Damaged Carbon Frame - Power Loss?

GH - Sydney said:

A few months back an airline guerilla decided to smash up my wife's
carbon frame. (Stupidly it was being transported in cardboard... we
have learnt this lesson). The bottom tube was impacted such that the
impacted area felt like thick paper. (It felt like it could be pressed
all the way through with your thumb). Basically the integrity of that
area was completely compromised. I looked around for a while as to
whether this could be repaired. There are a lot of different opinions.
Eventually I found a shop that had a guy who makes carbon frames and
fixes them. His approach was to cut out the effected area and then do
some process to fill it all in. Sanded back and a new paint job and to
the eye and touch it seems brand new. However, since then my wife's
bike times in several races have dropped off substantially. (She is an
Hawaii IM age group champion and is very strong on the bike). Her times
over 180 km are about 20 minutes down on normal and all other things
are equal - in fact she is in the best condition of her life and we
have ruled out 'rider issues'. She reports, following these races,
that she is absolutely working overtime on the bike and seems to be
getting nowhere. Her perceived exertion is significantly higher than
before the bike was damaged. A few experienced pro's at a race
recently said to her that they think it could be her frame, that it's
structural integrity had been compromised and was possibly flexing too
much, thereby reducing power flow, and if so, over a serious TT could
result in big time differences. Views?????

I'm no expert, but 20 minutes seems a lot of time for a bit of flex in
the frame.
Are these races time trials? If yes, you should be sure that conditions
are always the same (wind, etc), which is not easy.
If no, IMO it makes no sense to compare times.

Just my 0.2$
(I see a looooooong thread starting here :-) )

On 23 May 2005 21:26:35 -0700, "GH - Sydney"
<[email hidden]> wrote:

[snip]

Quoted message said:

. . . times
over 180 km are about 20 minutes down on normal and all other things
are equal . . .

[snip]

Dear G.,

A rider used to cover 180 km in X minutes, but is concerned
by recent times over the same course rising to X + 20
minutes.

Assuming that it used to take 300 minutes and now takes 320
minutes, the ride time has increased 6.7%.

For the same 111.85 miles, the average speed dropped from
22.37 mph to 20.97 mph, 1.4 mph slower.

It is highly unlikely that all other things are equal. No
gentleman would suggest that the rider's output could have
dropped, but the bike could have a problem or the wind could
have blown differently.

The wind is quite likely. Here's a calculator to play with:

http://www.kreuzotter.de/english/espeed.htm

When I place your wife on a triathlon bicycle, reduce her to
100 pounds and 5'4" (take her out to dinner after this
calculation), set the trip distance at the bottom of the web
page to 112 miles, and leave everything else at the
defaults, the results are a happy 22.4 mph and 5:00:00.

But if I increase the wind from a dead calm 0 mph to a
steady 2.2 mph headwind, your poor wife crosses the finish
line dead last at 5:20:00 at only 21.0 mph.

(Raising the temperature from 68F to 86F doesn't make up for
the headwind, but it does improve her time four-and-a-half
minutes, reducing it it to 5:15:30. The barometric pressure
will change things, too, but isn't available on this
calculator.)

Over a 112 mile course, a significantly cracked carbon frame
is much easier to detect than a 2.2 mph headwind increase,
which is little more than half a brisk 4 mph walking speed.

Carl Fogel

For clarification, the 20 minute decrease is a subjective assessment
compared to times ridden by other competitors she has competed against
many times. Its not a comparison between two events on the same course
under different conditions. So, the question is : could the damaged
carbon frame, even after the repair described, result in a significant
power output reduction (of say 5%)?

GH - Sydney said:

For clarification, the 20 minute decrease is a subjective assessment
compared to times ridden by other competitors she has competed against
many times. Its not a comparison between two events on the same course
under different conditions. So, the question is : could the damaged
carbon frame, even after the repair described, result in a significant
power output reduction (of say 5%)?

If this were to be the case it would be evident to someone not used to
the bike if he/she would be to ride it. If the repair doesn't show up
the tube isn't flexing very much at that point and stiffness should be
the same or even increased.

Check alignment and for changes in the seating position. Did you change
components, say tyres?
--
---
Marten Gerritsen

INFOapestaartjeM-GINEERINGpuntNL
www.m-gineering.nl

"GH - Sydney" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

However, since then my wife's
bike times in several races have dropped off substantially. (She is an
Hawaii IM age group champion and is very strong on the bike). Her times
over 180 km are about 20 minutes down on normal and all other things
are equal - in fact she is in the best condition of her life and we
have ruled out 'rider issues'. She reports, following these races,
that she is absolutely working overtime on the bike and seems to be
getting nowhere. Her perceived exertion is significantly higher than
before the bike was damaged. A few experienced pro's at a race
recently said to her that they think it could be her frame, that it's
structural integrity had been compromised and was possibly flexing too
much, thereby reducing power flow, and if so, over a serious TT could
result in big time differences. Views?????

Borrow a new bike/frame, similar spec, and see what happens.

Quoted message said:

On 23 May 2005 21:26:35 -0700, "GH - Sydney"
<[email hidden]> wrote:

[snip]

Quoted message said:

. . . times
over 180 km are about 20 minutes down on normal and all other things
are equal . . .

[snip]

Dear G.,

A rider used to cover 180 km in X minutes, but is concerned
by recent times over the same course rising to X + 20
minutes.

Assuming that it used to take 300 minutes and now takes 320
minutes, the ride time has increased 6.7%.

For the same 111.85 miles, the average speed dropped from
22.37 mph to 20.97 mph, 1.4 mph slower.

It is highly unlikely that all other things are equal. No
gentleman would suggest that the rider's output could have
dropped, but the bike could have a problem or the wind could
have blown differently.

The wind is quite likely. Here's a calculator to play with:

http://www.kreuzotter.de/english/espeed.htm

When I place your wife on a triathlon bicycle, reduce her to
100 pounds and 5'4" (take her out to dinner after this
calculation), set the trip distance at the bottom of the web
page to 112 miles, and leave everything else at the
defaults, the results are a happy 22.4 mph and 5:00:00.

But if I increase the wind from a dead calm 0 mph to a
steady 2.2 mph headwind, your poor wife crosses the finish
line dead last at 5:20:00 at only 21.0 mph.

(Raising the temperature from 68F to 86F doesn't make up for
the headwind, but it does improve her time four-and-a-half
minutes, reducing it it to 5:15:30. The barometric pressure
will change things, too, but isn't available on this
calculator.)

Over a 112 mile course, a significantly cracked carbon frame
is much easier to detect than a 2.2 mph headwind increase,
which is little more than half a brisk 4 mph walking speed.

Carl Fogel

What about her average pulse rate. Has that changed? Pulse rate is a
rough guide to energy expenditure. What does her pulse monitor say?

Marty

GH - Sydney said:

She reports, following these races,
that she is absolutely working overtime on the bike and seems to be
getting nowhere. Her perceived exertion is significantly higher than
before the bike was damaged. A few experienced pro's at a race
recently said to her that they think it could be her frame, that it's
structural integrity had been compromised and was possibly flexing too
much, thereby reducing power flow, and if so, over a serious TT could
result in big time differences. Views?????

I find it very unlikely that a normal feeling downtube could be allowing
significantly more flex without other obvious symptoms (feeling very
flexy when pedaling hard standing). Even if the frame was flexing a bit
more now, it shouldn't affect TT riding, since that is pretty much
steady effort seated riding.

Of course none of this matters if she is convinced her frame is at
fault, sounds like new frame time to me.

GH - Sydney said:

Eventually I found a shop that had a guy who makes carbon frames and
fixes them. His approach was to cut out the effected area and then do
some process to fill it all in. Sanded back and a new paint job and to
the eye and touch it seems brand new. However, since then my wife's
bike times in several races have dropped off substantially. (She is an
Hawaii IM age group champion and is very strong on the bike). Her times
over 180 km are about 20 minutes down on normal and all other things
are equal - in fact she is in the best condition of her life and we
have ruled out 'rider issues'. She reports, following these races,
that she is absolutely working overtime on the bike and seems to be
getting nowhere. Her perceived exertion is significantly higher than
before the bike was damaged. A few experienced pro's at a race
recently said to her that they think it could be her frame, that it's
structural integrity had been compromised and was possibly flexing too
much, thereby reducing power flow, and if so, over a serious TT could
result in big time differences. Views?????

If the frame was flexing enough to make THAT much difference, it would
be very obvious (she'd be scared to stand up to climb, for example).

The one thing you might check is the bottom bracket alignment. You
should be able to sight between the chainrings, and see the middle cog
on your cassette. This could be off to the right or left by a cog,
but should be very close, and the cogs and chainrings should be
obviously parallel (any misalignment should show up fairly well).

You might also think about checking the bottom bracket and wheel
bearings for wear, and toss on a new chain just to be safe.

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $695 ti frame

GH - Sydney said:

A few months back an airline guerilla decided to smash up my wife's
carbon frame. (Stupidly it was being transported in cardboard... we
have learnt this lesson). The bottom tube was impacted such that the
impacted area felt like thick paper. (It felt like it could be pressed
all the way through with your thumb). Basically the integrity of that
area was completely compromised. I looked around for a while as to
whether this could be repaired. There are a lot of different opinions.
Eventually I found a shop that had a guy who makes carbon frames and
fixes them. His approach was to cut out the effected area and then do
some process to fill it all in. Sanded back and a new paint job and to
the eye and touch it seems brand new. However, since then my wife's
bike times in several races have dropped off substantially. (She is an
Hawaii IM age group champion and is very strong on the bike). Her times
over 180 km are about 20 minutes down on normal and all other things
are equal - in fact she is in the best condition of her life and we
have ruled out 'rider issues'. She reports, following these races,
that she is absolutely working overtime on the bike and seems to be
getting nowhere. Her perceived exertion is significantly higher than
before the bike was damaged. A few experienced pro's at a race
recently said to her that they think it could be her frame, that it's
structural integrity had been compromised and was possibly flexing too
much, thereby reducing power flow, and if so, over a serious TT could
result in big time differences. Views?????

i wouldn't let her ride with a "repaired" carbon frame. the failure you
describe is typical. the repair is almost impossible to undertake
successfully achieving full reintegration of the two fiber sets with
similar compaction. i'd abandon that frame asap.

regarding potential absorption of energy, yes, it's definitely possible
for that to be happening, so some extent, but to the level you describe?
there would have to be noticeable distortion occurring i'd say.

regarding finding a person that would repair it, it's dangerous to rely
on someone that tells you what you want to hear. some while back, i did
some work in a situation where a load bearing member of a large concrete
structure had been core drilled by mistake. two major steel
reinforcements had been completely cut and were clearly visible in the
core. the individual responsible for the repair consulted no less than
six structural engineers until they found one prepared to give the
answer they wanted - "there's no need to worry, just fill the hole &
forget about it". the cost delta between that & the "real repair" of
paring back the concrete, repairing the steel, then reconcreting a
larger safety zone was six digits. if i may say, "repair" for your
frame is exactly the same kind of [mis]judgment.

Quoted message said:

Of course none of this matters if she is convinced her frame is at fault,
sounds like new frame time to me.

In this case, that's by far the most important issue. If her confidence in
the bike is diminished, it really doesn't matter whether the frame is
actually sucking up a lot of energy (which seems hard to believe) or not.
She needs to replace it, period. Either that or a lengthy period of
psychotherapy to convince her that it's all in her mind, but I have a
feeling a replacement bike will be a faster and less-expensive fix.

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com

"Peter Cole" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

GH - Sydney said:

She reports, following these races,
that she is absolutely working overtime on the bike and seems to be
getting nowhere. Her perceived exertion is significantly higher than
before the bike was damaged. A few experienced pro's at a race
recently said to her that they think it could be her frame, that it's
structural integrity had been compromised and was possibly flexing too
much, thereby reducing power flow, and if so, over a serious TT could
result in big time differences. Views?????

I find it very unlikely that a normal feeling downtube could be allowing
significantly more flex without other obvious symptoms (feeling very flexy
when pedaling hard standing). Even if the frame was flexing a bit more
now, it shouldn't affect TT riding, since that is pretty much steady
effort seated riding.

Of course none of this matters if she is convinced her frame is at fault,
sounds like new frame time to me.

jim beam said:

i wouldn't let her ride with a "repaired" carbon frame. the failure you
describe is typical. the repair is almost impossible to undertake
successfully achieving full reintegration of the two fiber sets with
similar compaction. i'd abandon that frame asap.

And replace it with a carbon frames where the ends of the tubes are
joined with exactly the same proces?

If you don't mind a weight increase a decent repair is quite possible. I
agree however that in some hands a bodge repair is more likely

--
---
Marten Gerritsen

INFOapestaartjeM-GINEERINGpuntNL
www.m-gineering.nl

Jim, I think the comparison with your large concrete structure is a bit
too far of a stretch. We didn't exactly run around trying to find
someone who would repair it ... that is a pretty big assumption on your
part. To be frank, the debate was pretty evenly spread as to whether
the repair could be done successfully, and this thread confirms that.
For a few hundred bucks we thought it would be worth the attempt, as
opposed to 10-fold that for the new frame. Anyway, you seem pretty
sure of what you are talking about - can you elborate on why you think
energy absorption is possible?

GH - Sydney said:

Jim, I think the comparison with your large concrete structure is a bit
too far of a stretch. We didn't exactly run around trying to find
someone who would repair it ... that is a pretty big assumption on your
part. To be frank, the debate was pretty evenly spread as to whether
the repair could be done successfully, and this thread confirms that.
For a few hundred bucks we thought it would be worth the attempt, as
opposed to 10-fold that for the new frame. Anyway, you seem pretty
sure of what you are talking about - can you elborate on why you think
energy absorption is possible?

Jim always seems pretty sure of what he's talking about. It is, in fact, his
most distinguishing characteristic. Excepting of course his skepticism of
whatever anyone else is talking about.

Just from a non-mechanical-engineers POV, the power loss attributed to the frame
seems severe enough that I would think there'd be signs of increased compliance.
Does the frame actually feel any different? Front derailler grinding?
Perceptible whippiness? Death wobbles on descents? Sponginess out of the saddle?
Anything?

Just curious. See, I think it would be possible, but also that for a time
trialer it would have to be a very flawed frame to make that big a difference.

Ron

RonSonic said:

Jim always seems pretty sure of what he's talking about. It is, in fact, his
most distinguishing characteristic.

No, that'd be his hard-on for Jobst.

RonSonic said:

GH - Sydney said:

Jim, I think the comparison with your large concrete structure is a bit
too far of a stretch. We didn't exactly run around trying to find
someone who would repair it ... that is a pretty big assumption on your
part. To be frank, the debate was pretty evenly spread as to whether
the repair could be done successfully, and this thread confirms that.
For a few hundred bucks we thought it would be worth the attempt, as
opposed to 10-fold that for the new frame. Anyway, you seem pretty
sure of what you are talking about - can you elborate on why you think
energy absorption is possible?

Jim always seems pretty sure of what he's talking about. It is, in fact, his
most distinguishing characteristic. Excepting of course his skepticism of
whatever anyone else is talking about.

if i express skepticism of misplaced or inaccurate opinion or pure
conjecture being presented as fact, well, it's because i /do/ have
knowledge & experience of those subjects, and i /do/ know to the
contrary. thanks. is it a crime to state that an emperor's naked or do
you just want to listen to the bleating of the other sheep?

Quoted message said:

Just from a non-mechanical-engineers POV, the power loss attributed to the frame
seems severe enough that I would think there'd be signs of increased compliance.
Does the frame actually feel any different? Front derailler grinding?
Perceptible whippiness? Death wobbles on descents? Sponginess out of the saddle?
Anything?

Just curious. See, I think it would be possible, but also that for a time
trialer it would have to be a very flawed frame to make that big a difference.

Ron

Jim I thought you told me not to take things personally!
Interestingly, for you at least, no one with experience in carbon fibre
has yet agreed with your view that a repair is impossible. In fact,
several materials experts have claimed it is easy and very successful.
So, disreagrding the original intent of this topic, following your
logic, all the carbon experts have 'misplaced or inaccurate opinions'
(not that an 'inaccurate opinion' is logically possible, because it is
just an opinion, not an expression of truth) and I ought to trust your
view as gospel. Right?

GH - Sydney said:

Jim I thought you told me not to take things personally!
Interestingly, for you at least, no one with experience in carbon fibre
has yet agreed with your view that a repair is impossible. In fact,
several materials experts have claimed it is easy and very successful.
So, disreagrding the original intent of this topic, following your
logic, all the carbon experts have 'misplaced or inaccurate opinions'
(not that an 'inaccurate opinion' is logically possible, because it is
just an opinion, not an expression of truth) and I ought to trust your
view as gospel. Right?

you mean frank & taipo on sci.materials? those were "in depth"
technical answers for you?

first, frank's an r.b.t. guy. doesn't mean he knows nothing, but with
respect to frank, he's not exactly giving away the crown jewels of
wisdom there.

taipo's answer is worth quoting again: "Functional repair is easy if you
know what you are doing. Getting it to look nice is more difficult,
just paint it nicely black." brilliant response.

if you're having trouble with the concept, thank of the composite as a
piece of wood [which is very close to the truth by the way]. if you
crack a piece of wood, a structural material with which you hopefully
have some familiarity, i doubt you'd "repair" it with bondo & expect it
to have the same structural integrity, right? hopefully it's apparent
that there's lack of fiber integrity, bonding issues, etc. so, it's the
same with your wife's frame. would you think of flying in a plane with
a "functional repair" like that?

it's funny. you come here for free advice. you don't like what you
hear. you complain. way things are, your wife will continue to be
dissatisfied, and guess what, it's not going to be my problem! but hey,
this opinion is worth what you just paid for it. have a nice day.