Measuring clamping forces
Measuring clamping forces
(OP)
I have a quick question concerning measuring clamping force and the use of temporary fasteners and was hoping someone could provide some helpful tips.
Quick synopsis:
I have a contoured composite skin that is installed onto 6 metal frames. Before permanent installation, the skin must be mated with the frames and gaps measured for the possibility of liquid shimming. Currently, we always shim. This process takes a whole day and I would like to remove it if possible. Per a spec, I am allowed a particular amount of clamping force every 8 inches. If I could somehow figure out how to measure the force when using Clecos to hold the skin onto the frames, I could potentially minimize all gaps so much that we do not have to shim.
My research:
SO far I've thought of and have been recommennded a couple options:
1) Use sand bags (I don't like this because it's inaccurate and shoddy)
2) Use force washers w/ Clecos (I've looked into this but since the skin is contoured I do not think the washers would work properly, not to mention the process of using them would take a considerable amount of time. I'd need about 50 washers to hold the entire skin onto the assembly)
Anyone have any suggestions for a new process engineer in the aerospace industry?
Quick synopsis:
I have a contoured composite skin that is installed onto 6 metal frames. Before permanent installation, the skin must be mated with the frames and gaps measured for the possibility of liquid shimming. Currently, we always shim. This process takes a whole day and I would like to remove it if possible. Per a spec, I am allowed a particular amount of clamping force every 8 inches. If I could somehow figure out how to measure the force when using Clecos to hold the skin onto the frames, I could potentially minimize all gaps so much that we do not have to shim.
My research:
SO far I've thought of and have been recommennded a couple options:
1) Use sand bags (I don't like this because it's inaccurate and shoddy)
2) Use force washers w/ Clecos (I've looked into this but since the skin is contoured I do not think the washers would work properly, not to mention the process of using them would take a considerable amount of time. I'd need about 50 washers to hold the entire skin onto the assembly)
Anyone have any suggestions for a new process engineer in the aerospace industry?





RE: Measuring clamping forces
(just a random picture search selection, not a product recommendation)
Are you guys riveting composite skins to metal frames? The designers aren't ready for the big leap to plastic?
Have you not noticed that one of the major advantages of composite external surfaces, ie. smoothness, has just been throw out by riveting the structure?
STF
RE: Measuring clamping forces
mind you now the OML will conform to the frames whereas currently i think you're tooling the OML (like Piaggio do for their Avanti turboprop), so this will affect the outer surface (mostly the appearance, little impact on drag).
Quando Omni Flunkus Moritati
RE: Measuring clamping forces
I would be very wary of eliminating the sealant step. Your suggestion of measuring loads and skipping the step may work for most cases but Murphy says that there will be some cases where your measurements and the relevant geometries of panel and frame do not align. The cost of repair (or replacement as was the case I discussed above) far exceeded the savings gained.
Regards
Blakmax
RE: Measuring clamping forces
Then find a spring which bottoms out out your desired maximum force and place this between the body and the thumbscrew.
If you can pull the panel without the springs bottoming out you know you are within the limit. You can even measure the force with a feeler gauge between 2 spring coils
RE: Measuring clamping forces
David Baird
Sr Controls Designer
EET degree.
www.afctool.com
RE: Measuring clamping forces