a silly question

[NNAATZ]

i was looking at ddaws 40, and it had a curved top roller support . the one on my 420 is straight. i know in the book there is the curved one for it to.
why? what is so advantagous about this or not?

[Stan Disbrow]

Hi,

I think it has to do with the 420 tracks being heavier than the 40 tracks.

Stan

[NNAATZ]

that could be, i know there is a differance on how to measure when the tracks are adjusted, bettween the two.

[JimAnderson]

NNAATZ,
The curved roller support is the best way to get the roller midway
between the front idler and rear sprocket .This will give each section
of track the same sag or back bending.With the straight support the
rear section sags more for a given front idler postion.Back bending
in its extreme causes more rapid pin and bushing wear.It also allows
the pads to hit each other causing wear at their contact point.If the
tracks are adjusted properly then either support works well but the
curved support gives you a little more time before serious back can
occur.
JimAnderson

[Lavoy]

The curved support was used on 5 roller 40's, and 5 roller 420's under serial number 100,000. It was prone to breakage, and was replaced on the Phase 2 420's and 430's by the straight support. At this time, the straight support also became the replacement part for the 40 and early 420.
Lavoy

[NNAATZ]

ok that makes more sense, i knew the curved ones where prone to breakage but not as replacement as phases changed, looking at mine i see how the pin wears as it sags
thanks nick