Shoot From Below

Shoot from below is so called becuase a jet is shot up from below and the pressurised jet replaces the normal Worthington Jet. The main benefit is the jet is consistent and repeatable and means it is easier to get collisions and is is a lot better for more complex collisions.

I first tried shoot from below (SFB) a few years ago. I had a very simple set-up; pressurised garden sprayer bottle, a piece of tube and a valve. I played with it for a while, had mixed results and went back to regular drops. I always intended to try again and over time I bought various bits & pieces and accessories (far too many) for SFB but didn’t do anything with them.

Note: This is not intended as a getting started guide. It is more like an intermediate level look at Shoot From Below.

SFB water drop photographs

SFB has become more and more popular with the dropper crowd and I am now getting many questions and requests about it so I decided to dig out the parts and set it up and try again (this was a while ago. It took me a while to write tis post). The SFB set up I have now is a little more advanced than when I first started with the sprayer bottle.

Here is my complete set up, or at least the set up I use most often. The small frame on the right is the SFB equipment.

And here is the same set up with a high tech splash guard I invented 🙂


The SFB equipment comprises:
– air pump
– bottle to store pressurized air
– pressure gauge
– ball valves
– a second bottle used to hold the liquid
– a solenoid valve attached to the second bottle
– various connectors

Missing from the above photo is the SFB nozzle. This is a spray nozzle with a 2mm opening attached to a 3-war brass connector and 2 short pieces (200mm) of 2020 extrusion. All held together with elastic bands.

Since taking the above photos I upgraded the bottom nozzle.
The stand is a fine adjustment thingy with a 3-way brass connector supported by a plastic nozzle. I found the nozzle worked very well and the fit was perfect. All I had to do was fill the top of the nozzle with hot glue to make a plug. The brass nozzle shown is a regular 4mm barbed one. This inner opening is just over 2mm.

Both versions are free standing and are heavy enough that they do not move when making jets. Having them free standing means they can be moved easily to make small adjustments to align the jet with the drops.

And here is the latest version in use.

 

Air pumps

I bought a range of pumps to try (from small to large,) and from these there are 2 that I use, the pump in the photos above and a smaller one.

6V-12V 520 DC motor
I run this at 6V and at 6V it is very quiet.
The nozzle fits 4mm tube.
At 6V produces around 5 psi.

DIY stand, very simple circuit.

6V-12V 550 DC motor
I run this one at 12V and is it almost silent.
The nozzle fits 6mm tube.
At 12V produces around 11 psi.

Another DIY stand.

Pressure

I mostly use a range between 1 psi to around 3 psi and find either pump suitable. The main difference is the larger pump has a larger capacity per minute/flow rate; 13L per minute vs 5.5L per minute.
I tend to use the large pump simply because the hose size is 6mm the same as all the fittings I use. When using the smaller pump I have to either use a tube size converter or change the fitting on the bottle.

Caution: Pumps like these can get very hot with continuous use.

Setting the exact pressure is done using a manual ball valve, the more open it is the lower the pressure. This is not the most efficient method but works well with a constant pressure source such as a pump. It does means you hear the hiss of escaping air all the time though.

 

Nozzles

I have several sets of nozzles which I am slowly trying out. So far I like the 4mm brass barbed nozzle and the nozzles from car wash wheel trim jets.

4mm barbed brass nozzles


Car Wash Nozzle

As well as for other things, these nozzles are used for the jets that clean wheels in large car washers, they are available with different sized threads and with different sized holes. The below are 1/4″ NPT thread; 1.0mm, 1.5mm, 2.0mm, and 3.0mm.

The jet from the 1mm nozzle.

The jet from the 2mm nozzle. At the moment I prefer the 2mm nozzle.

And the 3mm nozzle.

The pressure was at around 1 psi for the 1mm and 2mm nozzle. I had to increase the pressure slightly to about 2.5 psi while using the 3mm nozzle. There is no rule for any of this so try different nozzle sizes and lots of different pressures.

The liquid used was a fairly thick mixture of water with Guar Gum. The sparkly frosted glass effect is achieved by over mixing (blending) the liquid until it goes frothy with lots of small bubbles and then back lighting. Xantham Gum can also be used.

Random Notes

The hardest part of SFB is getting the jet vertical. It is easy to have the jet shoot up but for really good collisions it should to be exactly at a right angles, or as close as possible, with the base. Once you have this you can then experiment with moving the alignment. For left/right alignment I have started using a graph (see above). This was posted on one of the facebook groups. Can’t remember who posted it but when I do I will add their name. Getting the jet straight on the front/back plane is a little for difficult.

In the following images the jet is leaning slightly forwards. This means while the top drops are in the same place the lower drop is not aligned with the jet and the splash is being pushed backwards. I actually like this, especially when shooting level with the collision but in this case it was a happy accident and not planned.

I like the first image not so much the second. In the second image the shape of the bottom collision is hidden and looks flat in the photo.

When I first started with SFB I had the bottom nozzle secured to the base and I found it very difficult to get the jet and the drops aligned. Everytime I retightened the nozzle it would move a little bit and it was very frustrating to get it in to position. I now have the bottom nozzle free moving and aligning it with the drop is a lot easier and quicker. A macro rail would probably make things even easier but I don’t have one.

To align the jet with the drops, I start by making a drop from the top and eyeballing where it lands. I then move the bottom nozzle to where the drop hit. I make another drop and adjust the position of the nozzle repeating the process until the drop hits the nozzle fairly central. I then add a jet and make very minor adjustments until I get the collision I want.

I use fairly low pressure and normally keep it around 2 psi. With a small bore nozzle maybe 1 psi. One of the reasons for this is the mess. I live in a small apartment and use the dining table and have to keep the mess to a minimum. A higher pressure means bigger splashes which means more mess.