stevebubs
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| posted on 19/6/10 at 07:28 PM |
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Mysterious 2 Ton Lift
One of my mates bought a 2ton 2 post lift a couple of years ago, and finally got round to installing it into his double garage.
However, he hasn't got a clue as to what the make/model is...can anyone help?
Pics are here << Clicky
If anyone can help identify the make/model or even just the power of the motor, it would be much appreciated...
[Edited on 19/6/10 by stevebubs]
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t16turbotone
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| posted on 19/6/10 at 07:59 PM |
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Hi, well for a start its a 3 phase motor, overloads are set to 5 amps per phase, so at a guess its 2.2kw, speed looks like a 4 pole so 1420 rpm.
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SteveWalker
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| posted on 19/6/10 at 08:10 PM |
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I can't help with the lift itself, but the motor will be 415V 50Hz 3-phase, the starter is for direct-on-line (DOL) starting (he could use a
star-delta starter to reduce startup current if needed). The thermal overload in the starter appears to be set around 5.25A, therefore maximum power
is around 3kW assuming a power factor of 0.8.
W=V*I*SQRT(3)*pf for 3-phase.
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stevebubs
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| posted on 19/6/10 at 08:36 PM |
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Looks like the lift may have been blue before it's yellow paint...if that helps...
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stevebubs
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| posted on 19/6/10 at 08:37 PM |
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any pointers to a single phase equivalent motor?
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johhny5
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| posted on 19/6/10 at 08:53 PM |
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At a quick look it could be Bradbury or possiably an OMC.
Problem with ramps is that somebody makes them and then everybody buys them and re badges them, re spays and re names them.
I am an engineering surveyor for a insurance company so see many types.
Is there not a spec plate on one of the legs?
If this ramp is installed in comercial workshop the arms should lock at 100 mm from the ground, it the law from 2007 Jan.
If you need more help U2U me, i can advise on inspection etc, just to be safe.
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stevebubs
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| posted on 19/6/10 at 09:06 PM |
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quote:
Originally posted by johhny5
If this ramp is installed in comercial workshop the arms should lock at 100 mm from the ground, it the law from 2007 Jan.
Nope - is in his private garage. Purely for personal use.
quote:
If you need more help U2U me, i can advise on inspection etc, just to be safe.
Ta
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britishtrident
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| posted on 20/6/10 at 12:16 PM |
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Never seen the that model but the engineering loks Bradbury ---
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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Fury9R
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| posted on 20/6/10 at 04:56 PM |
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Hi Folks,
I'm the one with the mysterious lift. Thanks Steve for posting this, and thanks to all for the helpful replies. So I figured I should finally
pull my finger out and register myself. Although I am not actually building a locost (yet) 
Since I installed the ramp a few weeks ago, I have just been using an electric drill + homemade attachment to drive the hydraulic pump, but this is
far from ideal (it makes my drill smoke when lifting my -nearly 2 ton- 5 series  ) not to mention the fact rather "cowboyish" and likely
to cause an injury so am looking for options to get it working properly.
I expect getting the power company to provide 3 phase supply to my house will be prohibitavely expensive. So options are:
1) Buy an equivalent single phase motor.
2) Buy a (digital?) Phase converter.
3) Buy a 3 phase generator.
All of these come in at around £200 (ebay) for 3hp - as Steve mentioned, this is for non commercial use so I doubt I'll be doing on average more
than 1 raise lower cycle per week therefore 1000+ cycle reliability not a key issue. Likewise speed to raise the lift is not vital.
Irrespective of the option I choose I believe I need to determine the power rating of the existing motor in order to spec the solution but
unfortunately the rating plate on the motor has been removed for some unknown reason. By my calculations a 3hp (2.2 kW) motor should lift the max
rated 2 tons to a height of 6 foot in about 16 seconds (not counting the weight of the arms and other moving parts of the mechanism), a 1 hp motor
would take 48 seconds and a 2 hp motor would take just over 30 seconds.
As mentioned previously speed of raising the ramp is not key deciding factor in my choice of power rating but total cost and getting something that
will work is!
At the moment I favour the phase converter as (I presume) I should be able to use it for any other 3 phase equipment I might get in the future (as
this is just in my garage I have no need nor intention to run more than one 3 phase piece of equipment at any one time).
Although the genny option has the advantage of also supplying standard 240v single phase and being portable (ish) the thought enclosed garage and
carbon monoxide poisoning does not appeal, neither does angry neighbours, recoil starting every time I want to raise the lift etc.
I remember reading that single phase motors don't really work for car ramps. IIRC, no details were given why this is the case or whether this
applied to hydraulic and/or mechanical (screw) type lifts, but it was on the website of someone who was selling single phase motors and (strangely
enough) phase converters ;-)
As can be seen from the pictures it's currently Delta wired. Disconnecting one of these delta connections showed a resistance of 24 ohms across
all three phases of the stator windings (8 ohms each).
If I understand what I have read on various websites correctly, this means that it is suitable to be driven by a 240V single phase -> three phase
converter without the need to provide a step up 415V output.
So my questions are.
Is my thinking sound regarding using a Digital Phase Converter?
Any gotcha I need to look out for with this approach?
I presume that the hydraulic pump will have a minimum torque requirement to raise a 2 ton car and therefore for any given speed (RPM) would require
the motor to output a minimum power proportional to that speed in order to raise the lift, And if the motor is unable to provide that torque then it
will simply fail to turn and burn out, so using a lower power motor than the one currently being used is not an option?
Could I use a lower power Phase converter (say 1 or 2 hp) and run the motor at a slower speed (say 25% or 50%) which would raise the ramp slower but
also require less power?
Would I be better going for a single phase motor in spite of the warning as I am anticipating relatively few duty cycles?
Not wanting to contradict SteveW as I know so very little about this mysterious world of 3 phase electrics, but, is it true that the delta
configuration implies that the this is actually 240V three phase, which would give a power rating much lower than the quoted 3kW?
Many thanks for all the valuable input.
Sean
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MikeRJ
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| posted on 21/6/10 at 02:26 PM |
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Single phase motors tend to have lower starting torque than three phase.
A suitably rated inverter is certainly going to be
the easiest overall solution.
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skinned knuckles
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| posted on 21/6/10 at 04:34 PM |
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my head hurts!
A man isn't complete until he's married, then he's finished
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SteveWalker
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| posted on 21/6/10 at 05:37 PM |
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quote:
Originally posted by Fury9R
Not wanting to contradict SteveW as I know so very little about this mysterious world of 3 phase electrics, but, is it true that the delta
configuration implies that the this is actually 240V three phase, which would give a power rating much lower than the quoted 3kW?
The standard 3-phase supply (as will be in the street outside your house) is 415V (measured phase to phase) and hence 415V across the windings on a
delta wired motor. If the motor is instead wired for star, then one end of each phase is connected together (this should be floating at 0V) and the
measurement between phase and the star point should be 240V - this is indeed how the 240V single phase to your house is derived ... typically every
third house in the road will be connected to the same phase and the star point will be earthed to keep it at 0V if there is a fault or an unbalaced
load.
In star the calculation will instead be W=3*V*I*pf (which works out at the same 3kW).
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Fury9R
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| posted on 22/6/10 at 03:46 PM |
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Steve, thanks for the clarification. Makes a bit more sense in my (uneducated) mind now.
So is it correct that if I were to use a single phase 240V input to 3 phase 240V output digital phase converter, then the motor would need to be star
wired to work properly (with 240v)?
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SteveWalker
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| posted on 22/6/10 at 08:15 PM |
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No. When you are running the motor in Delta there is 415V across each winding, while in star there is only 240V, the motor will be running on too low
a voltage and will likely not come up to running speed and will probably overheat.
The motor you have got is for 415V Delta, the star configuration is purely to lower the voltage across each winding and hence lower the inrush current
for starting (you could be looking at 50A or so for a moment). Normally when this configuration is used, there is a timer (maybe 5 seconds or so) to
automatically switch to delta and prevent continued running in star. To run your motor continually in star, you'd need a 720V supply!
What you need is a proper inverter, giving 3ph 415V output, but you'd probably find it much cheaper to change the motor!
[Edited on 22/6/10 by SteveWalker]
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