Re: The Bent Zombie Tribrid Tadpole Trike (build phase)
I hada suspicion that where I'd gone wrong was the angle & length of my tie rods... alla that had gone together waaay too easy to be trusted, I'm hardly an "expert" with such things but I do know that if it's
that easy, ol' Murphy is takin' the opportunity to have a few lols. So, after finally finding a bit of info on the issue
http://www.thedirtforum.com/bumpsteer.htm I decided to experiment with all of the angles and lengths just to see what happened, if it got better or worse *shrug* Time consuming as I hadta fabricate stuff jus' for testing... but as the whole project hung on just this one problem it didn't matter if it took time, it was an "all or nothing" scenario and there was no way in heck I was gonna call it quits b'cause of somethin' like this.
So, lookin' at it the most obvious suspect was the angles of the tie rods vs the A arms, essentially opposite they crisscross, making an "X" because the steering plate was so low, the spindles so high. Given the results it was obvious this was just plain dumb. So I made a coupla 1 & 1/8th inch drops for the spindle's control arms, lowering the outer tie rods ends to the same as the ball joint's lowest point (any lower and I'd worry about hittin' stuff w/it) - while the tie rods angle was still not the same as the A arm, it was reduced significantly & after depressurizing the shocks again I found that I'd reduced the toe out by 2" just from that mod alone!
AH! It's defo the angle that's the problem, thing is, doin' some really basic math I figured it wasn't gonna be enough to just lower the outers and raise the inners, at most that was gonna reduce it by 3-4" and I had a ghastly 6" to rid myself of... but I was makin' progress and it belatedly occured to me if it was that sensitive to angles, length was no doubt important too...
So - I flipped the steering plate over & cobbed a patch for the tie rods, giving them 3" of separation so they'd have the same pivot points as the A arms & cutting the rods back a bit & raising them so the A arms and the tie rods would be almost the same, sounds simple enough but this raised havoc with the mounting as I hadn't designed the clearance in for the plate to be upside down... or rather I'd had it upside down to begin with and was only now realizing it... whatever lol - it WORKED!!!
In it's new configuration & under max compression (shocks depressurized completely) I've now only 1/16th inch of toe out, effectively none under any riding conditions! The remaining 1/16" is doubtlessly because the tie rods are still slightly longer than the A arms, they hafta be as there's no other place for the steering plate *shrug* but hey, I'll take it! Here's some pics, the second is w/just one shock down - still no bump steer effect w00t!
Yea, I've still gotta finsh up the welds on the plate & pretty it up, make gussets for the spindle drops & weld those up too, even drill a coupla holes and lower the linkages on the handle bars 1/2" to make up for the ratio changes resulting from the plate reconfiguration, it's waaay too sensitive now - but that's simple as pie & I left plenty on those tabs for that kind of adjustment.
Forgive the rants, I can't tell ya how much this had me worried, or jus' how psyched I am now that it's solved -
finally I can move on to less dire things, this problem was WAY outa my "comfort zone" lol