Thursday, August 12, 2021

Installing the Raymarine Rudder Position Sensor

Installing the Raymarine Autopilot Rudder Sensor (RPS)

This starts off techy, but read it to the end.



As mentioned in the previous post, the plan is to mount the RPS on the underside of the Aft Locker Shelf Support Beam. 


The RPS arm must be parallel to the Steering Radial Drive Radius when the rudder is amidships. There is a small amount of adjustment of the sensor (it has 3 extended slots in it's mounting base)




Schematic of RPS
Connection to the Steering Radial Drive


The vertical alignment of the RPS and the Tiller Pin has to be within +/- 5º Max. I'll make several Starboard Mounting plates of different thicknesses and use those that are needed to get the alignment within tolerance. I have several thicknesses of Starboard, so this should be easy. 

Well that first layout didn't work. The vertical alignment of the Tiller Pin would move everything down too low on the Steering Radial Drive - there would be huge chunk of starboard on the underside in order to clear the ridges.

Second design: Duh, looks a lot simpler.
This pic shows the underside of the Steering Radial Drive, that hole with the cable poking through is the problem for the 1st design.

Duh - Just make a bracket that can be held in place using the Thru bolt (center of the 5 in the pic) 

Basically an L shaped bracket made from 2" x 1/4" Aluminium Bar and mount the Tiller pin near the end of that bracket. There's a flat surface behind the head of that center bolt, so the bracket should be solid enough. I'll add a few brazed shims to the bracket if needed to ensure it's soli





Schematic of Tiller Pin and Support Bracket

Down at the boat again this morning with a makeshift Tiller Pin Support Bracket, just to figure out the size of the RPS mounting plate. We'll also check the max Rudder Angle, it has to be less than 60º from Center to Port and Starboard. The pic above shows the dimensions


To make the Bracket, I purchased a 24" piece of 2" x 1/8" Aluminium Bar Stock from Lowes. Marked the bar about 6" from the end. With the bar held in an Oven Gloved hand, and a plumbers Butane heat gun in the other, I heated the bend mark for 5 minutes. Then set the hot bar between a couple of garden stepping stones and bent the bar to shape. After cutting the bar to size, drilled the end hole and the Tiller mounting pin holes. Aluminium nuts and bolts hold the Tiller Pin in place, Loctite to keep them there. 

I added the two SS screws and lock nuts to add stability to where the plate is attached to the casting on the bottom of the steering radial drive. Plan is to attach the bracket using the center rudder post bolt, then tighten up on the two stabilizing screws and lock them in place with the lock nuts.




In addition to the Tiller Pin Bracket, I need to make a shim on which to mount the RPS and then mount it under the Port Side Shelf support beam.
1/4" thick Support shim 
I made 2, the other is 3/8" thick


The Install process will be:
  • Remove the Thru Bolt which prevents the Steering Radial Drive from rotating on the Ruder Post.
  • Install the new Tiller Pin Bracket on the bolt and reinsert the Bolt and secure in place.
  • Mount the RPS on the new Shim.
  • Align the shim so that the Pin on the RPS and the Tiller Pin are aligned and the RPS arm, Tiller Pin mount form a Parallelogram.
  • Run the Connector wire from the RPS forwards over the Aft Water tank and then join the loom of wires that reach the APU.

With everything prepped, I just need to get down to the boat early enough to be the heat or late enough for it to have started cooling down. Currently, the daily noonday temp is typically in the high 90ºF :(

Anticipating that I should be able to complete the RPS install in just one more trip to the boat, I'll hold off publishing this post until then.   Tuesday August 10th 2021

Update:  Thursday August 12 2021
Well, after getting all of that prep done, we took a break on Tuesday to get our Vaccinations - not Covid, we did that back in January, no, on Tuesday we got our Shingles Vaccine - shot #1 no biggy. Well, no biggy till Wednesday morning. Couldn't sleep all night and woke up unable to lift my left arm. Ibuprofen did not dull the pain! Wow, it gave me a little insight to what people suffer when they lose control of a limb. So Wednesday was a write off, I was able to steer my electric lawn mower, but very tenderly. So I mowed the lawn single handed.

Thursday almost 100% back in action. Lifting my elbow as high as my shoulder was slightly painful, but I felt I could make progress on this project.

We were down the boat by 10am and quickly got to work. 

Step 1 was to remove the center bolt. This pic shows the two shelf support braces on either side of the Steering Radial Drive. Removing the bolt took some doing, over 1/2 Hour to get it out, glad I'm a skinny guy.  That small USB powered rechargeable battery fan helped me keep my cool.

The bolt was a really tight fit through the rudder post, it needed a little persuasion but there's no room to swing a cat, barely room to tap the bolt with a hammer (of course I had a nut on the end so that the thread was not damaged.)

With the bolt out I took a break. The plan was to divide the job into steps. Step 1 done, got the bolt out.

Step 2  fit the Tiller Pin Bracket.  Step 3 install the Rudder Position Sensor with it's mounting plate. Step 4 fit the connecting stud between the Tiller Pin and the RPS pin.



After sweating for another hour, the Tiller Pin bracket is installed. There was no need for the stabilizing bolts, it's secured really well just using the Center Bolt.

This photo was taken after the install was completed, it shows the Connecting stud already installed.












Peggy had a good idea! Use a clamp to hold the RPS unit mounting plate to the underside of the shelf support braces.

I didn't have a suitable clamp on board, but I did have a velcro strap, it worked like a charm. That probably saved the day, I just don't see how I could have held that mount in place and screwed the plate to the underside of the shelf support brace.

Thanks Peggy.





This shows the completed install. the RPS is screwed to that Green plastic plate which is then screwed onto the underside of the Shelf support brace.

The biggest issue is getting the alignment correct and I'm not sure how accurate it is. This area is really difficult to work in.

The RPS has 3 slots around its circumference, that allows for some adjustments. The Connecting stud also has about 1/2" adjustment due to the two nuts on the connecting stud. 


Now that it's completed, I took this set of images.
But just to give it some context, this job involved quite a bit of Boat Yoga.

Getting into the aft locker / lazarette, takes some doing, but getting down into position in order to be able to reach the underside of the Steering Radial Drive requires a bit more flexibility.

I'm on my second shirt in this pic, the first was sodden by the time I finished installing the Tiller Pin Support Bracket.

Peggy took a couple of pics when I was not looking.







With the Rudder Position Sensor installed, we're ready for the next step. Run the wire from the RPS to the Autopilot Control Unit (ACU) and Install the EV-1 Sensor Core, both those jobs are easy by comparison to this part of the project.

Total time to install the RPS at the Boat -  3½ Hours. Plus the loss of a few pints of sweat equity.

See you on the Water.

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