In order to run the hydro line for my rear brake inside the swing arm. I did this to my vfr. Will it make the swing arm weaker? No way to tell so don't chance a horrible death over a trick mod?
I'm no engineer...
but it stands to reason if you start drilling holes and removing metal...
it has to be weaker.
It really depends where you drill the holes as to whether or not it will be dangerous.
I have some experience with truck frames.
You never drill the top of a rail.
Can you achieve your mod that way?
Makes sense. Location for inlet/outlet are not imperative. Stock hydro line is plenty long. I will be sure to do much more research before doing this again.
Plan on not drilling the bottom either. ;)
T'would seem that you'll need a pretty big hole to pass the line + provide a grommet to protect it unless you're switching to Goodridge Micro-bore lines. I'm assuming you'll attach fittings after threading so you don't need to pass the banjo through the hole. And how do you inspect the line?
Its a complex cantilever beam on any monoshock bike, the bending stress is highest as you approach the shock mount point (presumably where you would want the entry hole). Probably pretty 'optimal engineering' as designed to minimize weight so both the top and bottom (flanges) and the sides (web) may have little tolerance for modification. You might also introduce an unintended stress riser point.
IMHO:
"No way to tell so don't chance a horrible death an expensive failure over a trick mod."
A slight touch of optimism there, but basically I'm a conservative olde phart when it comes to that kind of mod.
Makes sense. I suppose I will focus on less risky mods. Thanks
you can drill it towards the shock end without any issue. says me though. and as DP pointed out, you dont want to drill on the top or bottom of it.
as for what carbmon said, the bending stress is highest there. But its not as high as a full cantilever since its not completely locked in place. its allowed to rotate about the swingarm pin.
aside from that, im assuimg you are on a steel swingarm. THey made them out of aluminum too. Ofcourse i dont know how big that hole is, you start putting holes andtaking a significant section out then thats just asking for trouble.
of course i would just run it along the swingarm. I think it looks cool when you see the routing of the wire.
Quote from: He Man on November 23, 2012, 09:38:09 AM
as for what carbmon said, the bending stress is highest there. But its not as high as a full cantilever since its not completely locked in place. its allowed to rotate about the swingarm pin.
Correct, in a sense, .... if you consider the "full cantilever" to the the length from the swingarm pivot to the axle. The hinge joint at the swingarm doesn't resist bending force so there's no bending stress there at all, only shear.
Even with the hinge joint at the swingarm pivot and the shock mount, I'm pretty sure that at any instant the bending stress at the shock mount is the same as a pure cantilever of the length from the shock pivot to the axle, with the load at rest being the rear sprung-weight of the bike and very significantly greater when you hit a bump at speed due to vertical acceleration of the mass.
Plotted as a force diagram that bending force (max at the shock mount) tapers away from the shock mount to zero toward both the axle and the swingarm pivot. The shape of those boxy modern cast aluminum or carbon fiber swingarms that are fat (in profile) at the shock mount and rapidly taper to each end very closely approximate that bending force diagram - they are optimally designed for the thin sidewalls (beam web) allowed by that fabrication method and material strength, yielding the lightest possible structure for the material. Actually very cool engineering, though not visually appealing to my eye. A great example of "form follows function".
The significant removal of web material for the axle-slide adjustment slot (where shear stress is greatest) strongly indicates that bending moment (maximum at the shock mount), not shear stress, is the limiting design factor in the relatively uniform cross-section of straight steel and extruded aluminum swingarms. Efficient engineering would dictate optimal design (plus safety margin) at the location of limiting factors. The question becomes: “Is the swingarm in question over-engineered enough at the selected location to tolerate the material removal without bending failure?†For the sake of weight, and having some faith in the skill of weight-conscious Ducati engineers, I hope not. [thumbsup]
Quote from: He Man on November 23, 2012, 09:38:09 AM
you can drill it towards the shock end without any issue….
So, for the reasons explained above, I must respectfully disagree.
Apology for the ramble, but trying to optimize engineering solutions is what made my working career so much fun and I still find it fascinating and fun stuff even though I'm out of the business. ;)
I agree, but the difference here is how comfortable you are with making that hole and how big the hole is. As for the bending forces, the heavy reinforcement towards the shock end is suppose to resist out of plane torsion isnt it? The shear component here is negligible in this discussion so thats not a concern unless we are talking about the swingarm pivot.
So yes, the large question is do you think the safety factor is well beyond that so you feel comfortable making that hole? Considering that they make the swingarm out of aluminum as well, id feel comfortable enough to put A hole in the swingarm (no mentioning of how large the hole is..read on). If you start computing out the maximum moment at the shock point, were mainly talking about the M/EI component, as well as the limiting radius of gyration im really only concerned about how big the hole is since your modulus of elasticity is much larger. I bring the aluminum swingarm into context because given the same forces, and essentially same design, the strength of the material plays a big role. So my main concern is how big that hole is. But considering its a hydraulic line, and you need to fit the banjo head through as well as someone else pointed out, i neglected to really think about that. if it becomes a really significant cross sectional area you are removing,thenyou are looking at the cross section of the web thats nearly 10-15% area reduction ( off the top of my head). So i'll put a addendum to what i said, how big do you want to make that hole?
I really dont think the duc engineers gave much of a damn about saving weight on the ducati monster.
Now, as far as quoting me on that. Im going to get a ton of backlash since there isnt significant discussion and people tend to pull things out of context.
But yes, i agree with you about the engineering aspect, but how big is that hole? Thats really the determining factor here for me.
Standard OEM Monster brake line would require nearly 3/4" diameter hole to fit the banjo fitting through.
Which swingarm are you targeting; steel/aluminum, hoop/ST/S*R/M696/M796/M1100?
Steel. But I think I won't do it. However I have loved the reeducation of some of the physics I have long forgotten. (Wish there was a handshake emocon).
I think that ultimately we're talking apples-and-apples, He Man.
Personally I'd have no problem with a small hole to hide an electrical conductor in the swingarm, for example.
For the hydraulic line, the hole to pass the banjo is probably about what would be needed to fit a protective grommet around the bare hose even if the fitting were swaged-on after threading through the arm.
If you don't like the expression “weight†as a design parameter of the engineers, how about “dollars� While not engineered to be the lightest machine possible, the Monster was certainly designed to a price point, and “weight†as it relates to choice of the beam section is basically the same as “dollars†in the production design equation.
In any case, we seem to end up at the same point: Poking holes in swingarms should not be done with impunity and the size and location of the hole are important. Without a bunch of crazy reverse engineering and computation, ya just gotta go with yer gut and the indefinable personal safety factor therein.
As I said in my original post while admitting a conservative bent in this context, the hole for the brake line crosses that indefinable personal comfort threashhold ("IMHO ....") Hell, on my current project I'm agonizing over making a hole in a clip-on bar for hiding switchgear wiring.
Lacking a handshake emoticon, I'll raise a mug and offer the avatar I use on a different forum. Ride long and prosper !
[beer]
(http://i1188.photobucket.com/albums/z419/mypicnow/AFECMRA.jpg)