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 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.
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-way brass connector and 2 short pieces (200mm) of 2020 extrusion. All held together with elastic bands.
Since taking the above photos I upgraded the nozzle support. I now use a fine adjustment level thingy (LP-64 Base with Bubble Level) with a 3-way brass connector supported by a plastic nozzle. I found the plastic nozzle was a perfect fit for the screw on the base and worked very well as a support. All I had to do was fill the top of the nozzle with hot glue to make a plug. The brass nozzle shown below is a regular 4mm barbed with an 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.
The connectors are small quick release connectors. With the nut removed the tube comes away fairly easy which makes filling and cleaning the bottles straight forward. The nut does not need to be that tight to get a a good seal.
Here are slightly heavier connectors. These have a larger nut and, I believe, are designed for higher pressure. They are exactly the same to use and are available in the same price range as the ones above.
Originally I wasn’t sure what connectors were suitable and bought quite a few different types. These are the cheapest I found but are designed for rigid tubes/pipes and not suitable for the soft PCV I use, however, if using rigid tubes these make a strong connection.
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.
DIY stand, very simple circuit.
Another DIY stand.
5V-12V 520 DC motor
I later had PCBs made and settled on a pump with a 520 motor. I run this at 12v which gives around 6 psi. Could be higher with a well sealed system.
At some point these will be available to buy.
I have very limited space and I try to make everything as compact as possible. If you have space then almost any air compressor will work, this doesn’t need to be very large, is likely to be more reliable (or at least no as fragile), and would also allow you to use higher pressures. Air compressors tend to be more expensive than the pumps in the photos above though.
I would not recommend aquarium pumps unless you can find a large one. Aquarium pumps tend to produce a decent flow but very low pressure.
I mostly use a range between 1 psi to around 3 psi and find any of the above pumps suitable. The main difference; the larger pump has a larger capacity per minute/flow rate; 13L per minute vs 5.5L per minute. Haven’t noticed if this makes a difference. I suppose if I were rapid firing the bottom nozzle it would make a difference.
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 hot with continuous use.
When using the electric pump, 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. You couldn’t use a ball valve with a sprayer bottle though.
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 pressure was at around 1 psi for the 1mm and slightly more for the 2mm nozzle and I had to increase the pressure 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 jet pressure can have a big effect on the shape of the collisions. For umbrella style shapes you need more pressure from the top and for cup shaped collisions you need more pressure from the bottom.
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.
Here are some other nozzles I have. These are larger and much heavier than the ones above with very similar performance. These were more expensive, around 5 times the price. They are, however, available in more sizes. The ones in the photo are 3mm, 2.5mm, 2mm, 1.5mm, and 1mm. Other sizes are available.
I have a whole load of different nozzles, most of which I will probably never get round to trying; such as the ones here. These are mini M5 nozzles and probably smaller than they may appear in the photo. The nozzles appear here with M5 to 1/8″ adaptors and then 1/8″ to 1/4″ adaptors.
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 needs to be as straight as possible. 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 more difficult.
In the following images the jet is leaning slightly forwards. This means, while the top drops collide nicely, 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 as it means the photo captures the shape better 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. Every time I retightened the nozzle it would move a little bit and it was very frustrating to get it in to the correct 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 hits. I make another drop and adjust the position of the nozzle repeating the process until the drop hits the nozzle fairly central (this is the same technique I use for regular drops when gauging the Worthington Jet). 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 the bottom jet around 2 psi for nozzles with 2mm openings and maybe 1 psi for smaller bore nozzles. One of the reasons for this is the mess. I live in a small apartment and use the dining table in the main room and so have to keep the mess to a minimum. A higher pressure means bigger splashes and different shapes but also means more mess.