Beeweldmut
Been Around the Block
CR500 , 2 stroke hardtail chopper project
Damn that is like a boss.
Damn that is like a boss.
CR500 , 2 stroke hardtail chopper project
- Thread starter Beeweldmut
- Start date
Beeweldmut
Been Around the Block
combustioncafe
Active Member
What an awesome project. The picture of your seat caught my eye, and I ended up reading the whole thread. I'm glad to see a kind of outside the box chopper-out-of-a-dirtbike on a mostly cafe racer forum. It's nice to see a lot of variety of cafes, bobbers, choppers, factory restorations, frankenstiens, whatever - as long as it has 2 wheels and you got your hands dirty instead of forking over cash to ride it. While I do love a factory restoration, I love something like this even more - something different/unusual, even your critics call it heresy. Even if it's not your style, your critics should appreciate the imagination, effort and balls it takes to have such an idea and follow it through.
After I finish my next two bikes I may have an extra engine laying around, and my hope is to use it to build an hardtail bike out of used parts... what you've done here is great for inspiration. So thank you for posting.
After I finish my next two bikes I may have an extra engine laying around, and my hope is to use it to build an hardtail bike out of used parts... what you've done here is great for inspiration. So thank you for posting.
Beeweldmut
Been Around the Block
CR500 , 2 stroke hardtail chopper project
Thanks I appreciate your encouragement. After a few weeks on this hardtail I might encourage you to not build a hardtail.
Thanks I appreciate your encouragement. After a few weeks on this hardtail I might encourage you to not build a hardtail.
combustioncafe
Active Member
Re: CR500 , 2 stroke hardtail chopper project
By the time I get around to it, I'll have at least 3 other bikes in the stable. Comfort would not be a main concern. A hard tail bike would be an occasional Saturday morning rider at the most for me. ;D
Beeweldmut said:Thanks I appreciate your encouragement. After a few weeks on this hardtail I might encourage you to not build a hardtail.
By the time I get around to it, I'll have at least 3 other bikes in the stable. Comfort would not be a main concern. A hard tail bike would be an occasional Saturday morning rider at the most for me. ;D
Beeweldmut
Been Around the Block
CR500 , 2 stroke hardtail chopper project
Yeah I'm kind of In the same boat. With 4 girls under 6 and 4 businesses to run I don't really have time for all day rides anyway. I'm just looking for some quick, cheap thrills out of a motorcycle.
combustioncafe said:
Yeah I'm kind of In the same boat. With 4 girls under 6 and 4 businesses to run I don't really have time for all day rides anyway. I'm just looking for some quick, cheap thrills out of a motorcycle.
Beeweldmut
Been Around the Block
CR500 , 2 stroke hardtail chopper project
I've raced and ridden mostly 2strokes including a street legal HRC spec NSR250 and a Aprilia SR50 that could hold the front wheel of the ground until 40mph and topped out at 80. 2strokes on the street is like sex without a rubber, it just feels better.
burnin that bean oil, such a great smell.cafe mike said:
I've raced and ridden mostly 2strokes including a street legal HRC spec NSR250 and a Aprilia SR50 that could hold the front wheel of the ground until 40mph and topped out at 80. 2strokes on the street is like sex without a rubber, it just feels better.
Keiff Hardcore
Loves anything that burns oil
Re: CR500 , 2 stroke hardtail chopper project
if this was a 4 stoke dirtbike build, it certainly would not be as cool.
i REALLY want to take an old Maico and turn it into a tracker. they are some of the meanest 2 stroke dirtbikes, and they have that "vintage" appeal to them.
indeed.Beeweldmut said:
if this was a 4 stoke dirtbike build, it certainly would not be as cool.
i REALLY want to take an old Maico and turn it into a tracker. they are some of the meanest 2 stroke dirtbikes, and they have that "vintage" appeal to them.
Walms
Been Around the Block
CR500 , 2 stroke hardtail chopper project
You will want to beef the rear frame up a bit if you haven't done so already. With parallel tubes and no triangulation, it's going to fold up like a cheap suit on the first good impact of the rear wheel.
A quick and dirty way to determine what sort of weight you'd need to support, add your weight, the bikes weight, then double it for an impact load.
As an example, doing a 3rd gear wheelie then hitting a pot hole.
You will want to beef the rear frame up a bit if you haven't done so already. With parallel tubes and no triangulation, it's going to fold up like a cheap suit on the first good impact of the rear wheel.
A quick and dirty way to determine what sort of weight you'd need to support, add your weight, the bikes weight, then double it for an impact load.
As an example, doing a 3rd gear wheelie then hitting a pot hole.
AW: CR500 , 2 stroke hardtail chopper project
this is my 2nd stroke dream (after my RD)to restomod that husquarna cr 250...extremely rare extremely light.found a guy who just sold that one for 1500 euros....$$$
this is my 2nd stroke dream (after my RD)to restomod that husquarna cr 250...extremely rare extremely light.found a guy who just sold that one for 1500 euros....$$$
Beeweldmut
Been Around the Block
CR500 , 2 stroke hardtail chopper project
No it's been decided that a triangle is the only structure capable of supporting weight. Parabolic arches that are triangulated and gusseted are not capable. Must use straight lines and 90° angles or the bike will explode.
cafe mike said:
No it's been decided that a triangle is the only structure capable of supporting weight. Parabolic arches that are triangulated and gusseted are not capable. Must use straight lines and 90° angles or the bike will explode.
Beeweldmut
Been Around the Block
CR500 , 2 stroke hardtail chopper project
thats got a sexy looking cylinder headRyan Stecken said:
this is my 2nd stroke dream (after my RD)to restomod that husquarna cr 250...extremely rare extremely light.found a guy who just sold that one for 1500 euros....$$$
Beeweldmut
Been Around the Block
CR500 , 2 stroke hardtail chopper project
I truly know y'all are trying to be helpful and I appreciate that. But what I don't understand is that y'all all seem like you know your stuff and are intelligent, but for some reason only see parallel lines on the tail section. If I had 2 horizontal straight tubes then yes I would agree because that forms a square. However there is not a single parallel or even a line (other than the backbone). It's a curve and curves are have different strength characteristics than a straight line does. Am I missing something?
Walms said:You will want to beef the rear frame up a bit if you haven't done so already. With parallel tubes and no triangulation, it's going to fold up like a cheap suit on the first good impact of the rear wheel.
A quick and dirty way to determine what sort of weight you'd need to support, add your weight, the bikes weight, then double it for an impact load.
As an example, doing a 3rd gear wheelie then hitting a pot hole.
I truly know y'all are trying to be helpful and I appreciate that. But what I don't understand is that y'all all seem like you know your stuff and are intelligent, but for some reason only see parallel lines on the tail section. If I had 2 horizontal straight tubes then yes I would agree because that forms a square. However there is not a single parallel or even a line (other than the backbone). It's a curve and curves are have different strength characteristics than a straight line does. Am I missing something?
I think the concern (at least from my perspective) is that your curved line is a catenary (hyperbolic cosine curve). The caveat with a catenary, is that it's strength is essentially sprung between two fixed points while it's load is uniform across the curve. A suspension bridge is an a example of a catenary. The St. Louis Gateway arch is an inverted catenary. In either example, the two endpoints of the curve are fixed points. The most common kilns I build are sprung arch kilns with a catenary as their roof. Any outward flex on the sidewall of the kiln, and the roof wants to cave in. It's paramount that the endpoints of the arch are fixed to give the arc it's strength. By nature a motorcycle frame doesn't have those anchors. Also in your design, you have introduced a 90 degree angle at the midpoint of the arc that creates the whole bottom of your frame. You designed a second arc over the rear axle that works counter to the arc at the base of the frame, but for that arc to strengthen the bottom arc, it would need to produce a biconvex shape. The tension between two arcs in a biconvex shape are what give them their strength. Your design may very well work, but I am not totally confident. Most point to triangulation to counter.
plagrone
Coast to Coast
CR500 , 2 stroke hardtail chopper project
I have zero experience building frames, but I work on jets and fiddle with stuff in my free time, and like to think I have pretty good common sense when it comes to stuff like this... If it was me, I would put down tubes on either side of that first cross member in front of the tire to reinforce the long arc of the tail, however that kind of seems superfluous, but in building a custom frame I would lean towards over-building. Then again, I've never built a custom frame.
With that said, I think it will be fine.
I LOVE your build. It's simply batshit and awesome. Hope you make it to and do well at the show.
MORE PICTURES plz
I have zero experience building frames, but I work on jets and fiddle with stuff in my free time, and like to think I have pretty good common sense when it comes to stuff like this... If it was me, I would put down tubes on either side of that first cross member in front of the tire to reinforce the long arc of the tail, however that kind of seems superfluous, but in building a custom frame I would lean towards over-building. Then again, I've never built a custom frame.
With that said, I think it will be fine.
I LOVE your build. It's simply batshit and awesome. Hope you make it to and do well at the show.
MORE PICTURES plz
Beeweldmut
Been Around the Block
CR500 , 2 stroke hardtail chopper project
More photos coming soon. I'm. Glad you like the bike and hope your not offended if I disagree with your suggestion. If I connected the 2 arches in the middle the upper arch would just push down the lower arch and neither would be effective at their jobs.
plagrone said:
More photos coming soon. I'm. Glad you like the bike and hope your not offended if I disagree with your suggestion. If I connected the 2 arches in the middle the upper arch would just push down the lower arch and neither would be effective at their jobs.
Beeweldmut
Been Around the Block
CR500 , 2 stroke hardtail chopper project
Deviant it sounds like you are implying that the motorcycle is supported by the engine cradle and not the back bone. I think you got it backwards. The lower section of a frame just cradles the engine and keeps the frame from twisting. The weight is supported by the line in between the neck and the rear axle. Usually called the backbone. 90% of sports bikes don't even have a lower frame anymore. So I wouldn't look at that frame to support any weight. Which of course the engine weighs about 65lbs, the frame weighs about 40 and I weigh about 132 so it's not much weight anyway.
The 90° angle you refer to is more like 120° and every bike has a swingarm angle of some kind. Mine happens to be less than most bikes since it is a chopper, but that angle effects the weight on the front wheel and not it's ability to support weight.
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.
deviant said:
Deviant it sounds like you are implying that the motorcycle is supported by the engine cradle and not the back bone. I think you got it backwards. The lower section of a frame just cradles the engine and keeps the frame from twisting. The weight is supported by the line in between the neck and the rear axle. Usually called the backbone. 90% of sports bikes don't even have a lower frame anymore. So I wouldn't look at that frame to support any weight. Which of course the engine weighs about 65lbs, the frame weighs about 40 and I weigh about 132 so it's not much weight anyway.
The 90° angle you refer to is more like 120° and every bike has a swingarm angle of some kind. Mine happens to be less than most bikes since it is a chopper, but that angle effects the weight on the front wheel and not it's ability to support weight.
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.
