let's talk sprockets

Agreen

Agreen

Member
Hey everyone, I'm in the big middle of building a Skyhawk bicycle frame w/ a 48cc 2 stroke. I'm still in the process of building the actual bicycle right now and I've made some good progress. Having never built a bicycle before, the learning curve has been steep. I thought I could transfer everything over from a Schwinn cruiser, and I was way wrong. So what I ended up with is parts from a couple different bikes all mashed in to one. The front forks are mountain bike "shock" forks, cruiser handle bars, cruiser one piece pedal crank, and mountain bike wheels with cruiser 2.125" tires. So far it looks good.

One thing I'm a little unsure of is the rear sprocket. The mountain bike's rear wheel is a 7 speed freewheel. What I want is a single speed freewheel. One person suggested a bmx single speed freewheel.

I guess my real question is "how will I know it fits when placing my order?". What I currently have is a freewheel that uses an FR1 style tool for removal.

http://www.amazon.com/gp/product/B001B6RGXG/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=AJ5KCH6R81QUN

And the freewheel looks somewhat like this one:

http://www.amazon.com/Shimano-Tourn...=1429840912&sr=8-3&keywords=shimano+freewheel

So do I HAVE to get one that uses the same tool to fit on the axle? Or can I get a different style, but single speed, freewheel and it threads on the same?

I only ask because I'm finding out more and more that not all bicycles are made the same. Different size/styles on lots of components such as seat tubes, fork tubes, rear axle widths, etc.

Thanks in advance.
 
Why would you want to loose your rear pedal gears on a 48cc direct drive?
You are really going to want them to help pedal along.

If it's because of the shifter on the handlebars just use a rotary on the left with the clutch and put a dual pull brake lever on the right with throttle.
 
On the freewheels themselves, both of those styles of freewheel will have the same threading and since they thread on in the direction the chain pulls, you can hand tighten them as far as you can, then use the cranks (or a chain whip if you have one) to tighten it down all the way. That part is the same regardless if you use a BMX or multi speed freewheel. It's only the removal tools that vary on modern stuff. If you don't care about destroying the rusty freewheel, you can use a screw driver and a hammer in a pinch to back one out. Whatever you have to do to grab and spin the splines. Lefty-loosy.

Here's a good article about Freewheels:
http://sheldonbrown.com/freewheels.html

The big variance you'll need to pay attention to when selecting a freewheel is if it's 1/8" of 3/32" chain. The Shimano BMX style you linked to is available in either, that specific model linked is 3/32". If you are reusing an old multispeed chain, you will need 3/32". If from a single speed, more likely 1/8" but not guaranteed.
 
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Thanks again knightscape. Bullet dodged. I also didn't know (surprise) that more than 1 type of bicycle chain exists. I broke out the caliper again and measured the crank sprocket and the freewheel sprockets. Once again, they're different. Yep, 3/32" for the mountain bike freewheel, 1/8" for the Del Mar crank. Explains why when I tried using a 1/8" chain that it popped like **** and kept falling off.

Another step up on that learning curve!
 
If it were me :
I'd convert to a 3 piece crank , leave the rears alone and just run a single speed set up .
That way when you find that cranking your 45 - 65 lb bike up a hill is a bit of a pain with a single speed ------ You can convert it back to a shift'r by adding a longer chain and the derailleur.....
All sarcasm aside , you will at some point have to peddle the darn thing, and it's usually a long trip .
I'd keep the gears...
 
I think the 3 piece crank is going to happen. It needs to be wider so the pedals can clear the exhaust anyways.

Sorry guys, it's staying as a single speed cruiser. I don't want it cluttered up with more crap than it needs.

I got my single speed freewheel from a great little bike shop here in Charleston. It's an 18t as opposed to the 19t the Del Mar had, so a very small increase in pedal effort, but overall I'm very happy with it.

To put some myths to rest:
-I'm not going to rely on the bike to get me anywhere important with a deadline. It's purely recreational.
-There are hills and grades here in the Charleston area.
-The little 48cc needs no help getting up them.
-The bike probably weighs all of 40 lbs.
-I am thoroughly impressed with the bike I have built here, exactly the way I built it, and wouldn't change anything.
-If, for whatever reason, I find myself needing more gears in the future, I can always install them later.
-If I run out of gas, I carry an aluminum bottle with another 1/2L of fuel.
 
Bob Saget... I forgot to add a picture.

The yellowed plastic crap is gone now. Much cleaner without it.
 

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