8mm Forum: Belts, to tight , to loose

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Posted by Bruce Wright (Member # 2793) on March 17, 2012, 09:34 PM:

Picked up two (2) B&H 482a projectors. Neither had a belt, so I ordered a belt from two different ebay dealers. The belts are not the same lenght. Installed the belts. One belt fits very loose and the other very tight, however, both projectors work ok. I am some what concerned about the tight belt. Is there a
"rule=of= thumb" for belt tension ? I've been away for a while
(hospital 7 days plus recovery) Today was first day back in my lab. Watched Charlie Chaplin-The Pawnshop- Sure made me feel a LOT better. Thanks

Posted by Joe Taffis (Member # 4) on March 17, 2012, 09:58 PM:

[Razz]

[ March 21, 2012, 09:32 PM: Message edited by: Joe Taffis ]

Posted by frank arnstein (Member # 330) on March 17, 2012, 11:32 PM:

Hi Bruce and Joe,

With projector belts, my opinion is that too tight is probably worse for the projector than running too loose.
I usually try to run my projectors belts as loose as practical but without any slippage ocurring. There's less internal friction to overcome giving good variable speed response and much less wear on the motor and shutter-shaft bearings. Running speed is effected when overtight belts are used resulting in a slower and weaker machine, struggling to get up to its correct running speed, getting hotter than usual and sometimes they will stop running after a while when the motor wiring burns out.

So I believe too loose is preferable to too tight, but the correct belt is the best belt to use.

This subject reminded me of the story about Goldilocks and the three bears. If you recall, the medium sized bed was the best size for Goldilocks. Not too big, not too small, but just right. The same basic principle can be applied to projector belts.

dogtor frankarnstein [Wink]

[ March 22, 2012, 09:49 AM: Message edited by: frank arnstein ]

Posted by Bruce Wright (Member # 2793) on March 21, 2012, 03:14 PM:

Dogtor Frankarnstein's belt information seems to be correct. This B&H projector has a split variable speed pulley mounted on the drive motor shaft. The speed control is a mechanical arm that presses on the end of the variable speed pulley causing it to expand or contract. The belt must be loose to allow for this movement of this pulley. [Cool]

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