Freewheel crank resources

[Kobushi]

I have been lurking on this forum a while trying to plan an ebike build of my own, I am not very familiar with bicycle parts and I'm wondering how universal these freecrank parts are?

I'm looking to use a pretty cheap bike to start out with (currently eyeing a Schwinn Tourist 700c from Target). But I am not clear as to which (how many) parts of the original crank assembly will have to go. I plan to ditch the gearing up front and go with a single so I can run the chain over the motor sprocket directly with some tensioners and alsignment guides. OR useing a freewheel crank as a jackshaft between the motor and rear drive.

Anyway my main hurdle here is wrapping my head around all of the components involved with a front freewheel crank assembly.

Obviously I need the freewheel, and I see that I need some sort of an adaptor to mount the freewheel to the sprocket(s) that the chain(s) will hook to.
But will the freewheel thread to the existing bottom bracket? Or will that need to be replaced with something special? If so can I be pretty confident before buying the bike that such a bracket for it's size/type (1pc, 3pc idk what it is yet) exists?

Thanks for any info you can give me.

 

[Miles]

Hi Kobushi,

You'll probably need:
- New bottom-bracket.
- Trials cranks (or Cyclone version).
- Freewheel.
- Freewheel to chainring adapter.

The freewheel threads on to the trials crank.

Changing the bottom bracket shouldn't be a problem.

 

[jdcburg]

Hi Kobushi - Sick Bike Parts http://sickbikeparts.com/catalog/catalog.php has everything you need to put a freewheel crank on your ebuild. They also answer emails and offer technical assistance - jd

 

[deecanio]

go for the widest bottom bracket you can - 128mm i beilieve, this will give you more space to setup.


D

 

[dequinox]

I have built my bike around the sickbikeparts kit, and I use the el-cheapo freewheel. I can tell you all that the cheaper one has a life of about 3-4 months before it takes a $#!t. That was about 500 miles I think. Not very long, but they are cheap...$21 on electricscooterparts. I know most of you are interested in the higher-end stuff and I think I will upgrade as soon as I can afford to put more money into this thing.

Also I have been having trouble with chain clearance from my outer drive chain and my rear sprocket drive chain. If I'm down in 8th gear they tend to collide and wreak havoc. Also I think the angle may be a bit too extreme for the chain to handle without twisting and eventually separating at the joinup point...I've had a few chains thrown off on me. Suggestions are always welcome!

 

[amberwolf]

You could make a chain deflector as I did (see pics in this post) that guides the rear drivetrain chain "around" the motor chain. But it will add noise (a little) to the system, and it will wear, causing you to eventually have to readjust or replace it to continue working.

Alternately, you can do what was suggested to me in this post, of increasing the distance from chainring to chainring, if you have room for that.

 

[dequinox]

I might try chopping up a rear derailleur for the pulley...and guide it that way. Even then I would still get the extreme angle as seen in the pic below. That tends to bend the links in the chain, I've found, and eventually retires the link where I joined it. I've found using master links vs just using a chain breaker to put it back together works better though. I think what I really need to do is better center the "rear" drive chain, because I can adjust the "chainring" drive chain as much as I need to. Some kind of a spacer for the crank freewheel and some washers for spacing the inner one should work a lot better.

 

[amberwolf]

That chain angle/wear problem is why it's usually not recommended to run on the granny ring and the high gear at the same time. Same for speed outer ring and low gear in back.

On my rear drivetrain, the regular bicycle part, I am almost always using the outer ring on the triple and the entire range on the rear cassette. Fortunately, the parts I have on there happen to line up such that it is closer to centered using the outer than it is with the middle ring. Though that means when I have to use the granny it sometimes rubs on the fat tire.

 

[dequinox]

I only have the two rings, and I do know about that whole problem. Running the granny and the largest crank ring is counter-intuitive anyways :lol:

I think I'll space the rings out more...especially the larger ring. I need to find a "spacer" that is machine-flat to serve as a spacer for the outer crank ring, and then I will try to dead-center the inner crank ring with the cassette so that the extreme angles are equal. That should solve the problem. Really it's only a problem now if I use the 2 highest gears (that is 7 and 8), but it would be nice to have those available without worries of chain-wrappage. Thanks again for the suggestions!

 

[amberwolf]

Do you have a crank puller?

If so, you could check to see if the crankshaft you have is symmetrical or not, from bearing ring to bearing ring. If it is not, it's possible that the longer end is actually installed on the *left* side right now. I don't know why but I have found a number of bikes done that way, when I would have expected the longer side on the right.

Anyway, if it is longer on the left, just flip it over, reinstall your cranks, and they may end up far enough out on the right side to help with the chain problem.

As for spacers, go to the thrift store and find some flat-bottomed aluminum sauce pans. Most of them have pretty thick walls, and sometimes an even thicker base. Usually at least 1/8", a couple I've seen were nearly 1/4".

Drill a small centering hole, then mark a circumference around it to cut out that matches the size of the spacer you need. If you don't have a way to power-tool-cut the circle out, you can either just go around and around and around it with a protractor, pencil end in the centering hole and sharp tip on the cirumference ring, or you could small holes all around it until you've perforated it enough to punch out.

Same thing on the inside, to cut out the center of the spacer ring.

You can also use the saucepan bottoms to make whole sprockets from, too, or other chainring adapters.

 

[Malcolm]

On bolt circle diameters and chainring spacing:

I’m rebuilding my bottom bracket drive in readiness for the arrival of a new Cute 128 motor. To make a simple job really complicated I decided while I’m at it to make a new chainring adapter for the White Industries freewheel that will take as wide a range of chainrings as possible. I hadn’t realised just how many different sizes there were: http://www.sheldonbrown.com/gloss_bo-z.html

Thought it might be useful to list what I’ve found. The most widely used current BCD patterns are:

5-arm cranks
135 mm Campagnolo
130/74 mm Road double and triple (smallest ring 24t)
110/74 mm Old MTB standard (smallest ring 24t)
94/58 mm Compact MTB

4-arm cranks
104/64 Compact MTB (smallest ring 22t)

The White Industries freewheel http://www.sickbikeparts.com/catalog/product_info.php?cPath=21&products_id=62&osCsid=5m4qhpu4l5rmebkpfrm5utej60 unfortunately has a bolt circle diameter that matches none of these, at 67.5 mm.

The old MTB standard of 110/74 mm seems to me to give the ideal combination of strength and gearing range, while also matching the five-hole pattern of the freewheel. This adapter could also have holes at 130 mm for road bike rings

Alternatively a four-arm adapter would be needed to accommodate the increasingly popular 104/64 bolt pattern. Miles has already modelled an adapter a few pages back.

Now a question. I’ve spent a couple of hours searching for information on chainring spacing and still not found a clear answer. Is there a standard chainring spacing? The usually dependable Sheldon Brown mentions a “typical” spacing of 5 mm, but measuring up a couple of cheap cranksets I have to hand gives me a spacing of 7.5–8 mm. I bet the answer isn’t straightforward

Malcolm

 

[amberwolf]

Based on the various bits I have around, I'm guessing that crank spacing depends on the bike's overall gearing range; if your bike was made for a 9-speed rear cassette, it's a good bet that the cranks are closer-spaced so that the narrower chain required for the rear cassette will be less likely to get jammed between the chainrings in front during derailing.

But on bikes with say 5-speed rear cassettes, the front can be wider spaced for the wider chain used on those.

 

[Malcolm]

Thanks amberwolf. I've come to the same conclusion that there are small variations depending on the number of gears. I expected to find the precise spacing widely documented, but there's a real dearth of information. I'm guessing that chain ring spacing has to be correctly adjusted to within half a millimetre or so on newer systems with indexed front shifting, otherwise shifting will be slow. If anyone can give me any specific information about chainring spacing for their own setup I'd be very grateful.

 

[Sturdly]

Dequinox, I just took five nuts about 2 sizes bigger than the bolts that go through the freewheel so they would not thread on, just spacers basically. Put them between the face of the freewheel and the back of the drive ring. Still caught enough shoulder on the freewheel to center the ring but moved the drive ring out close to 3/8". Plenty of space for chain clearance now. Of course I then added another drive ring outside of that with even more spacers, 52t for lower gearing. Now I can pick my reduction ratio for the motor and that all clears the deraileur so I still have the three front shifted rings of 28t 38t 48t. So many gears, so little time. Woo hoo!

 

[dequinox]

@Sturdly Thanks for the input, the kit does come with nut spacers like that. My problem at that point a long while back was how to space the inner ring out and not have it hit the frame! I determined that I could shift the bottom bracket over by adjusting the cups so they sat over a little further and that solved the problem.

 

[johnrobholmes]

A big bump from the dead.

Anybody ever come across a freewheeling 3 ring front? I remember seeing one somewhere, but cannot find it anymore. I see that sickbikeparts has bits to almost make something, but I am wanting something a bit nicer and lighter with shift ramps on the rings. The option I am kicking is to have a spider made to work with standard rings, but that bolts onto the freewheel that sbp carries http://www.sickbikeparts.com/catalog/product_info.php?cPath=21&products_id=62&osCsid=r77vleq1cmgi3nhl942s7np475


I love my old trusty build that is nice and light, and don't want to spend any more amperage to get better performance. This has lead me on a chase to run a hub motor through the gears.

 

[amberwolf]

I wonder if there is enough material on any regular spider to just lathe it out until it fits a crankshaft freewheel?

Probably not. So next best is to custom make a bolt on ring to go onto a standard freewheeling crank, with the ring having holes and offsets on it for three rings, assuming spacing allows.

 

[briangv99]

Anybody ever come across a freewheeling 3 ring front?

There was the Shimano Front Freewheel System from the early 80s, might find a second hand one laying around

http://velobase.com/ViewComponent.aspx?ID=3205D893-3860-4392-B3A6-76273D450225&Enum=115&AbsPos=81

 

[dequinox]

I wonder if there is enough material on any regular spider to just lathe it out until it fits a crankshaft freewheel?

Probably not. So next best is to custom make a bolt on ring to go onto a standard freewheeling crank, with the ring having holes and offsets on it for three rings, assuming spacing allows.

That actually sparked an idea AW, I'll get back on here and post Solidworks drawings/model views when I have time to complete it.

 

[Rassy]

JRH said:

The option I am kicking is to have a spider made to work with standard rings, but that bolts onto the freewheel that sbp carries

John, Than should work, but I don't see why you need a 3 dimensional spider instead of just a flat disk like AW mentioned. Then use spacers for the 3 rings.

But the reason I responded, I used the SBP freewheel on my trike, and there wasn't enough clearance between the crank and the BB housing. I should have gotten a BB with a longer axle, but instead I just ground off the "removal" tabs from the freewheel, so I will probably never get that freewheel off the crank arm, but it's working great so far.

Also, I got the biggest chainwheel SBP had, 48T, and decided I needed a larger one, so just drilled holes in the 48T chainwheel to attach a standard 56T chainwheel. Also working good, but the solid steel 48T chainwheel used as an adapter is heavy overkill. With any milling capability it should be fairly easy to make a nice looking lightweight adapter ring.

 

[dequinox]

Just a start on an idea I had, I know its been thought of before but I thought I'd keep modifying this until I got something similar to Matt's disc brake adapter. It would fit any 16t shimano freewheel so you don't have to wait on SBP for an HD wheel if they are out of stock... and the idea is to make the bolt pattern fit standard crank chainrings instead of the big thick ones on SBP. I might lose the CNC nubs and just use the bolt radius to lock the teeth into the bigger ring. Especially since a 1-off laser cut part would be cheaper than a cnc operation like that. The intent is for this to be open source. I have research to do on the bolt hole patters of STD crank chainrings and all that still...but comments etc are appreciated.

 

[Miles]

I might lose the CNC nubs and just use the bolt radius to lock the teeth into the bigger ring.

Hi dequinox,
Maybe use a "washer" on the bolt to match the radius of the teeth root? It would be the same thickness as the teeth to act as spacer.

 

[johnrobholmes]

Would you mind putting an iges or step file of your freewheel into the component thread dequinox? http://endless-sphere.com/forums/viewtopic.php?f=28&t=19549

 

[dequinox]

I'll try to figure out how to create a step file this week and get it up there. I actually didn't make the model, it was available on the SW website for download. I've not a clue about step files but I'm thinking its just "save as" and then select stp file right?

 

[johnrobholmes]

yep. I will hit up SW and find that file then, thanks!