Centre Rudder Block - play. Normal?

[TASEsq]

I hung my rudder pedals and split the centre block using a Japanese saw, which has a very tiny kerf.

I installed the blocks with a thick washer and tightened it down, checking for friction on the rudder bars. There was no friction present and I realised the plastic block was actually deforming around the washer somewhat. There was a lot of side to side play in the assembly - like the block was not clamping onto the rudder bars.

I removed the thick washer and replaced it with a thin set, but the same issue. It feels like the blocks are not clamping on the bars, and there is side to side play.

Is this normal? or could the very thin kerf of the Japanese saw be causing me issues - aka the block halves are too tall they cannot clamp onto the bars.

I have not tried installing it yet with no washers (as the plans call for a washer), but this was my next thought.

Unless this is how everyone else’s assembly is?

Here’s a video of the play:

 

[stigaro]

I hung my rudder pedals and split the centre block using a Japanese saw, which has a very tiny kerf.

I installed the blocks with a thick washer and tightened it down, checking for friction on the rudder bars. There was no friction present and I realised the plastic block was actually deforming around the washer somewhat. There was a lot of side to side play in the assembly - like the block was not clamping onto the rudder bars.

I removed the thick washer and replaced it with a thin set, but the same issue. It feels like the blocks are not clamping on the bars, and there is side to side play.

Is this normal? or could the very thin kerf of the Japanese saw be causing me issues - aka the block halves are too tall they cannot clamp onto the bars.

I have not tried installing it yet with no washers (as the plans call for a washer), but this was my next thought.

Unless this is how everyone else’s assembly is?

Here’s a video of the play:

It would seem to me that this would a good thing, no? I would have thought the central support is there more to hold up the rudder bars rather than to clamp them down. My setup definitely is more secure, but that just points to more friction. I used a thin bandsaw blade to cut mine and have 0.032" washers.

 

[Ralph Inkster]

Center bushing is to prevent the tubes from bending forward when foot braking forces are applied. The bracket will never move sideways in use - so your bushings are good as is.
Keep building!

 

[rvbuilder2002]

The purpose of the spacer washer is to replace the material removed when the block is sawed into two pieces. If the saw you used has a curf that is less than the thickness of the washer, then a different washer thickness should be used.
Considering the saw you described, you could likely use a thin washer instead.
UHMW blocks are not a hard material. Through the blocks should never be torqued to standard torque values. The block will get severely compressed.

 

[PaulvS]

I also used a thin kerf Japanese pull saw to split the blocks and instead of a washer there is a piece of rectangular .025 aluminium to replace the material that was removed. The bent tab makes it easier to insert than a washer.

 

[TASEsq]

I also used a thin kerf Japanese pull saw to split the blocks and instead of a washer there is a piece of rectangular .025 aluminium to replace the material that was removed. The bent tab makes it easier to insert than a washer.
View attachment 55515

Great idea. Thank you. My Japanese saw was 0.012” thick - the thinnest material I had was 0.016” so used that. They are still slightly wobbly back and forth but better. I just tightened them until the friction to turn the bolt head changed.

 

[Desert Rat]

Great idea. Thank you. My Japanese saw was 0.012” thick - the thinnest material I had was 0.016” so used that. They are still slightly wobbly back and forth but better. I just tightened them until the friction to turn the bolt head changed.

A soda can is probably about .010 thick and would work fine as a shim in this application.

 

[TASEsq]

A soda can is probably about .010 thick and would work fine as a shim in this application.

Even better, ALDI here sells a cheap beer, sold in packs of 12 cans of shim material, and the beer is called “RIVET”. I often pop into the shed “to do a few rivets”.

 

[TASEsq]

A soda can is probably about .010 thick and would work fine as a shim in this application.

Thanks for this advice.

I used a Bundaberg Ginger Beer can (uniquely Australian since it’s an Australian machine).

This was pretty thin - 0.0040. The saw blade I used had a kerf of 0.0120, so the shim was about 1/3 the thickness of the blade.

Tightened it just a bit more than when I felt resistance - maybe 1/4 a turn.

All the wobble in the bracket is gone but the pedals still move freely.

Thanks again for everyone’s advice.