[Newman]

I can't see why this would be a problem and it gives me alot more room for my exhaust. I'm using 16mm socket head bolts(stainless steel) and locking nuts. Why do I need to run the pivot bolt all the way through?










.

 

[raven]

I don't see a problem with it either.

 

[Sevulturus]

The only thing I can think of is that you've gone from a double shear point to a single shear one. Basically, when the bolt goes all the way through the frame it puts equal pressure on both sides of the frame as the swingarm moves. What you've done... is essentially create a giant dull pair of scissors. And they could quite easily cut right through or bend those bolts. Personally, I wouldn't do it.

It looks like a good weight and space saver, and I cannot help but think that if it were safe to do we'd be seeing it on gp bikes, or at least race bike. But everyone uses a full size pivot bolt. There's gotta be a reason.

 

[The Green Lantern]

go for it,i cant see why it wouldnt work

 

[929_adam]

why dont u just grind the head down?

 

[raven]

why dont u just grind the head down?

He already replaced the single pivot bolt with 2 individual bolts, one on each side. Took me a minute to figure out the pics too.

 

[dogbreath]

es loco

Put a dent in the pipe.

 

[Scrapyard]

It's been done befor. Sev makes a valid point, but with the forked swingarm there's already a lot of flex in that area. Hense the reason that swingarm used the motor as a pivot point. I think it'll be alright, but I would recomend adding a cross brace to the frame once you get your exhaust set.

 

[Dudad]

why not just shrink the exhaust tube in that area then expand after?

 

[dogbreath]

why not just shrink the exhaust tube in that area then expand after?

Or just do what factories do... Dent the pipe! Whack that bitch with a rubber mallet

 

[skr00zloose]

Or just do what factories do... Dent the pipe! Whack that bitch with a rubber mallet

my suggestion too. i mean damn, look at a left side pipe on a factory tl1000, that fuggers got all sorts of bends/dents/flat spots in it. as long as the dent is a smooth transition, it should still flow fine.
with grade 8 bolts in there like it's set up now, i'd actually be worried about the bearings, the loads on them are going to be different than what they are intended for, and they could fail ALOT sooner than normal, and possibly crack the aluminum on the arm around the bearing.
not saying it wouldn't work, but i don't know if i'd feel comfortable riding the bike in anger.

 

[Candyman]

i don't know if i'd feel comfortable riding the bike in anger.

:Stupid: You get into some tight twisties I could see how flogging that bike right and left could put a lot of added stress on those bolts. Its probly not something that would break on the first ride out, more like in a couple years, after its lulled you into thinking you were safe and forgot about monitoring it.

Some things were designed a specific way for a good reason. What you have is a good idea, but maybe not the wisest. I'd go with a dent myself.:rock:

 

[dc original]

And they could quite easily cut right through or bend those bolts.

Quite easily? I disagree. The shear strength of a grade 8 bolt is quite impressive.

But everyone uses a full size pivot bolt. There's gotta be a reason.

Not necessarily true. It's a common misperception that all things engineered are done so specifically to make something better or safer. Many times they are engineered in order to produce or assemble easier or faster. Not that this is the case here but just an example that many design decisions in products have nothing to do with their function.

 

[dogbreath]

Well he said there's gotta be a reason, maybe that reason is to make it easier to put together

Just dent the pipe dude, don't risk your nuts over a flashy exhaust.

 

[CRF3]

it not the shear strength of the bolt thats gonna be the problem, its the fact that the force is now twisting on the bearings instead of pushing squarely against the races (like skrooz said). doesnt really matter why they designed it the way they did (strength or cost/ease of assembly) all that matters is that they did design it that way

I dont usually chime in on these things, and I dont wanna step on anyone's toes, but I would hate to see another biker get hurt for no good reason. :letsride:

 

[fslflint]

if you must do it at least go with grade 8 bolts. but a better way to do it would be to make a couple billet pieces that could be welded to the frame so that the pivot bolt is supported on both sides of the pivot. otherwise there is a shit ton of twisting forces on the frame and swingarm.

 

[skr00zloose]

if you must do it at least go with grade 8 bolts. but a better way to do it would be to make a couple billet pieces that could be welded to the frame so that the pivot bolt is supported on both sides of the pivot. otherwise there is a shit ton of twisting forces on the frame and swingarm.

that's a really good idea, just something to support the inside portion of the swingarm. that'd take alot of load off the bearings.

 

[mpls|cafe|racer]

What people are getting at is this.

That original pivot bolt is an axle. Plain and simple.

If you have a solid axle at that point of the arm you are spreading the force evenly across that bolt.

Force is force. You're not changing that, you're just giving it two areas to spread differently.

Excessive force to one side WILL eventually bend and snap a bolt.

Oh, as for the grade 8 bolts thing, those bolts are tested for strength longetudinally, meaning pull to snap. You're not putting a longitudinal load on those bolts though.... you're putting a lateral load.

Will a Grade 8 bolt snap at a higher load when pulled? Yes. But when bent? You're reducing it's ability dramatically.

Don't risk it.

 

[Sevulturus]

Quite easily? I disagree. The shear strength of a grade 8 bolt is quite impressive.

The sheer strength of a grade 8 bolt may be impressive, but that doesn't change the fact you're putting forces on the bolt in a way it was never intended to withstand. Do you have any idea how much force is transmitted through the swing-arm into the pivot bolt? Honestly, I don't... but I know that it has to be a rather impressive number. So the question is, "which is more impressive, the sheer strength of said bolt, or the force transmitted. As mentioned previously there's also the longitudinal force that is now going to be forced onto the needle bearings inside that swing arm.

Do you know how steel bars, spring steel, rebar, or anything of the like is cut at the factory? With a big hydrolic press. Kerchunk, and it's cut.

Or hell, think about all the damage that twisting force on a grade 8 bolt could do to a soft aluminum swing arm.

Not necessarily true. It's a common misperception that all things engineered are done so specifically to make something better or safer. Many times they are engineered in order to produce or assemble easier or faster. Not that this is the case here but just an example that many design decisions in products have nothing to do with their function.

That's the point. It's done for a reason. And if switching to two small bolts instead of one long one allowed more room, easier assmebly, and less weight don't you think it would have been done by now? It leaves a lot of extra room through the engine don't you think? Look at all that space you could put something in. Two small bolts weigh less then one long one... lets drop a lb or two. And it'd be faster to install those two small bolts then the one big one where you need to jimmy shit around. So I'll repeat, why wouldn't we be seeing this on race bikes if it's an advantage? Hell it probably also provides rigidity across the frame while turning. Bolt one side to the other.

if you must do it at least go with grade 8 bolts. but a better way to do it would be to make a couple billet pieces that could be welded to the frame so that the pivot bolt is supported on both sides of the pivot. otherwise there is a shit ton of twisting forces on the frame and swingarm.

I was going to suggest forking the swingarm mounts points. Have it mount on both sides of the frame. Same idea, just on the swing arm.

 

[Newman]

On this particular swingarm the cut out in the swingarm was there to allow it to go on each side of the engine. It allowed the swingarm to be long and still have a short wheelbase. The swingarm was clamped and supported by a bushing that ran through the back of the engine on the F4i.

The bolts are tested in tension 100,000 lbs I think, but no specs were given for sheer strength , something to think about.

I could put the bolt back in and run a smaller diameter pipe but I think since I was going to make another brace to strengthen the frame I will make braces attached to it that come back to the bolts to control the bending. I'm also going to change to double roller tapered bearings instead of using the needle bearings that are in the swingarm now.

Thanks for the input, I didn't put enough thought into this when I decided to make the change.