Add disc tab to Tange biplane fork
#1
Senior Member
Thread Starter
Add disc tab to Tange biplane fork
I've got a Tange biplane from an early 80s Specialized Stumpjumper on my gravel conversion and although I can easily add disc tabs to the frame I'm not sure about the fork. I'm a welder by trade and plan to tig weld it. My issue is if the fork will handle the stress of a disc brake.
Is this too dangerous or is it doable? What are the cons to this?
Is this too dangerous or is it doable? What are the cons to this?
#2
blahblahblah chrome moly
Join Date: Apr 2009
Location: Seattle
Posts: 1,987
Mentioned: 92 Post(s)
Tagged: 0 Thread(s)
Quoted: 1173 Post(s)
Liked 2,569 Times
in
1,073 Posts
#3
Senior Member
Join Date: Feb 2012
Location: Rochester, NY
Posts: 18,073
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4201 Post(s)
Liked 3,857 Times
in
2,305 Posts
Both the photos show a poorly designed caliper mounting bracket, with no stress spreading up the blade tail aspect. I will also speculate that the fork blades used in the failed images are of thinner diameter and/or wall thickness then what's likely on your bike.
The "but" is that it only takes one failure to do you in There's no way I would suggest this for anyone other then one's self. So you have to ask "what is my risk management and acceptance level". Only you can answer that.
For the cost of an already disked fork this whole question is moot and also be able to retain the reversing of the mod. Just reinstall the old fork. So my advice is to first consider a made for disk brake fork first. Andy
The "but" is that it only takes one failure to do you in There's no way I would suggest this for anyone other then one's self. So you have to ask "what is my risk management and acceptance level". Only you can answer that.
For the cost of an already disked fork this whole question is moot and also be able to retain the reversing of the mod. Just reinstall the old fork. So my advice is to first consider a made for disk brake fork first. Andy
__________________
AndrewRStewart
AndrewRStewart
#4
Senior Member
Join Date: Aug 2016
Posts: 712
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 283 Post(s)
Liked 262 Times
in
164 Posts
My old mtn bike with v-brakes and kool stop pads has the best brakes of my 4 bikes. Better than disc brakes. Underrated brake system IMHO. I think you will wreck your frame or fork or both, and need different wheels to boot.
#5
Senior Member
Join Date: May 2010
Location: Bastrop Texas
Posts: 4,476
Bikes: Univega, Peu P6, Peu PR-10, Ted Williams, Peu UO-8, Peu UO-18 Mixte, Peu Dolomites
Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 964 Post(s)
Liked 1,628 Times
in
1,044 Posts
#6
Senior Member
Join Date: Feb 2012
Location: Rochester, NY
Posts: 18,073
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4201 Post(s)
Liked 3,857 Times
in
2,305 Posts
This!!! This aspect of human thinking is at the root of so many issues. The lack of awareness is under one's radar until the "thing" happens to them. As the legal community says, "ignorance is no defence" Andy
__________________
AndrewRStewart
AndrewRStewart
Likes For Andrew R Stewart:
#7
Senior Member
Join Date: May 2010
Location: Bastrop Texas
Posts: 4,476
Bikes: Univega, Peu P6, Peu PR-10, Ted Williams, Peu UO-8, Peu UO-18 Mixte, Peu Dolomites
Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 964 Post(s)
Liked 1,628 Times
in
1,044 Posts
As an experienced welder I am sure you could engineer the dimensions of the disk tabs to compensate for weak areas in the fork. But it would still be an unproven design to start and most likely it would be better to go with a new fork and its supposedly proven design...
__________________
No matter where you're at... There you are... Δf:=f(1/2)-f(-1/2)
No matter where you're at... There you are... Δf:=f(1/2)-f(-1/2)
#8
Senior Member
Thread Starter
Thanks everyone for the reply,I figured a replacement for would be the best option but I was hoping to retain the classic looks of the biplane fork for a neo-retro look. My concern was mostly with the wall thickness and wetheror not the tubes are butted. I don't think it would be an issue with straight gauge tubes bit if they are butted then there may be an issue with the heat weakening the tube and causing a failure like in the pics.
Thank you again.
Thank you again.
#9
Senior Member
Join Date: Feb 2012
Location: Rochester, NY
Posts: 18,073
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4201 Post(s)
Liked 3,857 Times
in
2,305 Posts
Tube wall changes (butting) does not indicate any greater strength, or less strength. just that the walls did change. BTW most lower cost blades start as a tube with a constant diameter and wall thickness. Then this blank gets swaged down to form the tapered diameter/shape. The metal has to go somewhere and it results in a thickening of the now smaller diameter end's wall. It's the nice stuff (Reynolds as example with their taper gage blades and stays) that can start as the constant diameter balnk but with a butted wall, the end to be tapered starts with a thinner wall so after swaging that end's wall results in about the same thickness as the un tapered end has.
Not yet mentioned is the presence of and blade bending to achieve a rake. Most disk forks use a straight (un bent) blade and get the rake by having the straight blade leave the crown at an angle. For forks that use a socketed crown the sockets are about 7 degrees "cranked" from the steerer's axis. This method is used to reduce the time/effort of fitting a well engineered disk caliper mount to the blade. A curved/bent blade requires the caliper bracket to be mitered to fit the curve. Andy
Not yet mentioned is the presence of and blade bending to achieve a rake. Most disk forks use a straight (un bent) blade and get the rake by having the straight blade leave the crown at an angle. For forks that use a socketed crown the sockets are about 7 degrees "cranked" from the steerer's axis. This method is used to reduce the time/effort of fitting a well engineered disk caliper mount to the blade. A curved/bent blade requires the caliper bracket to be mitered to fit the curve. Andy
__________________
AndrewRStewart
AndrewRStewart
Likes For Andrew R Stewart:
#10
Senior Member
Thread Starter
Tube wall changes (butting) does not indicate any greater strength, or less strength. just that the walls did change. BTW most lower cost blades start as a tube with a constant diameter and wall thickness. Then this blank gets swaged down to form the tapered diameter/shape. The metal has to go somewhere and it results in a thickening of the now smaller diameter end's wall. It's the nice stuff (Reynolds as example with their taper gage blades and stays) that can start as the constant diameter balnk but with a butted wall, the end to be tapered starts with a thinner wall so after swaging that end's wall results in about the same thickness as the un tapered end has.
Not yet mentioned is the presence of and blade bending to achieve a rake. Most disk forks use a straight (un bent) blade and get the rake by having the straight blade leave the crown at an angle. For forks that use a socketed crown the sockets are about 7 degrees "cranked" from the steerer's axis. This method is used to reduce the time/effort of fitting a well engineered disk caliper mount to the blade. A curved/bent blade requires the caliper bracket to be mitered to fit the curve. Andy
Not yet mentioned is the presence of and blade bending to achieve a rake. Most disk forks use a straight (un bent) blade and get the rake by having the straight blade leave the crown at an angle. For forks that use a socketed crown the sockets are about 7 degrees "cranked" from the steerer's axis. This method is used to reduce the time/effort of fitting a well engineered disk caliper mount to the blade. A curved/bent blade requires the caliper bracket to be mitered to fit the curve. Andy
Ok,makes sense. I would assume the same to be true for shaping of chain and seat stays?
I guess I could just find someone who needs a fork like this for a build or restoration then and trade/sell it. Problem Im having is finding a decent 1" fork with disc tabs that isn't hi-ten steel. Also,I absolutely hate the look of a unicorn fork which all I've found seem to have. I really don't have the funds to have a custom fork built for it either.
Maybe I can make a disc tab that has a tail or fin that tapers down in height that extends about 4" past where a standard tab would stop.
On a unrelated note,the dropouts on this frame are identical to the ones on my Lemond Zurich save for the Lemond logo stamped into them. That means since they are semi horizontal I can run this bike geared,single speed or if I want to make it more difficult and less fun to ride a fixed gear.
Last edited by BoozyMcliverRot; 07-16-21 at 06:24 PM.
#11
Senior Member
Join Date: Aug 2012
Location: Seattle
Posts: 507
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 103 Post(s)
Liked 144 Times
in
88 Posts
I believe that is called a Willits style tab (not sure on the history). This will help but you still have a very flexible blade on the other side. I have seen instances where a builder will add a rib down the right blade as well to even out the flex but at that point, you're pretty deep into the project and you still have a 1" steerer that isn't well suited to disc brakes. Disc brakes are game changers from frame/fork design point of view.
__________________
https://www.flickr.com/photos/54319503@N05/
https://www.draper-cycles.com
https://www.flickr.com/photos/54319503@N05/
https://www.draper-cycles.com
#12
Senior Member
Thread Starter
I believe that is called a Willits style tab (not sure on the history). This will help but you still have a very flexible blade on the other side. I have seen instances where a builder will add a rib down the right blade as well to even out the flex but at that point, you're pretty deep into the project and you still have a 1" steerer that isn't well suited to disc brakes. Disc brakes are game changers from frame/fork design point of view.
I see. Thank you.
#13
Senior Member
Join Date: Jul 2006
Location: San Jose (Willow Glen) Ca
Posts: 9,845
Bikes: Kirk Custom JK Special, '84 Team Miyata,(dura ace old school) 80?? SR Semi-Pro 600 Arabesque
Mentioned: 106 Post(s)
Tagged: 0 Thread(s)
Quoted: 2338 Post(s)
Liked 2,822 Times
in
1,541 Posts
also to consider is that disk with QR is not considered optimum. Current disc technology is the the thru axle design
__________________
Life is too short not to ride the best bike you have, as much as you can
(looking for Torpado Super light frame/fork or for Raleigh International frame fork 58cm)
Life is too short not to ride the best bike you have, as much as you can
(looking for Torpado Super light frame/fork or for Raleigh International frame fork 58cm)