Any down side to using 1" tube?

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Feb 7, 2008
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Nottinghamshire England
That would depend on:-
what you were building
where you were planing to use the tubing
and your weight
and where you planned on riding
and ....
 
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I can easily aquire 1/16 1 inch tube. Any down side to this size?
For the main parts of a frame, yes, unless it is used in a scaled-down model for a non-obese child.
 
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Square or rectangular tube gets it's strength primarily from the length of the sides. In maim beam use for a recumbent that would be the vertical face that resists the most load. For some areas inch square will do. For main chassis beams it will not unless, as said, for an unusually light rider.
 
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So my best bet would be to go to 2 inch. Correct? And thank you for your input
38mm or 40mm in 16 gauge is fine for most situations 50mm is a bit OTT, but can be used.
I had my first made in 40mm x40mm @ 2.5mm thick, was unbreakable.....but very, very heavy. Everything since has been in 38.8mm square (16 Gauge) or in 38mm round or 43mm round.
Round can look much nicer, but is harder to get nice looking welds (if you are a learner). Square tube and straight welds is so very much easier.
 
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I believe @FrankCrank uses 2 x 1 stainless on his creations.
The problem with a trike and a vertically oriented spine might be twist/flex over rough terrain perhaps?
Square tubes have less of a tendency to twist I think. If we look at the commercial trike world what do they use?
Predominantly ROUND or SQUARE how many Vertical Oblong trike manufacturers are there out there? Why would that be?
 
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I believe @FrankCrank uses 2 x 1 stainless on his creations.
The problem with a trike and a vertically oriented spine might be twist/flex over rough terrain perhaps?
Square tubes have less of a tendency to twist I think. If we look at the commercial trike world what do they use?
Predominantly ROUND or SQUARE how many Vertical Oblong trike manufacturers are there out there? Why would that be?
Round tube has a higher resistance to both flex and torsional twisting than square for any given weight. Rectangular has less resistance to twist but greater resistance to flex than round or square.

Commercial makers take one of two routes.
  1. They make them as well as possible which usually means thin and round or maybe even oval in places. Round just looks more professional and you can't charge top $$$ for something that looks less than that.
  2. They make them as cheap and easy as possible which means square because it's easier to work with. You have no difficult fishmouths to make and you don't have to consider orientation of anything before you cut it.
Considering vertical and lateral loading. It is quite easy to envisage such straightforward loads. The chassis on any recumbent is most stressed in the vertical plane simply because of rider weight. Cornering will stress the chassis sideways (tadpoles will anyway - deltas usually less so) but not to anywhere near the extent of the rider weight stressing it vertically. Indeed there's a built in safety mechanism to prevent sideways over-stressing of the chassis occurring and that's that the wheels will taco well before that happens. In the vertical the wheels are strongest, will hold up and the chassis can bend first. There is zero chance of chassis failure laterally before the wheels have let go at which point you're more concerned with bending yourself. In practicality the wheels can be considered a crumple zone protecting from side forces.
Now to consider twisting forces. Here I'll readily concede rectangular performs worst. I'll also concede this is where my knowledge lets me down as I'm unable to compare twisting forces on a trike against vertical or lateral forces other than I expect they will be higher off-road. I don't ride off-road so I've never had to consider such forces as relevant but if I did I'd be choosing round as stronger than square.

Calculated deflection in the vertical for a 3 foot beam and 200lb weight. All 16swg steel tubes and all weighing the same.
Square 30mm = 1.78"
Rectangular 40mm x 20mm = 1.18"
Round 1.5" = 1.42"

Rectangular is stronger simply because you place most metal where it will resist the highest load by taking metal from areas seeing less load. If you have greater worry about twisting loads you shouldn't choose rectangular. If you can measure twisting loads and compare them to vertical and lateral as to which is the greater threat then please enlighten me.
 
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Thanks for the mention Danny.

Here's a couple of pics of my trike during build:



As stated, 2"x1" stainless was used for the main sections, wall of sub 1mm. Reason I chose rectangular section was most loading is vertically. Additional struts added below seat area where most load applied, and to the boom section to avoid flex.
You would need to TIG weld something like this, and access to stainless suppliers (abundant here).
Very small amount of twist is evident going sharply round a corner, but hardly noticeable. Have been using it a lot these past few years and no issues.
For your own project you can build from plan, or try something a bit different - all depends on your skill-set and what you have easily available to build with. Anyways, good luck with it all.
 
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So with all being said. Thank you to all that responded. I bit the bullet and ordered online, delivered. Ouch on shipping, but that's life.

1 1/2 16 gauge square tube. 60 and 84 inches.

.625 x 36 inch cold finish round 1018

1.5 x 1/8 flat bar

Pillow blocks

Now time for finding a local to get the hubs.

I tried the " premade " washer route but can't find anything in non harded or plated.🤬

A well, it adds to the fun😁

I'll probably end up buying new as there aren't many " bike junkyards " around.

AND I have a reason to hit up the new Harbor Frieght in Escanaba.😁😁( Wife's gonna be pissed LOL)

Thank you to all the Gurus on this forum. You got some kick ass info, insight and general knowledge. More than enough for a food like me. 😁
 
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