Articulating Ramp

[dilitteral]

I am looking for a design to create my own articulating gangway. Does anyone have any?

[gonzo]

They are use specific. That is, they are designed to satisfy the particular requirements of the application. Also, if it is for commercial use there are other regulations to comply with.

[dilitteral]

I live on a lake that has fluctuating water levels and would like to have a ramp that will change into stairs as the water level drops. This is a residential use property. However, I do not know how to design the articulating stairs.

[Lurvio]

Should not be that hard, You need cheek planks (thats what their called here) that support the weight. In normat stair the steps are fixed to the cheeks, you need every step to have a pivot point only. Then you need an arm that has enough strenght to keep the step level in all conditions (preferably two - one on each side) and connector rod parallel to the cheek planks that connects the steps to each other and to a solid landbased anchor point.

You have to make sure the steps can move freely through the whole range of motion without touching each other.

how much difference between max. and min. water level? I think the maximum angle of the cheek plank in min. waterlevel should not exceed 30 degrees.

Lurvio

[CDK]

You mean something like this?

This is just a crude sketch: success or failure depends on the geometry. All tie bars have equal length except the one between the gangway and the fixed column on the jetty.

[gonzo]

If it is residential, you need to check local codes. For example, http://www.woodsthebest.com/Stairs/building-codeUS.htm
If it a rental unit, the restrictions may be stricter. Also, you will have to comply with ADA.

[Lurvio]

CDK
That is exactly what i mean. I thought about the connecting rod being below, but your version makes a lot of sense as there is something to attach the handrails to. The anchor point needs to have same geometry as the steps, so that would have to be moved above the pivotpoint in the sketch.

Building code usually (at least around here) gives minimum measurement for handrail height and possibly width and lenght of the step. And maximum measurement for step height.

If the gangway/stair structure is the only thing keeping the pier in place against wind etc, it has to have pretty strong construction.

Lurvio

[dilitteral]

Hi, Gonzo and Lurvio. Yes, exactly what I am thinking about. What would you suggest for the connecting material that makes the step move or remain stationary?

[murdomack]

Why don't you just have a simple gangway with treads about 2" square like ships use. It will be a lot more secure than all these swivel pins. You need firm foot contact on a gangway, it's like being on a ladder, always having three points of contact.

[Lurvio]

dilitteral

First we'd have to know what forces are in play here. There is a vast difference between a five square meter dock at a small inland lake and a 50 square meter dock/partydeck by the ocean.

Deck size, information of the area and waterlevel range for instance.

Lurvio

[dilitteral]

Hi. I love the design, it looks exactly like what I was thinking about. The lake is a relatively small lake that is flooded periodically (summer time) from the Tennessee Valley Authority. The water levels can change from around 10 feet or better from low to full pool. The landscape is steep and wanted to have steps in order to secure footing and an ability to continue to access the dock. The dock itself is a floating dock that is approximately 12 feet wide by 16 feet long, with a drive on boat dock in the center. Therefore, I need to ensure stability for movement also due to the drive on feature of the dock and the weight/movement of the boat driving onto the dock. Thank you for all the help, everyone. It is greatly appreciated.

[CDK]

Because it is a lake, aluminum would be a good construction material. Stainless bolts and nylon bushings for the swivel points, a concrete slab on the shore to make sure the gangway stays in place and a sign saying that using the stairs/gangway is at your own risk.

I've seen floating docks on the Channel Islands, where the tide exceeds 35 ft. They use simple vertical ladders to access the docks but usually wait for high tide to avoid the long climb.