-
It’s easier to cut (main reason) and it’s better in compression and shear than Nomex. You’d usually use Nomex on thinner gaps. I shaved a thicker bit down to the correct thickness. Bonding it in is no different as I’ve used what I believe is the strongest 2-part epoxy adhesive available. We’ve got stronger adhesive films which are lighter, but I’d have to tape it all up and vac bag it, whereas with this I can just spread it on and weight it down on the surface table overnight. I forgot to take a pic before I put it together!
1 Attachment
-
-
Ah right, makes sense. Not having to bag it would have been enough of a reason for me.
M40J is a mostly outdated fibre
This made me laugh, by the way. A year ago this was our high-end fibre, only used on special occasions. But then again, you lot probably spend more on a single wing element than a student team on their entire car.
-
We’ve got a couple of generations of fibre newer than M40J. M46J pretty much superseded it, which is a general purpose stiff fibre, but there’s a whole new generation of fibres coming through that offer higher strength as well as the high stiffness. These are replacing those older-style fibres where you had a choice of high strength, high modulus, or somewhere in between but not both.
-
I need to linish it round the edge, but it’s cured and ready to mark up for the hub. Brake tracks, from what I can make out, seem to be an abrasive coating on the rim. I haven’t got anything like that I can use. My Russian disc and Corima 4-spoke don’t have anything on them.
1 Attachment
-
-
Last one for the day. Got the hub fitted and dry mounted. Laterally it’s bob on and roundy roundy there’s about 1mm run out. That’s better than either of my discs but I might just give it a fettle tomorrow and see if I can get it spot on before bonding it in.
Total weight is 1350g. Considering the rim is 500g of that and the hub 200g, it’s not actually turned out too heavy. I’d love to have a crack at a proper hollow disc in a mould, aero section and carbon hub. Can’t see why you couldn’t get a 700c size down near 600g. Pipe dreams...
Running quite short of time now, so I’ve really got to crack on with this if I want to get anything else built as well.
1 Attachment
-
-
Badass.
So which are the expensive parts here that results in a disc wheel costing £800? Would that sheet of carbon fibre have cost a lot had you not used off-cuts? Or is it your knowledge/skills/labour that's the expensive bit?
-
Rough breakdown of some of the costs:
-I think I’ve put about 15 hours of my time into it in total. That doesn’t include any design or development because I haven’t done any.
-Pre-preg is between £35 and £100 per square metre and I probably spent about 2 hours cutting the triangles by hand, laminating it and bagging up. There’s probably 3-4 square meters used here taking into account the amount of scrap that would be generated.
-Autoclaves aren’t cheap. A small one is about £35k and that needs to be factored in, though a lot of carbon which doesn’t have to be highest quality is now being made out of clave.
-If there’s a proper shaped mould, this will add a few £k to the cost.
-A custom hub will also be quite expensive.Essentially, a flat disc in general purpose carbon with a foam core is not that expensive to make. Once a bit of development and moulding are factored in, the costs start to rise. Then it’s a matter of each incremental bit adding cost, like adding stiffness and lightweighting.
-
Really interesting, thanks!
-
Such amazing!
kwdm
Tijmen
clipon
deleted
mashton
MCamb
Heldring
frankenbike
Tijs
larsenroad-
Post a reply
About
Gonna make a pimpin carbon disc wheel from scratch
Posted by
@Jonny69
Cheers guys. Hopefully get the other skin bonded on after work tonight so I can trim it up tomorrow and look at bonding the hub in.