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  1. #1
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    Super Slack 29er Hardtail Build - possibly 3D printed titanium lugs and carbon tubing

    Hi all, with a bit of luck ill be able to make a 29er hardtail.

    Im taking inspiration from the Nicolai Argon AM, Kona Honzo Ti and Last Fast Forward.

    Heres my current geometry, any input would be greatly appreciated as this is the first time ive tried this.

    Super Slack 29er Hardtail Build - possibly 3D printed titanium lugs and carbon tubing-zkbyr9q.jpg

    Super Slack 29er Hardtail Build - possibly 3D printed titanium lugs and carbon tubing-brm65cc.png
    I forgot 'M', its 120mm.

    the rear axle is going to be a 12mm bolt thru. im kinda tempted to go single speed, but the sliding drop outs would weaken the rear end quite alot. Theres a few places that im toying with putting a gusset as well.

    Heres is an accurate CAD model of the frame with the above geometry. its parameterised so I can very quickly reproduce it with different geometry:

    Super Slack 29er Hardtail Build - possibly 3D printed titanium lugs and carbon tubing-apxx8to.jpg
    edit - updated image, this is the correct geo.

    my plan is to 3D print some titanium lugs then use carbon tubes for the rest. its a bit of a long shot, but its on the cards so im going all in and preparing the CAD for it.
    Attached Thumbnails Attached Thumbnails Super Slack 29er Hardtail Build - possibly 3D printed titanium lugs and carbon tubing-xaris4p.jpg  

    Last edited by isotropic; 08-10-2016 at 02:19 AM.

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    Definitely will be watching this with anticipation! What machine are you using for the Ti printing? Been curious to look into that process more as its super interesting to see where it'll take bikes in the coming years....

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    Well, it'll certainly be long and slack. For my money you get big time diminishing returns on hardtails doing that sort of geometry, but trying new things is fun!

    Come back and update when you have some actual physical stuff made!

    -Walt

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    What machine are you using for the Ti printing?
    the printer is a concept laser m2 with all the swings and whistles.

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    So, the reason I was going hardtail was because I had extremely limited time to get the project done. But that might not be the case. Problem is, i can only afford about 1.5kg of titanium. after checking the approximate weight of the CF tubes, they are weighing in at 0.7kg give or take. total frame weight would be 2.2kg.

    question is, can i stretch it out and go full suss (less aggressive trail bike)? if i machine the linkage out of ali, i think it may be possible? any other ideas on how i can spread the material?

  6. #6
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    Save up more money and do it the way you want with the materials you want.

    Or build it with steel or aluminum and just machine/weld everything.

    Or just buy a bike and go ride.

    -Walt

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    Quote Originally Posted by Walt View Post
    Save up more money
    this is the problem, im not spending my money on the printing. i effectively have a printing budget, and ive got 1.5kg (give or take) left in it which needs to be used. i cant actually get more money in there, but its also completely free, i just have to cough up for the carbon tubes and a few bearings.

  8. #8
    pvd
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    For a rider of your size, your geometry looks tiny, almost micoscopic. It would help to design a mountain bike to not think about head angle so much. Bikes aren't slack because that's the goal, it's the result. You should really start looking more at how you sit on the bike rather than Pink Bike reviews.

    I'm 5'10" tall. Here's a print of the bike (Concorde) I'm welding up right now. Should be pretty dialed over RedFive.

    Back to the drawing board | Peter Verdone Designs


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    Quote Originally Posted by pvd View Post
    For a rider of your size, your geometry looks tiny, almost micoscopic.
    right you are, two mistakes in the CAD model image i uploaded, new one can be found here (cant up link images at the moment?)

    Imgur: The most awesome images on the Internet

  10. #10
    pvd
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    It may be time for you to learn how to dimension a bike frame. Take a look at my prints for reference.

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    you mean add dimensions to the CAD drawing? im running it off a script in Rhino and adding dimensions isnt an option, and if it is, its a ball ache. its the same dimensions as the specification in my first post (give or take a few mm). I only added it for visual reference really.

  12. #12
    pvd
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    If this is a "ball ache" for you, making a frame isn'tisn't really going to work out well for you. Sorry.

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    So because the CAD package he's using can't automatically generate dimensions on a drawing, he can't make a frame? OK it might make it a bit tricky when he's cutting and mitering, but for christ's sake how many millions of frames were made before CAD was a thing? [sarcasm]Your input is as helpful as ever PVD.[/sarcasm]

  14. #14
    pvd
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    Quote Originally Posted by Joe Nation View Post
    So because...
    I don't know who you are 'Joe Nation', but the wonderful world of making stuff is full of challenges. If Isotropic can't chose a decent cad program to work with at first or be bothered to change modes when his first bad choice becomes apparent and pointed out, then it is telling of his ability to bring a project through to completion.

    Also, designing a frame without parametric CAD is for idiots. People did without it in the stone ages but these days there is no excuse for working without it. Folks that build bikes without CAD today are just clowns.

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    Quote Originally Posted by pvd View Post
    I don't know who you are 'Joe Nation', but the wonderful world of making stuff is full of challenges. If Isotropic can't chose a decent cad program to work with at first or be bothered to change modes when his first bad choice becomes apparent and pointed out, then it is telling of his ability to bring a project through to completion.

    Also, designing a frame without parametric CAD is for idiots. People did without it in the stone ages but these days there is no excuse for working without it. Folks that build bikes without CAD today are just clowns.
    Wow, are you always this big of a prick? Or just when you need to feel better about yourself?

  16. #16
    pvd
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    What are you talking about?

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    Quote Originally Posted by pvd View Post
    What are you talking about?
    Do you really have that little self awareness?

  18. #18
    pvd
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    ???

  19. #19
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    If Isotropic can't chose a decent cad program
    As i said, im using Rhino which is considered one of the best packages for scripting models. Its hugely powerful and can produce NURBS surfaces like its nobodies business. If you havent heard of one of the larger names in CAD, maybe you arent in a position to pass comment?

    designing a frame without parametric CAD is for idiots
    I clearly said I was using a parameterised model, the bike model also has well in excess of 200 parameters. Also, there isnt really such a thing as non-parametric CAD. you can use a CAD package and ignore the parameterisation, but it is still there.

    Back to why im not putting dimensions on the images, because it is apparently causes you great concern. Im scripting this model (as i said before), which means i use a script to control the geometry, as opposed to using the GUI which i assume you use. This means i can very quickly alter the frame geometries and generate a huge number of geometries using the script. This has advantages because it opens up design optimization. However its significantly more difficult, in fact my bike script is 5000+ lines of code already and im only about 60% of the way through.

    Now, Rhino doesnt have a decent dimensions command within its scripting capabilities, because why would you want it? all the parameters, or dependent parameters can be listed or saved as a file, which i opted to do. theres nothing wrong with that. i could go through afterwards manually adding the dimensions, but that sort of defies the point of using a script to quickly generate the geometry, also it doesnt offer anything more than using the table (like the one in my first post). i could however write my own function that adds a better dimension, but thats incredibly difficult, and tedious, a ball ache if you were...

    be bothered to change modes when his first bad choice becomes apparent and pointed out
    not really sure what youre getting at here? you didnt like my frame geometry and i didnt change it when i posted the second image? all i wanted to do was show the image of the proposed geometry (a few tweaks but nothing significant) in the first post.

    Bikes aren't slack because that's the goal, it's the result.
    well actually, i think the slack head tube angle is an important feature of the bike as it allows for more aggressive riding. alot of frames are flaunting their angles. most importantly, in my mind a slack head angle like this will make the bike more fun, which is my objective.

    Finally, you make massive assumptions then act on them, its irritating and makes you look like a muppet. you seem to be on a really high horse aswell.if you cant sort your game out, maybe just dont post in this thread?
    Last edited by isotropic; 08-10-2016 at 04:22 AM.

  20. #20
    pvd
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    Isotropic.

    You sound like a computer programmer. Having skill with 'scripts' isn't what is needed to make a good bike.

    1. If you can't make a clear dimensioned drawing of your design, none of this is important.
    2. You should spend some time learning about geometry if you are looking at designing this sort of thing. I've done it. I have several examples on my site. You ignored that when you could have inquired.
    3. You should learn more about CAD and drawing. It really is important.
    4. Refering to marketing materials and magazines in a discussion on 'head angle' is silly. You are just parroting. Why not learn about it if your 'design' revolves around it. It would shock you to know that I'm doing everything i can to make my heads as steep as I can in my design, not the other way around.

    I could go on but this project is really going nowhere.

    I'll include this as you won't bother reading it anyway.

    Bits of advice for the aspiring framebuilder | Peter Verdone Designs

  21. #21
    pvd
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    Also, you don't seem to remember when we were using boolean CAD programs. Or you weren't there.

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    Quote Originally Posted by pvd View Post
    I could go on but this project is really going nowhere.
    Whose project is this exactly? I mean, is it yours? Sure seems like you think it's yours. For someone that is ostensibly in here to help people with their projects, you are awfully confrontational and show...oh about zero willingness to accept that someone dare do anything different than the way you think it should be done.

    I have NO idea how many decent suggestions or ideas you have as everything you post on this thread is couched in this terrible attitude of 'You're a ****ing idiot'. Just how exactly do you expect anyone to listen to anything you have to say when every single thing you say is wrapped in negativity?

    I LOVE reading the threads in here as it is very interesting to learn about frame building, even if I don't see doing so in my near future. And it sure seems like you have a huge amount of expertise to share.

    Sure would be nice if you'd lighten up, accept that there are more than one way of doing things, and god forbid, allow for the fact that people have been successfully designing and engineering ALL SORTS of things for HUNDREDS OF YEARS without CAD...let alone your specific flavor and workflow processes.

    But until you drop the attitude, you are right, no one will bother reading anyways. That's no one's fault but your own though.

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    You sound like a computer programmer. Having skill with 'scripts' isn't what is needed to make a good bike.
    Actually im a mechanical engineer, work in modelling. These parameterised models comprise a large amount of my work.

    you keep going back to my CAD skills, but youre the one who seems to be lacking in CAD knowledge.

    Also, you don't seem to remember when we were using boolean CAD programs. Or you weren't there.
    this is my favorite part, what with Rhino still using boolean operations... maybe you should gen up on your knowledge.

    youre also still caught up with that diagram. i wouldnt of posted another mock up if it caused this much of a stir. my dimensions are clear as day. in my first post (which all of this is an amendment to) you can see a diagram which specifies dimensions. there is also a table with the dimension values in. its not hard is it?

  24. #24
    pvd
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    It's that your 'drawing' shows that you have a complete lack of understanding of bicycle design. Using fancy surfacing techniques and additive manufacturing won't fix that.

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    im kinda enjoying this, i dont know why.

    Using fancy surfacing techniques
    what do you mean?

  26. #26
    pvd
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    Dude. You're using Rino and talking about NURBS but cant produce a simple drawing or layout. Your geometry doesnt sound to be based on any reason but you know 'scripts'. And this will be 3D printed in Ti but your model doesnt take any advanage of that and you cant produce a proper 2D print.

    This isn't the work I'd expect from a mechanical engineer.

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    Isotropic, you're doing it wrong! Lol


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  28. #28
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    isotropic, hopefully you'll find this helpful, but you're going to have to put on a thicker skin than you've been showing. pvd isn't the kind of attacker that you want to attack in return. He's putting you on the defensive, it shows, even if he lashes at you, don't lash out.

    There are two phrases in one of your responses that show a little short sight. They are "because why would you want that" and "which I opted to do" shortly after.

    The answer to the first question, which you precluded anyone from answering by providing your own answer, is actually two answers:

    1) Because a preference is a preference.
    2) Because direct dimensioning packs more information into a given display size.

    In feedback to "which I opted to do", what you opted to do sounds more like a Hobson's Choice. If you have to make a choice from a list-of-choices that has a length of one choice, does it continue to be a choice?

    You made the best of a lacking situation (dimensioning features that Rhino lacks despite its powerful content creation features). Nothing inherently wrong with it on its own. Just don't get defensive about it when someone (rudely, in a roundabout way) says "I can't read this", instead ask "How do you want to read it instead?" and post an updated version.

    (Or don't, it doesn't matter until you build it.)

    For my money, I use FreeCAD, and it has some powerful 3D-to-2D tools. Is it better than Rhino? Is Rhino better than it? Are we supposed to care?

    *cough*

    One question, regarding your carbon tubing. That down tube doesn't look cylindrical like a prefab carbon tube. The other tubes all look straight-gauge. What's going on with the down tube?

    Another question, what do you mean by no budget with the 3D printing machine you have on hand? I didn't follow. You've... already paid for material that's in a laser sintering machine, or something, and you're trying to get your worth out of it?

    I too am using my extensive computing background for the sake of building frames, but there's always the very high chance of some rude surprise that happens after the computing is done.
    Disclaimer: I run Regular Cycles (as of 2016). As a profiteer of the bicycle industry, I am not to be taken very seriously.

  29. #29
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    I *think* Pete's point is that you are starting from a lack of basic knowledge about frame geometry, and because you're good at using Rhino (I don't even know what that is, for reference) you're spending a lot of time messing with optimizing/designing stuff that doesn't matter unless you have reasonable fit/geometry/design to begin with.

    I could be wrong about that, but that's the classic engineer-making-a-bike-for-the-first-time scenario. I get beautifully drawn up "designs" from folks all the time that are gorgeous and would ride/fit/work horribly.

    -Walt

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    but you're going to have to put on a thicker skin than you've been showing
    nail on the head there i think.

    The other tubes all look straight-gauge. What's going on with the down tube?
    the downtube is cylindrical, i think it could be either the lighting which makes it look strange, or the BB lug which doesnt have a constant radius (downtube diameter is 60mm at the moment, BB housing is 45ish, i forget), heres a pic:

    Super Slack 29er Hardtail Build - possibly 3D printed titanium lugs and carbon tubing-idzs5cx.jpg

    i havent got round to filleting the down tube BB interface yet, but i was going to go big to make a natural shape.

    on the topic of lugs. the robot bike co, who also have a ti printed lugged carbon frame have both internal and external lugs, the lugs are also the same length:

    Super Slack 29er Hardtail Build - possibly 3D printed titanium lugs and carbon tubing-robot-bike-co-bb.jpg

    question is, is that the best way to go about it? ignoring the possibility of failing glue, are staggered lugs better? is it better to have one long, and one short lugs in order to reduce weight, but will it affect the stress transfer between the lugs and tubes too much?

    You've... already paid for material that's in a laser sintering machine, or something, and you're trying to get your worth out of it?
    i get a specific amount of money to spend on "stuff" at work. since part of my job is making "stuff" cheaper, i always have money left over that i can spend. hopefully, ive done exactly what youve said with the left over money. it still has to go through finance, but im hopeful, plus i like designing stuff and this is quite fun. another issue is i only have a rough idea of how much printing in Ti costs, but i guess 1.5kg is around a reasonable amount.


    you're spending a lot of time messing with optimizing/designing stuff that doesn't matter unless you have reasonable fit/geometry/design to begin with
    i think this is where alot of confusion comes from. because im scripting i can build a model, then change the geometry afterwards. the script has a list of parameters at the beginning which Rhino reads. every time i run the script rhino rebuilds the entire model, which means i can change the parameter and then immediately have a new model with different geometry.

    for example, heres the same frame, but with 40mm shaved off the wheelbase. you can see the seat tube has been pushed back to accommodate the change in geometry (id have to shorten the top tube until the seat tube angle/effective top tube length are acceptable, neither are parameters but dependents)

    Super Slack 29er Hardtail Build - possibly 3D printed titanium lugs and carbon tubing-75tnevg.jpg

    also, im terrible at explaining stuff, so if this doesnt make sense its my fault

  31. #31
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    Yeah, this is where PVD is disagreeing with you. You've got seat tube angle as a dependent variable?

    The usual way to do this (assuming the bike will actually be pedaled, rather than just used for DJ or something) is to determine saddle position relative to BB first. That then is held constant. Next you'll want to decide on BB height, chainstay length, and trail/front center numbers. Then everything else is dependent.

    -Walt

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    Its been a long time since I've hung out in these parts, but it seems that much of the same stuff is still going on.

    isotropic - These last few posts by Walt & Drew are spot on. PVD has been around quite a while and has a ton of info to glean from. But you have to know how to get it (and receive it). Disregard the delivery. He's essentially saying that over the years many people have popped up in this forum with GRAND ideas and slick drawings....few ever get made (or even started). Truth is, Walt was pretty much saying the same thing in post #3. He just uses an economy of words along with some honey.

    My advice to brand new (tig & steel) builders/hobbyists is to go get your first frame done. Then immediately set it aside and start on #2. Number 2 will be 300% better than #1...and it will still be fairly crappy. (in the immortal words of PVD): Its overcoming the negative inertia of the multitude of steps in the process that is the real goal. This comment is so wise that I've used it as a signpost for many other facets of overcoming obstacles in life. It transcends far outside of just frame building.

    Since you are 3D printing the frame (which I've never seen done before outside of random engineering novelty blog posts), you may be charting new territory. The goal should be "learning through the process". NOT creating your dream bike the first time. This means that you can get quite a bit of geo feedback, but it means little unless you yourself have spent the saddle time on bikes learning what you like and what works for you (& why).

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  33. #33
    pvd
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    isotropic - I'm giving up on this thread. I don't think you are very serious about any of this. Essentially, you're ni##er rich for printing and want to drop on something neat but have no understanding of any of it and don't want to learn. Have fun.

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    Quote Originally Posted by CBaron View Post
    My advice to brand new (tig & steel) builders/hobbyists is to go get your first frame done. Then immediately set it aside and start on #2. Number 2 will be 300% better than #1...and it will still be fairly crappy. (in the immortal words of PVD):
    Don't set it assume. Ride the living daylights out of it while building #2. But yeah it's not going to be the dream bike you have in your head.

  35. #35
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    If you are anything like me, there will never be a bike that you finish that you're 100% happy with.

    But you have to get past that hurdle and make things, because bike 2 or 3 or 100 will be so much more awesome because of what you learned from screwing up the previous ones.

    That's life in a nutshell, I think.

    -Walt

  36. #36
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    Quote Originally Posted by isotropic View Post
    the downtube is cylindrical, i think it could be either the lighting which makes it look strange
    Gotcha. I had wondered if it was because of the in-viewport lighting that renders in milliseconds but sometimes shows weird surface feedback. Thanks for explaining where the printing resources are coming from also.

    Regarding the double lip style lugs that are possible with printing, how will it affect things... yeah I'm not sure! That is indeed pretty uncharted. I can see the benefit in terms of double surface area for adhesive. I see those Robot lugs have an escape vent giving excess air near the adhesive a place to leave.

    EDIT one thing I'm concerned for in your project, that the Robot folks must've figured out, is that secondary bonding adhesives need a very even bond gap to reach their full strength. I have doubts that you're going to be able to pull a printed part and straight use it as is, I think you'll want to ream it smooth at the joins. How to do that inside a tiny gap, that's ???? to me. In other words, Robot is either using an unusual adhesive, or they're ok with a suboptimal bond line, OR their double surface area trick really does work that well and I didn't know it.
    Disclaimer: I run Regular Cycles (as of 2016). As a profiteer of the bicycle industry, I am not to be taken very seriously.

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    Yeah, this is where PVD is disagreeing with you. You've got seat tube angle as a dependent variable?
    only in a mathematical sense. i know the area i want it in, but if i specify every parameter, the model will be over constrained and explode.

    hen immediately set it aside and start on #2. Number 2 will be 300% better than #1
    i understand what you and Walt are saying, problem is, i wont be able to afford to make no.2 in the foreseeable future. this is go for gold. geometry iteration 2 is closer to the piste though. if i follow others, it cant be that bad :P. heres the geo with other frames im interested in:

    Super Slack 29er Hardtail Build - possibly 3D printed titanium lugs and carbon tubing-0b7qr8a.png
    Super Slack 29er Hardtail Build - possibly 3D printed titanium lugs and carbon tubing-urgq4en.jpg

    i think the seat post tube should be steeper (i know, should be decided first), but this is early days. im still mulling it over. i might actually drop down to 650 wheels too. im using a 160 fork because its safer, if i designed around a 150, then decided to go up the front end would be EVEN SLACKER. mind you, i may still drop down, everything on the cards.

    you're ni##er rich for printing
    wow now! i prefer f##*ing lucky c##t! and im more than aware of it.

    I see those Robot lugs have an escape vent giving excess air near the adhesive a place to leave
    yeah, im not sure how many i need to put in or where. theyre essentially a weak spot which are asking for failure.

    one thing I'm concerned for in your project, that the Robot folks must've figured out, is that secondary bonding adhesives need a very even bond gap to reach their full strength. I have doubts that you're going to be able to pull a printed part and straight use it as is, I think you'll want to ream it smooth at the joins. How to do that inside a tiny gap, that's ???? to me. In other words, Robot is either using an unusual adhesive, or they're ok with a suboptimal bond line, OR their double surface area trick really does work that well and I didn't know it
    ok, a lot here.

    first off, we need to suss tolerances. this is extremely difficult to work out, and is actually the make or break. the precision of the printer (which defines maximum tolerance) is dependent on the dimension (x,y,z). in the horizontal plane, its amazing, within a few microns. within the vertical plane you have issues. as you melt the material gravity will pull it down creating an icicle type arrangement. furthermore, the laser direction also plays a part. the direction the laser blasts the powder pulls the icicles out of vertical, and parallel with the laser. just to add another layer of issues, theres about 10 parameters on the printer that affect the extent to which you get icicles, one of which is material. we are relative novices with titanium, normally working with stainless (its 'cheap'). technically you can predict icicle formation, but its hard and expensive, well beyond this project im afraid.

    on the topic of reaming, i dont think robot crew do it. its literally just a printed part bonded to a tube. three reasons for thinking this:

    1) sintered material is really good at bonding to stuff
    2) the cross section of the chain stay tubes arent circular but oval, im sceptical as of how accurately they can measure the profile to get a good fit (really hard, FARO arms cant do it!).
    3) how accurately can you make a carbon tube? not accurately enough to warrant reaming unless the tube is also post processed to fit.

    its really 3) that im interested in. is it possible to shave material off of the carbon tubes to make them fit? who knows. we'll find out though , and hopefully it will solve my icicle issue :D

    this is when it gets weird, i know a guy who claims hes had a mess around on a robot fame in a car park. but the frame was yet to be properly glued. assuming he got the right end of the stick (he isnt a cyclist), this opens a worrying question: if a frame like this can be held togeather with friction, can this frame even be slotted together? you certainly cant do one tube at a time. the entire thing has to be done in one go D:

    i know another chap who is an expert in carbon fibre adhesion (to other stuff), so im going to pick his brains about tolerances and the likes.

    when it comes to the the double lugging, theres only one way to determine the best option - FEA (stress analysis). fortunately, i f##ing love FEA.

    Also, i thought when i posted this i would have people pushing me to other geometries. "a little more here, but slacken this". and i thought people would gun me down for having quad chain stays. but its quite the opposite!
    Attached Thumbnails Attached Thumbnails Super Slack 29er Hardtail Build - possibly 3D printed titanium lugs and carbon tubing-1082192-super-slack-29er-hardtail-build-possibly-3d-printed-titanium-lugs-carbon-tubing-zkbyr9q.jpg  

    Last edited by isotropic; 08-11-2016 at 04:58 PM.

  38. #38
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    Quote Originally Posted by isotropic View Post
    i know another chap who is an expert in carbon fibre adhesion (to other stuff), so im going to pick his brains about tolerances and the likes.
    Acid etching is where it's at. Fuzzy surface, very little particulate left over from the typical manual abrasion, lots of surface area.

    Just by eyeballing those Robot lugs, I was simply thinking that the surface deviation was too extreme, like it would create a randomized bond line. More I think about it, I guess I should withhold judgment here because the adhesives engineers are more or less showing off at how advanced their craft is now, and there's probably some glue out there that is exactly applicable to what you're doing, I just dunno what it is.
    Disclaimer: I run Regular Cycles (as of 2016). As a profiteer of the bicycle industry, I am not to be taken very seriously.

  39. #39
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    If you have one shot, don't build it now. Don't even think about building it. Ideally, build some bikes with conventional techniques, or if that's not possible, at least ride some of the bikes you are copying. Then come back to it.

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    For once I'm enjoying reading about 3D printing! I've briefly had a spin on the Empire / Renishaw bike a couple of years ago - I presume you've seen that one?

    What is your thinking behind the double chainstays? I've done it with steel, but that was to get a small cross section to bend and squeeze between chainring and tyre on a short 29er (not an issue with your printed bb lug). I think generally they end up slightly heavier than a single tapered stay, but do give a very solid dropout connection / disc mount.

    If you're going to have a parametric ST angle (presumably using saddle rails / seatpost layback to get saddle back where you want it), then can you script it to at least keep a fixed clearance between the tube and back tyre :-)

  41. #41
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    Quote Originally Posted by isotropic View Post
    only in a mathematical sense. i know the area i want it in, but if i specify every parameter, the model will be over constrained and explode.



    i understand what you and Walt are saying, problem is, i wont be able to afford to make no.2 in the foreseeable future. this is go for gold. geometry iteration 2 is closer to the piste though. if i follow others, it cant be that bad :P. heres the geo with other frames im interested in:

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    i think the seat post tube should be steeper (i know, should be decided first), but this is early days. im still mulling it over. i might actually drop down to 650 wheels too. im using a 160 fork because its safer, if i designed around a 150, then decided to go up the front end would be EVEN SLACKER. mind you, i may still drop down, everything on the cards.



    wow now! i prefer f##*ing lucky c##t! and im more than aware of it.



    yeah, im not sure how many i need to put in or where. theyre essentially a weak spot which are asking for failure.



    ok, a lot here.

    first off, we need to suss tolerances. this is extremely difficult to work out, and is actually the make or break. the precision of the printer (which defines maximum tolerance) is dependent on the dimension (x,y,z). in the horizontal plane, its amazing, within a few microns. within the vertical plane you have issues. as you melt the material gravity will pull it down creating an icicle type arrangement. furthermore, the laser direction also plays a part. the direction the laser blasts the powder pulls the icicles out of vertical, and parallel with the laser. just to add another layer of issues, theres about 10 parameters on the printer that affect the extent to which you get icicles, one of which is material. we are relative novices with titanium, normally working with stainless (its 'cheap'). technically you can predict icicle formation, but its hard and expensive, well beyond this project im afraid.

    on the topic of reaming, i dont think robot crew do it. its literally just a printed part bonded to a tube. three reasons for thinking this:

    1) sintered material is really good at bonding to stuff
    2) the cross section of the chain stay tubes arent circular but oval, im sceptical as of how accurately they can measure the profile to get a good fit (really hard, FARO arms cant do it!).
    3) how accurately can you make a carbon tube? not accurately enough to warrant reaming unless the tube is also post processed to fit.

    its really 3) that im interested in. is it possible to shave material off of the carbon tubes to make them fit? who knows. we'll find out though , and hopefully it will solve my icicle issue

    this is when it gets weird, i know a guy who claims hes had a mess around on a robot fame in a car park. but the frame was yet to be properly glued. assuming he got the right end of the stick (he isnt a cyclist), this opens a worrying question: if a frame like this can be held togeather with friction, can this frame even be slotted together? you certainly cant do one tube at a time. the entire thing has to be done in one go D:

    i know another chap who is an expert in carbon fibre adhesion (to other stuff), so im going to pick his brains about tolerances and the likes.

    when it comes to the the double lugging, theres only one way to determine the best option - FEA (stress analysis). fortunately, i f##ing love FEA.

    Also, i thought when i posted this i would have people pushing me to other geometries. "a little more here, but slacken this". and i thought people would gun me down for having quad chain stays. but its quite the opposite!
    its called a PI joint like the symbol for PI you can google Pi

    to answer your other questions

    1) sintered material is really good at bonding to stuff

    thats not exactly how bonding titanium works but it will work based on the fact your filling a void

    2) the cross section of the chain stay tubes arent circular but oval, im sceptical as of how accurately they can measure the profile to get a good fit (really hard, FARO arms cant do it!).

    this is pretty irrelevant you can control bondline without needing to go to the nth degree measuring

    3) how accurately can you make a carbon tube? not accurately enough to warrant reaming unless the tube is also post processed to fit.

    Microns we used to make machines with carbon tubes for ZEISS again when people never knew how to do this **** It would hold length to microns well less than 1 micron and you could pretty much replicate down to 3 maybe 4 on diameter and 10ths on cyclindricity, you dont need this for bikes go back to question 2 for a general tube your mandrel will control the basic factors for the types of tube you might make

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    Acid etching is where it's at
    i really want to go down this route but im not sure itll work. you need a constant flow of fluid over the surfaces if you want a constant removal of material, in which cases the channels of the lugs might be a problem. also the PSU is broken on our kit

    at least ride some of the bikes you are copying
    dont worry, im on it. in Sept our (currently empty) mtb club will be teaming as the students are back, and with them their bikes.

    Empire / Renishaw bike
    Renishaw is effectively the parent company of Robot bike co, i hadnt actually seen the empire bike (thanks for pointing me there), but i think it might all be the same chaps.

    What is your thinking behind the double chainstays?
    ive got a relatively restricted selection of tubes to choose from, i just wanted something stiffer in one direction that can still easily get around the chainrings.

    If you're going to have a parametric ST angle (presumably using saddle rails / seatpost layback to get saddle back where you want it), then can you script it to at least keep a fixed clearance between the tube and back tyre :-)
    for sure, and thats a really good idea. it would be quite easy to implement in my script too.

    Microns we used to make machines with carbon tubes for ZEISS again when people never knew how to do this **** It would hold length to microns well less than 1 micron and you could pretty much replicate down to 3 maybe 4 on diameter and 10ths on cyclindricity,
    sweet! i found a few tube manufacturers stating a tolerance of 100micron on the diameter so i was pretty worried, if its all significantly less then thats ace.


    something i havent thought about until recently is tension cables. i might set one from the head tube to the seat tube just to ensure no catastrophic failure occurs. plus they look cool.

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    Quote Originally Posted by isotropic View Post
    i really want to go down this route but im not sure itll work. you need a constant flow of fluid over the surfaces if you want a constant removal of material, in which cases the channels of the lugs might be a problem. also the PSU is broken on our kit
    So are you trying to go beyond Very Good and go straight into Totally Laboratory Quality stuff?

    Because you're referring to some adhesives equipment that might be kinda rare and I don't want you outing your company on the net. Additionally, is that level of sophistication required for achieving your first frame build?

    Like maybe you could clean it, dry abrade it, etch it, allow the acid to evaporate, then apply adhesive and go on your way. Yes, if you're not in a clean room you'll have some contaminants that won't be able to see before you get your adhesive on, just make up for it with overlap surface area.
    Disclaimer: I run Regular Cycles (as of 2016). As a profiteer of the bicycle industry, I am not to be taken very seriously.

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    Totally Laboratory Quality stuff?
    entirely possible. also im pretty sure the RBC dont etch, or electropolish their frames. they are literally using raw surface finishes. with exception to the head tube surrounding the headset which is machined post printing. possibly the BB shell too
    Last edited by isotropic; 08-18-2016 at 02:29 AM.

  45. #45
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    Quote Originally Posted by pvd View Post
    isotropic - I'm giving up on this thread. I don't think you are very serious about any of this. Essentially, you're ni##er rich for printing and want to drop on something neat but have no understanding of any of it and don't want to learn. Have fun.
    As someone who seems to be familiar with the use of the English language, I'm sure you can come up with some colorful insults that don't drop to this level. C'mon man, I realize you may be insulated out there in almost-Marin, but grow up.

    OP- stop talking, start building. It is only money and it's not even yours!

  46. #46
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    OP- stop talking, start building. It is only money and it's not even yours!
    Haha, its going to be a while before i can print anything because our machine is filled with stainless steel. i could print it in stainless (i could probably print 3 of them if i did), but the weight is an issue, and print quality plummets with stainless relative to Ti. ive got no idea when the printer will cycle to Ti, but im no where finished designing yet, so its gunna be a long hall this build.

    also, nicolai have really pushed the boat out with how slack a hardtail can go, theyve dropped down to 63 degrees (and their DH frame is 61.5!)

    Super Slack 29er Hardtail Build - possibly 3D printed titanium lugs and carbon tubing-1x9a3199_1_1.jpg

  47. #47
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    Did a bike get built?

  48. #48
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    It seems that I was right.

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    Quote Originally Posted by pvd View Post
    It seems that I was right.
    Or you ran yet another person off with your opinions.

  50. #50
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    I'm pretty sure if someone is prevented in doing something by the opinions of another on an online message board then they really weren't serious in the first place. Moreover, my 'opinions' are correct.

  51. #51
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    Could Pete be more polite, and still make his point? Yes.
    Do CAD wonder engineers who don't know much about bikes end up just drawing their wonderbikes and never building them? Yes.

    That said, I'd love to be proven wrong on both counts...

    -Walt

  52. #52
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    Quote Originally Posted by pvd View Post
    I'm pretty sure if someone is prevented in doing something by the opinions of another on an online message board then they really weren't serious in the first place. Moreover, my 'opinions' are correct.
    Or he built the bike and never posted again because some self proclaimed expert ran him off. You've got some great knowledge but sharing it in a constructive way is something you can't seem to accomplish.

  53. #53
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    Quote Originally Posted by customfab View Post
    Or he built the bike and never posted again because some self proclaimed expert ran him off. You've got some great knowledge but sharing it in a constructive way is something you can't seem to accomplish.
    He didn't.
    I am an expert.
    I'm far more constructive with and share far more than anyone I know.

  54. #54
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    Regardless of whether he built a frame or not, i'm sorry he got shooed off. I would have enjoyed watching him work through the design process with materials and processes i totally don't understand.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

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