Jared's 1982 CM450C Cafe Project

cxman said:
the frame has been welded and ground down on both side in 2 spots each side

near where you put the swingarm if those welds crystallized and or were ground down to much

then the frame is essentially been cut in half

i would consider jack plating the sides of the frame if not making a wrap around stiffener

I have (3) stiffeners on each side going form the outside of the swing arm pivot to the engine mounts and the rear shock upper mount. They will all be welded to the 1/4" foot control brackets in the last picture above. Should trasfer the shear and torsion loads from the swing arm to all the appropriate strong points on the chassis and engine. I'll post pictures of that installation when we get to that point.
 
Watching. Lots of ingenuity here. You are clearly not done with the frame so it makes no sense to critique that yet. I like it so far.

Are you going to try to match the VFR rear wheel? I love the five spokes, never have been a fan of three spokes.
 
yeah the frame aint done but you will need some perimeter structure some beams or a lattice work set of structural outer members tying in the outside of the swinger pivot,as well as the motor mounts of course up to the bacbone steering head area .
longer swinger = much higher loads in the normal direction ie basically the lever of the swingarm is longer so the force trying to get the wheels out of line is a good bit more.the frame as stock had quite a bit of integrated structure to fight this force,the oem ugly ass rear frame that looped around so hideously and triangled into the upper rear backbone ,actually served a very important part of this duty,along with the cast alloy mounts.......compounding that issue is now the swinger pivot has huge forces in the more or less vertical plane wheras the stock twin shock lashup had very very little vertical loads at the swinger pivot.
basically if you could have layed the bike frame on its side supported at the contact patch area of the wheels and start stacking weight over the swinger pivot then you can see cleasrly that the frame wants to bend in the middle.same test with the ugly looping rear frame removed ,or just cut loose from wher it ties in at the backbone, would be quite alarming a rubber band is what it would be like in comparison.
you can hopefully see that a longer swingarm would be resulting in more deflection in this "test"
having the overall frame centerarea weaker or more springy than it was originally is well a mistake.. but then you add in the constant up to well over a thousand pounds of totally new vertical forces see sawing up and down at the pivot spindle (stock vertical loads were proly a cupl hundred pounds max if that),whilst it is trying to bend sideways at the same time and you might understand why you need more than just side plates
the single forward mounted shock,along with the longer lever is the culprit directing highly multiplied suspension forces in a vertical plane where there was virtually none before,right smack dab in the middle of your modding
 
DohcBikes said:
Watching. Lots of ingenuity here. You are clearly not done with the frame so it makes no sense to critique that yet. I like it so far.

Are you going to try to match the VFR rear wheel? I love the five spokes, never have been a fan of three spokes.

Thanks for the feedback DOHCBikes! I made more progress on the frame and chassis stiffeners this past weekend, so you'll at least know my direction. Let me know if you have any questions. Look fowrard to hearing your thoughts.

I'm probably going to keep the rear VFR wheel, I didn't really like how the 3-spoke NT650 Hawk wheel looked. The front wheel (2006 cbr600rr) should be fine, I'm probably not going to switch it out. I do like the 5-spokes much better, but it's not fitting into the budget so far. Plus I thin the front rotors should disguise the 3-spokes, or at least break up any obviousness from it.
 
xb33bsa said:
yeah the frame aint done but you will need some perimeter structure some beams or a lattice work set of structural outer members tying in the outside of the swinger pivot,as well as the motor mounts of course up to the bacbone steering head area .
longer swinger = much higher loads in the normal direction ie basically the lever of the swingarm is longer so the force trying to get the wheels out of line is a good bit more.the frame as stock had quite a bit of integrated structure to fight this force,the oem ugly ass rear frame that looped around so hideously and triangled into the upper rear backbone ,actually served a very important part of this duty,along with the cast alloy mounts.......compounding that issue is now the swinger pivot has huge forces in the more or less vertical plane wheras the stock twin shock lashup had very very little vertical loads at the swinger pivot.
basically if you could have layed the bike frame on its side supported at the contact patch area of the wheels and start stacking weight over the swinger pivot then you can see cleasrly that the frame wants to bend in the middle.same test with the ugly looping rear frame removed ,or just cut loose from wher it ties in at the backbone, would be quite alarming a rubber band is what it would be like in comparison.
you can hopefully see that a longer swingarm would be resulting in more deflection in this "test"
having the overall frame centerarea weaker or more springy than it was originally is well a mistake.. but then you add in the constant up to well over a thousand pounds of totally new vertical forces see sawing up and down at the pivot spindle (stock vertical loads were proly a cupl hundred pounds max if that),whilst it is trying to bend sideways at the same time and you might understand why you need more than just side plates
the single forward mounted shock,along with the longer lever is the culprit directing highly multiplied suspension forces in a vertical plane where there was virtually none before,right smack dab in the middle of your modding

Thanks for your feedback XB33BSA, all very good points. I did spend time last couple saturdays looking over the chassis and different ways to strengthen everything. It helps knowing that I won't be very hard on this bike, I have another motorcycle that I can go fast on and beat up.

There is a LOT of things going on around the swinger pivot that I'm trying to resolve. The right side has the rear break master cylinder and foot controls to deal with, and the left side has the chain to dodge with all those supports. Thats the main reason the underneath support on the left side was a chunk of steel flat stock (1/4" x 1") instead of 3/4" tubing like all the others. The left side also has a short tube going into the longer, more vertical tube next to it. Admitedly not the ideal situation, since you really want those forces directed to the centerline of the swinger pivot. But with the chain going right behind all of that, this was really the only option. Also added some stiffener plates on all along both sides the swinger pivot shaft housing.

Thanks again and looking forward to more feedback!
 

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Here some progress pictures of the subframe cross-bracing for the seat. It was pretty tricky with the coping and the fishmouths, but I got the hang of it after a few trys. I have the advantage of the local steel shops having a "minimum order", so I have about 20-30" feet of tubing left over!
 

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The CM based builds are the ones surprising me the most lately. Really like the way you're going with this can't wait to see more!
 
I took another long break from the project this spring and summer, but here are a few progress pics of finishing up the subframe and getting the mold for the fiberglass seat. On the left side, the chain does have full clearance for the full swingarm travel. I had to do some special fabrication for the rear-set supports on that side, but figured it out after some trial and error. I'll get some pics showing the chain location relative to the rearset supports.
 

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Jared, this is a great looking bike I love it you are doing awesome work but the seat hump doesn't suit the bike imho. Not that it matters because as long as you like it that is all that matters. It just seems like you are trying to utilize an old school cafe racer seat hump on a modern take on a cafe racer. Please don't be offended that's just my opinion.
 
johnu said:
Jared, this is a great looking bike I love it you are doing awesome work but the seat hump doesn't suit the bike imho. Not that it matters because as long as you like it that is all that matters. It just seems like you are trying to utilize an old school cafe racer seat hump on a modern take on a cafe racer. Please don't be offended that's just my opinion.

Not offended at all, I always appreciate feedback and the free-flow of thoughts, especially in this strange intersection of art and motorcycles! I was using the article from BIke Exif (http://www.bikeexif.com/build-cafe-racer) as a guide for the visual continuity of the bike as a whole, and specifically, the seat as it relates to the rest of the bike. So this classic cafe seat on the modern take of the cafe racer is actually what I was going for. But to be completely honest, this particular mold was destoyed when I made my first attempt at laying the fiberglass and epoxy resin. So I am actually in the process of re-doing the whole thing... :eek: :mad: :'(

So are you saying that a modernized cafe racer like this should have some type of modern, new, edgy seat style? Maybe you could send me a few picutres of examples over private message? I'm down to consider anything, as I know it will just help me to have the most conviction for the design I finally choose.
 
The shape of the hump is a little funky to me, but this whole thing is looking pretty badass. Carry right on sir.
 
I have to agree, I think something a bit more streamlined would look great on this thing. Maybe squashed down vertically a bit would give some nicer proportions. Overall the bike looks great though.

When glassing over foam, I always use clear packing tape to cover the foam first, overlapping each coarse about 1/8"-1/4". Mold release wax from Meguire's or the like also helps your finished product to pop right off the mold allowing you to keep the plug.


Sent from my iPhone using DO THE TON
 
Hey Jared, if it were me I would use the look of this Honda NSR125 tail as my inspiration http://www.airtech-streamlining.com/hondaz/RS1252004-06.htm and then go from there. Take away the sharp lines and replace with larger rads. Kind of like a scaled down Suzuki srad GSX 750 (not sure what year). Glad you didn't get mad at me ;D It really is an awesome bike you're building :)
 
I finished sanding the new mold last night, here's a picture. I was trying to mimick the gradual downward curvature of the gas tank, and make it more streamlined. I am still wanting a seat that is "cafe-ish", and I didn't think any sharp lines or edges would work with the existing "bulb-like" tank. Thoughts?
 

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That looks better, I think you might be right trying to get the shape to 'flow' with the tank. Interesting work you are doing, I always thought I would like to convert one of these myself.
 
you are sure adding tubes and stuff but i think it still has a well oiled hinge in the middle its probably fine for bar hopping but be carreful if you ride hard
the tail looks sweet
i think you might want to check the clearance of the shock spring to the crossed tubes,which i really like but as the wheel comes up every bit of movement brings the shock spring closer to those tubes
taking the spring off the shock is what you should have done before fabrication but its not to late
you cant redo a rear suspension with the springs on the shocks anyway,because you dont know how far the wheel comes up ,see
 
Thanks for the thoughts XB33bsa. Not sure what you mean about the "well oiled hinge in the middle", could you please explain? You are right about it generally being a bar-hopping bike, with all the custom frame and suspension work, I'm definitely not expecting high performance out of it.

I did do the calculations on if the rear spring would stay clear of the subframe tubes... Using the full stroke distance of the rear shock (50mm), I was able to find the arc length and total swing of the rear wheel when the shock is fully compressed. There should be about 1/2" clearance on either side at that condition. It's not a ton, but it's enough for me.

The other tubes are mainly for outboard supports for the swing arm and for the rearsets. This swing arm (NT650 Hawk) was originally designed with all it's supports on the outside, so I was trying to address as much of that as possible.

Thanks again for the thoughts! Hope you stay tuned for the rest of my progress ;D ;D
 
hinge its just that what you have done the tubing work which looks fantasic by the way ,please dont ruin it with a flux core wire feed \either use a mig tig oxy ace it
hinge the tubing didnt really do much at all to help in the i guess lateral direction
the swinger has a ;lot more leverage than stock i the direction of bending in the middle like if you pushed on ther swinger bolt and kept the wheels from sliding that direction ,it neerds some way to be stiffer but its almost impossible without large outboard structure al the way up to the steering head
all that said it wont be an issue putting around town ..if you get the inkling to do so,just be wary and careful pushing it hard through bumpy turns at speed,thats all
 
Jared, with a degree in mechanical engineering I would have thought that the bikes ability to function safely, properly and better then stock would have been your goals. I don't see anything in your thread regarding the bikes geometry and I, like xb33bsa, have real doubts as to whether your mono shock/framing systems are safe. I just don't see the point in putting time and money into something that isn't usable in real world application, but it's not my bike or thread so I'll bow out.
 
xb33bsa said:
hinge its just that what you have done the tubing work which looks fantasic by the way ,please dont ruin it with a flux core wire feed \either use a mig tig oxy ace it
hinge the tubing didnt really do much at all to help in the i guess lateral direction
the swinger has a ;lot more leverage than stock i the direction of bending in the middle like if you pushed on ther swinger bolt and kept the wheels from sliding that direction ,it neerds some way to be stiffer but its almost impossible without large outboard structure al the way up to the steering head
all that said it wont be an issue putting around town ..if you get the inkling to do so,just be wary and careful pushing it hard through bumpy turns at speed,thats all

Good point with the flux core wire feed, I was just using it to tack the tubes in place to finish the geometry in my garage. Since the fiberglass seat is pretty much done now, I will be taking the subframe to a welding shop to have everything professionally welded up. I don't want to be worried about welds that I did while riding!

Bracing the swinger laterally from the outboard sides was defintely a concern. I beefed up the swinger bolt housing inside the frame big time, which should help a lot. The only places I could transfer loads from the outsides of the swinger bolt were the two engine bolt points (one above the rearsets and one below, tough to see the one below) and to the rear shock top mount. But you're right, the outsides of the swinger pivot point needs all the help it can get.

The OEM swinger was 508mm long, and the Hawk NT 650 swinger is 545mm, so about 7% longer. It will have more leverage, but the main difference I found in my research was that the aluminum single-sided swingarm AND the new forks (CBR600rr) will transfer more loads to the steel frame on account of them being much stiffer than OEM forks and swingarm. We will see how it holds up and of course I will be taking it easy when riding, but short of paying an engineering consulting firm $5k to $10k for a full FEA analysis, there's no way of knowing for sure.
 
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