The passenger seat needed to swivel 90 degrees or 180 degrees.  90 to use the seat for reading with feet on the driver's seat and 180 to face the fold up table mounted on the side of the side of the sink cabinet.  The fold up table can be used for eating or computer usage.  No need for the driver's seat to swivel because the shower enclosure wall is directly behind the driver seat.

Could have bought a swivel for about $330 plus shipping and handling.  Probably should have done that.  Lots of design time and a redesign to fix what did not work.  Cost ended up about the same.  Parts weigh 42 lbs.  Ended up with a swivel that works very well and can be turned without hitting the passenger door.  Shaft is centered between the seat mounting holes.

My van does not have power seats or rear air or seat airbags so there was no wiring or anything else under the seat except for the jack and jack mount.  Removed the jack and jack mount.  A vertical 1 1/4" SS shaft was installed in two four bolt flange bearings.  A framework was made that sits on the seat base to support the two bearings and is bolted to the seat base with the original 8mm seat mounting bolts.  A 1/4" SS plate was bolted to the bottom of the seat with 5/16-18NC x 3/4" hex head bolts and elastic stop nuts using the stock seat mounting holes.

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Did not want to weld, machine or paint any of the parts.  A 1/4" SS plate is used to bolt the bearings back to back. The 1/4" x 8" SS bearing plate is part of the framework that bolts to the seat base.  Used two SS split shaft collars below the bottom bearing and one above the top bearing.  The seat plate has a 40BTL 36 tooth sprocket bolted to the plate.  The seat plate is installed on the shaft with a 1610 taperlock bushing.  Seat turns easily.  Seat is raised less than 1 1/4" and could have been less if I had used flathead screws.

The 1/4" SS seat base and seat plates were cut with a waterjet.  A .dxf CAD drawing was sent to the shop to get the parts cut out.  The seat base framework is made with two plates and 80/20 aluminum extrusions and bolted together.
The latching mechanism is where the difficulties were encountered.  What I designed looked good on the computer but did not work in the real world.  Too much slop in the design to hold the seat stationary.  What I thought was a clever design was not.  Ended up using a wood stick against the two plates to prevent rotation.  Remove the stick and rotate the seat and then replace the stick.  Seat at 90 degrees is not locked in position.

Swivel was not crash tested (no plans to do that).  It is not certified by anyone so the results that would occur are unknown.  No calculations were done to determine the safety of the design.  If someone wants to use the design they need to be aware of the risks.  If you want a swivel that has been tested,  then buy a swivel from a commercial supplier.  THIS SWIVEL MAY FAIL IN A CRASH.

 

Passenger Seat Swivel Drawing # ODJ127-60                                    

If you want more PDF menu choices the drawing can be saved to your computer and then reopened with Adobe PDF Reader.  The Adobe PDF Reader is a better program to use for viewing.