Bushings on your forward crossbeams?

[Chotu]

hey everybody. Looking to get a consensus of what’s out there.

my plans call for bushings between the pin that holds the Crossbeam and the Crossbeam and bracket. Like in the attached photo.

most crossbeams seem to have a bushing here. What is yours made from?


I’m thinking Delrin? Is there something else I should be using? Does it have to be metal? Because I’m trying to avoid dissimilar metal problems with the stainless and aluminum.

[Chotu]

What about naval bronze? That’s what the machinist was going to use.

[Chotu]

well, there was not enough time to wait for an answer. I went with Delrin.

[wyb2]

Not sure why no-one chimed in. I would think delrin is a solid choice, it will insulate the aluminum and SS against galvanic corrosion, has a low coefficient of friction which will help prevent it getting ground to dust by small movements of the joint, and will probably deform instead of failing catastrophically if the loads are too great.


Just check the joint for gradually increasing play. If it develops extra play early, switch to something harder. If not, you should be golden.


What are you using for the shims depicted? I would think delrin there too for all the same reasons.

[Chotu]

Originally Posted by wyb2

Not sure why no-one chimed in. I would think delrin is a solid choice, it will insulate the aluminum and SS against galvanic corrosion, has a low coefficient of friction which will help prevent it getting ground to dust by small movements of the joint, and will probably deform instead of failing catastrophically if the loads are too great.


Just check the joint for gradually increasing play. If it develops extra play early, switch to something harder. If not, you should be golden.


What are you using for the shims depicted? I would think delrin there too for all the same reasons.

thank you very much for the vote of confidence. Hopefully the Delrin will work.

and also hoping I have a boat left after next week

[rslifkin]

As long as the Delrin doesn't squish too much under load I expect it'll work fine.

[Chotu]

Originally Posted by rslifkin

As long as the Delrin doesn't squish too much under load I expect it'll work fine.

That was really my only negative thought also. The stuff does seem to be pretty rugged. My rudder bushings are made out of it.

[Rumpi]

The bushing should be stainless, hydraulically pressed in. After the pin gets installed everything gets smothered with duralac.

[Chotu]

Originally Posted by Rumpi

The bushing should be stainless, hydraulically pressed in. After the pin gets installed everything gets smothered with duralac.

How come nobody told me this before? I did Delrin.

Do you think it’ll last a while?

[rslifkin]

Being that you already went delrin, I'd just plan to monitor them and see if they show any issues that would make you want to swap them out later.

[Chotu]

Originally Posted by rslifkin

Being that you already went delrin, I'd just plan to monitor them and see if they show any issues that would make you want to swap them out later.

Yeah. I’m thinking the Delrin will hold up. The load isn’t tremendous and there is not much play to wear them down.

[smj]

I believe ours are delrin and no problems.

[Chotu]

Originally Posted by smj

I believe ours are delrin and no problems.
Attachment 264901

Great!

The Crossbeam I bought from the Chris white Atlantic 55 has a thin plastic bushing where a very large diameter pin goes.

[Rumpi]

Yes it will hold for a while. Worst thing that can happen is that play develops and the hole in the Al deforms and becomes oval. Monitor the situation and take appropriate action.

The bushing is used to harden the hole since Al is softer then steel and the fit between hole and pin is not perfect the force is transmitted only in a small contact area. The bush has a perfect fit with the hole (that's why it's pressed in) and can transmit the force correctly while resisting deformation from the non perfect fit with the pin. If there is enough Al the bushing isn't necessary, if not it deforms. How well the delrin fares remains to be seen and probably depends on the involved sizes.

Why nobody told you begins with the designer who assumed the fabricator knows standard procedures, and ends with you not googling "aluminium chainplate bushing".