| Author | Message | ||
     Xl1200r |
How much weight would you feel comfortable hanging from a grade 8, 1/4"-20 bolt from the undertail of your bike? I've been trying to figure this out, but the only thing i can find lists an M10 bolt being able to sustaion 26 kN (about 5800 lbs), and that just seems a bit optimistic to me. | ||
| Seanp |
I'm not an engineer, but I'd say it depends on how expensive the weight is...  | ||
| Djkaplan |
Will the load be in shear or tension... or a combination of both? | ||
| Xl1200r |
tension only. | ||
| Mr_grumpy |
Vibration? Metal fatigue? Lots of variables to consider. I generally go with the principal of 'belt & braces' & try to use more than one fastener if possible. 1/4" is M6 if that helps any. | ||
| Djkaplan |
Just tell us what you're doing. Give all the details you can with any variables that might be encountered. | ||
| Xl1200r |
I've built a mount for a pair of saddle bags that threat into the holes about halfway up the undersiade of the tail on my forbolt. So yeah - there's vibration and a constant weight bearing straight down. There are arms that bolt to the passanger peg mounts, so the whole thing is stable, but the force on those is pushing up so they aren't taking any of the weight. | ||
| Mikej |
Dynamic stressors are something I don't get paid to do, I just draw the pictures. I think this one is clearly in Blake's arena. | ||
| Swampy |
I don't know but I have been told...... What about the 7/16 bolts holding the "Do Not Remove" bracket to the front of the head? I had so many break....I even had one break in three pieces! | ||
| Adrenaline_junkie |
The grade 8 bolt should hold a lot more than the aluminum threads you have it screwed into. How much will the aluminum threads hold? Hard to say. Would need to know the grade of aluminum, what kind of tempering, if any, it had done to it and several other things. | ||
| Jlnance |
I've been trying to figure this out, but the only thing i can find lists an M10 bolt being able to sustaion 26 kN (about 5800 lbs), and that just seems a bit optimistic to me. That is optimistic. That's probably the force required to break the break the bolt, you don't want to get anywhere close to that. One thing to remember is that if you hang a weight off something, and that something bounces, like a motorcycle does, the force from the weight will be amplified. | ||
| Classicbuells |
Bear in mind the actual effective diameter of a 1/4" bolt is a LOT less than a 1/4". If possible increase the screw size to 3/8". HTH. | ||
| Xl1200r |
I think the threads themselves are actually brass imbedded in the aluminum - how those are held in I have no idea. I'm thinking this trip is just going to require a couple bungee chords, or a strap of some kind. I really wanted to rig these bags up in a way that put all the weight on top of the passenger seat because that's proven to be able to take the weight, but the guy I had making the bracket kind of wanted to do a quick and dirty job. It looks nice, but I don't trust it for anything. | ||
| Slaughter |
I'd also be more concerned about the subframe itself than the bolt. The "R" subframe is not that heavy gaged aluminum. The rivnut-type fasteners just won't take the loads that I think you're talking about. You'd be better off doing what you are describing or going to a GOOD aluminum welding shop and have them weld in a doubler and then use a couple fasteners so you're not single-point-loading that thin-walled square aluminum tubing in the subframe. | ||
| Xl1200r |
Yup - looks like I'm strapping the things over the tail then. I'm going to pull the plastic off the tail when I get the bike back today (new tires going on) and take a look at exactly what I'm dealing with. | ||
| Bott |
xl1200r do we have any good aluminum welding shops in the Albany area? I need some work done also. | ||
| Xl1200r |
Bott - the guy I use is actually VERY good, but this was kind of a favor, so we were looking for a quick fix. PM me if your interested and I can get you in touch. He works out of Stillwater. For anyone that's interested - What I'm dealing with is a Class III lever. The fulcrum is the front passanger peg mount, the weight is the bags (about 25 lbs loaded). Fulcrum to weight cog is 12.75", support point to weight cog is 4.25". Fe x De = Fr x Dr Fe x 4.25 = 25 x 12.75 Fe = 318.75/4.25 Fe = 75 lbs. Kind of a lot... | ||
| Blake |
If the bolt isn't being loaded in tension then is it just holding opposing bearing surfaces in position? If so, then why worry? | ||
| Blake |
A grade 8 1/4"-20 bolt is indeed rated for 120 KSI tensile proof stress on the nominal bolt section, so its proof load would be Pproof = p * 1/16 / 4 * 120KSI = 5,890 LB. The Yield stress is 130 KSI and the ultimate strength is 150KSI. You have no worries unless fatigue (cyclic stress) is an issue. | ||
| Mr_grumpy |
Blake I'm going to call you next time I have insomnia. That last post was as good as nytol, made me instantly sleepy.  | ||
| Gowindward |
The 1/4 bolt would not be the problem, it's the PEM type nut insert they use in the frame. The nut right now is only one of several attach points for the plastic tail body work, which is very little load. I would be figuring out a way to through bolt the connection on the sub frame. I would not trust the brass nut insert to hold. (Message edited by gowindward on March 26, 2008) | ||
| Blake |
Sir Grumpy, How can you possibly get sleepy when talking about such wonderfully exciting properties as yield stress and proof load? I know what it was. It's obvious that pie makes you drowsy.  |
