Recumbent Trike – Steering pull solved
The steering pulling to the right bothered me. The 1.5 to 2 degree difference in the caster angles was there and it had to be the clue I needed. However, the angle readings were varying on each try but overall the right wheel had less caster than the left. I really did not want to cut off the arm and realign the whole thing again as that was not easy the first time. Searching at lunch for caster steering problems, I came across a Quora post that said if the caster is uneven the car will pull towards the side with less caster. https://www.quora.com/How-caster-angle-affects-to-the-vehicle-dynamics. This was the answer I needed!
So, I decided to cut the front tube perpendicular to the long axis. This would give me the ability to adjust the caster without messing up the camber. WIth a 2 degree angle error and 1.5″ tubing I would need to have a slot 0.078″ or just over 1/16″ . One slice with a cut-off blade in the angle grinder would be about right. I placed a straight edge against the back of the spindle tubes and marked across the arm.
Measuring the angle exactly is very hard. So I enlisted my wife’s help and used a pair of 2 foot long winding sticks placed against the front edges of the steering bearing cups. Sighting along these from the side I could see the angles were plainly different. Winding sticks are used in woodworking when flattening benches, aligning jointer beds and other areas where you are looking remove twist in a surface. Below, I am holding a ruler in the position where each of the winding sticks was placed.
After slicing through the top and then the sides, a bit of downward pressure closed the gap. A quick check with the winding sticks again showed that they were now almost exactly parallel – the difference was gone! Now it was time for a couple of hot tack welds and a test ride. You can see the gap at the bottom, where the cut is folded and that it is tight at the top.
This did the trick. I can now go 100-200 feet hands free with very little drift. I will still tighten up the steering a bit to add some friction as bumps will cause a deviation (yes more caster would probably help but I am going to leave this one alone now. So it was now time to weld over the length of the joint and start to grind flush. It gets dark early now so I was not able to completely finish and it will be easier when the bike is disassembled for painting.
Now I need to figure out the rear chain skipping…