"Building a welding JIG first" - design process and thoughts

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Hi guys, since I have multiple frame jobs in the shed and in my head... I will pick up this work when I am nearly finishing my SWBO bicycle.

I am thinking about entering the next build off too, since I have a bog standard and beautiful bike I want to change the frame a bit.

And I'll use this topic for notes:


Currently I am manifesting a more professional frame building shop and work on custom parts. Yes I am taking my time ;)

But since I am enthusiastic and slowly learning about the works of (among many more) Viktor Schauberger and Richard Buckminster Fuller, I am thinking about material use and the unforced application of 'sacred geometry' in my works. Or at least learn and see what works... go with the flow so to speak.

That means I am orienting my methods and tools depending on the design and frame materials I will use, wood or metal.
Building a custom frame made out of wood is a challenge and a deep fascination for me.

But finishing the frame JIG the the starting point of that orientation!

Some inspirational pictures I found on the internet:
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Screenshot_20231122_143626_Instagram.jpg

Beautiful!

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Wood.


Screenshot_20240204_181124_Instagram.jpg

Drivetrain :heart:
 
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Very similar to the Chopsource design I was going to modify for bicycles

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Captain, I took a better look at this JIG. I saw the chopsource version with plates and bolts and you have to find your own steel beams with that. I thought its pretty cool! Its a great concept they have worked out.

I took a look at these aluminum extrusion profiles again. They are just so easy to put together and combine.

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This is the 8080 (80x80 millimeters) version.

Officially, a 70x70 or 80x80 steel beam is stiffer, but these profiles are cheap, easy to use and probably tough enough (will make some calculations).

My thought on using this specific size is that its an easy size for the bottom bracket with clamping (68mm mostly). And if I use a wider profile, the spots that need welding/brazing are harder to reach.

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Thoughts and notes.


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Working out this concept. With ideas from the chopsource design (mainly the headtube).
Next week some 3D models!

Notice the BB clamp separate from the seat tube clamp.... custom bikes!

CBurke also uses chopsource I guess: you can see it later in the video.

 
Hi guys, I made a start on the 3D model.

The JIG main beams/profiles are made with a simplified 3D model. I did make the weight the same, so I'll get an idea. This way I can choose to mount it on a rotating engine stand.

The model is a concept, improvements will be made.

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Angular plate. Large holes are for bolts/assembly.
Small holes are for the alignment. If I use M5 allen screws, the heads will fall neatly in the profile slot.
My thought is: If I loosen the M8 bolts to adjust the JIG, I don't want it all wobbly with too much play, so I can retain the alignment.

1000021491.jpg

I used the chopsource idea for this.


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Aluminum block with a centre M20 thread for the headtube. Model needs refining.

1000021494.jpg

Same angular plate, like above, with holes to make it a little lighter. Its 4mm steel plate at the moment.


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Current assembly.

The main beam is 2000mm long. Obviously for long bike frames. This might pull the smaller parts out of perspective.

Next: Rear shaft alignment plates, its shaft and the cones to keep the bottom bracket round and clamped down.
 
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3D model and thoughts update:

I implemented a 8080 extrusion profile stepfile. Looks much better and realistic!

I updated the corner plates:
Made them a little higher, yet removed a corner so its more like a puzzle. This means a little more stiffness and the same, or better adjustability.

The bottom bracket alignment plate is a tricky one. My goal is to keep it simple, have lots of space for welding and a stiff/rigid setup. Yet have many options.

I like options :grin:

I plan to build a bike in the future that can have a tube that goes under the bottom bracket like this:
43e4789168742939a1c49f5f087e4f78.jpg


For the bottom bracket cones I will utilize the M8/8mm bolt size, so the cones can also be placed in line with the seatpost. In the profiles slot.

I thought about the number of bolts to loosen/secure when adjusting. I have no issues with the current amount. Takes a few minutes more to secure it all.

Plate thickness, details, lots to be done, but very content with this so far!

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Rear shaft fixture setup. Bottom picture the lowest setup.


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Bottom bracket first concept. You can see the height measured here.


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Hi guys,

Working on the BB clamp section for a bit.

I designed something that looks like 'male parts', made me giggle like a kid :bigsmile: wasn’t on purpose.

The idea behind it is: To be able to hang the bottom bracket tube/pot anywhere and create space for welding, with a profile or plate that is stiff enough to do the job.

1000021822.jpg

1000021821.jpg

When you see the adjustment options, you can see that its idea is to position it anywhere and create working space where you need it.



But maybe I am thinking too much about it and just work with a profile that can slide up-and-down, plus a bit left to right. Like the following picture:
1000021823.jpg

The plate must be thick enough to prevent it from bending.


I looked at other builders jigs that work with custom bicycles and the chopsource jig seems popular here:
1000021820.jpg

Screenshot from 'CBurke' his youtube channel. Credits to him.



Feel free to leave your thoughts.
 
Just some forethought for you, CBurke and all those chopper style builders are using heavy wall tubing and thus typically no back purge. Would you consider an option for being able to back purge the head tube, seat tube, or BB in the future?

Another good example for you would be Mike Laird

 
Just some forethought for you, CBurke and all those chopper style builders are using heavy wall tubing and thus typically no back purge. Would you consider an option for being able to back purge the head tube, seat tube, or BB in the future?

Another good example for you would be Mike Laird


Wow Captain, appreciate that link, thanks.

Just watched it and my observations:
  • At around 5:30 he explains that he keeps the frame in the fixture the entire time.
  • He also explains that most production facilities 'cold fix' the frame afterwards.
I thought that his explanation makes sense, that was my angle of attack too. Keep the frame in the fixture and design the fixture in such a was that you can keep it in the fixture as much as possible.

  • There is a high BB in relation to the JIG so you can reach/weld underneath while its in the frame.
  • His JIG can completely rotate 360 degrees.
  • There is ARGON gas going in the frame. That is the back purge you described Captain, am I right?
  • He welds the inside welds first and then the outside welds to 'create' as much as an 'even' tension in the frame as possible (that's experience).
More things I want to think about:
Maybe a laser pointer in the JIG for alignment. This can be added afterwards.

The seatpost, BB and headtube fixture: Is it a cone or a cylindrical fitting? I think it is a cone since a cylindrical fixture can get really stuck in there. When you weld steel, you can get 'weld thickness' on the inside of tubes. Plus: I read that it should be the same as the frame material, which is logical when different materials have a different expansion coefficient.

Awesome!



I want to think as much as I can about this, since I'm seriously looking to do this professionally in the future. I'm currently a bit cautious saying I want to do it full time, but that is a personal fear I will work on when I get more experienced. I enjoy my current job too.
To answer you question @Captain Awesome : Yeah I'm willing to consider the 'back purging' option. Start out with heavy wall CroMo tubing or mild steel for cruisers. Then work my way to thinner walled bikes (Klunkers, Mountainbikes etcetera).
But a thing I am eager to learn more about is brazing or even TIG brazing. I love the look, the capillary function of brazing and the lower heat.

Paul Brodie (from Canada) is a great youtube mentor in my view:

 
Wow Captain, appreciate that link, thanks.

Just watched it and my observations:
  • At around 5:30 he explains that he keeps the frame in the fixture the entire time.
  • He also explains that most production facilities 'cold fix' the frame afterwards.
I thought that his explanation makes sense, that was my angle of attack too. Keep the frame in the fixture and design the fixture in such a was that you can keep it in the fixture as much as possible.

  • There is a high BB in relation to the JIG so you can reach/weld underneath while its in the frame.
  • His JIG can completely rotate 360 degrees.
  • There is ARGON gas going in the frame. That is the back purge you described Captain, am I right?
  • He welds the inside welds first and then the outside welds to 'create' as much as an 'even' tension in the frame as possible (that's experience).
More things I want to think about:
Maybe a laser pointer in the JIG for alignment. This can be added afterwards.

The seatpost, BB and headtube fixture: Is it a cone or a cylindrical fitting? I think it is a cone since a cylindrical fixture can get really stuck in there. When you weld steel, you can get 'weld thickness' on the inside of tubes. Plus: I read that it should be the same as the frame material, which is logical when different materials have a different expansion coefficient.


Awesome!



I want to think as much as I can about this, since I'm seriously looking to do this professionally in the future. I'm currently a bit cautious saying I want to do it full time, but that is a personal fear I will work on when I get more experienced. I enjoy my current job too.
To answer you question @Captain Awesome : Yeah I'm willing to consider the 'back purging' option. Start out with heavy wall CroMo tubing or mild steel for cruisers. Then work my way to thinner walled bikes (Klunkers, Mountainbikes etcetera).
But a thing I am eager to learn more about is brazing or even TIG brazing. I love the look, the capillary function of brazing and the lower heat.

Paul Brodie (from Canada) is a great youtube mentor in my view:


I also prefer a locked in welding position and then applied heat/tension. Cold setting or table shaping is just waste in my opinion. I’m all about eliminating steps and any secondary work is just non value add
 
A few modelling updates.

For the BB I decided to go for a thick walled, small square steel tube (30x30x4mm). Reason for a small tube is simply working space. I will close and weld the ends for a stiffer end product. Clamp it with a plate like the chopsource JIG.
The plate has slotted holes so you can position it with an angle. And slide it up and down.

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For the other side I did the same. But since its the seat tube, the angle 'options' are different:

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The seat tube will have a aluminium extrusion profile, because of the way the seat tube is held.
 

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