@ravi31 Ravi

Hi
We thought to tinker with bamboo as material and create structures to re-organise the existing makerspace space.
The task of today is to figure out the joint mechanism with bamboo as structure.

We got some 10 ft+ long solid bamboo. Started with cutting it into smaller lengths. We used the circular saw to do that.

Here is close up view



@vvcstemplay Vickram Crishna

Pipe clamps are an inexpensive and simple method for binding bamboo, since they prevent splitting of the bamboo fibres, which extend longitudinally with the stalk. They look like this, and come in many sizes to suit convenience.



@jtd Jude T Dsouza

We need to attach at 90 ^o. Would be absolutely wonderful if we could spot weld two at 90 ^0.
And a third for vertical.



@vvcstemplay Vickram Crishna

My guess is that 3 way bamboo holders would be fairly easy to fabricate, indeed, not to mention cheap. Make jigs, and it will be possible to build as many as are needed, with good accuracy.



@ravi31 Ravi

So, here is a brief pictorial summary of yesterday’s work

Trim the bamboo pieces according to requisite sizes

Drill pilot holes, and screw the pieces together with handheld power screw driver using self-threading screw !


Here is the close up of the joint and one side of the frame

Here is the one side of the frame

We couldn’t complete the frame yesterday since the screw size was shorter than expected. Also, the screw was too brittle and it broke. Will get newer ones and will share the progress soon!



@ravi31 Ravi



@jtd Jude T Dsouza


This one seems to provide the most aesthetically and functionally.
Rack / Display / Work table
Rigidity



@vvcstemplay Vickram Crishna

I don’t want to be a wet blanket, but sheet metal screws work loose in bamboo, especially for a structure like this. Jude’s idea of welded clamps will be far more sturdy and long lasting.



@G_N Nagarjuna G

I also think so. When the clamps are ready the same bamboo can be repurposed for that, since the damage done to the bamboo throiugh screws is not much. Also, this is helping us to learn Structural Engineering 101.



@jtd Jude T Dsouza

Not sheet metal screws, nut and bolt. We tried sheet metal but did not use it.



@jtd Jude T Dsouza

We learnt a new method to keep one face of a bamboo stable.
While drilling holes along the length maintaining a stable reference line along the length is a very tricky task. We found a worker making a ladder using an utterly simple tool to do the above.
He makes a 25 x 25mm square hole on the bamboo. He then inserts the handle of a mallet like tool into the hole and wedges it with a shim. The bamboo now rests on the mallet always presenting a single surface to work on, thus preventing the rungs from spiraling out of alignment.
Very effective.
One could make the handle on a disc and have it rotating, to provide capability to make cuts and holes at precisely offset angles along the circumference. Dont know if such a tool exists elsewhere.

.



@ravi31 Ravi

Here is the update for the day
The complete frame looks like this…We later realized that if we would made the triangular frame with ply beforehand, it would have been a much easier process to make the stand.

What’s next?

  • Completing the shelf
  • Revamping the design to function as a standalone, mobile, modular and cost-effective workstation.

Update (23 Dec 2019)



@jtd Jude T Dsouza

https://grail.cs.washington.edu/projects/carpentrycompiler/

Our carpentry compiler converts high-level geometric designs made by users to low-level fabrication instructions that can be directly followed to manufacture parts. The compiler performs multi-objective optimization on the low-level instructions to generate Pareto-optimal candidates



@vvcstemplay Vickram Crishna

Again, the use of an external clamp means this step becomes redundant. And clamping a set of clamps together to weld them at accurate angles, repetitively to make a set of identical clamp assemblies, is also much simpler than drilling along a lengthy rod.

Using the nut/bolt is far better than my misreading thought that it was a sheet metal screw. But the weakness here is not the threading, it is the drilling itself. This would not be a problem per se using wood, but bamboo is a grass. The fibers are not strongly cross linked, so splitting them in any way leads to stress in their bonding.



@G_N Nagarjuna G

Yesterday we saw a metal scaffolding done at the centre, installed for painting of the tall roof. They have used two clamps which are not welded together, instead used a tough rotatable joint, more like a flexible revet. This design helps to join two rods at any angle.



@jtd Jude T Dsouza

Clamps provide a compression joint. Perfect for bamboo.
I will get hose pipe clamps tomorrow and investigate the best method for creating a right angle joint.



@G_N Nagarjuna G

We only need to join the two clamps, no need to keep them at right angles.



@vvcstemplay Vickram Crishna

As Jude pointed out earlier, there is a need to join 3 rods, with accuracy, repetitively. This needs a fixture to simplify the operation, hence the welded clamps.

One really useful lightweight assembly is a skeletal roofing structure made of repeating tetrahedrons, where the accurate clamp will make assembly almost trivial.

The flexible clamp joint might be used for different assemblies, such as easy to erect but reliable and sturdy tents and wigwams.



@jtd Jude T Dsouza

+1.
We can prototype a few welded clamps. Then outsource it.
There is a manufacturer in Pune who makes clamps for pipe structures.
Wonder if he could be induced into making a tetrahedron clamp as a standard product.



@vvcstemplay Vickram Crishna

I was thinking, if the prototype roof is built, it could be used to erect a rapid build temporary shamiana in the campus to inaugurate the proposed new exhibit in the hall.

And the roof will provide an excellent support framework for a wired very low cost distributed sound pa system for the event.