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AVAILABLE NOW, MAY 2018

Bell & Howell Worm Gears For Sale Page

new Bell & Howell worm gear £36.00 UKP each. Post to worldwide: £4.80
QUANTITY DISCOUNT:

NEW REPLACEMENT WORM GEARS available now ~ MAY 2018

Now available once more. Improved white nylon solid design machine cut new worms. New solid nylon worm gears manufactured to exact Bell & Howell thread dimensions.

Purchase via the Paypal button above. Includes printed Service Manual and Printed Parts Catalogue. Worldwide Airmail Postage £4.80

Bell & Howell part number 2304782.

New worm gears new Bell & Howell Worm New non-animation worm gear shown fitted to Bell & Howell 1695. New worm diameter 36.86mm.

 

Worm gears on Bell & Howell projectors are prone to hairline cracks that develop into fractures that eventually cause sudden breaking up while the projector is running. Almost all Bell & Howell projectors have cracked worms.

With the 'animation' model Bell & Howells, the worm gear consists of a thin outer nylon shell with a helical 'archimedean' worm gear that drives the sprockets and is prone to cracking. Replacement requires a major strip-down of the projector to replace the broken worm, usually with a solid, non-animation one.

Below: Original worm thread pitch of 2.5mm measured on old worm.

Old B&H Worm Gear MeasuredB&H Old Worm Thread 2.5mm

Cracked animation worm gear from a Bell & Howell model 1695.

 

Bell & Howell Worm Gear Intact Here is an an example of an original nylon 'animation' worm gear shown in a Bell & Howell model 2592. It is rare to find an original worm, as shown in this example, that remains uncracked and intact. As can be seen in the photograph below, a catastrophic break has developed from a crack in the thin outer shell.

Bell & Howell Cracked Worm Gear on Model 655 Typical broken worm.

FITTING THE NEW WORM:

It is sensible to 'run-in' the worm gear mechanism on the bench to be sure that the worm gears are freely running before reassembling. In the Bell & Howell repair manual provided there are is a diagram plan to make a home-made motorised jig for setting up, adjusting, and running in the mechanism before fitting back in the projector.

There should be slight 'side shake' felt at all positions as you grasp the large plastic gear wheels that engage with the worm. You may need to apply a needle file to the large gear wheel teeth at the positions where there is binding, or no side shake is felt.

When the projector is running with the lamp on, the gears will expand due to heat, so it is necessary to allow sufficient clearance to avoid binding or uneven running.

 

New Bell & Howell projectors stored for many years in a government warehouse unused were all found to have cracked worm gears. This indicates that the problem was not incorrect lubricant or missuse. There is evidence that some Bell & Howell projector worm gears with diverse hairline fissures (that do not join together) can be run regularly without catastrophic failure. However it is only a matter of time before an original worm gear will inevitably fail. A Bell & Howell projector that has had a replacement solid worm fitted is to be preferred.

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