4.7m (15ft) Boat Trailer
Quad Wobble Rollers
Adjustment to the overall length of the wobble arm can be made if the boat strake positions will interfere with the rollers. It is recommended not to exceed 19" (485mm) overall SHS length. Shorten the overall length where possible.
If modifications are made, change the mounting hole position so it is 25mm offset from centre.
Correct welding of the wobble shaft onto the arm is required to ensure good strength.
Due to the larger mass of the wobble shaft, a hot weld is required to give good penetration into the shaft, taking care not to blow through the thinner wall of the SHS.
Insufficient weld penetration of the wobble shaft/arm may cause the wobble unit to fail in service.
As per the dual roller setup, the wobble rollers shown in this plan are 130mm diameter "Grey Barrons" with a 26mm diameter bore available from most trailer parts suppliers.
Changes may have to made to the overall shaft length between the washer and split pin hole with different wobble rollers.
Double check the internal dimensions of your rollers before fabricating
The final component for the quad wobble setup is the quad arm as below. Check U brackets are square to the quad arm and sitting nice and level on the arm before applying good, strong welds.
It does pay to clamp the U brackets to the arm prior to welding, as they tend to move around whilst being welded.
Mounting of the wobble arms to the quad arm is with M12 x 70 galvanised bolts and M12 galvanised nylock nuts. Rollers are mounted to the wobble arm with the addition of an M20 galvanised washer and stainless steel split pin.