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Now I'm positive I need to lose weight....

Old 08-31-22, 02:49 PM
  #1  
Ordo inanimalia
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Now I'm positive I need to lose weight....

Greetings you metallurgical magicians. I've been torturing a 2010(ish?) Raleigh m40 7005 aluminum for about a decade. It's finally shown some tangible sign of that abuse. The seat tube broke off just above the weld beads where the top tube and seat stays meet it. Due to the construction material it's a nice clean break. It appears that the welds for afore mentioned joint are all sound. My plan is to just drop the seat post into the seat tube and drill a hole an inch or two below the welds in the seat tube and post, fix it in place with a bolt/nut(or maybe the quick release bolt from the seat clamp) and call it fixed. Obviously, I would lose the seat hight adjustment function and I'm ok with that. My question is to what extent drilling a hole through the aluminum would compromise the structural integrity of the frame? Also, would hole placement in relation to distance from the welds mitigate any of that possible increased unreliability? I would have included corresponding images but I'm unable to due so as I'm new to the forum. I thank you in advance to all who sound off with any knowledge and experience you could lend me.
Ride on....
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Old 08-31-22, 03:00 PM
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The bike is finished- do not repair!
I ya wanna lose weight, keep ridin & stop eatin so much...
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Old 08-31-22, 03:11 PM
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Ordo inanimalia
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Lol nice. I'm actually in great shape. But let's pretend the bike isn't toast. I'm definitely going to keep riding it till the wheels fall off. Let's see if someone with some actual knowledge of the construction material can offer me some insight pertaining to my actual question. Not just shoot off ad hominem like a side character from the movie Idiocracy. Isn't there a Starbucks near by? Sounds like you could use a latte....
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Old 08-31-22, 04:06 PM
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Originally Posted by Ordo inanimalia
The seat tube broke off just above the weld beads where the top tube and seat stays meet it. Due to the construction material it's a nice clean break. It appears that the welds for afore mentioned joint are all sound.
If I understand the above correctly, a section of the seat tube which is above the top tube / seat tube / seat stay junction broke off cleanly, without affecting the welds that form said junction. However, that leaves no room to install a seat post clamp.

Originally Posted by Ordo inanimalia
My plan is to just drop the seat post into the seat tube and drill a hole an inch or two below the welds in the seat tube and post, fix it in place with a bolt/nut(or maybe the quick release bolt from the seat clamp) and call it fixed. Obviously, I would lose the seat hight adjustment function and I'm ok with that. My question is to what extent drilling a hole through the aluminum would compromise the structural integrity of the frame?
Doing so seems inadvisable, as any hole compromises the structural integrity of the frame (and the seat post), but I suppose the answer depends on (a) the size of the hole, (b) the material of your seat post, and (c) your weight. But if you insist on this approach, perhaps a series of smaller holes, spaced apart along the length of the seat post, would work better a single, bigger hole.

Originally Posted by Ordo inanimalia
Also, would hole placement in relation to distance from the welds mitigate any of that possible increased unreliability?
The lower you drill the top hole from the aforementioned junction, the more the seat post would flex within the seat tube (when you are riding), because you are effectively fixing the seat post to the seat tube at a lower position and increasing the length of the lever. So although your intuition to avoid drilling the frame near that junction is understandable, drilling at a lower position does not necessarily avoid or reduce stress on that junction. Which is why attempting this fix is inadvisable.
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Old 08-31-22, 04:09 PM
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Originally Posted by Ordo inanimalia
Lol nice. I'm actually in great shape. But let's pretend the bike isn't toast. I'm definitely going to keep riding it till the wheels fall off.
But the bike is toast, and if you keep riding it, more likely there would be an issue with the interface between the seat post and seat tube, causing you to fall off before either wheel does.
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Old 08-31-22, 05:56 PM
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Originally Posted by SoSmellyAir
If I understand the above correctly, a section of the seat tube which is above the top tube / seat tube / seat stay junction broke off cleanly, without affecting the welds that form said junction. However, that leaves no room to install a seat post clamp.
I'm engaging my "Devil's Advocate" mode here.
Based on the information provided, it sounds like the seatpost clamp assembly is still attached to the seatpost. This means that the rider's weight holds the fractured top of the seat tube in contact with the remainder of the seat tube. The seatpost's lower section would prevent the saddle from doing anything except rotate; it wouldn't fall off or represent a risk for serious injury. Drilling a hole through the seat tube and post at the selected location would stabilize the saddle against rotation.
With respect to the possibility of failure of either the seatpost or seat tube (or both) at this location, fracture of the seatpost would likely do nothing more than allow the saddle to rotate and prevent the bike from being lifted by the saddle. Failure of the seat tube would be accessible to early discovery by virtue of its location, and even a complete circumferential fracture of the frame at that location would probably not cause a catastrophe.

My reasoning is based on some personal experience. One of my folding bikes developed cracks in the seat tube radiating out from the stress-breaker hole at the bottom of the slot in the top of the tube. I discovered this too late to take corrective action (increasing the radius of curvature of the stress-breaker hole). The crack eventually circled the seat tube, disconnecting its top, including the clamp assembly, just above the weld joining the seat tube to the main frame member. The saddle would still support my weight, and the irregular surface of the fracture actually prevented rotation. The main problem was that lifting the bike by the saddle would pull out the seatpost. I fabricated two "stays" to connect the clamp assembly to the rack mounting holes in the frame. This allows picking the bike up by the saddle. This bike now has over 12,000 miles on it, and the problem described happened at about the 5,000 mile mark. The repair is not elegant, but it is functional.

Assuming the OP understands the issues and is able and willing to keep an eye on his repair, I see no reason he couldn't choose to do something like this.
(/DA Mode)


The fractured seat tube and the stays holding it together (sort-of) are seen. The seatpost extends well below the main frame member.
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Old 08-31-22, 07:33 PM
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The frame has failed and the bike is not worth much even new. The M40 was at or near the bottom of Raleigh's range.

If we are pretending I have a full fleet of Titanium Firefly bikes custom built to my specs and a large house with a lot of land with a velodrome in the basement and a massive swimming pool with a fun slide and a hot tub. The bike however is done, it is not a special collectible bike it is not worth much and there are plenty of awesome bikes that would either be a grade or better yet an upgrade. I am not saying that to be insulting just being honest and real about things.

I am all for saving bikes and keeping them going but sometimes it just isn't worth it and when an aluminum frame fails it is done. A nicer steel frame maybe I might try to save because you can actually re-weld a steel frame in some cases.
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Old 08-31-22, 07:47 PM
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Sounds like a plan...what could go wrong
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Old 08-31-22, 07:50 PM
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These last few responses are exactly what I was looking for. I would like to thank the both of you for the well thought out analytical advice. To answer some questions posed I am 6" 194lbs. I've been a fanatically diligent daily rider since I was four. I'm a mechanical engineer professionally and have been a "back yard mechanic" since I could turn a wrench. There was a section of seat tube approximately 50.8 mm that did in fact carry the seat post clamp broken just above the weld beads for top tube and seat stays. as properly ascertained above, no room was left to install an effective seatpost clamp. About 8 mm above the welds on the right(drive side) and 11 mm on the left. I used a rotating die grinder to clean that up and went out and purchased a stick of titanium rod in 27.2 mm and cut it so it rested on the water bottle rack attachment points inside the seat tube. I drilled two 1/8" holes with a water cooled shop press perferating both seatpost and seat tube. One 25.5 mm below the upper welds and the second the second the same distance up from the top rack fastener. I used stainless hardware in both. After an hour long trail ride an inspection showed no obvious sign of and damage due to flex. But more stress/ride hours would undoubtedly be required to find any visible Damage.
in summery, if I can finish the season on this frame I'll be happy. I got more than my money's worth from this platform. It's stood up to abuse that borders misuse and logged more hours than any bike I've ever owned. I run aftermarket cranks and a custom wheelset, otherwise it's stock. I'll miss it next year for sure.

Again. Thank you kindly to those that offered critical analysis and personal insight.
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Old 09-01-22, 02:59 PM
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Originally Posted by Ordo inanimalia
I thank you in advance to all who sound off with any knowledge and experience you could lend me.
Ride on....
Read the fine print on your dental coverage and tighten the straps on your helmet...
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Old 09-03-22, 07:07 AM
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Originally Posted by wheelreason
Read the fine print on your dental coverage ...
Heh... I'm a dentist, and can confidently predict that the OP's plan carries little risk to his dentition.
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Old 09-03-22, 09:27 AM
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Just a thought here. There are tens of?, hundreds of? thousands bikes out there with drilled seat tubes. And none of them have a snug seatpost supporting the tube at those drillings. Most are done as production process with little thought as to quality. Many but not all are reinforced with braze-on collars. Think water bottle bosses. In fact, many manufacturers put those same drillings in the much more critical tube, the downtube. Yet we don't hear reports of those tube cracking very often and actual failures and injury almost never.

So the OP wants to drill a hole or two, additionally stiffen the tube with another tube inside and this is going to affect his teeth? Maybe it will fail if he rides this bike long enough but I'd call it an 8000 mile repair. Ride it no longer than that distance, meanwhile looking for a replacement. No big deal. (I rode my Mooney's fork a year after bending both blades, one a lot, in a crash. Had a pro bend it back, ordered a new one and a year later, put the new one on and kept the old as a spare. And that was a fork, not a seat tube where nothing is likely to happen even if it cracks all the way around. (My race bike seat tube cracked and broke at the BB shell in a face. NBD. Rode it to the start/finish and retired it.)
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Old 09-03-22, 11:57 AM
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I see no benefit at all to drilling holes. What you need is a stop on your seat post fitted to the cleaned up and squared up weld area. You can put some silicone or something similar in there to act as adhesive. It needs to be a heat and release type so you can remove the seat post whenever necessary. Drilling holes just gives a breaking point, particularly with the back-and-forth movement of the seat post.
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