Film-Tech Forum ARCHIVE: Flimsy plastic lamp focus parts

This is topic Flimsy plastic lamp focus parts in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Michael Schaffer (Member # 1204) on 12-11-2003, 10:10 PM:

I am having many unhappy moments with the flimsy plastic lamp focus gears in older Christie consoles (for instance, CH40 and similar). A lot of them are broken [Frown]

Usually it is only the small wheels which are stripped. Not surprisingly, Christie apparently don`t stock those parts anymore - but they are happy to sell the entire assembly for upwards of $300 [Mad]

Does anybody know where else these parts might be available?

Posted by Mark Gulbrandsen (Member # 72) on 12-11-2003, 10:37 PM:

Well I've always wanted to gut a CC40 anyway and install the new reflector and stuff. Sort fo like a Phoenix kit for the smaller wattages. I think all the UV light is pretty tough on the plastic over the years. Anyway, I think you'll find the new assy. a bit improved over the old one. Call Dennis and ask him about it...I recall it being a bit different. We may also have those gears that you need in stock, or a used assy.
Mark @ CLACO

Posted by Randy Stankey (Member # 64) on 12-11-2003, 11:13 PM:

We had the same problem in the CFS consoles that Cinemar used to buy. A lot of the problem has to do with the fact that the plastic deteriorates over time due to exposure to heat and UV. It gets brittle and cracks.

I think the idea was to provide some electrical insulation to isolate the (potentially) live parts of the rack mechanism from the rest of the projector and, theoretically any operator who might be adjusting the controls. I don't buy that, though. I don't believe that less than an inch of plastic will stop 100 amps of current, let alone 30Kv strike voltage.

Lighting Images sells parts for CFS consoles, now that CFS has gone tits up. I don't know if the gears are the same size but it's worth a look.

I also think they sell brass versions of the same gears. No chance of them getting brittle. I was replacing brittle gears in CFS consoles with them. The work great. I can't imagine why any crown/bevel gear with the right shaft diameter wouldn't work as long as both gears were identical and had a small enough diameter/height to fit in there.

Posted by Gordon McLeod (Member # 33) on 12-12-2003, 09:18 AM:

In the CFS and ORC consoles the cathode end of the lamp was grounded anyway so they didn't need any issolation
they probably used the plastic as it was cheap
I would not be suprised if that was not an off the shelf gear that is found in many other products in industry

Posted by Tim Reed (Member # 137) on 12-12-2003, 09:43 AM:

They were motor gears in the Barbie record player.

Posted by Greg Mueller (Member # 17) on 12-12-2003, 10:04 AM:

A lot of the time manufacturers will use off the shelf gears that are of a specific description, rather than making a proprietary gear for one application. I have several manufacturers catalogs and would be glad to try to match up and find a replacement gear for you, if you can find an existing whole plastic gear or enough parts of one to measure. I have some gear teeth measuring gauges and such that would make trying to figure out what you got, a little easier. I'm taking a short vacation (starting tonight) but will be back next week.
I might even be able to find another plastic gear.

Posted by Gordon McLeod (Member # 33) on 12-12-2003, 10:12 AM:

Greg could you post links to some manufacturers of stock gears as there are lot of applications a stock gear replacement could come in handy for

Posted by Greg Mueller (Member # 17) on 12-12-2003, 10:46 AM:

The one I use the most is Stock Drive Products / Sterling Instrument.
I have all these catalogs and finding stuff in the book is much easier than on the web (for me)
I'm having trouble getting the Globe Gears site to load

Berg Gears
http://www.wmberg.com/

Globe Gears
http://www.rushgears.com/framecontain.asp?pagetype=index

Stock Drive Products / Sterling Instrument
http://www.sdp-si.com/index.asp

Posted by Michael Schaffer (Member # 1204) on 12-12-2003, 02:08 PM:

I will see that I can take some samples from a CH console that we can measure. These consoles are quite common. I am sure many F-T members will come across them in the field, and often find those gears cracked. It might be very helpful to have that information - I am sure the relevant parts are quite cheap...

Posted by John Pytlak (Member # 331) on 12-12-2003, 02:25 PM:

Finding a replacement part by measuring old ones is fine, but shouldn't this information be available from the equipment manufacturer, especially if they decide to no longer stock replacements themselves? I can understand old custom-made parts no longer being available, but an "off the shelf" replacement should be identified if it is still available from the OEM vendor.

Posted by Tim Reed (Member # 137) on 12-12-2003, 04:54 PM:

From Christie, are you kidding?! They want to sell him the $300 unit!

[Eek!]

Posted by Jack Ondracek (Member # 1466) on 12-12-2003, 07:59 PM:

quote:
I don't believe that less than an inch of plastic will stop 100 amps of current, let alone 30Kv strike voltage.

Actually, that much plastic probably would insulate well enough at operating voltages... the current is a non-issue. At 30 volts you could have 200 amps running through the lamp and the insulator would work as well.

As for the 30kV, that's quite another matter. However, there are plenty of lamphouses around that have their positive lines running along the back of the cabinet. If striking voltage isn't breaking through the cable insulation and grounding on the cabinet, maybe that plastic is more than enough.

...assuming that's why they're doing it & it's not just a matter of being cheap.

Posted by Michael Schaffer (Member # 1204) on 12-12-2003, 11:44 PM:

Tim - indeed they would want that. And that is not the only case where you would need a few small parts - and they don`t stock them but want to sell you a complete assembly for tons of $$$.

Posted by Daryl C. W. O'Shea (Member # 1303) on 12-13-2003, 09:14 AM:

I don't believe an inch of plastic wouldn't stop 30kV of electricity.

Most plastics have a dielectric strength that fall within a range of 17 to 24 kV/mm.

Common plastics include Polypropylene Homopolymer (PP) @ 23 kV/mm, Polyethylene Terephtalate (PET) @ 20 kV/mm, Polybutylene Terephtalate (PBT) @ 15 kV/mm, and Polyamides (PAs -- Nylons) @ 17 kV/mm.

Thermoplastics like Thermoplastic Polyurethane (TPU) or Thermoplastic Elastomer Polyolefin (TPO) would be much better suited for plastics used in lamphouses due to their superior UV resistance and suitable dielectric strengths of 20 and 24 kV/mm, respectively. Of couse they are slightly more expensive, but nothing serious.