Film-Tech Forum ARCHIVE: Benefits of LaVezzi VKF sprockets?

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Posted by Brad Allen (Member # 470) on 08-21-2003, 03:52 PM:

Would someone be so kind as to enlighten me?
Are they usually available for most Proj/sound heads?
Thanks

Posted by John Pytlak (Member # 331) on 08-21-2003, 04:04 PM:

Wider sprocket tooth profile "spreads out" any perf stress over a wider area, and the rounded corners reduce stresses in the perforation corners:

http://www.lavezzi.com/LavFAQ-VKFII.html

http://www.lavezzi.com/VKF.html

Originally, the VKF sprockets were designed to be compatible with both KS-1870 perforations and the smaller CS-1870 (CinemaScope used with mag striped film) perforations, but have been redesigned for use with KS-1870 only, since CS-1870 perfs have not been used since the early 1980's.

Posted by Will Kutler (Member # 770) on 08-21-2003, 04:07 PM:

As quoted form the LaVezzi catalog

"Whether driving film, perforated lead frames or in TAB applications, protecting perforations against premature failure is often critical. Thus the form and finish of the VKF (Very Kind To Film) sprocket has been designed to reduce damage to the perforation.

The VKF tooth has a maximun width across the flat driving face to minimize the stress on the perforation face. the corners of the teeth have been radiused to clear the perforation radii. This eliminates the potential for damage when lateral motion causes the perforations to slide over a relatively square standard tooth corner."

"The finish of the VKF tooth form has been enhanced using the Radii-Blend TM process. With this procedure, every intersecting tooth edge, both at the sides and the top, is blended and burnished to offer a polished surface. This insures a smooth engagement and disengagement of the perforated edge with the tooth surface."

"Although the stock VKF design was origonally intended for materials perforated per ANSI-SMPTE 102-1991 or 139-1986, the process may be applied to other tooth forms. Super 16 and 35 , as well as 70mm tooth shapes, have been improved using this procedure. Contact LaVezzi for information on variations of other similar applications."

On a side note, I do believe that LaVezzi VKF sprockets are less prone to "hooking". Today, VKF sprockets are almost standard equipment. I do believe that VKF sprockets can be adapted to older projector intermittents such as the Simplex Super and E-7, but applications should be checked with LaVezzi, as they do have the application information/charts.

Posted by Paul G. Thompson (Member # 655) on 08-21-2003, 07:48 PM:

LaVezzi VKF Sprockets are the greatest thing since sliced bread. [Smile]

Posted by Dick Prather (Member # 1136) on 08-21-2003, 08:17 PM:

VKF sprockets are available for most of the common American projectors and soundheads. They do not make a VKF for old style taper pin intermittent sprockets just the updated nut and bolt versions. I use them for all replacements on rebuilds. For normal use they are the best sprocket out there. They also have a newer VKF II sprocket. Check with the LaVezzi web site for info.

One problem is that they will NOT run shrunken C/S or Fox perfs. They can damage your shrunken mag film. Since I do run older mag film I took my VKF sprockets out and replaced them all with new C/S ones.

Posted by Steve Kraus (Member # 476) on 08-21-2003, 09:28 PM:

Super 16 and 35 , as well as 70mm tooth shapes, have been improved using this procedure.

Sprockets specifically for Super 16 or Super 35? Huh?

Posted by Gordon McLeod (Member # 33) on 08-21-2003, 11:13 PM:

Steve it says Super16 and 35, not super 16 and super35

Posted by Mark Gulbrandsen (Member # 72) on 08-22-2003, 10:28 AM:

We recently custom fitted a set of VKF 24 tooth sprockets to a DP-70 for testing. Seems to be runnng really good. This will eliminate the need for expensive 35/70 alumnium sprockets that have short life span. I have yet to see a re-designed 70mm sprocket that has incorporated VKF or Positrol teeth. Something that should be done though.......
Mark

Posted by Frank Angel (Member # 248) on 08-23-2003, 02:14 AM:

So does LaVezzi make CS sprockets that are comperable to the VKF configuration? Dick said: Since I do run older mag film I took my VKF sprockets out and replaced them all with new C/S ones. Are these better than what for a better term would be "normal" CS sprockets? Or just new?

Didn't I read somewhere that CS sprockets BETTER for film (contrary to what your gut would tell you)? I seem to recall they did wear tests on CS -- foxholes -- prints and regular print film and the CS prints held up better. It stuck in my mind because it is just the opposite of what you would think would be the case.

Frank

Posted by Mark Gulbrandsen (Member # 72) on 08-24-2003, 09:39 AM:

Frank,
You are on the right track but just have it backwards. CS, or Fox holes are actually much stronger than regular KS perfs. However you'd find that use of CS tooth sprockets on KS perf film is not as gentle to the film as a VKF tooth sprocket would be. VKF teeth also generate less film dust due to the wide face and rounded corner teeth. As for Dick removing his VKF's to run CS perf film it is definately not necessary to do this unless the Mag striped film were shrunken laterally. I've run many 35mm mag prints with VKF tooth sprockets without any problems......the VKF teeth were designed to be compatable. On the other hand even all 15/70 projectors I've seen and or run are still using tiny cs style teeth. I'm surprised that none of the LF machines have incorporated that tooth design.....LaVezzi actually makes the Imax projector input and output sprockets anyway.
Another point to note...... Don't get Posi-Trol and VKF teeth mixed up. Posi-Trol teeth ARE NOT compatable with CS perfs!!
Mark

Posted by Chris Hipp (Member # 1788) on 08-24-2003, 10:48 PM:

Mark:
I remember in a recent post you had DFP 2000 sprockets that are hardcoated. Could you either email me the information on those or give me the phone number. I cant find that last post with the info.

Posted by Dick Prather (Member # 1136) on 08-25-2003, 12:40 AM:

Mark is correct. VKF sprockets were designed to run fox hole film and they are a better sprocket. Unfortunatly I do have shrunken mag that would not regester properly on my XL 24 tooth sprokets. To not damage the film I put new C/S sprockets in place of them.

Frank, The C/S sprockets were just new in the box from stock I had on my shelves. I don't think LaVezzi ever made a C/S VKF sprocket or at least I never saw one. All my films run just fine on the smaller teeth for being quiet and picture quality.

Posted by Mark Gulbrandsen (Member # 72) on 08-25-2003, 09:42 PM:

Chris,
We do have a supply of the Sony sprockets on hand. They are hardcoated to a metal depth of .001, and with a .001 thickness on top of that. This will increase the life of them drastically although I can't predict exactly how much. We have a couple out in the field and have had no problems with them. Give us a call if you need one. They are far less expensive than getting them form Sony and exactly the same sprocket!
BTW: These sprockets have the old standard tooth design which is better for wear than a CS tooth alumnium sprocket is.

Mark @ CLACO
801-355-1250

Posted by Steve Guttag (Member # 268) on 08-25-2003, 10:44 PM:

When we switched to the Hardcoat version of the sprocket, the buzzzzzzzing noise assocaited with the sprocket also vanished too!

However, DON'T try to run any CS perfs though that sprocket... the teeth are not centered on the CS perf but on the inside edge of the KS perf (the CS film will buckle) Somwhere I have the drawing on that sprocket...I'll see if I can dig it up.

Steve