Wheelchair access to a shower bench?

[Baluncore]

Surely this problem has been solved many times.

Yes it has.
But finding occasions of interference, during the manipulation of arbitrary 2D or 3D linked objects, through arbitrary 2D or 3D geometric passages, is not usually mathematically analytic, it is numerical and involves FEM with intrusion detection.

 

[berkeman]

I am doing a bathroom remodel and want to make sure it is handicap accessible, in case I become in need of a chair in the future. I am 81 and doing good so far but who knows.

In my EMS experience, nobody showers sitting in their wheelchair. They wheel into the shower and transfer to sit on the bench to shower, and push their wheelchair out of the waterstream path before turning on the water.

Okay, Barry please stop and take a deep breath. Whew.

Nobody showers sitting in their wheelchair, please trust me on this. I work in EMS and help folks with wheelchair disability issues all the time. So the question for you is really how to best design your new shower to accommodate future needs where you will maybe need to access the shower sitting in your wheelchair, and most comfortably transfer to the bench using handrails and push your wheelchair out of the shower so you can turn on the water stream.

So make your bench big and wide and make your handrails sturdy and make it easy to reach the shower door handle after you push your wheelchair just outside of the door.

More resources: https://www.abilities.com/

 

[DaveC426913]

I tried to reply to DaveC4259 and got an error msg saying the post was not available.?

Surely the one I deleted, having decided it had little to contribute.

 

[Lnewqban]

Any house modification of that nature should comply with the current Accessibility Building Code of your state, if located in USA.

Just for a guide on the basic dimmensions, please see that current code for Florida:
https://codes.iccsafe.org/content/FLAC2020P1/chapter-4-accessible-routes

 

[anorlunda]

Any house modification of that nature should comply with the current Accessibility Building Code of your state, if located in USA.

Just for a guide on the basic dimensions, please see that current code for Florida:
https://codes.iccsafe.org/content/FLAC2020P1/chapter-4-accessible-routes

That is the real answer. In the modern world, the calculations the OP seeks to do have been done in advance. Also, other considerations the OP didn't think of are included. The result is embodied in a code like the one @Lnewqban linked.

Failure to follow the codes can result in making your house uninsurable, or unable to be resold in the future.

 

[Tom.G]

2. Then, when completely in the space, you turn the remaining 45°.

If the shower stall is 36" x 72" as shown in the diagram, there is a noticable problem. The diagonal measure of the wheelchair is 48" so turning it around in the shower is not possible.

For a different approach look at:
https://m.media-amazon.com/images/I/31dT86eGSmL._AC_.jpg

Which is available at:
https://www.amazon.com/dp/B001KNNWYW/?tag=pfamazon01-20

Cheers,
Tom

 

[Baluncore]

The diagonal measure of the wheelchair is 48" so turning it around in the shower is not possible.

The chair is passing along a bent passage way. The rear RHS corner of the chair is in the doorway. It does not need to turn around. It comes out backwards.
The left-hand wall outside the entrance to the passage now precludes my original analysis.

 

[barryj]

I made a scale model of the situation. The chair will have to rotate as it enters the 36x72 space and it will do so. The cutout on the wall is not necessary it seems. While using a model works, I still do not have a precise answer of how deep the bench can be. Looks like 16 inches, maybe a bit longer. Tough problem.

 

[sophiecentaur]

It can with an ideal wheelchair. In particular, the location of the wheels would have to be on the very corners of the device and be of zero size. But that will have no bearing on any real scenario.

Wheelchairs come in a variety of sizes and skilled users can do all sorts of things with them but the OP will need to cater for all possibilities; self drive or 'pushed' could be required. To save a lot of hassle, it would probably be best to see what's available from suppliers and base a bespoke design on that.
The best way to approach this problem is probably not to spend too much initial time on calculations and geometry - pity but it's probably true. @anorlunda 's point about insurance and regulations is very relevant. You might find it worth while to approach the 'department of free advice' in the guise of a couple professional installers with records of good work.

Good luck with the project and congrats on being so forward thinking.

 

[barryj]

To be honest, getting the wheelchair into the shower was my first issue. Now we have a general problem of in this case how deep can a bench be if a piece of say plywood 25X42 inches had to be slid into the shower. Like I said, I made a model and using my fingers carefully slid the plywood into the shower. However, I still do not know how to calculate the precise distance the bench depth can be made. The plywood when entering the shower area must undergo a translation and rotation to get it in. Not sure how to calculate thie.

 

[Baluncore]

Not sure how to calculate thie.

I have been looking at a two-phase numerical solution.

Phase 1. The chair back left corner follows the left wall outside the shower, while the RHS slides along the door post on the right of the entry. During that progress, the front left corner of the chair traces a line on the floor.

Phase 2. The chair front left corner follows the back wall of the shower, while the RHS slides along the door post. During that progress, the rear left corner of the chair traces a line on the floor.

The two lines on the floor mark the boundary of the area needed by the chair, outside which can be the shelf.

 

[barryj]

I think this plan will work. So as the bottom left corner moves up the read shower wall, the perpendicular
distance between the shower top left corner and the chair edge must be calculated. Once a closed form expression is obtained the distance can be calculated using differentiation. Or something like this...

 

[Baluncore]

Once a closed form expression is obtained the distance can be calculated using differentiation. Or something like this...

Not mathematically continuous, but numerically in many small discrete steps.

 

[barryj]

Not sure I agree with you. During phase 1, as the corner moves up against the back wall, I bet you could calculate the distance as a function of x, the distance the corner moved.. I will try sometime today.

 

[Baluncore]

During phase 1, as the corner moves up against the back wall, ...

"The corner" is meaningless, there are four of them. Which corner, FL, FR, BL, BR.

The FL does not reach the back wall of the shower during phase 1, because there is sufficient space to turn through 90 degrees. That is why there must be two phases. The functions are not continuous, but each has two bounds, beyond which each analysis fails.

It would be easier to hang a shower curtain than build a wall.

 

[Baluncore]

Notice that both the opening and the shower stall are 36" wide.
The problem is numerically symmetrical about the diagonal axis.

 

[Baluncore]

I have a messy solution that gives the locus of the front left corner of the chair as it enters the space. The back left corner of the chair follows the wall on the left. The RHS of the chair slides on the door post. The yellow locus assumes a full 90° turn, with no shelf to obstruct the back left corner.
Phase 1 ends when the chair has moved and rotated to 45°, it slides forward, parallel with the shelf until the front left corner hits the back wall. That is where phase 2 begins.

The magenta line is the maximum shelf size, 33" along each wall.

 

[barryj]

I agree with your calculations. I did a simulation using a cutout of the shower footprint and moving it as you did and get the same plot. The dots agree with your calculation. So it seems I can have a 19 inch bench. Good!.