1/4 Scale ACA P-10 Siren

Update July 15th.... minor update to a few parts. new brush holder, the old one warped because it was under constant. new one has holes for M3 screws to support it internally laterally and from the bottom, pushing it up so it don't warp

Update March 7th..... Major update to the internals of the model

Update October 8th… I uploaded the wrong impeller, it had a test hub as opposed to the right one for the final product. If you downloaded, grab the impeller .obj again.

DISCLAIMER

The information provided here is offered on an AS-IS basis only. While I have efforted to make this helpful to you, I do not offer any warranty or guarantee of any kind regarding any aspect of this information. The information below may be subject to change without notice. The full risks as to the use of this information are assumed solely by the model builder. 

*** This is not a beginners project. You will need to fabricate some components with common tools and have some knowledge for editing objects in Blender or similar software ***

You will need….. (or equivalent) 

• https://www.amazon.com/dp/B07Z3FT4FD Select 4x10x4 size

• https://www.amazon.com/dp/B0BB2V8PNK

• https://www.amazon.com/dp/B085NDM5WV Select 40x50x6 size

• https://www.amazon.com/dp/B07P6X8QM1 Select 2.3mm to 4mm variant

• https://www.amazon.com/dp/B07SGDYW1Z Select 10x19x5 Size

• https://www.amazon.com/dp/B07G5873CP

• https://www.amazon.com/dp/B07KY88H3Q Select 3.9mm variant

• https://www.amazon.com/dp/B0D1RKK81D Select 10mm variant

• https://www.amazon.com/dp/B076H3XHXP 

• https://www.amazon.com/dp/B0D2XCH9R2

• M4, M3, & M2 Screws and Nuts

• Wire and Connectors

• Up to a 12 Volt Power Source… A 1500mA Wall Transformer is ideal

• A spring (get a door return sampler kit from home depot)

• ½ inch wide brass strip roll

• Wire and Solder

• Desolder braid

• Plumbers Tape

• Rubber Band

This was printed on a Neptune 3 Pro which is 225x225x300

M4 nuts need to be 6.83mm in size for the motor mounting

Holes are not set for inserts. the bolts will cut their own threads when you first insert them. Items that need to be securely secured will use nuts. Be careful with tightening, The threads will last if you don't overtighten. This assumes your slicer has it's X-Y hole and contour compensations set to zero.

The chopper and backing plate it mounts to are keyed so they can fit into each other and align… Pay attention to the chopper… mounting it wrong will cause the intake cone to oriented wrong. The indents on the intake should point to 12, 3, 6, and 9 on a clock face.

Holes that will receive bearings, depending on your slicer settings may be a smidge undersized. if that's the case you can ream the holes out with a screw driver that has a wide enough blade, but ream gently!

A counter intuitive approach is needed for the rotor. Set your slicer up to print with as little filament as you can. This will help mitigate any balance issues with the rotating mass. The super capacitor will handle the wind up and wind down. 

The worm gear drive will use one full length 100mm 3.9mm shaft. The hole in the gear is 6mm… There is a sleeve for this. you may have to tweak and reprint this sleeve several times to get it to fit right. you will need to print it extremely slowly or else your sleeve will come out all melty. The pulley that goes on the other end of the shaft is press fit and may need to be tweaked slightly too. Use some small washers to shim the gap between the pulley and bearing

you will need another shaft for the motor output from the back of the motor to the worm gear and you will need to cut it off at 40mm length

For the “brushes” I've used desoldering braid wrapped around the rings. See the attached photos to get a feel for how they are constructed. The spring mentioned in the parts list is used here. One spring can be cut and a loop bent out 90 degrees to make a new hook. There are grooved slots in the frame the holder mounts to. By moving back and forth, you can adjust the tension

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Ok now, the fabrication part… this model uses a custom ring and “brush” setup for the collector rings. there are two pieces, the slip ring holder and the retainer ring which needs to printed X2. Setup your slicer to print the rings as thin as you can since we will need to bend them to slip them inside the holder.

Take that brass strip roll and solder a good length of stranded wire on the end of it. Fan out the wire so it's as thin as possible. You will need a good source of heat since the brass will soak up a lot of it. I used a small torch. Once that's done measure about 10 mm from the solder joint and put a 90 degree bend in the strip and insert it, wire first through a slit in the slip ring holder. With the fulcrum of the bend up against the edge of the slit, finish the bend so that wraps around the slit completely. The wire we just soldered SHOULD NOT be facing the inside channel of the holder.

Wrap the strip around the holder so that it fits into the channel, once you get it wrapped around all the way, make see where it meets the slit… now go back to where it's just before meeting the slit and make a note of that spot and put another 90 degree bend into it and cut off the strip about 15mm past the bend. insert that bend into that slit and push it in and then complete that bend like the other.

If you got it right the ring you just made should be nice and snug. Repeat the process for the other ring.

Now the two retainer rings will fit inside the holder and make it easier to get the entire thing on to the turntable, by printing them thin we can bend them to slip them inside the holder. Notice how the retainers are notched. We are gonna route our wires so they go into those notches and our retainers should sit inside the channel for each ring. If the brass strips are proving stubborn, you can use pliers to help them conform the holder. 

Make sure also that the notches in the retainers line up. Next step is to take the finished assembly and insert it onto the turntable. The turntable has a keyway in. Put the wires though the keyway and line up the notches to the keyway and push it on the turntable. In the base of the table is another hole to run wires out of. See the photos below for how it goes together

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I've changed to using a press fit hub to mount the rotor. the hub presses onto the coupler and then rotor goes on the hub and secured with M3 screws and nuts. The change will let you get tolerances better adjusted for your printer and if you mess something up with the hub you won't need to reprint the whole rotor.

Now that we have the rotor hub made we need to mount it onto the smaller coupler that goes on the motor shaft. There's gonna be a little slop due to loose tolerances so what we're gonna do is shim that out by wrapping the the coupler with plumbers tape. This doesn't need a really thick wrapping, When putting the hub on over the tape, if the tape starts smearing and bunching up, you've put too much on. You might actually win the tolerances lottery on Amazon and not need the tape at all.

Tightening down the set screws on the hub needs to be done gradually. Don't torque one down really tight and then do the other one, it'll make it wobble. 

To line up the rotor we need to take 6 of those 6.83mm M4 nuts and insert them into the conveniently shaped hexagonal shaped holes in the motor mount plate. to do that take an M4 bolt and tighten it down until it pulls the nuts into the recesses, then back it out until the end of the bolt is flush with the nut. 

Now insert the motor with your rotor attached into the holder. leave the shield on the motor attached and slide it so it covers up the vent holes by the brushes (this motor is not gonna be stressed enough to make any heat). Line it up so the ports in the rotor and chopper align, then turn the each of the six screws so they're just starting to grab the motor body, You can set this down on the table so you have something flat to work on for this part. 

A power supply with voltage control will come in handy here… Balancing the rotor needs to be done through trial and error. The outer ring on the rotor has holes around the perimeter for tiny m2 screws. After you get the motor mounted you need to spin it up without the chopper to see how it bad it will vibrate. You'll need to insert a little m2 screw into a hole on the outer ring and spin it up gradually to to see how the vibration changes. Repeat with the screw in different holes and leave it in the one that gives you the smoothest operation

Alignment time! First mount the chopper and secure with nuts and bolts. NOW THIS IS THE TRICKY PART… PATIENCE IS KEY HERE… Notice how you should have three sets of bolts clamping the motor case at the back and front. By turning those screws we are adjusting the placement and tilt of the rotating assembly. You need to adjust each screw to center the rotor up. For each screw you tighten on the front, you need to loosen another one on the front, same for the back as well. The assembly will move in the direction that the screw is pushing it. You can check for scrapping by gradually spinning up the rotor with the power supply.

As an alternative to a variable power supply, you can use the adjustment screw on the power module you will use later to slowly spin up the rotor when doing balancing and alignment. Make sure to back out the adjustment screw(s) all the way

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A word about power regulators, you get them from amazon cranked up by default to full power, they will need to be turned all the way down using the adjustment screws, use a meter to measure. The completed project using the parts here will drawn around 2 amps from your power supply if it outputs 12 volts while running an alert. Starting current will be about 7 amps.

The motor should have a positive terminal marked… this get positive voltage!

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Here's the power setup. A separate box for holding the power regulator will be printed and mounts to one of the legs. While simpler, this can suffer from pitch problems because the power regulation happens before the slip rings and the whole setup in this config is very sensitive to the electrical continuity of the rings. To do this setup you'll need…

• https://www.amazon.com/dp/B0D2XCH9R2

• https://www.amazon.com/dp/B0BDR19JT3

The power regulator used here is capable of both current and voltage regulation so no special considerations are needed for charging the supercap. Set the regulator to output 3 volts and then adjust the current as necessary for proper pitch. Don't crank the voltage up and use the current regulating capabilities for pitch control, if the motor goes open circuit you could end up blowing up the supercap.

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There are 3 decals to print if you want. Each different element of the decal will be 5 layers deep on printing and if you have multicolor capabilities, you can simply change colors every five layers. If you don't have multicolor, you'll need to figure out how to pause the print cleanly so you can change filament. 

For my Elegoo, what I did was slice in Cura and edit the gcode file to play a long beep after the right layer. While the beep was playing, I remove the filament from the head and run-out sensor which the printer will notice and give the prompt to load filament. 

If you've read this to the end, I applaud you. Have fun!