The end of bent derailleur hangers?

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The end of bent derailleur hangers?
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flag R-M-R
Posted: Oct 22, 2020 at 13:02 Quote
As I understand it, your position is that you want to reduce the frequency of damaged hangers and you're proposing breakaway hanger screws to accomplish this. My position, based on that understanding, is we're already at this point via optional breakaway derailleur screws. Please let me know if there's something missing from my understanding.

As long as the breakaway screws* - whether that's the derailleur screw or the hanger attachment screws - fail before the hanger, everything is fine. The failure load of the screws and the hanger can be determined by the manufacturer and either approach should be equally effective at solving this problem.

Reasons I favour placing the breakaway point at the derailleur, rather than the frame:

• One screw to replace, rather than potentially multiple.
• A hanger can be integrated with the dropout to ensure alignment with the axle. This is not possible with a breakaway hanger unless you introduce additional mating surfaces, which defeats the purpose of integrating the components.

It doesn't seem necessary to create an extremely strong hanger, as that would shift the "weakest link in the chain" to the derailleur or - worst of all - the frame. That said, we could then make stronger derailleurs and frames, but that's nothing new: we already have those options.



* I'm going to switch to proper terminology if we're going to have a proper discussion!
flag MTBrandonLee
Posted: Oct 22, 2020 at 13:22 Quote
cmcrawfo wrote:
General rule of thumb is to buy a replacement hanger the same day you buy your new bike ( I usually buy 2) . It fits in your pocket (unlike a derailleur alignment tool)... one lives with my riding gear, the other lives in my tool box.

However, if the hanger concept is problematic for an individual, a solution to that already exists.


a gearbox
I try to at least have 4-5 on hand. Couple for me. and some spares for the second owner when i sell the bike Big Grin
flag Sayshell
O+
Posted: Oct 22, 2020 at 19:01 Quote
R-M-R wrote:
As I understand it, your position is that you want to reduce the frequency of damaged hangers and you're proposing breakaway hanger screws to accomplish this. My position, based on that understanding, is we're already at this point via optional breakaway derailleur screws. Please let me know if there's something missing from my understanding.

As long as the breakaway screws* - whether that's the derailleur screw or the hanger attachment screws - fail before the hanger, everything is fine. The failure load of the screws and the hanger can be determined by the manufacturer and either approach should be equally effective at solving this problem.

Reasons I favour placing the breakaway point at the derailleur, rather than the frame:

• One screw to replace, rather than potentially multiple.
• A hanger can be integrated with the dropout to ensure alignment with the axle. This is not possible with a breakaway hanger unless you introduce additional mating surfaces, which defeats the purpose of integrating the components.

It doesn't seem necessary to create an extremely strong hanger, as that would shift the "weakest link in the chain" to the derailleur or - worst of all - the frame. That said, we could then make stronger derailleurs and frames, but that's nothing new: we already have those options.



* I'm going to switch to proper terminology if we're going to have a proper discussion!

I have no objection whatsoever to where the breakaway point is. Sure have it in the derailleur itself, that's fine. I agree with you that might be easier. But I think you are still missing my point about the hanger. Consider the following...

1) You want the amount of force it takes to snap the derailleur off the frame as high as possible without risking damage to the derailleur or frame itself. Agreed? Obviously you don't want your derailleur to fall off if you just roll over a rock rough.

2) Currently the force it takes to snap your hanger is already set to do this. Agreed?

3) Therefore if you use a breakaway derailleur screw with your current hanger, the derailleur screw must take less force to break than the hanger itself, otherwise the derailleur screw is useless agreed?

4) Therefore if you use a breakaway derailleur screw with your current hanger you are no longer at the maximum amount of force it takes to snap the derailleur without risking damage to the frame/derailleur, you are below it. And if you want to make it so it snaps before the derailleur can even bend, then you have dropped the amount of force it takes to break the derailleur off the bike much lower. Agreed?

5) Therefore if you use an invincible hanger, and a breakaway derailleur screw that takes the same amount of force to snap as your current derailleur hanger, it will take the exact same amount of force to snap the derailleur off the bike, but now it's impossible to bend the hanger. Agreed?
flag R-M-R
Posted: Oct 22, 2020 at 19:38 Quote
I'm afraid I don't agree.


1. Not necessarily. The frame seller wants to minimize the chance of damage to the frame, other than the hanger. There is little regard for the derailleur. The current methods for doing this are for the hanger to bend, permanently damaging the hanger, but not the rest of the frame, and for the optional breakaway derailleur screw to break before the derailleur is damaged.
2. No, a derailleur will typically be damaged long before a hanger snaps. That's why breakaway derailleur screws exist: to reduce the chance of damage to the derailleur, which also reduces the chance of bending the hanger.
3. Again, not necessarily. The screw should break before the derailleur is damaged, which could still be enough force to bend the hanger.
4. These points have already been addressed.
5. No, if a breakaway derailleur hanger screw is set to the force required to snap either a derailleur or hanger, the derailleur could be bent beyond any functionality - let alone proper functionality - before this point.


There are two fundamental problems with this system:

1. Derailleurs will be damaged long before a hanger is ripped off.
2. Presumably, the complete fracture strength of a hanger is below the point at which the frame is damaged, but metals bend before they break.

In other words, the frame should be strong enough to withstand the complete fracture of a derailleur or hanger, but both of the latter are bent long before this point. If we want to raise the "chain" of failure stresses up to the the yield stress of the frame without yielding of the derailleur or hanger, breakaway screws are the way to do it.

Another problem: this whole conversation is premised upon the assumption we don't want the frame to yield. Some derailleurs are more expensive than a replacement chainstay or seatstay, so sometimes the derailleur is the part in greatest need of protection.


I see two solutions:

1. Hangers become stronger and derailleurs remain at their current level of strength. Both are attached via breakaway screws that are set to break before the part they affix bends.
2. Hangers become stronger and derailleurs are strengthened to match the strength of the hanger and frame. Only one breakaway point is required; it doesn't really matter whether this is at the derailleur screw or the hanger attachment. It would be safer for the frame if the breakaway is at the hanger attachment, since a direct impact to the derailleur attachment could damage the hanger and the frame.
flag Sayshell
O+
Posted: Oct 22, 2020 at 20:09 Quote
R-M-R wrote:
I'm afraid I don't agree.


1. Not necessarily. The frame seller wants to minimize the chance of damage to the frame, other than the hanger. There is little regard for the derailleur. The current methods for doing this are for the hanger to bend, permanently damaging the hanger, but not the rest of the frame, and for the optional breakaway derailleur screw to break before the derailleur is damaged.
2. No, a derailleur will typically be damaged long before a hanger snaps. That's why breakaway derailleur screws exist: to reduce the chance of damage to the derailleur, which also reduces the chance of bending the hanger.
3. Again, not necessarily. The screw should break before the derailleur is damaged, which could still be enough force to bend the hanger.
4. These points have already been addressed.
5. No, if a breakaway derailleur hanger screw is set to the force required to snap either a derailleur or hanger, the derailleur could be bent beyond any functionality - let alone proper functionality - before this point.


There are two fundamental problems with this system:

1. Derailleurs will be damaged long before a hanger is ripped off.
2. Presumably, the complete fracture strength of a hanger is below the point at which the frame is damaged, but metals bend before they break.

In other words, the frame should be strong enough to withstand the complete fracture of a derailleur or hanger, but both of the latter are bent long before this point. If we want to raise the "chain" of failure stresses up to the the yield stress of the frame without yielding of the derailleur or hanger, breakaway screws are the way to do it.

Another problem: this whole conversation is premised upon the assumption we don't want the frame to yield. Some derailleurs are more expensive than a replacement chainstay or seatstay, so sometimes the derailleur is the part in greatest need of protection.


I see two solutions:

1. Hangers become stronger and derailleurs remain at their current level of strength. Both are attached via breakaway screws that are set to break before the part they affix bends.
2. Hangers become stronger and derailleurs are strengthened to match the strength of the hanger and frame. Only one breakaway point is required; it doesn't really matter whether this is at the derailleur screw or the hanger attachment. It would be safer for the frame if the breakaway is at the hanger attachment, since a direct impact to the derailleur attachment could damage the hanger and the frame.

I am not sure where you disagree then. The solutions you are proposing are exactly what I just said. #1 is literally 100% exactly what I just said. Eek Anyways I agree with either #1 or 2. Both solve the issue.
flag R-M-R
Posted: Oct 23, 2020 at 0:05 Quote
That's because I'm trying to work with your ideas and clearly define the possible implementations, including the possibility of increased derailleur damage if that's not concurrently addressed.

7075 aluminum and a slight increase in hanger thickness may be enough to create a significantly stronger hanger with existing designs. If not, if would have to be steel, which would triple the weight and would be a barrier to adoption. At least it may stay straight up to the maximum allowable load (complete fracture of a 6061 hanger, or failure of breakaway screws with a stronger hanger).

In the event of damage, two or more breakaway screws would have to be replaced. This may not be a lot cheaper than a replacement 6061 hanger, but at least universal breakaway screws are possible or, in a pinch, standard screws.

Those are a couple of potential benefits. The major drawback is the difficulty of adapting the breakaway hanger concept to designs that integrate the hanger with the hub axle threads, such as SRAM's UDH. And everything changes if SRAM implements direct-mount derailleurs.

Are you familiar with Syntace's X-12 hanger with breakaway screw?


photo
flag Sayshell
O+
Posted: Oct 23, 2020 at 8:07 Quote
R-M-R wrote:
That's because I'm trying to work with your ideas and clearly define the possible implementations, including the possibility of increased derailleur damage if that's not concurrently addressed.

7075 aluminum and a slight increase in hanger thickness may be enough to create a significantly stronger hanger with existing designs. If not, if would have to be steel, which would triple the weight and would be a barrier to adoption. At least it may stay straight up to the maximum allowable load (complete fracture of a 6061 hanger, or failure of breakaway screws with a stronger hanger).

In the event of damage, two or more breakaway screws would have to be replaced. This may not be a lot cheaper than a replacement 6061 hanger, but at least universal breakaway screws are possible or, in a pinch, standard screws.

Those are a couple of potential benefits. The major drawback is the difficulty of adapting the breakaway hanger concept to designs that integrate the hanger with the hub axle threads, such as SRAM's UDH. And everything changes if SRAM implements

Are you familiar with Syntace's X-12 hanger with breakaway screw?

No but from what I have heard they are stronger anyways, so they might not even need to be modded. My knowledge mainly goes up to around 5 years behind new, because I rarely buy new stuff. I also think the industry should go back to a 1X9 or 1X10. I'll probably get hell over that statement lol, but the box2 1X9 system just works magnitudes better. More space between gears = less misshifts/chain skips, lighter, bigger gears and chain = stronger (I know shimano says 12 is the strongest because there 12 speed chains use modern construction techniques, but only shimano is keeping their 9 speed stuff in the stoneage, the 9 speed ebike chains are REALLY strong), plus you can shift through your gears much quicker which is important on roller coastery trails, and cassettes are much cheaper. Additionally the more compact cassette produces better chainline and never has issues backpedaling (which can be useful for trick riders who do backwards riding) and for regular riders adjusting crankarm position while coasting. I just don't think the average rider needs perfect pedaling cadence, xc bikes/road bikes can/should use 12, but normal mtnbikes should be 9 IMO. But let's not derail the conversation in that direction too much (pun intended)

Putting that aside, you have made many good suggestions I agree with. Overall I like the derailleur break away screw more. It's replacing 1 screw vs 2. Simple and already exists. One downside is it's quite hard to put the derailleur back into the hanger without loosening the B-tension screw. This can create more down time on the trail.
When a hanger breaks normally you still have this downtime anyways, so it's still faster than changing a snapped hanger. Another benefit is you don't need a new frame with a special derailleur hanger if you use derailleur break away screw. With the hanger screws snapping the derailleur hanger could not go under the quick release skewer/thru axle.
I think a carbon hanger would also work well weight wise just because carbon doesn't really bend. The costs on that might be brutal though, but it's unlikely it would ever break if it had the break away screw. Super hard aluminum would probably be fine. Switching the break away point to the hardware with a stronger hanger I think just has no real disadvantage, and many important benefits. The average rider would benefit from cost, and not having to hunt down specific hangers + ease of installation / less down time on the trail. + They will never have to deal with the occasional bends they get from lighter impacts like small crashes/dropping the bike. For really technical riders/multi-disciplinary riders the benefits are colossal.
flag R-M-R
Posted: Oct 23, 2020 at 10:55 Quote
Now that we've clarified some issues on bending vs. breaking, etc., I feel we're at the core of the issue: Keeping the system fully functional up to the safe limits of the frame and derailleur. A stronger hanger and breakaway screws on one or both parts would do this. It adds some cost, but it's a reasonable idea. A Syntace hanger and a breakaway screw on the derailleur would accomplish it with existing components.

A derailleur can be installed without backing off the B-tension screw, but it's awkward: better to just back it off. This does take a little time, but maybe a minute. If you're breaking so many derailleurs or hangers that a minute per incident is a significant concern, I can see why you're concerned about this issue, but there must be a more fundamental problem!

My observation is that broken chains nearly disappeared with the front derailleur because the chain is no longer cross-loaded on the high-tension side. 12-speed chains are plenty strong for everyone I know. That said, I agree current cassettes have become carried away with the sprocket count and range. Few riders ever use their top ratios, let alone use them frequently. A 9-speed cassette with 400% - 450% range should meet the needs of most riders. My preference would be to execute it with 12-speed chain dimensions, make the cassette narrower, and improve the bracing angle of the rear wheel's spokes.
flag mtbtrekracer
Posted: Oct 23, 2020 at 12:41 Quote
Anther thread blown up and way more complicated than it needed to be.

Sram did their R&D on their UDH so let them just sell their hanger and be happy its becoming universal.
Can we now delete the last 3 pages???
flag R-M-R
Posted: Oct 23, 2020 at 12:56 Quote
Everyone "does their R&D" (actually not, in many cases, but likely in the case of UDH), yet crappy products still get produced, so there is always value in trying to analyze and improve.

A cynical interpretation of SRAM's UDH is that it's a sly market share grab: introduce a convenient product, sell it at zero margin to gain market share, then introduce a derailleur with a patented interface that works with only UDH frames when Syntace's perfectly good system already exists. Unknown whether this will materialize, but it's fun to speculate.

If you don't want to be part of it, you have the option to not read it, yet you did. You even took the time to post. Admit it: you love it!
flag mtbtrekracer
Posted: Oct 23, 2020 at 13:36 Quote
i honestly did not read any of what you and the other guy wrote... so i have no idea what you're on about, big forum posts do nothing except excite the inner "i did something today" feeling to the person who wrote it.
Your time is better off spent either working on your bike, riding your bike or making your own products for yours/others bikes.
flag R-M-R
Posted: Oct 23, 2020 at 13:41 Quote
So you don't even read posts, you just come into a thread and post to tell people to stop posting? What inner part of you does that excite? Maybe your time would be "better off spent either working on your bike, riding your bike or making your own products for yours/others bikes".
flag mtbtrekracer
Posted: Oct 23, 2020 at 13:45 Quote
R-M-R wrote:
So you don't even read posts, you just come into a thread and post to tell people to stop posting? What inner part of you does that excite? Maybe your time would be "better off spent either working on your bike, riding your bike or making your own products for yours/others bikes".

Rolleyes Rolleyes i read posts that are constructive and actually add some quality to a thread, when two people start going backward and forward about whos own willy is bigger it adds nothing.

exactly like you're doing now, you cannot help yourself but be the last person to reply.

My replies were simple and gave actual answer to a problem that already had a solution.
flag noideamtber
Posted: Oct 23, 2020 at 13:49 Quote
I to have no interest in reading big forum posts, especially when two people are "trying" to prove their own point lol.
flag R-M-R
Posted: Oct 23, 2020 at 13:55 Quote
mtbtrekracer wrote:
Rolleyes Rolleyes i read posts that are constructive and actually add some quality to a thread

Seems like you're reading this one! lol


mtbtrekracer wrote:
when two people start going backward and forward about whos own willy is bigger

Can you point me to the part where that happened?


mtbtrekracer wrote:
exactly like you're doing now

Not at all! I'm sure you're hung like a stallion! I'm just pointing out the irony of someone taking the time to tell other people to not take the time.


mtbtrekracer wrote:
you cannot help yourself but be the last person to reply.

Do you not see the irony in the things you say?


mtbtrekracer wrote:
My replies were simple and gave actual answer to a problem that already had a solution.

Your one reply was "Why is this even up for discussion? Sram UDH. plastic and alloy.. and guess what.. cheap...Every bike should come with this hanger, let shimano use "UDH" aswell and everyones happy, especially customers."

If you had read the other posts, which you claim you didn't even do, you would see it was just an exploration of the issue to gain some understanding. Some possible improvements came to light and some challenges were identified. People having a discussion. The very purpose of a forum.

 


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