Pages

Introduction

I hope this site is of value and contains information. I will record my ramblings regarding sailing adventures, my boat projects and anything else that might interest people attracted to a site about Wharram catamarans.

Please visit again for updates and do leave your comments.


Wednesday 13 June 2018

Auto Tiller Prototype

In a weak moment and with an impulsive click on eBay,  and an auction was won. The TP1000 auto tiller was mine!

As the victory faded, attention turned to how it would work. An auto tiller is designed to simply connect to a tiller in the middle of a boat. What could be simpler?

They connect at around 30cm (1ft) from the pivot point and have enough power and reach to push and pull the tiller and control the boat. They have a built in flux-compass. Press the button, and it keeps you going on a fixed heading.

The trouble is, my Tiki 21 has two tillers, with a cross bar linkage. The tillers are nearly 2 meters long. It might be possible to mount the auto tiller on one tiller a foot from the rudder and it would work. However, it would be well out of reach. Some research was necessary. How to connect the control unit?

Here are a few examples:

In the idea below, an extra stub tiller at 90 degs is added to the tiller and the auto tiller uses a long extension bar.


Of course, I also checked out Roger's blog which is full of useful information. In the end it's Roger's basic design that makes sense. However, I can't easily use the track and chain linkage like Roger as my rear beam has mainsheet and genoa cleats in the way.


In Roger's design above, the auto tiller can be quickly released and different chain links selected in the drive chain. Whilst I'm not going to use the track, the rope arrangement seems the best choice.

In the drawing below the ropes run around and cross over to drive the tiller arms. The auto tiller needs to grip the rope which runs across the rear beam.
The blocks shown here can simply be attached with rope. But a way to connect the auto tiller to the hull and to the rope is required.

To fix the auto tiller, I made a simple block out of two discs of ply epoxied together.
With a hole in the middle to accommodate the tiller pilot pin, it just needed epoxying to the boat. 
An area was masked off on the hull just behind the rear beam and the finished mount stuck on and painted. After this was fixed, I set the boat up in the yard with the control lines and blocks in place. Then I positioned the auto tiller to see how the whole thing looked.
It looked fine. I just needed a way to get the shaft on the pilot to grip the rope. This was tricky as it needs a release mechanism. 

I turned to the 3D printer. Here's the first prototype. The lever rotates an off-centre cam which moves a plate to grip the line.
At the bottom, you can see the half tube shape. Another piece fits over the tiller pilot shaft and is screwed on to grip. This design is ok, but is a bit complicated. The moving plate is unnecessary. The first prototype was also flimsy and needed beefing up. 

Here's the second version in which the cam grips the rope. This prototype has the top parts screwed on and is in the release position.

Here's the same thing with the level in the grip position and the cam is seen compressing the rope.
Finally here's the working version which was printed with thicker walls and a slightly improved design. And yes it works. I'll update once it's been tested in all bit calm conditions.



2 comments:

  1. Would opposing clamcleats mounted direct on the ram work? Harder to adjust quickly but available.

    ReplyDelete
  2. That would work. One useful feature on the autopilot is to be able to quickly engage and disengage the pilot and the lever work well for this.

    ReplyDelete