Dear all

Looks as though my brain has finally turned to mush. Pretty sure I could have worked this out with pen and pencil 50 years ago.

Kids grow up. They abandon the trampoline. The 2" steel poles that supported the trampoline are inevitably too good to abandon and so you pack them up and transport them across a few house moves in the certainty that you will use them creatively.

Numerous Norman Wisdom slips, trips falls and surfing across the garage floor episodes later the time has come to weld them into something of no practical value.

This is where the problem starts. Confidently convinced SWMBO that I could create a tubular duodecahedron using my new found welding skills and even more developed 'grinding the mistakes off' abilities. So ten tubular pentagons sharing vertices in a 3D configuration.

For the life of me I can't work out how to plot the cut lines or intersections on the end of each tube. If it was smaller section or wood I could rig up a drilling jig but gashing out 2" tube takes more grunt than the kit I have available. I do have a mill and a couple of lathes but set up for the cuts is dependent on working out the geometry which is defeating me. Hence a preference for paper templates, saw and grinder.

Enough rambling. Some assumptions.

• Each component part should be identical so I once the mark out is set it should be a relatively simple question of gashing the 30 pieces required with basic saw and grinder. Surely any pentagon viewed individually attaches to another identically? Or there a consideration around top and bottom halves that throws that assumption out?
• A simple pentagon wooden framework as a base will allow the parts to be held relative to each for assembly. The base layer first then flip that on its side/at an angle to add each upright in turn.
• Do that for a top and bottom and the two halves will join seamlessly with no need to bodge and hammer them into shape. What could go wrong?

It seems an interesting exercise but I can't for the life of me work out how to project the angles for the various intersects and then develop the bit of high tech paper to wrap around each end.

Creating a single pentagon in one plane is easy enough – diagonal cuts – and it would be possible to do a top and bottom that way but it will be inelegant to then tie in the other components 'overlapping' the corners. If that is the only realist route to success I will pursue that but ideally I'd like it to look decent so that I can dump it in the garden and call it 'art.' Then I can re-fill the space created in the workshop with more scrap to trip over . . . it keeps me nimble.

Finally the question! Is there an online tool that I can use to do the required projection?

Many thanks in anticipation. I ask more questions than I ever answer and always appreciate the help given. Once this is out of the way I have a few more queries lined up. Will post a picture of it once done.

Andrew Smith

Thanks Martin

That might be my salvation. Will that just invite straight cuts in each plane rather than faffing with projecting curves?

Surely it does??? That would be a simple jig to knock up.

A

Looking at Dave's image, which I have previously looked at on the net several times, it is now obvious how to go about this.

Thanks for the inspiration everyone. Wouldn't have seen the wood for the trees without your nudging. I think a plan has formed.

Regards

Andrew