Opus 3 Cantus parallel tracking arm

[bgruhn]

Originally Posted by dtut

Moray,

Thanks. The tinkering has finally reached the point that I can begin to seriously consider appearance and ideas are coming faster than I can implement them - a very nice quandary to be in - including steam bent wood for the wand/carriage connector. The track is glass lined. BillG leaves his naked, but I had to figure a way to connect the glass to an existing tower, which led to the wood substrate.

I think the cynical answer to the puzzle about the apparent lack of building is that LTs aren't very sexy. Bo's work is still the bench mark LT, but compare it to Frank Schroeder's magnetic bearing arm. The Schroeder is a great arm - I built a goofy clone - and sexy as hell. The namesake of this thread is an equally great arm, but just doesn't have the same visual impact. LTs tend to be small and cute - they just don't ooze audio pulchritude. You could substitute "Little Thing" for Linear Tracker. I've heard that reaction: "Gee, that Little Thing really does work. Look at it go. And it sounds pretty good." And off they walk.

And we've made a point of being able to build them from shop scrap, off-the-shelf hardware, and hobby bearings - not the best way to establish their cred, their audio cojones. And we've made it too simple. We're dealing with straight lines and 90 degree angles - none of that tenths of mm of overhang and offset to get good at, weird arcs, protractors, and distortion null points, none of stuff that makes LP music reproduction so much fun with a pivot arm.

It's a marketing problem. If we were trying to DIY replicate a seriously buffed existing tonearm made from gorgeously machined and finished exotic materials, costing thousands, and backed by major marketing and distribution, the response might be different. But we're coming at this from another perspective, we're trying to work our way toward something, actually developing a working design, then we can then start to make them pretty. I believe we are very close, especially with developments in the past few weeks. All the elements are available now for anybody to build a very good Linear Tracker and then start working on the visual polishing - adding the sparkle.

That's not to say there aren't technical advances to be discovered - I'm convinced there are, but I believe most of the major groundwork has been laid out. That said, I would love to have someone prove me wrong. There's still work to be done on particular bearing brands and sizes, specific cabling, although I'm reluctant to open that can of worms - actually, if we're reduced to cable arguments, that's a pretty good indicator we've achieved a mature innovation - and lots left to be done on resonances and cures. There's been no serious exploration of cartridges. There's all kinds of fun to be had yet on LTland.

This rant was originally going to be a skosh more tongue-in-cheek, ironic, but it got away from me. It's been a grey, cold, rainy day here - that sort of thing happens. Thanks for your indulgence.

[woodturner-fran]

bearing spacing is 33mm or ~1 3/8". Effective length is 80mm or ~3 1/8". I guessed those numbers from looking at the pics....

Am I in the ballpark?


Fran

[woodturner-fran]

mmm. So I went back and flushed out the bearings, spun them with the compressor. One of them kinda fell apart as it was spinning - one of the retaining clips just fell out. My issue may just be really crap bearings.


Fran

[bgruhn]

Hi Doug,
I have been having a lot of trouble trying to type answers to postings on DIY Audio. The cursor keeps moving around and shifting the positiion of words or partial words elsewhere on the page. I find my entries getting lost or deleted and other strange stuff. Thought it could be the wireless mouse sending spurious signals, so I tried a USB mouse to no avail. Right now I'm on word pad and having no trouble at all. Will copy and paste this to the forum if that works.
Your comments on the LT arm being ready for polishing up to something more than looking like a "little thing" hit home with what has been my thinking from the day one. In fact the "little thing" put me off building a LT for a long time. I'm about ready to build a more or less final model. My TT is made of grey Corian with a white Corian platter. I intend to use the same materials for the LT arm and scale the parts where possible to give an integrated appearance. The base will be like an arm board, curved to follow the platter and into a corner and side edge of the plinth. Wish me luck. In a reply to Fran I mentioned to you that I had just ordered ceramic bearings. I was able to get 4x10x4 mm bearings which are the same size as I am using in SS abec 7 bearings. So I will be able to make a direct comparison. I note that Acer-racer delivers these bearings lubricated with a low viscocity synthetic oil. Did you use yours as delivered or did you flush them out? I'm really looking forward to trying ceramics. When we feel that we have a matured and reproducible LT, maybe we should distill the process into a LT CookBook like the loudspeaker design cookbook, so future builders needn't dig through all our postings and efforts to reproduce one. But there is much fun and much to be learned by digging deeply into the forum and this thread. I tried to give Fran some help with his hunting problem. My hunting seems to be corrected, but I'm not really sure just what fixed it. Anything you can suggest or comment on would help him and possibly shed some light for all of us.
Rgds,
BillG

Originally Posted by dtut

Moray,

Thanks. The tinkering has finally reached the point that I can begin to seriously consider appearance and ideas are coming faster than I can implement them - a very nice quandary to be in - including steam bent wood for the wand/carriage connector. The track is glass lined. BillG leaves his naked, but I had to figure a way to connect the glass to an existing tower, which led to the wood substrate.

I think the cynical answer to the puzzle about the apparent lack of building is that LTs aren't very sexy. Bo's work is still the bench mark LT, but compare it to Frank Schroeder's magnetic bearing arm. The Schroeder is a great arm - I built a goofy clone - and sexy as hell. The namesake of this thread is an equally great arm, but just doesn't have the same visual impact. LTs tend to be small and cute - they just don't ooze audio pulchritude. You could substitute "Little Thing" for Linear Tracker. I've heard that reaction: "Gee, that Little Thing really does work. Look at it go. And it sounds pretty good." And off they walk.

And we've made a point of being able to build them from shop scrap, off-the-shelf hardware, and hobby bearings - not the best way to establish their cred, their audio cojones. And we've made it too simple. We're dealing with straight lines and 90 degree angles - none of that tenths of mm of overhang and offset to get good at, weird arcs, protractors, and distortion null points, none of stuff that makes LP music reproduction so much fun with a pivot arm.

It's a marketing problem. If we were trying to DIY replicate a seriously buffed existing tonearm made from gorgeously machined and finished exotic materials, costing thousands, and backed by major marketing and distribution, the response might be different. But we're coming at this from another perspective, we're trying to work our way toward something, actually developing a working design, then we can then start to make them pretty. I believe we are very close, especially with developments in the past few weeks. All the elements are available now for anybody to build a very good Linear Tracker and then start working on the visual polishing - adding the sparkle.

That's not to say there aren't technical advances to be discovered - I'm convinced there are, but I believe most of the major groundwork has been laid out. That said, I would love to have someone prove me wrong. There's still work to be done on particular bearing brands and sizes, specific cabling, although I'm reluctant to open that can of worms - actually, if we're reduced to cable arguments, that's a pretty good indicator we've achieved a mature innovation - and lots left to be done on resonances and cures. There's been no serious exploration of cartridges. There's all kinds of fun to be had yet on LTland.

This rant was originally going to be a skosh more tongue-in-cheek, ironic, but it got away from me. It's been a grey, cold, rainy day here - that sort of thing happens. Thanks for your indulgence.

[phivates]

I wonder if the cylindrical tube of the Opus 3 allows for a fudge of torque analogous to the "crabbing" of servo assisted LTs. 90 degree reactions are intrinsic to Newtonian structures, and attempts to achieve 100% rigidity are doomed. I'm thinking of the Millennium bridge in London which had to have dampers installed after the grand opening resulted in serious oscillation. The original is sometimes the best.

[bgruhn]

Fran, Couldn't tell whose pics you were looking at. DTUT's or mine. Mine measure 46.5mm spacing and 107mm apex of track to stylus. These numbers taken with hand held caliper held close to but not precisely against the arm. So yes you are in the ball park considering the pics are small and all taken at oblique angles. Sorry to hear your bearing blew up. Cut down the air pressure next time. Really, that spacer shouldn't have fallen apart. Get a refund or a replacement.

BillG

Originally Posted by woodturner-fran

bearing spacing is 33mm or ~1 3/8". Effective length is 80mm or ~3 1/8". I guessed those numbers from looking at the pics....

Am I in the ballpark?


Fran

[woodturner-fran]

Thanks guys. I ordered some new ceramic ones from acerracing.com, I'll try those when the land here.

In the meantime, I need to put the finishing touches to my schroder arm, which is up playing and sounding pretty good tonight!!


Fran

[bgruhn]

Hi Fran, Doug and others,
My 4x10x4 ceramics came today. Installed them tonight and spent the rest of the evening listening to records. Brilliant! First I flushed them out by spinning them slowly by hand in an acetone bath. then blew them out with compressed air and repeated the wash. There was a surprising amount of stuff that flushed out so the second rinse was in clean fluid. Acerracer says the bearings are lubed with thin silicone(check this) oil not grease so I didn't remove the seals. Then mounted them in place of the abec7's, aligned the arm again and the rest is listening to it. It tracks perfectly. The sound is no different than with the old bearings. It seems to be tracking at a lower stylus pressure, have to measure that. Like you Doug, I won't be going back to all steel bearings. I didn't want to buy a tube of 10, so I settled on 2 pcs. Perhaps cherry picking could have found even better ones. Will have to ask what the ABEC rating is. I think there may be a bit more radial play, and that may be to our advantage. Did a lot of watching the cart to check for hunting. There is none visible but I'll check more carefully. Now to make a pretty arm. I'm a happy guy tonight.
BillG

Originally Posted by woodturner-fran

Thanks guys. I ordered some new ceramic ones from acerracing.com, I'll try those when the land here.

In the meantime, I need to put the finishing touches to my schroder arm, which is up playing and sounding pretty good tonight!!


Fran

[woodturner-fran]

Excellent news!

Fran

[woodturner-fran]

New bearings arrived today - and yes they are a massive improvement! I flushed them out as normal and I did remove the seals - they ran much freer without those. I quickly mounted them up and tried them out..... and it works!!

Now, its not perfect yet, I think a bit more tweaking is needed, I need to polish the outside of the bearings, plus refine the mounting for the slide, plus I think I can shave a few grams off the mass too. I made a short vid and loaded it to youtube. Quality ain't brilliant, but you can get the idea. I shot some of the cart running in the lead out groove to show both the deflection on the stylus, and then again to show the carriage movement. The deck is just a junker with a warped platter, plus the record is not great either, so its a test!

Link:

VIDEO0095.3gp - YouTube


Fran