Bill Hamilton <
[email protected]> wrote in
news:[email protected]:
> rorschandt <
[email protected]> wrote in
>
news:[email protected]:
>
>SNIP<<
>> Thanks, I do too, BUT, it is very labor intensive to build, and so far does not have torsional
>> rigidity as I'd like.
>
> It's difficult for me to tell in the pictures, but it looks like you didn't triangulate the top
> and bottom of the frame, or much of the cross section. Breaking the frame down into triangles will
> strengthen it greatly. Putting x-shaped supports within the frame attached to all four 3/8" rails
> will help prevent twisting on the long axis due to bumps and such.
This I did after the pictures were taken. Although it helped tremendously, I am probably not going
to pursue mods to it as the seat is just way too high making center of gravity a difficulty. The
rider is also too far behind the front wheels for proper handling. I learned a lot from it! (~:
> I'd also recomend, if possible, frame members that go from the lower weld on your kingpins to the
> upper welds where the front wheel arms attach to the central frame. Right now all the weight on
> the front wheels is applied as a moment where the arms weld to the frame. Triangulating that will
> move most of that into a compression force along the diagonal member and top member, and a tension
> force along the bottom member.
I'd thought of doing this as well. I wasn't sure if I should brace the four members 'to' each other
about in the middle of the span, or a lengthwise tube from top to bottom as( I think)you described.
Large diameter tubing is far easier.
>
> If you're completely unfamiliar with how this works, do a web search on "engineering statics" and
> you'll get a number of hits for online course materials. Don't worry about the math, just look at
> how 2d and 3d trusses react. A trike frame can be treated as if static because ideally it won't
> warp. If you want to talk more about this, email me (remove "nos" from my address).
Thanks for that, I'll have a look later, when I've more time.
>
> I showed these pics to the guy welding my homebuild and told him of the problem you're having. He
> suggests small triangular pieces of sheet steel to brace the frame member intersections. I don't
> know that I agree with him (I prefer more frame members), but I'm just an engineering student
> while he's the welder.
>
I think that you are correct. It was the "square" attempting to be a "diamond" shape.
> Your project has inspired me, though. I'm fiddling around now with designing a fully suspended
> framed trike with lean-steer and everything. Exactly what I needed to start doing in the middle of
> finals week.
>
Kewl. Send pictures. happy trails, rorschandt
