WARRIOR LOW RACER TADPOLE TRIKE - Question

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Apr 14, 2021
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Hey Mates - Last time I was on this site was 2008 - Back again and looking to build a "WARRIOR LOW RACER TADPOLE TRIKE" - Can I use alum square tubing instead of steel? - If so what size/thickness? - Thanks for any help Docbob.
 
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Hello there. Welcome back to the pack.
There is a reason why aluminium framed upwrongs use oversized tubing. Rule of tumb, , for the same wall thickness, increase the diameter (or square) with 50%. So a steel 1.5" box section will need a 2" or even a 2" 1/8 box section replacement. Thicker wall won't decrease that a lot, but will make it easier to weld it.
 
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Regular bikes can use aluminium frames because the triangulation is perfect and all the forces run along the tubes. Recumbents use the frame as a beam where the metal is vastly weaker. An aluminium beam will almost certainly fail and fail drastically and without warning. Without substantial redesign I'd not do it. Steel has some give in it which is crucial to a beam.
 
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With the amount of aluminium you need, the weight difference will be small, if there is any.
I have a rear part that is aluminium. But the rest of the bike is steel.
Most weight profit that I hot, was from the steering setup, the wheels and the seat.
 
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Thanks Mate - thought their might be some engineering issues (didn't see any projects using Alum instead of steel) Thanks again - Docbob
 
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Rear triangles are, again, perfectly triangulated so a rear triangle in aluminium can cope with the forces it's subjected to. Those bolted frames look substantially heavier than most steel ones and that's without adding in the weight of the bolts which itself will be no small figure.



This is one of the lightest I've seen and the frame alone is 8kg. They have to use 4 beams to make a box to add enough strength. A Warrior chassis comes in around 6kg depending on length / width etc. Exactly what's defined as chassis can vary from person to person and/or build to build. BB tubes and steerer tubes on a bolt on chassis probably don't count to chassis weight, but they would on a Warrior IMO making the comparison even better for the steel chassis. I'd also expect any bolted aluminium frame to elongate the bolt holes over time.
 
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As it is for weight, than there are other ways to save weight. Use the rear suspension from a mountain bike, use an other seat, change the steering system ad the wheels, use carbon tubes to link the steering.
Then the parts you get. The wheels you choose can make a big difference in weight and roll resistance.
But also with the other parts you can safe weight.
 

Ian

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Nov 7, 2021
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Hey Mates - Last time I was on this site was 2008 - Back again and looking to build a "WARRIOR LOW RACER TADPOLE TRIKE" - Can I use alum square tubing instead of steel? - If so what size/thickness? - Thanks for any help Docbob.
I'm a new boy on the block. I'm trying to decide which material to use. The Warrior plans say 1.5 inch 16 gauge or 14 gauge for a stronger build. My estimation is that the difference is about 3.3lbs or about 10% of the total bike weight. Add the weight of the rider and the difference you are pushing is extremely small. Has anyone built a 14 gauge and can confirm this or tell me I am wrong? I'm not very heavy 78kg but I have friends who are which is the problem. I like the idea of gussets but agree that you just push the stress to the weakest point and I don't want a patchwork of gussets and reinforcing plates chasing chassis cracks. Thanks in advance for the help. I will have more questions later but choice of material is the starting point.
 
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Body weight and bike weight are not equal. Your body is used to moving whatever it weighs and that holds true whether walking or cycling. Bike or trike weight is always extra to what your muscles expect. You can add 20lbs of fat and muscle and you'll barely notice the extra effort walking or cycling but put on a backpack weighing the same and you notice it immediately. Build it in 16swg and tell your mates to build their own. Gussets have their uses as does a pair of braces on a Warrior from the wheel arms back to the main frame to triangulate the rear. It's the easiest thing in the world to build something heavy and then hate to use it because of that weight. Recumbents are already at a disadvantage in going uphill and a heavy one more so. A trike will always weigh more than a bike and keeping weight down should be an aim.
 

Ian

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Thanks Popshot, that's one question answered. Now I've just got to source the material. I live down under where everything is metric and 35mm or 40mm with wall thickness of 1.6mm or 2mm is standard but with a little work I can get 1.5 inch 16 gauge or 38mm
 
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i have built 3 warriors, I added gussets and braces in a few places and stuck with what the plans say, 16g. I'm not near the weight limit, but figured a single point of contact is a bad idea and should be avoided. I figured it would be more of a sound solid design to triangulate and brace, rather than just use thicker steel but still only have one point for all the stress to go through
 

Ian

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Nov 7, 2021
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Thanks Thom G, It looks like gussets and triangulated braces are the way to go
 
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