EPA-100 Project

[muovimies]

I'm under the impression that all impressive equipment aside, putting together a tonearm is still mostly a human being using his hands to get the feel just right and then making sure it moves as freely as a good example of that design should. I might be wrong though. And of course, even if it is, it still takes a good bit of experience. I mean if you have fairly sensitive hands, it's not difficult to feel even the tiniest bit of play, or tiniest bit of excess friction, but without a reliable baseline it's impossible to know what exactly you are aiming for. The best you can do is go back and forth until you believe you've found the spot.

 

[jamie123]

The best you can do is go back and forth until you believe you've found the spot.

oh god ive been there! lol

 

[JP]

No way you'll feel excess friction or play, unless it's rather drastic. The last bit of bearing play I can hear but not feel, and to check movement I blow on it and watch it move to see if there are any tight spots. Just finished mounting the gimbal, which took nearly two hours to get adjusted right.

 

[totem]

You may just have a career as a hand model, i hear they pay quite well.

 

[muovimies]

No way you'll feel excess friction or play, unless it's rather drastic. The last bit of bearing play I can hear but not feel, and to check movement I blow on it and watch it move to see if there are any tight spots. Just finished mounting the gimbal, which took nearly two hours to get adjusted right.

When you say hearing bearing play you can't feel, surely you must be using a stethoscope or something? At least for me, there's no way I would be able to detect bearing play I can't feel with my hands with any other sense, though I haven't tried licking the bearings to see what they taste like... I realize the tolerances are mighty fine, but I honestly feel at least for me hands get me really close. For horizontal movement the final test I do using a piece of paper to see how long and thin piece of copy paper can still move the arm with freely, if there's tight spots they will show up... + you can feel them in the paper To be fair any of the arms I have adjusted haven't had bearings of the quality of something like EPA-100. Maybe I just have talented hands for this or maybe my "perfectly adjusted" arm is the rough starting point at which for you real adjustment starts. I'll say this though, I've seen someone feel for very minor hairline fractures in the bones through skin and everything, the doctors missed them on the X-rays until they were told what to look for, and I'm not sure they ever came to believe someone actually found them feeling for them with their hands.

 

[JP]

May not work for all arms and pieces, but the gimbal on the EPA-100 magnifies sound fairly well - I just hold it up to my ear. Likely that'll change once the yoke is in place. The paper trick sounds like a good one - I'll try that.

 

[JP]

Worth mentioning I'm adjusting the gimbal without yoke and arm tube - I prefer to do it without as I can get better adjustment without the weight/lever of the tube.

 

[Ken Boyd]

Packed many a cageless needle bearings on outboards and watercraft engines and they are no fun but at least they are not near as small as those. If they don't have a cage don't pack them to tight, you have to leave a little room for them other wise they will bind.

They are not taper bearings how do you measure the end thrust clearance? Do you just tighten down on the shaft that the bearings run on until they bottom out, and then back them off just a bit?

 

[jamie123]

here's what i do for a reference,i cut small triangles of masking tape and put one on the bearing cup and one on the body of the tonearm,using some magnifying framed glasses i can see both points of each triangle, i slowly take out the bearing play with tiny adjustments,when 1 tip of the masking tape goes past the other i simply peel off one of the triangles and stick it back in line so each time my window of pre load gets smaller until im right on the sweet spot (hopefully!)
check the arm movement as you go.

 

[JP]

@jamie123 can you explain that with a bit more detail - I’m having a hard time following.

 

[jamie123]

@jamie123 can you explain that with a bit more detail - I’m having a hard time following.

ive edited it so it makes more sense

even using the above method its a pain in the arse,the bearing cups are locked in place with grub screws,tightening these puts a bit of pre load on the bearing as does the cup covers,so both have to be factored in.
id love to know how they did it quickly when first built!

 

[Ken Boyd]

I think they load the bearings in prior to rolling that edge on that outer bearing shield.

 

[JP]

@jamie123 what arm in your pic?

 

[jamie123]

It’s a zeta

 

[JP]

Ah. I found a thread on VE that showed one in pieces - makes more sense now. Bearings on that one are massive in comparison. I should've gotten one of those!

 

[jamie123]

i hope your arm building is going better than mine?
i stripped mine down again as i wasn't happy with the free play,as hard as i tried i could not find that sweet spot between too loose and too tight,on closer inspection i found small indentations on the bearing cones from being over tightened in the past,bummer!

 

[theophile]

You may just have a career as a hand model, i hear they pay quite well.

 

[JP]

Can the cone be resurfaced?

I'm stalled here. One of the plastic covers on the yoke broke apart when I removed it so I need to fabricate replacements. I've been looking at materials, etc. but it'll likely be a few weeks until I get something workable.

Not helping, our town where our weekend house is was hit with a macroburst Tuesday. 110 MPH winds. No idea when we'll get power back, no packages being delivered, etc. We're heading up this morning to scope out the damage.

 

[jamie123]

im hoping so,they are currently with the guys at true point uk so fingers crossed.

 

[theophile]

Wishing you well JP.