+x

 

Steve Broad - 8/27/2018 9:02:35 AM

With regard to bolting, I use these. Length of tube equals thickness of composite so crushing is not possible. Machined out of aluminium round bar and glued into the composite with a suitable adhesive. This one is actually threaded (M6 which will give you an idea of size) as it sits in the car floor with the bolt securing an undertray. The washer spreads the load over the carbon undertray. 



These are bigger and secure the pedal box to the floor. They aren't threaded so are just top hat washers but were countersunk prior to gluing in. Just an idea.

+x

 

quinn - 8/27/2018 2:05:28 PM

+x

 

Steve Broad - 8/27/2018 9:02:35 AM

With regard to bolting, I use these. Length of tube equals thickness of composite so crushing is not possible. Machined out of aluminium round bar and glued into the composite with a suitable adhesive. This one is actually threaded (M6 which will give you an idea of size) as it sits in the car floor with the bolt securing an undertray. The washer spreads the load over the carbon undertray. 



These are bigger and secure the pedal box to the floor. They aren't threaded so are just top hat washers but were countersunk prior to gluing in. Just an idea.

Those look pretty handy, although I think I would gain more weight back than I lost going with light core. About 30 bolt holes in a 200mm x 500mm frame side. Although it would be nice to come up with a solution that doesn't involve reinforcing the bolt locations during lay up.  Maybe when cuttimg out side frames,  drill an m3 hole to 4mm and epoxy in short sections of 4mm OD 3mm ID tube in each hole or something like that. I'll probably just experiment with bolting through the sandwich and see how it does. Might be fine as is, especially the soric that pretty much ends up with a rigid honeycomb pattern inside. A foam core with no honeycomb would probably be more likely to have issues in bolt locations. Another possible solution could be a tiny key hole cutter with a 1mm shank and opens up to 3mm diameter by 1.5 high. After cnc drills all holes, it could come in with the key hole cutter and open up just the core to 5mm diameter at each 3mm hole. Fill those back in with resin and then drill to 3mm. Each bolt hole would end up with a 1mm wall column of resin between outer skins for reinforcement. Actually I could even run the keyhole cutter around the outside edges as well and have a 1mm thick wall of resin bridging the skins at the edge. At that point a lighter foam core could probably be used. Starts to become a lot of work though at that point though

+x

 

oekmont - 8/27/2018 5:33:41 AM

Out of the three cores I mentioned, soric lrc (lrc is the lightweight soric version) is the heaviest one, but acts as a flow media. Not as good as regular flow media, but good enough. The density of the core after infusion is far below 1g/cm^3, while solid carbon is around 1,6g/cm^3. In my applications a similar laminate with 1,5 soric lrc flows in water.
The closed cell foam cores are far lighter in comparison, but do not make a huge difference when it comes to thin cores, as the core surface takes up some resin, and thin cores have more surface per volume than thick cores. they will be lighter, still.

+x

 

Steve Broad - 8/27/2018 2:28:43 PM

+x

 

quinn - 8/27/2018 2:05:28 PM

+x

 

Steve Broad - 8/27/2018 9:02:35 AM

With regard to bolting, I use these. Length of tube equals thickness of composite so crushing is not possible. Machined out of aluminium round bar and glued into the composite with a suitable adhesive. This one is actually threaded (M6 which will give you an idea of size) as it sits in the car floor with the bolt securing an undertray. The washer spreads the load over the carbon undertray. 



These are bigger and secure the pedal box to the floor. They aren't threaded so are just top hat washers but were countersunk prior to gluing in. Just an idea.

Those look pretty handy, although I think I would gain more weight back than I lost going with light core. About 30 bolt holes in a 200mm x 500mm frame side. Although it would be nice to come up with a solution that doesn't involve reinforcing the bolt locations during lay up.  Maybe when cuttimg out side frames,  drill an m3 hole to 4mm and epoxy in short sections of 4mm OD 3mm ID tube in each hole or something like that. I'll probably just experiment with bolting through the sandwich and see how it does. Might be fine as is, especially the soric that pretty much ends up with a rigid honeycomb pattern inside. A foam core with no honeycomb would probably be more likely to have issues in bolt locations. Another possible solution could be a tiny key hole cutter with a 1mm shank and opens up to 3mm diameter by 1.5 high. After cnc drills all holes, it could come in with the key hole cutter and open up just the core to 5mm diameter at each 3mm hole. Fill those back in with resin and then drill to 3mm. Each bolt hole would end up with a 1mm wall column of resin between outer skins for reinforcement. Actually I could even run the keyhole cutter around the outside edges as well and have a 1mm thick wall of resin bridging the skins at the edge. At that point a lighter foam core could probably be used. Starts to become a lot of work though at that point though

Aluminium is approx 2.7 times as heavy as epoxy resin. A quick calculation using aluminium top hats 6mm dia and 2mm deep with a 10mm dia flat top, 30 of these will weigh 7.5gms :-) 

+x

 

quinn - 8/27/2018 2:32:02 PM

+x

 

Steve Broad - 8/27/2018 2:28:43 PM

+x

 

quinn - 8/27/2018 2:05:28 PM

+x

 

Steve Broad - 8/27/2018 9:02:35 AM

With regard to bolting, I use these. Length of tube equals thickness of composite so crushing is not possible. Machined out of aluminium round bar and glued into the composite with a suitable adhesive. This one is actually threaded (M6 which will give you an idea of size) as it sits in the car floor with the bolt securing an undertray. The washer spreads the load over the carbon undertray. 



These are bigger and secure the pedal box to the floor. They aren't threaded so are just top hat washers but were countersunk prior to gluing in. Just an idea.

Those look pretty handy, although I think I would gain more weight back than I lost going with light core. About 30 bolt holes in a 200mm x 500mm frame side. Although it would be nice to come up with a solution that doesn't involve reinforcing the bolt locations during lay up.  Maybe when cuttimg out side frames,  drill an m3 hole to 4mm and epoxy in short sections of 4mm OD 3mm ID tube in each hole or something like that. I'll probably just experiment with bolting through the sandwich and see how it does. Might be fine as is, especially the soric that pretty much ends up with a rigid honeycomb pattern inside. A foam core with no honeycomb would probably be more likely to have issues in bolt locations. Another possible solution could be a tiny key hole cutter with a 1mm shank and opens up to 3mm diameter by 1.5 high. After cnc drills all holes, it could come in with the key hole cutter and open up just the core to 5mm diameter at each 3mm hole. Fill those back in with resin and then drill to 3mm. Each bolt hole would end up with a 1mm wall column of resin between outer skins for reinforcement. Actually I could even run the keyhole cutter around the outside edges as well and have a 1mm thick wall of resin bridging the skins at the edge. At that point a lighter foam core could probably be used. Starts to become a lot of work though at that point though

Aluminium is approx 2.7 times as heavy as epoxy resin. A quick calculation using aluminium top hats 6mm dia and 2mm deep with a 10mm dia flat top, 30 of these will weigh 7.5gms :-) 

Are you sure that's right? Each one is a quarter of a gram? That doest seem right. An aluminum m3x8 screw weighs that much. How thick is the 10mm flat top? And are you figuring for a 3mm hole or 4mm hole?

+x

 

Steve Broad - 8/27/2018 2:54:56 PM

+x

 

quinn - 8/27/2018 2:32:02 PM

+x

 

Steve Broad - 8/27/2018 2:28:43 PM

+x

 

quinn - 8/27/2018 2:05:28 PM

+x

 

Steve Broad - 8/27/2018 9:02:35 AM

With regard to bolting, I use these. Length of tube equals thickness of composite so crushing is not possible. Machined out of aluminium round bar and glued into the composite with a suitable adhesive. This one is actually threaded (M6 which will give you an idea of size) as it sits in the car floor with the bolt securing an undertray. The washer spreads the load over the carbon undertray. 



These are bigger and secure the pedal box to the floor. They aren't threaded so are just top hat washers but were countersunk prior to gluing in. Just an idea.

Those look pretty handy, although I think I would gain more weight back than I lost going with light core. About 30 bolt holes in a 200mm x 500mm frame side. Although it would be nice to come up with a solution that doesn't involve reinforcing the bolt locations during lay up.  Maybe when cuttimg out side frames,  drill an m3 hole to 4mm and epoxy in short sections of 4mm OD 3mm ID tube in each hole or something like that. I'll probably just experiment with bolting through the sandwich and see how it does. Might be fine as is, especially the soric that pretty much ends up with a rigid honeycomb pattern inside. A foam core with no honeycomb would probably be more likely to have issues in bolt locations. Another possible solution could be a tiny key hole cutter with a 1mm shank and opens up to 3mm diameter by 1.5 high. After cnc drills all holes, it could come in with the key hole cutter and open up just the core to 5mm diameter at each 3mm hole. Fill those back in with resin and then drill to 3mm. Each bolt hole would end up with a 1mm wall column of resin between outer skins for reinforcement. Actually I could even run the keyhole cutter around the outside edges as well and have a 1mm thick wall of resin bridging the skins at the edge. At that point a lighter foam core could probably be used. Starts to become a lot of work though at that point though

Aluminium is approx 2.7 times as heavy as epoxy resin. A quick calculation using aluminium top hats 6mm dia and 2mm deep with a 10mm dia flat top, 30 of these will weigh 7.5gms :-) 

Are you sure that's right? Each one is a quarter of a gram? That doest seem right. An aluminum m3x8 screw weighs that much. How thick is the 10mm flat top? And are you figuring for a 3mm hole or 4mm hole?

I think so, it seemed light to me also so I checked and checked again :-)

6mm diameter tube with a 3mm dia hole and 2mm long (thickness of composite) = 0.1145gms
10mm diameter 'washer' with 3mm diameter hole and 0.75mm thick = 0.1447gms
0.2592gms x 30 = 7.776gms :-)
There is, of course, the extra weight of the bonding adhesive :-)
A lot easier that faffing about with resin and a lot stronger, as long as you have access to a lathe. This is the way I have done it on my car and I am so anal about weight that I even centre drill titanium bolts!

+x

 

Hanaldo - 8/27/2018 3:14:34 PM

If you're open to doing a 2 or 3 shot process, then honeycomb cores are by far the lightest (they barely add any weight to the skins, aside from the adhesive).