early 80's rear mech / chain length question

[foz]

I've been making slow progress on my batavus: viewtopic.php?f=23&t=346692

Tonight I was fitting the rear mech, and I'm not sure how to set chain length on one this old... 1984-ish zeus supercronos (campag NR/SR copy, more or less).

I've always dealt with late 80's or newer, where I've set chain length by either both jockey wheels vertical and aligned with the wheel axle while in large chainring and small sprocket (shimano way), or large chainring and large sprocket, plus a couple of chain links (campag way)

Should I be using the same methods with an earlier non-indexed mech? or is there another way?

And just to check - there isn't a base plate between the rear mech body and the dropout. That's the way I took it off the last frame it was on, and it seems to go on and work fine like that, but I know some mechs (mavic, for example) have base plates that often get lost.

thanks!

 

[Midlife]

Campag / Zeus of that era just can't cope with the rear cog range of the slant pantograph jobbies from Shimano and Suntour, ok Shimano are strictly not a slant pantograph but hey...all in name.

It's just trial and error, and in the real world just don't go for the big ring at the front and the big cog at the back or it all goes pants...as does using the small ring and small cog at the back as it bounces in the chainstay LOL

We usually went for the shorter chain to avoid touching up the paint on the chainstay, or had it chromed ..

Shaun

 

[foz]

Thanks Shaun - that's helpful, but I'm still not sure how long the chain should be! Shorter than it would be set with a later type mech?

 

[Nob]

Re:

Jockey wheels at 7 o clock is a starting point

 

[torqueless]

Re:

Personally I set 'em up on the small chainring and smallest cog with the longest chain possible that still keeps tension on the derailleur spring. Imo if it looks/works wrong with that chain length on the big ring and the biggest cog then the derailleur is being asked to cover too wide a gear range.

Fwiw: 16 1/4" stays, 13-21 block, 42/52 rings, Campag. NR mech- 108 links in the chain.

And just to check - there isn't a base plate between the rear mech body and the dropout. That's the way I took it off the last frame it was on, and it seems to go on and work fine like that, but I know some mechs (mavic, for example) have base plates that often get lost.

I always wondered about this too, 'cause my mech flops about in a small arc around the upper pivot bolt until the chain goes on. but judging from the '75 Campag catalogue there doesn't appear to be anything missing- there's just the bolt and its housing, no little washers or anything, so I assume that that movement is 'normal'..

 

[foz]

Re:

OK, thanks! will experiment with the chain later.

"flops about" is an accurate description of the mech with no chain - that's how I took it off the previous bike, and it seems correct, I'm just used to more modern stuff that works in a slightly different way