Round Tube/Pipe with Tension Cable Core
Round Tube/Pipe with Tension Cable Core
(OP)
The design challenge:
There is a fabric roll that needs to span a large distance unsupported (about 80 feet). The client has asked for the roll weight to be minimized since the quantity and weight of the fabric is very small in comparison (roll size < 5" dia; preferably carbon fiber tube).
The idea:
The roll has ends caps to which the internal cable would attach. Tension would be applied to the cable inside the tube to support the roll and reduce deflection. Containing the tension within the roll eliminates the need for robust horizontal supports. Multiple cables could be an option.
This concept is new to us and we wanted to see if anyone else has experience doing this or know of instances where something similar has worked.
What design challenges do you foresee? Is it feasible?
Thanks,
There is a fabric roll that needs to span a large distance unsupported (about 80 feet). The client has asked for the roll weight to be minimized since the quantity and weight of the fabric is very small in comparison (roll size < 5" dia; preferably carbon fiber tube).
The idea:
The roll has ends caps to which the internal cable would attach. Tension would be applied to the cable inside the tube to support the roll and reduce deflection. Containing the tension within the roll eliminates the need for robust horizontal supports. Multiple cables could be an option.
This concept is new to us and we wanted to see if anyone else has experience doing this or know of instances where something similar has worked.
What design challenges do you foresee? Is it feasible?
Thanks,
DFLewis
www.phoenix-engineer.com





RE: Round Tube/Pipe with Tension Cable Core
What is the permissible deflection at the center?
Does the roll have to rotate? If not, the cable should be at the bottom side if this has any chance of working. An 80' span seems awfully long for a 5" diameter cylinder. I think putting a tension cable inside would do more to contribute to Euler buckling than straightening the thing out.
-handleman, CSWP (The new, easy test)
RE: Round Tube/Pipe with Tension Cable Core
- 12" in the center is a lot but probably on the edge of what we might find acceptable.
- Yes, the roll needs to rotate and be driven... approximately 1000 in.lbf. of torque applied.
I agree with the buckling concerns.
DFLewis
www.phoenix-engineer.com
RE: Round Tube/Pipe with Tension Cable Core
Also, with that kind of driving torque and such a long "shaft" you are going to need to consider twisting of the tube pretty carefully.
-handleman, CSWP (The new, easy test)
RE: Round Tube/Pipe with Tension Cable Core
the inflation may be able to deploy the cover ??
RE: Round Tube/Pipe with Tension Cable Core
Or could you run several tensioned smaller cables from end to end inside the tube along the id?
Griffy
RE: Round Tube/Pipe with Tension Cable Core
An internal prestressed cable will only make deflection worse as Handleman pointed.
RE: Round Tube/Pipe with Tension Cable Core
Only difference in principle I see is that the sail is inside the mast which is the object in compression. I think it would sag quite a bit in the middle if suspended horizontally. Companies that make them are Reckmann, Profurl, Seafurl, Harken. Not exactly what you were looking for but might give you some ideas.
RE: Round Tube/Pipe with Tension Cable Core
E.g. say:
-end diaphrams with cable anchors clustered near the center
- a midspan diaphragm with only notches around its periphery
- quarter- span diaphragms with holes at, say, 5/8 radius
- and so on,
so that the cables are each tensioned over a series of edges approximating a half-sine.
Ok, maybe that's what (s)he meant to say anyway.
Just as in sailboat rigging, rods would probably work better than cables, because cables (or their terminations) stretch more.
Mike Halloran
Pembroke Pines, FL, USA