Tube Sizing for 180mm Freeride Bike- Mtbr.com
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  1. #1
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    Tube Sizing for 180mm Freeride Bike

    Hello all,

    My high school requires a senior project and I have decided to design and build a mountain bike frame.

    I want to build a bike similar to my Santa Cruz Bullet 1, but made out of steel because I don't want to deal with the tempering of the aluminum after it is welded, and modernized (thru-axle, tapered head tube, 27.5inch, etc.). I will not be welding the bike, I will have a welder do it. I do have a 3-axis CNC machine for making parts if needed.

    Now my question. Bullets are single pivot with both the pivot and the upper shock mount in the down tube which will add a lot of force to it while riding. I have researched what size/thickness of tube for the down tube but no one has made a 180/180mm steel freeride bike so I don't know what kind of tube to use. I would prefer one with a large diameter because it makes the bike look stronger (my current Bullet has around a 47mm down tube) but that might make the bike too heavy. What size/thickness of tube should I use?

    I want to know now so that I can use the right sized tubes while making a 3d model.

    Thanks for any help!

  2. #2
    pvd
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    This project is too large a scale for you.

    Try a more simple project and do proper documentation for it.

  3. #3
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    Good to see that Mr. Helpful is right on cue to offer some guidance.

    Walt is good at dishing out advice. I canít find the thread I really want, as he goes more into detail on his reasoning as to what and why. This has some info on it.

    https://forums.mtbr.com/frame-buildi...r-1076824.html

  4. #4
    pvd
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    Quote Originally Posted by Cord View Post
    Good to see that Mr. Helpful is right on cue to offer some guidance.
    A bit of knowledge and experience are needed to recognize good advice from bad. This makes it hard for the beginner as they don't know who to listen to, but they can learn.

    Actually, you're not a bike expert | Peter Verdone Designs

  5. #5
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    Quote Originally Posted by pvd View Post
    A bit of knowledge and experience are needed to recognize good advice from bad. This makes it hard for the beginner as they don't know who to listen to, but they can learn.

    Actually, you're not a bike expert | Peter Verdone Designs

    Absolutely exactly correct. I am not an expert, and have never claimed to be one. I pointed him towards Walt who not only has a good amount of experience, but is also prepared to explain why he suggests certain things. Certainly a good point to start compiling information.

    As you yourself have not offered any info, am I correct in my assumption that you must not consider yourself an expert either?

    Maybe you could help answer the original posters question and point him towards an expert who may be willing to advise on tubing?

  6. #6
    pvd
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    I'm an expert. Regarding school projects and bicycles.

    I work at a large US University. I advise and instruct faculty and students here on the engineering and construction of various projects in the STEM (COSE) College. Both instructionally and in research groups. I know what most students are capable of and the ladder that they need to climb for success.

    This is no project for a high school student or even a University project unless in a good group of over achievers. The student should cut the scope of their project way back, do something more manageable, and focus on modeling, drawing, and engineering documentation if they are looking for a real learning experience and success.

    So, again, it's hard for a non-expert to recognize expert advice.

  7. #7
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    Quote Originally Posted by pvd View Post
    I'm an expert. Regarding school projects and bicycles.

    I work at a large US University. I advise and instruct faculty and students here on the engineering and construction of various projects in the STEM (COSE) College. Both instructionally and in research groups. I know what most students are capable of and the ladder that they need to climb for success.

    This is no project for a high school student or even a University project unless in a good group of over achievers. The student should cut the scope of their project way back, do something more manageable, and focus on modeling, drawing, and engineering documentation if they are looking for a real learning experience and success.

    So, again, it's hard for a non-expert to recognize expert advice.
    Well done, see, it wasnít that hard to actually offer up some information. Your starting to get the hang of this whole question/answer scenario.

    As you said earlier, I wonder if this ďbeginnerĒ will now be able to find it easier to decide who to actually listen to.

  8. #8
    pvd
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    I have 20 years of projects and content on my website and thousands of message board discussions participated in. All written in long form and showing the math, the drawings, and rationalizations. Your attitude is ignorant of that as this is all new to you.

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    Far from ignorant. I realised youíd been doing this for a long time, hence why on several occasions I had directly asked for you input. Iíd love to be able to peruse through 20 years of maths and data on some of these subjects that would help me enormously.

    With you being an education expert Iím intrigued by your methodology of simply saying to either Ďnotí or to Ďdoí something. I was educated in a far different way, I was taught the reasoning behind why I should or shouldnít do something and that helped greatly to grow my knowledge base. Iím glad you are training the experts of tomorrow. It makes me have confidence in the future.

    Anyway, I think I may be dragging this topic severely off topic.

  10. #10
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    Quote Originally Posted by pvd View Post
    I'm an expert. Regarding school projects and bicycles.

    I work at a large US University. I advise and instruct faculty and students here on the engineering and construction of various projects in the STEM (COSE) College. Both instructionally and in research groups. I know what most students are capable of and the ladder that they need to climb for success.

    This is no project for a high school student or even a University project unless in a good group of over achievers. The student should cut the scope of their project way back, do something more manageable, and focus on modeling, drawing, and engineering documentation if they are looking for a real learning experience and success.

    So, again, it's hard for a non-expert to recognize expert advice.
    Whether or not you think I could pull off a project like this based on your vast knowledge of who am is not what I asked.
    I just wanted some numbers so that I could make a 3d model.

    It is required that I have a meeting with a mentor for the project and I live in the north end of northern California so I could use someone who is involved with the frame building school in Ashland, Oregon as a mentor (about 50m drive).

    And if the bike breaks first ride, so be it. At least I will have gained some experience, had some fun, and gotten my senior project done.

    Edit: Sorry I didn't reply, thought I would get email notifications but didn't

  11. #11
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    Why not start with a hardtail? It's a vastly easier project but still challenging for someone who has never designed and built a frame before.

    You can still use your fancy CNC machine to make your own dropouts, chainstay yoke, braze-ons, and head tube.

    If you go with a hardtail and a more modern geometry, most builders use a 38.1mm down tube with at least .9/.6/.9mm butted walls. Nova Cycle Supply carries a nice tube for that application.

    The challenge for most mountain bike builders is getting enough tire clearance at the chainstays. Designing a CNC milled yoke would be a really fun part of the project. PVD makes his own and his latest design is really nice. Adam Sklar makes his own too. You can also look at Paragon Machine Works and Oakes MFG. for commercial options.

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    Quote Originally Posted by nrj View Post
    Why not start with a hardtail? It's a vastly easier project but still challenging for someone who has never designed and built a frame before.

    You can still use your fancy CNC machine to make your own dropouts, chainstay yoke, braze-ons, and head tube.

    If you go with a hardtail and a more modern geometry, most builders use a 38.1mm down tube with at least .9/.6/.9mm butted walls. Nova Cycle Supply carries a nice tube for that application.

    The challenge for most mountain bike builders is getting enough tire clearance at the chainstays. Designing a CNC milled yoke would be a really fun part of the project. PVD makes his own and his latest design is really nice. Adam Sklar makes his own too. You can also look at Paragon Machine Works and Oakes MFG. for commercial options.
    I'll think about it. I would rather make a full suspension though since my favorite trails in my area aren't rideable on a hardtail.

    Additionally, I would enjoy coming up with the suspension design so that it performs well. I found this nice website, https://www.shimrestackor.com/, that has a lot of good information about suspension designs and how to make one that performs well.

  13. #13
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    Quote Originally Posted by FINN ANDERS View Post
    Whether or not you think I could pull off a project like this based on your vast knowledge of who am is not what I asked.
    I just wanted some numbers so that I could make a 3d model.

    It is required that I have a meeting with a mentor for the project and I live in the north end of northern California so I could use someone who is involved with the frame building school in Ashland, Oregon as a mentor (about 50m drive).

    And if the bike breaks first ride, so be it. At least I will have gained some experience, had some fun, and gotten my senior project done.

    Edit: Sorry I didn't reply, thought I would get email notifications but didn't

    As I said, have a hunt through Waltís posts thereís was a little info on the 1 I linked, but heís definitely gone more in depth in the past.

  14. #14
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    If you couldn't find the info online to answer your question you're not ready to built it.

    ALL the info you need is buried deep in this forum. If they aren't teaching you how to do the initial research they you are missing a critical step.

  15. #15
    pvd
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    Good judgement comes from experience.
    Experience comes from bad judgement.

    If you want to build a full suspension, build one. There's a good chance it won't be that great. But you will have gained a lot of experience and found one way not to build a bike. Lots of research will go a long way to helping you sort out all the ideas that really won't work, however at some point you have to build something and try it.
    If you have never built a bike before or don't have a lot of fabrication experience, a hardtail is a great place to start. There are so many variables that influence how a bike rides and fits, it will take many, many hours just to figure out what you want to build. Again lots of research.
    When you throw full suspension into the mix, you are opening a whole new can of worms. Not only do you have to know what it takes to build a great riding bike, but you also have to know how to build great riding suspension. This opens you up to a whole new set of variables to screw up. Lots and lots and lots of research required here.
    If you are up to it, go full suspension. However, be realistic with your expectations. It may not be that awesome. If all you want to do is fulfill the requirements for your senior project, it will be fine for that. If you want to build a bike that really rides well, you will likely have better results with a hardtail.

  17. #17
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    A full suspension frame that requires engineering, industrial design, and manufacturing seems way overkill for a high school project.

    If you plan to take tubes to a welder - what is the welder going to use as a fixture?

    If you're going to CNC parts, who is going to build the tooling?

    What if you turn this into a design project and make the final product just a mockup? You can then 3d print a lot of the parts, or use the CNC with a soft material. For the tubes use anything about the right outside diameter and epoxy it all together. Or design it as if it was going to be a carbon frame and build it from foam/plywood/bondo.

    The typical n00b mistakes are forgetting stuff like chainring clearances and ending up with something unrideable. Why not start with something that can't be ridden anyway but use materials that are a lot cheaper to make and easier to modify when you make the inevitable mistakes? This also makes your fixturing needs super easy, nothing you can't build with some scrap wood and deck screws.

  18. #18
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    Quote Originally Posted by FINN ANDERS View Post
    Hello all,

    My high school requires a senior project and I have decided to design and build a mountain bike frame.

    I want to build a bike similar to my Santa Cruz Bullet 1, but made out of steel because I don't want to deal with the tempering of the aluminum after it is welded, and modernized (thru-axle, tapered head tube, 27.5inch, etc.). I will not be welding the bike, I will have a welder do it. I do have a 3-axis CNC machine for making parts if needed.

    Now my question. Bullets are single pivot with both the pivot and the upper shock mount in the down tube which will add a lot of force to it while riding. I have researched what size/thickness of tube for the down tube but no one has made a 180/180mm steel freeride bike so I don't know what kind of tube to use. I would prefer one with a large diameter because it makes the bike look stronger (my current Bullet has around a 47mm down tube) but that might make the bike too heavy. What size/thickness of tube should I use?

    I want to know now so that I can use the right sized tubes while making a 3d model.

    Thanks for any help!
    So, take this as you will.


    I've built about a dozen frames, but no suspension ones. I can easily answer your question, dive in to the tradeoffs between the alternatives, and offer material sources and reference material, but i don't think that serves your interests. It's a painfully basic question that speaks to unpreparedness. I don't know enough to build a worthwhile FS bike, and i'm a lot more experienced than you. Walk before you run.


    If you're interested in frame design, build a hardtail, a rigid bike, or a road bike. Come up with some super-solid fixturing so your frame comes out with excellent, repeatable alignment. Figure out where the butts are going to lie relative to the bosses and cable guides. Think about how the frame will flex, both laterally and vertically. Figure out each tube and have a reason for why you selected that tube over all the others in the market. Map out your cockpit so it's fkn awesome, develop fit theory that can be applied to your next design. All that boring shit MATTERS: it's even more important than hardtail vs FS. Maybe build a hardtail so you can realize that they can be ridden virtually anywhere. Heck, if you can't smash on a hardtail... can you really ride?

    Professionals admire a simple job that has been done RIGHT. ...but there's something to be said by making a couple rolling disasters. That's how i learned. In my experience, you're gonna make some bonehead idiotic design/build decisions even going down the most trodden path.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

  19. #19
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    I'm not the most experienced builder, but I'm working on my own F/S design. For a 180mm freeride bike made from steel, I would use a 44mm straight gauge down tube. Just so you finally have an answer to your question.

  20. #20
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    don't mind pvd, he's just a bitter old shithead that doesn't like anyone but himself making bicycles.

    i have no input on tube sizing, but it sounds like a fun project/experiment. i'd just build it for eye candy as i'd never trust a bike i built to be ridden without it hurting me in some way..


  21. #21
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    Quote Originally Posted by .WestCoastHucker. View Post
    don't mind pvd, he's just a bitter old shithead that doesn't like anyone but himself making bicycles.

    i have no input on tube sizing, but it sounds like a fun project/experiment. i'd just build it for eye candy as i'd never trust a bike i built to be ridden without it hurting me in some way..
    Mr. Hucker,

    You really have me at a disadvantage. You're here posting anonymously and I am not. Could you let us know who you are IRL and where we can look at the work you've done that support the things you're saying about me? I doubt that you want to be known as the type that has to hide while saying things about others.

  22. #22
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    my name is Mike Henderson. to support what i say about you, all one needs to do is look at your less than helpful, condescending, self hyping posts that you continuously spout off. i never claimed to know anything about frame building, but i don't need to know anything to be able to tell that you are a wanker of the next level that should just be ignored...


  23. #23
    pvd
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    Quote Originally Posted by .WestCoastHucker. View Post
    My name is Mike Henderson...
    Ok Mike.
    Since you don't know much about bicycle, and come to a message board about bicycles, claim who shouldn't be listened to, insult them, and basically make a fool of yourself...We all know who the problem person is. Why don't you leave? You have nothing to offer here but insults. I'm busy sharing knowledge and helping people. You're acting a fool. ...and grow the f up.

  24. #24
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    Quote Originally Posted by pvd View Post
    ...I'm busy sharing knowledge and helping people..
    LOLZ!

    "your design is wack, read my website" ; "full suspension is stupid, go rigid. read my website" ; "i've made more bikes than you, read my website" ; 'your class project will fail, read my website"

    yeah, sounds like quality knowledge and help right there...


  25. #25
    pvd
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    You didn't go to the website.

  26. #26
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    of course not. you are already useless here. i couldn't imagine why anybody would willingly go read your worthless drivel somewhere else...


  27. #27
    pvd
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    Wow. You really are a scumbag. Get a life.

    Anyway, this is what I did in the past few hours:

    Move fast and break things | Peter Verdone Designs

  28. #28
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    you're funny and you don't even try. it makes it so much better for the rest of us...


  29. #29
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    Hilarious, I wouldnít have gone quite as far as a sh1thead. However, Iíve been there before, you can read about it on my website!!!!

  30. #30
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    Ugh.

    Heyyy FINN ANDERS, I'm not sure if you're even reading this thread anymore. Just in case you are, I'll leave this here:

    Firstly, google for "Dave Camp homemade gearbox bike" - and take stock that a teenager can indeed make a full suspension bicycle that is well outside the norm and have it work.

    However, where you're going wrong here is your wording of "but that might make the bike too heavy". The advice you've received so far has been a mixture of "don't try" vs "it's too much for you" vs "you will fail". Some of this is from an ineffective desire of grizzled old frame builders wanting to prevent you from wasting your money. To that I say, you can always make more money, you're going to be doing so for like your whole life.

    The key thing here is "but that might make the bike too heavy" -- it's okay to want to do an ambitious first build. But to make an optimized first build? Even the experienced professionals cannot achieve this. If you want to show me someone who got the version 7 build done on the first try, I'll show you a liar.

    Point being: make yourself a heavy ass bike. You wanna get hurt over making a bike frame? Resewing bones sucks. Save the weight optimization for later.

    As for PVD, his website does have useful info on it, but you have to wade through a lot of sneering. Wanna know something kinda horrifying? I've worked closely with people who are trash talking superiority complex than this dude. Like I'm not trying to give him a pass, because he does this a lot, but, there's, you know, worse people out there, and somehow they remain gainfully employed. You have to go really, really far down the rabbit hole of extreme rudeness to become totally useless. I know because I'm related to one of them!
    Disclaimer: I run Regular Cycles (officialy in 2016, functionally in 2020).

  31. #31
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    Quote Originally Posted by dr.welby View Post
    A full suspension frame that requires engineering, industrial design, and manufacturing seems way overkill for a high school project.

    If you plan to take tubes to a welder - what is the welder going to use as a fixture?

    If you're going to CNC parts, who is going to build the tooling?

    What if you turn this into a design project and make the final product just a mockup? You can then 3d print a lot of the parts, or use the CNC with a soft material. For the tubes use anything about the right outside diameter and epoxy it all together. Or design it as if it was going to be a carbon frame and build it from foam/plywood/bondo.

    The typical n00b mistakes are forgetting stuff like chainring clearances and ending up with something unrideable. Why not start with something that can't be ridden anyway but use materials that are a lot cheaper to make and easier to modify when you make the inevitable mistakes? This also makes your fixturing needs super easy, nothing you can't build with some scrap wood and deck screws.
    I am going to put all of the tubes in a jig made with a large piece of MDF like this guy: https://forums.mtbr.com/frame-buildi...r-1076824.html. Then I will bring it to the welder, in the jig, and have the welder tack weld it. Once the frame is stable, he can weld the whole frame, off of the jig.

    Who is going to build the tooling? My dad can help me do that. Probably won't be very efficient, but it'll work.

  32. #32
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    Quote Originally Posted by jsudar View Post
    I'm not the most experienced builder, but I'm working on my own F/S design. For a 180mm freeride bike made from steel, I would use a 44mm straight gauge down tube. Just so you finally have an answer to your question.
    I was thinking about using 1-5/8" straight gauge, but I am open to using 1-3/4" (≈44mm). My only concern would be the weight, but once I finish the 2D model I will calculate (roughly) how much the frame will weigh and see if it weighs too much.

    Quote Originally Posted by Drew Diller View Post
    Ugh.

    Heyyy FINN ANDERS, I'm not sure if you're even reading this thread anymore. Just in case you are, I'll leave this here:

    Firstly, google for "Dave Camp homemade gearbox bike" - and take stock that a teenager can indeed make a full suspension bicycle that is well outside the norm and have it work.

    However, where you're going wrong here is your wording of "but that might make the bike too heavy". The advice you've received so far has been a mixture of "don't try" vs "it's too much for you" vs "you will fail". Some of this is from an ineffective desire of grizzled old frame builders wanting to prevent you from wasting your money. To that I say, you can always make more money, you're going to be doing so for like your whole life.

    The key thing here is "but that might make the bike too heavy" -- it's okay to want to do an ambitious first build. But to make an optimized first build? Even the experienced professionals cannot achieve this. If you want to show me someone who got the version 7 build done on the first try, I'll show you a liar.

    Point being: make yourself a heavy ass bike. You wanna get hurt over making a bike frame? Resewing bones sucks. Save the weight optimization for later.

    As for PVD, his website does have useful info on it, but you have to wade through a lot of sneering. Wanna know something kinda horrifying? I've worked closely with people who are trash talking superiority complex than this dude. Like I'm not trying to give him a pass, because he does this a lot, but, there's, you know, worse people out there, and somehow they remain gainfully employed. You have to go really, really far down the rabbit hole of extreme rudeness to become totally useless. I know because I'm related to one of them!
    I agree with what you're saying. If the bike weighs a lot, I'll just save up my money for some light parts.
    I prefer to just ignore the arguing.

  33. #33
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    Quote Originally Posted by FINN ANDERS View Post
    I am going to put all of the tubes in a jig made with a large piece of MDF like this guy
    Cool, sounds like you have a good plan.

    For tubing, if you look at some of the off-the-shelf downtubes the thicker stuff is 0.9mm wall thickness, with a couple burlier tubes going to 1.0 or 1.1 mm.

    For plain gauge, you can get 0.035" which is just under 0.9mm, or 0.049", which is about 1.25mm.

    So if you build the prototype with 0.049" tubing that puts you on the safe side.

  34. #34
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    Quote Originally Posted by FINN ANDERS View Post
    I am going to put all of the tubes in a jig made with a large piece of MDF like this guy: https://forums.mtbr.com/frame-buildi...r-1076824.html. Then I will bring it to the welder, in the jig, and have the welder tack weld it. Once the frame is stable, he can weld the whole frame, off of the jig.

    Who is going to build the tooling? My dad can help me do that. Probably won't be very efficient, but it'll work.
    3D printed tube supports/vee blocks etc,, work very well. They wonít hold up to much abuse, but good for a 1 off. Iím hoping this frame becomes a reality, as much to get your project done, as to silence the nay-sayers on here. Itís not rocket science, itís basic fabrication.

  35. #35
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    Quote Originally Posted by Cord View Post
    Iím hoping this frame becomes a reality, as much to get your project done, as to silence the nay-sayers on here. Itís not rocket science, itís basic fabrication.
    +1

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    Tube Sizing for 180mm Freeride Bike

    Quote Originally Posted by FINN ANDERS View Post
    Whether or not you think I could pull off a project like this based on your vast knowledge of who am is not what I asked.
    I just wanted some numbers so that I could make a 3d model.

    It is required that I have a meeting with a mentor for the project and I live in the north end of northern California so I could use someone who is involved with the frame building school in Ashland, Oregon as a mentor (about 50m drive).

    And if the bike breaks first ride, so be it. At least I will have gained some experience, had some fun, and gotten my senior project done.

    Edit: Sorry I didn't reply, thought I would get email notifications but didn't
    Numbers: Use anything from 1.5Ē to 2Ē OD for the main triangle @ 0.035Ē wall. And something smaller, like 0.5Ē-0.875Ē for the rear. You probably wont be able to find a wall thickness too thin for the smaller tubes, but donít go under 0.020Ē. This is all 4130. And you donít have to use 4130 welding rod - as a matter of fact donít unless you want to bake the whole thing. Just use mild steel rod with the 4130 tubes and youíll be fine.

    Now GO! And donít forget proper documentation is whatís separated the good engineers from the bad. Itís not all Solidworks and endmills!!

    EDIT: and donít forget to test some of your welds. Make a few samples and make sure they hold at least 750 pounds. On tubes greater that 1Ē. Design a test fixture and put that in your project - safety first.

  37. #37
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    Quote Originally Posted by dr.welby View Post
    Cool, sounds like you have a good plan.

    For tubing, if you look at some of the off-the-shelf downtubes the thicker stuff is 0.9mm wall thickness, with a couple burlier tubes going to 1.0 or 1.1 mm.

    For plain gauge, you can get 0.035" which is just under 0.9mm, or 0.049", which is about 1.25mm.

    So if you build the prototype with 0.049" tubing that puts you on the safe side.
    I'm not positive .049 is really that conservative. On the rare occasion i've gotten to measure/read about established FS steel framebuilders' design, it's always >1mm wall thickness on the downtube. Especially if the shock attaches to it- that adds a whole extra dimension where overbuilding is cheap insurance.

    Weight weenieing is fine when you have a proven, excellent design. It's stupid to go there first though.



    I had an OG canfield balance. 2007? Steel front triangle, alu rear. 12.8lbs. Too much shock progression. I broke it on a big flat drop.

    Still bummed about that. It wasn't the 'best bike,' but it was so much fun for exploring desert terrain. Better than modern stuff.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

  38. #38
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    100% go for it! I built my bike while I was in engineering school. It was a lot to take on with all my class work, but if you keep plugging away and work a couple long nights you will get it done.

    Some tips. If you stay with a full suspension design I would use strait gage tubing for your first frame. I used 0.039" wall for most of the frame other than the top and bottom of the seat post, I used 0.058" wall. This was to give more strength for the main pivot and the seat post. Aircraft spruce has good pricing on 4130 tubing. I did as you said with my jig, I tacked the tubes in the jig then took it out and fully welded it. I found a local frame builder to put it on his alignment table for straightening and to my surprise it only needed minimal straitening. If you haven purchased Linkage X3 I would highly recommend purchasing it.

    My build thread was linked a few times in here. If you missed it there was a link in there to a report I wrote for some class credit. This was not my capstone design project so it does not go to in depth about the design, but it has some useful information and includes all the build photos. Here is the link. Good Luck!

    https://docs.wixstatic.com/ugd/1196f...74b5863a38.pdf

  39. #39
    pvd
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    This is very very good work. Definately worth reading for anyone. In a quick survey, you describe the trail of a kanted head axis incorrectly but otherwise the rigor is good.

  40. #40
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    Thanks PVD, I appreciate the feedback. I'll look into it.

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