Crack or Scratch?
#1
Member
Thread Starter
Crack or Scratch?
I just picked up a clean Vintage TA Cyclotouriste crankset on EBay, but after polishing discovered what appears to be cracks on the non-drive-side arm near the top of the arm. Are these cracks or cosmetic scratches?
#2
Full Member
Join Date: Nov 2016
Location: SoCal
Posts: 489
Bikes: 2014 Bruce Gordon Rock&Road, 1995 Santana Visa Tandem, 1990 Trek 520, 2012 Surly LHT
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 211 Post(s)
Likes: 0
Liked 43 Times
in
35 Posts
Not sure what to see in the 1st photo so no opinion on it. The 2nd photo, my opinion is it is a scratch stretching left to right. The reason I say that is at the left end, it appears that a two "features" on the left merge at a very shallow angle, which I interpret as a short scratch merging into a longer scratch. But if you think they are cracks I would not suggest not using it; from what I hear a breaking a crankarm can lead to a serious crash. You could try to find a lab that can do an ultrasonic inspection to see if it is a crack.
#3
Senior Member
Join Date: Aug 2005
Location: Pittsburgh, PA
Posts: 33,656
Bikes: '96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '20 Surly Midnight Special, All are 3x10. It is hilly around here!
Mentioned: 39 Post(s)
Tagged: 0 Thread(s)
Quoted: 2026 Post(s)
Likes: 0
Liked 1,096 Times
in
742 Posts
Agree the first photo tells us nothing but that "scratch" shown in the second photo appears to indeed be a scratch. However, it's deep enough and in a high stress location that I would worry about it being a "stress raiser" and could lead to a real crack and failure. I personally wouldn't use that crank.
#4
Member
Thread Starter
Thanks, guys. I appreciate the educated guesses. I will do some further inspection, and perhaps an ultrasound as you suggested.
#5
Senior Member
Join Date: Sep 2010
Location: Roswell, GA
Posts: 8,319
Bikes: '93 Trek 750, '92 Schwinn Crisscross, '93 Mongoose Alta
Mentioned: 30 Post(s)
Tagged: 0 Thread(s)
Quoted: 1438 Post(s)
Liked 1,092 Times
in
723 Posts
Surface scratches can be filed/sanded/polished out to remove the stress risers. This is commonly done on airplane propellers to restore nicked and dinged surfaces to airworthiness. Information you may find useful starts on page 23 of this Advisory Circular: https://www.faa.gov/documentlibrary/.../ac_20-37e.pdf
Likes For krecik:
Likes For FiftySix:
#9
Senior Member
Join Date: Jun 2014
Location: Ontario, Canada
Posts: 4,624
Bikes: iele Latina, Miele Suprema, Miele Uno LS, Miele Miele Beta, MMTB, Bianchi Model Unknown, Fiori Venezia, Fiori Napoli, VeloSport Adamas AX
Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 1324 Post(s)
Liked 927 Times
in
640 Posts
I'd call that a gouge rather than a scratch. To use that unit, I'd definitely sand/file/grind it out so that it has a gradual taper to the main part of the unit. Take a piece of wood about the same size and try breaking it. Now put a deep gouge/scratch like that in the same area of the piece of wood and try breaking it. You'll most likely be able to break that piece of wood fairily easily and the break will happen on or close to where the gouge/scratch is. that's why it's called a stress riser; it concentrates stresses to that locale.
Cheers
Cheers
#10
Member
Thread Starter
Thanks for the recommendation. This seems to be the course of action that I need to take if I want it to retain its integrity.
#11
Senior Member
Join Date: Jun 2014
Location: Ontario, Canada
Posts: 4,624
Bikes: iele Latina, Miele Suprema, Miele Uno LS, Miele Miele Beta, MMTB, Bianchi Model Unknown, Fiori Venezia, Fiori Napoli, VeloSport Adamas AX
Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 1324 Post(s)
Liked 927 Times
in
640 Posts
Cheers
Likes For Miele Man:
#12
Member
Thread Starter
Thank you. I will definitely do this, as I don’t want it to be at all noticeable.
#13
Full Member
Cracks are not that straight, so like others have said, scratch or maybe better term gouge?
#14
Senior Member
Join Date: Apr 2010
Location: Elevation 666m Edmonton Canada
Posts: 2,478
Bikes: 2013 Custom SA5w / Rohloff Tourster
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 1236 Post(s)
Liked 318 Times
in
245 Posts
It's a gouge. Anyway we need a better pic of the whole part. I thought it was a dented rim looking at the pic. LOL
Is it CF ?? WTH.
I would DEMAND my money back from the bugger that sold it.
Is it CF ?? WTH.
I would DEMAND my money back from the bugger that sold it.
Likes For GamblerGORD53:
Likes For quindecima:
#17
Member
Thread Starter
#20
Senior Member
Join Date: Jun 2020
Location: Oregon
Posts: 71
Bikes: Flex, Volkscycle MarkX
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 26 Post(s)
Likes: 0
Liked 12 Times
in
5 Posts
Doesn't make any difference, a good tig welder could clamp that up and make a quick pass over it and be done. I haven't tig welded in years but I know I could do it.