The WD part is a hexagonal bar with a 1/4" dia. threaded section machined on each end. Once the end that fits through the mudguard has been tightened the regulator box is fitted to the other end. This allows for removal of the regulator without having to get underneath the mudguard to access a bolt head/nut.
The hexagonal portion is a 1/4" whit spanner size and approx. 1/2"-5/8" long. The 1/4" dia. threads are cycle thread. Lengths of the 1/4" sections can be readily calculated from the thickness of what they pass through plus the thickness of the washers, nuts etc. used to secure them. I would advise loctiting the nuts under the mudguard...they are difficult to get at with the wheel in place if they come adrift. There was no vibration isolation as such. When making these parts I generally extend the upper threaded portion that the regulator fits on and fit a steel washer, a rubber washer (about 5/16" thick) and then the regulator...and finally a plain washer and a nut and locknut.This allows for 'compressing' the rubber washer to the desired degree...Ian
email (option): ian@wright52.plus.com
email (option): unpob@yahoo.com
email (option): unpob@yahoo.com