HELP-1960 period fork dimension question

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retrobuilder

Finally riding a big boys bike
Oct 8, 2017
115
65
Alpharetta, GA
Hello I have a 1960 Columbia reebuild which the owner failed to mention (or know) the fork was bent at steer tube...my bad as well.

I did a few aliggnment checks and these are what I measured.

The steer tube is bent ~51/4 to 5/16 at top to crown,. bending is fore//aft not side to side.
Fork rake measures 2 1/2" (64mm)
Hub spacing is 3-5/8" (92mm)

The fork blades appear centered from crown to axle to top steer tube.

Does anyone know the nominal rake for this period?

We can probably straighten in a 10 ton press - this is a fix or replace inquiry,
Pics included..

20180130_121002_resized.jpg


20180130_121315_resized.jpg


20180130_123425_resized.jpg


20180130_121029_resized.jpg
 

retrobuilder

Finally riding a big boys bike
Oct 8, 2017
115
65
Alpharetta, GA
Hello I have a 1960 Columbia reebuild which the owner failed to mention (or know) the fork was bent at steer tube...my bad as well.

I did a few aliggnment checks and these are what I measured.

The steer tube is bent ~51/4 to 5/16 at top to crown,. bending is fore//aft not side to side.
Fork rake measures 2 1/2" (64mm)
Hub spacing is 3-5/8" (92mm)

The fork blades appear centered from crown to axle to top steer tube.

Does anyone know the nominal rake for this period?

We can probably straighten in a 10 ton press - this is a fix or replace inquiry,
Pics included..

20180130_121002_resized.jpg


20180130_121315_resized.jpg


20180130_123425_resized.jpg


20180130_121029_resized.jpg
side view of bend addded..

bend.jpg
 

Kenny Middendorf

Look Ma, No Hands!
Nov 7, 2017
79
55
2003 South 4th Street, Fayetteville, IL, United States
that looks like its bent back a little bit . the last two bikes i bought were like that , they looked good but tracked funny and caused my feet to hit the fender when you turned it . it was a simple fix with the press ,just block it up with a couple 2x4 or something soft so you dont mess up the threads. if the bend has caused the tube to crack its less likley to stay where it belongs. and will need welded to be safe again. hope this helped
 

retrobuilder

Finally riding a big boys bike
Oct 8, 2017
115
65
Alpharetta, GA
that looks like its bent back a little bit . the last two bikes i bought were like that , they looked good but tracked funny and caused my feet to hit the fender when you turned it . it was a simple fix with the press ,just block it up with a couple 2x4 or something soft so you dont mess up the threads. if the bend has caused the tube to crack its less likley to stay where it belongs. and will need welded to be safe again. hope this helped
Thanks for reply.

The bend seems to be on steer tube and yes using a hydraulic press with a support at theupper part of the blade near the crown and the steering tube where the lower bearing seats is possible.

Just now cross checked the fork blades for alignment. Using the crown as the reference and moving a small level along the the tubes...the fork portion is in line on each side.

The rake is 2- 1/2" and looks right..In contrast to modern road bikes the rake is about 1.3/4 to 2".
I'll remeasure more as I straighten the the steer tube, maybe using cold bend.....as log as the steer tube is suppported at bearing race..

level 1.jpg
 

bikemonkey

I live for the CABE
Jun 25, 2016
1,361
67
North Carolina , Albemarle, NC, United States
Well that's self explanatory.. simple and makes sense...THANKS
If you are going to build a fork jack let me know and I can send a few other pics of it. Harbor Freight has bottle jacks for around $20.

When you get through you want the upper fork blades to be in the same plane of alignment as the head tube of the bike (where the fork enters the frame). You will need to jack the fork just a touch beyond straight as it will rebound slightly after the jack is removed.

Rebending the fork will cause some weakness at the juncture of the steerer tube and fork crown. You may want to examine it closely for hairline cracks when through and understand it could fail at that point in the future.
 
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retrobuilder

Finally riding a big boys bike
Oct 8, 2017
115
65
Alpharetta, GA
If you are going to build a fork jack let me know and I can send a few other pics of it. Harbor Freight has bottle jacks for around $20.

When you get through you want the upper fork blades to be in the same plane of alignment as the head tube of the bike (where the fork enters the frame). You will need to jack the fork just a touch beyond straight as it will rebound slightly after the jack is removed.

Rebending the fork will cause some weakness at the juncture of the steerer tube and fork crown. You may want to examine it closely for hairline cracks when through and understand it could fail at that point in the future.
I agree with your comments. I am also supporting the steer tube at the lower bearing seat as well.

THeoretcally your apProach should re bend the same as when the whells struck somethjing.

I'm concerned about two areas- The crown/blade joint and the bearing/steeer tube joints.

The primary bend is at the steer tube where the bearings supported the fork when impacted.and had a reaction force bend...KINDVE LIKE A FULCRUM.

The "blades" measure in plane and alignment with each outher and the top of steer tube..that's good.

You have a cool press tool..fairly explanatory.- I'd cut a half moon out of the 2x4 at the bottom bracket to better protect the roundness.

We willl probably setup on a 20 ton bress we have..but yours is a great simple way to push at the place the for got bent. using same method I used on AC Cobra racing suspension A arms years back...

Wish I had the rake dimension of the same or period forks...measures 2-1/2" now..I imagine it is deform a fraction of an inch.

THANKS TREMENDOUSLY..-- way better than using a large pipe and vise.method.
 

bikemonkey

I live for the CABE
Jun 25, 2016
1,361
67
North Carolina , Albemarle, NC, United States
I agree with your comments. I am also supporting the steer tube at the lower bearing seat as well.

THeoretcally your apProach should re bend the same as when the whells struck somethjing.

I'm concerned about two areas- The crown/blade joint and the bearing/steeer tube joints.

The primary bend is at the steer tube where the bearings supported the fork when impacted.and had a reaction force bend...KINDVE LIKE A FULCRUM.

The "blades" measure in plane and alignment with each outher and the top of steer tube..that's good.

You have a cool press tool..fairly explanatory.- I'd cut a half moon out of the 2x4 at the bottom bracket to better protect the roundness.

We willl probably setup on a 20 ton bress we have..but yours is a great simple way to push at the place the for got bent. using same method I used on AC Cobra racing suspension A arms years back...

Wish I had the rake dimension of the same or period forks...measures 2-1/2" now..I imagine it is deform a fraction of an inch.

THANKS TREMENDOUSLY..-- way better than using a large pipe and vise.method.
You are welcome...old school tool uses a ratcheting car jack but this is the next evolution.

The fork should be installed as usual before jacking it out. If there is a lateral bend in the blades this fork jack does nothing to help with that. You will know if that is an issue when you ride it if it pulls to one side. Park makes a tool to help with that alignment but it is much more difficult to set without a fork jig.

Yes..cut half moons in the 2x4s for the bb shell. I used a cut off section of old handlebar and then flattened it a bit. It goes in between the fork blades over the axle and distributes the force from the jack along the axle and keeps the jack plate from slipping.

Screw the base of the jack into the 2x4 assembly - I also used T straps with wood screws in a few places just to add some strength.
 
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rhenning

I live for the CABE
May 9, 2010
1,410
71
Sharon wi United States
This is my home made fork straightener using an old mechanical auto jack. Easy to use and does a good job. Roger

IMG_0960.jpg


IMG_0961.jpg


IMG_0962.jpg


IMG_0966.jpg


IMG_0970.jpg
 
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retrobuilder

Finally riding a big boys bike
Oct 8, 2017
115
65
Alpharetta, GA
This is my home made fork straightener using an old mechanical auto jack. Easy to use and does a good job. Roger

IMG_0960.jpg


IMG_0961.jpg


IMG_0962.jpg


IMG_0966.jpg


IMG_0970.jpg
kindve like the Park tool only simpler and 1960s ols school jack use..:) If it works use it.
 

AndyA

Finally riding a big boys bike
Nov 24, 2017
156
72
bergen county
There is an alternative to pushing with a jack. You can spin the fork in the frame (pointing backward instead of forward), put a rod thru the dropouts, rig a Spanish windlass between the rod the BB, and twist away. Pulling instead of pushing.
 

retrobuilder

Finally riding a big boys bike
Oct 8, 2017
115
65
Alpharetta, GA
There is an alternative to pushing with a jack. You can spin the fork in the frame (pointing backward instead of forward), put a rod thru the dropouts, rig a Spanish windlass between the rod the BB, and twist away. Pulling instead of pushing.
I'm rigging up a hydraulic press to correct the steerer tube bend with machinist V blocks..will post a picture or two when done. Supports will be at the crown and steer tube base.

Derusting at moment.

Thanks everyone for input..
 
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retrobuilder

Finally riding a big boys bike
Oct 8, 2017
115
65
Alpharetta, GA
I'm rigging up a hydraulic press to correct the steerer tube bend with machinist V blocks..will post a picture or two when done. Supports will be at the crown and steer tube base.

Derusting at moment.

Thanks everyone for input..
Thank YOU to everyone....after initial derusting check I noticed morre seriuos rust pitting amd metal removed.at the bottom of the Steer tube and under a stuck lower race.

Way too much material pittting problems to even touch up weld and file and then attempt to straignten....See picture.

Not going to straignten or anything else..replacing with a better fork...Learned a lot of straighyening methods..THANKS AGAIN.....Wayne

I'll make a lamp with it..:)

fork rust .jpg
 

bikemonkey

I live for the CABE
Jun 25, 2016
1,361
67
North Carolina , Albemarle, NC, United States
Thank YOU to everyone....after initial derusting check I noticed morre seriuos rust pitting amd metal removed.at the bottom of the Steer tube and under a stuck lower race.

Way too much material pittting problems to even touch up weld and file and then attempt to straignten....See picture.

Not going to straignten or anything else..replacing with a better fork...Learned a lot of straighyening methods..THANKS AGAIN.....Wayne

I'll make a lamp with it..:)

fork rust .jpg
I would wire wheel that area and see what it looks like under there - just me... But essentially I agree, failures at the fork crown can result in serious headers so replacement is the best route in this case.
 

bikemonkey

I live for the CABE
Jun 25, 2016
1,361
67
North Carolina , Albemarle, NC, United States
This is my home made fork straightener using an old mechanical auto jack. Easy to use and does a good job. Roger

IMG_0960.jpg


IMG_0961.jpg


IMG_0962.jpg


IMG_0966.jpg


IMG_0970.jpg
Nice! You could buy the shop version of this back in the 70's/early 80's - just like this one it was a modified car jack - that ratcheting sound always jacked up my nerves as well.
 

retrobuilder

Finally riding a big boys bike
Oct 8, 2017
115
65
Alpharetta, GA
Nice! You could buy the shop version of this back in the 70's/early 80's - just like this one it was a modified car jack - that ratcheting sound always jacked up my nerves as well.
The pitting goes around 1/4 uf the crown the steer tube lower race. I imagine inside is thinner too... This bike is intended to be a dsily rider and most of the pitting came off after abou 4 hours of derusting..
That area is the highest stressed part of a fork............

Going to make a lamp with it later with a chainring welded to the axle drop out.at base and also oak routed 8" base..Cheers :)
 
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