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Building your own bike frames - anyone here ever done it?

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  • softtail
    replied
    Machine, what you describe about the top of the chain being taught, and the bottom loose is not from cs flex. But of course frames flex all over the place.. nice to have them return to center so to speak..if its already of 2mm to the left...

    Facing of the headset and bb may be necessitated regardless depending how you conjure to hold them in jig. Holding an eccentric through the middle can lead to some serious frustration after distortion. Two parallel faces that can be refreshed through the build is a goo route regardless of it being needed for the bearings.

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  • 754
    replied
    How does the EBB clamp ?
    In case any one thinks it's new I had a motorcycle frame built 110 years ago that had that
    Most frames are built to an acceptable tolerance with affordability being a big consideration.
    Many motorcycle frames were not perfectly straight, and had room for improvement.
    It's pretty cool to build your own frame, go for it..

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  • softtail
    replied
    Originally posted by wombat2go View Post
    Assuming the bicycle frame is 2-Dimensional, Y: vertical
    What is the allowable tolerance of the centrelines of the 4 bearings and seat tube, in zero loading from Y=0?
    Is there an ISO standard for this?
    Thanks
    Edit_ assuming symmetrical spokes etc
    No ISO. There are so many variables.. and bikes aren't big money, considered kids things in the US by and large. Some things that one would think would make a frame unrideable are barely discernible.. others show nasty characteristics despite being very straight/true.

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  • wombat2go
    replied
    Assuming the bicycle frame is 2-Dimensional, Y: vertical
    What is the allowable tolerance of the centrelines of the 4 bearings and seat tube, in zero loading from Y=0?
    Is there an ISO standard for this?
    Thanks
    Edit_ assuming symmetrical spokes etc

    Leave a comment:


  • Machine
    replied
    Thanks again everyone for the helpful tips. I haven’t really given much thought yet to how I will fixture the frame during the welding process, other than having a general sense of fabbing up a heavy duty square tubular steel frame made of scrap metal welded together with my Mig. Then machining precisely located mounting surfaces for the headtube, BB and rear dropouts onto the jig using my mill. I'm going to try to design the jig not only as a welding fixture but also as a frame holder that can be bolted to my mill’s table for the machining operations. Not sure if that’s really practical, but that’s what I’m thinking about now.

    From what I could see in the frame building video someone mentioned earlier, the key to avoiding warpage during welding is to tack it first and then weld in certain sequences. If you do this and don’t generally overheat the frame, apparently it can come out virtually perfect right off the bat. But if there is some fairly minor warpage, I’m not above breaking out a bender bar or two to put it straight before final machine ops. The other factor I was considering is to make the headtube and the BB shell thicker than they needed to be. That way I could line bore the headtube and BB shell, and I would have enough excess to accommodate slight overall misalignment and/or heat warpage.

    The other thing is that an eccentric BB doesn’t need to be faced on the outside, unlike a regular BB shell. Its bore only needs to be round, sized properly for the rotating eccentric insert and aligned so it’s perfectly parallel to the rear axle.



    Also, the modern/new tapered 1.5/1.125” headtube with integrated headsets also don’t need the outside surfaces to be faced, unlike the old 1-1/8 pressed in bearing standard.



    You just need a cleanly machined recess to accommodate the bearings. A job custom tailored for a Bridgeport, I think. I also have a 90 deg attachment for my Bridgy if I need to go that route, too.

    As far as the level of quality and precision I’m going for. I definitely want to shoot for a very straight frame with absolutely imperceptible flaws in handling and rideability. On the other hand, I tend to agree with 754, I don’t think it really has to be made to 0.0001” Swiss watch precision. I’ve learned over the years how much lightweight bike frames flex and twist all the time as you’re riding them. Hell I can jump on my Trek bike right now and simply lay my foot on the pedal, tension the upper part of chain up a bit and watch the lower chain go slack due to the pretty extreme chainstay flex. But the bike’s still very rideable and is an awesome handling bike. But I do plan on not settling for anything less than pretty damned straight – at least as straight and aligned as a store bought bike normally provides. I won’t settle on that no matter how long it takes me to get it right, up to and including destroying the frame and starting over if it isn't square the first time around. And I especially want the EBB to function perfectly. I don’t really like EBBs because they tend to be heavy and have caused me problems before (mostly with slipping and sliding laterally). But for this bike, I’m kind of forced into using one. So I do plan on custom building one of those to high precision to ensure it works flawlessly and in accordance with my exact specifications.

    As far as weight, if the bike comes in at under 30lbs I’ll be reasonably pleased. If it comes in under 27lbs, I’ll be very happy. If it comes in under 25lbs, I’ll be ecstatic. Remember, this is an XL size, 29+ fat tire bike (tires are 3” wide) with some overbuilt features and it’ll be steel. On the other hand, it will be a single speed (SS), which should save some weight. It will also have high end lightweight components ($900 wheelset, $400 crank, $400 brakes, $150 handlebars, $250 pedals etc). These types of bikes, even expensive ones made out of aluminum or Ti, commonly weigh in at 25lbs or more. Although yes, there are some weight weenies that can manage to get it down to a skeletal 19-20lbs. But I have learned over the years that those bikes are not durable and also not comfortable because you must forego a front suspension fork along with silly things like shaving the rubber out of your grips to achieve true weight weenie nirvana. No thanks to that, although I have been riding fully rigid for the past year and half and am actually pretty used to it now. The aluminum bike I ride now probably weighs around 26lbs, although I haven’t weighed it yet.

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  • 754
    replied
    I should mention at this time, a weight weenie bike built here in town.
    I think it came in at 9 lbs or so with 1 cluster on it..not sure of final weight.
    a lot if it was built by the guy himself with fairly limited amount of tools at his disposal.
    I made a few bits for it, can't remember what, but at times he would show me some of the parts, very light.
    Eventually he got a 3 in 1 machine and maybe a mill, and when he would ask me to make something for him, I started to tell him how to do it with what he had.. that was sort of fun..
    I think finished, it was maybe the 3rd lightest in the world at that time, but honestly it had less than a third of the dollars into it than the others..
    So be careful throwing around the cant word, and difficult, and tricky to do that... good thing not everyone will listen to that.

    Leave a comment:


  • 754
    replied
    I suspect bicycle frame specs may be more forgiving than you are imagining.
    Of course it depends on the end use as well. However someone on here wanting to build their first frame, I doubt they expect to meet world class standards ... they just want to ride a bike which they made and learned from.
    Any process can be over thought.
    I don't think the bicycle fab considerations are as hard to do as some of the Bonneville frames and forks that have been built here in this town..

    Leave a comment:


  • softtail
    replied
    754, like I said it cane be done. Depends what tolerances one wants, and if they are able to tell. Using the outside of a distorted tube won't give you true center line. Enough to matter? Possibly.

    Bike frames, by nature of light weight and self propulsion, can be airy fairy contraptions.. its harder to get away with things than on a motorcycle frame.

    But having said that, if materials are pretty straight to start, miters are dead nuts, welding is done very well, jigging perfect, etc, you can get a frame out of the jig with no post prep that will ride just fine. Would probably ride better, and the bearings would last longer with facing...

    Depending how the frame is going to built, facing the bottom bracket may need to be done multiple times throughout the build.

    A horizontal mill would excell these ops...

    I would probably square the rear drops first, and use a dummy axle with scribbed center line, and go from there. Putting a heavy scribe around the faced bottom bracket *before* building would be a good idea. Getting the seat tube welded exactly on center in regards to bottom bracket faces would also help. Then you could know rear axle center, figure/adjust to bb center (and thus seat tube center), and move on to head tube center.. possibly via head cones all the while taking into account front triangle droop aka gravity. If you run some strings from drop out faces around heat tube and measure standoff off of strings at seat tube, you can replicate that on mill table with frame laying down, and some kind of supporting jack on underside to get the readings from strings while it was vertical.. assuming readings were equal thus eliminating droop. Having the frame vertical is nice in this regard....

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  • 754
    replied
    Originally posted by wombat2go View Post
    I use Harris Safety Silv 56 in belief it is Cadmium free (AWS 5.8- BAg-7)
    There are sample Cert sheets showing nil Cd . To get actual certs,
    it was necessary to provide my details unsecured to their web site so I did not proceed.

    I looked at 2 other providers of 56% Ag to WS 5.8- BAg-7 and one mentioned "Cd Free" and another showed nil Cd on a chemistry sheet.
    I just speak from my own experience but if I had to square a head tube on a BP..
    I would put the head tube in a few blocks or on a shim. Clocking the front face and support the back of the frame with a stand.
    Check level of headtube vs seat tube, straighten if needed. Once headtube is clocked and leveled to table, cut across end of head tube.. light cuts.. square it up ..
    Not seeing any great difficulty or huge amount of time there.
    Butvtgey I have had several motorcycle frames on my mill table, and they are harder to work with..

    Leave a comment:


  • mattthemuppet
    replied
    I don't know about the headtube finishing, but the BB threads/ face in your eccentric can be finished with the standard Park BB threading/ facing tool. It does both at the same time using the other side of the BB to center the tool via a threaded rod. Only takes 15min or so and I'm sure your local bike shop will let you use one for a 6 pack if your friend doesn't have one. Also worth thinking about are what type of BB you want to run. I'm old school(ish) and out of the loop, but the last time I looked there were a whole bunch of different BB types - thread in external, thread in internal, press in etc. Looking forward to see what you come up with for an eccentric BB, those things are cool.

    Leave a comment:


  • softtail
    replied
    Use dedicated frame tools. Pay a shop or frame builder if need be. Many reasons.. which in theory can all be overcome, but in practice will be difficult and will require making jigging above and beyond the effort/cost of using frame tools. Finding and keeping the frame's true center line (and keeping it) in both bb and head tube is one of the challenges. There will be appreciable warpage both in terms of the faces and the diameter (seat tube included..use a shim and also sleeve the outside). That's one set of difficulties.

    The other is trying to jig/hold a frame on a mill table with the rigidity/tolerances needed for the given tasks. What are the references? Difficult. Would take a lot of special blocking/support with special consideration given to how and where you are supporting frame to get acceptable results. A frame is a big long flexible noodle in this context...

    An adjustable reamer and flex hone will due for seat tube unless you have really cooked the hell out of it.

    Leave a comment:


  • wombat2go
    replied
    I use Harris Safety Silv 56 in belief it is Cadmium free (AWS 5.8- BAg-7)
    There are sample Cert sheets showing nil Cd . To get actual certs,
    it was necessary to provide my details unsecured to their web site so I did not proceed.

    I looked at 2 other providers of 56% Ag to WS 5.8- BAg-7 and one mentioned "Cd Free" and another showed nil Cd on a chemistry sheet.

    Leave a comment:


  • Machine
    replied
    Originally posted by john hobdeclipe View Post
    I was thinking about various aspects of this project while riding my bike this morning. Here are a couple of things to consider: After you have successfully built your frame, by whatever process you choose, you will still have some specialized machining to do.You'll need to ream and face the head tube for the headset of your choice. You'll need to cut the fork crown / steerer to match your headset. You may need to thread the top of the steerer if you choose a threaded headset. You'll need to ream the seat tube. You'll need to face the bottom bracket shell, then tap or otherwise machine the inside to fit your choice of bottom bracket bearing configuration. All of these operations require very specialized tools. And another thought...if you use silver solder to build a lugged frame, be aware that many silver solders include cadmium, which is a real nasty to breath. This I know from experience, it's real, real nasty. At any rate, keep us posted on your project
    Thanks John. Here’s what I’m thinking about those topics now:

    I know someone who said he had a lot of these specialized bike machine tools and offered to let me borrow them. So I might be able to borrow them from that person (maybe). Otherwise, I’m thinking I might be able to use by Bridgeport to do most of those functions. Here’s what I’m thinking:

    Assuming the headtube and bottom bracket are somewhat distorted after welding (a pretty safe bet) I should be able to set the fully welded frame up on the mill table and bore both headtube and BB. Also, face each end so that it’s square. Might be a bit more trouble than using the dedicated tools designed for that specific job, but shouldn’t be too bad. And yes, I probably would need to bore the BB because I’m probably going to be using an Eccentric BB (EBB) for chain tensioning purposes (this bike will be a single speed (SS)). I plan on building a custom EBB to my own specs, but haven’t fully figured that part out yet. I will not need to thread the BB shell, but I probably will need to thread the inner eccentric part, but that part will be aluminum.

    Other notes: I won’t be using a threaded headset or steerer. I’ll be using the latest greatest 1.5/1.125” tapered headtube which is starting to be the new standard for mountain bikes.

    Reaming the seat tube – I hadn’t thought about that one yet, but you’re right, that may be a consideration. Although I’ve thought about using a slightly oversized seat tube and then inserting a thin aluminum spacer for a smaller aluminum seat post. The reason I’m considering that approach is because of the possibility (or likelihood) of dissimilar metals/galvanic corrosion between the steel seat post tube and an aluminum seat post. I’ve had that happen before and also seen it happen on other steel frame bikes.

    Years ago, I had a Trek 950, a really nice chromoly steel mountain bike from the mid-90’s, and I used an aluminum seat post on it. I rode that bike for years including in the mud and muck often. Since the seat was adjusted perfectly for me, I never needed to adjust it. Over time, the seat post welded itself into place, and I mean it was WELDED via galvanic corrosion. The only way I could remove it was to use my oxy acetylene torch to melt it out of the seat tube, which utterly destroyed the bike’s pretty copper colored paint job. I also sold another nice steel mountain frame to a friend and the exact same thing happened to him in just a year or two. I know it can be prevented by moving the seat post up and down occasionally and maybe using some form of protectant, but that’s a hassle and something I’m likely to forget over time. So I’m thinking if I just use an insert, I don’t care if it welds itself into the seat tube. As long as I can adjust and remove the seatpost when needed, that’s all that matters (other than a pretty minor weight penalty for the shim).

    I’ll remember what you said about the cadmium in the silver solder. I’ll plan on just using braze or possibly go for Tig. But I’m liking the brazed approach so that’s probably what I’m going to do. Thanks again for the tips and happy riding.

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  • 754
    replied
    I would face headtube before welding, then ream after welding
    Can you not weld threaded and faced bottom bracket, then Chase threads after welding?
    All of which can be taken to a shop to get done.

    Leave a comment:


  • john hobdeclipe
    replied
    I was thinking about various aspects of this project while riding my bike this morning. Here are a couple of things to consider:

    After you have successfully built your frame, by whatever process you choose, you will still have some specialized machining to do.

    You'll need to ream and face the head tube for the headset of your choice. You'll need to cut the fork crown / steerer to match your headset. You may need to thread the top of the steerer if you choose a threaded headset.

    You'll need to ream the seat tube.

    You'll need to face the bottom bracket shell, then tap or otherwise machine the inside to fit your choice of bottom bracket bearing configuration.

    All of these operations require very specialized tools.

    And another thought...if you use silver solder to build a lugged frame, be aware that many silver solders include cadmium, which is a real nasty to breath. This I know from experience, it's real, real nasty.

    At any rate, keep us posted on your project

    Leave a comment:

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