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The new admins make us play nice now. But had you been here even a year ago, you鈥檇 know angry old men. There are some old forum traditions that aren鈥檛 so frowned upon, though....,

Yeah, about that.... he's been here longer than you have... 馃槃
 

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That鈥檚 because he鈥檚 right, and you鈥檙e not. Call us angry old men al you like. You ain鈥檛 hurting anyone鈥檚 feelings here. Quite honestly, no one here gives a fleeting flying fig what yours (or anyone else鈥檚) bike looks like. What we care about is how it WORKS. You made the statement that if you had placed the mount higher up no one would鈥檝e batted an eye. You are correct because that鈥檚 where it should be. Raise the front mounting point up above the rear mounting point so you get a more progressive shock compression. Even then you will be somewhat limited by the fact that the shock was designed to utilize a rising rate linkage and only has about 2 inches of total travel. But at least the rear won鈥檛 be getting all wobbly and pogo-y on whoever tries to ride it.

The new admins make us play nice now. But had you been here even a year ago, you鈥檇 know angry old men. There are some old forum traditions that aren鈥檛 so frowned upon, though....,
View attachment 105733
Fleeting flying fig - brings a tear to my eye. Actually, I spit beer.
That and you are right.
 

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Discussion Starter · #43 · (Edited)
You made the statement that if you had placed the mount higher up no one would鈥檝e batted an eye. You are correct because that鈥檚 where it should be.
That's not what I said. I said had I mounted it vertically from the swingarm to the backbone no one would have said anything. Because that's where it should be? It would take a 25~30kg/mm spring to work there while all of the stress would be concentrated on the arm brace...which is a small and lightly made piece of real estate. And even then I would have had a hard time positioning the shock in a way that would give me full swing and full stroke. Mounting it in the middle of the swingarm to the frame, "where it should be", is quite possibly the worst place to put the shock on this bike. Where I have it I have full travel and it's only going to require a 17~17.5kg/mm spring and the stress is distributed across the entire arm.

Had I put it in the middle, which is where you normally see monoshock retrofits, no one would have batted an eye and this string of conversation wouldn't be happening and the suspension wouldn't work. This idea that some people have that I stood across the shop, threw the shock at the bike, and welded it up wherever it landed is as laughable as the idea that I didn't explore other options. There's going to be some hurdles to overcome but they're going to be a lot shorter than the ones I'd be jumping if I went with a configuration that you approved of.

I see that you're using your bike as an example of why you're right and I'm not...and I would like to say that it is a very nice build, it's stunning...but it's not really easily comparable to what I'm doing. My bike is heavier and the swingarm is about 5-5.5" longer that you're dealing with (I'm estimating using my CX500's swingarm, I don't have a CB arm to measure). I'm 100% certain there are ways to make it work...probably by wrapping the arm in a large cage and using a shock from a dirtbike with a long stroke and an appropriately stiff spring, but keep in mind again bigger wheel, much longer arm, and a backbone frame...things you're not dealing with...but the way I went will work to. Whether you approve or not. Less stress on the shock, frame, and swingarm and the general area has a look I like. Alternatives would have been difficult, dangerous, or just big and unsightly. I see by your bike you're not a fan of big and unsightly

(edit because upon reflection...and walking out to the shop with a tape measure...if I wrapped the wheel in a taller brace and mounted the shock high and horizontal-ish like yours 8ball I'm not sure that I would actually have room to mount a shock that would have enough stroke to accommodate full swing. I'd only have 10" of clearance for a shock, plossibly 11" if I scrapped my plans for battery box/electronics...and I would need a touch over 4" of stroke. This frame is not open in the back like yours.)

This is not really a point I'm debating...and, as said, deaf ears. I didn't ask for advice and nothing except the seat/tank line has been finalized and while I don't mind discussing anything on the bike it will be done with civility. That goes for everyone with any interest in this build. Since sharing the last pic I've been called names, had my intelligence and character attacked, I've been threatened. I will point out that while I have certainly enjoyed the hate and maybe done a little antagonizing I have not attacked anyone. I have not insulted anyone. I have not swore at anyone. I have not demeaned anyone's character. I have not threatened anyone. If you want to talk about the bike, discuss the plans...or rather discuss the different directions my brainstorming has taken me...by all means let's talk. But if you want to be antagonized and tormented, please keep bringing the hate and anger because it gets blood hot! It's like a runner's high for me...or more like something not appropriate to discuss in mixed company...so please keep going I can feel it in my toes I'm almost there ;)...
 

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"nothing except the seat/tank line has been finalized" :LOL: Modern day priority, start with the bone line, once you got that right all the small things like suspension travel will fall into place.
 

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Discussion Starter · #45 ·
"nothing except the seat/tank line has been finalized" :LOL: Modern day priority, start with the bone line, once you got that right all the small things like suspension travel will fall into place.
Gotta make sure you can put your butt someplace that lets your hands reach the bars comfortably. Stock tank wouldn't work with the forks, have to run a skinny, tall tank, new tank doesn't work with the factory mounts so those gotta go, and when those go so do the seat rails so can't use the factory seat. Just running the forks means none of the body works. It might help to remember that this is a Honda Shadow, not a CB750.
 

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When you say "parallelogram" do you mean with the shock parallel to the arm or adjacent to it?
Such that the loads on the shock are transferred into the frame at an angle that is conducive to the shock absorber and spring operating efficiently. You want to design it to be easy as possible on the shock or you are going to make heat and heat is not good. The shock should be more in parallel alignment with the swingarm so the shock and spring is not operating at a disadvantage.

How well the suspension transfers shock forces into the frame structure is an entirely different science again.
 

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Discussion Starter · #50 ·
Such that the loads on the shock are transferred into the frame at an angle that is conducive to the shock absorber and spring operating efficiently. You want to design it to be easy as possible on the shock or you are going to make heat and heat is not good. The shock should be more in parallel alignment with the swingarm so the shock and spring is not operating at a disadvantage.

How well the suspension transfers shock forces into the frame structure is an entirely different science again.
Well, with the space and suitable locations to mount a shock with an appropriate stroke I have it where the stress on the shock and frame is as low as I can get it without, as described above, building a large cage around the rear wheel and using a shock with an enormous stroke...which I don't have room for anyway. Moving the frame mount side higher to where it's parallel with the arm would only let me use a slightly...and only slightly...lower weight spring while putting a lot more stress on that area of the frame and I wasn't confident I could brace it there to make it stronger. If, in the end, where I have it proves to be too weak a location I have clearance to brace the area from behind. Not to mention, even if I mounted the shock parallel to the arm, the travel would still be regressive. Where it's at now the first inch of wheel travel consumes 7.5mm of shock stroke, and the sixth inch consumes 9mm. If I mounted the shock parallel to the arm, because I can't move the frame side mount any further forward, the first inch of travel would still use the same 7.5mm of stroke while the sixth would consume 8.5mm.
 

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You know when you are close when the shock mounts don't need to rotate much,
and yes moving the shock mount up would allow you to use a lighter spring rate because you have reduced the bending load at the shock mount and directed the forces towards the frame, which as you say is a weak frame.
You should be bracing it from the outside, think exoskeleton not beefed up square tube backbone.
... personally I think you are exerting needless bending loads on your shock absorber to accommodate the handy bracket that already exists on the frame, and the first mistake made was completely cutting off both triangulated frame supports and turning the frame into a noodle.
 

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Discussion Starter · #52 ·
This bike was wrecked and landed pretty hard on the rear end. All the cage on the back was buggered...there was no bringing it back to begin with. Nothing to lose...and besides, trying to fix it would leave me with the same bike I started with. The idea here is something different. Again, it's easy to forget that this is not a CB750 or some other generic cookie cutter standard bike that already has the basic framework in place to be a traditional "cafe" bike.

The mounts don't actually rotate much. There's a 5~6掳 shift from static to 6" wheel travel. It's not ideal but it's pretty good for what I'm working with.
 

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... this is not a CB750 or some other generic cookie cutter standard bike that already has the basic framework in place to be a traditional "cafe" bike.
...
A traditional cafe racer would be a British motorcycle and what you call a traditional cafe cookie cutter bike is generally an abortion from what I've seen.

Good thing you live in a part of the world where you can plate anything at all for the road, or is this a race bike, or is it a lawn ornament?
 

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Discussion Starter · #55 ·
A traditional cafe racer would be a British motorcycle and what you call a traditional cafe cookie cutter bike is generally an abortion from what I've seen.
Your first point is a bit on the pedantic side but whatever...second point, however, most of what people call "cafe" bikes are meant to be artworks and not actually ridden. They don't even count as motorcycles as far as I'm concerned.

This bike will be ridden. I ride all of my bikes. I'm not an artist so if I can't ride it then what's the point?
 

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... seriously though be careful of bending that shock body on a bigger then normal bump,
watch closely for frame cracks, keep all the bearings in really good shape
and go easy throwing her into a corner. Post photos once in a while or we will assume you are um, you know.
 

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Discussion Starter · #58 ·
I think the shock will be fine, so long as it's not bottomed out it shouldn't even see any bending. This shock has a little under 2.5" of travel and I built the suspension to only use 2" of it (original shock I intended to use only had 2.25" of travel and was a little shorter...I swapped to this shock because the original was too fat). The arm is at a mechanical limit before it can overextend the shock and I'm pretty sure the same will be true before maximum compression.

There is a LONG road ahead of this bike before I get to see how it rides, though.
 

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... The arm is at a mechanical limit before it can overextend the shock and I'm pretty sure the same will be true before maximum compression.
...
You better hope that is Not the case or something is going to bend and break for sure.

Two suggestions: One: remove the spring from the shock body to design and test the travel in the swingarm and chain and brake stay. Two: learn to prepare joins for welding and how to achieve weld penetration, or you might as well put the whole thing together with hot melt glue.
 

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... and I bet dimes to donuts you bend that shock absorber on the first big bump it hits.
google up "bent shock" images if you want to see what that looks like, most of the time it will happen on a shock strut that has a coil spring over it. Coil over springs do not apply direct linear forces on the shock body, the coil spring twists and rotates on compression or extension, and that spring is going to push out of there any direction it can.
 
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