8mm Thunderbird Projector question

[Philip Hamilton]

I recently purchased a very nice 8mm Thunderbird Projector in the box. It projects just fine HOWEVER the film keeps slipping off the black sprocket wheel on the bottom side thus causing a loss of the bottom loop passing through the aperture.

If I run it without a take up reel OR if I place my finger on the take up reel to slow it down the loop maintains. OR - if I place my finger lightly to keep the film threaded on the black sprocket wheel - the loop maintains.

Is this a worn sprocket wheel issue? All the teeth are there - it just doesn't maintain good pressure on the wheel and then what happens is the take up reel just pulls the film forward slowly until the bottom loop is gone. Running it like this will damage the film I am pretty sure...

Thoughts? Suggestions! Thanks!

[John Burgess]

It seems to me from what you say that the take up is too fierce and dragging the film under the bottom of the sprocket. I have never seen one of these machines before so don’t know if this could be adjusted. But you could give it a go.
John

[Ed Gordon]

Phillip, this was my first projector which was sold as a "Brumberger". The only time I had lost loops was from bad splices. It sounds like the tension on the take up reel is too high, and as I recall that projector had no means of adjusting the tension. My Brumberger used the metal spring "belts" which could be stretched to adjust the tension on take up.

[Philip Hamilton]

Additional testing shows that once the take up reel gets about 25 feet of film on it - the LOOP MAINTAINS. Is this the slightly additional weight to the reel or the ANGLE in which the film enters the take up reel?

I put some weights on the reel and it had no effect so I am guessing that the ANGLE at which the film enters the reel creates additional tension on the center sprocket assembly keeping the film flat and on the TEETH of that sprocket.

So if I SLOW the take up reel for about 90 seconds then everything seems fine after that. But I shouldn't have to do this should I? Are all vintage THUNDERBIRDS like this? I have the option to return the eBay purchase. Is very nice and clean but this is annoying.

[Osi Osgood]

Return ... find another. Go with a Eumig P8, the Cadillac of silent standard 8mm projectors! (Personal opinion).

[Philip Hamilton]

Return ... find another. Go with a Eumig P8, the Cadillac of silent standard 8mm projectors! (Personal opinion).

but it's not a THUNDERBIRD!!!

[Philip Hamilton]

Update: I found a rubber band that was kind of the same size as the spring belt. I put it on. the LOOP MAINTAINS!! So I need to STRETCH the belt I have out just a wee smidgey without ruining it......oh the pain...

[Ed Gordon]

Update: I found a rubber band that was kind of the same size as the spring belt. I put it on. the LOOP MAINTAINS!! So I need to STRETCH the belt I have out just a wee smidgey without ruining it......oh the pain...

Another option is to make a new belt. See: https://www.mcmaster.com/products/be...round-belting/

[Philip Hamilton]

Had no idea these belts were still in use....interesting...

I wonder why the belt is causing the issue now after 50+ years with this projector. I don't think belts get tighter do they? Funny that that little rubber band works by apply just enough pressure to turn the take up reel.

I had a similar problem with a GAF Dual 8 projector but I could adjust the tension with a small rubber wheel that turned the take up reel. There was a "sweet spot" for sure in that adjustment.

Something as simple mechanically as the Thunderbird certainly has nothing like that.

i even thought about 'greasing' the pulley so the spring band might slip just a bit and slow down.... It's a puzzle for sure...

[Philip Hamilton]

Well I took the belt and stretched it out just a bit. Now it works. Loop is MAINTAINED. Funny how that stupid flimsy rubber band also worked.

Thanks everyone for chiming in on this……

The THUNDERBIRD is simple. It’s loud. And GLORIOUS at the same time for me. I had this when I was 12. 54 years ago. I wish it had a better lens but hey it is whe it is …. Haha

[John Burgess]

Philip
So pleased you have resolved the problem with your projector, it really is rewarding when you complete a diy fix , happy projecting .
John

[Philip Hamilton]

So now I wish there were a way to change the lens. Other than finding a lens from another Brumberger or Thunderbird - would it be possible to use a different lens if you could get it to fit the slot? Of course I have never tried this before but I am curious.