MangPong wrote:
Hi Mr Rumbles
I'm not a qualified engineer so I just wanted to query your suspension design, which seems to be massively strong, but the UCA is fastened to the chassis by what looks like a couple of 1/4" bolts, which also hang way out... and 'looks' odd to me.
Was this deliberate, as an immediate weak-link (so you know where to check first), or am I just worrying unduly.
Not criticism - just curious. Best wishes, MangPong.
MangPong, Thanks for the comment.
The rod bolt that attaches the Upper Control Arm (UCA) to the frame is actually a hardened 3/8" bolt. You are correct, if there is a weak point in the design, that rod bolt is it.
However, I took my queue from the Yamaha engineers who designed the donor Raptor 700. The Raptor upper A-arms were very lightweight aluminum and the attachment point on the frame was a .060" steel tab, that is weaker than my 3/8" rod bolt. The donor Raptor was built to withstand rock hopping and jumping the whoopees, where I will be using it on more civilized streets with an occasional speed bump. If my calculations are correct, the weight on the front end should be close to the donor Raptor as well.
All that said, I admit that I also looked at the rod bolts thinking they seemed less than beefy. I still have quite a bit of adjust-ability remaining on the upper A-arm ball joints, so I could thread-out the ball joint and thread-in the rod bolts to reduce the stress on them. However, that will change my front end geometry.
I plan to keep an eye on the rod bolts as I test the car. If there is a problem, I can replace the rod bolts with a beefy bracket.