Adhesive/cement required for a ceramic insulator

[GreensandsParticipant @greensands]

If pursuing the dimmer option, what would be the options in terms of readily available,   off the shelf units capable of handling a 500W load?

[John HaineParticipant @johnhaine32865]

500 watts!  Good grief, that projector must get hot!  Please could you post a picture of the bulb?  I would have expected 50W max.  Quick look online suggests that many bulbs these days are low voltage – 12 or 24V.

Here are a couple of dimmers that could handle the load – one Screwfix the other RS.  I notice that there is a minimum effective output of 40W mentioned.  You’d have to experiment to check that set to minimum it doesn’t overload your bulb.

https://www.screwfix.com/p/crabtree-platinum-1-gang-1-way-dimmer-switch-satin-chrome/23675

https://docs.rs-online.com/f4e3/0900766b814fdd58.pdf

If what you want to do is use the projector rather than exhibit it I would suggest you strongly consider upgrading to an LED source with appropriate power supply (nowadays cheap as chips).  Several sites mentioned by Google that describe this.

All kind of weird and wonderful arrangements were used in old mains supplies.  I bought a sixpenny radio from a jumble sale with a “line cord”, a mains cable using resistance wire to drop the volts.  My dad got it working and I listened to it for years in bed, warming my hands on the cable in winter!

[Russell EberhardtParticipant @russelleberhardt48058]

Incandescent bulbs have a low resistance when cold so they would draw an excessive current when switched on.  I suspect that the taps on that resistor are to enable the power to be ramped up slowly so that there is not an excessive surge when switched on, which can shorten the lamp life.  I would be inclined to try to find a replacement 240 V lamp and fit a suitable NTC thermistor in series to limit the initial current and not use that resistor.

Russell

[Ian PParticipant @ianp]

Someone mentioned that the ceramic element support has mounts at both ends, if so then maybe a bit of tweaking to them could apply enough end-to-end pressure to keep the break closed.

I would not fancy the idea of a metal strap to keep the two parts of the support together and as has been mentioned suitable adhesives are hard to come by or expensive.

My suggestion would be to use glassfibre cord or lace to hold the support together. Installing several turns end to end and then tying it off. It will be heatproof and unlike a metal strap arrangement it will cope with long term expansion and contraction.

Ian P

 

[Keith LongParticipant @keithlong89920]

Hi Greensands, Have a look (internet search) for Vitcas products. It seems that they do a high temperature adhesive for gluing the ceramic seals on stove / oven / wood burner doors and they do a small bottle for little money. That especially combined with Ians P’s suggestion of the glass tape or cord as an additional support should do the job.

500 watts for a projector lamp isn’t unusual, I seem to remember that the 16mm Bell and Howell that we used at school was 1000 watt, and theatre lanterns even for a small auditorium were often 1000 watt which is why the place got so hot especially during the summer when you might have 15 or 20 lanterns on all the time in a production. Often the dimmers were arranged to keep a smallish (relatively) current flowing through the lamp continually to avoid the thermal shock on the filament and so prolong the life of the bulb – they were quite expensive.

[peak4Participant @peak4]

See half way down this page for some limited details, including the wattage and the switch design
https://www.pathefilm.uk/95gear/95gearspecto.htm

By 1951 Specto had revealed a larger version of their established projector model, using 900 foot / 300 metre spool arms and fitted with a 110 volt 500 watt A1/7 pre-focus projection lamp, fed from the 200 to 250 volt mains via a dropper resistance mounted in the lamphouse to benefit from the powerful fan cooling of the lamp. This meant this new design gave a brighter picture, but could also run on both normal A.C. mains but also D.C. mains supplies which still existed in odd areas of the UK and also overseas. Because there was no mains transformer, total weight was reduced to 12 lbs.

Specto “500” projector models were introduced for 8mm, 9.5mm and 16mm, but a dual gauge 9.5mm / 16mm model was also introduced, with cleverly designed spring retained interchangeable sprockets, interchangeable spool spindles and an improved film gate with snap-on 9.5mm pressure plate and double recessed front gate plate, served by a twin-claw film movement. A lever withdrew the claw assembly for easy access to the swing out the gate assembly (after the lens is removed of course!) for cleaning or gauge change, whilst a two position lamp switch enabled some surge suppression when turning on the lamp. All in all an excellent redesign which also led eventually to a dual gauge 8mm / 16mm model. By now, finish was in a modern bronze style with smart white knobs for motor speed and on/off, lamp dim/bright. Maybe some finish after the mid fifties was a grey hammertone glossy finish. As the advert says – “Projection Perfection”!

Bill

[duncan webster 1Participant @duncanwebster1]

Both of John’s links quote 400W max load.

Ebay item 304808637300 has 4 kW capacity, comes in a box, and is UK supply. Claims to be good for lamps and motors, both of which have surge current. Costs <£10.

[Author]

Posts