Composite Motorcycle Skidplate Designs

Toviah added a notch to see if it would improve deflection for the XT200 Skidplate.

Based off our simulation we are trying for 25 percent increase in rigidity over the initial prototype.

And with two ridges:

If you look at the scales we are seeing a significant increase in stiffness, something like a 21% increase over the current prototype.

There are animation files too which will be added as available.

After removing some material around the exhaust I forgot to account for and moving a mount point we got the skidplate for the XT200 mounted and some miles logged. No bad vibrations and a close fit.

It actually blends in with the bike due to its low profile.

We might use a sheet metal insert to oven cure our next part to avoid heat deformation ahead of use.

You can barely see it!

We are adding contours and a lip network to increase rigidity and then plan on CNCing out a foam mold for the next iteration while working on the BMW skidplate which will be a little more complicated. We have run some basic simulations and will share some visualizations when we get the chance.

We removed the part from the mold today.

The female side of the mold was pretty well stuck so we had to break it apart.

The insert block for the overhang hook was also really stuck in there.

After cleaning up the edges this seems like a pretty usable part. Its definitely too thin and the surface finish is far from perfect but things are looking good.

The front mount point will need to be drilled out but the pilot hole came out clean.

Now to double check that it fits on the bike and see how it responds to loads!

To make our cutsheets for the skidplate I unrolled our digital model, this will be included in the files section.

It's not very complicated but annoying to cut out with scissors. A laser seemed like it should do the trick.... And yes, we're including the hole.

Each sheet takes about a minute and a half to completely cut out. It takes much longer to just get it off the bolt.

We are able to get very precise cuts. Burns could probably be minimized by going a little faster, I had the settings up pretty high. Ahem, shameless plug:

Then actual lay-up began.

Some cut-sheets got messed up because of tape, going to have to minimize that in the future.

Here you can see some kinda ugly patch-working:

The outer most layer is 50/50 Carbon and Kevlar. Kevlar doesn't like UV light very much but since this is a semi-disposable component I'm going to give it a shot to see if it helps with scratches and such. I also added the Wallfacer Design logo, because I can.

The end tab was folded over into the insert and then the top half of the mold was lined up and clamped down as hard as we could.

To help with clamping force in the future we should cut the mold exterior faces flat.

We did a poor job of recording our first couple of FEA simulations so hold tight for those.

The XT200's skidplate has simpler curvature so is being attempted first.

At first I used the pilot curve to cut a bunch of wooden templates and then attach them together to make a positive mold.

 Since we still don't have the vacuum system working I changed my mind and made a two part blue foam mold.

It has a slot for an insert block for the overhang tab that connects near the swing-arm connection.

To get a feel of lay-up a couple samples were devised.

All samples came out pretty well considering we didn't put them under vacuum.

To perform simulations we need 3D models of our skidplate designs and existing designs to compare behavior.

The BMW's Skidplate conveniently fits on my bookbag.

A surface was made in Rhino, then transferred to Solidworks for some details such as bolt holes.

We tried to replicate the existing design as closely as possible except for rounding of edges.

Since the XT200 did not come with a skidplate we are making some assumptions based off of exposed hardware.

We have been working on developing a code to facilitate the computation of properties of a given composite.

This started as a spreadsheet but has since moved to code.

Information from this is used to feed data to Solidworks for FEA Simulation.

Since this is a rather complicated subject I won't get into this too deep.

Essentially composites behave differently depending on the orientation of yarns and resin to fiber volume fractions among many other factors such as actual form.

By changing the design or layup we have a completely different result. Typically this is insanely proprietary, mostly because its difficult to explain haha.

Because composites layup is a heavily hand labor influenced process the results can vary quite a bit, adding confusion. Think of this as a very scientifically informed craft.

I will upload our spreadsheet.

Two bikes have been chosen since they are immediately available to us.

The 1983 Yamaha XT200 and 2006 BMW F650GS.

BMW Skidplate removed view:

The Yamaha:

No reference skidplate; view of skidplate region:

Engine is a stressed member and fully exposed. This keeps the XT at a 203lb wet weight but is a serious vulnerability.