Build tricks & tips: Thunder Shot & Dragon chassis

[TurnipJF 10299]

A few years ago, I restomodded a Thunder Shot, turning it from a complete wreck into the car you see below:

I enjoy running it and it makes a rather capable RBP competitor, so when the Saint Dragon became available with a pre painted body for less than the price of an XSA Grasshopper, my wife suggested adding one of those to the stable too. Here follow some tricks and tips that I learned when restomodding the Thunder Shot and implemented when building the Saint Dragon.

 

Before the build

The re-released versions of this chassis have some moulding imperfections on the E parts gear teeth which make for a very noisy drivetrain if you don't trim them off prior to assembly. They will eventually bed in by themselves, but it takes ages. A few scrapes with a sharp modelling knife is a far quicker way of getting them gone.

 

Step 3 - Attaching counter gear

My first deviation from the norm happens in Step 3, where the manual would have you put a plastic bushing in the counter gear before sliding it onto its shaft.

Normally one would replace all plastic bushings with metal bearings and my bearing kit came with a metal bearing to replace this one, but looking at how it sits in the gearbox, it doesn't actually function as a bearing at all, just as a spacer, since the shaft and counter gear rotate as a single unit. I therefore utilised the stock plastic bushing in this location as it is lighter and gives me a spare bearing for use on something else.

 

Step 4 - Rear gearbox

The manual would have you install part B8 with the wider part at the top.

However if you flip it so that the wider part is at the bottom, this gives you some rear toe-in. It has two sets of holes for the hinge pins and appears intended to be flippable in this manner, although it isn't mentioned in the manual for some reason.

 

Steps 5, 6 and 7 - Propeller joints

The chassis makes use of a metal and plastic thrust washer arrangement using parts E1 and BA13.

It looks like one can fit a 1150 metal bearing in there instead, or even a proper thrust bearing as used in the F103 diff for example, but these are ever so slightly thicker than the stock parts and cause the gears to bind when everything goes together. Unless you can find a slightly thinner bearing somewhere, the stock arrangement works better.

(Oddly, this only seems to be an issue with the re-release gear set. The vintage ones seem to work fine with either a standard bearing or thrust bearing in place of the thrust washers and are presumably molded to different tolerances?)

 

Step 13 - Attaching rear upper arms

The gearbox plastics are quite prone to cracking if the stock hinge pin screws are screwed straight in. Some people replace them with shafts and E-clips, others heat the screw. I have successfully used the heated screw method, which in my case involves putting the screw in place ready to tighten, then touching a hot soldering iron to the head until the first bit of thread only just starts to melt the plastic and sink into the hole. I then remove the soldering iron and screw in the hinge pin, being careful to stop when it is all the way in, as the hot screw can easily strip out the hole if over-tightened. Once everything cools down, the screw pin is secure and the plastic is relaxed, ready for many miles of trouble-free use. The same method can be used for attaching the front upper and lower arms. The rear lower arm mount is made of a softer, more rubbery plastic that isn't prone to cracking, so while the heated screw method doesn't do any harm here, it isn't needed.

 

Step 14 - Attaching rear axles

Those familiar with this chassis will no doubt also be familiar with the whitening of the lower suspension arms at the base of the pieces which extend towards the hinge pins. As the arms are secured on the outside but not in the middle, the two points where the inner hinge pins pass through them can be squeezed together in collisions, and are also placed under pressure during acceleration and braking. As the plastic flexes, it develops a whitish tinge. This can be avoided by placing some 3mm I.D. tubing between the two points where the hinge pins pass through, supporting the arms and stopping them from flexing when squeezed.

The same recommendation applies to the front lower arms attached in Step 22.

 

Step 19 - Attaching rear dampers

Using posts to attach dampers designed to take ball connectors is a recipe for slop, especially after the car has been running for a while as the plastic at the front and rear of the eyelet hole is worn and compressed, resulting in the whole hole reaching the diameter of its widest point, which is wider than the post. Replacing the posts with the ball connectors of your choice keeps your shock mounts less sloppy for longer. Ball nuts work well on this kit as they can be secured with screws from the back at the top, and long grub screws with the stock nuts at the bottom. The same applies in Step 27 for the front dampers.

 

Step 21 - Attaching front upper arms

In addition to using the heated screw technique for the hinge pins discussed earlier, this is the point at which the notoriously vulnerable A5 part is fitted. I am sure anyone considering this chassis is already aware of the steel braces and alloy replacement parts available to address this issue. I opted for the steel brace.

This is secured with two screws, and adds 2mm or so of thickness, bringing the screw heads 2mm further out compared to where they would be normally be. I therefore substituted the stock 12mm screws with 14mm ones so as not to lose out on any potential threads in the plastic.

 

Step 23 - Attaching stabilizer

The front body post is attached in this step, and I found the stock one to be a bit on the short side, requiring the shell to be squished down and flexed a bit to get the body pin on. Shapeways have a longer post available, which I seem to remember was designed by one of our members although I forget who.

This alleviates the issue and even gives enough room for a foam pad to be fitted, eliminating rattling and protecting the paint.

This step also involves attaching balls to the ends of the stabilizer, which in stock form are secured with little pieces of rubber tubing. In practice I found that these tend to come off quite easily, so I replaced them with ball connectors secured with grub screws, and popped some M2 nylocks on the exposed ends of the stabilizer bar.

 

Step 30 - Attaching battery holders

In addition to attaching the battery holders, this step also has one attaching the rear body posts. On the Saint Dragon, these will later have a U-shaped fibreglass piece attached to them with body clips. A more secure method of attachment is to bolt the fibreglass piece in place. This necessitates the fitment of standoffs at this point rather than the stock body posts. If you happen to have built a TC-01 and swapped the stock plastic shock extenders for blingy but otherwise pointless alloy ones, the leftover plastic ones work well here, being a couple of mm shorter than the stock posts. This means that you can fit a foam pad to the rear body post and utilise the upper of the two holes for the body pin, retaining the stock body height with less protruding post, less rattling and some protection for the paint.

While you are at it, you can skip forwards to step 44, and rotate the fibreglass piece through 180 degrees so that the arms of the U point towards the front of the car. With the piece in the stock orientation, the arms stick out below the "ears" on the back of the shell. With it rotated, they tuck in underneath them.

 

Step 34 - Attaching front gearbox

The front upper mounting points on the chassis aren't the sturdiest out there, so putting some washers on the 3x12mm screws that go through them help spread the pressure from the screwhead a little, prolonging their life. You can see them there in the photo I uploaded for Step 23.

This is also the point at which you fit the propshaft which in stock form is a thin bit of wire with a loop at each end. Shapeways have a sturdier sintered steel alternative which uses the stock propeller joints, or you can use Hotshot propeller joints and a TT-02 propshaft.

Both solutions work well and don't twist or go floppy like the stock one.

 

Step 36 - Attaching driver figure

In stock form the chassis uses a polycarbonate cover which features the shoulders and arms of the driver figure, to which one attaches the injection-moulded head. I am not a fan of the cover as it impedes ESC cooling and makes accessing the ESC-mounted switch a hassle, but I didn't want to forego a driver figure, so I elected to fit a Hornet-style one as used on the Madcap-based Saint Dragon and bolt him to the canopy instead.

 

Step 40 - Attaching wheels

The triangular wheel mounting pieces for the stock wheels can be replaced with ordinary 12mm hexes which open up a wide range of wheel and tyre options. I went for the FTX Vantage wheelset in white, as it is affordable and easy to find, the tyres last quite well and the white rims are closer in appearance to those which come with the Mini 4WD Saint Dragon, as are the staggered wheel/tyre widths rather than the stock same-width-all-round arrangement.

Something to bear in mind if using this wheelset is that the mounting faces of the rear wheels are about 1mm thicker than the fronts, so if you want the thread for the wheel nuts to protrude by the same amount front and rear, you'll want the rear hexes to be 1mm thinner than the fronts.

 

I hope that these tips are of help to others who are building this chassis, and I'd welcome any others with experience of this chassis to add their own tips and tricks to the thread.

[Andreas W 2558]

Excellent tips.

 

I can tip that if you use a Flysky FS-BS6 receiver that fits brilliantly upside down in the slot on top, rear of the battery compartment. That is super in the winter,  as the snow powder makes it's way into most other places, but not there. 

[Grumpy pants 5511]

Great tips, fantastic information 👍

[BuggyDad 6021]

Opportune, this thread, given I'm thinking about getting my lad one for Christmas. Will follow!

Would be interested to know if anyone has a list of the suspension shafts required to replace the screw pins. 

[Saito2 7724]

Excellent write up @TurnipJF! Hits most of the points I address when building up one of these chassis plus some new ones I need to try. Thanks!

[Re-Bugged 11605]

Thanks for taking the time here 👍🏻 Some great tips I can apply to my TS. 

[ucacjbs 16]

3 hours ago, BuggyDad said:

Opportune, this thread, given I'm thinking about getting my lad one for Christmas. Will follow!

Would be interested to know if anyone has a list of the suspension shafts required to replace the screw pins. 

Fairly certain the following will do it

1x TL-01 pins

2x 54695 GF-01 pins and suspension bridge

1x 54395 22mm pins

2x 53539 the shims/spacers too  

What I bought for a planned but not realized dragon build  

Pretty certain I crabbed the info from Taffer’s thundershot(?) gallery. The lengths made sense vs the manual.

(And now many of these are in my HS ii, with ludicrous numbers of spacers til I find some pins around 35mm or so)

 

 

 

[Frog Jumper 3848]

My Dragon thread:

 

[Carmine A 2601]

@TurnipJF looks like I've got work to do on my Fire Dragon when I get home! Awesome series of tips! The 3mm tubes on the lower arms is brilliant. I've already fitted an Alumininium A5 part. I just didn't want to risk it.  Like you, a PRE-PAINTED Fire Dragon wasn't high on my list.... but at the time it was cheaper than a GHII.

[isomer1 179]

Sidenote: Thanks to this post I found out that Shapeways is back! Excellent!