How to Make a Flux Capacitor From Back to the Future.




Introduction: How to Make a Flux Capacitor From Back to the Future.

After Watching the back to the future films again, i thought to my self "i could make a flux capacitor, it would go nice with my hover board"

This instructable is how i made my Flux capacitor from scratch. there are probably better ways to make or at least different ways to make it.

Please read the whole thing as i may have missed some info out on what is needed on the next page.

If you like it could you please vote for me in any competition it is added into (that is if you think it deserves it) please do, Thank you.

Step 1: Research.

I researched the Flux capacitor by googling it and looking at screen grabs.

And to be honest the majority of photos on the internet are other peoples replicas of the props and them and some screen grabs and just watching the film are what i used.

Step 2: Tools and Materials.

**** This list is probably not everything needed or that was used to make this project, please read the whole thing before starting it. **** Also not everything listed is pictured. ****


Laser cutter.

Line bender

Files and or sand paper

Knifes, cutting tools or razors.

Straight edge or cutting ruler.

Soldering iron and solder

pliers and wire snips.


Perspex, 5mm, 3mm and 2mm

Perspex tubes 12mm

perspex ball 19mm

styrene tube 7mm

Acrylic rod 5mm. (to fit inside the 7mm tube above)

warm light LED 5mm

circuit wire.

1mm silver garden wire.

3mm piano wire or rod.

black 2mm cable (detail decoration)

Rubber window seal

3 core electrical cable

Yellow heat shrink (large enough to go round the 3 core cable)

small PVC elbow joints from fishtanks.

Glues. super glue, solvent glue and 5 minute epoxy.

Spray paints of many colours.

paper and printing materials.

Running LED Circuit board kit.

Step 3: Making the Solenoids. Part 1.

To make the solenoid base i used the 5mm perspex (doesnt matter what colour as its going to be painted)

the solenoids are 30mm tall and around 50mm across. with a central hole and two little holes for terminal points and an oval shape for the wires.

There are three Solenoids in the capacitor so you will need to make three of everything.

Six layers of 5mm perspex for each solenoid are then glued together.

(i forgot to take a photo of the next bit)

i cut a 95mm x 20mm strip with rounded ends, with a small hole in each end, out of a 2mm perspex.

using a line bender i bent the strip into a shape that resembles an n with little feet. _n_

and the middle section was then headed and curved to match the shape of the solenoid. (see the pictures)

i bent one of the feet on two of the mounting brackets to match the look of the film.

then glue the mounting bracket to the solenoid.

Now its time to paint!

Paint the solenoid with plastic under coat then a coat or two of 'metallic gold' which looks like brass.

while the paint is drying i made up some stickers that looked like the label from the real solenoid, i then printed it off and glued it to the dry solenoid.

Step 4: Making the Solenoids. Part 2.

To make the terminal posts I cut out 6 nut shapes (hexagon shape) with a 7mm hole in the middle out of the 3mm perspex.
These are to mimic the look of a nut used to secure the terminal posts.

I cut the 7mm styrene tube in to 15mm long lengths, again 6 of them, and i also cut the 5mm acrylic bar in to 25mm lengths, once again 6.

These 3 parts will be combined to make the terminal posts.

To do this, first i put the hexagon on the 7mm tube and glued them to the bottom.

I then inserted the acrylic bar inside the tube, leaving 5mm sticking out the top and bottom of the styrene tube.

Paint the whole terminal posts a metallic silver, once they have fully dried (metallic paint takes a little longer to dry than other spray paints.) use some black electrical tape cut in half length ways (7mm wide.)to wrap around the wider part, the styrene tube, to make it look like an electrical component.

Once you have them fully constructed its time to attach them to the solenoids.

I glued the posts into the two holes in the solenoids when the glue had dried i cut some (i think it was three core headphone cables, from my scrap draw) wire to a length of around 35mm long and i stripped off one end and split the internal wire into two bundles. These two bundles were then glued to the top of the terminal post and the other end was just inserted into the oval hole in the solenoid (you don't need to glue them they will hold in place but you can if you want)

Do this to all 6 posts. and then you have the solenoid bases complete.

Step 5: Making the Solenoids. Part 3.

The solenoids in the film have a glass tube structure running through and extending out to one side of it.

To make this I used the 12mm perspex tube and the perspex ball.

I cut the 12mm tube into three parts (x3) 1x 70mm, 2x 15mm.

i rounded one end of the 70mm and one of the 15mm tubes using files and sand paper. The sanded parts were then polished them to make them clear again.

I sanded/filed down the ball to have a flat side the was the size of the tube (12mm) using this one sanded side as a reference point i then sanded another flat part at right angles to the first side. These will be the flat surfaces that the tubes with the rounded ends will be attached.

the third 15mm tube will be attached opposite the smaller tube with a rounded end.

I glued the 70mm to one flat side of the ball. this will be the part that extends out the side of the solenoid. Then i glued the 15mm tube with the rounded end to the other flat side of the ball this will be the top of the glass structure, the last 15mm tube will be glued to the bottom of the ball opposite the short rounded tube. this bit will go in to the hole of the solenoid so it doesn't need a flat surface but if you want to you can.

once all the tubes a have been glued on and the glue is dry i cut a length of 1mm wire into a straight length of 85mm and glued it into the the tube so it extends out of the 70mm tube.

Then the non rounded tube goes into the hole in the center of the solenoid. i didn't glue it in at this point as i was waiting to get all the other parts made before the final gluing.

Step 6: Making the LED Light Bar.

The Solenoid glass tube that extends out sideways has a light bar underneath it. In the film the light bar phases from the solenoid to the center of the Flux capacitors Y shape.

To make this part i cut a a rectangle with one sloping side. the shape is 30mm tall ~(same as the solenoid) and 75mm on the long side (bottom) and 60mm along the short side (top)

I cut these shapes out of the 5mm perspex and doubled them up. making the shape 10mm wide.

Once i glued them together i marked out where i wanted the LEDs to sit to light up the bar. the first mark was 6mm from the flat edge and then the next three were 16mm apart. i then drilled a 6mm wide hole into the acrylic around 4mm deep. Do this to all three light bars.

I then sanded all the narrow sides of the light bar, to give them a frosted look, and to aid the light to diffuse through the bar.

when the edges of the light bars i used some silver plumbers tape on the large sides of the bars. This gives the side a reflective look and stops the light from escaping sideways.

Step 7: Making the Case.

The case of the original Flux capacitor was made from a STAHLIN J1210HPL enclosure. and seeing as they sell for around £40/£50 and i didnt have / want to spend that on this i decided to make one.

The box i made is 270mm wide and 320mm tall and 125mm deep.

The lid for the box (which is the section to mimic the original prop.) is 290mm wide and 340mm tall with radius on each corner. The window in the lid is 250mm tall and 200mm wide with a 45mm radius on the corners.

I drew up the box in Adobe illustrator and cut out out of the 3mm and 5mm acrylic. the sides are 5mm and the base is 3mm and the lid is two layers of 3mm acrylic.

Build this box in your favorite way.

I made the lid two layers of 3mm as i wanted to build in the hinge. I did this by making some holes in the bottom layer of the lid into which some little plastic tabs with a 4mm hole were glued (see pictures) i also placed some plastic tabs with holes in them in the left hand side of the box edge, that lined up with the lids tabs, this allowed me to feed a metal rod through all the holes to create a hinge. (you can buy a hinge and attach it to the box and lid if you want.)

I placed some 3mm Acrylic spacers into the internal corners of the box to hold up a sheet of plastic which will hold all the components of the flux capacitor, the electrics will be hidden under this level and the LEDs will poke through and go into the light bars made in previous steps.

This sheet of acrylic had the positions of the solenoids and light bars etched into it and also had holes for the light bar leds to poke through and some detail holes, in a little arc on the right hand side. There are also three large holes for the wires that attach to the top of the solenoids to go through.

I painted the whole box with plastic primer and a dark grey to match the films.

In the picture i have placed the solenoids in the box to show what it will look like when its finidshed.

(I forgot to take pictures of this bit.) I installed the rubber seal to the opening in the case lid, I didn't glue this in or use sealant. I then pushed the window section (cut from 3mm clear acrylic 5mm smaller than the opening) in to the seal from the back and lifted and moved the seal until the window was securely In place.

Step 8: Making the Lights.

I purchased a Chasing LED kit board on ebay. The one i got was for a circle of chasing LEDs but i wired the LEDs in sets and made them light the light bars in the sequence from the film.

First i constructed the Kit circuit board following the instructions from the kit but leaving the LED out of the circuit, instead of wiring the LEDs in i soldered some wires in their place. (these will attach to the sets of LEDs that will go in the light bars.)

the LEDs were wired into four sets of three as there are four lights in each LED bar and there are three light bars.

The LEDs are set to flash in order. The closest to the solenoid is LED 1 and the closest to the center of the Y is LED 4.

Once the LEDs have been wired into the sets they are then soldered to the circuit board and the rate of flashing is adjusted using a little variable resistor which you adjust with a small screw driver.

When i had done all the soldering i glued the LEDs into their holes. (i numbered the holes on the back to make sure they went into the correct places.)

Step 9: Making the Jump Leads.

The jump leads are the parts that connect from the top of the glass tube in the solenoids to the main detail board through the three holes.

These were originally spark plug leads, which you can still get but they are expensive and come in packs of two, so i would have had to buy two packs and that was far too much money to spend on a bit of fun prop.

I started with the yellow leads. i looked in my local hardware store to find yellow electrical cable but couldn't find it so i just got some regular three core power cable. I then fed this cable into some yellow heat shrink tube. Then i heated the tube and it shrank to the size of the 3 core cable.

I couldn't just use the yellow heat shrink as it would kink as i bent it and not curve correctly.So with the 3 core cable inside the heat shrink it means the cable can be bent and not kink up, its a smooth bend.

To make the caps for the leads i found some fish tank airline or irrigation tube Elbow joints. These were about the right size and came in a pack of 5 so it was perfect.

I painted the Elbow with plastic primer and then a red to match the colours in the movie.

(i forgot to take a photo of trimming the thin section of the L joint) I cut the thinner section of the L joint off so it would look better.

I glued the yellow cable into one end of the elbow joint, then placed the elbow ontop of the glass tube coming out the top of the solenoid and measured the cable to the hole in the base. i cut the wire slightly longer so there is some play in the bend so the curve can be made longer or shorter.

Step 10: Little Details.

The beauty of a prop is in the little details.

In the movie the Flux capacitor has some labels on the front of the case and they are made out of what looks like an embossing label maker.

I do not have one of these so i had to do the next best thing and fake it.

I googled free Embossed font and found one and made the labels on the computer.
I found out that the strips used to make the embossed labels comes in two sizes, 9mm and 16mm by looking at the pictures i think the 16mm is too big so i made them at 9mm wide.

I printed them off and cut them out, using some double sided tape i stuck them to the front of the Flux case.

i left the one on the glass off until all of the parts are installed as i want it to line up correctly

Step 11: Final Assembly ​

Once all the separate parts of the Flux capacitor have been made its time to construct it all.

The main detail board is where most of the details will sit.

I painted this board slightly darker than the rest of the box.

When the paint had dried i inserted all the LEDs into the back and made sure they all worked and flashed in the correct order. When they were all in the right place i glued them in using hot glue to make sure they wont fall out.

I turned the board over and glued the light bars over the LEDs, I did this before gluing the Solenoids down so i would be sure that the light bars would fit over the LEDs sticking out. incase the solenoids moved when the glue is drying or i put it in the wrong place, meaning that the light bars wouldnt fit.

After putting the light bars in i glued in the solenoid bases behind the light bars. Paying attention to th placement of the bent foot on the solenoid mounting brackets.

When the bases are in place its time to glue the glass tubes in place. I used hot glue and just squirted some into the hole of the base and then pressed the tubes in place and aligned them with the light bar.

When the glue holding the glass tubes in place has set its time to add the leads. i glued the elbow joints on top of the glass tubes with hot glue and then fed the yellow cable through the holes. then on the under side of the detail board i hot glued the cables in place to stop them slipping out of the holes.

When the main parts were in place i closed the lid and attached the last front sticker so its in line with its placement in the movie.

Step 12: Finished Flux Capactior.

Once you have put all that parts together its time to get Fluxing and display your Flux Capacitor in all its glory.

I am going to put mine with my hover board.

Thank you for spending your time reading my instructable. I know its a long one.

If you have any questions please ask and i will do my best to answer them.

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Participated in the
Halloween Props Contest 2015

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    7 years ago

    Any chance you could attatch your laser cutter files?

    backwards lamb
    backwards lamb

    Reply 7 years ago

    erm, there isnt much to the files its just lots of circles and rectangles etc. i will have a look and see if i can find the files.


    Reply 3 years ago

    are those files available ?


    Reply 3 years ago

    No. See above comment from author.

    Just4Fun Media
    Just4Fun Media

    7 years ago

    Very nice replica! It is one of the most realistic ones that I have seen! How long did it take to build?

    Have a great day! :-)

    backwards lamb
    backwards lamb

    Reply 7 years ago

    Well it was a just at night build really. But actual build time was probably a couple of days. Also waiting for the elbow joint to come from Asia was annoying.
    But it was probably two weeks of just at night a 3 days a week. :) hope that makes sense.


    7 years ago

    Awesome!! Voted!

    backwards lamb
    backwards lamb

    Reply 7 years ago

    Thank you. Share it too if you like ;)


    7 years ago

    this is,,,AWESOME!!!