Hi,
I have a problem with a stage at a school that currently runs a hydraulic powerpack and 4 cylinders. One to each corner of the stage. It spans 18metres x 5 metres wide. The stage has a travel of 1800mm so can be used as a orchestra pit drops down 900mm and lifts to stage height. This operation is slow and the level of the stage gets out of synchronization every cycle. Looking at repairing the hydraulic circuit and also fitting a switch in place to stop each cylinder, or level the stage up once out of sync. Currently the stage is operated by maintenance personnel but they would like the option of numerous people. It uses a 12V solenoid system to open the valves in either direction and can individually operate each cylinder.
Hi Joshua
Sounds like you have an uneven fluid supply to the cylinders. Assuming the system operated correctly at one time it may be time for a complete clean out and overhaul by some hydraulic engineering people.
I feel anything you might try or do to correct this will only be a “Band Aid” solution and will not fix the core problem. The fitting of “limit switches” in an attempt to level up the stage is only going to involve more stops and / or control valves and generally complicate the issue without fixing anything.
There may be other issues here which will prove me completely wrong but one can only comment on the information available.
Cheers Bob
Definitely some bugs in the system. I actually worked for a hydraulics engineering firm part-time while I was doing my degree. If you’re at all unsure of working with hydraulics, I’d 100% call in an expert.
Hydraulics are very dangerous - especially because they look so innocent with their quiet slow motion. (Hydraulic) fluid injection injuries are a very real risk (only google this if you’ve got a strong stomach), and commonly result in massive surgery or amputation despite a seemingly tiny entry wound.
Also, anything strong enough to lift an entire orchestra will be capable of cutting a person in half without even a hiccup - if it were me, I’d be 100% restricting who can operate that stage to a very small group of highly trained people. The only way around it would be a few hundred thousand (or $1M+) in engineering costs to implement some complex automatic safety systems - and then you’d need to find an engineer willing to stick their neck out and risk gaol time to sign it off as safe.
Oh, and this is lifting people of course. A failure = falling platform. Falling platform = 1.8m drop = severe spinal injuries for anyone on it, and/or death for anyone underneath it. This piece of equipment is a safety nightmare, and would need to be regularly inspected by an engineer under AS1418 anyway. Calling in a professional on this one isn’t really optional - it’s a legal requirement.
Safety aside, operating hydraulic cylinders synchronously is a very common requirement and the basic circuits to do it are well established. I’d strongly recommend a call to a custom fluid power place even if there weren’t safety issues - in my experience hydraulics are one of those things that seems expensive to have done by a professional and cheap to DIY, but is actually cheap to have done professionally and very expensive to DIY once you know the full story (particularly once you account for the special tools and equipment needed, as well as all the training and specialist knowledge you need).
For educational purposes though, these are pretty good videos:
Thanks for posting on the forum! I believe I spoke with you on the phone about this one.
I had no idea that this was the scale you were working with! I agree with Oliver and Bob on this one, it seems like a bit of a patch if it originally raised evenly.
My patch was going to be distance sensors pointed at the gap between the stage and ground or something like that i.e.
However, that sensor board was only meant to connect at small distances, you might need a microcontroller that is measuring from it, and sending that data over a better medium like RS485 or OneWire
I can go more in-depth on this one, but it seems like the consensus is to treat the cause, not the symptom.
Do yourself a favour and seek help from qualified professional hydraulic personal.
As this is a known fault, just continuing to operate the equipment could lead to severe legal ramifications if anyone is injured. Safety is the first consideration in any case like this, legally it is duty of care.
It may be costly to get a professional but it pales compared to the legal duty of care.
I guess that is what I was trying to say. Hence my reference to Band Aids.
Unfortunately all too often it is the reverse that seems to happen.
Cheers Bob
