Machining fiberglass rods

[Andrew Schuetze]

Team 2745 is exploring the use of flexible fiberglass rods. As a 10 year mentor/coach ( founder 499) I have no experience in drilling or machining fiberglass of any type.

How likely will drilling a hole through the rod cause it to splinter and break?
Are there any fact sheets that would give some guidance such as 0.500 in round stock could accept a 0.128 in through hole axially...
The use of this rod will cause it to flex much in the manner of camping tent poles. I am thinking that a hose clamp will not give sufficient attachment over the course of the season.

As always is the case, any and all advice or suggestions are welcome, espcially from teams using non-traditional materials in their robot construction.

APS

[MrForbes]

You can drill fiberglass. The strength after you put a hole in it depends on lots of things..but a 1/2" rod with a 1/8" hole should still be plenty strong.

Beware of safety issues, use eye protection, a dust mask, and a vacuum. If you need to saw the material a normal saw blade will work, but will dull quickly. If you need to make a lot of cuts then try to use an abrasive blade, such as designed for cutting masonry.

[Dad1279]

Our Overdrive robot used fiberglass rods as part of the 'thrower', which had to hinge. We drilled a hole in a block of lexan, then epoxied the fiberglass rod in the hole, and drilled the 'hinge point' in the lexan block. It held up without issue all season.

[Tom Line]

Are you trying to bend the rod, or not?

You can drill it and it will splinter a bit. Your best bet is to wrap it in tape prior to the drilling. Drill with a very sharp bit, then when you're done remove the tape gently and coat the hole walls with a good epoxy to prevent further splintering and cracking.

If you're just looking to raise a lightweight hook up to the bar, you should be able to do that easily with .5".

Sometimes using a very thin (1/32 or 1/64) aluminum or brass sleeve and glueing it in place prior to drilling will prevent the splintering entirely AND keep the tube stable afterwards.

Edit: It's still good practice to coat the walls of the hole with epoxy even if you've sleeved it.

[Andrew Schuetze]

Thanks for the suggestions.

Correct that the rod will be bent to be in the 'box' and then released to raise a lift hook to the tower from a winch. Concerns are mounting the rod end to the robot base and then securing a release line to the rod to hold it in starting position. This attachement will release line in a controlled fashion. I like the idea of epoxy in both instances. I was already considering securing a capped PVC tube to the robot base and then inserting the rod and filling the tube with epoxy. We can then epoxy a ring to the other end of the tube.

[Tom Line]

Have you already tried bending the fiberglass? Depending on the epoxy and the layup of the glass strings in the tube, bending it 180 degrees in 38 inches might be too much for the material to take.

[Andrew Schuetze]

We successfully bent a multi-section tent pole replacement. It failed during a test that pulled it at a different angle and forced it onto a corner of the frame. It shattered at that stress point.

[DonRotolo]

Depending upon the way the rod is made, you may find that tiny splinters of glass fiber come off the surface of the rod - anyone rubbing a hand along the rod will find out in a split second, and remember it for weeks.

It may be valuable to coat the surface with epoxy, Plasti-Dip, or even electrical tape if this is happening.

If you do drill in, in addition to the advice above about epoxy in the hole, also try to select a spot that low stress. For example, at the tip it'll be fine, right in the middle where the rod bends most, it may be less so...