Warren's 350 MAC mid-drive (finally) recumbent

[Warren]

Folks,

This group is an amazing resource. I have been reading this stuff for months.

I am an old cyclist. I love long rides by myself...20-100 miles...upright and recumbent. I'm thinking of a highracer with a 48 volt, 20 amp Ping pack. I will pedal all the time...want to average ~20 mph. I really want it quiet, and simple. It is very hilly here. So a Crystalyte 4XX on a bracket will replace the idler below the seat. One chainring...slide motor back to tighten front chain. From there back to a 11-34 cassette.

I want to run the motor for efficiency most of the time...80% of unloaded rpm. Looks like my only choices are the 408 or 4011. Anyone know which Stokemonkey and Hanebrink use? Pros and cons of either?

On the Crystalyte site they give specs for these motors. Can anyone explain why the 4011 on 48 volts only got a 75 kg rider on a MTB to 25km/h (201rpm) when the unloaded rpm is 320.9?

Thanks, Warren

[deVries]

I know the Stokemonkey guy with patented design in Portland Clever Cycles has a custom motor he designed & is custom made for him in China. Can't remember off-hand his website, but Google will find it. He has a lot of info posted on his website about the motor, design, etc.

Those 4x motors with high torque didn't seem enough for me... you need a 5x ...06 for torque hills/speed you want... but maybe geared right the 4x in Stokemonkey form would do it???

I defer to the experts here... Maxwell sells these at good prices in the for sale area.

A lot of people like the 9x brand motors... that may be a good choice too? Or, check-out that "mighty-might" in the for sale area too.

Best of Luck...

[Warren]

de Vries,

"Those 4x motors with high torque didn't seem enough for me."

It is more than enough for me, as a mid-drive. I am on the low power end of interest in electric bicycles. If I want more power, it will be an Empulse, or something like it.

Warren

[Rassy]

Hi Warren, welcome to the forum. I can't begin to relate what I've learned here.

However, you will get advice from some that don't relate to being happy with slower pleasure riding. In 8th gear my trike will only go about 21 MPH, but in 1st gear it will climb a 15 to 20% grade at 6 to 7 MPH with light pedaling and the motor running efficiently (i.e. not lugging and heating up).

I think any hub motor is a good choice for a mid drive, since many are designed to run at a low RPM, somewhere between 300 and 400 RPM at 48V I think. The downside of the motor I used is it's weight and outside diameter (had to shoehorn it into the space available), but otherwise it is perfect for the job.

One issue that I didn't get right until completing the conversion was the gearing between the crank and the motor. Initially I had 48T on the crank and I couldn't keep up with the motor at WOT, and since I like to pedal all the time I was running the motor below it's efficient speeds. My motor and crank are on the same chain and I ended up with 16T on the motor and 56T on the crank, which works out good for this motor and me.

Good luck with your build. I will enjoy watching it develop.

[Warren]

Rassy,

"In 8th gear my trike will only go about 21 MPH, but in 1st gear it will climb a 15 to 20% grade at 6 to 7 MPH with light pedaling and the motor running efficiently (i.e. not lugging and heating up)."

So with moderate/heavy pedaling you could hit 25 MPH? That is what I am shooting for with tailwind and/or slight downhill, to make up for the 6-7 MPH uphill.

"I think any hub motor is a good choice for a mid drive, since many are designed to run at a low RPM, somewhere between 300 and 400 RPM at 48V I think. "

Yes. But I would like to be able to use cheaper, standard bike parts. I have a 60 tooth chainring on one of my recumbents, but I'd rather stick to 53 max.

"The downside of the motor I used is it's weight and outside diameter"

Outside diameter is not much problem on the highracers...tons of space under the seat. Just don't want it so low as to require an idler to hold the chain above the front wheel....another reason to avoid an overly large chainring.

"motor at WOT"

Explain acronym please.

Thanks, Warren

[katou]

Wide Open Throttle.

From the builds I've seen here, just about any hubmotor will work well for the Stokemonkey style of drive train. To hit a particular MPH goal is difficult to say because the Stokemonkey setup allows for so much variability driving through the existing derailleur.

The only way would be to see what hubmotors people have used for such drivetrains, and ask them what their speeds are, using particular gear ratios. Pretty involved question.

Me, I just bought a 9c 2807 and I'm sure it will be more than necessary. Stokemonkey style is more about low-speed torque in general. If I need more push, I'll just up the voltage.

That build has stalled because the dude financing it just bought a house, and had his priorities rearranged for him. So, it will wait, I estimate Springtime maybe.

Katou

[Rassy]

So with moderate/heavy pedaling you could hit 25 MPH? That is what I am shooting for with tailwind and/or slight downhill, to make up for the 6-7 MPH uphill.

Your question is good, but dialing your bike in for yourself will depend on too many factors for me to even guess. In your first post you called yourself an "old" cyclist. I am old, 70, but was never a "cyclist", so you probably are happy spinning faster than I am. My IGH (Nexus Internally Geared Hub) has an 18T cog and that could be replaced with a 16T cog to give 2 or 3 more MPH, with a proportional speed increase in lower gears, but a little less torque.

When I reach the top of my comfortable cadence I shift up a gear or two, and if already in 8th gear I just release the throttle and continue to pedal or coast. Where I ride there are lots of hills with varying grades and winds so I end up with lots of gear changes. The nice thing about this type of setup (compared to conventional hub motors), when my cadence feels right I know the motor is also in it's efficient zone.

[Warren]

Rassy,

"you probably are happy spinning faster than I am."

My preferred cadence is 75-85.

"The nice thing about this type of setup (compared to conventional hub motors), when my cadence feels right I know the motor is also in it's efficient zone."

Most Crystalyte hub motors spin 360-460 on 48 volts, no load. Even 60T-16T wouldn't get me down to my cadence. What is the no load rpm of your 9 Continents 6x10 motor? Are these still made?

Thanks, Warren

[Rassy]

Warren,

I think the unloaded speed of the 6X10 is around 300 RPM. According to Sheldon Brown's calculator for the Nexus in a 20" wheel my cadence should be 70 RPM at 21 MPH (with 18T on the Nexus and 56T at the crank). At 70 RPM at the crank with 56T the motor would be turning 245 RPM with 16T, or about 80% of unloaded speed.

Likewise, in low gear the calculator indicates 7 MPH at a cadence of 70 RPM.

These speeds are consistent with my maximum actual speeds on level ground and maximum comfortable cadence. I'm not sure the actual tire size used in the calculator is identical to mine. Also, my total weight is about 300# with me on the trike, which is going to drag the loaded speed down when compared to a 2 wheel bike with a lighter rider. I guess my normal cadence is 60 to 70 RPM.

I think this motor is still being made, but I'm not sure any reseller's in the US or Canada are stocking them. I would check with the E-BikeKit guys. They have active threads in the for sale section of the forum.

Doesn't your bike have 26" wheels?

[jbond]

Still looking for the simplest possible design for a mid motor recumbent. Especially one where the basic recumbent design has a mid-mounted idler. One possible solution to this is a small Bafang rear hub motor with two sprockets on it. One sprocket would be a fixed wheel for the chain back to the rear mech. The other sprocket would be a single speed freewheel for the chain to the front chainset. Then add a derailleur mech to take up the front chain slack. The theory goes that the front chainset can be a normal 2 speed road race set with a >50t.
- Pedal only. Chainset drives the hub, hub drives the rear, internal freewheel on the motor separates motor from hub.
- Motor only. Hub drives the rear, pedals freewheel on the single speed freewheel gear
- Freewheel. Both hub and pedals freewheel on the rear gearset
With a 16t or so pair of gears on the hub and a 14t smallest on the rear, you could run nice large chain runs for quietness and efficiency. You'd get some extra speed from the hub and still have a 2:1 or higher gear range on the rear gearset for climbing. The QWSXH Bafang hub should be easily capable of 25mph and with the gearing will still be able to power up the hills.

I *think* all the freewheels will line up in the right way. If they don't, Frank in Germany has a reversed planetary gear freewheel for these motors. Getting two single speed sprockets on the Shimano thread on the motor may be a problem. And keeping them on there with all the various torque reversals may also be a problem, but this feels solvable.

[Warren]

jbond,

"One possible solution to this is a small Bafang rear hub motor"

Yes. A geared hub motor gets you less weight, and the motor freewheels when you go pedal only...many of the advantages of an Ecospeed style mid-drive, without all of the extra chains and brackets. On the downside, you still get extra noise from the planetary gear set, and less gearing flexibility than the external reduction rigs.

The problem is that you want a hub motor wound for running 20 mph on 48 volts, in a 26" or 700c wheel. Used for a mid-drive, this gets your cadence in the normal range, with normal bicycle sprockets, and chainrings. Unfortunately, all the geared hub motors I am aware of are wound for 36 volts at 20 mph.

On the other hand, If I ran a geared hub motor on 36 volts, the lighter weight would offset the extra weight of a 36 volt, 30 amp Ping pack! Same total weight, more range....but both the hub motor and the battery pack would be more expensive.

Nothing is ever simple. Warren

[jbond]

I picked up this info which might help for the small Bafang motors. All at 36v (I think).

The gearbox is on SWXK or SWXH or SWXB always the same the different speed comes from copper windings inside the motor and in this way the realise different rpm for different wheelsize. 175rpm is for 28",195rpm is for 26", 220rpm is for 24",255rpm is for 20", 275rpm is for 18" and around 320 is for 16"

I think a "16inch" motor in a 700c rim running at 36v should have a high enough no-load rpm as a hubmotor to do 25mph. By using a slightly larger sprocket on the hub than the smallest on the rear cassette, you can get a bit more speed if it isn't. I think this is the point, by mid mounting a hub motor you get more flexibility because you can change the rear cassette and the sprocket on the motor to get your gearing right. And by having the same size sprocket for both chains, you still keep the pedal chainset to rear cassette the same. I'm told the nominally 250W motors are safe to push to 15A-36V which is over 500W. That should be enough in a 'bent to reach 25mph on the flat. That matches nicely with a 36V-15AHr Ping

The drag from these Bafangs when freewheeling is minimal and silent and they're really not that noisy when running.

[Samba]

Could use a sram dualdrive for more gearing range - to accomidate a motor rpm thats higher than ideal or an unknown in the loaded vs unloaded rpm. But that doesn't help matching the crank cadence to the motor.

My wishlist has a nuvinci hub on the rear, to the motor, to a 5 or 7 speed hub configured as a gearbox, to the crank. I like to vary the cadence a lot and the foot position/angle for theraputic reasons.

[katou]

Don't forget the reduction from the motor to the left side tandem/stoker chainring.

First stage: motor to left side Bottom Bracket cog
Second Stage: right side cog to rear cluster

Maybe you're already including this in your calculations, but you could go with a low toothcount on the motor, big ring on the bottom bracket left side, maybe get 4:1 reduction right there.

Anyway, that's what I'm planning. I'm going to use the existing cluster on the 9c to give me a bunch of cogs to try out different first stage ratios, run it with an idler to take up extra chain slack until I get the right ratio, then break the chain to remove extra length and ditch the idler.

Katou

[jbond]

First stage: motor to left side Bottom Bracket cog
Second Stage: right side cog to rear cluster

Where are the freewheels in this config? Does that mean the pedals have to move under motor power?

[deVries]

The problem is that you want a hub motor wound for running 20 mph on 48 volts, in a 26" or 700c wheel. Used for a mid-drive, this gets your cadence in the normal range, with normal bicycle sprockets, and chainrings. Unfortunately, all the geared hub motors I am aware of are wound for 36 volts at 20 mph.

On the other hand, If I ran a geared hub motor on 36 volts, the lighter weight would offset the extra weight of a 36 volt, 30 amp Ping pack! Same total weight, more range....but both the hub motor and the battery pack would be more expensive.

I know some of the Cute & Fusin geared motors are slower rpm at higher volts. Also, cell_man had/has or can get a slower wind DD below a No load speed of 280rpm at 39.2V upon special order. He has good prices & can sell the bare motor. These geared or DD motors are low-cost, and many of these geared motors are very, very, quiet too. So, I'm thinking cost or loudness should not be an issue with geared motors.

[Warren]

deVries,

"DD below a No load speed of 280rpm at 39.2V upon special order"

The 48 volt speed would still be a little high.

"cell_man...good prices & can sell the bare motor."

He sounds like a good source. I will check with him.

Thanks

[Warren]

jbond,

"Where are the freewheels in this config? Does that mean the pedals have to move under motor power?"

Yes. But the motor is stationary when pedaling with the power off. This system is designed for bicyclists. It should be bullet-proof. The only inefficiency introduced is that you are gearing the motor down to the cranks, only to have it geared back up from the cranks to the rear wheel. Using the motor as a mid-drive eliminates the double gearing. I imagine the battery pack mounted under the seat of the recumbent on the left side, and the DD hub motor mounted under the seat on the right side, a 16-18 ENO freewheel facing in.

http://www.whiteind.com/images/640_dos1618.jpg

Now if someone would make a hub motor with a left hand threaded, backwards running double freewheel, I could mount the motor on the centerline, under the seat.

Warren

[John in CR]

Warren,

That last config will leave you with the motor force to unscrew the freewheel. I've bonded one on with epoxy that's held up well, but that was only standing up to minor pedal input.

A geared hub with chains on the right with a non-freewheeling cog on the cover driving the rear, and a normal freewheel at the motor receiving the pedal input solves all of the freewheeling issues in the easiest manner, though you are left with the gear hub issues.

With a direct drive motor, I think the easiest without getting into special components, that are either expensive or suspect in quality, is to send the motor and pedal to a combining jackshaft. That's the route I plan, though it is for a high power, high speed rig that can also climb steep mountains, because I feel that I'll need that extra stage anyway for the gearing range I want on the pedals.

One concern I have with Katou's approach is the strength of that freewheel connection. We've heard of quite a few failures there with pedal input, so it's gotta be a weak link for motor input. I'd definitely pop that motor cover off and reinforce that area.

John

[katou]

I agree, the freewheel part of the Stokemonkey is the only part that I have real reservations about.

I will deal with it when I have to, but I will have my eye on it....

The efficiency lost inherent in gearing down in order to gear back up is frustrating, at the very least to my sense of mechanical esthetics.

That said, I have never seen any numbers indicating how much juice was lost to chain/cog friction driving through the existing chain.

The Stokemonkey system shines when you need low-speed, climb anything, stump-pulling torque.

When I get mine setup, I want to put it in the lowest gear available, and then go looking for the steepest hills I can find.

1 mph, 1000 ft*lbs anyone? Hey, it's good to have dreams.

Katou

[Warren]

John,

"That last config will leave you with the motor force to unscrew the freewheel."

The custom I described, with left hand thread, would tend to screw onto the motor under motor power. Under pedal only, it would freewheel, so no tendency to unscrew. Actually, you could use the normal Eno dual sprocket freewheel, just flipped around on a normal hub motor...if you could tap into the motor side cover between the freewheel threads, and the motor bearing. I am imagining a cap with three or more screws, to prevent the freewheel from spinning off.

"One concern I have with Katou's approach is the strength of that freewheel connection. We've heard of quite a few failures there with pedal input, so it's gotta be a weak link for motor input."

I suspect that jumping on the pedals every 180 degrees is harder on it than a steady motor pull. Also, the double freewheel is much closer to the cover than the outer cogs of a 7 speed freewheel...much less leverage.

Warren

[John in CR]

Sorry, I wasn't paying attention and missed the LH threads somehow.

I do think you give the motor makers too much credit. All of the hubbies I've seen have thinner cast AL material at the connection for the freewheel than on the alloy bike hubs I've cannibalized to add a FW connection. I'd much rather spend a short time addressing a known weakness before the motor goes on than repair a failure. Maybe it is strong enough, but from some of the failures I've heard, they didn't sound abused like a pedal bike might be.

[Warren]

John,

"I'd much rather spend a short time addressing a known weakness before the motor goes on than repair a failure."

I've never had my hands on one to take apart. How would you go about reinforcing the cover?

Warren

[docnjoj]

Crystalyte motors now use a reinforced (with steel) central hub area to the threaded connections for freewheels. Check with ebikes.ca
otherDoc

[Warren]

"Crystalyte motors now use a reinforced (with steel) central hub area to the threaded connections for freewheels."

Great! Sounds like my problem is solved. Thank you otherDoc.

Warren