[modeleng] Re: are ye all trying to tell me something...

Hi Peter

All worms are reversible, but, as you say, they are very inefficient in 
reverse.  Lifts (elevators) are often driven by worm boxes, but if the brake 
is released without the motor being powered, the lift is quite capable of 
running away under gravity by back-driving through the worm.  Hence the need 
for a safety brake.  (For information, lifts are normally counterbalanced at 
50-60% of passenger load so at any time either the car or counterweight is 
likely to be heavier).

Regards
Ron (who's had a bit to do with lifts in his career)

----- Original Message ----- 
From: <peter.chadwick@xxxxxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Sent: Sunday, November 19, 2006 9:59 AM
Subject: [modeleng] Re: are ye all trying to tell me something...


>I believe that you can reverse drive a worm under certain circumstances.
> From memory, you must have a very 'fast' worm i.e a big pitch, and the
> correct angles of the worm and the gear. It will then reverse drive but is
> horribly inefficient, and is of little (if any) practical use.
> Peter Chadwick
> Swindon
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