8mm Forum: Elmo 16-CL pulley dimensions

This is topic Elmo 16-CL pulley dimensions in forum 16mm Forum at 8mm Forum.

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Posted by Dino Everette (Member # 1378) on January 01, 2010, 01:55 PM:

Does anyone have the pulley dimensions (ie: circumference or diameter) of the pulley combination for 18fps and 24fps, as opposed to the 50Hz 60 Hz

Posted by David Pannell (Member # 300) on January 05, 2010, 07:51 AM:

Hi Dino,

I have both types of 16-CL, and have the pulley dimensions for you, but I am at the office at the moment, and the measurements are at home.

I'll post the answers for you here as soon as I get hold of them.
______________________________

OK! Now arrived home, so here are the dimensions of the pulleys you asked for. As you may have read in a previous post, I have turned down one of my motor pulleys on a lathe to give me 16fps on our 50Hz mains supply - but that's another story - it's just in order to let you know that I took all pulley measurements while I was doing the job, using a vernier calliper. All measurements are across the flanges of the pulleys - NOT across the valleys.

EUROPEAN VERSION - 50Hz only, but can change film speed:

MOTOR PULLEY
18fps = 24mm. diameter
24fps = 30mm. diameter

SHUTTER SHAFT PULLEY
18fps = 63mm. diameter
24fps = 58mm. diameter

USA VERSION - 24fps only, but can change supply frequency:

MOTOR PULLEY
50Hz = 30mm. diameter
60Hz = 26mm. diameter

SHUTTER SHAFT PULLEY
50Hz = 58mm. diameter
60Hz = 61mm. diameter

You can easily see that the 24fps setting for both versions uses the same size and ratio pulleys for the 50Hz supply.

I hope this helps. I'm interested in your reason for wanting this information.

Cheers,

[ January 05, 2010, 09:45 AM: Message edited by: David Pannell ]

Posted by David Pannell (Member # 300) on January 06, 2010, 02:06 PM:

Bump.

Calling Dino Everette.

Posted by Dino Everette (Member # 1378) on January 06, 2010, 04:53 PM:

I wanted to change the speed of my elmo, and thought there were US speed pulleys (as are mentioned in the owners manual) Also I recall you stating you had specially made a pulley to make one of yours into 20fps, so I was figuring it was all just a matter of having the right pulleys on the machine to keep the motor constant, rather than a UK only option of the speed change... [Confused]

So is there NO way to alter the speed of a US elmo in the US?

Posted by David Pannell (Member # 300) on January 07, 2010, 02:41 AM:

Hi Dino,

A little confusion here, I think.

The 20fps results from simply using my USA version of the 16-CL on its 60Hz setting, on our 50Hz electricity supply. This results in the shutter shaft turning at the equivalent of 20fps, as there is a fifth difference in frequency and therefore a fifth difference in speed.

I achieved the 16fps speed simply by turning down the 60Hz section of the USA version motor pulley from 26mm. dia. to 21mm. dia.

I then purchased a new USA pulley from Richard Patchett, as the European pulley is as rare as hen's teeth.

Thus, the EU model remains unaltered, giving 24fps and 18fps.
The USA model gives 24fps and 20fps with the standard pulley, and 24fps and 16fps with the turned down pulley.

I hope that makes the procedure clear.

If you are wanting to achieve 18 or 16fps with your USA machine, as well as retaining the 24fps, I'm afraid your only option is to turn down the motor pulley in the correct ratio.

You need to bear in mind that it is important to maintain the correct ratio between the motor and shutter shaft pulleys, otherwise you will have to adjust the motor position as well, whenever you wish to change speed, as the belt would be either too tight or too loose on one or the other settings.

Having said all that, it isn't a difficult task, and certainly well worth the effort if you wish to screen silent films.

Good luck, and please let me know if I can be of any further help.

BTW, if you swapped the belt to the 50Hz position, you would get 24fps + 20% = 28.8fps!!!

THEREFORE, my considered recommendation would be to purchase a new spare pulley from Richard Patchett, (so there is no chance of ruining the stock pulley), and turn down the larger diameter to give 24fps - this would be the normal 50Hz position, and then turn down the smaller diameter section to give 18fps.

Although the calculation of the correct ratios would seem the way to go, and you can do this initially, as you get nearer to the correct size, then a more reliable method would be to do it practically by turning down a millimetre at a time, and use a stroboscope till you get the speed exact - that's how I did it!

Best regards,

Posted by Dino Everette (Member # 1378) on January 07, 2010, 10:37 AM:

David forgive my ignorance, but I think I understand... when you state "turn down" do you mean have a machine shop reduce (ie: grind..or make smaller) the small pulley, or will this have to be done on both pulleys?

Posted by David Pannell (Member # 300) on January 07, 2010, 12:13 PM:

No problem Dino.

I refer to turning down the pulley diameter on a lathe.

"Turning" is the act of spinning an item in the jaws of a lathe chuck in order to shape or make smaller. A special cutting tool is positioned and bolted precisely to a tool holder on the bed of the lathe; and by means of rotating threaded shafts, which can move the tool holder in various directions, the cutting tool is brought into contact with the item to be worked on. Cutting tools can be made in an infinite number of shapes and sizes to achieve any desired shape of the finished article.

You only need to do it on the stepped motor pulley, but it would have to be on both sections of this stepped pulley to give you your two film speeds. Do not touch the shutter shaft pulley at all.

Hope this explanation helps.

Best,

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