Project Velobration: The Common Power Module

I really like what Silvocross did with that 50cc transmission. Offhand I think - the CPM could definitely (1) accommodate this in the space already allocated - all I'd need is one more through-frame hole to fit the system, and (2) could definitely benefit from this: the 4 gears would (in how I imagine it) be fitted between the electric motor and the input to the left side of the NuVinci. This would mean gearing (4 discrete gears) of electric drive through the NuVinci, and the infinitely variable gearing of human power.

I'll keep it in mind. 70mm between the main structural plates is more than I am currently planning for - but very close. We'll see if I have room for it. But the idea is certainly very intriguing.
 
ok, then you have 4 discrete gears for the motor and infinite gears for human power :( Does not really fit together :x Why not use an IVT with two motor instead, like the Prius and and GM-Volt/Ampera do? Then combine it on the output of Nuvinci. This way you have 2 independent transmissions, which both have infinite gears. You could still use regen with the motors, since the freewheel of NuVinci sits on its input.

If NuVinci fails, you can still use the motors
If the motors fail, you can still pedal
If the final drive chain fails, you can still push your bike home :mrgreen:
 
made a plan, the gear ratios will be quite challenging. Also the final drive is on the left :( that sucks, it must be on the right. Otherwise it's non-standard and no more "common" :x

The Prius Driving Simulator illustrates how it works: http://www.wind.sannet.ne.jp/m_matsu/prius/ThsSimu/index_i18n.html
The Engine would be the PowerMotor in our case, the Generator is the "Actuator Motor", a "Motor" that sits on the wheel is not needed, since we can push Generator-Power from the Generator/Actuator-Motor into the PowerMotor/Engine (this would not be possible with a gas engine, which can not be fed with electricity ;) thats why Prius has 3Motors total, BUT we only need 2 )
 

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As an ActuatorMotor/Generator we can use a Bafang SWXH converted-to-middrive (Converted after my HowTo: http://endless-sphere.com/forums/viewtopic.php?f=28&t=45245),
it comes with a Planetary Gear with 4:1 standard gear ratio. The built-in freewheel must be blocked to enable regen. As a PowerMotor we can use a Rotormax 100cc with chain/belt reduction to the SWXH shaft. The shell/Hub of the SWXH will get a sprocket on the 6-hole sprocket interface, which is driven by NuVinci on the left. It gets another sprocket on the right that drives the wheel. This changes my scheme that I just posted, so it is possible to use a common right side drive :p
 

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For the calcs, to see if this can fit:

For the torque:
The PowerMotor must have 5-times the torque of the generator. SWXH motor can produce 8Nm, so the PowerMotor must do 40Nm. Since the 100cc only does 15Nm, we need a 40Nm/15Nm=2.67 reduction gear to the SWXH shaft.

For the RPM: The SWXH rotor does 1500rpm max, the RotoMax does 8000rpm max. But it is load like hell at this RPM. The 100cc can be run at 4000rpm efficiently. But output is limited to 3kW then. It's really brain-frock to do the math for a PowerMotor->SWXH shaft reduction :x Miles, where are you :oops:

BTW: It could also be possible to use the first IVT scheme with a right side, there might be enough space between the Nuvinci freewheel to attach another sprocket to the hub shell :?
 

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Some awesome ideas being added here - thank you Crossbreak. Some of these might have to be considered for a "2.0" version.

At present, I want the CPM to be flexible enough to run different driver ratios. My bike will be using 20" wheels, while Steve wants to use 26". He'll need more reduction.

The primary reduction will be a belt, and will be tensioned by slotting the axle and mount bolt holes. I did some measuring today - I only need about 3mm of "slot" between a drive belt loose enough to remove and tight enough to be properly tensioned. If this design only needed to use one reduction ratio, I could keep the side penetration slots to a minimum. But I want this bike to work for multiple reductions:
4.00:1, via 80:20
5.00:1, via 80:16
5.00:1, via 100:20
6.25:1, via 100:16

It appears I can get away with very small slots (within 5mm) the first two ratios using a 500mm belt, and even include the 100:20 combination in this same envelope as long as I use a 565mm belt. But for the 6.25:1 ratio, I need to add more than in inch in the slot length, and use a much larger 615mm belt (the primary constraint here is to have six "teeth in mesh", which is related to the center-center difference of the pullies. See here: http://www.maxtorque.com/calctool/centertocenterstartx.asp).

Finding the best way to do this flexibly will be a challenge.
 
Can you plz post the now-load rpm of the motor? I need it to calc gear ratios. Plz also post input-, output-sprocket and chainwheel number of teeth :)

The primary reduction will be a belt, and will be tensioned by slotting the axle and mount bolt holes.
Click to expand...
Chain-wheel screws are best use for this method IMO. They have very small thread pitch and can induce high pressure, they will not loosen due vibration.
 
crossbreak said:
Can you plz post the now-load rpm of the motor? I need it to calc gear ratios. Plz also post input-, output-sprocket and chainwheel number of teeth :)
Click to expand...
I'm totally sold on the Astroflight family of motors. The CPM is being designed around the 3220, but that means it will accommodate the shorter 3215 and 3210 without a problem. For now let's say I'll be using the 5 turn 3220 (or 10 turn 3210 withthe same kv), with a kv of 135. At 50 volts peak (using Castle Creations HV-160 as controller), that's ~5200rpm.

Reduction will go as follows:
Stage 1: 20:80 via belt (1:4).
Stage 2: 16:34 via bicycle chain (1:2.125). 34 is a constraint here, I want the smallest commonly available chain ring that fits 110mm BCD. This gives me 1:8.5 reduction at the input to the NuVinci left side drive sprag clutch.
The 16t driver on the second stage is going to be a freewheel in the very short term, as a failsafe in case the sprag clutch seizes while in use. I can get more reduction by shrinking that freewheel to 15, 14 or 13 teeth (13t = 1:10.46 reduction at the NuVinci input).

The NuVinci output to the rear wheel is a chainring mounted to a 130bcd hole pattern. I want this as small as possible - 38t. If I use a 50t chainring at the rear, I'm getting a further reduction of 1:1.3, leading to a total motor drive reduction of between 1:11.2 for the 16t fw and 1:13.8 for 13t fw. This will put my performance very close to the 1:12.2 I'm currently running on the 20" wheel folding bike (as a design goal: Get the thing moving with performance characteristics I'm used to, then perhaps make changes from there. The folding bike has great torque and a top end speed of 33mph).

Once this thing is built and proven, I can easily swap that 16t freewheel out for 17t or 18, for higher top-end speed...


crossbreak said:
The primary reduction will be a belt, and will be tensioned by slotting the axle and mount bolt holes.
Click to expand...
Chain-wheel screws are best use for this method IMO. They have very small thread pitch and can induce high pressure, they will not loosen due vibration.
Click to expand...
Chainring bolts are huge, requiring large slots. I'll take your advice and plan on using bolts with extra fine pitch - but I'd prefer to keep the bolts in the 5-6mm range.
 
Quick update -
I'm thinking of using one of these (see pic below) to drive the freehub. The rear wheel will need a 30 - 54 tooth chainring in order for the rest of the bike's gear ratios to work out.
june+09+030.jpg
 
Hi Matt,

I picked up one of these Giant Stiletto with Staton Inc 18.75:1 reduction gearbox to a Robin Subaru EH035 brushcutter engine.
http://www.staton-inc.com/store/products/Honda_GX35_7_speed_shift_with_the_Engine_35_8_cc_Four_Cycle_GIANT_STILETTO_Chopper_Bicycle_Engine_Motor_kit-398-0.html

Your criteria of a mid-drive RC with reduction reminded me of this kit, as someone has fitted an RC motor in place of the petrol engine.

Staton make some nice looking kits, and I'm very impressed so far with this one, still needing some basic chain lube and cleanup TLC and brakes improvement before I'm happy test riding it after it's been sitting for a while with previous owner.

He's got some info here, and similar options with the improved design 16.07:1 reduction:
http://www.staton-inc.com/Chain%20Drive.shtml
http://www.staton-inc.com/store/products/16_07_to_1_reduction_Gearbox_with_9_16_18_Clutch_Drum-1008-27.html
 
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