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Guypie's Bike Build - It's done!


Guypie
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For many years I have wanted to have a go at building a bike frame and have slowly been working towards getting all the gear to put one together. The other day I was watching a video on the couch and the video quoted something that Frieburger off roadkill once said - "don't get it right, just get it running". I had a think and while I don't have the ideal equipment job, people have definitely got the job done to a good standard with worse equipment than what I currently have.

So instead of getting my arse off the couch I opened up tinkercad and started modeling a bare bones frame jig. Basically something to hold tubes perpendicular to a flat plane and a mount to hold the bottom bracket vertical.

I ended up coming up with these bits here:

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After a bit of fiddling around the centre height ended up at 58mm for no particular reason. Someone kindly donated an old chromoly marin eldrige which made me cry inside a little to cut up, however it had signs of rust in the tubes and the previous owner was not confident to reuse it. I cut the bottom bracket and headtube off it and will hopefully be able to salvage the tubes of the rear triangle too.

Here's the bottom bracket fixture printed and attached to a backing board. the hole is friction fit for a 9.5mm drill bit, I just threaded in some m10 threaded rod after a quick trip to the hardware store.

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The fixtures have alignment arrows built into them so you can mark a line on the backing board and place them on the line fairly accurately.

 

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The larger item there is a bottom bracket fixture thing that I drew as well, I'm undecided as to wether it will be worth using or not at the moment.

More coming soon...

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MDF is flat and lighter to move than an old lathe bed......and you can screw fittings to it.

I do my frames (motorcycle) in a box jig in which I can adjust the steering head angle and distance to the swingarm pivot. You don't need this.

How are you welding it ?

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So the bike I am building is going to be a full rigid, 27.5" plus tyre mountain bike with pretty aggressive geometry. I am going to make the chainstays extra long as both of my mountain bikes have short chainstays (435mm and 425mm) and I would like to see how the handling is with a longer chainstay length.

I drew it initially on the free version of bikecad, which is super annoying as they don't include all the measurements, no doubt to try to get you to buy the full version. So I printed off a picture of the frame with as many measurements as it would allow, figured out the scale of the print and extrapolated the measurements that were not on the printout using some vernier calipers. Next time I think I would just jump straight to doing a 1:1 drawing on a backing plate/paper.

Anyway here is roughly what I am building, the front triangle is going to be as per the drawing but I may end up gong 450 on chainstay length if the materials I have allow for it:

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I have ordered a rigid 1 1/8" steerer fork off aliexpress that I will probably need to cut and shut to give it tyre clearance and to fit thru axle wheels, hopefully it isn't complete garbage but if it is I will probably get a surly fork to suit easily enough. The stack height is a bit weird so my plan is to get a set of dirtbike handlebars with 75mm rise to get the height up to where most of my bikes are, and bore out an old bmx stem I have lying around here to suit the 28mm bar diameter.

Initailly I used a piece of 18mm plywood as my backing board, but after a bit of measuring I found it was very un-flat. So I decided to go with MDF as it is quite stiff, dimensionally stable and best of all... cheap. So I drew the board out a second time and chucked on the bits and pieces that I have so far.

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I ordered 6 feet of 4130 1.5"x0.035" tubing for the seat post and down tube (with extra to allow for stuff ups) and 2 feet of 1.25"x0.035" for the top tube (no room for stuff ups, that will go in the triangle last) from AFWE in auckland and made a jig which is blatantly stolen off @Valiant to mount the tube in the lathe toolpost for coping:

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It did a pretty good job, need moar hose clamps for better holding power. Maybe a hole saw that has all its teeth would help too as it snagged at the top and gave it a bit of a ding, came out ok with a little tappy tappy with the hammer.

 

 

 

 

 

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Spun up the tube with some sandpaper on the lathe, it is mildly terrifying contemplating what would happen if it comes flying out and stabbed you in the hand or something. I guess not being complacent is good! popped it in the jig and found I need to make an adjustment to my end piece as the cone is slightly too small for the ID of this tube. Spent a bit of time filing the coping to try get a nice tight fit.

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And thats about where I am up to at the moment. I need to practice Tig welding on thinwall on tube before I can get much further so I have ordered the recommended tungstens and consumables for my torch. Might have to get a lesson or 2 from @Geophy hahaha

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5 minutes ago, GregT said:

MDF is flat and lighter to move than an old lathe bed......and you can screw fittings to it.

I do my frames (motorcycle) in a box jig in which I can adjust the steering head angle and distance to the swingarm pivot. You don't need this.

How are you welding it ?

I have a tig, though I have a few hurdles to get over with it before getting on to welding the frame. First of all I am not very good at it, so practice is needed. Second, I don't have a pedal, a pulse function or downslope on my welder. I think if I can get a pedal sorted it will do the trick, it can take one but it is a very old cigweld with a 7 pin connector and I have not been able to find a pinout for it.

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Shit yeah this is mean, bring around some scraps and ill give you a hand. You shouldnt need a pedal even though alot of people use them just use the right amperage and be more fussy on your torch angle. If your keen I have some tig brazing rods ive been wanting to use on a big project.

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Wow! 

This is really exciting. I like your plastic? stands, they would make life easier.

I'm really glad that you've made a tube jig. I use new hole saws welded to some 7/8 bar so they are held really strongly in the chuck.

 

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2 hours ago, Valiant said:

Wow! 

This is really exciting. I like your plastic? stands, they would make life easier.

I'm really glad that you've made a tube jig. I use new hole saws welded to some 7/8 bar so they are held really strongly in the chuck.

 

Oh yeah, I forgot to mention that. The jig parts are 3d printed. Means I can sit by the fire inside while I "make" a thing in the shed hahaha. I am thinking it will probably be a single use jig, we will have to see how they come out after the frame has been in and out a few times.

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3 hours ago, Geophy said:

Shit yeah this is mean, bring around some scraps and ill give you a hand. You shouldnt need a pedal even though alot of people use them just use the right amperage and be more fussy on your torch angle. If your keen I have some tig brazing rods ive been wanting to use on a big project.

received_301090431697096.jpeg

I did wonder about tig brazing. I did a bit of googling and found a bunch of people who said it cant be done blah blah blah, but I found the same thing when I googled about mig welding a bike frame. Then there was one thread where a dude actually did it and it was fine. He even posted up a update a few years later and said it was still all good, no cracks or failures. It was a trials frame too so not something that would not have been nana'd either

Edit: just had a look, er70s-2 is the recommended filler for 4130, its rated 483mpa tensile, the silicon bronze is 340mpa. Does that mean if the fillet is say 20% larger strength would be same same? Maybe we should make a few test pieces and smack em around with a hammer...

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I use manganese bronze rod and gas. My frame joints look like his large fillets where he used the bigger rod. Never had one break - and they've been crashed too. They're mild steel tube and the big, softer fillet is a good match and won't crack.

What is typical is the lack of mention of nickel bronze rods. They don't seem to be used in the US. Strength is a lot higher so a smaller fillet can be used.

Where you're using high strength tube - like your CrMo tube - I'd use nickel bronze as the filler rod. It's a very good match for the material.

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Progress update: No further work on the frame :(

But a lot has been happening working towards the frame build. I turned up an arbor for a 1" holesaw and welded the holesaw to the arbor as @Valiant suggested and got some 1" mild steel tube 1.2mm thick to practice welding on. It is galve which is somewhat annoying, so I ended up plugging the end and filling it with acetic acid to clean all the galve off the inside. I filed and sanded the galve off the outside, though I think there may still be tiny specs or pockets of galve hiding in the dips and divots of the surface as I am having a bit of difficulty with porosity occasionally in the weld.

I also upgraded my coping jig as the hose clamps just weren't cutting the mustard. A couple of g clamps welded to a second piece of angle iron now clamp the tube:

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I lined the jaws in skateboard grip tape for maximum traction as if the tube slips it snaps the teeth off the holesaw which is super annoying.

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It works great. I might chop off the t bars and turn some thumb screws with a nut on the back to make it quicker to open and close when its mounted on the lathe later, but for now its good to go.

This is my first practice piece:

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I thought burning through was going to be much more of an issue but it was not a problem. I found around 55a seemed to work best, the difficulty is getting comfortable and moving the torch in an arc so you don't end up balling your filler before you get to dip it in the puddle. I took that join over to the anvil and squashed it flat, it held together well:

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So I whacked it backwards and forwards until it failed. It took a lot, more than what I was expecting considering it wasn't a very pretty weld!

 

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Here is the failed weld:

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While it certainly isnt going to win any beauty contests I think as a bike frame component that weld wouldn't fail, it took a lot of beating on to get it to crack.

I coped and welded a few more joints and that's where I am up to now, I think there must be pockets of galve causing issues with the weld as I am getting little pockets of contamination even though everything looks nice and clean:

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I am probably going to do a few more practice copes and welds and then just go for it. I figure this is bike frame no.1, may as well just get it done and consider it to be a learning process and not a final product.

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Good enough. I've said elsewhere that if it bends before breaking you've discovered ductility....If it breaks before bending, blame the welder, the metal or someone else.

Getting something finished and operating will teach you more than walking away due to not being happy with some aspect of the job.

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I probably have some short lengths of 4130 in my garage if you want those to practice with, it would be way better than galv. I am in Nelson tho so it might be a mission.

That last bit of tig of yours is about the same level of skill I welded up my fat bike forks with, and those have had a good chunk of punishment with my fat arse adding stress. They are still mint.

This all reminds me I still have most of a CX bike frame mitered and sitting in my frame jig where it has been for 5 or 6 years. Should probably get onto that.

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PM'd about the lengths. Good to know that quality will do the job!

I figured with the remaining tube I have I would make a tiny bike. So made a 1:5 scale version of the frame hahaha

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Started welding it together and had all of the contamination problems. I have been cleaning the metal with alcohol, I think it might not be aggressive enough so I figured I would call it quits for the day and try again later with some acetone.

I have probably hit my learning absorption limit for the day as well. go to sleep and try again tomorrow.

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