Re: adjustable car ramp


"Dave Plowman (News)" <dave@xxxxxxxxxxxxxxx> wrote in message
news:4f0db58f6adave@xxxxxxxxxxxxxxxxxx
In article <op.twljs9d1yuobwl@xxxxxxxxxxxxxxxxxxx>,
Duncan Wood <newsto@xxxxxxxxxxxx> wrote:
Anything that uses a screw that can't turn by itself (ball screws
aren't used for this reason), does not need a secondary locking
system. And before you try arguing, at work there are three different
two post lifts (two are 3tonne rated, the other 5tonne rated) that
use screws, along with a four post lift rated at 18tonne, all of
which use screws with no secondary locking device.


Are you sure they're not driven by a braked motor?

You'd need a *very* coarse screw thread to be reversible.

That's the exact principle they rely on. Certainly all the two posters have
no form of braking, but the motors are highly geared via belts, which helps
increase resistance to the screw self running (the screws spin, and the nuts
are stationary).
Having had to lower one manually, they're not going to self-run!
The big four poster isn't braked, but again each motor is geared through a
gearbox (going by the shape/location of the gearbox, I'd suspect they're
epicyclic gearing, rather than a wormwheel and screw)

And getting back on topic, a brake on the screw/nut/drive system is not a
secondary locking device.


.

Relevant Pages

  • Re: adjustable car ramp
    ... > which use screws with no secondary locking device. ... gearbox (going by the shape/location of the gearbox, ... Although if they're connected by belts braking the motor woukd be pretty pointless ...
    (uk.rec.cars.maintenance)
  • Re: adjustable car ramp
    ... And before you try arguing, at work there are three different ... two post lifts ... which use screws with no secondary locking device. ...
    (uk.rec.cars.maintenance)
  • Re: Refurbish cassette deck motor
    ... Such motors usually employ a mechanical speed regulation ... Not sure if it has screws beneath the case tape. ... It's swaged together, making repair all but impossible (you can't get to the thrust bearing, without ripping the thing apart). ... My cost price is about 8 Bucks. ...
    (uk.rec.audio)
  • Re: Ball Screws in Bridgeport mill?
    ... I would save the ballscrews until you run across some stepper ... or servo motors, and then install the screws and motors. ... would be heading is to have a machine that can run manually or CNC. ...
    (rec.crafts.metalworking)
  • Re: Refurbish cassette deck motor
    ... Such motors usually employ a mechanical speed regulation ... electronic speed regulation systems and are almost impossible to repair, ... Not sure if it has screws beneath the case tape. ...
    (uk.rec.audio)