Rockstar pro
Oh right fivestar is just the 9 inch, got confused
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They’re out of stock iirc
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No worries.
I have access to a tig welder and people who a have lots of experience with them so the frame itself and welding aren’t in question. I’ll just need to explore what axle bolt material would be the best for the application and that is where my experience ends.
Maybe a truck maker would be able to provide some insight. 12.9 stainless steel treated with something will be a good enough start.
12.9 is high tensile strength (google just says “quenched and tempered alloy”) but she ain’t stainless. Do you mean like zinc coated 12.9 or something? That stuff can look shiny like stainless
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I don’t think this exists. Stainless steel is weak, relatively.
And pretty sure multiple grades of stainless, but 12.9 ain’t one of them. I think A4-80 is a good grade of stainless, but I wouldn’t use stainless personally.
12.9 (or 10.9) steel for the win 
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See this is the info I need to be hearing. Yeah steel steel, not stainless cheese.
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If you weld all the way around, with proper technique, then it’ll be fine. That photo looks like you just put a tack weld, which is definitely not enough.
That ain’t a thing. And even if it were, any steel with a significant heat-treat on it (anything high-strength, basically) will be significantly affected by the heat of welding, resulting in it not being 12.9 anymore.
If you want to retain strength higher than ~50KSI (hot rolled mild steel basically), you would need to do a post-welding heat treatment.
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To be fair, I did offer a “good” stainless choice as well as saying steel is better 
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Thank you. That was just a photo I found that sparked the idea. I have done nothing for the adult kart yet. It just seemed like an interesting way to get a fixed axle to attach to a square tube frame.
I’ve considered:
- somehow pressing and securing an axle in to tune frame
- a huge structural axle that steps down to 12mm on the ends, welded to the frame so it’s fixed
- shoulder bolt method and having a thread drilled in to the frame area somehow
- bolt welded to frame making an axle
Please tell me if there are any obvious solutions I’m missing
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There are some very strong, hard stainless steels out there, and you can even get fasteners made from them. But they’re egregiously expensive - I’m talking over $1/pc for M4. 17-4 and 17-7 come to mind. You can make springs out of that stuff.
Yes, I would try this which is similar to, but not, what you listed:
- a huge structural axle that steps down to 12mm on the ends,
weldedbolted to the frame so it’s fixed
But a welded one would work too
Welding can affect heat treatments and structural strength
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Do you imagine this huge axle as square in the middle or round all the way through?
This, but using a coupling nut welded into the frame?
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I’m picturing it as round, but it’d be even better if it was square (with round ends) now that you mention it
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Why not just make the frame in such a way it has two (or more) holes, which the axle passes through?
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I wasn’t sure if a 12mm axle all the way across the width of a kart would hold up well. If I reinforced the frame with cross supports so it has more holes to go through, it would spread the load more.
Googles super long 12mm double threaded axle
Lots of fully threaded one. It’d be cheaper and uglier than getting a round 12mm rod and having it threaded though. I bet I could find someone to cut threads on the end of one for me though.
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Flexy deck recommendations that are similar to this - light with a bit of flex & drop-through - and that there is an enclosure for?
if you where to choose between land surf 165mm pneumatic wheels
(https://land-surf.com/products/xcell™-rs™-e-skate-tires-165mm-x-62mm-set-of-4)
and Trampa 203mm pneumatic wheels (deep dish with their new golfa tires)
(DEEP-DISH MEGASTAR 8 Hub with SKINNY BBStar Spoke 3.75 x 2.5 Inch)
which one would you go ideally go for? (leaving cost out of the equation)
Do yourself a favour and select a deck that there is a good enclosure for.
One such list (of multiple) is here:
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