Restoring a Gray Research 103... input welcome!

garethj

Member
2016-03-14 9:06 pm
Hello everyone!

So, recently, I got my hands on a Rek-O-Kut B3 with a Gray Research 103 tonearm. I have access to a full machine shop, wood shop, electronics, 3-d printing, etc. Pretty much anything I could want.

I'm not sure I'm keen on doing any destructive modifications to the arm itself, so, beyond a rewire, cleaning and re-lube, what all could I do to help this arm out a little bit? Some things I'm considering:

-Replace bearing balls. ( the old ones are a little pitted. Would delrin be an improvement over the original steel balls?)
-Machine new bearing races out of brass or bronze.
-Rewire, re-lube.

I'm tempted to machine some of the mass out of the arm to get it lighter, however, I've never worked in magnesium before, which is intimidating, and also, It's in pretty damn good condition and I don't that any improvement I might get would be worth ruining a piece of history.

Any ideas or input would be hugely appreciated!
 

Bibio

Member
2009-03-08 3:36 am
replace bearings with delrin.. no use standard bearings they are harder.

machine new races from brass or bronze... no use proper races they are harder.

rewire.. yes

lube what.. the bearings? no! arm bearings should be run dry.

depending on the bearings you might find that you can buy them off the shelf.

dont machine the magnesium as you run a very high risk of warping. what i might suggest is slitting the headshel to allow a wider range of cars to be used.

after all of that i would really ask the question of why use such an antiquated tonearm?

if you have all that machinery at hand why not design and build your own arm.
 

garethj

Member
2016-03-14 9:06 pm
well, I am building an arm as well, I just really enjoy tinkering.

The thing I'm finding with the extant bearings, is that when I move the arm I can feel a tiny bit of rumble. I was thinking that replacing the bearing balls and using a graphite/moly lubricant would help.
 

Bibio

Member
2009-03-08 3:36 am
never ever use any type of grease, oil or lubricant on arm bearings unless its a single point design and only then for dampening purposes. grease dries out and clumps, graphite molly is actually fairly rough due to the graphite particles.

if you can feel rumble on the bearings then the balls and races are shot, you will be able to get new ones off the shelf. you just need the size of the outer shell, width and type. dont be tempted to get high spec ones as they tend to bind in high temperatures if not set properly.

nowt wrong with tinkering :)
 

garethj

Member
2016-03-14 9:06 pm
I think the races themselves are fine. I did clean and polish them. I the BB's have some noticeable... pitting? under sight magnification.

When I move the arm with my fingers I can feel very, very slight rumble in the movement.

The thing with the races is that they aren't standard radial ball bearings. I'll post some pictures when I go to the shop, but I'll try to explain here. It's sort of a hybrid radial/axial thrust bearing. The outer race is 90 degrees in cross section, in which sit 9 loose BB's. The inner race is a tapered shaft that presses the balls into the 90 degree wall of the outer track. I can't replace the bearings without making my own. The balls themselves are simple .125'' steel. Those I can very easily replace with off the shelf parts. My reasoning behind the delrin was that it might reduce noise, even though its obviously not as hard, from what I remember it does have very low breakaway friction, and being that its softer it might provide some compromise for any deviation from spec that the races themselves may have accumulated over the 70ish years the arm has been floating around.
 

Bibio

Member
2009-03-08 3:36 am
so a fancy needle point set up which is inverted so the cone is on the inside acting as the axle. you know i never even gave that setup a thought, interesting as you could turn the outer cup into the adjustment... hmmmm. much like old car hub bearings.

i would stick the races and axle in the lathe and take a skim off the faces or just stick them in a cordless hand drill and use a bit of leather and very fine cutting/polishing compound then thoroughly clean after with nail polish remover. if there is any pitting in the races what so ever then the bearings will stick.
 

garethj

Member
2016-03-14 9:06 pm
I'll hit up the shop tomorrow and snap a few pictures. Kevin, the reason I don't want to do any destructive mods is exactly that; the arm is worth something to someone. I would, though, like to squeeze every bit of performance I can out of it, while still being able to return it to factory spec should anyone come along who wants it more than I do :)
 
Sounds like a good plan, ultimately of course if you are putting it to good use that's even better.

I've tried to nothing absolutely irreversible to either of my TD-124s, although I have to admit the second one came to me completely in pieces and largely incomplete, so I'm not exactly sure where I am going with that.. lol I've done a sensitive restoration..