Schoolproject: building a cruiserbike

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UnDerzon3

UnDerzon3

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May 8, 2011
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Östhammar, Sweden
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Hi
My name's Rasmus. An 18 year old guy from Sweden which is about to start a project in school. My idea is to build a cruiser bike from scratch. I haven't really decided how the design of the frame will be but i'm working on it. What I do know is that I'll be using 1,5" tubes for the entire bikeframe and I've also been thinking about puting a 120mm wide motorcycle wheel as the backwheel for my bike.
For a long time now I've been locking on the Firebikes FBR bike and I'm thinking about having that design as some sort of output for the design. I've also been thinking about puting a springer fork on the bike but that pretty much everything i've decided so far.
I'm probaly going to start this topic by posting some ideas for the design and i'm glad if you guys could tell me what you think about things I'll be uploading here.
thats pretty much what I have to say for now, if you have any questions feel free to ask. :)
// Rasmus

this is the latest sketch of the design, tell me what you think :)
ide.jpg
 
Yep, that's Firebike allright. Good choice, 'cause it looks good. Springerfork looks o.k. too. Don't mind my personal taste, but I would reconsider the seat and sissybar. A nice cruisersaddle could give the bike a less massive look on its backside. But it's up to you to decide. Good luck and have fun, building it.
 
I sure wish I had the wherewithall to build frames. I like the shape, and I think a few rollers to guide the chain along with the frame, so it follows the lines of the frame, would look good.
 
Frame is looking good. I'm not liking the sissy bar. I think with 1.5" tube your springer fork will look "dinky." Why don't you build your own springer fork with some thicker tubing, say 1." I would also rake the front end some, cause that will look better and your foot won't scrape the front tire when cornering. Or just move the bottom bracket shell back. Keep us updated.
 
glad to hear that you guys liked the framedesign. I've looked at your comments and i've redesigned the last sketch I made and acording to your thoughts the bike would look a little like this...
ide2.jpg

i've replaced the springerfork with a triplefork and tilted that a bit. And i've changed the seat to a regular cruisersaddle. Hope you guys like it even more this time :)

//Rasmus
 
when i first saw design 2, i thought the rear was suspended, pivoting where it mounts to top tube. spring could go on the non-drive side at the bottom, opposite the chain, seat would move with the swingarm. were you thinking that too? even as a hardtail it looks pretty cool. not sure if a radial-spoked rear rim is up to the stress, but as a bicycle-drawing-person myself, they are much easier to draw.
 
X-RAY said:
when i first saw design 2, i thought the rear was suspended, pivoting where it mounts to top tube. spring could go on the non-drive side at the bottom, opposite the chain, seat would move with the swingarm. were you thinking that too? even as a hardtail it looks pretty cool. not sure if a radial-spoked rear rim is up to the stress, but as a bicycle-drawing-person myself, they are much easier to draw.
Click to expand...

the saddle's going to be mounted on the top tube and it ain't going to move with the swingarm.
With my first design where i had the seat with the sissybar I kind of thought that the sissybar was going to be some kind of support for the rear but now i probably gonna stick with some sort of cruisersaddle
hope it was some sort of answear to you question

// Rasmus
 
Hey Rasmus,
I think, the bike looks much better now. Wildcat mentioned a chainguide/-spanner and I agree with him. If your chain has a length of almost 2 regular chains, it's wise to consider some sort of tensioningsystem. With mine, I used a rollerskatewheel. And last, but not least: build it, following your own ideas. Have fun, dude. :mrgreen:
 
wimpy said:
Hey Rasmus,
I think, the bike looks much better now. Wildcat mentioned a chainguide/-spanner and I agree with him. If your chain has a length of almost 2 regular chains, it's wise to consider some sort of tensioningsystem. With mine, I used a rollerskatewheel. And last, but not least: build it, following your own ideas. Have fun, dude. :mrgreen:
Click to expand...

Hi It's fun to hear that you like it :)
i will consider the chainguiding but first things first, the project is really "only" the building of the frame. I have a timelimit and to be sure to not surpass that time i set the project to only be the framebuild. The rest of the build is gonna be something i will have to deal with later :)

//Rasmus
 
Does your design intent match your fabrication abilities?
Using 1.5" tubing for the chain/seat stays is problematic without some more design work.
 
c.p.odom said:
Does your design intent match your fabrication abilities?
Using 1.5" tubing for the chain/seat stays is problematic without some more design work.
Click to expand...
God im lucky i can change a saddle :lol:
 
Your concept sketch is a long ways from having a design. Cantilevered single stays are fine but it will be best if welded at two points and made from thick steel, your sketch allows for that. But from that point the stays will have to bend outward considerable to clear the tire and chain, they will also be rotated to give the desired curve that you show, as you rotate them they lose the inside curvature, this is where "Problematic" comes in. There are no dropouts shown in this sketch, you still have to keep the rear end around 110-120mm while having to deal with three inches of tubing width. fortunately crank clearance is not an issue with the bottom bracket being far forward.
 
c.p.odom said:
Your concept sketch is a long ways from having a design. Cantilevered single stays are fine but it will be best if welded at two points and made from thick steel, your sketch allows for that. But from that point the stays will have to bend outward considerable to clear the tire and chain, they will also be rotated to give the desired curve that you show, as you rotate them they lose the inside curvature, this is where "Problematic" comes in. There are no dropouts shown in this sketch, you still have to keep the rear end around 110-120mm while having to deal with three inches of tubing width. fortunately crank clearance is not an issue with the bottom bracket being far forward.
Click to expand...

ok now i feel like i have a little better understanding of what you're talking about. I've been thinking about the rear of the frame a lot, specially about that i will have to bend the stays so much outward. After all this thinking I've more or less decided to build something similar to what this sketch's showing just in order to be able to fit in the 120 mm wide reartire...
(which i maybe will change for a 160 mm tire instead ^^)

Hope you will be able to understand the sketch :)
upp.jpg


// Rasmus
 
This is doable, I would call it a workaround as it does not keep to your original design intent. Try to avoid adding that kind of angular fabrication to a design that is based on curves. Instead try using two short curved pieces of tubing or even better one U shaped tube that wraps around and the stays attach to it.

Now my personal opinion on the forks:
Do not use the common triple crown fork setup. I find them to be cheap and tacky wannabe copies of motorcycle parts. Your building a bicycle not a pedal powered motorcycle, keep the design DNA somewhat pure. It is OK to pull design ideas from many things in life but not to just copy them.
Curved frames NEED curved forks. Do not stray from the design intent just because it is easy to bolt something on.

To very loosely paraphrase Karl Von Clausewitz:
Just because something appears to be simple does not mean that it will be easy to do.
 
c.p.odom said:
This is doable, I would call it a workaround as it does not keep to your original design intent. Try to avoid adding that kind of angular fabrication to a design that is based on curves. Instead try using two short curved pieces of tubing or even better one U shaped tube that wraps around and the stays attach to it.

Now my personal opinion on the forks:
Do not use the common triple crown fork setup. I find them to be cheap and tacky wannabe copies of motorcycle parts. Your building a bicycle not a pedal powered motorcycle, keep the design DNA somewhat pure. It is OK to pull design ideas from many things in life but not to just copy them.
Curved frames NEED curved forks. Do not stray from the design intent just because it is easy to bolt something on.

To very loosely paraphrase Karl Von Clausewitz:
Just because something appears to be simple does not mean that it will be easy to do.
Click to expand...

We'll see how I will do with the forks. My nr one priority right now is to start building the frame and start looking a litte closer on what kind of rim i will be using for the reartire.
Still, thank you very much for your comments so far, they've been helpful. Hope you will follow my project :)

// Rasmus
 

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