RE: [CAD_CAM_EDM_DRO] looking for some gearheads

There pinion and worm drives like Jon says that have hydraulic loading where
the lash is controlled by a continuous preload applied by a hydraulic
piston.

I've never had one, only seen pictures in tech books, but the preload is
supposed to be very hi, much higher than spring loaded snubbers. They also
have a very fancy helical like gear profile rather than straight cut, I
believe the design was invented by the Churchhill grinder group and patented
many years ago along with their hydraulic adjusting grinder bearings,
certainly the two systems are often found in that area of some text books.

The coaxially split drives are more typical to find in old mining machines
with wheels several feet in diameter, I don't think they were for anti
backlash, more to reduce sideways bearing thrust.



Regs Mark



Dr. Mark Vaughan Ph'D. B.Eng. M0VAU

Managing Director

Vaughan Industries Ltd, reg in UK no 2561068

Water Care Technology Ltd, reg in UK no 4129351

Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH, UK.
Phone/Fax 44 1872 561288

RSGB DRM111(Cornwall)

_____

From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Jon Elson
Sent: 31 July 2007 02:57
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] looking for some gearheads



H & J Johnson wrote:

> David, after re-reading my previous reply I guess I did sound a bit

brisk.. I

> appologise if toes were stepped on..
>
> That being said, when someone is looking for these reducers
> to fit a 34 or 42 NEMA, or a 90 or 115mm motor frame.. chances are
> that they are looking for something to use in the drive side of a project
>
> I'd sure like to find a worm drive w/ 10 arc seconds
> of backlash.. I have a use for one, granted they are cheaper than
> the planetary reducers and harmonic drives I was going to buy. :-)

Some worm drives have an eccentric adjustment to vary the gear
engagement. If the worm wheel is well-centered, you can bring
the worm in almost to zero clearance. I did this on a very old
dividing head, but that is probably built to tighter tolerance
than a small gear reducer. There are also some worm drives that
have a coaxially-split worm. The two sections of the worm meet
right over the center of the worm wheel, so it is essentially
equivalent to an anti-backlash gear set. These can have
extremely small backlash.

Jon





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