up!!

I rode it more at bicycle speeds (averaging about 15 MPH, and up to 28 going down hills on the bike path, just taking it easy using only the minimum power, about 3-4A) and I felt like Superman again, just like the first time I rode a E-Bike!

The gearing makes a ton of difference, however, after this trip, if I decide to stick with a hub motor, I would be better off with an 8 X 8, but that might change once I get my 6S Nano Techs in to allow me to run 14S, that might make all the difference. I would really like more grunt on the low end, and I wouldn't mind gearing that gave me more low than high, and I really don't need to go 40MPH down hill under power (waste of power on a long trip but wow it's fun! )

My "not so windy" day was actually 15MPH and gusting up to 25MPH! Now that I was returning, I was having to burn precious AH's just to go on the flat!

Going back along the river sure didn't help, no cover, and half the time I could only manage about 7 - 9 MPH while pulling 2 - 3 Amps and pedaling moderately.

I started to realize that now it was MY batteries (legs going out) that were at stake as well, so now those AH's became even more precious!

I have concluded that a truly aerodynamic windshield is a top priority, even if it does look a little silly, and I saw somewhere in a post someone bought something for $40 or so, and that will have a huge effect on efficiency regardless of the fact that this bike won't go over 20-25 MPH most of the time.

Well, once I got to the half-way point to Oregon City, I was pretty beat!

I was about to climb the first big hill (2 miles about 7 - 10%) and I had forgot to pack a sandwich, so I reached into my emergency stash and ate all 4 granola bars!

The first hill wasn't so bad heading south, until I crested the hill, then the wind hit me full force! I barely could make more than 6 MPH on that steep grade and wind.

I have concluded that I need to double my battery capacity, as it is, I was able to get to the real hill with just 1 AH to spare, and it took most of my last AH going up this 2 mile monster, so I mostly tickled the throttle the rest of the way so that I wouldn't be pedaling against the DD & Nuvinci resistance (you know, I don't notice it usually, but this tired, it felt like riding on wet sand! ) and I managed to hit the garage having used exactly 9.02 AH's!

I am too tired to remember how to calculate Watt Hours, so maybe someone can refresh my memory, here are the stats:

45V (average voltage, started at 48 and ended at 44V)

12A average amperage

9AH used

46 miles traveled

If I'm not mistaken (and my tired brain probably is) this comes to ***EDIT***9 watts/mile.

However, taking 1 hour going, 2 hours coming back (with 3-4 stops along the way both ways) I think the average speed must have been dropped to around 8 -10 MPH.

[LI-ghtcycle]

Wow, that was one long rambling post!

It did however lack one important bit that I wanted to share, the torque arm that I put on to beef up the ones from the exercise bike (it's easy to just think steel is strong however, the drop-outs are really quite thin) and if I had not thought of that, I almost certainly would have had problems with chain tension. If I look really close, even though I have good, even ideal chain tension, I can see just the slightest sag on the chain drive side.

I will be building a second torque arm for that side too and then it won't be able to sag. Ultimately, when I have a custom rack built to hold it, I will design it so that if it were to loosen, it gravity would tighten the chain. I might be able to use the drop-outs that have motorcycle style tensioning from my nephews pocket bike for this, would make chain tensioning a real snap!

[LI-ghtcycle]

I might get some pics tonight up of the new torque arm and the build thus far, but I did some more testing, wanted to see what kind of efficiency I would get out of a fully charged battery going up the hill, and WOW with it on full under-drive, I was able to climb 12% at 7 MPH using just 20A!!

This is huge since normally I would be maxing at around 30A and only going 2 -3 MPH faster! (remember, this is a "touring cargo bike", so it's more important to be able to go up hills with out pedaling than anything else).

The second torque arm isn't really a torque arm however, I made it a tad short, so it's just acting as a tensioner more than anything, it's notched instead of having full coverage around the bolt, it sits on top of it, but this is just temporary.

I have a lead on what could be a VERY nice Lincoln welder for cheap from a friend, and I might have that be the "pay" for my neighbor's welding services, and I think first we are going to use some of the frames I have laying around to make the rear rack and attach the ends of my nephew's old pocket bike swing-arm since they have motorcycle style adjustable drop-outs, and that will be the first "production" rack for this build meaning it might end up as a permanent usable rack rather than just a test bed prototype like I am using now.

[LI-ghtcycle]

Got the new gearing going, and this time the gear calc is spot on! I think before I had the wrong RPM for the motor skewing the calc.

Right now with the 13T drive sprocket and 27T Hub sprocket, I am able to shift the Nuvinci gear ratio down to the point of 7 MPH and up to 29 almost 30MPH, so it's perfect!

The only problem is with the smaller sprocket I have less clearance on the drop-outs of the test mount, but I have been busily trying to adapt a derailleur for the task, and it made a noisy mess, too much tension, and I finally realized I could use the 'bent riders trick and just used some small diameter ABS conduit for the chain to slide over (I might eventually have the chain go through a length of pipe on the final version) where it would have rubbed on the drive side, and just guarded a few places it might rub from time to time, and the chain is at an ideal not too tight or too loose tension even though I had to remove 2 links for the smaller cog!

I also got my Zzip Designs MTB fairing, and have been so tired, that I could barely get half of the tensioner experiments done, and the fairing has been sitting for almost 2 days now, hopefully I can have it installed today and pics to show!

Tomorrow is going to be very windy, so it will be a perfect time to test the fairing!

[LI-ghtcycle]

Ok, pics!

First, some of the torque arms & plastic chain sliders from ABS pipe:







I made this just today after nearly 2 days trying come up with a chain tensioner I liked.

The first was pretty promising, made from an old derailleur that I took apart, but even thought it did what I expected, it also had the chain much tighter than I would have liked, and made a horrible racket.

The final version was just pieces of 1/2" plastic conduit pipe cut in half lengthwise and zip-tied to the side of the drop-outs and the rack where the chain gets a little close. The drop-out on the drive side (first pic) is the only place that will be regularly contacted, but just barely, and it makes no noise as the chain is just the right tension, not to tight or loose.

Here is a link to the post for my Mid-Hub drive to see the latest pics of the bike:

http://endless-sphere.com/forums/viewtopic.php?f=3&t=25856

[amberwolf]

If you happen to find that the ABS wears quickly, try finding an old kitchen cutting board made of the white slippery type of plastic. It may be cast from teflon; I used pieces from one as chain guides on CrazyBike2's powerchair drive, and they worked wonders without catching the chain, and didnt' show any signs of wear when I eventually removed all taht and went to the hub drive back in October.

[LI-ghtcycle]

If you happen to find that the ABS wears quickly, try finding an old kitchen cutting board made of the white slippery type of plastic. It may be cast from teflon; I used pieces from one as chain guides on CrazyBike2's powerchair drive, and they worked wonders without catching the chain, and didnt' show any signs of wear when I eventually removed all taht and went to the hub drive back in October.

Great idea! I'll keep an eye out for some at the local goodwill, need to get a new fanny pack anyway. Hopefully the pipe won't show any wear to speak of.

I'm going to start cutting up old frames soon as I can and build a rack that allows the motor to be in a better position.

Really don't like having the high center of gravity, makes the bike far too tippy! Might get started on my front racks first if I can cobble something together until next week when my neighbor can do some more welding for me.

[neptronix]

Ahh yes.. maybe a smaller motor like a bafang or mxus geared hub would do better for weight balance. i think you can get them as light as 7lb. Half the weight, and you can bring it down closer to the wheel..

Of course they can't kick out the same amount of power tho :/

[John in CR]

Okay LI-ghtcycle, now it's time for the biggie now that you have the gearing dialed in. What kind of mileage are you getting with no pedaling? wh/mile on the flats at say 20mph. Did you run the motor before in-wheel for some directly comparable data?

[LI-ghtcycle]

Okay LI-ghtcycle, now it's time for the biggie now that you have the gearing dialed in. What kind of mileage are you getting with no pedaling? wh/mile on the flats at say 20mph. Did you run the motor before in-wheel for some directly comparable data?

Yep, I'll have to look back at my post in the efficiency post to get specifics, but honestly, I have to do some more riding to make sure the gearing is dialed in, yesterday I was so beat after trying to make a tensioner, that I only road across the street in the neighbors extended driveway back and forth, and with some wind skewing things.