Film-Tech Forum ARCHIVE: HELP! Century SA & Simplex SH-1000 Running At Different Speeds!

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Posted by Brett G. Sherris (Member # 3543) on 04-03-2006, 08:44 PM:

Resident Experts...

I recently mounted my Century SA head on a Simplex SH-1000 soundhead. Both units were throughly renovated by the entities that I purchased them from.

The problem is that the soundhead gearing appears to be running on-speed at 24fps, but the picturehead is running somewhere under 20fps (I know this because the fire shudder does not open on it's own). I have checked the weights on the vertical shaft, and the shudder WILL open if pressure is placed on the lever, but it will not under normal operation.

I have ascertained that I do have the correct 3.25" fibre meshing gear for these two models.

At this point in time, the supplier of each head has not been able to sleuth out this issue.

Does anybody here have any idea how to proceed to troubleshoot this problem?

Any and all help will be appreciated.

Brett

Posted by Sam D. Chavez (Member # 1841) on 04-03-2006, 08:58 PM:

Have you run film through the projector and soundhead? If the two are running at different speeds, film will either break or accumulate somewhere between the projector and soundhead.

Posted by Brett G. Sherris (Member # 3543) on 04-03-2006, 09:57 PM:

Sam:

As you suspected, the film pulls tight and tears sprocket holes between the last sprocket in the picturehead and the first sprocket in the soundhead.

I know for a fact that the soundhead is running faster than the picturehead.

I did a little experiment, I put a pencil mark at the 12 o'clock position on the bottom sprocket in the picturehead and on the top sprocket in the soundhead. Then I hand-turned the soundhead motor and rotated the soundhead sprocket ONE FULL clockwise revolution, and then found that the mark on the corresponding picturehead sprocket only moved to the 4 o'clock position.

This indicates that the picturehead is running at 8fps, exactly 1/3 the speed of the soundhead running at 24 fps.

B.

Posted by Richard May (Member # 2627) on 04-03-2006, 10:06 PM:

check all the fiber gears in the projector head for any missing teeth. Also check to see if the main drive fiber gear at the bottom of the projector head is meshing with the steel gear correctly at the bottom of the vertical shaft in the projector head. Lastly, check the fiber gear that mounts between the projector and soundhead for the correct number of teeth. Had one once that was wrong. Projector ran at different speed like yours is doing..

Posted by Dave Macaulay (Member # 813) on 04-03-2006, 10:28 PM:

The soundhead gear turns once every four frames. It has 16 tooth film sprockets and the drive gear is on a sprocket shaft.
I'm pretty certain that the projector main shaft is one turn = one frame.
So the projector drive gear must turn 4 times the speed of the soundhead output gear.
And the projector gear needs 1/4 as many teeth as the soundhead gear.
However - the only gear drive sets I know of are the same ratio, they might be different sizes but they differ in tooth pitch and angle. I don't know if you could get a mixed up pair to work at all.
Anyway, count the teeth and see if they are 4:1.
There are composite drive gears with a rubber shock-absorbing ring between a hub and a toothed ring. These are famous for slipping when the rubber breaks loose from the hub or toothed ring; the teeth can turn without turning the hub. This causes snapping film on startup or even a slow running projector depending on how bad the gear is and the projector drag. If you have these composite gears replace them. They haven't been made for decades so the rubber is hard by now even if "new old stock"; get new solid gears.

Posted by Brett G. Sherris (Member # 3543) on 04-03-2006, 10:48 PM:

Here is a picture of the fiber meshing gear I am currently using:

Posted by Monte L Fullmer (Member # 2797) on 04-03-2006, 11:43 PM:

Being a SH-1000 (4-star) soundhead, wonder if the upper brass gear, that is attached to the upper holdback sprocket, in the soundhead transmisson has gone bad..due to lack of lubrication..causing gear jump for that upper holdback and causing the film to have the sudden tension problems between head and soundhead...

Then, I forgot, with this bad brass gear...could cause the variance of speed being that the projection drive sprocket is attached to that upper soundhead shaft ... which is attached to that brass gear...
-monte

Posted by Eric Robinson (Member # 2966) on 04-04-2006, 12:02 AM:

Does the sound head drive the projector head with a gear? If so, I have not seen this design before.

I have had trouble in the past with a Simplex projector and a 5 Star sound head when I put a belt on with the wrong pitched teeth. The motor drove the 5 Star sound head just fine, but the belt from the sound head to the projector was riding to high on the belt drive pulley thus causing it to run at a slightly different speed.

This probably doesn't help though if your situation only involves gears and one drive belt.

Posted by Will Kutler (Member # 770) on 04-04-2006, 02:23 AM:

Brett:

By the looks of the pic you posted of the fibre gear, that gear looks trashed!

Cheers

K

Posted by Brett G. Sherris (Member # 3543) on 04-04-2006, 06:39 AM:

Eric:

Yes, the picturehead is driven directly by gears.

Will:

This gear is nearly brand new! It has like ZERO operational hours on it...how could it be trashed?!

B.

Posted by Stephen Furley (Member # 1277) on 04-04-2006, 07:53 AM:

quote:
By the looks of the pic you posted of the fibre gear, that gear looks trashed!

I think it may just look that way due to the angle that the teeth are photographed at in the first picture. It does look new in the second picture.

Posted by Mark Gulbrandsen (Member # 72) on 04-04-2006, 08:08 AM:

Be sure that your projector has the correct main drive ger set.. you cannnot use a sync gear drive set. GR-8 is the correct fibre gear in your case. Also be sure that the two screws holding the fibre gear to the main drive shaft are tight. That gear is behind that lower cover that comes off. If you post a picture of your fibre gear main drive we should be able to tell if you have the correct one. IMHO you probably have a sync gear set as that would definately cause the projector head to run slower than thhe ssound reproducer. The correct projector main drive shaft speed is 720 rpm but the sync drive gear is smaller in diameter than the GR-8 standard drive gear.

Mark

Posted by Brett G. Sherris (Member # 3543) on 04-04-2006, 09:33 AM:

Well folks, it is clear that there are two schools of thought on this problem.

Konrad Schiecke (refurbusher of my Century picturehead):

"There are 2 different gear boxes for the sh1000 soundhead. the original one and one for what they call sync operation,1800rpm. You should have a 1725rpm motor on your soundhead. You could have a mismatch gear box to motor."

Sooo, if I am reading this right, Konrad thinks the problem is in the soundhead, and that the Simplex gearbox could be mismatched.

On the other hand, Fred Blank at Tri-State (refurbusher of my soundhead) has said:

"We are at the point that it almost must be the drive shaft gear set."

So it appears that Fred feels the problem lies in the picturehead with regard to the lower horizontal gear set.

In short, I now have two different schools of thought.

Anyone else care to weigh in on this?

Thanks,
Brett

Posted by Gordon McLeod (Member # 33) on 04-04-2006, 09:54 AM:

It is possible that the century projector has the GR8 gear installed for the direct drive version
If it was the gear box on the soundhead then both the projector and soundhead would both be running at the wrong speed not just one of the pair

Posted by Brett G. Sherris (Member # 3543) on 04-04-2006, 10:08 AM:

Gordon, good point.

One additional tidbit of information that might help the sleuthing here...

When the soundhead/picturehead are coupled together, it is very hard to turn the shutter shaft knob (although it is very easy to turn the gearing from the motor side of the soundhead). Since I have turned this knob on numerous occasions when threading Century projectors at my locale reperatory house – and there never seems to be any difficulty turning this knob - does it not suggest some disproportionate gearing somewhere?

B.

Posted by Richard Fowler (Member # 893) on 04-04-2006, 10:50 AM:

Using the shutter threading knob to move the projector is a poor design point on the Century and should be avoided. Outside of the speed problem which will be eventually solved, how tight do you have the gear mesh from the projector fiber gear to the soundhead gear.....there should be a very slight play on the tooth faces

Posted by Brett G. Sherris (Member # 3543) on 04-04-2006, 10:59 AM:

Richard:

Thanks for the note, but I have tried every spacing variation humanly possible for the postioning of the meshing gears. It has no effect whatsoever on the problem at hand.

B.

Posted by John Eickhof (Member # 323) on 04-04-2006, 11:11 AM:

I'll bet the lower gear set on the Century head is the M series direct drive! ( if the namelate says 'MSA' )Which would have been mounted on a M series R3 soundhead and direct belt drive to the main drive shaft. If the lower fibre gear has teeth angled at approx 80 degrees pitch off center of shaft it is, the standard GR-8 is a approx 22 1/2 dgree angle! Plus count the teeth on the steel gear at the bottom of the vertical shaft and the fibre gear on the main drive shaft ! The steep pitch is why it is hard to turn the mechanism & soundhead by the shutter shaft as the gear ratio is trying to turn the soundhead gears at 3-4 times the speed! Call Konrad and have him furnish you the correct GR-8 / GR-4 gear set.

Posted by Sam D. Chavez (Member # 1841) on 04-04-2006, 11:12 AM:

I would run a loop through just the sound head. The loop should be exactly down to the perf something that can be divided evenly into 90, as in feet per minute. Count the splice clicks on a stop watch for one minute. A 3 foot loop should come out to 30 clicks. This will tell you if the soundhead gearing is correct and you eliminate one variable.

Posted by Brett G. Sherris (Member # 3543) on 04-04-2006, 11:31 AM:

John:

The plate on the front of the Century head has the letters "SA" stamped into it.

Here is a picture of my picturehead from the gear side (sorry, the lower cover is still on in this photo).

Posted by John Eickhof (Member # 323) on 04-04-2006, 11:38 AM:

can you post a picture of the fibre and steel gears that are at the very bottom of the century head without the external fibre gear in the way? I will be able to tell by that for you..take the lower gear cover off and shoot the picture downward from the front corner of the head to see the gear set ...john

Posted by Brett G. Sherris (Member # 3543) on 04-04-2006, 11:49 AM:

John:

Here is a picture of the lower third of the Century picturehead from the gear side:

Posted by Louis Bornwasser (Member # 3063) on 04-04-2006, 01:04 PM:

John's suspicion is correct. You have the gears for the "Direct drive" Century. Swap the GR4,8 as Mark suggested and you should be OK. The soundhead is almost certainly OK as well as the flat drive gear since (as stated above) since there is gain/loss BETWEEN components. Louis

Posted by Mark Gulbrandsen (Member # 72) on 04-04-2006, 09:50 PM:

quote: Gordon McLeod
It is possible that the century projector has the GR8 gear installed for the direct drive version

Actually Gord the GR-8 is the standard drive gear and the GR-183 is the gear you're thinking of.... but I agree with Fred that its the projetor main drive pair.... An 1800 rpm gear box would just make both pieces run slow with a 1725 rpm motor but they would still be in the correct relaationship with each other.... HAS to be a wrong main drive set!!! Sorry Konrad but that pretty much spells it out....

EDIT:
Just saw the picture after posting the above......definately the wrong gears!!!

quote: Richard Fowler
Using the shutter threading knob to move the projector is a poor design point on the Century and should be avoided.

Absolutely! But the real existance of the knob was to indicate the locked position of the intermittent for threading purposes, assuming the knob is locked down at the correct point. Earlier Century's didn't have an actual knob but an angled revolving indicator that couldn't be grabbed for turning over the machine....

Mark

Posted by John Eickhof (Member # 323) on 04-05-2006, 09:33 AM:

Brett I would contact Konrad and have him furnish the 'standard' drive gear set. For some reason the mechanism was converted for use with a M seires Direct Drive soundhead. Once you install the proper gears, all should be fine. However you will have to dis-assemble by removing the the shutter shaft assy, the vertical shaft assy and the main drive in order to correct the problem, If you are not familiar with this proceedure, It may be best to return the head to Konrad and have him do the correction. Or if you have a more local tech have him help you. John

[ 04-05-2006, 10:54 AM: Message edited by: John Eickhof ]

Posted by Dave Macaulay (Member # 813) on 04-05-2006, 11:34 AM:

I shouldn't post from home where I don't have a projector to look at [Smile]

You obviously do have the correct drive gears between the soundhead and projector, but looking at the picture I was trying to figure out the ratio... the projector drive shaft obviously isn't one turn = one frame (as I thought) since the soundhead is one turn = 4 frames and those gears are obviously not 4:1. Checking a Century I find it is actually one turn = 3 frames, for 480 RPM at 24 fps.
Make sure you get the right main shaft gear. It looks like you have the "new" shaft that takes a GR-302 gear. Konrad should know what shaft you have and what gear it needs though.
Turning the unit over using the shutter shaft knob isn't recommended anyway, but a 5-Star soundhead is much easier to turn than the SH-1000 so the comparison is poor. It should be lots easier to turn - if you still want to - when you get the correct main/vertical shaft gears. The soundhead motor knob is right at hand and should be what you use.

Posted by Brett G. Sherris (Member # 3543) on 04-05-2006, 01:59 PM:

Everyone:

With the expert assistance of Gail at Tri-State Theatre Supply, who kindly spent three+ hours with me on the phone, I changed out the gearing on my Century head, and now everything is working beautifully.

Thanks to everyone here who pitched into this thread and lent their time to solving this issue.

B.