Kyosho Ultima Pro XL / II Rear Bulkhead

thingiverse

Rear bulkhead for a variety of vintage Ultima-series buggies (Ultima, Ultima II, Ultima Pro XL). With the introduction of the Kyosho Ultima Pro XL, Kyosho added an additional rear hinge pin mount/boss to the Ultima bulkhead. This additional pivot allowed for the use of longer rear arms. This modification likely required the mold to be modified, so most Ultimas (i.e. the II-Series) offered after 1989 included this additional hinge mount, even if equipped with the shorter "original" Ultima arms. This bulkhead has been modified slightly to combine aspects of the re-release bulkhead while adding the additional hinge pivots. The pivots, by design, add about 4 degrees of anti-squat to the buggy and approximately 1 degree of toe-in (per the original design). I have added reinforcement ribs similar to the re-release version. I have also stepped the inner front section to allow for a battery pack to be mounted inline up against the bulkhead. In all likelihood, most people will not be mounting a battery pack that far rearward, but it is now possible with this design. Typical adhesive backed foam in front would support the front edge of the battery pack. The bulkhead will likely be a little heavier than the original (~1.5-2 grams at 100% infill). Tap the shock mounting holes with a M3 tap. The upper transmission mount has been set up as a through hole, so it should not need to be tapped. Tap the chassis mounting holes with a M4 tap. You will likely need to use a 3 mm drill bit to clean out the hinge pivots. Take care while doing this (I recommend first clearing with drilling in reverse or threading lightly by hand). You can bore it in normal drilling direction however the hinge pivots are very close to the chassis mounting screws. NOTE: I may try to design an alternate version which lower the pivots to reduce antisquat in the future. The space is limited and may also require a different rear hinge block as well.