Intermittent interchangability

[Adam Liberman]

Hi,
I'm wondering what intermittents are interchangeable within the same brand. Specifically, will the same intermittent fit a:

Simplex Regular, Super, E-7, X-L, 35?

Century (P?), C, H, (S)A?

[Mark Gulbrandsen]

Generally not except the case of the Super movement also fitting in a Standard. The E-7, and XL are all by themselves.

Not sure about the Century P, do you mean H? However, there may have been a Century that existed before the C. I've never run into one.

The original C's have a sprocket fixed by two taper pins on a 1/4" shaft, but later parts and intermittents do have the screw and nut to fix the sprocket, and 5/16" diameter shaft.
In similar fashion the cam in the C is smaller, but the drive side is the same as the H and SA.

The C has a small star wheel, the same size as the Standard and Super, but to be honest, I never tried a C movement in an SA, or vice versa, although it may work fine either way as the drive side is the same.

The SA, and H have almost double the size webbed star wheel, and a larger cam to match the size of the star radius. Same size star and cam in a JJ as is in the SA. The star wheel shaft is longer to accommodate the 70mm sprocket.

The rare Cinemascope 55 projectors used the SA sized parts, except the cam had a dovetail driven by an internal fixed cam. The film was slightly accelerated so the film frame pulled down in the same amount of time as 35mm 4 perf would, as it was a 35/55mm projector

The Century VistaVision projectors initially used modified model C movements with alumnium 32 tooth sprockets, but they didn't hold up. Century used Brenkert intermittents highly modified, placed in a different housing and submerged in oil. Those were reliable. Most of the modified Century's made into VistaVision projectors used the SA movement, and those also worked fine.

I hope this helps...

[Adam Liberman]

Thanks Mark, that is helpful. I have 3 Simplex Regulars (but only one has its intermittent), and two Century C's (one with the pinned sprocket, and one with the nut). I've picked up a few inexpensive intermittents on eBay, so I was specifically wondering about the Regular/Super, and the C/SA interchangability, so it sounds like they are. The condition of those on ebay is of course a gamble, but I figure that at the least, I can practice rebuilding one without messing with the one on the projector. After I track down an RP40 film, I'll be able to compare the steadiness. I know that the C had the changes in the pins/nut, starwheel size, and whether the sprocket end-bearing is removable (I do have the drawings downloaded from Film-tech).

[Mark Gulbrandsen]

I have interchanged Standard / Super movements myself. I don't remember having the need to change a C for an SA, but in therory, it should work.

[Tj Hopland]

A Century C and H / SA will interchange but the different size star and cam places the sprocket in a slightly different place. If you place a C in a SA you loose a little framing range and change the angle of the film coming out the gate/trap. Where it gets interesting is if you place a SA in a C. The different sprocket location will now allow you to do a toothless sprocket or gear conversion depending on how hard you send it. The only thing that lets you sort of get away with it is the oil fill cap hits the light shield that is behind the trap. IF you were to frame it up without the shield you can run the sprocket right into the bottom of the trap. Even if the shield is tight you can slam it hard enough to break off the cap and take the tip off the teeth same thing if the shield is loose.

IIRC the part number is C1-BB-30 for the C and H1-BB-30 for the H and then later A machines. Century started out like many making a Simplex clone, possibly for the US military. There was a reason it was often called the Standard, it kinda became a standard design. Think of them like the small block Chev V8. It was a very popular decent design so there was a huge aftermarket so to speak. Many people made clones and parts and upgrade kits. Century was the model K I think. There was also Kaplin which I think was were the model K Centry came from. Perhaps Century was one of Kaplin's suppliers and they just ended up buying. Wenzel Ace was another one. Ballentyne had I think first the B which was almost a direct clone then the later BW which had a much larger and more roomy case, like Century C sized but was still a Standard simplex gear wise. Maybe it was even something like Century was a foundry and would do 'private label' castings for anyone that wanted to sell a projector?

The earlier Simplex and then Century intermittents were often used in some of the more portable machines. Which one you used depended on your framing concept. If you rotated the intermittent you used the Simplex and if you ran it up and down you used the Century. Devry I think was a Simplex. There was an early Christie that used a Simplex. The later Christie "Ultramittent" was very similar to the SA design but added seals and ball bearings. I think there were Charlie Ajiar studio machines that used both designs over the years.

On the early Simplex you would sometimes see single and double bearing referenced. This was the 'arm' on the intermittent. A single bearing meant there was just the internal bearing in the case cover so the sprocket was just hanging out with no outside support. Double bearing seemed to be a thing by the sound era where they added the arm to the outside of the sprocket with a bearing in it for better support. The reason the Simplex and Century style intermittents needed the outer support is there wasn't a lot of room for a bearing between the star and sprocket, like in the range of 1/2" or 13mm so not a lot of room for good support compared to say something like a Brenkert that had a much larger diameter shaft and a couple inches in the case.

On the Century C when you did the conversion to the bolt on 5/16 star you also had to use the sprocket with the LA suffix. The LA added a little shoulder section at the bore which was then the thrust surface that set the end play. The pinned 1/4" star, the H, and like an XL movement used that outer collar as the thrust surface. Memory is a bit fuzzy but I think the double bearing earlier Simplex also used the LA style sprockets. Anything with the pinned sprockets you need to find or build yourself a little stand that cradles and supports the sprocket so you can drive the tapper pins in or out without damaging anything. Those pins can be pretty tight and that 1/4" shaft isn't very strong.

[Tj Hopland]

After I track down an RP40 film, I'll be able to compare the steadiness

Since RP-40 is a consumable and pretty scarce these days I would do my initial testing and experiments by trying to see if your projector will project the sprocket holes with no or minor mods like maybe removing a heat shield. The sprocket holes were usually pretty decent on any film so you can use any film to work the bugs out and find out if you are close. Once you are pretty sure you got it dialed and have not make any major mistakes you can move to the RP-40 for a final short test.

[Mark Gulbrandsen]

Try Boston Light & Sound for RP-40....

[Adam Liberman]

Try Boston Light & Sound for RP-40....

Thanks, just messaged them.

[Sean McKinnon]

You spelled it wrong Mark

[Mark Gulbrandsen]

You spelled it wrong Mark

[Tim Reed]

I don't remember which way this goes... An SA intermittent will fit in a C mechanism, but you can run the sprocket teeth into the bottom of the film trap with the framer. I may have that backwards, though, it could be a C movement in an SA frame does that. Check before you turn the motor on to be sure. I serviced a circuit once that was full of Centurys with burred intermittent sprocket teeth.

[Adam Liberman]

I don't remember which way this goes... An SA intermittent will fit in a C mechanism, but you can run the sprocket teeth into the bottom of the film trap with the framer. I may have that backwards, though, it could be a C movement in an SA frame does that. Check before you turn the motor on to be sure. I serviced a circuit once that was full of Centurys with burred intermittent sprocket teeth.

Tj Hopland above says that it is when you put an SA movement in a C.

I'm assuming though that if the framing knob is centered and the film is threaded on-frame, you won't need to be adjusting framing enough for this to be an issue, although of course it would be best to be impossible under any circumstances.

[Mark Gulbrandsen]

I don't remember which way this goes... An SA intermittent will fit in a C mechanism, but you can run the sprocket teeth into the bottom of the film trap with the framer. I may have that backwards, though, it could be a C movement in an SA frame does that. Check before you turn the motor on to be sure. I serviced a circuit once that was full of Centurys with burred intermittent sprocket teeth.

That's correct Tim. The shape and length of the SA trap is very different than the straight gate C...

[Tim Reed]

... if the framing knob is centered and the film is threaded on-frame, you won't need to be adjusting framing enough for this to be an issue,

For you and me maybe... but not for the average sprocket jockey of those days.