Hi Carlo, I was thinking about using spring to hold the tips instead of adjusting the set screws, punching on side walls is probably easier to be accurate.Thanks for the praising/teasing, friends - Carlo is just an old mule who tries everything possible to waste time.
2A3 - Sorry to disappoint you, unfortunately this is one of the most difficult arms I have built, and i'm still modifying it. Keeping the parallelism is anything but trivial: no play at all, and pivots positioned to the hundredths.
How will you use the spring? On CS, as previously on Lil Casey and others there is an elastomer, a small piece of O ring in the center of the groove for the two pentips
Reckon that you might be correct there Carlo, something springy that doesn't ring rather than a metal spring that rings happily? - an effect we seek to eliminate.Great, when finding a 2mm spring with the right force.
A piece of 2mm diam. O ring chord in the same position is fine for me: gives the right pressure on pentips, prevents their rotation and seals the ink (or grease) inside. 3 jobs for a single small piece of plastic (it can hardly be seen in the photo of parts ).
I could also say that it has a fundamental importance against chattering, but...
Carlo, now we just need to see some excellent photos of the whole, very neat and excellent realisation please!CORKSCREW MK2 MEASURES -(#4560)
sorry for the delay - but there was a good reason, beyond my laziness
my "crash test", although encouraging, showed a somewhat "hesitant" behavior: the carriage on eccentricities flowed easily, which is not unusual with non-recirculating bearing, but the movement was not as smooth as I like it. Mike56, who had some initial problems with CG placement, gave me helpful hints and I began to notice several other details to improve. In short, I built a second carriage: the improvements are small, almost not measurable, but the cantilever moves better, and this is important.
(drawings - attachment)
VTF VARIATIONS (digital scale setup - attachment)
The first A cart, reassembled, and the second B cart show not much difference; indeed the former perhaps moves better, due a single CW (instead of two different ones), longer base ("headshell") and more building precision
A cart - H / VTF
0 / 1.58 - 0.5 / 1.56 - 1 / 1.55 - 1.5 / 1.58 - 2 / 1.60 - 2.5 1.62 - 3 / 1.75 - 3.5 / 1.73 - 4 / 1 , 72
B cart - H / VTF
0 / 2.22 - 0.5 / 2.19 - 1 / 2.22 - 1.5 / 2.23 - 2 2.25 - 2.5 / 2.18 - 3 / 2.20 - 3.5 2.08 - 4 / 2 ,10
The digital scale measurements confirm the first rough tests done: very small changes in VTF due height (only 0,15 gr ca on severe warps >3mm) and a quite good repeatabilty (however worse than a good pivoted)
FRICTION - STICTION (sine bar set up - attachment)
A cart Total weight = 48 gr
friction - runs with a tilt of a 0,35 height / 300mm rail. angle = 0°2'17" = 0,038 decimal --- μ =0.00066
stiction - starts with a tilt of a 0,75 height / 300mm rail. angle = 0°5'10" = 0,086 decimal --- μ =0.0015)
B cart Total weight = 46 gr
friction - runs with a tilt of a 0,40 height / 300mm rail. angle = 0°2'17" = 0,038 decimal --- μ =0.00066
stiction - starts with a tilt of a 0,65 height / 300mm rail. angle = 0°5'10" = 0,086 decimal --- μ =0.0015)
A bit worse than the CorkScrew cart ones - and I was so proud to have reached 0.1 and 0.04 of parallelism! - Evidently some more play with a self centering rail doesn't hurt. and less weight too! (39 vs 48 gr)
The two carts have practically the same (average) measures, but not the same behavior - rolls unevenly the first A cart, really smoothly the second one, the B cart - an acceptably centered CG seems really to count a lot.
INVERSE PENDULUM (inverse pendulum set up - attachment)
as known, the pendulum measures are only stiction measures, and even less reliable than those with the sinebar (more measures for an acceptable average) However, their observation is very useful to better understand their behavior on a leveled rail.
(only for the cart B - the measurements of cart A do not give measurable average differences)
B cart Horizontal movement
Total weight = 46 gr
displacement S = 0,0028 m
Θ (angle = 4,59°
H (mg height) = 0,00112
U (pot. energy) = 5,048-5
F (friction) = 0,0018 N
B cart Vertical movement
Total weight = 46 gr
displacement S = 0,0032 m (42- ca 10mm)
Θ (angle = 5,24°
H (mg height) = 0,0015
U (pot. energy) = 6,596-5
F (friction) = 0,0020 N
CRASH TEST (3+3 MP4 video zipped - attachments)
And now, for your amusement. the usual "crash test videos". (Eccentricity = 1,5 mm - Warp = 3mm - far beyond RIIA spec.)
In the B cart there is a visible improvement compared to A, especially in the horizontal movement.
Seem not so bad to me, and the tracking of average LPs with normal defects is also smooth and satisfactory.
ciao a tutti - carlo
For me its very simple audiostar, this is a diy forum and i make my diy versions without machine tools, no chance i can make a servo arm and with lots of help from folk on the forum i have been able to make a passive arm that meets lots of folks aspirations, if anyone can make one like Carlo's and compare it!, that would be fantastic!Linear servo tonearm vs linear non servo tonearm. What are the advantages or disadvantages?
For me it is not that simple. Mike is right , servos have a tendency to be more complicated because of the needed motor drive, but not necessary bigger demands to your mechanical workshops machinery.Linear servo tonearm vs linear non servo tonearm. What are the advantages or disadvantages?