8mm Forum: Belt is not melting or loosen, but cracking. What material is this?

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Posted by Winbert Hutahaean (Member # 58) on January 19, 2017, 10:59 PM:

I have found many times my projector belts got melting or loosen, but this time I found it cracking.

So do you think this is because of the climate here making this crack or is it because of the different between the rubber material?

thanks

Posted by Maurice Leakey (Member # 916) on January 20, 2017, 02:38 AM:

Belts often crack like that on my 16mm Bell & Howells, and it's not the UK climate to blame!

Posted by Phil Murat (Member # 5148) on January 20, 2017, 02:11 PM:

Hi Winbert,
Depending on lenght, Shape section, etc.... try to find an equivalent in polyurethan material.

Polyurethan benefits :
- Higher resistance to friction
- Higher strenghness
- Many Fluid resistance (Oil, Water, etc...)
- Different hardness (in "Shore" Unit) can be obtain

Posted by Winbert Hutahaean (Member # 58) on January 20, 2017, 02:12 PM:

Is it the material? Perhaps syntetic rubber to blame?

Posted by Andrew Woodcock (Member # 3260) on January 20, 2017, 02:19 PM:

It's how almost all Vee belts or Square profiled drive belts deteriorate before they eventually fail.

Even toothed rubber drive belts crack in between teeth before they fail.

Nearly all I come across in industry end their days like this.

It's simply wear and tear. Can be accelerated significantly however by over tensioning a drive belt and then also commonly leads to premature bearing failure also.

Never expect any kind of drive belt to last forever, they are designed to have a serviceable lifespan and like bearings and seals are therefore classified as consumable wear items.

Posted by Phil Murat (Member # 5148) on January 20, 2017, 02:20 PM:

That seems to be standard rubber.

How many years old are they?

As Andrew says, pay particular attention to tension. Overload leads to bearing premature wear.

What is the humidity percentage in your country usually ?

Posted by Steve Klare (Member # 12) on January 20, 2017, 02:22 PM:

This is very typical looking belt failure: I've seen it all the way from movie projectors to car engines!

If you think about it, a belt going over pulleys gets flexed, gets un-flexed and does it again every time it goes around the pulleys. This is like somebody taking it in their hands and bending and unbending it a couple of times a second...-for hours!

Something's gotta give eventually!

I committed to doing a show for the Cub Scouts a few years ago. I checked out the machine I wanted to use and the belts looked like yours. I ordered a new set and begged the guy to rush ship them: they arrived on time by four hours!

(One less thing to worry about...)

Posted by Rob Young. (Member # 131) on January 20, 2017, 02:40 PM:

Audi Cam belt; 110,00 miles or every 5 years.

Maybe projector belts should be made from German rubber?

Obvious questions, Winbert, but how old is the belt, how many hours has it run and where did you get it from?

Posted by Winbert Hutahaean (Member # 58) on January 21, 2017, 05:53 AM:

This is not the original belt. I bought it from Ebay, I think 'isellprojectorbelts" ot something.

The original belt was last very long time and got loosen after sedral years. This new belt was only one year old and has been like this. This crack does not have any relation with working hours because I did not use my projector. This is more like a life span, whether we use it or not, it will crack due to the age.

The humidity in my country was so high between 80-95%. While the temperature was around 25-32 celcius

Cheers,

Posted by Steve Klare (Member # 12) on January 21, 2017, 06:22 AM:

That's interesting: I get my belts from him and usually get at least five years between replacements.

Posted by Phil Murat (Member # 5148) on January 21, 2017, 07:38 AM:

Hi Winbert,

There is a high probability a High Humidity rate accelerate rubber material aging process.
Then due to proximity for sea side, salt can be found in the air.Probably a mix of humidity / salt is not good for rubber material.

If you want to keep your machine for a long, it should be interesting to replace rubber belts (and rollers, as necessary) by equivalent made from polyurethan material.

I did that for an EIKI projector arms belts......

Phil

//////////////// UPDATING /////////////////

I have observed on the picture the pulley involved is showing a "V" groove.
It give me the idea a standard belt ("O" section) made of Silicon material could fit properly, but may be it could be difficult to find....

[ January 23, 2017, 01:12 AM: Message edited by: Phil Murat ]

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