8mm Forum: Wrong size belt?

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Posted by Chad Shumaker (Member # 2384) on December 18, 2013, 07:56 PM:

In trying to remedy recent problems with my Sankyo 700, I'm starting to wonder if the belts I purchased are the wrong size.

Would a too-tight belt cause the projector to slow down/change speeds during a show?

Posted by Dominique De Bast (Member # 3798) on December 19, 2013, 04:31 AM:

It may be the shape I have a similar problem. The replaced belt is the same size than the previous one but it is a round model though the other was a plate one.

Posted by Maurice Leakey (Member # 916) on December 19, 2013, 09:39 AM:

If the incorrect shape of belt is used, round or flat, it will not seat correctly on the drive pulley, thus giving incorrect speed to the mechanism.

Posted by Dominique De Bast (Member # 3798) on December 19, 2013, 12:38 PM:

The trouble is that I bought the belt from a cine related dealer and it had the correct projector reference written on the plastic bag. You cannot guess it it will be exactly the same belt or just a belt with the same size. It may (I don't know) make no difference in some cases but in other you get problems.

Posted by Chad Shumaker (Member # 2384) on December 26, 2013, 10:18 PM:

Ugh. Just got new belts in the mail today from isellprojectorbelts on eBay. These are round going into V shaped pulleys on my projector. Still the same problem. Speed is fluctuating.

I'm really getting frustrated. I'm wondering the following-

1. Did I thread the belt wrong? It's got a weird path. Does anyone have a picture of how it should look?

2. Is there something wrong with the motor? I've hit it with some 3 in 1 and blown it out with air.

3. Is it me? Am I just destined to not be a part of this hobby??

Is there anyone state side I can send this projector to for a good going over?

Chad

Posted by Maurice Leakey (Member # 916) on December 27, 2013, 10:19 AM:

Chad
It sounds more like a problem with the electronic control of the motor. Why not contact Richard C. Patchett in Royal Oak, Michigan which I believe is about 220 miles from you. Richard is a member of this Forum. Here is his web-site.
http://www.rcsclassic16mm.com/

Posted by Richard C Patchett (Member # 974) on December 27, 2013, 10:46 AM:

Greetings
Thank you again Maurice

Hope you had a Wondrfull Christmas
And have A Happy New Year to you and yours

Waiting for Chad to contact me
RC

Posted by Joe Taffis (Member # 4) on December 28, 2013, 08:52 AM:

Chad, I don't have a Sankyo 700, but I'm curious to see the inside of it. Could you post a pic with the back off? Thanks....

Posted by John Capazzo (Member # 157) on December 28, 2013, 09:38 AM:

Some Sankyo have speed pots as Elmo has. One for 18 and 24. Correct the speed with a plastic screwdriver or shave a fork to fit the slot. No steel when it's running.

Posted by Chad Shumaker (Member # 2384) on January 24, 2014, 06:34 PM:

Man, I hope this is it. I ordered some belts from ES Photographics in the UK. They fit *much* better in the pulleys than both previous sets.

I also read on Phil's Vintage Movie Films that following a belt change, the speed pots need to be adjusted. I had to do this before when I first got the projector to correct a sound issue so I knew where they were.

Upon close inspection of the projector innards, I noticed that the pots were very tarnished and dirty. I sanded them with an emery board just a bit and then cleaned them with a swab soaked in electronics cleaner. LOTS of dirt came off.

I also noticed that one of the pulleys had old belt buildup on it. It received a good cleaning as well.

New belt installed. Pot adjustment made to the proper now clean pot. Just ran a 400' reel with no problems.

I will say those pots are sensitive. One little tweak to slow and the speed issue seemed to rear its ugly head. I can help but wonder in the dirty contacts were the source of the issue. I will run a few more reels tonite and see what happens.

Thanks to all who offered advice! I really appreciate the input and suggestions.

By the way, here are the pots for those who are curious. The arrow is pointing to the pot that adjusts 24 fps. The last photo also shows a third pot that as of this writing I have no clue what it does.

Posted by Lee Mannering (Member # 728) on January 25, 2014, 08:04 AM:

Hi Chad. Before you start looking too deep and possibly create another problem many of the 700 range models are now showing signs of worn out/faulty switches that are just behind the main control switch. This fault can show itself often infrequently buy typically when you least want it to.

The test.
Does the slow down or stop start happen when the projector is operated in both forwards and reverse? If not it is likely to be a faulty micro switch. To change the faulty one (It’s worth doing them both) you need to remove the lower front cover and you will see the switches either side of the main switch shaft.

If you are not confident doing this repair always send the machine to a good service engineer. We are very lucky in the UK to have our Bill Parsons amongst others and I’m guessing you have a similar guy in the USA.
Regards

Posted by Chad Shumaker (Member # 2384) on January 30, 2014, 06:25 PM:

OK- another new belt and another new problem, but first thing's first-

Again thanks to all for advice and guidance.

Lee- The slowdown occurs in both forward and reverse so I don't think the microswitch is at fault as per your suggestion.

The new belt is a bit thinner than all previous. Sits very well in the pulleys- until projection begins. There are two little pulleys leading up to the main and the front one is the culprit. This actually happened on previous belts too. It wants to jump out of the pulley.

When there is no film- smooth sailing the belts do exactly as they are supposed to. In reverse no trouble. Forward projection belts want to jump this pulley and the bottom of the belt goes slack.

See pics below for details.

Above is the entire path the belt follows. Have I threaded incorrectly??

Here are the little pulleys that are being a pain. Specifically the front one. With no reel, no problem. Pulling film it wants to slip.

Now I also noticed a switch on the side I had ignored before. "Auto/Manual". It has been set to auto as far as I know. On a recent playback attempt I switched it to manual and there was no slowdown.

I think it deals with sound recording but could it affect playback too?

Sorry if these are silly/dumb questions but I'm really frustrated! [Smile]

Posted by Maurice Leakey (Member # 916) on January 31, 2014, 02:54 AM:

I've just looked at my Sankyo which is a model 501 and your threading of the belt is correct, however, your belt is much smaller than mine, also, mine is not round, it's three-sided.

The auto/manual switch is purely for recording. The auto setting lets the projector set itself to an optimum level. The manual setting lets the user select their own level by using the volume control. There is no connection whatsoever to the motor.

Posted by frank arnstein (Member # 330) on January 31, 2014, 09:50 PM:

Hi Chad,

I think your problem is that the main-drive friction-clutch is faulty and its not able to slip as it should.
It looks like its been overtightened by some one in an attempt to make it drive. Try backing off the two nuts that adjust the clutch pressure. The clutch should slip completely when you prevent the take up spindle from turning, while in forwards project. The motor should not slow down because the clutch limits the load on the motor by slipping at a certain load.
If it can't slip, then the motor will slow and the belt will try to come off the pulleys and the bottom part of the belt will go loose like yours is.

In some cases similar to this, the friction material inside the clutch comes off one side of the clutch face where it was glued to. Thats when some people tighten the adjustment way too far in an attempt to make it drive. They get it to drive but then it wont slip at all, like yours is doing.
If they can't be adjusted, these clutches need to be dismantled and the friction washer reglued back onto the pressure surface where it was and then adjusted properly so it slips when needed instead of slowing down the motor.

So have a close look at the clutch and its operation.

dogtor frankarnstein
[Wink]

Posted by Chad Shumaker (Member # 2384) on February 02, 2014, 10:15 PM:

Once more thanks everyone for your time. I have officially shipped my projector off to Richard to see if he can fix it! Wow! What an adventure this has been... [Smile]

Posted by Maurice Leakey (Member # 916) on February 03, 2014, 02:52 AM:

There are times when help from a professional is a godsend.

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