In another post I enquired about the purchase of a tonearm but there were no offers. I therefore had to make do with what I had which involved modifying and machining parts to build an arm from scrap bits which I had.
All of this work was done between Christmas and New Year and at long last I could start testing the homebrew which was by far the most work I ever did building a tonearm.
The work involved making many parts and in particular two new open bearing cups, machining two cones and for these two bearings, I used brandnew roller balls - 12 balls each at the top and bottom bearings. All parts were mirror-polished before fitting them together.
And so started the most frustrating 2 weeks. The arm would work perfectly OK for a couple of record sides and then start misbehaving by refusing to track beyond random points on different records although the geometry and overhang was fine.
When assembling the bearings, I put a very small quantity of Superlube with teflon in each bearing cup but later learned (from Lencoheaven) that tonearm bearings should run dry, sans lubricant.
So I rinsed out all lubricant and initially, the arm worked correctly for quite a bit longer but eventually the problem of binding returned.
When I assembled the arm, the nut adjusting and locking the pressure between the rollerballs and the two cones was locked/fixed with locktite but this I found was not working as I noticed minute, telltale score marks around the circumference of both cones.
What had happened was that the locktite I used for the nut obviously didn't work and as the arm traversed, the nut somehow went tighter, pressing the roller balls tighter than adjusted and scoring the two cones and causing (undetectable) stiction if the armwand was moved by hand.
I then re-polished all the bearing contact surfaces and tried locking the nut again, using a dab of Pratley Steel epoxy and then again Araldite, all to no avail - the nut moved and the arm's misbehaviour started all over again.
This type of open armbearings and cones obviously wasn't going to work so yesterday I stripped the arm and found two new enclosed bearings from one of my Ambassadeur fishing reels.
Yesterday, I had to re-configure my lathe to turn between centres a hollow, flanged spindle with different-sized threads at each end to accomodate the two new bearings.
What a way to spend the holidays...
skollie
All of this work was done between Christmas and New Year and at long last I could start testing the homebrew which was by far the most work I ever did building a tonearm.
The work involved making many parts and in particular two new open bearing cups, machining two cones and for these two bearings, I used brandnew roller balls - 12 balls each at the top and bottom bearings. All parts were mirror-polished before fitting them together.
And so started the most frustrating 2 weeks. The arm would work perfectly OK for a couple of record sides and then start misbehaving by refusing to track beyond random points on different records although the geometry and overhang was fine.
When assembling the bearings, I put a very small quantity of Superlube with teflon in each bearing cup but later learned (from Lencoheaven) that tonearm bearings should run dry, sans lubricant.
So I rinsed out all lubricant and initially, the arm worked correctly for quite a bit longer but eventually the problem of binding returned.
When I assembled the arm, the nut adjusting and locking the pressure between the rollerballs and the two cones was locked/fixed with locktite but this I found was not working as I noticed minute, telltale score marks around the circumference of both cones.
What had happened was that the locktite I used for the nut obviously didn't work and as the arm traversed, the nut somehow went tighter, pressing the roller balls tighter than adjusted and scoring the two cones and causing (undetectable) stiction if the armwand was moved by hand.
I then re-polished all the bearing contact surfaces and tried locking the nut again, using a dab of Pratley Steel epoxy and then again Araldite, all to no avail - the nut moved and the arm's misbehaviour started all over again.
This type of open armbearings and cones obviously wasn't going to work so yesterday I stripped the arm and found two new enclosed bearings from one of my Ambassadeur fishing reels.
Yesterday, I had to re-configure my lathe to turn between centres a hollow, flanged spindle with different-sized threads at each end to accomodate the two new bearings.
What a way to spend the holidays...
skollie
