Give cargobike non-hub motor 3 speeds, ideas?

[spinningmagnets]

John-in-CR used a hubmotor as a non-hub and I want to do the same for a longtail cargobike (plenty of room in the frame for any chosen options). http://endless-sphere.com/forums/viewtopic.php?f=6&t=26932&start=15#p389622. 44V LiPo, Probably only 1,000W.

The smaller Crystalyte 406 hub motors don't seem to be available, so I plan to order a cell_man MAC geared hub, which is about the same size as the 406 ( http://www.emissions-free.com/catalog/i1.html ). I've been pondering ways to incorporate 3-speeds for the motor by using a Nexus Internally-Geared-Hub (IGH). I can key a freewheel to the MAC threads so it can be reversed if needed, or, I may attach a sprocket to the disc-brake flange on the left.

I plan to use it as a 2-speed in daily operation, with first gear reserved for especially steep hills. I will pedal some, but it will be more of a moped commuter. Any ideas or warnings welcome. I'd also appreciate parts links that could make any of these options more doable. I can make any custom sprocket mount adapters that will be needed.

A. Left-Side-Drive Using the IGH as a de-spoked transmission/jackshaft, possibly use a belt connecting the motor to the IGH (primary-drive). Nexus-3 is available in a trike hub, which already has a second sprocket attached to the shell (can be used as a sprocket, or, used as a mount for a belted pulley)

Pros: adding a 2:1 drive between the motor and IGH cuts the torque applied to the IGH in half, making the weaker Sturmey-Archer IGH a viable option. Complete separation of stock pedaling system. I think that with the IGH flipped over, the freewheel is turning in the correct direction while using its stock configuration. This means I may be able to easily connect the motor to the IGH body with a solid cog bolted to the Hubs disc-brake flange (whether I use a chain in the primary drive, or the cog is merely a mount for a belted pulley).

Cons:

B. Series-Drive (like the Hanebrink http://elescooterparts.com/J/6.jpg ).

Pros: I have a GGoodrum double-freewheel adapter, and this would be the easiest to put together. If motor is mounted on a rear suspension arm, no motor-chain tensioner is needed (pedal chain tensioner for chain-stretch less of a problem)

Cons: It may require throttle snubbing to prevent shock-loading the IGH teeth and breaking them.

C. Parallel-Drive (like GGoodrums bike http://endless-sphere.com/forums/viewtopic.php?f=28&t=12267 )

Pros:

Cons: May be too wide to fit on some frames drop-outs with double freewheel? Limits pedals to 3-speeds (not actually a problem for me). May require snubbing the throttle to prevent IGH tooth breakage.

 

[spinningmagnets]

I got the $20 dual-freewheel adapter from ES member GGoodrum (needed for configurations B and C), but the TPpacks RC-helicopter site he sells them from is down right now ( http://www.tppacks.com/ )

Heres a $150 example of the Nexus-3 trike hub (has two sprockets, one of them freewheels, and one of them is fixed onto the shell) including the shifter (for configuration A):
http://www.choppersus.com/store/product/771/Trike-3-Speed-Drive-Train-Kit/

$119 Nexus inter-3 with disc-brake flange (one option for mounting a fixed sprocket/pulley to back-drive the IGH-shell is to attach them to a disc-brake flange, configuration A)
http://www.niagaracycle.com/product_info.php?products_id=503222

 

[Miles]

I got the $20 dual-freewheel adapter from ES member GGoodrum (needed for configurations B and C), but the TPpacks RC-helicopter site he sells them from is down right now ( http://www.tppacks.com/ )

Spinning, It's not exactly a dual-freewheel adaptor. It will get you a fixed sprocket for the motor and a freewheel for the pedal drive. I expect you know that, though...

 

[spinningmagnets]

Thanks, Miles. I forgot that some of the newer readers from this last year may not have seen many of the older builds, and wouldn't be familiar with them.

In configuration C, there must be some type of freewheel added to either the Bottom-Bracket (BB, the pedal-axle) or to the motor shaft. If I didn't, I would be driving the unpowered motor when just pedaling.

a 3-speed hub used as a jackshaft discussion over at a gasoline bicycle website
http://motorbicycling.com/f48/will-sturmey-archer-3-speed-hub-10131.html

 

[Rassy]

SM, nice to see you putting a multi-speed mid-drive together. I don't have any specific advice, but I'm sure you will like it when finished.

Just yesterday I hooked one of my old trailers to my trike for a little battery test (don't ask). Anyway the trailer has a WE BD36 in a 16" wheel and a 48V 15AH Ping battery. It will push the trike at about 20 MPH on the level, but with all the weight on the trike (mid-drive setup, batteries, 210# of me, etc.), it stalled out on my 20% grade driveway and I had to get off and push the last 20 feet. This power trailer was able to push the trike up the driveway before all the extra weight was added for the mid-drive, but it did get warm, and was obviously getting close to it's limit.

The mid-drive on the trike also tops out just over 20 MPH on the level, but in low gear it walks right up that same driveway at 5+ MPH, even when pulling a BOB trailer with some groceries in it.

One incidental point, I have replaced the freewheel on the mid-drive motor with a track hub. So now when I pedal without running the motor, I am still spinning the motor. It's working out fine, and I don't really notice the extra drag. Rode about 70 miles last week end with a friend on a pedal only trike, so fairly slow riding. Used about 900 WH for the 70 miles.

Good luck with your build.

 

[amberwolf]

Or, if you want to keep the rear wheel standard (so you can just swap it out with any other rear wheel, if anything is damaged on it, and not worry about special spoke sizes because of the IGH), you could do it by using the IGH as the jackshaft that combines both pedals and motor, rather like your C version, but prior to the wheel.

I started to make a drawing for it, but I dozed off and screwed it up and I'm so sleepy I'll ahve to wait till tomorrow or something to make a new one.

But this is more and more likley similar to how I will do it for my new bike.

 

[spinningmagnets]

Thanks for the responses. I've been thinking about this for a long time. I credit Granpa-Chas over at the VisforVoltage site several years ago. His grocery-getter is a delta trike using a brushed 24V TNC motor at 36V, which drove a mid-mount 3-speed IGH, and the system was geared for 20-MPH top speed. 1st and 2nd gear were very good climbers. Miles, your input during several 2-speed threads verified the value of the geared possibilities.

His justification for the brushed motor (rather than the preferred brushless) was how cheap the controller was. Even with the old-skool brushed motor and SLA batteries, the 3-speed helped its climbing and kept the system from overheating even when loaded on a steep climb (hilly San Francisco bay area).

The standard gears on most 3-speed IGHs are a 30% under-drive for first, 2nd is locked at 1:1, and 3rd is a 30% over-drive. If 3rd is 20-MPH loaded on level ground, 2nd would be around 14-MPH, and 1st should be near 9-MPH. If 36V X ~20A = 750W/one-HP, and its geared for only 9-MPH, I don't think he was exaggerating. I expect good performance from ~46V X 25A = 1100W/1.5-HP. I will load-test it gradually, and add active cooling if I can't keep my hand on the motor/controller, if they get too hot (I also have lots of hills here).

cell_man's geared-motor planets are noted to be wider and of a more robust material, so they can take more heat than perhaps the Bafangs? but that also means the motor can get very hot without the cheap-to-replace gears failing as a mechanical fuse, so, I intend to install a temp probe before peak-load testing.

Rassy, I seem to remember your mid-drive was a clever freewheel solution that will be useful to others, and at the same time the gear-ratio between the mid-drive hub and rear wheel was near 1:1, so, I thought you would have gotten near the same performance from having the hub in the rear wheel. At the time I felt it was a missed opportunity where you could've gotten a faster winding and used higher volts, because the sprocket ratios could be easily adjusted to have the same speed, but with even more climbing torque.

After some thought, your build was part of an inspiration for me as I realized that, if I added a 3-speed to a non-hub, it would have 30% better climbing and 30% less heat in the first gear of a 3-sp IGH, if I had a 1:1 ratio for the entire system between the motor and the wheel while in second gear. Plus on level ground, I would have 30% better speed in third. I can also easily swap a single sprocket to change the overall system gearing so that second gear is 20-MPH.

Or, if third gear is 20-MPH, first gear (9-MPH) should be somewhere near 60% better climbing-torque/less-heat?

Miles and AW, both of your postings over the last couple years have been incredibly useful for me, and I value any input you may have. I think this will be a fun project!