Cyclone Cadence - gear up human speed?

[heathyoung]

Its probably been discussed here before (but not that I could find) - anyways.

I'm looking to build up a downhill bike with a cyclone setup, but the prevailing opinion on these is that the gears aren't the best in the 9:1 reduction drive. This could be resolved by increasing the voltage (and hence RPM) which would reduce the torque action killing the gearbox for the same power output with more reduction.

The cyclone @ 48V has a silly RPM output for trying to provide any assistance. The standard KV of 150, combined with a 9.33:1 reduction (770 rpm), and a 14:44 reduction result in a maximum RPM of 245 RPM at the chainring. (!!!)

Now, this can be reduced down with another reduction to a more sensible 80 rpm or so BUT the torque that is then placed on the chains and sprockets is much higher (most people complain about chain growth).

Left field suggestion - you can't pedal at 245 rpm (I don't care who you are) BUT what if you placed a chainring on the left hand side, and geared it UP? Get some sickbikeparts jackshaft parts - a shaft, two bearings with retainers, a 9 tooth sprocket, a freewheel adaptor and a 22 tooth freewheel. You would get 44:9 (4.88:1) then 22:44 (2:1) so in all, a 1:2.44 increase, so a cadence of 100 rpm would yeild 244 rpm.

Even more left field - left-hand chainwheel driving another motor (another cyclone?) Set up as a generator (ie. 3 phases brought out to a 3 phase rectifier) feeding into a 'simple switcher' set up as a charger. Assuming a maximum cadence of 100 rpm (80 typical) with a 44:14:9.33:1 = ~2900 rpm X 150Kv = ~20V - step that up to charge the batteries... Hmmm.... Beats pretending to pedal, and there is some actual input.

 

[amberwolf]

Get some sickbikeparts jackshaft parts - a shaft, two bearings with retainers, a 9 tooth sprocket, a freewheel adaptor and a 22 tooth freewheel. You would get 44:9 (4.88:1) then 22:44 (2:1) so in all, a 1:2.44 increase, so a cadence of 100 rpm would yeild 244 rpm.

This is kind of what I did with CrazyBike2's original powerchair motor drivetrain. Since it has two BBs on it, one for the actual cranks and one for the jackshaft/front of regular shiftable chainline, I put the crank chainring on the left side, with a smaller ring than it's receiver on the jackshaft (not by much, though I forget the ratios).

The powerchair motor already had a gearbox that output something like 120-150RPM, I think; I've forgotten now, might be that was it's 24V RPM and since I used them at 36V and higher, was a lot closer to what you will see out of that proposed gearing. It went from a smaller ring on the powerchair mootr gearbox output to a larger one on the jackshaft.

Only thing I didn't have was a freewheel on the pedal chain, so the pedals spun with the motor which had HUGE torque, and I tore up more than a couple pairs of pants getting tangled in the pedal chain. Could've probably broken a leg once, if I hadn't been able to stop.


Anyway, what you propose shoudl work fine, in principle at least.

 

[heathyoung]

Cool, thanks for that input.

I think the main problems people are having with chains growing is indeed due to the torque that is being placed on them at lower RPM's - since power = torque X rpm, higher RPM = lower torque, so better for the gearboxes and chains.

Running the cyclone at the same wattage (but lower voltage) would require more current (and hence torque) being placed on those rather delicate gears.

I wonder how everyone running RC setups is coping with this as well? (ie. torque on chains) Surely they pedal... Maybe not?

 

[h0tr0d]

But isnt the motor limited to ~3600 giving a "doable" 123rpm@ pedals...?

And that, with 26" and a 11T rear sprocket is 67.5km/h!

 

[boostjuice]

^^^ Wrong dyno plot. That one refers to the gearboxless larger motor. Even the '650W' plot shown doesnt refer to the planetary geared motor (run at 24V). The '500w' plot is for the planetary geared motor, and the best we can do is extrapolate from this (24V/internal controller) out to 48V and with a higher current limit (external controller).

Studying this and extrapolating to 48V, i consider 4~5krpm@48V under load being the best compromise RPM zone to 'hover around' using variable deraileur gearing.

So, to get 70rpm pedal cadence we need ([4500/75]/9.33) = 6.43:1 2nd stage reduction (or a 3rd stage...another source of efficiency loss). Keeping 2 stages can be done with #219 chain with a realistic sized driven sprocket if you rig up some dual freewheel cranks. In my case is used 13T>89T (6.84:1). An 89T #219 sprocket has the same diameter as a 55T bicycle chainring, so ground/frame clearance is doable on most bikes.

 

[boostjuice]

63.81 : 1 reduction to freewheel cranks (with incorporated 9.33 : 1 Cyclone/Headline planetary gearhead)

Allows a comfortable ~70rpm assisting pedal cadence for these motors driven @ 48VDC (matches the best compromise RPM for the loaded motor [~4500rpm/63.81 = 70.5rpm]).

#219 chain stage (13T Rotax kart sprocket > 89T composite Kart sprocket) = [89T/13T = 6.84 : 1] x [9.33 : 1] = [63.81 : 1]

Dual piggy-backed freewheel cranks compensate for the replacement of the standard fitted micro freewheel with a fixed sprocket on the gearbox shaft.

Design credit for the Dual-freewheel cranks goes to ES member 'Briangv99' over here and here

To increase chain stage reduction, the gearbox freewheel is swapped out for a smaller pitch (#219) fixed sprocket allowing a divorce from annoyingly long bicycle chain-pitch micro freewheels (the smallest available being 13T). This allows a larger driven sprocket for greater reduction (in this case the 89T #219 sprocket has the same diameter as a 55T bicycle chainring). BTW, #25 chain doesnt have the required strength to use as an alternative to #219.

A standard Rotax 19mm ID straight bore sprocket is bored out to 20mm and a 'scotch key' fitted (half-round/half-square). Broaching a keyway is not possible as the wall thickness around the teeth area is too thin, hence a rotary cutter is is used to make a partial depth blind channel within the thick wall cross-section.

Before anyone asks, I cant offer these kits for sale. For me this is only a hobby and I simply dont have time.
I hope these detailed photos guide anyone who would like to build a similar system.






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vEVa la revolution!

 

[heathyoung]

Thats a very slick solution - Impressive!

Gets around the problem of trying to pedal the motor around, and the massive sprocket you need to get adequate reduction.

 

[boostjuice]

Thanks. Yes I dare say a 89T bicycle pitch chainring would be a little impractical from a ground/frame clearance perspective

 

[heathyoung]

Yes, that could prove to be a challenge.

I wonder if it is worthwhile trying this with a 9 tooth pocketbike pinion (M8 - cant remember the thread on the end - I think its M6) and a 65 tooth 1/4" pitch chainring. Getting the double-freewheel to work will be interesting...

Gave that idea more thought - the motor would be trying to undo the pinion gear all the time - so no go. It also doesn't solve the issue with chain stretch due to torque at the lower RPM's.

 

[h0tr0d]

63.81 : 1 reduction to freewheel cranks (with incorporated 9.33 : 1 Cyclone/Headline planetary gearhead)

Allows a comfortable ~70rpm assisting pedal cadence for these motors driven @ 48VDC (matches the best compromise RPM for the loaded motor [~4500rpm/63.81 = 70.5rpm]).

#219 chain stage (13T Rotax kart sprocket > 89T composite Kart sprocket) = [89T/13T = 6.84 : 1] x [9.33 : 1] = [63.81 : 1]

Dual piggy-backed freewheel cranks compensate for the replacement of the standard fitted micro freewheel with a fixed sprocket on the gearbox shaft.

<span>Design credit for the Dual-freewheel cranks goes to ES member 'Briangv99" class="smarterwiki-linkify">http://endless-sphere.com/forums/memberlist.php?mode=viewprofile&u=5963]Briangv99[/url]</a>' over here" class="smarterwiki-linkify">http://endless-sphere.com/forums/viewtopic.php?f=28&t=23861#p356222]here[/url]</a> and here" class="smarterwiki-linkify">http://endless-sphere.com/forums/viewtopic.php?f=28&t=15529&hilit=briangv99#p267017]here[/url]</a></span>

To increase chain stage reduction, the gearbox freewheel is swapped out for a smaller pitch (#219) fixed sprocket allowing a divorce from annoyingly long bicycle chain-pitch micro freewheels (the smallest available being 13T). This allows a larger driven sprocket for greater reduction (in this case the 89T #219 sprocket has the same diameter as a 55T bicycle chainring). BTW, #25 chain doesnt have the required strength to use as an alternative to #219.

A standard Rotax 19mm ID straight bore sprocket is bored out to 20mm and a 'scotch key' fitted (half-round/half-square). Broaching a keyway is not possible as the wall thickness around the teeth area is too thin, hence a rotary cutter is is used to make a partial depth blind channel within the thick wall cross-section.

Before anyone asks, I cant offer these kits for sale. For me this is only a hobby and I simply dont have time.
I hope these detailed photos guide anyone who would like to build a similar system.

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vEVa la revolution!

Boost, most impressive drivetrain, great job! 8)

Can you give us a parts list and suppliers?

Thanks!!

 

[boostjuice]

Boost, most impressive drivetrain, great job! 8)

Can you give us a parts list and suppliers?

Thanks!!

Glad you like it, hopefully you can get access to or funding for a bit of milling/turning to create some of the custom/modded parts this assembly requires.

Most of the Dual freewheel crank parts are listed by the designer ES member 'briangv99' in his thread over here

But anyway here are the parts I used;

EDIT: 1x 'GGoodrum' freewheel > 4 bolt kart sprocket adapter modded to 5 x 5mm bolt pcd (contact him through ES or TPPacks.com to see if he still has some from his original batch run)
1 x 206mm 'First components F-200IE bottom bracket with 3/16"keyway
1 x 5/8" bore, 3/16" keyway Freewheel adaptor for 1.375" 24tpi freewheels
2 x Keys 3/16" x 3/16" x 3/4"
2 x Front Freewheel - Heavy Duty (White Industries 5-bolt ENO) [I used 1x of these and 1x 22T ENO freewheel only because i already had one. Its cheaper just to use 2x of the sickbikeparts units]
1 x Freewheel Crank Set, Square taper
Rotax 13T #219 sprocket
Extron #219 89T sprocket
1 x 55T, 130mm BCD, 9spd chain compatible chainring
5 x 16mm long chainring bolts
1 x 6002-2RS bearing
Various custom length (ie. hacksaw & hand file) round/pan head 5mm & 6mm setscrews, locknuts, washers etc.

1 x Custom ring 25mm OD x 20.2mm ID x 5.5mm length [spacer between gearbox shaft circlip and sprocket]
1 x Custom washer 25mm OD x 6mm ID x 3.5mm length [retainer for outbound side of gearbox shaft mounted sprocket]
1 x Custom ring 22mm OD x 16mm ID x 16mm length [spacer between BB bearing and freewheel adaptor]
1 x Custom chainring adapter for 5 x 130mm BCD x 10mm hole > 5 x 67mm BCD x 5mm hole, [145mm OD x 54mm ID x 3mm thickness] (to adapt to flanged Freewheel)
1 x Custom Kart sprocket adaptor for 6 x 5.25" BCD x 6mm hole > 5 x 67mm BCD x 5mm hole, [148mm OD x 54mm ID x 3mm thickness ] (to adapt to flanged Freewheel)


The pictures combined with briangv99's instruction show most of the work needed to fabricate the Dual Freewheel crank setup. Things i did different were;

- I extended the keyway in the BB spindle inbound so that i could use 2x of the 3/4" length pieces of key-steel for extra surface area in keying to the freewheel adaptor
- Turned down the outer portion of the crank spindle from 5/8" > 14.98mm for the ID of the 6002-2RS support bearing
- Turned out the inner portion of the tool removal collar of one of the flanged freewheels to 32.02mm for the OD of the 6002-2RS support bearing

As mentioned already, regarding the Rotax sprocket, i also had to turn out the standard ID of the bore from 19.02mm > 20.02mm and mill a scotch keyway. The standard piece of 6 x 6mm key-steel that came with the cyclone motor freewheel adaptor was modded[filed] to be half-round to match this.

 

[Gab]

Hi Boost juice where did u get the 16mm chain ring nuts from ?

Are they the same size and thread as normal chain ring nuts ? i.e to suit a 10mm hole ?

 

[boostjuice]

Hi Boost juice where did u get the 16mm chain ring nuts from ?

Are they the same size and thread as normal chain ring nuts ? i.e to suit a 10mm hole ?

http://problemsolversbike.com/products/chainring_bolts/

 

[epack]

Thanks for all the links. Great job on this one.

 

[TRRRR]

I have a 36 V cyclone kit with the programmable kelly controller. One of the options in the Kelly software is a speed limit % and in the description of what this function does it says it is limitting motor voltage to a percent of battery voltage. This sugests to me that the 48V battery could be made to drive the motor at 24 V and elliminate the motor gearing problems letting you pedal at a more human speed to keep up with the motor. I would also think the efficiency curve of the motor would shift to lower RPMs. If this is true people could buy a 36 or 48 V battery then speed limit it to get the high efficiency band at the speed you want it.

Is anyone able to confirm that this is what the kelly controller is doing and is there any down sides to using this function?

 

[boostjuice]

Unfortunately, the Kelly controller isn't going to give you a "free lunch" here. All that setting it is doing is putting a threshold limit on the controllers PWM duty-cycle to limit speed electronically just the same as if you wired your throttle so it was capped from transmitting a FULL-ON/100% speed signal voltage (somewhere between ~4>5VDC for the usual chinese hall-effect sensor based throttles).

In both cases, the motor is simply enduring increased phase current multiplication (the motor coils act as an inductor the same as in a bucking SMPS), the controller is slightly less efficient (due to the added PWM switching required vs 100% duty cycle of a full throttle input), and the motor is not spinning as fast as it could be to achieve added power with an up-shifted efficiency curve (the entire point of running these cyclone motors on 48V).

The reason Kelly adds that option in the programming software is so the user can literally impose a travelling speed limit in single drive ratio applications, or so that the motors commutation sequencing can be kept synchronised with the controller in the case of a high pole count/high rpm motor that has the ability to spin faster than the controller can keep up with (keeps the motor's speed within the contraints of the controllers electrical rpm limit).

 

[TRRRR]

Ok, thanks for your reply. That must be just a poorly worded description by Kelly then if they mean duty cycle limit when they say % of battery voltage. I did actually put an oscilloscope on the thick blue and yellow wires from the kelly yesterday and saw some sort of a square wave (with some other waveforms within the square pulses - dont know what they are there for?) and yes, the height of the voltage pulses remain constant (at about 40 volts for my 36 V battery) even when you change the speed limit. That's a bit of a shame since the ability to change the voltage driving the motor with a fixed voltage battery would be a nice feature in an ebike controller. I am not an expert in electronics but I suspect it may be possible to do something like this.

 

[oldskoolhead]

63.81 : 1 reduction to freewheel cranks (with incorporated 9.33 : 1 Cyclone/Headline planetary gearhead)

Allows a comfortable ~70rpm assisting pedal cadence for these motors driven @ 48VDC (matches the best compromise RPM for the loaded motor [~4500rpm/63.81 = 70.5rpm]).

#219 chain stage (13T Rotax kart sprocket > 89T composite Kart sprocket) = [89T/13T = 6.84 : 1] x [9.33 : 1] = [63.81 : 1]

Dual piggy-backed freewheel cranks compensate for the replacement of the standard fitted micro freewheel with a fixed sprocket on the gearbox shaft.

Design credit for the Dual-freewheel cranks goes to ES member 'Briangv99' over here and here

To increase chain stage reduction, the gearbox freewheel is swapped out for a smaller pitch (#219) fixed sprocket allowing a divorce from annoyingly long bicycle chain-pitch micro freewheels (the smallest available being 13T). This allows a larger driven sprocket for greater reduction (in this case the 89T #219 sprocket has the same diameter as a 55T bicycle chainring). BTW, #25 chain doesnt have the required strength to use as an alternative to #219.

A standard Rotax 19mm ID straight bore sprocket is bored out to 20mm and a 'scotch key' fitted (half-round/half-square). Broaching a keyway is not possible as the wall thickness around the teeth area is too thin, hence a rotary cutter is is used to make a partial depth blind channel within the thick wall cross-section.

Before anyone asks, I cant offer these kits for sale. For me this is only a hobby and I simply dont have time.

vEVa la revolution!

intresting what would you charge for a set up like this?
im in the process of getting parts to convert my carerra centos and have decided on the main parts and ordered a kelly controller last night (kds48100 24-48v 100a) and chose this controller because i could buy a larger motor and program it to comply with uk regulations but still have the option of having some fun off road so i decided from a cost and availability perspective i wasnt going to use a brushless cyclone and use a brushed unite my1020z 36v 450w (similar to the gng kit) but am still contemplating how im going to gear this correctly assuming i will need to find a free wheel for the motor which is going to cock the reasonable cadence of about 104rpm i would get using the smaller motor sprocket that comes with it. plus if the shaft is different to the available cyclone free wheels is going to be another headache. i would also like to find a solution where by i could keep my 3 speed front mech system as well which i thought i could change one of the 48 tooth rings for my 44 tooth outer ring or maybe my two smaller rings i have on my current crank and add a much larger one i was thinking possibly mounting it to the holes that are occupied by the chain guard as most of the larger chain rings ive found in fact all of them have 5 pin mounts which it seems the chain guard has too though weather they are the right size and position to enable this is purely speculation, but im open to any suggestions or alternative solutions especially if they will keep the cost down and can be fabricated with readily available parts, which incidently the bike and the controller and programming rs232-usb lead are the only parts ive actually commited to and paid for so still have the flexibility to use a different motor if need be hence why i chose the 24-48v controller.
another point to mention i was hoping to get a big enough battery to give me some mega range as well so info on the mpw/h i can expect from this set up would be much appreciated as well as i was hoping to be able to on occasion make the 60 mile journey to visit friends though this may be ambitious lol but i would certainly want to be able to cover the 15 or so miles to visit my family which the piece of dog poo sakura bike im riding to work at present wont allow
once ive got all the parts together i will be videoing the process of the build as well for youtube as i also plan on building an aluminium case inside my frame to house the motor controller and hopefully at least some of my battery lol but this will be some time off due to financial limitations ill be collecting the parts bit by bit lol

 

[boostjuice]

That's a bit of a shame since the ability to change the voltage driving the motor with a fixed voltage battery would be a nice feature in an ebike controller. I am not an expert in electronics but I suspect it may be possible to do something like this.

Yes this can be done, but it's terribly inefficient. What your describing is a 'linear regulator'. The problem with using these in a motor controller is that the difference in [battery voltage minus phase-coil voltage * current] = [rejected Power], and must be dissapated as waste heat from within the device. Apart from the unacceptably high losses from an energy efficiency standpoint, for a motor controller this would be a stupendous amount of heat to dissipate at low speeds [High dV(IN)/V(OUT)], and hence it isn't done (and the reason why SMPS are so much smarter/cheaper in most high power applications where output ripple noise isn't of much concern).

The vast majority of mass market, bicycle/scooter BLDC motor controllers are setup as variable output speed commutation sequencing devices that are fundamentally just a SMPS without smoothing caps accross the phase coil load. With a small amount of digital electronics knowledge you will quickly understand that although the battery voltage remains more-or-less constant as it's shunted through the controller's FETs and into the motor coils, the PWM 'chopping' ratio (ON-time vs. OFF-time) of this constant-voltage by the FET's during each commutation iteration passes a variable average of voltage/power into the motor's phase coils. Hence the motor sees a lower average voltage when the speed signal is <100% duty cycle. Take for example 50% PWM with a 40VDC battery. The average voltage of half the ON-time@~40VDC vs half the OFF-time@~0VDC = 20VDC average voltage. The motor will spin at half speed under this condtion.

Admittidely the above explanation is a little oversimplified as the other consideration the motor controller has to deal with is it's battery current limit. To keep the motor's current draw in check as well as keep within the delivery capabilities of the controller (within it's nominal power rating), some phase conduction PWM is needed at higher-load/lower-rpm (where the phase coils are in a lower impedance state due to little back EMF) to keep the motor from pulling high current that the battery/controller and motor can not deliver/sustain. Thus, even when the speed throttle may be pegged at 100%, under these conditions, there is likely a <100% duty cycle condition.

 

[TRRRR]

I was thinking of something more like a transformer that can step-up or step-down AC voltages with minimal losses. the only trouble with using one of these is that you need to change the number of turns of wire on the coils to change the output voltage, or maybe have a switch to flick between a set of small transformers with different windings. It wouldn't be too hard to retrofit one of these to the output of your controller if you really did want to change the voltage.

 

[amberwolf]

Except you cant' just use a transformer, becuase it will only output during a change in voltage (current, really) at it's input. Since the typical controller output has a fair bit of DC component to it, it is not going to output much like the input waveform.

Additionally, you'll need quite the hefty transformer to handle the currents necessary, most likely. And if it's a three-phase motor, you need three of them, probably each the size of your motor.

 

[waxman123]

Boostjuice

Great work on the two freewheel set up!!!!

Thank you for postiing all the info I have ordered all my items from sickbikes and adrenlane carts!! This is going to be the best fix to my worst complaint about the Cyclone set up! I have an EGO system and am very happy with the fit and finish but hate that the cadence is so fast. I even put a three speed switch on and it worked good but was a band aid at best.

My question how are you conecting the two freewheels togetheer. I do not see any parts called out for that. I see, and understand, how the system works and I can handle the light fabrication that is required.

For the life of me I can not see how you are connecting the left side to the right. I understand that the left is normal orientation and the right side gets flipped around but how are you connecting them together!

 

[briangv99]

My question how are you connecting the two freewheels together.

I think Boost is using the same part I used, it was a freewheel adapter produced by a member (GGoodrum) a few years back made for attaching a freewheel to a 3 speed IGH. Gary doesn't list the part on his website (tppacks.com) anymore, but maybe you could email him to check if he still has some.

This is thread where the adapter first came about
http://www.endless-sphere.com/forums/viewtopic.php?p=178191#p178191

 

[oldskoolhead]

would it not be possible to use a cut down wheel hub for this part ie just keeping the thread and the spoke flange and drill your 4 holes in the flange or add a plate to drill these holes if the diameter is too small?

 

[boostjuice]

would it not be possible to use a cut down wheel hub for this part ie just keeping the thread and the spoke flange and drill your 4 holes in the flange or add a plate to drill these holes if the diameter is too small?

That's a resourceful idea that I suspect would work, but without modification maybe not quite as well as the Goodrum adapter depending on the exact hub in question. I suspect that because typical spoke flanges on hubs have a tapered wall thickness, this interface point might result in a larger gap between the flange face and the freewheel body thus consuming a little more precious lateral space along an already crowded bottom bracket spindle. Still, if you turned down the spoke flange faces so they were perpendicular to the hub axle right down to the freewheel section and extended the freewheel threads (leaving a smalled stepped clearance gap for the freewheel outer to clear the flange face) almost up to it on a lathe it would likely work just dandy.

Also, just a correction, its 5 holes you want drilled in the flange. The Goodrum adapter is drilled as standard to adapt to the standard 4 bolt #35 Kart sprocket interface, and as such must be modified for the 5 hole BCD of the Dicta/ACS Crossfire/WI ENO flanged outer freewheels. (take a closer look at Brian's photo to see how he's drilled 'on-top-of' the original 4 larger diameter holes.