Quote from: woods170 on 04/09/2018 01:13 pmQuote from: Cheapchips on 04/09/2018 12:53 pmInteresting that they not using the big robot arm approach used by NASA/Boeing/Janicki. I assume it's since they're attaching the domes after, this giant tube is simpler.I'm assuming, in ignorance, that the outer tube will allow them to cure it in place (Also assuming out of autoclave).I suggest do not assume anything. The image shared by Elon shows just the lay-up mould, resting on its supports, housed in a temporary facility. The tent is NOT where actual manufacturing of BFS will be done. This is just an image of recently arrived tooling sitting in temporary storage.The stands the cylinder is sitting on seem to be more substantial than SpaceX would build simply to store a bit of tooling. They look like tooling.
Quote from: Cheapchips on 04/09/2018 12:53 pmInteresting that they not using the big robot arm approach used by NASA/Boeing/Janicki. I assume it's since they're attaching the domes after, this giant tube is simpler.I'm assuming, in ignorance, that the outer tube will allow them to cure it in place (Also assuming out of autoclave).I suggest do not assume anything. The image shared by Elon shows just the lay-up mould, resting on its supports, housed in a temporary facility. The tent is NOT where actual manufacturing of BFS will be done. This is just an image of recently arrived tooling sitting in temporary storage.
Interesting that they not using the big robot arm approach used by NASA/Boeing/Janicki. I assume it's since they're attaching the domes after, this giant tube is simpler.I'm assuming, in ignorance, that the outer tube will allow them to cure it in place (Also assuming out of autoclave).
The stands I believe are more than just stands - they are rollers - some driven and some passive. Meaning that there are no end domes, rather the composite wraps around the mandrel to form a barrel section. This means that the barrel section doesn't go to the ends of the mandrel (where the rollers are). I would also go so far as to say that the near side end may have air injectors and the far side has a taper to allow the mandrel to be removed from the composite barrel segment when complete. This would make it some amount less than the assumed 15M in length. (I've annotated, with what looks like a four year old's ability, the image to point out the ends of the actual composite barrel and possible air injectors at the near end). Also, the outer diameter of the mandrel is of course the inside diameter of the barrel section of the BFS (and perhaps BFR as well?). Any guesses as to how thick the actual composite / insulation / etc will be? Very curious as to how they intend on mating the three dome sections (including the common inside dome between the two tanks).Woods170 gave a nice photo of the Dragon trunk barrel section being wound - quite possible this will utilize a similar process.
The stands I believe are more than just stands - they are rollers - some driven and some passive.
Any guesses as to how thick the actual composite / insulation / etc will be?
The mandrel is heavy so it needs to be rotated to avoid deformation at the roller supports, just like a loaded rail car deforms the track and the wheels when it sits overnight.
Quote from: Johnnyhinbos on 04/09/2018 04:52 pmThe stands I believe are more than just stands - they are rollers - some driven and some passive.I'll buy that and further add that the things that look like control stations below the rollers may actually be control stations for the rollers. However it could be that those rollers and stands are leftovers from the process of fabricating the mandrel in place there, not the ones that will be used to lay on carbon. Assuming for a second that the rollers and stands are for the laying on of carbon I'd guess you wouldn't store them under the mandrel because they would have come on a truck on a pallet and you'd leave them on the pallet until they were brought to the production floor and they'd have to be installed on the production floor before the mandrel drum would be moved there which is made more difficult by the fact that they are currently supporting the drum in this location and there is no overhead crane (without disassembling the tent). And notice that they are not on pallets or railroad ties or similar, they are directly on the floor type surface in the tent.Quote from: Johnnyhinbos on 04/09/2018 04:52 pmAny guesses as to how thick the actual composite / insulation / etc will be?We should be able to get into the ballpark of the composite thickness if we had the maximum operating pressure of the tanks, we know the size.Quote from: aero on 04/09/2018 05:33 pmThe mandrel is heavy so it needs to be rotated to avoid deformation at the roller supports, just like a loaded rail car deforms the track and the wheels when it sits overnight.I'm not buying that steel deforms at stresses significantly below its yield strength at room temperature over an extended period of time. There doesn't seem to be any theoretical basis for that to occur. Perhaps the phenomenon you describe is due to the oil film in the bearings being crushed out or due to cold welding.
Quote from: OxCartMark on 04/09/2018 06:03 pmQuote from: Johnnyhinbos on 04/09/2018 04:52 pmThe stands I believe are more than just stands - they are rollers - some driven and some passive.I'll buy that and further add that the things that look like control stations below the rollers may actually be control stations for the rollers. However it could be that those rollers and stands are leftovers from the process of fabricating the mandrel in place there, not the ones that will be used to lay on carbon. Assuming for a second that the rollers and stands are for the laying on of carbon I'd guess you wouldn't store them under the mandrel because they would have come on a truck on a pallet and you'd leave them on the pallet until they were brought to the production floor and they'd have to be installed on the production floor before the mandrel drum would be moved there which is made more difficult by the fact that they are currently supporting the drum in this location and there is no overhead crane (without disassembling the tent). And notice that they are not on pallets or railroad ties or similar, they are directly on the floor type surface in the tent.Quote from: Johnnyhinbos on 04/09/2018 04:52 pmAny guesses as to how thick the actual composite / insulation / etc will be?We should be able to get into the ballpark of the composite thickness if we had the maximum operating pressure of the tanks, we know the size.Quote from: aero on 04/09/2018 05:33 pmThe mandrel is heavy so it needs to be rotated to avoid deformation at the roller supports, just like a loaded rail car deforms the track and the wheels when it sits overnight.I'm not buying that steel deforms at stresses significantly below its yield strength at room temperature over an extended period of time. There doesn't seem to be any theoretical basis for that to occur. Perhaps the phenomenon you describe is due to the oil film in the bearings being crushed out or due to cold welding.This phenomenon is called Creep and is generally only a consideration for metals when they are exposed to a continuous load at very high temperatures. So not applicable to rail cars or this tooling.
Quote from: Rabidpanda on 04/09/2018 06:18 pmQuote from: OxCartMark on 04/09/2018 06:03 pmQuote from: Johnnyhinbos on 04/09/2018 04:52 pmThe stands I believe are more than just stands - they are rollers - some driven and some passive.I'll buy that and further add that the things that look like control stations below the rollers may actually be control stations for the rollers. However it could be that those rollers and stands are leftovers from the process of fabricating the mandrel in place there, not the ones that will be used to lay on carbon. Assuming for a second that the rollers and stands are for the laying on of carbon I'd guess you wouldn't store them under the mandrel because they would have come on a truck on a pallet and you'd leave them on the pallet until they were brought to the production floor and they'd have to be installed on the production floor before the mandrel drum would be moved there which is made more difficult by the fact that they are currently supporting the drum in this location and there is no overhead crane (without disassembling the tent). And notice that they are not on pallets or railroad ties or similar, they are directly on the floor type surface in the tent.Quote from: Johnnyhinbos on 04/09/2018 04:52 pmAny guesses as to how thick the actual composite / insulation / etc will be?We should be able to get into the ballpark of the composite thickness if we had the maximum operating pressure of the tanks, we know the size.Quote from: aero on 04/09/2018 05:33 pmThe mandrel is heavy so it needs to be rotated to avoid deformation at the roller supports, just like a loaded rail car deforms the track and the wheels when it sits overnight.I'm not buying that steel deforms at stresses significantly below its yield strength at room temperature over an extended period of time. There doesn't seem to be any theoretical basis for that to occur. Perhaps the phenomenon you describe is due to the oil film in the bearings being crushed out or due to cold welding.This phenomenon is called Creep and is generally only a consideration for metals when they are exposed to a continuous load at very high temperatures. So not applicable to rail cars or this tooling.Given how much empty space is inside the mandrel, I agree. But I know they _do_ need to rotate similar-diameter steam turbine blades when _not_ in service at power plants in order to prevent deformations that lead to imbalance and bad resonance when they power up again.
It’s my guess that this mandrel is fabricated from invar, which is highly dimensionally and thermally stable. Not your father’s mandrel, this...
We should be able to get into the ballpark of the composite thickness if we had the maximum operating pressure of the tanks, we know the size.
I didn't understand until Wolfram's photo tweaking that there was an inner and an outer. I'm of the opinion that (as stated above) a custom winding head works the inner drum and the outer provides a clean environment for winding and an autoclave enclosure. So if its the inner we're talking about then I don't think the photo scaling that someone did above applies anymore.
How do you get the mandrel out, once you've wrapped the composite around it?
Quote from: sanman on 04/09/2018 08:09 pmHow do you get the mandrel out, once you've wrapped the composite around it?From what I've read, there are many ways, depending on your manufacturing process. For instance, you can inject air between the outside of the mandrel and the inside of the composite structure and use that air bearing to slide the structure off - that was what I was alluding to in my earlier post. Or you can cool the mandrel to fractionally reduce it's diameter (either from active heating during manufacture and allow to cool, or active cooling post manufacture). Then there are release agents. And some mandrels are meant to disassemble into smaller sections. When I toured the OrbitalATK facility in Promontory, UT prior to the QM-1 test fire of the SLS SRB, I _believe_ the mandrels used to cast the segments used this last technique - though not 100% positive I'm remembering this correctly...
Hey you, listen up! Read my latest @JECComposites interview article with Colin Birtles of @AscentAerospace regarding the company's launch of its HyVarC hybrid Invar and composite mould solutionshttps://twitter.com/aero_mag/status/982263038903382016
@SpaceX showing off the main body tool for the BFR 🤩🤩🤩https://twitter.com/AscentAerospace/status/983382489035980800