Did not expect the multiphysics analysis! Bonus. I’m doing this same thing to a Giant. Just welded up the brake tabs yesterday. I’m paying close attention to your work. Thanks,
You can buy pre made caliper mounts from several bike frame builder suppliers in the US. No need to mill your own. I silver brazed mine and added a small gusset. I have over 3000 miles on the frame. No problems at all.
I’ve got a Brodie Catalyst that’s getting the gravel bike treatment …and this video is fantastic. Really liked the engineering to demonstrate that deflection under unrealistic loading is not even 0.2mm! Those are numbers I can live with. Subbed and thanks for your excellent work!
Very cool video, I appreciate the fact that you did some FEA to verify your choices, as that is what engineering is all about. I personally wouldn't do all the extra work of welding in a brace for a .5 increase in my safety factor, but I guess that depends on the frame one uses.
Whenever someone comes into a forum and asks about converting a 90's MTB to disc brakes by welding in tabs, the top response is something along the lines of "you'll die". It always seemed hyperbolic to me, I'm glad you busted out the FEA on this. I'm wondering what the safety factor on something more modern is, particularly a more all-road frame as opposed to a downhill bike. (deleted part of my comment, reading the linked studies now lol)
I have to agree that the frame looks better than it would have with a brace, and I was one of those who questioned why you chose not to install one. After watching this great explanation, it makes sense that the force applied is really negligible, especially with using a small diameter rotor (160mm). The force would have been higher if you had went with a 180mm, but that's not really needed on a road/gravel oriented bike on the rear.
About the need for a brace. I completely agree that your setup is fine. Steel frames are very strong, and also in practice the rear brake is only able to take maybe 1/3 of the stopping force before the rear wheel will skid - - physics. The more critical part is the front fork, but I'm assuming you just used a new disc-ready fork? Really cool build!
Awesome. Very well explained. Just wish I could weld. Loved the FEA but I'm not a big fan as very minor changes in the boundary conditions can have huge effects on the answers. Love the thru-axles.❤👍👍👍👍👍
I just did a back-of-envelope calculation and I got a different force on the caliper. Considering mu = 1 (dry asphalt, good tire) and rear tyre normal force Fz = 400 N, the stopping force is 400 N on the lever of 0.35 m (wheel radius). From the torque balance for the brake disc action radius (r= 0.07 m), that is 400*0.35/0.07 = 2000 N!. Looking at the second paper, I see they use mu = 0.5 in which case your result seems plausible but their experiment is in pretty much laboratory condition. I would be afraid that that frame could collapse in that one emergency braking situation when your rear tire bites to a rock in the ground. I am sure you will be fine on normal roads but I would think twice before riding some rougher trails.
Actually, that gives me an idea. What if I'd model the original cantilever brakes and see what forces those applied to the stays under the same conditions? It could serve as a good baseline. The only other idea I have is strain gauges on the rear stays but that is sure expensive and I'm 100% we'll get the same results.
@@RobertAdairWorkshop @RobertAdairWorkshop it surely would be interesting to reverse engineer the original design, just to put it into perspective with yours. But for rim brakes, the braking force might not even be the most significant one. For such thin tube I would definitely also consider the buckling load from your weight but and also from the forces from wheel into axle. Using strain gauges could be a fun project that I thought about myself. You can get cheap ones from china including some arduino amplifier modules. But proper installation, processing the results and calibration could be frustrating. If it was to me, I would simply lock the brake, try to turn the wheel to simulate the braking torque and observe closely the bending of the tube. Btw how did you measure the thickness of the stay tube for your FEM model? Is it the same along the length of the tube? And also what UTS of the material do you use in the FEM?
Very nice work. I made a similar transformation but with an early 2000's alu bike that already had disk mounts. The FEA analysis is interesting, but think I spotted a small mistake in the model. You seem to have defined the wheel axle as a rigid point, but it should be considered as a pivot. that way the seatstay should share some of the deformation with the chainstay, and show less difference between the braced and unbraced cases.
Congratulations on your bike, I liked how it turned out, I really like the on point methodology you explain to us about the FEA! Aluminum frames are another level to modify, right? I've got a cannodale m900 bike which is aluminum, same 90's built, it would be awesome if you could show us how to modify aluminum frames! Im not a welder myself but im eager to know how!
I did discs on an aluminum 1998 Stumpjumper last year. It was actually easier to do but you're kind of taking your life into your own hands with the brazing. ruclips.net/video/vD1pH86wCrU/видео.html
Fantastic video! Seriously an underserved subject on youtube a bike forums. I did want to ask if you considered just brazing the bracket onto the stay? Brazing is accessible to more people (a MAP torch from home depot is way cheaper than a tig setup) and certainly strong enough to handle anything i can give it with my grip strength right? Wouldn't have to be as concerned about contaminating a weld and every step would be almost the same except for the filler material.
Totally get it! With the FEA and exceptional thoroughness of your video I assumed it was a strength calculation. I wish I was setup for welding but brazing is super simple (except for the acetylene shortage ha). Getting filler rod of the right type is harder the torching metal until it starts wicking filler in. Great video again and glad it popped up in my feed. Newly subscribed!
Superbe reconversion du freinage . Je suis sur le même projet sur un cadre acier LOOK . Peux-tu me renseigner sur le support choisi pour le montage de l'étrier . Superb braking conversion. I am on the same project on a LOOK steel frame. Can you tell me about the support chosen for mounting the caliper.
curious, the use IS (not iso) mount because it opens up the options for flat and post mount caliipers, good choice. but the use of a what looks like maybe a IS to PM adapter (that adapter is huge) for a 203mm rotor to locate the mount for a 160mm rotor would remove the options of running flat mounts as the caliper won't be in the correct place. surely using a adapter for 160mm rotor in the first place would of allowed the creation of a IS mount that would suit all brake styles. yes using the BB5 cable brake is good, but just use enough flat spacers under it to account for the CPS washers thoose things usually use.
The 984N I calculated is for a situation worse-than a panic stop where there is no slippage. A panic stop would be less than that 984. The calculates FOS does cover max braking.
Then you. This is incredibly useful. Also, did you have to mill rear drop out to fit 12mm axle? I'm just about to get my self a classic gt or gary fisher. Cant waiiiit
I had to drill it out 12mm for the axle. If you're alright with me sharing a link to another video, check out the build video. I've started it at the timestamp for the thru-axle mods: ruclips.net/video/WDkYQHh_scU/видео.htmlsi=6kVaQ2sjjSYYOgUj&t=222
Dude, that's exactly what i want to do with an old frame i got. But i'll try to stick weld it because its the only way i have to weld it, hahahaha. Cool video, cool bike
Last summer I put 27.5" wheels on a 26" frame because they fit and I wanted the bigger wheels. Being a bigger wheel, the whole bike got a bit taller and it felt like I was riding on a tower of a bike. Did you find that this bike felt really tall with the bigger than intended wheels?
Which fork do you have in mind for the Kona? Asking because I have a similar frame (steel, disc tab added), it's currently set up as a hardtail mtb, and I'm considering more of a gravel setup.
I’m using one made by Soma for their fog cutter frame. It’s a straight steerer carbon fork with flat mount caliper and 12mm thru axles. Fits the frame really well.
No, sadly, this one is a bit too old to look at fatigue stresses. I’d like to have a modern version but the software is ridiculously expensive for one license. Maybe if I make it big on RUclips, I’ll celebrate with software.
Amazon. Here's the basic link -> www.amazon.com/gp/product/B07DND33HV I had to round the bottom of each with some sandpaper wrapped around a dowel, to get them to sit flat on the frame. I didn't show that in the video.
Hello there, could you by any chance send me the 3D-Model of the frame you created for the video? Step or any other type would be fine, but SLDPRT highly appreciated, as I use SolidWorks myself. Would be great and save me a ton of work. It doesn´t have to be perfectly my own frame, but I need a model of a retro-mtb-frame for an upcoming project. It would be great, if you could help me out on that. Kind regards Viktor (btw. If it if it makes a difference to you: I did not just find your channel while searching for a 3D-Model, but am an active viewer, and just remembered, that you made this model in this video before starting to create my own one)
Hey! I'd be happy to send you the Solidworks file for the frame. Send me an email and I'll attach it to my response. Its in SolidWorks 2006 so hopefully it'll still be compatible.
700c x 40. I talked about it in the original build video. That gives 8mm at the stay bridge. ruclips.net/video/WDkYQHh_scU/видео.htmlsi=dsn5uc-Sn0hriI5d&t=1179
@@RobertAdairWorkshop oh. Yes thanks. So 40c on a wide 27internal rim would be the frames max. That would probably bulge it out to 41 or almost 42. Ever thought about putting in some 42c ? Or would that be bad for your type of riding in muddy areas?
Dang man it sounds like you could tweak your compressor settings a little, seems like the first word of your sentences is getting cut off, anyhow great stuff!
Probably the noise reduction I use to try and cut down on the background noise from my workshop heater. I didn't notice til you mentioned it. I'll see what I can do for the next one.
Converting from rim brakes to disc brakes is really dangerous due to the different forces exerted on the frame. It can e. g. easily lead to fork failure.
![Ice On My Teeth - ATEEZ エイティーズ 에이티즈 [Music Bank] | KBS WORLD TV 241115](http://i.ytimg.com/vi/c-n92OgbbwA/mqdefault.jpg)
This is the best retro bike modernization ive seen to date, paint job ended up looking amazing as well
Couldn’t agree more 🎉
The bike is impressive, but showing your work is just next level. Well done video, and that bike is amazing. Well done.
Thank you!
As a structural engineer who loves tinkering with bikes this was right up my ally.
Did not expect the multiphysics analysis! Bonus. I’m doing this same thing to a Giant. Just welded up the brake tabs yesterday. I’m paying close attention to your work. Thanks,
Great video -- really impressed with the FEA!
You can buy pre made caliper mounts from several bike frame builder suppliers in the US. No need to mill your own.
I silver brazed mine and added a small gusset. I have over 3000 miles on the frame. No problems at all.
really impressed you bothered to run it in FEA software, way to go man
Well done. Impressive craftsmanship.
I’ve got a Brodie Catalyst that’s getting the gravel bike treatment …and this video is fantastic. Really liked the engineering to demonstrate that deflection under unrealistic loading is not even 0.2mm! Those are numbers I can live with. Subbed and thanks for your excellent work!
Very cool video, I appreciate the fact that you did some FEA to verify your choices, as that is what engineering is all about. I personally wouldn't do all the extra work of welding in a brace for a .5 increase in my safety factor, but I guess that depends on the frame one uses.
Great point!
Wow this is great! I was thinking about doing exactly this and to see that someone else has done it before me will be a great reference. Great work!
Appreciate it, thank you It was a fun and rewarding project. I'll bet yours will turn out great.
Just one thing to say, sickly amazing job!
Whenever someone comes into a forum and asks about converting a 90's MTB to disc brakes by welding in tabs, the top response is something along the lines of "you'll die". It always seemed hyperbolic to me, I'm glad you busted out the FEA on this. I'm wondering what the safety factor on something more modern is, particularly a more all-road frame as opposed to a downhill bike.
(deleted part of my comment, reading the linked studies now lol)
Good thing about bicycles is that you will always stop. How, is the real concern.
Wow, modifying old mtb frame WITH physics theory. Bravo my friend, sub'd!
I have to agree that the frame looks better than it would have with a brace, and I was one of those who questioned why you chose not to install one.
After watching this great explanation, it makes sense that the force applied is really negligible, especially with using a small diameter rotor (160mm). The force would have been higher if you had went with a 180mm, but that's not really needed on a road/gravel oriented bike on the rear.
About the need for a brace. I completely agree that your setup is fine. Steel frames are very strong, and also in practice the rear brake is only able to take maybe 1/3 of the stopping force before the rear wheel will skid - - physics. The more critical part is the front fork, but I'm assuming you just used a new disc-ready fork? Really cool build!
Appreciate it, thank you. Yep, you're spot on. This was a disc fork. I did adapt it for thru axles, but native disc.
This is a mod I've always wanted to do. Sadly, 90's MTB frames are scarce where I live. Looking forward to the Kona!
I’m excited for the Kona build. I got to buy a new rotary table just for that project. It’s going to be awesome.
good explanation about the brace, that's what I also said something about in the first video.
Right on
Nicely done sir. Wow great step description.
Thank you kindly!
Awesome. Very well explained. Just wish I could weld. Loved the FEA but I'm not a big fan as very minor changes in the boundary conditions can have huge effects on the answers. Love the thru-axles.❤👍👍👍👍👍
I just did a back-of-envelope calculation and I got a different force on the caliper.
Considering mu = 1 (dry asphalt, good tire) and rear tyre normal force Fz = 400 N, the stopping force is 400 N on the lever of 0.35 m (wheel radius). From the torque balance for the brake disc action radius (r= 0.07 m), that is 400*0.35/0.07 = 2000 N!.
Looking at the second paper, I see they use mu = 0.5 in which case your result seems plausible but their experiment is in pretty much laboratory condition. I would be afraid that that frame could collapse in that one emergency braking situation when your rear tire bites to a rock in the ground.
I am sure you will be fine on normal roads but I would think twice before riding some rougher trails.
Actually, that gives me an idea. What if I'd model the original cantilever brakes and see what forces those applied to the stays under the same conditions? It could serve as a good baseline. The only other idea I have is strain gauges on the rear stays but that is sure expensive and I'm 100% we'll get the same results.
@@RobertAdairWorkshop @RobertAdairWorkshop it surely would be interesting to reverse engineer the original design, just to put it into perspective with yours. But for rim brakes, the braking force might not even be the most significant one. For such thin tube I would definitely also consider the buckling load from your weight but and also from the forces from wheel into axle.
Using strain gauges could be a fun project that I thought about myself. You can get cheap ones from china including some arduino amplifier modules. But proper installation, processing the results and calibration could be frustrating.
If it was to me, I would simply lock the brake, try to turn the wheel to simulate the braking torque and observe closely the bending of the tube.
Btw how did you measure the thickness of the stay tube for your FEM model? Is it the same along the length of the tube? And also what UTS of the material do you use in the FEM?
Very nice work. I made a similar transformation but with an early 2000's alu bike that already had disk mounts.
The FEA analysis is interesting, but think I spotted a small mistake in the model. You seem to have defined the wheel axle as a rigid point, but it should be considered as a pivot. that way the seatstay should share some of the deformation with the chainstay, and show less difference between the braced and unbraced cases.
Wow! You are exactly right. I'm not quite sure how I missed that. Thank you!
Fantastic work 🎉
What a great video. The only thing for a "modern" bike would be internal cabling, which is very easy on that frame
I didn't even think about that. Hmmm. Next project, right?!
looking forward for that kona video 👀
man I'm inspired to try this now
Looking forward to the 2000 Hahanna!
Yeah! Waiting for the kona videos!
Congratulations on your bike, I liked how it turned out, I really like the on point methodology you explain to us about the FEA! Aluminum frames are another level to modify, right? I've got a cannodale m900 bike which is aluminum, same 90's built, it would be awesome if you could show us how to modify aluminum frames! Im not a welder myself but im eager to know how!
I did discs on an aluminum 1998 Stumpjumper last year. It was actually easier to do but you're kind of taking your life into your own hands with the brazing. ruclips.net/video/vD1pH86wCrU/видео.html
Nostalgia! I used that solidworks in college
Ha! That's where I learned it, too.
Fantastic video! Seriously an underserved subject on youtube a bike forums.
I did want to ask if you considered just brazing the bracket onto the stay? Brazing is accessible to more people (a MAP torch from home depot is way cheaper than a tig setup) and certainly strong enough to handle anything i can give it with my grip strength right? Wouldn't have to be as concerned about contaminating a weld and every step would be almost the same except for the filler material.
I think brazing it is probably the frame builders “correct way” to do it. I just never learned to braze so I’m sticking with what I know.
Totally get it! With the FEA and exceptional thoroughness of your video I assumed it was a strength calculation.
I wish I was setup for welding but brazing is super simple (except for the acetylene shortage ha). Getting filler rod of the right type is harder the torching metal until it starts wicking filler in.
Great video again and glad it popped up in my feed. Newly subscribed!
Superbe reconversion du freinage . Je suis sur le même projet sur un cadre acier LOOK . Peux-tu me renseigner sur le support choisi pour le montage de l'étrier . Superb braking conversion. I am on the same project on a LOOK steel frame. Can you tell me about the support chosen for mounting the caliper.
curious, the use IS (not iso) mount because it opens up the options for flat and post mount caliipers, good choice.
but the use of a what looks like maybe a IS to PM adapter (that adapter is huge) for a 203mm rotor to locate the mount for a 160mm rotor would remove the options of running flat mounts as the caliper won't be in the correct place.
surely using a adapter for 160mm rotor in the first place would of allowed the creation of a IS mount that would suit all brake styles. yes using the BB5 cable brake is good, but just use enough flat spacers under it to account for the CPS washers thoose things usually use.
Brilliant! I have one question: would a panic stop cause a peak power that could be higher, and would the calculated safety value cover this?
The 984N I calculated is for a situation worse-than a panic stop where there is no slippage. A panic stop would be less than that 984. The calculates FOS does cover max braking.
Then you. This is incredibly useful. Also, did you have to mill rear drop out to fit 12mm axle? I'm just about to get my self a classic gt or gary fisher. Cant waiiiit
I had to drill it out 12mm for the axle. If you're alright with me sharing a link to another video, check out the build video. I've started it at the timestamp for the thru-axle mods: ruclips.net/video/WDkYQHh_scU/видео.htmlsi=6kVaQ2sjjSYYOgUj&t=222
Dude, that's exactly what i want to do with an old frame i got.
But i'll try to stick weld it because its the only way i have to weld it, hahahaha.
Cool video, cool bike
I mig welded it because I don’t know how to braze. I totally got ya!
Last summer I put 27.5" wheels on a 26" frame because they fit and I wanted the bigger wheels. Being a bigger wheel, the whole bike got a bit taller and it felt like I was riding on a tower of a bike. Did you find that this bike felt really tall with the bigger than intended wheels?
Which fork do you have in mind for the Kona? Asking because I have a similar frame (steel, disc tab added), it's currently set up as a hardtail mtb, and I'm considering more of a gravel setup.
I’m using one made by Soma for their fog cutter frame. It’s a straight steerer carbon fork with flat mount caliper and 12mm thru axles. Fits the frame really well.
And now I’m on market place looking for a 90s mtb 😅😂
You're like Bob Ross. Was that a PAPR you were wearing during clear coat
It’s a Hobbyaire system I bought back in the early 2k’s to paint a 300zx. Still works great. Draws from filtered shop air.
Does that FEA package let you do a fatigue analysis?
No, sadly, this one is a bit too old to look at fatigue stresses. I’d like to have a modern version but the software is ridiculously expensive for one license. Maybe if I make it big on RUclips, I’ll celebrate with software.
🔥🔥🔥
3:40 but is that a 180 mm adapter with a 160 mm rotor? im confused
Looks like I have a project for my old gitchee gumee
Where did you get the rivet brake hose holders? :0
Amazon. Here's the basic link -> www.amazon.com/gp/product/B07DND33HV
I had to round the bottom of each with some sandpaper wrapped around a dowel, to get them to sit flat on the frame. I didn't show that in the video.
@@RobertAdairWorkshop Awesome, thanks! Ive welded tabs on an old schwinn and I'm excited to put these to use too
I used 203mm rotors in my conversion and I still don't understand why everybody uses 160mm, it is simply not enough for precise control on breaking
Hello there,
could you by any chance send me the 3D-Model of the frame you created for the video? Step or any other type would be fine, but SLDPRT highly appreciated, as I use SolidWorks myself.
Would be great and save me a ton of work.
It doesn´t have to be perfectly my own frame, but I need a model of a retro-mtb-frame for an upcoming project. It would be great, if you could help me out on that.
Kind regards
Viktor
(btw. If it if it makes a difference to you: I did not just find your channel while searching for a 3D-Model, but am an active viewer, and just remembered, that you made this model in this video before starting to create my own one)
Hey! I'd be happy to send you the Solidworks file for the frame. Send me an email and I'll attach it to my response. Its in SolidWorks 2006 so hopefully it'll still be compatible.
Max tire size?
700c x 40. I talked about it in the original build video. That gives 8mm at the stay bridge. ruclips.net/video/WDkYQHh_scU/видео.htmlsi=dsn5uc-Sn0hriI5d&t=1179
@@RobertAdairWorkshop oh. Yes thanks. So 40c on a wide 27internal rim would be the frames max. That would probably bulge it out to 41 or almost 42.
Ever thought about putting in some 42c ? Or would that be bad for your type of riding in muddy areas?
Dang man it sounds like you could tweak your compressor settings a little, seems like the first word of your sentences is getting cut off, anyhow great stuff!
Probably the noise reduction I use to try and cut down on the background noise from my workshop heater. I didn't notice til you mentioned it. I'll see what I can do for the next one.
Very impressive. I wish there was an easy way to properly face brake mounts and tabs. For the home mechanic the tools are out of reach.
9:23 here you go ,physics enjoy everyone
Ha!
I wish I was your neighbor!
You might be if you live in Denver, Colorado.
@@RobertAdairWorkshop Rural Maine for me! Thanks for the videos, keep up the good work 👍
Converting from rim brakes to disc brakes is really dangerous due to the different forces exerted on the frame. It can e. g. easily lead to fork failure.
I don't think you watched the video. Look at 8:52. I talk about, just that, for at least 5 minutes.