Making carbon swingarm

Tuesday 4 Dec 2012, 5pm

I’ve been a bit busy since my last blog.

Friday was a learning experience. I wanted to preform mounts for the swingarm components, which are seen here after spraying with etch primer. The tubes were later sheathed with a layer of fibreglass and the smaller aluminium components were coated with epoxy, to prevent contact of this metal with carbon fibre and consequent galvanic reactions.

 and after an all day effort arrived at this mess

  

Which I realised was going to be inordinately complicated to cast with the components in situ, and decided that night that it would be rather easier to fit the components after casting the swingarm.

On the weekend I took a couple of days off and drove up into the forest at the end of our road with Chris and David for the purpose of arting. Much fun was had by all. Here’s the result (all pastel and Charcoal) –

Sylvester’s (Saturday)

Mt Walker (Sunday)

In the Creek (Sunday)

My first artistic efforts in three years. Not much to do with engineering, but this is my blog after all.

Yesterday I got stated on the carbon fibre (that’s ‘fiber’ to any Americans reading this) components. I started by making two new cores for the swingarms from surfboard foam.

Then I started wrapping them in carbon socks

This shows the materials used in the wrap. Unidirectional at top and two diameters of sleeves below. The smaller sleeve (32mm) is stretched and consequently the weave is more across the component than the 64mm tube, thereby giving a couple of different directions of weave to combat twisting. The unidirectional gives strength along the spar. Thirteen layers in all, giving about 6mm walls to the tube. A bit over the top, really.

About ten layers at this stage.

This is the final tube assembly with the materials for the layup, firstly peel ply (which I stitched in place), then breather fabric (allows the resin to flow around the outside of the component) and finally the transparent bagging plastic. All materials came from playwithcarbon.com

This is the part ‘in the bag’. Mastic used to seal the edges and inlet and outlet ports fitted with extra breather under them (unnecessary, as I discovered).

This is the vacuum pump and catch pot (for excess resin drawn off the casting) in action

And this is the layup with vacuum applied (14 pounds per sq inch, or one atmosphere), no resin introduced as yet

And here we go with the resin. The tube between the inlet and outlet is clamped during infusion, then opened to apply suction to both ends of the layup. Carbon nanotubes mixed in the resin give it its black colour (Americans read 'color'). Fingers crossed.

Unwrapping at 9 last night –

Needs a bit more force –

Finally naked –

Today I put the second arm in the bag and proceeded to clean up the first arm (has a note of cast iron when you bang it on the fireplace) and ready it for it’s metal components. Apologies for the quality of the next few pics, didn’t realise the camera was on the wrong setting until much later. Clamp the arm in the jig –

Drill out a couple of holes and then bolt the arm through these to drill the rest of the holes.

Preparing the jig, sealing with plasticene and bagging plastic. It leaked. You can see the aluminium tube has a layer of fibreglass on it.

Finally woke up to the camera setting -

Pouring resin mixed with nanotubes into the swingarm to anchor the metal components. That’s it for today, hope you’ve enjoyed my first foray into resin infusion. I’m nackered. Bottling elderflower champagne in the morning for a change.