BMW K bikes (Bricks)

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1Back to top Go down   Top Box!! Grrr... Empty Top Box!! Grrr... on Sun Oct 18, 2020 12:45 am

jjefferies

jjefferies
Silver member
Silver member
Just posting to let off some irritation with humor. So it's a hot day, because of another darker story, I'm my way to CalMoto out in Livermore, CA. My nearest in terms of time, BMW shop from the little island of Alameda, CA.. Mission: to pickup some one time use bolts for my other, big Red, K75's clutch (the darker story). Why would bolts on the clutch be one time use?? Anyway, let's focus on this story. I lane split through the Tube that goes under S.F. Bay between Oakland and Alameda, I'm on the ramp leading up to I-880 AND WHOA!! what is that laying on the side of the road?? Dang that looked like a Top Box. You know one of those things that fit on the back of a bike to put your helmet and other things in. WoW, split second decision, no way I can get over and grab it without running the risk of dying as the autos around me are jousting like it was a Le Mans to see who's first onto the freeway. So I take a short right and exit the on-ramp and take a go round the center of Oakland, CA.  to re-enter the on-ramp. Yes!! It is! A nicely sized 2 liter or bigger Top Box. Heavy too. And the mounting brackets are still attached. And in fact they look like they were cut off with a grinder. Hmmm! Barely room for a K-75 to be pulled over on this on-ramp but I put down the side stand and proceed to bungee the bugger on my back seat. Three HUGE pickup trucks whizz by me practically blowing the bike and me over. This is stupid risky but hey a nice top box. So I slide off the on-ramp back around to the underground entrance to the Tube back over to Alameda and home. I drop the top box in my yard and hustle back over to the freeway 3rd time is a charm and on my ride to CalMoto. There I pickup the six bolts for a mere USD $27.00. And I'm still wondering why one time use. And I have a little fine dining at Wendy's with the 3 tables outside. In these Covid-19 times my idea of fine dining is fast food at a joint where you can eat outside.

Back home, I open up the Top Box. Really nice, got some weird wiring coming out of it. But already I'm looking at how I can mount the top  box on Silver, my former project bike which is now my every day ride. There's a liner in there covering the mounting bolts. I pull it aside. DAMN! I find DMV registration papers and evidence of Insurance papers. Big Sigh! it's no longer just a found on the freeway item. It belongs to a rider. I have a minor conscience battle. Irritating things, consciences. But I do my due diligence and it turns out it's not a rider but a company but by this time I've acknowledged having the box.  So after contacting them they give me an e-mail address to correspond with. Which I do. Stating in my most pleasant manner that if they want it they can come pick it up otherwise I'll convert it to my own uses. Yeah, Ok. So maybe I was getting a tad ahead of myself and should have realized that it probably wasn't a freebie. The company apparently is one of these use an app. to rent an electric scooter things and probably someone has been billed for its loss. The spot I found it in was 20 or 30 feet from one of the many homeless encampments that ring Oakland so I suspect that someone there took the scooter for their own nefarious purposes and discarded the top box.  Why? Who knows. It's all a mystery about these encampments and their inhabitants.

    

2Back to top Go down   Top Box!! Grrr... Empty Re: Top Box!! Grrr... on Sun Oct 18, 2020 5:15 am

chris846

chris846
Life time member
Life time member
Golly, are you saying those bolts are one-time use? 


 (starts counting on fingers..... Embarassed )


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

3Back to top Go down   Top Box!! Grrr... Empty Re: Top Box!! Grrr... on Sun Oct 18, 2020 4:37 pm

jjefferies

jjefferies
Silver member
Silver member
@chris846 wrote:Golly, are you saying those bolts are one-time use?
 (starts counting on fingers..... Embarassed )
That's my opinion as well. But I thought the purists on this website might have some reason why.

    

4Back to top Go down   Top Box!! Grrr... Empty Re: Top Box!! Grrr... on Sun Oct 18, 2020 4:54 pm

Stump

Stump
active member
active member
one time use is for bolt stretch. It's a calculated amount multiplied by the amount of torque. Once done, the fastener won't repeat (it's been stretched). I see it in coupling bolts and reciprocating machinery. High energy multistage pumps as well. I'm assuming these are the flywheel bolts that screw into the crank. See the same thing on the output coupling bolts on air heads.

    

5Back to top Go down   Top Box!! Grrr... Empty Re: Top Box!! Grrr... on Sun Oct 18, 2020 10:42 pm

jjefferies

jjefferies
Silver member
Silver member
@Stump wrote:one time use is for bolt stretch. It's a calculated amount multiplied by the amount of torque. Once done, the fastener won't repeat (it's been stretched). I see it in coupling bolts and reciprocating machinery. High energy multistage pumps as well. I'm assuming these are the flywheel bolts that screw into the crank. See the same thing on the output coupling bolts on air heads.
Thanks, at least there's some theory behind it. Not just my suspicions that it's another way to milk my billfold. As an aside something I've noticed in getting these bolts out is that the last one usually will cause all sorts of trouble. Think it may be related to having loosened the previous bolts and the last one getting a bit of a kink as a result. I've seen this while watching the last two times getting into the clutch assembly. What I've found helpful is to loosen each clutch bolt and then re-tighten it but not torque it down. Then after initially loosening all three or six (depending on how you're going about it) it's easy to completely take them out.

    

6Back to top Go down   Top Box!! Grrr... Empty Re: Top Box!! Grrr... on Mon Oct 19, 2020 4:30 am

chris846

chris846
Life time member
Life time member
Seriously, my unenlightened understanding is that stretch bolts work like those springs that hold exhaust sections together - the torque/angle figures are calculated so's you take them into the elastic stage of their deformation. Elastic deformation means that they recover fully after release, just like a spring that's not been overstretched. For the bolts to permanently deform, they would have to be tightened further than this, to take them beyond elastic deformation and into plastic deformation, from which they don't recover. It's the same as overstretching a spring. I always thought that it was unlikely that this would be the case with these bolts, since once you apply enough stress to achieve plastic deformation, the graph -force vs deflection- steepens and the component starts to approach failure.

It was a long time ago though  Shocked

FWIW I have previously measured one of these clutch bolts, 'before and after' and it was the same length.


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Sometimes I'm not really Suzi Quatro.
    

7Back to top Go down   Top Box!! Grrr... Empty Re: Top Box!! Grrr... on Wed Oct 21, 2020 2:08 am

Laitch

Laitch
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@chris846 wrote:Seriously, my unenlightened understanding is that stretch bolts work like those springs that hold exhaust sections together - the torque/angle figures are calculated so's you take them into the elastic stage of their deformation. For the bolts to permanently deform, they would have to be tightened further than this, to take them beyond elastic deformation and into plastic deformation, from which they don't recover. 
Torquing can cause any bolt to stretch; stretch of a bolt can be part of clamping force. Specified torque range in common bolts is designed to preserve their elasticity while providing sufficient stretch to augment clamping force. 

Some "stretch" bolts—torque-to-yield bolts—are designed to enter plastic deformation rather than remain elastic. That is why those in particular are specified for one-time use. It can be possible to use smaller T-T-Y bolts than common bolts for similar applications because T-T-Y bolt clamping force is as great and tends to be more uniform. 

From your useful observation, we learn that these clutch bolts are not in that class although BMW's recommendation of replacing them suggests that they are. In the interest of sharing further scientific inquiry, please reef on them harder—starting at a temple vein-bursting rate and ending with a dying strain—then measure them. Smile


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1995 K75 81,000 miles
Top Box!! Grrr... Usa-lo10
    

8Back to top Go down   Top Box!! Grrr... Empty Re: Top Box!! Grrr... on Wed Oct 21, 2020 4:43 am

chris846

chris846
Life time member
Life time member
Sounds like my kind of project. Will do  bounce


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Sometimes I'm not really Suzi Quatro.
    

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