Carbon fiber brace experiment

[ebreckpo]

For the info the P5 I own is the one with the wooden surround.

[watercourse]

Really loving the sound, playing Brahms Symphony No. 4 Sawallisch/Vienna SO!

[troutbum]

Good stuff! Nicely done.
Being a bicyclist myself I do like the comparisons, even do I only ride Reynolds 520 Steel

I was wondering though since the sheet of CF is quite thin, how is the stiffness?
Does it bend easily?
From what I've read the braces are supposed to keep the arm base and platter base at the same distance at all times (something like that?), or am I on the wrong track?.

Allthough I'm sure you've already thought about that

[brassnwood]

A really good project Wilson
If I understand correctly then, your single brace is 'Clamped' in place by both the VTAF & the brass bearing?
I always thought that the Brace was for 'stiffening' the plinth without 'Linking' the arm /bearing.
Perhaps someone with the RP3 or 6 could let us know how their brace's are fixed
I thought Most TT's nowadays try to isolate the 3 main components - I am hear to be shot down of course
I wonder if the clamping is causing the Hash; just a thought from this Non musical man unlike most of you guys
Cheers,
GC

[RoDa]

It's is clamped in place.
Looks like it's supposed to link the bearing and the armbase.



REGArds

[Etnier]

Really loving the sound, playing Brahms Symphony No. 4 Sawallisch/Vienna SO!

Of course. I could tell from the rills.

Seriously, though- is that green dot at the pivot point to aid protractor work?

[Etnier]

TWO braces, top and bottom and kept in tension, MIGHT stiffen a plinth. Otherwise, the only effect would be coupling the arm and bearing. Right?

[watercourse]

Good stuff! Nicely done.
Being a bicyclist myself I do like the comparisons, even do I only ride Reynolds 520 Steel

I was wondering though since the sheet of CF is quite thin, how is the stiffness?
Does it bend easily?
From what I've read the braces are supposed to keep the arm base and platter base at the same distance at all times (something like that?), or am I on the wrong track?.

Allthough I'm sure you've already thought about that

Thanks Troutbum and Etnier!

@ Troutbum: My wife rides the Reynolds 853, while I ride a Dedacciai SAT frame. She always gets the good stuff. Although I preferred a bit more the geometry of my previous Easton Ultralight Alu frame, it was a harsher ride and it was stolen.

CF becomes very difficult to flex at 1/16" or about 1.6mm. I could not bend it perceptibly.

As RoDa says, I think the brace is at least stated to do more than just act as a spacer, it is supposed to provide a rigid mechanical link between bearing and arm. That was one of the ideas I was "testing". The theory is that the forces of rotating the subplatter and platter may lead to arm and platter motion that is not on the same plane or vector, which becomes audible with blurring and timing problems. This is not my theory, I repeat it from reading elsewhere.

If this were true, my hypothesis was that one would expect to hear more cohesiveness and increased resolution with a more rigid material than the somewhat softer mdf plinth covered with phenolic resin. Another hypothesis was that CF is very good at absorbing energy, and therefore would reflect back less energy coming from the arm, and transmit less energy from the plinth. This would likely lead to less blurring effects and more even frequency response.

I still haven't put any other carts on, so I guess I can't say I've proved the hypotheses completely. Because both the SAE and 501 gained resolution, I might say they been partially proved. I'm not sure what to say about cohesiveness, because this is difficult to quantify when the deck was not lacking focus before, AFAIK. I can say that those records with previously boomy or woolly bass are no longer like that. Bass is tight and textured, which may help with a perception of greater extension, because you can actually hear the notes better than before.

And if I don't feel like taking the Shelter away, I guess this is a good result in and of itself? Who knows, but at some point, I will try another cart and report back.

@Etnier: I think what you state about double braces needed to stiffen the plinth is true, based on Rega's description of the DBT as a "stressed beam". Frankly though, I'm not sure (and may be a bit skeptical) how Rega have fabricated the plastic to be a true stressed beam, i.e. flexed prior to clamping, and they don't talk much about the DBT's sonic benefits, only mechanical benefits.

So, in my experiment, even if I had used two braces, it would not be similar to Rega's DBT if in fact they do use a stressed beam approach, as I could not duplicate that in DIY. My "armboard" experiment may only mechanically couple the arm and bearing, and might drain energy better.

[brassnwood]

Thanks for the pic Rolf - it shows the set-up very clearly - oh well, what do I know
GC

[watercourse]

A really good project Wilson
If I understand correctly then, your single brace is 'Clamped' in place by both the VTAF & the brass bearing?
I always thought that the Brace was for 'stiffening' the plinth without 'Linking' the arm /bearing.
Perhaps someone with the RP3 or 6 could let us know how their brace's are fixed
I thought Most TT's nowadays try to isolate the 3 main components - I am hear to be shot down of course
I wonder if the clamping is causing the Hash; just a thought from this Non musical man unlike most of you guys
Cheers,
GC

Thanks GC! Long time no hear!
Yes, the brace is clamped by the VTAF and bearing. I'm not sure that stiffening the plinth is all that the DBT is intended to do, at least from Rega's descriptions, but I am open to other thoughts.
Etnier also brought up the "stressed beam" concept - I also wonder how the brace is attached. Just by clamping, or something else in addition? If you look at online photos of the RP3/6 from below, the arm's connection to the bottom brace appears less rigid than I would have imagined, although in the three other connection points, the braces appear "clamped".
Also, I felt that the hash was actually diminished with the brace in place, but I may have to confirm this again at some point when I'm feeling less lazy.
Lastly, I'm not shooting you down, but I think there are so many TT designs out there that I feel it's hard to make any blanket statements anymore.

[watercourse]

Whoops sorry Etnier, the dot of blutack helps me when I am aligning carts, making sure pivot-to-spindle hasn't changed. I don't know why I've kept it there, P-S hasn't changed in the past 6 months. Lazy...

[troutbum]

Off course, there is also the theory that the only thing the braces does is allow for faster assembly at the factory.

[watercourse]

We'll need another experiment using other materials as a brace

[troutbum]

We'll need another experiment using other materials as a brace

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