MJPriceisright
Coast to Coast
hahahahah thanks man, turned out pretty good, just hoping it bakes well and sticks after i get it running!
new cafe build cb450
- Thread starter MJPriceisright
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MJPriceisright
Coast to Coast
BARN FIND! So I was talking today with my old man about the carbs for my bike and the possibility of swapping out for some mikunis... He then mentioned he had an old carb off a four wheeler, turns out it is a mikuni BTM? Couldn't find any other numbers on it, but doing some research looks like they come on the Yamaha warrior, which is the four stroke 350 twin if I'm not mistaken.. Would something like this work on my bike if I came across another one?
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MJPriceisright
Coast to Coast
Right on, I think I'll be leaning towards the first design, not really sure about how I like the curved bend, although I have definitely been keeping the structural strength in mind, (I'm 6 foot roughly 215). I'm currently waiting on the supermoto wheels to come, direct replacement for the cr500 swingarm, and the front Is actually a Ktm dual front disk hub laced with a 3.5" rim. Hopefully ill have updated pics sooner than later.
MJPriceisright
Coast to Coast
Yeah was thinking maybe filling the triangular section with a reinforcement plate and having the CNC shop cut out the Honda logo in it. We'll see, gotta get the vision from paper to the frame, I can see what I want for the most part in my head, but every time I am standing in front of the frame I can't quite see it.. I ordered the wheels so I can kind of fab the bike together and then make the necessary frame mods.. I don't wanna change the frame without it semi put together and then have to take two steps back when it's all pc'd and something doesn't look right.
MJPriceisright
Coast to Coast
thanks swivel for your insight, definitely wont be doing any welds until i know everything is set up and going to work as well as it looks.
Flugtechnik
My bike is not transportation, it is a respite
Yes, the second frame design looks better. At least from a seat supporting standpoint.
Where were you planning on putting the shock mounts. Honestly I have not read through the full thread so I don't know if you were planning on going mono shock or something.
The main problem with the first design is that it is not properly trussed. The piece that comes down from the back of the seat hits the main downtube at neatly a perpendicular angle. The downtube then has to react the axial load from that piece in bending rather than converting into axial loads in other directions. This isn't really a strength issue, more of a stiffness issue.
I'll draw what I'm talking about.
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Where were you planning on putting the shock mounts. Honestly I have not read through the full thread so I don't know if you were planning on going mono shock or something.
The main problem with the first design is that it is not properly trussed. The piece that comes down from the back of the seat hits the main downtube at neatly a perpendicular angle. The downtube then has to react the axial load from that piece in bending rather than converting into axial loads in other directions. This isn't really a strength issue, more of a stiffness issue.
I'll draw what I'm talking about.
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MJPriceisright
Coast to Coast
Flugtechnik said:
dang and just when i was thinking i wanted to go with the first one..
Flugtechnik
My bike is not transportation, it is a respite
This is what I was trying to describe. The applied loads I'm showing are from the shocks, assuming they are mounted there.
In the first one the downtube is being bent. Although it is probably strong enough to take the load, it is not good design practice and will reduce the stiffness of the frame which greatly affects handling.
On the second one, you would want to blend the curved lower piece of the "tail" into the main frame a little better. The solid web you have drawn will help support the curvature, even if you have some design cut into it.
Honestly, just looking at them, the first one looks like you hacked the back off and made a new tail section. The second one looks like you redesigned the tail. A significant distinction.
Just giving my input. Take it as you will.
Keep up the good work.
In the first one the downtube is being bent. Although it is probably strong enough to take the load, it is not good design practice and will reduce the stiffness of the frame which greatly affects handling.
On the second one, you would want to blend the curved lower piece of the "tail" into the main frame a little better. The solid web you have drawn will help support the curvature, even if you have some design cut into it.
Honestly, just looking at them, the first one looks like you hacked the back off and made a new tail section. The second one looks like you redesigned the tail. A significant distinction.
Just giving my input. Take it as you will.
Keep up the good work.
MJPriceisright
Coast to Coast
flug that is awesome, thanks for the rear section tear down.. are you keeping in mind the bike is going to be a rear mono shock? so nothing will be mounted to the tail section other than my rider weight. i see what your saying about the perforated web piece, but what if i did the same web piece in the first one as well? these sketches were literally just a photoshop and permanent marker job to get a feel for what i am doing with the bike, so anything can be changed, advice, you could do one and show me, anything is cool by me, i love the creative criticism.
Flugtechnik
My bike is not transportation, it is a respite
Flugtechnik said:
No I wasn't, that's why I asked. If it is just supporting your weight, the design is less critical but still important. you can then just take those pics I drew and reverse the direction of the loads. Remember, it is not just supporting your weight, but the inertial load of your body when you hit a large bump. I'm no chassis designer but I would guess you could reach 5Gs when you hit a sharp bump. So that is 500-600 lbs pushing down on each side. Depending on the geometry of the frame that can result in very large loads at the tail joints at the main frame.....upwards of 1000 lbs.
Again, the first design will work probably work as long as you make it stout enough. My day job is aircraft structural design so I tend to look for the most efficient structures, which to me, of the two, is the second.
Where were you planning on mounting the monoshock to the frame? I'm guessing just aft of the rear tank mount?
MJPriceisright
Coast to Coast
ahh sorry about that, went right past your question about the mono shock. yes running a mono shock. yeah was planning on having it right up around where the tank mount is. getting the shock here in a couple days so i will post some pictures of how that is going to look as well.. althought i have been gettin lengths of sport bike shocks and they are pretty short in comparison to the stock cr500 shock that came on this swingarm, i posted a picture of where most sport bike shocks will mount, if this is the case, im assuming i will need some good solid support coming down from that middle joint area? thanks flug this is helping a ton!
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MJPriceisright
Coast to Coast
yeah teazer that def looks nice, i like that a lot.
MJPriceisright
Coast to Coast
would it be possible to do away with that middle bar teazer removed?
It is effectively replaced by the (two) new tubes. Of course packaging may be an issue once the engine tries to slide back into place.....
A short shock could mount on a new cross tube between the two new rear downtubes as long as it's all triangulated. What i did on one conversion was to slip a length of 1"x2" chro-Mo box section tube in as a cross brace and machined a top mount that bolted in with 4 bolts in shear. There are other ways.
A short shock could mount on a new cross tube between the two new rear downtubes as long as it's all triangulated. What i did on one conversion was to slip a length of 1"x2" chro-Mo box section tube in as a cross brace and machined a top mount that bolted in with 4 bolts in shear. There are other ways.
MJPriceisright
Coast to Coast
ok im following with the cross tube.. but do the two new bars you have made come together at the top? sorry for the breakdown of questions for you, just trying to get a whole vivid idea of what your doing. thanks teaze
Flugtechnik
My bike is not transportation, it is a respite
Being an engineer I am very reluctant to give advice on something I don't really know about (unlike Swivel) so I think your questions are moving beyond my ability to answer them. Again I don't like what Teazer has drawn because he as the tail load punching sideways into the downtube without any backup. It can work if the down tube is big enough.
If you lose the stock downtube, you lose an engine mount. I have a feeling that one isn't doing a lot but you should know what you are getting into.
As for the two new down tubes coming together at the top, I would think they would have to somehow. I think you will run into carb clearance issues if you do that. Here is my frame and engine. You can see that the carbs actually sit on either side of the stock downtube.
Again, I don't really know anything about monoshock conversions, but I would want to shock load to punch as directly into the frame member under the tank as you can get it.
If you lose the stock downtube, you lose an engine mount. I have a feeling that one isn't doing a lot but you should know what you are getting into.
As for the two new down tubes coming together at the top, I would think they would have to somehow. I think you will run into carb clearance issues if you do that. Here is my frame and engine. You can see that the carbs actually sit on either side of the stock downtube.
Again, I don't really know anything about monoshock conversions, but I would want to shock load to punch as directly into the frame member under the tank as you can get it.
If you're unsure about designing for strength, there is a simple rule of thumb with a couple of extra considerations:
1.) Triangles are the strongest shape. Use them everywhere.
2.) The above holds true so long as the pressure (or tension) is being applied at the corners of the triangle and not laterally to the legs of the triangle.
3.) If pressure must be applied laterally to the leg of a triangle, it is best to brace the opposite side of the leg with an additional triangle.
Like so...
1.) Triangles are the strongest shape. Use them everywhere.
2.) The above holds true so long as the pressure (or tension) is being applied at the corners of the triangle and not laterally to the legs of the triangle.
3.) If pressure must be applied laterally to the leg of a triangle, it is best to brace the opposite side of the leg with an additional triangle.
Like so...
