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Guypie's Bike Builds - A paint job and more!


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30 minutes ago, anglia4 said:

Dylan will the 4130 need pre-heating for tig welding?


TBH I never bothered. I cant remember if that was the result of my research or laziness. I have a feeling that preheating allows more alloying elements to migrate away from the join than is desirable but I would need to look hard at the thing again to know, so dont take that as a given.

I did spend a lot of time looking for the correct filler wire, my results told me that MIG wire (generally ER70s) is perfect for this sort of thing with 4130.

Which tells me that a tidy Mig weld would be fine too. I don't know if anyone remembers the longbike, but that was MIG and stood up really well.


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I had heard about the brake cleaner thing, pretty scary really. I figured out most of my problems with getting nice welds had more to do with sheilding. I'm pretty sure my torch body in just old and worn out. It has a gas tap on it that didn't have an o ring so I put one in, the wrapped it with electrical tape. I have borrowed a gas lens off a friend and that seems to help too and has brought down my gas flow requirement which is nice. I have a new torch body and gas lens setup on the way from aliexpress.

After coping some of the tubes I had a couple of offcuts left so I had a little test on those with the gas lens setup:


Happy with that. By this time I had already tacked the seat tube to the BB, so I just went ahead and welded that up. you can see it in the background of the above picture kind of, its not quite as good as my test weld as its a bit tricky with the BB being 3mm and the tube 0.9mm trying to get the heat to go where you want it.

Heres a few shots of the tubes getting added to the jig:



On the picture below you can see a little block that I 3d printed to get a level surface to reference so I could accurately clock the tube 90 degrees for the bottom bracket cope, also fresh deliverys from @ThePog thanks!:


A few more pics to come in the next post...

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More pics of welds:


These are the uglier ones:



I think the one sied of the BB wasn't clean or still had paint residue in the steel cause it was a bit fizzy and I couldnt really do much about it.

I popped it on the scales to see how things are tracking:


1556g, not too bad. I think it will come out around 2.7kg mark, I have been making the "dropouts" (thru axle so they dont drop anything out) and they are going to be a bit heavy hahaha.

I turned a reducer out of stainless on the lathe, which took a long time because my lathe is very worn out. A heck of a lot better than no lathe though!


In the frame:


This actually added 10% to the weight of the frame so far haha. I don't really care about the final weight that much, but I think it is worth considering while I am making bits and pieces for the frame.

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Aaaaaand welded in place:


Will need to send a reamer down the tube as internally it has gone kind of hourglass shaped from welding it in place.

I threw the frame back in the jig to see how far/close it was to original dimension, its pretty darn good!


Using the height gauge it looks like in relation to the headtube the seat tube about 0.5mm off line. Which I don't think will be noticeable at all in the end product.

I gave the lathe a cleanup at this point as the swarf overflow was starting to get sucked into the leadscrews which is generally a bad time


This is my old lathe, its a selson probably from the 1920s. The headstock bearings are absolutely stuffed and it can only turn anything by virtue of being heavy. Too much cutting load and it starts to vibrate like crazy as the spindle "rolls in the slop" if that makes sense. I actually have another newer much better lathe on the other side fo the workshop, but it needs 3 phase that I don't currently have.

To make the dropouts my plan was to turn some centres for the axle and weld them into a bit of tube, then cope the chain stays and seat stays to weld to the dropouts. kind of like this:


but a bit more simplistic. So I got a chunk of stainless and started whittling it down...


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After a few hours of work (not even kidding, gotta go real gentle on the old girl!) I came out with these:



I used a piece of stainless tubing I had to make the shroud part and tacked it on


then remembered that stainless is poos and will go all sugary on the backside if it gets too hot as below. So I filed off the tacks for round 2


This time with 4130 tube:


Then I welded it up...


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And it came out like this. fairly yuck

after heaps of fileing/sanding/scotch bright it looked a bit like this:


Its kind of ok, but I'm not really happy with it. So with about a days worth of work in it I decided to scrap it and start again.

Today I spent most of the day turning these out of some mystery steel from my box of offcuts:



They look a bit like oldschool skateboard wheels. Much more happy with the outcome, I need to cut the shroud parts down to the correct size so I will probably go get a nice new file tomorrow and just do it by hand. I had a little test run on the lathe putting it off centre with the 4 jaw chuck. It would work but it was mildly terrifying, not to mention if the jaws slipped on the workpiece it could turn it to scrap metal real quick

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  • 2 weeks later...

I have managed to get a bit more done on this in the last couple of weeks. Here is a terrible picture of my BB to rear axle jig.



I won't be using this again, for the next build I will make a proper jig. But it got the job done.

I filed the bottom of the lip of the frame ends flush so that when you have the bike tipped upside down to pop the wheel in there's a ledge for them to rest on. The horrendous surface finish on the dummy hub in the jig is a bit weird. I have a bunch of lengths about 300mm long of some sort of medium tensile steel that was the offcuts of a CNC job from a friends workshop. I cannot figure out how to get a decent finish on it, it just always comes out with a very torn up looking surface. I have tried a few different tool geometries, different feeds and speeds, always comes out looking like balls.



BB is centred on cones. The other reason I will be going with a new jig next time around is that there's barely any space in here for the 68mm BB shell. I only used that size because that's what the old marin had. Next time I think I will buy a new shell in 73mm.

(or maybe 83mm...)



Also those 2 holes from the old chainstays were a pain, I had to patch them as the new stays didn't line up with the holes. not sure if I took a photo but it looks a bit of a mess in there. fortunately that little nook is always just jammed full of mud anyways so as long as I don't clean the bike it should be well concealed.

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I started on the non drive side chain stay. It was a seat stay donated by the vintage marin (RIP) I gave it a little bit of a tappy tap with the hammer on the inside of the curve to tighten up the radius and tacked it in place



I figured I should check for any clearance issues before going any further so I unbolted the rear axle and rotated it in the jig then threw the wheel in and gave it a spin:


I forgot to take any pictures of the drive side stay before I tacked it in place. It is a chain stay from the marin which interestingly had 3/4" chain stays and seat stays, and I made a bridge to clear the chainring out of a piece of hardox 450 4mm plate. Hopefully the hardox works out well, 4130 plate is ludicrously expensive.


the piece of wood in the middle is a very rough and ready tyre clearance gauge to make sure I don't make any silly mistakes while tacking it together

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  • Guypie changed the title to Guypie's Bike Builds - A paint job and more!

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