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“The latest part of your build-up DeLorean model is the Mr. Fusion fuel processor that Doc Brown adds to the time machine for the final scene of Back to the Future. It also includes the reactor disc seen in the rest of the film.”

I want to point out here that Eaglemoss no longer supplies the three ‘CP’ screws shown in the parts list. The six ‘DP’ screws listed are packaged as CP screws. Read on to find out how to use them correctly. And, if you are interested, I have a dedicated page all about The Screws that details each type of screw the build will use.

This issue also contains a few of Mike Lane’s excellent mods, so it is going to be a little longer than others!




  • Drive Time: Model Instructions
  • The Real Doc Brown: Michael Scheffe, who built the original car
  • Finding Doc: Casting Christopher Lloyd
  • A Time Traveler’s Guide: Einstein the dog


The Reactor

Steps 1-2

Fit the Reactor Disc 3 (yellow cap) in the center of the Reactor Disc 2. Turn the Reactor Disc 3 so that it locks into place.

Fun Fact: On The ‘A’ Car, this center cap was custom made, but the disc was a stator vane from a military jet turbine engine. When I first received this Issue, my yellow cap had numerous nicks in it exposing the black plastic underneath. This was poor quality control, so I reached out to Eaglemoss to fix it. See my Whoops #1 post about my experience contacting Eaglemoss Customer Service. This image shows the replacement cap:

Just like everyone else, I found that this piece does not lock into place at all and will easily fall out. There is only one ‘key’ peg and they really should have used two pegs like shown in the instructions. Luckily, by the time this gets mounted on the car, you shouldn’t be turning it upside down any more.

Step 3

Place Reactor Disc 1 on top of the previous assembled part, flip it over, and fix into position with two (2) AP screws.

The instructions say Reactor Disc 3 (4C), but it is really Reactor Disc 1 (4A).  There is a peg that orientates the two so that they can only go together one way. Do not put the screws into the raised holes, they are for the next step. On the real car, this piece was a hubcap from an old Dodge Polara:

Step 4

Fix the transparent Reactor Disc 4 to the center of the assembly using two (2) CP screws.

The instructions here are wrong. The supplied CP screws are too small and would never work. Instead, they expect us to use two (2) AP screws:

One of Mike Lane’s many fantastic products is included in his Decal Set II. This is a dry transfer decal of the tiny radioactive symbol that belongs on the yellow Reactor Disc 3. I found this easiest to install by using the whole assembly so far as a platform:

As he usually does, Mike includes extras, so I cut the pair of decals in half:

Using the red lines as guides, I removed the backing and attached the tape to the reactor:

Finally, using a soft lead pencil, I rubbed the decal firmly into place. I did not rub over the red lines, they are not part of it:

I checked under the film to make sure the decal was in place, then carefully removed it. And this is what you get:

A tiny modification, but an accurate part of the reactor for sure!

Mr. Fusion

Step 1

Put the two Mr. Fusion body halves together and fix into position with three (3) AP screws.

Fun Fact: On the real car, this was crafted from a Krups Coffina model 223A coffee grinder:

Step 2

Attach the transparent Mr. Fusion Chamber (4K) Lid to the Mr. Fusion Chamber (4L) component.

It does not snap into place or anything, it just fits very loosely on top. Step 3 will secure it into place:

Step 3

Slot the assembled Mr. Fusion Chamber components into the corresponding gap in the Mr. Fusion shell. Then, click the Mr. Fusion Lid down into place.

It takes a little bit of effort to get the Mr. Fusion Chamber to snap into place, but it will. The Mr. Fusion Lid pops on easily:

Step 4

Take the first part of the Hinge (4G) and attach to the Mr. Fusion Hatch using two (2) AP screws. Make sure the large circular hole is positioned as shown:

Step 5

Fit the black Mr. Fusion Chamber (4E) to the Mr. Fusion Hatch and fix with one (1) AP screw.

On the real car, the black base of the Mr. Fusion was created using the outer shell of a Singer Librascope magnetic disc memory core:

Step 6

Attach the base of the completed Mr. Fusion shell to the Mr. Fusion Hatch with one (1) AP screw:

With my model, the Mr. Fusion did not want to sit flush on the hatch. So, I sanded down the raised hole a bit and cut off some flashing for a better fit:

Steps 7a-7b

Clip the Hinge (4I) into the red Hinge (4H) and attach with two (2) DP screws.

Again, the instructions here are wrong; use the supplied CP screws. Also, pay special attention to the alignment of the hinges here. It is pretty easy to get them screwed together crooked:

Steps 8-10

Assuring that the flat end of the Hinge assembly we just built is facing up, click the assembly into the black Mr. Fusion Chamber. The hinge should sit flush so that the hole in Hinge (4I) lines up with the screw hole in the chamber body. Fix the assembled Hinge to the black Mr. Fusion Chamber with one (1) AP screw.

There is a pin on Hinge (4-I) that should be towards the end with the Mr. Fusion Hatch. Also, the instructions reference entirely wrong part numbers 4M and 4K. Just ignore them:

Step 11-13

Take the two Springs and thread them onto the two posts on the red Hinge (4H). Fix the two Springs into place through the top of Hinge (4I) with two (2) DP screws.

This is not an easy step, so get ready for a good or bad time depending on your finger agility! The Springs were tiny and had a tendency to launch across the room. And, the instructions were wrong again; these are CP screws. Finally, as most have discovered, getting the screws started first helps a lot:

Then, I fit the Springs over the red pegs and held it into place while I fastened it down. A good pair of tweezers helped a lot here:

Step 14

Align the assembled Mr. Fusion reactor with the matching screw holes on the Bodywork panel, ensuring the panel is the correct way up. Fix into position with three (3) AP screws.

No matter how hard I tried, this did not want to sit flush. One of the casting depressions in the Bodywork panel was simply too shallow to take the pegs on the bottom of the black Mr. Fusion Chamber. I tried using a hobby knife to trim the peg down to make it fit, but ended up just cutting the whole peg off. No worries however, as the two other pegs will align it just fine:

As many builders have noticed, Eaglemoss messed up the Mr. Fusion by leaving these three ugly screws exposed. Luckily, another great product from Mike Lane is here to save the day! He released a Mr. Fusion Vinyl Wrap, so I returned to this issue again to install it. This consists of a printed sticker with the correct graphics and can be directly placed over the holes. However, this could still show dimples where the holes are. So, I took it a step further and filled the holes…

To start, I took the clear plastic pieces off (I had something in mind for them as you will see below):

Next, using Deluxe Materials Perfect Plastic Putty, I completely filled the holes. This is a low-odor, water-based plastics putty with easy clean-up and very little shrinkage. This helped the process by only needing one application:

While this putty was still wet, I used a wooden stick as a spreader to press it into the holes ensuring they were completely full:

I let the putty dry for about an hour, then came back and sanded it all smooth using 800, 1600, and 2400 grit sandpaper sticks. It does not have to look perfect as it will be covered up, it just needs to be really smooth. This can be tricky, and I did manage to nick the top and sides in a few places exposing the black plastic underneath. I corrected these nicks by removing the Mr. Fusion and giving it a quick coat of Tamiya XF-2 Flat White paint:

Now for the best part, I applied the new vinyl decal. The logo and lettering look great and the little ‘holes’ are much more accurate!

Finally, I always wondered why the clear parts of Mr. Fusion were not darker as per the original. So, I gave them a few light coats of Tamiya X-19 Smoke paint. Unfortunately, this causes them to become cloudy and lose their transparency. That sucked to find out, but all is not lost.

A long time ago, in the model building community, a neat trick was discovered regarding using an acrylic floor polish called ‘Future’ to add an deep glossy layer to plastics. Today, that same product is sold in the USA as Pledge Floor Gloss. By letting a few drops of this amazing stuff run over my parts and dry for 24 hours, they turned transparent again:

And look at the result! I had an extra Issue 04 handy, so I can compare and share my modded Mr. Fusion (left) to the stock Eaglemoss one (right). The difference is night and day and the results are extremely satisfying!

But wait, there’s more! What is a Mr. Fusion without some garbage to make it go? Mike Lane answered the question with his Mr. Fusion Fuel. This product is two tiny 1:8 scale banana peels and a Miller Lite can from the end of the first film. I hope this picture can convey how superb these are:

Mike also includes a thin plastic disc that can be mounted under the Bodywork panel:

This allows you to actually put the fuel pieces into your Mr. Fusion and not lose them. Thank you Mike, you are my hero!


This was the longest issue yet even before the mods! Other than those little springs, this was a fun issue with lots to build. The Bodywork panel is metal, but all of the other parts are plastic. And like before, this is another issue where you need to put all of the parts aside for safe keeping. They will not be used again until the very end of the build in Issue 126.

Running Total of screws used so far: 37

Next Up

 Issue 05 – Suspension: Front Suspension/Hub (Left)

5 thoughts on “ISSUE 04”

  1. I’m four issues behind you, but haven’t started my build. I’m finding very informative following your build, so I know what to expect and ideas for mods. Thanks.

  2. I have just found this website and am very impressed with your results. Very informative! I will definitely have to get those decals from Mike Lane. I went through several copies of kit #4 trying to get the screws right, thinking that they just flat out mislabeled those small screws – are they really supposed to be CP? – and had mislabeled the DPs as CP. The other issue I have with #4 is that the manual shows the larger reactor ring with three mounting studs on the underside that are missing from the actual part. How is this going to be attached later on without these mounting studs?

    1. Thanks for visiting! From what I understand, they supply the original trial magazine, but with the updated production parts. That’s why they don’t match up. The reactor disc will never be mounted to anything (it will just sit on top of a plastic light diffuser) so the posts are not needed.

  3. Let me share my experience, as I’m building this issue for the second time. If there is only one issue in the entire build where you should really take the time to pre-thread every single hole before installing the final screws…it’s this one! For God’s sake, please do it and you will thank yourself later. Just prepare every piece one by one, before you install anything together! You can work backwards – start with the last piece and prepare them one by one. Install the screw, carefully in a perfect 90 degree angle, then gently remove it. This will remove the leftover paint in the holes and it will carve a screw-shaped hole to lead your screw later in the correct direction.

    This is especially true for the tiny CP screws everywhere…you will need to apply pressure to screw them in, once their parts are installed to something else, and the more pressure you apply, the more you will bend the existing installation – and you will end up with a rotated piece, things won’t fit perfectly together later.

    There are so many pieces here which must align perfectly well, the screw must fit in a perfect, flawless 90 degree angle into the hole, otherwise your red hinge will be drooping, it won’t touch correctly Mr. Fusion and won’t hold it down. Same way, the black hinge which is holding the big white cap on top of the reactor, if you install it just slightly angled, your Mr. Fusion won’t align correctly on top of the barrel and it will look crappy.

    And those tiny springs – damn, hold your palms closed around the reactor barrel when you install those microscopic little bastards. Just one bad move and you won’t see that spring ever again – many of us learnt this the hard way. 😀 A good trick is to pre-install the CP screws which will hold the springs, you will be able to compress them when installing on the two ends. Use a PH00 screwdriver. PH000 did not have enough torque for me, which is surprising given that CP screw is smaller than the AP. The PH00 in general was very handy for both types of screws, you can work very efficiently. I used my own fingernails to squeeze the springs, very slowly and carefully – using the tweezer tool just caused me too much trouble with these super tiny things.

    Make sure you do a lot of small, but strong quarter turns with your screwdriver. You will learn it later on, but I was a total amateur during the first few issues with this car and unfortunately, issue 4 is a very delicate piece.

    As for the order of installation, I found that installing the red hinge part (4-I to 4-E) first will make your life easier. Then the white lid combined with the black hinge (4-G to 4-E) on the opposite side. And only after all of this, the very last step, to install Mr. Fusion on top of the white lid (4-F). This minimized the unwanted pressure and bending on the already installed components, so by the end they stayed very tight and perfectly aligned.

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