TECH ADVICE ON POSITRON REAR DERAILLER

Polly

Hey there everybody on rec.tech

I am currently messing around with a very old shimano positron rear
derailler. Its a bit infuriating since I dont really have much info on this.
I was wondering if anybody new of a website where there might be a diagram
discusing adjustment of this type of derailler. Or any type of advice...
woudl be appreciatted.
Basically the derailler is somewhat bent, that I fixed..however problem is
it just keeps shooting into the wheel. I am preplexed as to how one adjusts
the limit on one of these or perhaps that is fixed?

Thanks
Polly

S. Anderson

Polly" <polly@cyclescanada.com> wrote in message
news:ZomdnbvLuIwrEQzdRVn-gg@look.ca...
> Basically the derailler is somewhat bent, that I fixed..however problem is
> it just keeps shooting into the wheel. I am preplexed as to how one
adjusts
> the limit on one of these or perhaps that is fixed?

I seem to recall there WAS a limit screw on there somewhere..is there a
screw in the middle of the derailleur body? That one screw might be
intended to do BOTH limits..sort of a fixed amount of swing and you're
setting the bracket of swing. I also think some had dual limit screws, like
a normal derailleur, but I'm not sure about that. Wish I could help more!

Cheers,

Scott..

Polly

Thanks Scott

theres no dual limit screws on this baby, or it might be the case that they
were and they are gone.
I was thinking that middle screw might adjust the limit as well.
Its kind of a weird situation as no one has really posted any diagrams as to
fixing it, I do seem to remember theres a really old manual that might have
a section devoted to it. I guess I have to figure this one out and post the
results, I was kinda hoping Jobst or sheldon might pipe up with a response
to fixing it.. oh well

Thanks
polly

S. Anderson

"Polly" <polly@cyclescanada.com> wrote in message
news:Q-SdndxSK7FnJQ_dRVn-hA@look.ca...
> Thanks Scott
>
> theres no dual limit screws on this baby, or it might be the case that
they
> were and they are gone.
> I was thinking that middle screw might adjust the limit as well.
> Its kind of a weird situation as no one has really posted any diagrams as
to
> fixing it, I do seem to remember theres a really old manual that might
have
> a section devoted to it. I guess I have to figure this one out and post
the
> results, I was kinda hoping Jobst or sheldon might pipe up with a response
> to fixing it.. oh well
>
> Thanks
> polly

You know, now that I think about it more, I think that screw sets the upper
limit. I think the chain has a disc after the last cog that prevents the
chain from falling off on the bottom. Unfortunately, there weren't that
many of those things and they were rather problematic.

Good luck!

Scott..

dianne_1234

On Thu, 29 Apr 2004 19:13:19 -0400, "Polly" <polly@cyclescanada.com>
wrote:

>Hey there everybody on rec.tech
>
>I am currently messing around with a very old shimano positron rear
>derailler. Its a bit infuriating since I dont really have much info on this.
>I was wondering if anybody new of a website where there might be a diagram
>discusing adjustment of this type of derailler. Or any type of advice...
>woudl be appreciatted.
>Basically the derailler is somewhat bent, that I fixed..however problem is
>it just keeps shooting into the wheel. I am preplexed as to how one adjusts
>the limit on one of these or perhaps that is fixed?
>
>Thanks
>Polly

My memory could be wrong, but I think the single screw centers the
range. I guess in a way that's limiting, but I don't recall the
instructions saying to set it as a limit screw.

Try adjusting the screw while watching the effect on the derailleur's
movement. Even while not pedaling I think I remember the derailleur's
lateral position being affected.

A Muzi

Polly wrote:
> I am currently messing around with a very old shimano positron rear
> derailler. Its a bit infuriating since I dont really have much info on this.
> I was wondering if anybody new of a website where there might be a diagram
> discusing adjustment of this type of derailler. Or any type of advice...
> woudl be appreciatted.
> Basically the derailler is somewhat bent, that I fixed..however problem is
> it just keeps shooting into the wheel. I am preplexed as to how one adjusts
> the limit on one of these or perhaps that is fixed?

There is a single adjusting screw. It's accessed through an
aperture in the outer body plate.
Double check, by getting your head directly behind the
changer, that the thing is vertical and parallel to the
chainrings.
And oil the cable! They are pricey!

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971