Carbon Fibre Swingarm Construction for Carbon Bonneville – Step 4

Posted on 2nd August, by John_Admin in Cafe Racers, Project Bikes. No Comments

step 4: main spar bracing core

After wrapping the main spar joints, I need to brace the main spar in the section infront of the wheel leading up to the pivot tube.

The reason for this bracing are 3 fold.

1) to add to the lateral  rigidity of the main spars like a gussett. This hugely reduces the point loading on the wrapped and bonded main spar joints by spreading the load.

2) to add tortional rigidity to the structure. This is achieve with the specific laying up of different types of carbon fibre in the brace core and on the outside of the area. Layer the fibres at 45/45 deg to the  direction across the flat area of the top and bottom of the brace will increase tortional rigidity of the structure.

3) to provide a platform onto which the suspension linkage mounts will be bonded at a later stage.  Also I will have to bore a hole through the brace core and then reinforce the walls of the hole. The hole is required so that the suspension actuating rod can pass through the swingarm and locate on the bottom frame mount.

The core in this case is a rigid open cell type foam so it absorbs a certain amount of resin with then cures and make the core very rigid. This rigid foam core is also very light weight.

See below the fit up stage of the brace core.

Each layer of foam is bonded to the next until the required thickness is achieved.  At this stage I added a layer of carbon cloth top and bottom to furter consolidate the structural integraty.

Again I don’t have a pic of the full 5 layer of foam core in position, but you can get the idea.

Next post will be step 5: main spar bracing core wrapping & step 6: fabricate and bond the mounting point for linkage Delta and bore hole on gussett for delta bottom linkage


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