2 Post lift control box

[Josho]

First off I hope I am posting in the right section.

Second, I have a 2 post lift that I am having issues with. The control board was damaged and we ordered one in. It is a German lift, not THAT old but not sold anymore. The company got what they thought was the correct board in and we fitted it.

All was okay til the lift went out of sync. There is a reset proceedure involving both up and down buttons (which are low voltage). A massive bang happened and the breaker went.

What has happened is the original board had a physical interlock on the reverse contactor. The replacement doesn't, I think it has an electrical one.

Anyway both relays inside the reverse contactor have managed to fire at the same time resulting in the bang.

I'm a bit sick of buying incorrect £600 boards so thinking of making my own.

See the diagram. The only issues I can see is the board syncronised the lifts for you, i.e if one slowed down a little because the car was slightly off center it would stop one lift momentarily and balance it.

So I have added a normaly closed switch to motor 2 so we can do that ourselves.

Seems a shame to get rid of the lift as it came from a commercial VW dealer and it will cost £10k to get one that is this solid. We can get a Smart Car or a LWB Luton Sprinter on and the legs are so heavy duty it doesn't wobble with the heavy stuff on.

Thanks for your thoughts.

 

[Adam_151]

Unfortunatly it gets messy, you are into teritary covered by the machinery directive, LOLLER, PUWER, etc and are modifying a machine that you are using in commerial environment. Plus it looks like your replacement controls could still energise directions and short out phases anyway.

Is it not possible to look at repairing the original board? then providing you change like for like you are not modifying the original design

 

[bernardgreen]

Adam's advice is very important, you or whoever works on the lift has legal obligations and can be held liable for any damage, injury or death caused by modification carried out by an untrained / ignorant / incompetent person.

Using a change over switch for the Down button is a better ( safer ) way to select up or down motion as it prevents both UP and DOWN contactors being energised at the same time,,

 

[ericmark]

I have to agree with @Adam_151 I worked where we had tower cranes, I could see ways to improve them, however to do so I had to write to the manufacturers with the suggestion, and they needed to write back to me and tell me to do the alterations. This as you may expect was rare.

The problem is when the unexpected happens, this did happen with the tower cranes, being powered from a generator, the inverter for one motor managed to inject the supply causing the frequency meter to show 100 Hz and the main winch motor to fail to engage the brake. Lucky no one injured, but my point is I would have never foreseen that fault.

It seems strange that there is not some sensor or other device to ensure the two motors run at the same speed, or at least some cross wiring in some way so if one motor stops, both stop. The whole idea of being able to stop just one motor seems flawed.

Also having two independent reversing contactors, one would have thought they would both be powered together so one contactor not closing can't run just one motor. The whole set up seems Heath Robinson.

However the

It is a German lift

is a bit of a give away, my accident was caused by a German export not complying with safety regulations, it seems it did not even comply with German regulations, but since being exported, it did not have to comply, seems they even before we left the EU could sell non compliant stuff to the UK.

 

[flameport]

So I have added a normaly closed switch to motor 2 so we can do that ourselves.

That is not an acceptable use case. Someone will get it wrong, or the switch will stick and the result will be a 2 ton vehicle falling to the floor.
The diagram as posted cannot be used either for the same reason - individual limit switches which only interrupt one motor will at some point result in one motor operating on it's own.

it will cost £10k to get one that is this solid

How much does it cost to replace a destroyed vehicle, or pay for lifetime care for the person who is crushed underneath it?

 

[Josho]

Apologies, the diagram is slightly drawn wrong, I was thinking of a toggle switch up and down so it can't be pressed together.

Originally the board had one reversing contactor and two seperate contractors.

When one went out of sync it would drop one contactor so the other one would catch up.

A lot of 2 posts ramps have no synchronisation other than when right at the top or right at the bottom.

Bottom is better I suppose as if anything does go wrong the car is on the floor.

Thank you for your views.

The original board is quite heavily burned.

As said it was probably a bit of a freak condition pushing up and down at the same time and although it should never fire both contactors I think it just delayed. The original board having a physical stop it wasn't able to ever happen.


The lifts have to be inspected for LOLLER every 6 months.


We have had a lift once that stuck randomly going down but fortunately the operator just switched the emergency switch off (which on these ramps is at the control box).

It's one of them, what COULD go wrong when to be fair any of the lifts being hydraulic or not could snap a cable etc at any time.


I will make another call to try and get the correct board.....

 

[SpecialK]

Get the same board and electrically interlock the up and down buttons?

 

[SUNRAY]

Deleted to correct reply

 

[SUNRAY]

As much as I hate to say this:
This question does not belong in this DIY forum.


Get someone in who can design a system for you and carries millions of pounds of appropriate third party liability insurance.

I no longer carry such insurance and therefore unable to help.


The fact you ate using inappropriate terms indicates to me you may not be the person for this job.
If I'm wrong I apologise but this can be a very dangerous machine.

 

[Josho]

Thanks for the replies lads.

I will say I'd definitely do it if it was just me using it but on reflection and after some of your comments we've ordered a new lift.

Not the same and I bet it is nowehere near as sturdy but it's officially safe.