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Looking for advice how to make counterweights for an ADC LMF tonearm

I can go steampunk, no probs :thumbsup:!
...I just found some thicker types of stainless steel washers with 15mm inner diameter and ordered a bunch to see if i can cobble something together from those :)
 
Something that just came to mind is a shaft collar with a setscrew. You might have problems finding one with low enough weight, but I'm sure you could make it work.

This one is aluminum weighs in at around 60g if I did the quick math right. Some creative work with a drill could probably bring it down to around 30g.

https://www.mcmaster.com/9946K17/

That one is 5/8" I.D., but you might be able to find a metric size closer to you. I'd be surprised if that stub is really 15.1mm nominal instead of 15mm. I don't see anything about the design that would have constrained ADC from using a nice round measurement. A 15mm ID collar would probably slide right on, but 0.1mm could be removed in short order from an aluminum part using a round file.
 
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Mchaz said:
Something that just came to mind is a shaft collar with a setscrew. You might have problems finding one with low enough weight, but I'm sure you could make it work.

This one is aluminum weighs in at around 60g if I did the quick math right. Some creative work with a drill could probably bring it down to around 30g.

https://www.mcmaster.com/9946K17/

That one is 5/8" I.D., but you might be able to find a metric size closer to you. I'd be surprised if that stub is really 15.1mm nominal instead of 15mm. I don't see anything about the design that would have constrained ADC from using a nice round measurement. A 15mm ID collar would probably slide right on, but 0.1mm could be removed in short order from an aluminum part using a round file.
Click to expand...
Looks like 15.1 mm OD stub, 15.4 mm ID CW with 0.3 mm proud o-ring dampers.

Wouldn’t be surprised to find the dimensions of stub and CW dimensioned around the o-ring dampers available. I have a set of English and Metric o-rings. There is a whole set of Metric o-rings exactly at the dimension that would fit that CW stub snuggly, but not tight.
 
I sourced a fully functional replacement from McMaster Carr. I carefully measured the shaft diameter and ordered a Shaft collar-just like the link offered by Mchaz. It's not original, of course, but it looks 'professional'. I just guessed at the weight-and I was successful.
 
Mchaz said:
Something that just came to mind is a shaft collar with a setscrew. You might have problems finding one with low enough weight, but I'm sure you could make it work.

This one is aluminum weighs in at around 60g if I did the quick math right. Some creative work with a drill could probably bring it down to around 30g.

https://www.mcmaster.com/9946K17/

That one is 5/8" I.D., but you might be able to find a metric size closer to you. I'd be surprised if that stub is really 15.1mm nominal instead of 15mm. I don't see anything about the design that would have constrained ADC from using a nice round measurement. A 15mm ID collar would probably slide right on, but 0.1mm could be removed in short order from an aluminum part using a round file.
Click to expand...

Great idea! After some translation mishaps I found the corresponding item in web shops here in Sweden. They are available with 15 or 16 inside diameter so should work with either some honing to slightly larger hole (on the 15mm) or maybe with a spacer like shrink tube (on the 16mm). Think I´ll try this!
stoppringar.jpg
 
Wolfie62 said:
Looks like 15.1 mm OD stub, 15.4 mm ID CW with 0.3 mm proud o-ring dampers.

Wouldn’t be surprised to find the dimensions of stub and CW dimensioned around the o-ring dampers available. I have a set of English and Metric o-rings. There is a whole set of Metric o-rings exactly at the dimension that would fit that CW stub snuggly, but not tight.
Click to expand...


You're right. The picture of the original counterweight on the previous page shows two o-ring grooves in the ID. I bet the original design used friction from the o-rings to hold the counterweight in place.
 
The absence of a spiral groove on the surface of the CW “stub” caused me to look closely at juan’s pics. The “balancing” CW is a damped, friction fit.

Using calipers, rulers, and an engineering compass, I produced many reverse-engineered drawings of manufacturers parts on production machinery so we could contract parts locally at 1/4 the OEM price. Or, make an improvement to a part or system. Some parts had a 3-6 month lead time; my only option was to reproduce parts locally for a down machine.
 
Just in the mail. This may work as a starter. Thinking about gluing the washers together with superglue and try to add something to damp against the armtube to prevent vibration /rattling.
IMG_20201125_062554.jpg

IMG_20201125_070614_1.jpg
 
Wow! Perfect fit! And, you can easily customize the weight.

How much clearance do you have? Enlarge the ID of the 2nd and 4th washers; install o-rings in the gap you make. It’ll work exactly like OEM!
 
Wolfie62 said:
Wow! Perfect fit! And, you can easily customize the weight.

How much clearance do you have? Enlarge the ID of the 2nd and 4th washers; install o-rings in the gap you make. It’ll work exactly like OEM!
Click to expand...
They're pretty much a snug fit now. Like the suggestion about mounting o-rings inside. Will try! ...if I f**k it up I have only wasted a couple of bucks :-)
 
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