Synchronization of hydraulic pistons

[lakmalp]

Hi,

I am planning to build a garage to park my two cars. Since I don't have much space for two vehicles, I am planning to build an underground car parking system with two levels.

For this, I need 4 synchronized cylinders for 4 corners. Load will be approx. 6000 lbs.

Can anyone of you please help me figure out how can I synchronize these 4 cylinders?

Regards,
/Lakmal

 

[triden]

I know a lot of hydraulic car hoists have 1 main piston that pulls on 4 cables to each of the posts. This way each side is certain to lift at the same rate.

Are you planning to lower the platform as a single table? If so you can do what elevators do and have one central ram that lifts from the ground and pushes upwards.

 

[lakmalp]

Thanks for the idea triden. It will be lot easier than maintaining 4 cylinders. Are there any other advantages/disadvantages in this method compared to 4 cylinder option?

 

[lakmalp]

Here is what I mean to build. Brown area is earth.

 

[confused slug]

You could consider using gear type flow dividers to divide the oil flow equally. There would be minimal oil flow across the divider which would be a problem if the loads on each cylinder was not equal. You would also need to incorporate double overcentre valves as a safety measure should a hose or ram seal fail or pilot operated check valves on the cylider ports. I would recommend using amoured hoses, something like R9R or Gates M6K spec. I have used such systems to control the folding functions on large machinery which would over balance and fall over if one side lifted before the other. Need to consider what would happen if one ram failed or was prevented from functioning due to a mechanical problem.
Keeping 4 cylinders phased is not easy, if electorics are your thing then one way may be to use cylinders with integral LVDTs or similar positional sensors linked to presure compensated flow control valves on each ram and a box of tricks to control the valves. In an application like this i would go for 1 ram and a mechanical linkage / wire ropes to eliminate the problems.

 

[lakmalp]

Having read the responses, I think I should go with 1 ram/ropes option. I think that is what "confused slug" also suggesting.

 

[Ranger Mike]

http://www.affordableautomotiveequip.net/car-lifts.php

 

[Travis_King]

Your load would be a lot more than 6000 lb most likely. You will need a solid platform, which means lots of structural steel. What floor will you be using for the top layer? Material for that will add weight. Factor of safey for all of this (15-20% unless you don't like your vehicles )

Then you've got to think about footings for these rams to support their respective loads. Buckling of the ram rods while you are lifting the platform 5-7 feet will become a problem as well.

Is this really worth it?

 

[lakmalp]

@Travis_King: Yes. Total load would be ~7500 lbs. If I can use counterweights (like in an elevator)? So the load on the ram would be lot lesser.

 

[Travis_King]

Here's an idea for you to consider:

Two level static garage. Hydraulic/elevator ramp that allows access to the bottom floor. Obviously you will have to do some more with drainage for rain and such so the bottom level (particularly the ram components) doesn't get flooded. But if you have the room for it, this would be a much safer and (relatively speaking) easier job. Have you checked building codes in your area? Do they allow for the necessary escavation? Do they allow this sort of "floating floor" system you are considering?

 

[lakmalp]

Two level static garage.

Sorry, I couldn't get you.

This is what I meant:
http://www.aegarageequipment.co.uk/phantom-park1.jpg" with added counterweights.

 

[Travis_King]

Yea, so if you are going to escavate that lower level anyway, why not save yourself some hastle and escavate a ramp with a cut out for your hydraulics. This way your only moving parts is the ramp which only has to support a vehicle while you are driving in and out of the two spots, and really only when you are driving into and out of the top spot, since you would likely have some support when the ramp was lowered into the lower section..

It's just some food for thought. Something like this (unless you buy a turn-key system) involves a LOT of planning and money. The real question is, is it worth it.

Also, again, have you considered your local building codes?

 

[Mech_Engineer]

You will definitely be better off buying a semi-custom unit which is properly engineered for this sort of application- there are several companies which specialize in this field. I get the sneaking suspicion that you don't have any heavy equipment design experience... so instead take for example these guys which make EXACTLY what you're trying to make yourself:

http://www.aclifts.com/parking/pss-7/

 

[Enthalpy]

Four ballscrews look stiffer and more reliable than cables.
You can turn them from a single motor-gear and four shafts.

It's done to move a nozzle extension at recent rocket engines, like the RL10B and the Vinci. Very elegant solution to a very difficult task.

 

[lakmalp]

You can turn them from a single motor-gear and four shafts.

@Enthalpy:
You mean: use electric motor instead of hydraulics?

 

[Travis_King]

I would follow the link mechanical engineer posted. For the amount of time and money you'll spend doing this yourself, you will still likely end up with a system which is less safe and less effective as the turn key ones. Its not saying anything about you, its just that when it comes to heavy equipment systems like this, it is better to go with a tried and tested design by people who focus on that specific application.

 

[lakmalp]

Thank you all for your valuable inputs. It seems I am not the one who should take up this job. :)

Thank you all again!

 

[Travis_King]

Yea. I mean I don't want to discourage you from building things and testing yourself, but sometimes it isn't worth it