CR500 , 2 stroke hardtail chopper project

[plagrone]

CR500 , 2 stroke hardtail chopper project

The great part about this thread is that we all agree that the biggest concern is what happens when my 8 foot long chopper sets down a wheelie.

Bahahaha
I think I may put this in my signature.

 

[irk miller]

The force is being transferred to the bottom part of the frame because there is so much caster on a chopper. The force is running straight down that down tube that the tank is on into that bottom catenary. Because the endpoints of that catenary are essentially your wheels, the bottom section will likely flex. That may not be a big deal. Have you tested the frame at that 120 degree angle to check for flex? You ran a tube from that 120 degree focus which hopefully will counter the flex, but I think the swing arm section has a really good chance of bending at that same point. If it were me, I would have someone hold the bike while I jumped up and down where the seat goes to see how much it flexes. I could be wrong, but it looks like force will be applied to the wrong side of your arcs.

I hope the geometry works, because it looks great. And yes, my biggest concern is what happens when your 8 foot long chopper sets down a wheelie. I can't wait for the video.

 

[Beeweldmut]

CR500 , 2 stroke hardtail chopper project

The force is being transferred to the bottom part of the frame because there is so much caster on a chopper. The force is running straight down that down tube that the tank is on into that bottom catenary. Because the endpoints of that catenary are essentially your wheels, the bottom section will likely flex. That may not be a big deal. Have you tested the frame at that 120 degree angle to check for flex? You ran a tube from that 120 degree focus which hopefully will counter the flex, but I think the swing arm section has a really good chance of bending at that same point. If it were me, I would have someone hold the bike while I jumped up and down where the seat goes to see how much it flexes. I could be wrong, but it looks like force will be applied to the wrong side of your arcs.

I hope the geometry works, because it looks great. And yes, my biggest concern is what happens when your 8 foot long chopper sets down a wheelie. I can't wait for the video.

Sorry I wasn't trying to be condescending in my reply. My apologies.


The way I wrap my head around it, I have opposing arches on top and bottom and both are curved in as well, so that makes them compound from all angles right? A force from any direction will be absorbed by a curve opposite of it.

I know triangulating makes things stronger, and that's why I put one in the center of the bike. All sides of that triangle extend to the stressed parts of the bike. It's not just a curved frame with a strut in the middle.

I'm willing to accept shortcomings, but other than a chopper geometry that is not going to be real aggressive in corners, I don't see a lot of problems with my frame. I do however enjoy an intelligent difference of opinion, and boobies. I like boobies more.

 

[50gary]

This is more fun than reading about bike building. This bike has become the Rorschach ink blot test of bikes. BTW I do build bike frames and racing kart frames and guitars and one house. This bike has the axles as fixed points, do not be fooled into thinking they are not fixed points because it is mobile, more than one can say about that static St. Louis arch inverted or otherwise.
Cheers, 50gary

 

[irk miller]

Haha. I like boobies more too. I am not for triangulation in your design. My question was just the potential for flex, while also trying to make sense of why people are questioning the geometry. I don't think flex would necessarily be bad for you as long as it doesn't stress your welds. I was also responding to your "am I missing something" comment before and offering potential pitfalls. I don't want to insult your knowledge here . I just overlooked the action of my swing arm when trying to retrofit hayabusa rear sets to my CB and someone pointed it out. It was a pretty boneheaded thing to do.

 

[irk miller]

This bike has the axles as fixed points, do not be fooled into thinking they are not fixed points because it is mobile, more than one can say about that static St. Louis arch inverted or otherwise.
Cheers, 50gary

Mobile has nothing to do with it. Axles, frames, and forks twist and flex and there are shock absorbers on the front. So they are definitely not static.

 

[Beeweldmut]

CR500 , 2 stroke hardtail chopper project

This bike has the axles as fixed points,
Cheers, 50gary

Yeah I was cussing myself and that fixed axle when I had to get a bigger sprocket to tighten my chain. Which did work.

 

[50gary]

I noticed way back that there were no rear axle adjustments but bit my tongue and didn't post about it. Not (at the time) wanting to appear the critic, but yeah.
The frame is fine. You only weigh 132# you should be a cyclist, you could be a great climber.
Cheers, 50gary

 

[Beeweldmut]

CR500 , 2 stroke hardtail chopper project

I noticed way back that there were no rear axle adjustments but bit my tongue and didn't post about it. Not (at the time) wanting to appear the critic, but yeah.
The frame is fine. You only weigh 132# you should be a cyclist, you could be a great climber.
Cheers, 50gary

Yeah the spring tensioner is great for actively keeping tension, but still need a way to adjust the sprocket for the chain length.

 

[Keiff Hardcore]

i dont see any problem with this frame.

it IS NOT a dirt bike anymore, so it doesnt need to be strong enough to take the forces involved in 10+ft jumps.

 

[Walms]

CR500 , 2 stroke hardtail chopper project

so this, basically, will be the bikes geometry?

Sorry, just trying to figure out where ass, hands and feet are going.

Maybe Mlinder can run this model through FEA, either that or forward it to me and I can. It would give you a better understanding of what we are talking about.

 

[Keiff Hardcore]

I must be a smart ass.

 

[Cafe Mike]

I'm not gonna be happy unless you add some more triangle. I have a fever..... And the only prescription is more triangles...... Ba ding....
With age comes a cage. And it will fend off the frame issues....

 

[Walms]

CR500 , 2 stroke hardtail chopper project

I must be a smart ass.

Dude, move your circle to the right!

 

[Beeweldmut]

CR500 , 2 stroke hardtail chopper project

Maybe Mlinder can run this model through FEA, either that or forward it to me and I can. It would give you a better understanding of what we are talking about.

That would be cool.

 

[SilkySmooth750]

Oh Man, this thread is amazing! All of the back and forth and the cool bike. Totally entertaining! I'm super stoked to see the finished project too! I might have joined late, but I'm all caught up!

 

[hillsy]

All you need to do now is put a car tyre on the back so people can totally flip out and tell you how it will absolutely kill you even before you ride it.

 

[Beeweldmut]

CR500 , 2 stroke hardtail chopper project

Meek I've got plenty to do on the bike and things to fix.. But I took it for a timid test ride today and took some photos. Video coming

 

[Beeweldmut]

CR500 , 2 stroke hardtail chopper project

..

 

[Beeweldmut]

CR500 , 2 stroke hardtail chopper project

That's girl #4 in the oven and #3,#2 and #1 riding 3up on a solo seat.