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#61
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drill/tap in frames
On Wed, 11 Jul 2018 09:42:08 -0700, Jeff Liebermann
wrote: On Tue, 10 Jul 2018 20:41:08 -0700, John B. Slocomb wrote: On Sat, 07 Jul 2018 12:33:38 -0700, Jeff Liebermann wrote: On Sat, 7 Jul 2018 11:06:52 -0400, Frank Krygowski wrote: This group has debated Rivnuts extensively. One poster claims nobody should install a Rivnut unless he has access to a complete machine shop. Others with more experience have said that the installation is easy for anyone with normal mechanical skills. That would be SMS (Steven Scharf) on one of his web pages: http://nordicgroup.us/cageboss/ Since I've made a mess with all the available technologies, Rivnuts (steel and aluminum), brazing (steel), TIG (aluminum), and epoxy glue (plastic boss on aluminum), I'll remain neutral on the matter. Hint: Use steel Rivnuts on steel frames, aluminum Rivnuts on aluminum frame, and plastic straps or clamps on CF (carbon fiber). One can only suppose that those "dumb asses: that manufacture rivnuts deliberately make their product in a number of materials :-) I'm not sure about the deliberate part, but yes, one can buy them in steel or aluminum. I couldn't find any plastic or carbon fiber rivnuts. And, it might be added that not knowing what you are doing is not limited to bicycle maintenence :-) True. If those expounding on bicycle technology by various electronic means really knew what they were doing, they would be riding instead of pounding on the keyboard. If you really want to know how things work, find someone that is actually doing the work and interrogate them for the information you need and don't bother reading books, manufacturers literature, magazines, forums, and newsgroups. The only downside is that those who really know, tend to be inarticulate and have difficulties explaining complex concepts, like which way to tighten a right handed bolt. However, persistence, intimidation, and perhaps bribery will eventually produce the required answer from a real expert. As I mentioned, I have successfully trashed most everything I've tried to do with Rivnuts on bicycles, and therefore have no opinion on the matter. However, it might be interesting to try a simple test. I could probably finance the test by taking bets on the outcome. Take two identical lengths of steel bicycle tubing. Install a Rivnut in only one tube at midpoint. Clamp one end in a pipe vise. Pull on the other end with a Come-Along perpendicular to the tubing. Measure the force with a load cell. Draw a graph to show when the tubing went plastic and eventually buckled. Compare results between the tubing with and without the Rivnut. That should settle the debate whether Rivnuts are detrimental to frame and stay strength. (Big Smile) I know a bike builder who accidentally did just that, with out the rivnut being installed - bending the curve into the front fork blades with a 5 foot bar :-) But as an aside, anything will break given sufficient force applied which doesn't prove much of anything. -- Cheers, John B. |
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#62
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drill/tap in frames
On 7/11/2018 10:18 AM, Jeff Liebermann wrote:
On Tue, 10 Jul 2018 21:25:06 -0700, John B. Slocomb wrote: On Mon, 09 Jul 2018 10:55:00 -0700, Jeff Liebermann wrote: On Mon, 9 Jul 2018 16:21:43 +0000 (UTC), David Scheidt wrote: sms wrote: :On 7/7/2018 7:27 AM, Emanuel Berg wrote: : Are there any secrets to drilling holes in : steel bike frames? I have a couple of discarded : ones I can test on but I thought I'd : ask anyway. : : Do you use normal power hand tools like : a drill-screwdriver and/or a drill press (if : possible with the desired bolt position)? : : Do the normal rules apply, e.g. to get : a threaded hole for an M6, you first drill with : a 5.0mm drill? : : And you can use chainsaw oil, right? :As Jobst Brandt stated: "I don't know many riders who believe that :drilling a hole in a frame tube is a reasonable concept." Who cares what riders think, what do the egineers do? Jobst Brandt was a mechanical engineer. https://en.wikipedia.org/wiki/Jobst_Brandt What's an egineer? One might comment that a fairly large number of bridges, that subsequently fell down, were designed by the engineers of the times :-) Therefore, anything designed by an engineer will eventually fall apart. I like the logic. Few can recognize an electronic problem or find someone on the design staff to blame. It's safety through obscurity. In chip design it's often easy to find who to blame. Actually the same holds true in much electronic design. |
#63
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drill/tap in frames
On Wed, 11 Jul 2018 10:18:38 -0700, Jeff Liebermann
wrote: On Tue, 10 Jul 2018 21:25:06 -0700, John B. Slocomb wrote: On Mon, 09 Jul 2018 10:55:00 -0700, Jeff Liebermann wrote: On Mon, 9 Jul 2018 16:21:43 +0000 (UTC), David Scheidt wrote: sms wrote: :On 7/7/2018 7:27 AM, Emanuel Berg wrote: : Are there any secrets to drilling holes in : steel bike frames? I have a couple of discarded : ones I can test on but I thought I'd : ask anyway. : : Do you use normal power hand tools like : a drill-screwdriver and/or a drill press (if : possible with the desired bolt position)? : : Do the normal rules apply, e.g. to get : a threaded hole for an M6, you first drill with : a 5.0mm drill? : : And you can use chainsaw oil, right? :As Jobst Brandt stated: "I don't know many riders who believe that :drilling a hole in a frame tube is a reasonable concept." Who cares what riders think, what do the egineers do? Jobst Brandt was a mechanical engineer. https://en.wikipedia.org/wiki/Jobst_Brandt What's an egineer? One might comment that a fairly large number of bridges, that subsequently fell down, were designed by the engineers of the times :-) Therefore, anything designed by an engineer will eventually fall apart. I like the logic. Hardly logic :-) Note the wording "engineers of the times" which is probably more indicative of the fact that one method of gaining knowledge is to fail, a few times :-) The problem with mechanical engineering is that problems, such as falling bridges, are easily visible. Even Joe Sixpack can recognize a mechanical failure. The fault is always with the architect or designer, and never with cost cutting contractor, sloppy construction company, defective imported components, blind inspectors, bribed officials, or the demands of the aesthetics committees. It's for this reason that I chose to go into electronics. Few can recognize an electronic problem or find someone on the design staff to blame. It's safety through obscurity. -- Cheers, John B. |
#64
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drill/tap in frames
On Wed, 11 Jul 2018 17:44:49 -0400, Frank Krygowski
wrote: On 7/11/2018 12:25 AM, John B. Slocomb wrote: One might comment that a fairly large number of bridges, that subsequently fell down, were designed by the engineers of the times Locally, the current hot problem is a historic and well-loved pedestrian suspension bridge in a park. One know-it-all claims he talked to one engineer who said "It's reached the end of its useful life" and offered to design a replacement for several thousand dollars, which would require many tens of thousands of dollars to build. Know-it-all wanted the village to hire the guy on the spot. When there was skepticism, the know-it-all (a marketing guy, BTW) brought in another engineer. Know-it-all claims this engineer said "I'd close it immediately for safety reasons." No details from either of those engineers on what might possibly fail. In fact, no direct communication from them at all. All we have is know-it-all's version of their views. I'm not sure I'd heap all the blame on the two engineers. A casual conversation can easily be interpreted :-) Given that doing oil exploration in the jungles can result in a lot of bridges being built one of out clients wanted some engineering data on "Wooden Bridges" which in the U.S. is, apparently, difficult to find. Luckily we hired an Australian Bloke who had worked for the Tasmania Timber Development who are still design and building fairly good sized wooden bridges. Shortly after we "discovered" Tasmania one of our people in the U.S. came across a retired guy who used rebuild wood bridges for the railroad and he still had a bunch of reference material that we copied. Meanwhile another registered Professional Engineer examined it and reported in detail, saying that there is no danger at all, that safety factors are in the hundreds, that only minor repairs are needed, and that those can be done by volunteers. I'm a retired PE, and I agree with that guy. But we'll see which way the politics go. I've always had good luck paying for a "preliminary report" to include recommendations. I find that most people get rather conservative when asked to "Sign the Report". -- Cheers, John B. |
#65
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drill/tap in frames
On 7/11/2018 5:39 PM, sms wrote:
On 7/11/2018 11:42 AM, Emanuel Berg wrote: Joy Beeson wrote: I put it there with cable ties ("wires") but there was an annoying sound while riding the bike. You need a hose clamp. Wrap the tube with handlebar tape to protect the paint. Also, clamp on tape has a much higher co-efficient of friction than clamp on hard surface. I attached two bottle cages this way late in the twentieth century, and haven't thought about them since. Good idea, I'll try that next. The hose clamp is an underrated commodity when it comes to bikes. No it's not. It's an over-rated kludge. Had you said 'inelegant' I would agree with you. But, like Joerg's headset clamp, functional. I've seen many ugly but workable stainless hose clamp repairs/upgrades on customers' bikes over the years but never a broken one. -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 |
#66
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drill/tap in frames
On Wed, 11 Jul 2018 13:48:47 -0500, AMuzi wrote:
I think the question isn't so much 'has the tube's ultimate strength been diminished?' but rather 'is it yet strong enough for expected application?'. Nope. I'm not trying to measure if the tubing is strong enough. Assuming identical lengths of tubing, I wanted to see if the presence of a Rivnut significantly changed the tension required to bend or break the tubing when compared to the identical tubing that did not have a Rivnut inserted. If I'm able to pull hard enough, I should be able to eventually break both tubes. If they break at the same tension, then I'll declare the Rivnuts are safe to use. If there's a substantial difference in tension, then I'll declare the Rivnuts weaken the frame. In theory and in absolute yes the tube is less strong. In practice, from Santana ExoGrid tandems to Bianchi thinwall tempered aluminum models, to their carbon bikes, rivnuts are not a failure point. Where are the Rivnuts installed on these machines? Water bottle holders? The pictures don't show much detail: https://www.google.com/search?q=Santana+ExoGrid+tandem&tbm=isch& https://www.google.com/search?tbm=isch&q=bianchi+aluminum -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#67
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drill/tap in frames
On Wed, 11 Jul 2018 15:46:28 -0700, John B. Slocomb
wrote: (Big Smile) I know a bike builder who accidentally did just that, with out the rivnut being installed - bending the curve into the front fork blades with a 5 foot bar :-) I think that's called a "torque amplifier". But as an aside, anything will break given sufficient force applied which doesn't prove much of anything. Ah, but if there's a significant difference in tension (force) between the tube with and without a Rivnut, then methinks it demonstrates that Rivnuts weaken the frame. I think the real trick will be to find two tubing pieces that are really identical. I'll check with the local "Bike Church" to see if they have any old frames laying around. I have a few frames, but I didn't want to trash them quite yet. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#68
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drill/tap in frames
On Wed, 11 Jul 2018 17:24:40 -0400, Frank Krygowski
wrote: Exactly. Strong enough is strong enough. OK, so let's pretend that the tube with the Rivnut bent at 10% less tension. Is that "strong enough"? There's no way to tell without the original design calculations, or reverse engineering the frame with an FEA model. Too bad Autodesk killed their online ForceEffect web app. http://blogs.autodesk.com/inventor/2017/01/17/autodesk-forceeffect-family-retirement/ I think I could have modeled the problem using the program. Maybe this will work: http://structural-analyser.com Nope. Won't do tubing. And BTW, the test you're describing would be much, much easier to do in a proper tensile testing machine. Find an engineering student, get him interested, have him get permission to do it as a class project, and your data would be much better. Yep, but my use of UCSC equipment has turned into a complex hassle. I'll spare you the details, but at this time, it's not an easy options. I was wondering how I would do it on a proper machine. Probably support the tube at the ends and push in the middle behind the Rivnut. The problem with that is I'll probably crimp the tube where it's pushing. It's likely I'll tear the tube before it bends. So, I'm stuck with securing one end, and pulling (or pushing) on the other. But on the other hand, tensile strength of the tube isn't really the concern. The concern would be fatigue strength, and if we're talking about the down tube, it would be under repeated, reversing torsional stresses. Good point. However, it will take too many tubing samples to test all the possible combinations of forces available. Shall we keep it simple and just bend a tube or two? I strongly suspect that you'd find no significant difference. One feature of the Rivnut is that its clamping action on the parent metal applies compressive stress. Fatigue cracks start in regions of tensile stress. The Rivnut may even make the object stronger. Clamping action requires equal compression at all points around the Rivnut hole. That's not going to happen in tubing where the Rivnut is being crimped onto a curved surface. At the peak of the curve, there will probably be plenty of compression force holding the Rivnut in place. 90 degrees to either side, there may be an air gap with zero compression force. In order to make it stronger on the curved surface of the tubing stronger, the Rivnut would need a matching curve. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#69
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drill/tap in frames
On 7/11/2018 5:08 PM, AMuzi wrote:
On 7/11/2018 5:39 PM, sms wrote: On 7/11/2018 11:42 AM, Emanuel Berg wrote: Joy Beeson wrote: I put it there with cable ties ("wires") but there was an annoying sound while riding the bike. You need a hose clamp. Wrap the tube with handlebar tape to protect the paint. Also, clamp on tape has a much higher co-efficient of friction than clamp on hard surface. I attached two bottle cages this way late in the twentieth century, and haven't thought about them since. Good idea, I'll try that next. The hose clamp is an underrated commodity when it comes to bikes. No it's not. It's an over-rated kludge. Had you said 'inelegant' I would agree with you. But, like Joerg's headset clamp, functional. I've seen many ugly but workable stainless hose clamp repairs/upgrades on customers' bikes over the years but never a broken one. Inelegant in some cases, kludge in some cases. There is almost always a more elegant, simple, minimalist solution. Maybe not as cheap though. http://www.minoura.jp/english/accessory-e/bh95x-e.html http://www.minoura.jp/english/accessory-e/lw-e.html https://www.amazon.com/dp/B00OS6HKIM http://www.zefal.com/en/bottle-cages-thermoplastic/60-gizmo-universal.html |
#70
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drill/tap in frames
On 7/11/2018 8:43 PM, Jeff Liebermann wrote:
On Wed, 11 Jul 2018 17:24:40 -0400, Frank Krygowski wrote: Exactly. Strong enough is strong enough. OK, so let's pretend that the tube with the Rivnut bent at 10% less tension. Is that "strong enough"? There's no way to tell without the original design calculations, or reverse engineering the frame with an FEA model. Too bad Autodesk killed their online ForceEffect web app. http://blogs.autodesk.com/inventor/2017/01/17/autodesk-forceeffect-family-retirement/ I think I could have modeled the problem using the program. It's a bad experiment because it doesn't take into account whether or not the hole was properly drilled and the Rivnut properly installed. You also have to do it with the same aluminum tubing used on a bicycle frame, but even then it isn't accurate because there's no way to factor in metal fatigue which isn't an issue as much in steel as it is in aluminum. Remember, just because you can often get away with doing a really stupid thing, it doesn't mean that you should still do it. |
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