Crankin' It - Mid-Mounted Crank Drive

450w (24V) Gear Reduction Motors (Brush) - thin profile
25.9V = 485w
29.6V = 555w
33.3V = 625w ... partial throttle at low speed recommended to be more efficient and to reduce damaging heat
37V = 695w ... reduced amperage controller (or throttle restraint) recommended to reduce low speed heat damage
44.4V = 835w ... reduced amperage controller (or throttle restraint) recommended to reduce heat damage
48.1V = 900w ... reduced amperage controller (or throttle restraint) recommended to reduce heat damage and prevent shearing the sprocket key

XYD-16
- Confirm with seller! White label States XYD-16 and "C" on cover


Monsterscooterparts.com

Eledtricscooterparts.com - 7th item down

Thesuperkids.com

MY1018
Triangle on Cover
Monsterscooterparts.com

TNCscooters.com
 
Single Chainring Advantages - Disadvantages

Advantages
Eliminates the twisting (off-center) stress-wear on the crank freewheel = greatly increased reliability-usable life
Reduced cost! "Standard" crank freewheel with single centered chainring will survive longer or as long as super duty freewheel with multiple chainrings

Disadvantages
Negates the possibility of shifting between multiple front chainrings
Eliminates the variance of chainring sizes to match motor to pedal speed.
Doesn't look as complex = doesn't impress the simple minded as easily

Perhaps not obvious ... It is still possible to modify motor and pedal speeds

Motor speed can be varied either by:

Changing the size of the motor sprocket

The Currie motors, MY1018 & XYD-16, have 8T,9T,11T,13T available (mod-able 15T also found)
Adapter is available for 13T-14T-15T small freewheels
Additional adapter is available for the "standard" 16T - 22T freewheels

Changing the voltage of the motor
At 24V, gear reduced (sprocket) speed is ~400 rpm
22.2V = 370 rpm
24V = 400 rpm
25.9V = 432 rpm
30V = 500 rpm
33.3V = 555 rpm
37V = 617 rpm
40.7V = 678 rpm
44.4V = 740 rpm
48.1V = 800 rpm

Then ... rear sprocket can be adjusted
14-34T to 11-28T to 21-26T 7-speed freewheels (or cassettes) available

Front Chainring
Now you adjust your pedal ratio by changing the single chainring ... 32T - 62T+.
This has no effect on the motor speed ratio! ...

Motor speed is now determined by motor sprocket to rear wheel sprockets ... not by chain ring.
Chainring is effectively an idler sprocket for the motor contribution, varying the size has no relation to motor speed.

I do not see any reason to use dual chainrings of equal size ... ?
I have 2 - dual 40T and 1 - single 40T.
Advantage of chain contacting 20T rather than 10T?
I can't justify that as any reasonable advantage ...

So, I will likely post up, at least, 2 40T chainrings with "standard" 5 hole - for ACS CrossFire etc. - Appear new - steel.
Or swap for compatible 44T 48T ... other?
 
Last edited:
Chainring selection

24T does not offer the recommended "offset"
24t.jpg

30T
30t.jpg

36T
36T.jpg

44T
44T.jpg

48T
48t.jpg



24T, 30T, 36T, 44T, 48T - sickbikeparts.com

I'm surprised at the lack of a 40T chainring, 36 to 44T is a pretty drastic jump, limiting fine tuning motor to pedal speed.

It should be reasonably simple to build an adapter from the common 5 hole freewheel to the 130 or 144 BCD chainrings.
The adapter would supply the desired offset to any flat chainring.
This would enable a large selection of readily available chainrings ... up to 62T+?
Larger chainrings might create increased "twisting" wear on dual chainring setups but single setups should suffer no additional stress.
 
I'm surprised at the lack of a 40T chainring,

I agree.

Using the SickBikeParts optional low range jackshaft gearing 9T - 48T, you really need a 40T chainring to bring the gear ratio back where it needs to be. The 36T isn't really suitable in that situation, hence i have to purchase another jackshaft freewheel bearing system from another manufacturer which happens to have a 38T chainwheel, just so i can get the 38T sprocket.
 
Bargain I couldn't pass up!
A Schwinn Front Freewheel (FF) crankset

file.php


Circa ... late 70's, this item was touted as "a solution ... in such of a problem!"

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Interesting to me, the freewheel seems to possibly run, at least partially, against the BB bearing race.
Dependent on actual construction, this could bypass some of the problems with modern freewheel chainring crank systems.

file.php


Just had to get it, cost less than $25 including shipping.
I will post up evaluation after arrival.

Update:
Better picture shows freewheel bearings to be easy to keep lubricated and adjustable.
Durability looks to be a big improvement over "modern" methods!

file.php
 
That Schwinn Front Freewheel (FF) crankset is a nice looking unit, and appears to be a full compliment bearing housing.

The SickBikeParts higher end Heavy Duty freewheel bearing system (made by White Industries) is the best component i've used, when compared to the standard duty freewheel bearing versions which in my opinion (and going from personal testing of two different manufacturers) is not a particularly durable bearing system in operation, despite the fact that by design, it should be a better system than the White Industries freewheel. Ironically, the White Industries freewheel (even though it uses a single bearing) can take a heck of a lot more punishment and maintain significantly better sprocket stability than the cheaper dual bearing design.

From what i understand White Industries is going to release a "dual bearing system" for their heavy duty freewheel, which should make it an even more effective sprocket drive system. Unfortunately we might have to up to 2 years before the dual bearing design is released.
 
Hot Damn!
Schwinn freewheel crank arrived.
A 37 year old item in excellent condition! (1977)
No noticeable wear on the chromed teeth and no traces of rust near the bearings.
Freewheel is nice and tight and smooth ... best of all it is adjustable.
It can be tightened up after it wears a bit.

I do believe that a single chainring is preferable.
But this looks to have good potential as a double ... if I ever go that way.

Now just gotta find the "proper" bike to transform.
My Schwinn Searcher 700C, (rescue bike), looks to be the prime candidate.
14-34T 7speed looks appropriate for the 52T chainring @ 33.3V.
Steel frame gives good motor mount options.

Will probably build a cheap Mountain bike conversion with cheapo single chainring as my first testbed ... tho.
 
Just found a 46T Schwinn-Shimano FF 46T Single freewheel crank.
Perfect for my pedal assist at my preferred 33.3V.

Newest addition seems advantageous over the dual chainring. Chainring is perfectly centered between the freewheel bearings, eliminating the "twisting" that destroys the dual chainring variant.

There is a speckling of rust on the chrome, but teeth and bearings appear to be in excellent condition.
(1978 vintage)

file.php



file.php
 
Single Chainring Advantages - Disadvantages

Advantages
Eliminates the twisting (off-center) stress-wear on the crank freewheel = greatly increased reliability-usable life
Reduced cost! "Standard" crank freewheel with single centered chainring will survive longer or as long as super duty freewheel with multiple chainrings

Disadvantages
Negates the possibility of shifting between multiple front chainrings
Eliminates the variance of chainring sizes to match motor to pedal speed.
Doesn't look as complex = doesn't impress the simple minded as easily

Perhaps not obvious ... It is still possible to modify motor and pedal speeds

Motor speed can be varied either by:

Changing the size of the motor sprocket

The Currie motors, MY1018 & XYD-16, have 8T,9T,11T,13T available (mod-able 15T also found)
Adapter is available for 13T-14T-15T small freewheels
Additional adapter is available for the "standard" 16T - 22T freewheels

Changing the voltage of the motor
At 24V, gear reduced (sprocket) speed is ~400 rpm
22.2V = 370 rpm
24V = 400 rpm
25.9V = 432 rpm
30V = 500 rpm
33.3V = 555 rpm
37V = 617 rpm
40.7V = 678 rpm
44.4V = 740 rpm
48.1V = 800 rpm

Then ... rear sprocket can be adjusted
14-34T to 11-28T to 21-26T 7-speed freewheels (or cassettes) available

Front Chainring
Now you adjust your pedal ratio by changing the single chainring ... 32T - 62T+.
This has no effect on the motor speed ratio! ...

Motor speed is now determined by motor sprocket to rear wheel sprockets ... not by chain ring.
Chainring is effectively an idler sprocket for the motor contribution, varying the size has no relation to motor speed.

I do not see any reason to use dual chainrings of equal size ... ?
I have 2 - dual 40T and 1 - single 40T.
Advantage of chain contacting 20T rather than 10T?
I can't justify that as any reasonable advantage ...

So, I will likely post up, at least, 2 40T chainrings with "standard" 5 hole - for ACS CrossFire etc. - Appear new - steel.
Or swap for compatible 44T 48T ... other?
Single Chainring Advantages - Disadvantages

Advantages
Eliminates the twisting (off-center) stress-wear on the crank freewheel = greatly increased reliability-usable life
Reduced cost! "Standard" crank freewheel with single centered chainring will survive longer or as long as super duty freewheel with multiple chainrings

Disadvantages
Negates the possibility of shifting between multiple front chainrings
Eliminates the variance of chainring sizes to match motor to pedal speed.
Doesn't look as complex = doesn't impress the simple minded as easily

Perhaps not obvious ... It is still possible to modify motor and pedal speeds

Motor speed can be varied either by:

Changing the size of the motor sprocket

The Currie motors, MY1018 & XYD-16, have 8T,9T,11T,13T available (mod-able 15T also found)
Adapter is available for 13T-14T-15T small freewheels
Additional adapter is available for the "standard" 16T - 22T freewheels

Changing the voltage of the motor
At 24V, gear reduced (sprocket) speed is ~400 rpm
22.2V = 370 rpm
24V = 400 rpm
25.9V = 432 rpm
30V = 500 rpm
33.3V = 555 rpm
37V = 617 rpm
40.7V = 678 rpm
44.4V = 740 rpm
48.1V = 800 rpm

Then ... rear sprocket can be adjusted
14-34T to 11-28T to 21-26T 7-speed freewheels (or cassettes) available

Front Chainring
Now you adjust your pedal ratio by changing the single chainring ... 32T - 62T+.
This has no effect on the motor speed ratio! ...

Motor speed is now determined by motor sprocket to rear wheel sprockets ... not by chain ring.
Chainring is effectively an idler sprocket for the motor contribution, varying the size has no relation to motor speed.

I do not see any reason to use dual chainrings of equal size ... ?
I have 2 - dual 40T and 1 - single 40T.
Advantage of chain contacting 20T rather than 10T?
I can't justify that as any reasonable advantage ...

So, I will likely post up, at least, 2 40T chainrings with "standard" 5 hole - for ACS CrossFire etc. - Appear new - steel.
Or swap for compatible 44T 48T ... other?


The voltage vs rpm thing is of great interest to me.

I have a 24v my1018 (which seems a very durable unit) powered bike with a dog of a lead acid battery, and a 12ah 36v ebike with nice panasonic bottle battery that needs upgrading to a 15ah lifepo4 pouch cell battery. It would be neat to use the panasonic 36v as a hand me down on the 24v bike.

Are you saying i can simply swap the 24v for a 36v and the 24v my1018 & controller will un-protestingly run at higher rpm & presumably with more zip? It seems counter intuitive that the motor and controller are happy with 50% more voltage.

My plan was to reduce the 36v panasonic battery output to 24v somehow. I have been assured this is simple.

Your advice would be appreciated.

fyi, my 24v bike is a longer silverfish type ladies bike with no gears, just a second dedicated chain to a second freewheel sprocket on rear axle.

It sounds crappy, but there are things to like. a/ the chain can be much stronger and durable than for derailleurs and b/ the pedals are not stuck with the same, probably unsuitable, ratio as the motor. I still don't have much luck finding a gear that suits both on my 36v 24 speed mid drive.
 
Many 2008 and earlier and some few 2009 eZips are 24-36V+ capable.
Test by jumpers from battery to pack terminals - insure pos and neg terminals to avoid damage!
$15 20-50V controller available -eBike Toolbox (requires connector adaptation)
 
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