The making of.... THE RIMS

Today I am telling you about the rims I am making. We decided to make new rims in carbon fiber, this year as every year. But the difference this year is that the rims are going to hold 5 bar while we are driving, without leakage or cracking.

Since doing advanced analyzes is time consuming, and the analyzes often get poorly done, I decided to make the rims based on the previous years trials and the knowledge of experienced people.

My intention was to make the rims 100% reliable, and not care so much if the rims are 200 grams or so heavier than before.. And as cool as these carbon fiber rims to the left below. At least as better than the previous years' rims..

The right wheel above is from the first year NTNU participated in the Shell Eco-marathon, and these wheels are actually the best set of rims so far. Until this year of course....

So I started to ask people at the institute, and they were happy to help me with good advice.

Nils Petter Vedvik - Associate Professor

Andreas Echtermeyer - Professor

Arve Sinnerud - Master student

We were also really lucky, because there is actually a very skilled exchange student at the institute this year. He has worked on this type of carbon fiber before, and joined the team!

This is Rico Khlewind from Germany..

After some research, I found a man in Fredrikstad that is an expert on composites. I talked to him over the phone, and he had a lot of interesting points, and useful tips for the production. So I went to Fredrikstad to meet him in his workshop. This is Paal at HP Composites..:

After some thinking, discussing and designing, I decided to make the rims in two piece: the actual rim ring, and the center plate. The sketch below shows the two pieces, and the metal center piece that Aksel is making.

Paal was so kind to make the center plates in carbon fiber in his workshop, and send them up. We got the materials sponsored from Lindberg & Lund. We made the outer rim ring here in our workshop, and glues in the centerplates with glue (also sponsored by Lindberg & Lund).

To make the rim rings as smooth as possible, I made a new mold for the rim that was negative. This way we will get a smooth surface where the tire sits, so the air don't leak out.

Here is a picture of the production of the mold and how it worked out:

Tim is the expert on getting a tight vacuum during the baking of the carbon fiber in the oven.

Bjarne Stolpnesster helped us with this in the milling machine in the Prototype lab.

In the picture above we are milling out the center hole for the metal piece. It is important to get this hole in the middle of the rim, so that the car will ride smoothly.

This is the finished rim:

Rico and Alex are testing it to see if it is accurate enough..

We might coat it so it will get an even cooler look.

If you follow the blog, you've already read about two tests on the rims. The first one was a success, but in the recent test the rim exploded... The carbon fiber in this last rim is lighter, and thinner, so it is not as stiff. But we are designing a better lay-up for the next ones, so they will hold 5 bar like promised!

So stay tuned this week; we are hopefully finished assembling the whole car soon.... Only a few weeks left to the race!

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