Dremelfuge Stand V1

For an explanation of what a dremelfuge is and why we need to build one, please see our previous lab note "How do you spin things fast in the backcountry?" 

After 34 hours of printing, 1 hour of part-cleaning and threaded-insert installation, and about 20 minutes of assembly-- we have created Version 1 of the dremel stand! This is the part of the dremelfuge that will hold the dremel while it is spinning our sample tubes.

 

Dremelfuge, Dremel Stand, Version 1

When we set out to design our "Dremelfuge" we wanted to make something with these properties:

(1) does not spin things at eye level

(2) does not tear itself apart while spinning slightly unbalanced loads

(3) can be weighed down with environmental objects, like rocks or sand

(4) can be disassembled (ideally without tools) and packed relatively flat

How did we do?

(1) A bunch of smart scientists made a similar setup-- they designed a plastic device to hold tubes that attached to the part of the Dremel that spins -- we'll refer to this plastic device as a rotor. These investigators reported that the plastic rotor cracked while they were spinning it in the field. Because these scientists held the Dremel in their hands while it was spinning the tubes, the pieces of the cracked rotor flew towards their faces. We wanted to build ours from scratch because cracking is disastrous. Ours is designed to avoid cracking!

We have not yet designed the safety guards, so they aren't present in this version of the stand. The safety guards will protect the operator and the tent from being injured by a piece of the broken rotor ejected at high velocity. Because the broken pieces of the rotor are rigid, sharp, and would be going very fast, they resemble shrapnel-- and are terrifying. Before we design the guards we want to see which way a broken rotor will fly. Once we know this, we'll be better prepared to design guards that are sufficient for protection, appropriate for the most likely failure modes, and weight-efficient.

(2) Our second design goal was to try to make a device that can handle slightly unbalanced loads. Our calculations suggest that it is very important to balance the rotor, and we'll do our best to keep it balanced. Because we're putting pipettes in a backpack and taking them deep and dark places, they may become less accurate over the course of the expedition. Since we don't have a rotor printed yet, we haven't been able to test an unbalanced load.

(3) Our third design goal was to make an apparatus that could be weighed down and partially-stabilized with environmental objects. We installed threaded inserts at the base of each leg, which will allow us to securely attach a stabilization tray to the dremelfuge. We haven't designed the tray yet. We opted to make this a tray that we can fill with weight-- instead of an integrated weight-- so that when we are in the field, we can weigh the dremelfuge down with whatever is available, like sand or rocks. The threaded inserts look like gold dots in the picture below.

 

Threaded inserts to allow for the attachment to the stabilization tray.

(4) Our fourth goal was to design a stand that could be packed flat and assembled quickly, without tools. When we started to make the actual design, we realized that snap-together parts were probably not appropriate for the forces this stand could encounter. So, we decided it might be more reasonable to change the initial constraint to "assembled with a single tool" -- in this case, a hex key. Ikea style. Seemed good.

 

Using a hex key to turn the machine screws. The hex key is the only tool required for assembly.

For this first model, we didn't put threaded inserts in the holes on the disk because we were in a hurry. Instead, we used machine screws and nuts to secure the legs to the central disk. Small nuts. Nuts that are probably easy to lose. Nuts you wouldn't want to operate with cold or wet hands. Indoor nuts.

 

Nuts used to secure the hex screws.

Right now, the stand assembly packs down flat for pre-field airtravel, but the current version would need to be assembled prior to field-sequencing and shouldn't be assembled in the field. Since it won't fit inside a backpack, the stand would need to be lashed to the outside of a backpack. Given the densely forested nature of some of our sampling locations, we're a bit concerned that this might snag on branches.

Next, we'll design and test our own version of the part that attaches the spinning tubes to the dremel-- the rotor.