Film-Tech Forum ARCHIVE: Rebuilding Christie Ultramittents

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Posted by Jeremy Weigel (Member # 4208) on 03-19-2008, 07:10 PM:

Other than sending these back to Christie for repair/exchange, is there anyone who rebuilds these at a more reasonable price?

Posted by Tristan Lane (Member # 1169) on 03-20-2008, 01:01 AM:

American Cinema Equipment in Portland, OR will rebuild these for much less than Christie. Many of the big chains use them for rebuilds.

Highly recommended. I've sent a lot of intermittent movements to their shop and have had great performance.

Posted by Jeremy Weigel (Member # 4208) on 03-20-2008, 07:00 PM:

Thanks Tristan. I'll give them a call.

Posted by Randy Bowden (Member # 587) on 03-21-2008, 08:57 PM:

Gee, thanks Tristan [Smile]

Posted by Mark Gulbrandsen (Member # 72) on 03-25-2008, 10:14 PM:

As a side note I did an Ultramittent overhaul today with one of the new LaVezzi Ultramittent Kits instead of fitting, lapping the bushings and sorting ball bearings myself as I normally do. I have to say that LaVezzi has finally hit the high mark in rebuild kits. If you laid all these parts out in a big windstorm they'd literally blow themselves right back together. All the parts are literally a perfect fit and its just a 30 to 45 min rebuild job not counting the run in time.

Mark

Posted by Randy Bowden (Member # 587) on 03-28-2008, 04:56 PM:

I wish I could say the same thing about the quality of Lavezzi cam shafts that I've been getting. There seems to be a real lack of consistency with the cam pin, the more common problem being that some are slightly over sized and pull through with too much resistance, so I have to fix that little problem to get them working properly. The other not so common problem being that sometimes you get a pin that is not pressed in strait and will hardly pull through at all. Having said all that, I almost always have good things to say about Lavezzi quality. Although I have yet to try out the Lavezzi rebuild kit for the ultra, I really do like the Century kits a lot.

Posted by Mark Gulbrandsen (Member # 72) on 03-28-2008, 10:58 PM:

Randy,

When we were rebuilding Ultramittents for Christie a number of years back (I believve you guys were too) the parts batches we received from LaVezzi were not tolerance matched at all and gettingthings matched and then ramped up to rebuld them was not an easy task ... I think you'll find the kit parts are much better matched, however if there is a tight pin its not all that big a deal to lap out the slots in the star a little.

Mark

Posted by Louis Bornwasser (Member # 3063) on 03-29-2008, 04:45 AM:

In fact, it is far better that they be a bit tight, rather than loose. This is the process lapped by you and then "run in" during the in inital assembly. Of course a thorough cleaning after run in is essential to remove the particles shaved off during run in. Wed use a heavy duty industrial ultrasonic cleaner for this.

As regards LaVezzi matching....maybe, but we take 25 or 30 newly purchased cams & stars and "rematch" them. We once didn't and had left over parts that were unusuable. Let's just say that we are better at matching than they are! Louis

Posted by Randy Bowden (Member # 587) on 03-31-2008, 05:29 PM:

Mark,

I have never actually lapped out the star wheel, just being honest here, but I don't really know how to do it properly. What I have been doing is using some 1200 grit sand paper on the cam pin. It usually does not take much to get it into spec. just enough so the pin will pull through smoothly. I do this with the simplex cams and usually it results in an intermittent that runs so quiet you can hardly tell it's on.

Of course there are the ones that pull through perfectly right out of the box, thus making my job much easier.

Sadly, if and when this DCIP thing goes through, I suspect I will see a tremendous drop off in rebuild work. Who knows how many years I have left in this. I currently get about 95% of my business from Regal, AMC and Cinemark, so I'm not looking forward to the day when my rebuild work goes away, as I actually do like fixing these things.

Posted by Mark Gulbrandsen (Member # 72) on 03-31-2008, 07:40 PM:

I've had to lap out Century C stars a number of times. I use a piece of glass and lapping compound and count strokes making sure that each side of the slots get the same number of strokes... works really well but don't loose count! Thats a really good idea about the 1200 grit Randy... the fine lines that the 1200 grit will put into the pin are actually very good oil carriers and the cam pin will last alot longer than if it were just smooth. I always thought that a cam pin with tiny little grooves around the diameter would also be good oil carriers and make the pin last longer. The Brenkert roller pin was alo a very good long lasting design. I don't recall anyone else ever doing a roller pin but there may be others....

Mark

Posted by Randy Bowden (Member # 587) on 03-31-2008, 08:30 PM:

Ya know I've never actually had a Brenkert Int. apart. that's interesting and I wonder if it's anything like the pizza-meccanica intermittents. The V-5 has a cam roller that's basicly a sleeve that fits over an eccentric pin. When you get a new star it comes with the cam pin roller assy and the pin will definitely drag through the star, but it's also supposed to do that. I can run the intermittent in at about half of film speed, by the time I come back in the morning, the cam has seated itself to the star quite nicely. Pretty cool actually.

Posted by Mark Gulbrandsen (Member # 72) on 04-01-2008, 07:52 AM:

Yea, The Brenkert is modeled after some of the European stuff. Shakamecanicca and Prevost mainly.

Mark

Posted by Gordon McLeod (Member # 33) on 04-01-2008, 10:04 AM:

Brenkert was patterned after a early Ernamann

Posted by Dick Prather (Member # 1136) on 04-01-2008, 02:35 PM:

Power's 6B intermittents used roller pins in the 1920's. The 6A did not. Probably other European and Japanese machines did also. I agree with Gordon about the Brenkert intermittent.

Had a couple apart to check for wear and never found any. Long lasting movement.

Randy, I havent had to lap a star for a while. We used to get oversize cam pins and lap stars to fit on some rebuilds. Quality from LaVezzi is usually pretty good. There were lapping blocks made for this. Never found one for sale.
Dick

Posted by Mark Gulbrandsen (Member # 72) on 04-01-2008, 05:40 PM:

The other interesting thing about Brenkert movements is that neither the star nor the cam are hardened steel. Prooves that when you do it right it lasts long no matter how well hardened the metal is. Ballantyne s steeltars and cams are also not hardened... they also see many tips break off of the stars...

Dick... LApping blocks in many sizes can be bought at many machinery supply places. A piece of glass the correct thickness works just as well though.

Mark

Posted by John Hawkinson (Member # 1135) on 04-02-2008, 12:28 AM:

I definitely know zilch about lapping, but I'm a bit confused:

Do you lap the star or the cam?

It sounds like you're not lapping in-place?

What significant difference is there between rubbing the cam with a piece of fine sandpaper, and "lapping" it with a piece of glass and some lapping compound? Presumably, Mark, you test after each lap of lapping, or you use a micrometer on the cam, or...?

How do you lap a round feature (cam) by hand with a piece of glass in an even fashion?

Just kinda curious...

--jhawk

Posted by Randy Bowden (Member # 587) on 04-02-2008, 02:04 AM:

I will give a general rundown on how I do things. first off lets get something established here, when I say that a cam pin is oversized we're talking about a very slight amount. For instance today I did an Ultramittent rebuild. The cam fit the star perfectly out of the box. no problem, it ran nice and quiet. Later in the day I went to do a simplex rebuild. A test fit of the pin indicated right away that it needed work. It pulled through rather stiff, or shall I say pushed through. What I do first is clean the parts completely of the oil coating that Lavezzi leaves on. Then holding the star in one hand and the cam in the other I test the fitting of the pin through the slot. It it needs work, I clamp the cam in my vice and proceed to scrub the surface of the pin with 1200 grit. I use a narrow piece of sandpaper folded in half. The trick is to hit the surface as evenly as possible from all sides. If your starting off with a cam that just needs a new pin, then you can chuck the pin in a lathe or drill press and work it that way, the only real down side to that being that cam pins don't always want to press in strait, at least not for me anyway. Now I know my method may sound a little crude and quite frankly it is, but it works and with enough practice it works really well. The only Lavezzi cam that I never seem to have to do this with is the Pro-35.

Posted by Richard Fowler (Member # 893) on 04-02-2008, 06:20 AM:

Sometimes pins depending how they are pressed ( preferred ) or "tapped" in will create a mushroom head that will require dress down. Lapping power is very fine and was more common when some make of projectors required lapping of shafts and sleeve bearings for fit.....I still have powder, stones in the shop with associated laps and tools.

Posted by Louis Bornwasser (Member # 3063) on 04-02-2008, 09:53 AM:

We try not to disturb the surface hardening on the pin at all. The inside of the star is cross-hatched. It is that surface you want to reduce if you lap or run-in.

Much more of a factor is "lack of squareness" on the majority of case halves, especially the XL and century. This will cause a binding when the pin engages if not corrected. This (& lack of oil) are the main reasons why intermittents fail in the first place. Louis

Posted by Mark Gulbrandsen (Member # 72) on 04-02-2008, 10:20 PM:

JHawk, You lap out the slots in the star... on a piece of flat glass.. just keep track of how many strokes and above all don't go crazy.. it doesn't take much to loosen up the fit... but I like Randy's idea better and plan on giving it a try...

I'll try your method next tight pin I come aross Randy... its interesting to say the least... I have a friend thats a knifemaker, he hardens his own steel!! He has a Rockwell hardness tester that we've tested alot of projector parts and the results are not always what you think you should find... generally not very good. Also, most cam pins which are nothing more than perfectly sized(not always) dowell pins are hardened completely through so a little scoring of the surface is totally irrelevant to its wear factor... its very good for oil distribution.

You're right on about the lack of case squareness Louis!! Century's are especially bad... if you measure the squareness of the flat surfaces in relation to the bore for the bushings you will more than likely find they are off. I don't see this very often on X-L cases though... in general they are pretty good. Some century case halves have been so far off they are not even salvagable... I suspect the fixtures at the factory were worn out but they kept producing them anyway.

Mark

Posted by Louis Bornwasser (Member # 3063) on 04-03-2008, 10:31 AM:

It is important to note that this is not a recent problem; it goes back to the very beginning. Strong, in fact, has done very well in terms of squareness. Louis

Posted by Randy Bowden (Member # 587) on 04-03-2008, 11:07 AM:

It's true, the century's can be a real pain. I have no problems with the simplex.