RN Box rebuild questions

[Scarlet O'Hara]

Thanks Dave, photos a great help, I've got a downpipe that fits that route and the silencer so just need to sort out the tail pipe and bracket.

[Dennis Nicholas]

Scarlet (and any others new to 7s.
Reference to the front axle caster angle and the previous wright ups of how to change it. The one method of twisting the radius arms with a big Stilson after loosening the nut at the front SHOULD NOT BE ATTEMPTED as that puts a twist in the spring and thus loads up the spring shackles wrongly in the spring eye giving heavier wear; also it ads a twist to the radius arms which puts a wrong loading on the joint where the arms meet at the front chassis cross member.  It is a pity that method was not edited out of the re-write of the book.
The only way to achieve turning the axle and thus changing the caster angle is by putting a wedge (very thin) between chassis and spring.  The ends of the radius arms at the chassis front cross member should then NOT be forced to line up with the mounting bracket but the bracket must be moved up or down and maybe packed out so that the arms meet the ball joint (or pin through Metalastic joint on later cars) and the pin can be inserted without any straining.  The chassis nose-piece had the correct angle designed into the flat surface where the spring mounts. There may be reasons why over the years that nosepiece angle has changed.  Sounds like a lot of faffing around but it is well worth the effort to get the front end right. 
To my mind the Big seven shackles with their coarse (acme?) threaded pins and bushes look to be a wonderful engineering advance though more expensive.  With the thread there is more surface area to share load wear, especially front and back loading and the pins can be rotated to position the front and rear plates of the shackles and the tapered ends of the pins to just the right position.  There may be something clever about the screwing motion imparted when the axle end moves up and down??

Dennis

[Dave Mann]

Make sure that the tailpipe slides over the stub on the silencer, the first tailpipe I made slid inside the silencer stub and it was like driving with the brakes on. If you look at the RNS chassis extension you will find the hole for the tailpipe bracket. As far as I aware nobody makes an exhaust system for a 3 speed RN I got fed up of making replacements in mild steel and took a whole system to a stainless steel exhaust manufacturer who copied it.