LWB Frame Construction

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Sep 4, 2019
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I have some general questions regarding custom frame design and construction for a
LWB recumbent. I have never built a custom bike before, so please forgive me if some
of these issues are well-understood by the experienced community.

My hope is that a general discussion can be developed regarding design, materials,
and welding techniques.

Here are some questions I have :

Design :
1. I would assume that a truss-type design such as on the Wildkat would be more difficult
to construct, but be lighter and more rigid than a single-member frame, as found on
the Marauder. Are these assumptions correct?

Materials :
For building a single-member frame for a LWB recumbent :
  1. Which tubing cross-section type would be more rigid? Less expensive? Lighter?
  2. What wall-thickness values are proper?
  3. Where can suitable round or square cross-section tubing be purchased?
Welding :
  1. Are most builders using stick-welding for frame construction, or MIG or TIG?
  2. How does stick welding compare to MIG for constructing bike frames?
(Brad seems to have good success with stick-welding using 6013 rod.)
 

Radical Brad

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A timely question!
I say that because I am starting a video series that will show a complete SWB build as well as tips and tricks for all tools required.
The rain has kept me from starting this week, but I should be at it soon enough.

Brad
 
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Single member 40x20x2.0mm or similar. For a truss I'd drop to 1.5mm wall with a size around an inch square or round. That assumes a typical weight rider. It's very easy to make a bike / trike unnecessarily heavy and accordingly less fun to ride. Keeping weight down is a hard decision to make as failure comes that much closer. As to where from that would depend on where you are. I've used ebay a lot for my metal supplies as well as Metal Supermarkets.

Stick is quite hard to use on such thin metal. Brad can do it because he's an expert. I'd expect most people making these things use MIG, though TIGs have got much cheaper in the last few years. Stick is great for heavier work for amateurs. I can do a passable job on 3mm thick angle for a car trailer with a stick but below that I'll go MIG all time. If I tried to use a stick on 16SWG I'd be blowing holes in everything. The MIG learning curve is fairly easy and most people could produce a passable effort after a couple of days practise. Even the cheap MIGs will have sufficient power for a bike frame. Never used TIG so can add nothing to that area.
 
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Sep 4, 2019
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Popshot -
Thank you for this very helpful information. I need to purchase my first welder, so your comments on stick vs MIG for bike frame construction is much appreciated. From the limited research I have done, it seems that an inexpensive DC MIG welder might be a good, or at least acceptable, choice for a bike frame project. To Brad - if feasible, I think some content that compares stick vs MIG techniques for new bike builders in your upcoming build tutorial would be very well received - al least by new bike builders like myself. Never having welded before, I plan to look for a course at a local community college before I attempt constructing my first frame.
- Bender
 
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