Super Short wheelbase M-02 chassis
Here, the goal is to reduce the M-02 chassis wheelbase. The M-02 chassis is the shortest existing variant in Tamiya current range of products, but the 210mm wheelbase is still too long to perfectly fit the Toyota Celica LB Turbo Gr.5 bodyshell since its original chassis wheelbase is 206mm. We have to reduce it by 4mm and I only found two ways to do it:
- the hard way: moving the front and rear drivetrains 2mm inwards the chassis
- the butcher way: cutting the chassis
The first way is pretty difficult to operate because of the suspension system. But here's how to proceed (thanks to DEE aka On the road again from the M-Chassis Forum):
The rear left arm (yes, my chassis still needs to be cleaned)
Spacers for the suspension system
On the first photo, you need to remove 2mm from the outer left side of the arm (A), 1mm from the inner right side (B) and 1mm from the outer right side of the arm fixation on the chassis (C). The 2mm to cut in (A) are only meant to keep the rear left arm free from the gearbox housing.
The second image comes from the user manual. In (1), place a 2mm thick spacer in order to move the spring outwards, and add another 2mm thick spacer along the arm (2) on the MA20 screw axis. This second spacer is meant to maintain the lower spring axle along the arm.
These operations (except step A) have to be done on the 3 other arms to reduce the overall chassis wheelbase by 4mm. After some thinking about this mod, I decided not to go for it since I considered the arms would become too fragile to deal with running stress.
So I chose option 2: cutting the chassis. I know this is not the most elegant way, and yes, you could achieve a much better looking result. Unfortunately, I had to deal with with the limited tools I have here and couldn't get better.
Cutting and reassembling the chassis
The process is pretty easy to perform: unbuilt the front and rear gearboxes to release the central chassis frame. In order to cut more accurately, I recommend to screw the two parts of the chassis frame together.
Then, you need to chose exactly where to cut: I decided to cut between the steering servo mounts since I noticed an exact 4mm free space that would allow me to still use the chassis holes to mount the steering servo. After drawing the two cutting lines separated by a 4mm distance, the saw got some action.
The next steps are to fix the chassis main frame parts we got after cutting. You can do this several ways but here's how I did: I chose to recycle FRP plates that originally hold mechanical speed controller resistors. You could probably think of better parts, but these were available so I used them . I used two FRP plates (previously cut) on the left side of the chassis and one more on the right side lower part of the frame. Drill holes in the frame to screw the plates and the chassis parts together.
On the right side of the chassis frame, you can't fix a plate in the upper part because of the steering servo: no problem since the servo mounts are now perfectly aligned with the original mounting holes on the chassis. So it's the steering servo itself that will be used to hold the upper chassis frame. If the mounting holes were not perfectly adjusted, one of the chassis mounting holes just needs to be re-drilled to achieve the same result.
Either the steering rod needs length needs to be adjusted or the servo neutral position needs to be setup up again since the steering servo has moved 4mm towards the front of the chassis compared to its original position on the full length chassis frame.
Now you need to tie cables with care since it is better to hide as many cables as possible for the final model to look nice. You also have to consider the pilot: it is glued on the bodyshell door but comes right above the chassis. The installed battery stick pack will definitely remain into this chassis since it needs to be placed with precision not to make the body move on either side. Last, the Rilsan collars have been painted flat black to better hide them.
The chassis is now finished with an exact 206mm wheelbase. After performing a test run, everything works as it should, from the steering to the overall shortened chassis strength. One more thing, and a pretty much important one: body mounts. As I said before, I don't want to drill the body. The original Celica chassis body fix system can't be used on the M-chassis, and the M-02 body mounts can't either. As the solution I chose can only be fitted once the body is painted, I will talking about the body mounts later on.