Freewheel crank resources

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Freewheel crank resources

Postby recumpence » Thu Nov 27, 2008 8:34 am

Hey Guys,

I am coming to the conclusion that freewheeling cranks are one really good solution to our non-hub drive desires. There seems to be alot of confusion about this especially for me because I have never found a decent freewheel crank setup, nor do I really understand all that is involved in setting one up. To that end, I wanted to start this thread as an area to compile freewheel crank options in one thread so we can pool our resources and compare ideas.

Here is one set of freewheel threaded crank arms I found. They can be aquired in two bore arrangements.

http://www.webcyclery.com/product.php?p ... 415&page=1

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Re: Freewheel crank resources

Postby AussieJester » Thu Nov 27, 2008 8:37 am

Quite simple to make them Matt surprised you would be looking at buying them :-|
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Re: Freewheel crank resources

Postby recumpence » Thu Nov 27, 2008 8:43 am

I can make anything! :wink:

Primarily I am looking at options that we can all benefit from. I understand fabrication. What I am unfamiliar with are products that are ready made and available to the average Joe. I also want a list of various options to keep myself and others from having to scratch build a set. My recumbent crank arm has enough material to mill and thread for a freewheel. But, I do not want toe aggrivation if I can just buy a set without breaking the bank. :D

Also, I am a fabricator, not as much a bike mechanic that knows all the ins and outs of every bike part out there.

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Re: Freewheel crank resources

Postby Miles » Thu Nov 27, 2008 8:46 am

Hi Matt,

Good idea to start a thread for this.

The problem is that (for our use) torque levels at the crank are around 3 times greater than at the rear hub - so you need a good quality freewheel.

The best ones seem to be the ENO (White Industries) and the Tensile (Onza).

The ENO 22t is a particularly convenient one to adapt because it has 5 circumferentially milled slots which can be used to bolt to.

So, you screw your freewheel onto the trials cranks and then you need an adapter to mate up with one of the three common chainring BCD standards. 104mm 110mm and 130mm. For my bike, I designed a chainring to fit directly to the ENO 22t freewheel (see photo).




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Re: Freewheel crank resources

Postby Miles » Thu Nov 27, 2008 9:00 am

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Re: Freewheel crank resources

Postby deecanio » Thu Nov 27, 2008 9:58 am

good thread.
I like the one Matt posted as its square taper (i have lots of square taper arms and bb's) - however they only show the arms - wheres the freewheel then? i also wonder what the thread is for the pedals.
More research needed here, does anyone know if you can use any length BB ??? they recomend 127mm for square taper which is exactly what i have already :mrgreen:

EDIT ** i Knew i'd seen those arms on a class bike somewhere**

Cheers,

D
Last edited by deecanio on Thu Nov 27, 2008 10:23 am, edited 1 time in total.
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Re: Freewheel crank resources

Postby safe » Thu Nov 27, 2008 10:02 am

I just took a regular steel one piece crank I had laying around and cut apart a spare rear freewheel hub in order to cannibalize the threads. I then welded the "half hub" threaded piece backwards onto the steel crank. Take a regular BMX freewheel and add a homemade spider to connect to the sprocket and that's all. It seems okay so far, but I don't have a lot of testing on it yet.

(so my solution was basically free... but a lot of work)

I know you guys are talking about "real parts" but it should be mentioned that the cheap way is just to weld something up.
Last edited by safe on Thu Nov 27, 2008 10:07 am, edited 2 times in total.
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Re: Freewheel crank resources

Postby Miles » Thu Nov 27, 2008 10:04 am

D,

127 mm should be fine.

I used this 122.5mm one http://www.tartybikes.co.uk/product.php ... ory_id=100 which has a RH offset.

Threads are the ubiquitous 1.37" x 24 tpi
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Re: Freewheel crank resources

Postby TylerDurden » Thu Nov 27, 2008 10:13 am

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Re: Freewheel crank resources

Postby recumpence » Thu Nov 27, 2008 10:54 am

Gulp, a little pricey, but oh so sweet! :mrgreen:

http://www.webcyclery.com/product.php?p ... 420&page=1

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Re: Freewheel crank resources

Postby Miles » Thu Nov 27, 2008 10:59 am

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Re: Freewheel crank resources

Postby recumpence » Thu Nov 27, 2008 11:05 am

Man, you beat me to it! I was just coming over from e-Bay to post that link.

You are too fast! :mrgreen:

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Re: Freewheel crank resources

Postby Miles » Thu Nov 27, 2008 11:10 am

:)
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Re: Freewheel crank resources

Postby recumpence » Thu Nov 27, 2008 11:18 am

So, the question is, is it better to run a longer chain around the power unit, then around the freewheeling chainring to the rear cassette, or is it better to have two front chainrings with one chain being driven by the motor to the larger chainring and the second chainring driving a second chain to the cassette like Gary is doing on his Cyclone system?

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Re: Freewheel crank resources

Postby Miles » Thu Nov 27, 2008 11:31 am

There are pluses and minuses..

Driving the cranks means an extra gear reduction step which is then reversed.

Driving the chain directly needs careful alignment and can be problematic with derailleurs. Probably an idler/guide-pulley will be needed, to get enough chainwrap on the motor drive sprocket.

Another option is a serial drive of the type that Mitch is planning. [Drives are combined on a jackshaft and a second chain goes to the wheel from there].
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Re: Freewheel crank resources

Postby recumpence » Thu Nov 27, 2008 12:38 pm

Agreed, an idler would be needed.

I like the serial drive option, except that I do alot of pedal only riding too and use the motor for hills and what-not. A serial drive has noticeable added drag. Non-serial drives have much less drag and seems to be roughly the same amount of work to complete.

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Re: Freewheel crank resources

Postby Miles » Thu Nov 27, 2008 12:50 pm

If the motor drove the chain after the chainwheel (normal Cyclone set-up), it would be possible to disengage it completely - absolutely no extra drag.... Just a thought....
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Re: Freewheel crank resources

Postby recumpence » Thu Nov 27, 2008 1:11 pm

That would be easy for me using RC equipment. I could use a high torque servo to engage and disengage the motor with the first 25% throttle movement, then have the ESC activate after that point.

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Re: Freewheel crank resources

Postby Miles » Thu Nov 27, 2008 1:28 pm

Neat idea :D
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Re: Freewheel crank resources

Postby MitchJi » Fri Nov 28, 2008 3:43 am

recumpence wrote:Agreed, an idler would be needed.

I like the serial drive option, except that I do a lot of pedal only riding too and use the motor for hills and what-not. A serial drive has noticeable added drag. Non-serial drives have much less drag and seems to be roughly the same amount of work to complete.

Matt


Hi Matt,

Serial drive the pedals and motor turn the same shaft. If there is a FW on the motor end of the shaft I think the only extra drag when pedaling would be (if I'm missing something let me know):
    1. the longer shaft
    2. the friction of the FW
    3. possibly a crooked chain line

I don't think 1 and 2 are significant. Marcus (who did a lot of testing) told me 3 isn't very much.
Best Wishes!

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Re: Freewheel crank resources

Postby Miles » Fri Nov 28, 2008 4:10 am

MitchJi wrote:Serial drive the pedals and motor turn the same shaft. If there is a FW on the motor end of the shaft I think the only extra drag when pedaling would be (if I'm missing something let me know):
    1. the longer shaft
    2. the friction of the FW
    3. possibly a crooked chain line

I don't think 1 and 2 are significant. Marcus (who did a lot of testing) told me 3 isn't very much.


Mitch,

Yes, the losses from chain mis-alignment would be minimal.

If you're comparing this system with others, you haven't taken into account the fact that the pedal drive uses a second chain run....
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Re: Freewheel crank resources

Postby recumpence » Fri Nov 28, 2008 9:10 am

The losses I am referring to are primarily the fact that two separate chains are used in series to drive the rear wheel. It is not a huge loss, but enough to feel while pedalling.

For those who do mostly motoring, that is not an issue. For those who do mostly pedalling, it can be an issue. Not a terrible issue, but an issue non-the-less. :)

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Re: Freewheel crank resources

Postby John in CR » Fri Nov 28, 2008 10:58 am

The serial drive I would want to work toward for a scratch built bike would have the combining shaft be the crank shaft. Wouldn't that be the ideal use of freewheels on the crank? Then the only inefficiency to overcome for pedal only use is the extra freewheel for the motor's sprocket on that shaft, though I'd imagine that the heavy duty bike chain required may be less efficient than lightweight chain.

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Re: Freewheel crank resources

Postby Miles » Fri Nov 28, 2008 11:33 am

Yes, that would be better for pedalling but less efficient for the motor. There's no ideal set-up - pick your compromise for the intended use.
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Re: Freewheel crank resources

Postby John in CR » Fri Nov 28, 2008 12:28 pm

Miles wrote:Yes, that would be better for pedalling but less efficient for the motor. There's no ideal set-up - pick your compromise for the intended use.


Why, as long as it's all an integral part of the gearing stages of the motor? The few % loss of the final stage being the bike chain should definitely be worth it to obtain variable gearing, and isn't only a loss if you aren't pedaling, or am I looking at it wrong and the loss is variable, not a fixed loss?

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