8mm Forum: Bell and Howell worm gear

This is topic Bell and Howell worm gear in forum 16mm Forum at 8mm Forum.

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Posted by Barry Webb (Member # 1897) on July 03, 2010, 01:40 PM:

Hi all this is my first post and first time on a forum.I have been in to this hobby now for about 4 years starting with super 8 and then moving on to 16mm.I have about 6 bell and howells.
My problem is i have one 1695 that has had a new worm gear fitted by someone and it is to tight and the machine jams after a short time can any tell me if this this is a easy fix or a total strip down.
Barry

Posted by Maurice Leakey (Member # 916) on July 03, 2010, 02:52 PM:

Barry

There were a lot of black nylatron worms which were slightly over size and as they get hot they expand and jam.

It sounds if your installer (unwittingly) used one of these.

Open up the back, is the worm darkish grey in colour? If so, it's a nylatron single piece worm.

I suggest you contact your engineer immediately as it means a complete stripdown. It will either need a new worm or a "turn down" of the OD of the worm, and a corresponding reduction of the bottom of the groove.

Sorry to give you the bad news.

Posted by Richard C Patchett (Member # 974) on July 03, 2010, 09:21 PM:

Greetings
It may be installed backwards.I have seen this before.
on the 1695 which would cause binding.
RC

Posted by Josef Grassmann (Member # 378) on July 08, 2010, 08:40 AM:

Is there a bit clerance between teeth of worm gear to top and lower gear when warmed up? Is is more difficult to crank it by hand when warmed up?
Otherwise it could be that claw mechanism is tighten too much.

Every time worm gear is changed full service / inspection has to be carried out to ensure that projector runs smoothly.

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