3D printed Ultima ST "Type-R"

[HiTec]

Does someone recognize what this is going to be?

[GoMachV]

Marui gearbox to use a flat chassis?

[HiTec]

Correct! Hunter/Galaxy rear chassis. Im drawing this using my own broken Hunter chassis. Im also fixing some flaws this chassis had, mainly the idler gear area and rear shock mounts. Idler gear will be ball bearing ready, the universal joint axles bearings will be swapped from the odd 11mm size to 10mm OD bearings, so they will be easier and cheaper to get. The lower arms pockets will have 7mm OD 3mm ID bearings and lower arms will have 3mm hinge pins instead of those binding 7mm plastic "axles". Rear shock mounts will retain the original geometry, but they will be reinforced and separate from the chassis (installed using screws).

I actually had in my mind that i would do a model the whole Hunter/Galaxy chassis, but design it to be printed with 2 pieces and screwed together as it wont fit on my printers print bed, but i could actually do a flat chassis version also.

I will also re-design the gears for this gearbox. Marui used 0.6MOD gears that cant be printed with FDM printer. At least with 0.4mm nozzle i have in my Prusa i3 MK3s. I will swap the gears to 0.8mod, that can be printed and figure out the gear ratio later. I currently only have Kyosho OT-28 diff gears in my hands, so the first version that will go to use will probably use the Ultima ST GP diff i had designed earlier as a diff case, i will just swap the gear tooth count to it and design a new idler.

The other possibility that i had in mind was to buy a complete Kyosho gear diff and design the gearbox around it, but ideally i would love to print spares instead of pouring money to the parts and wait them to arrive. (UMW604).

The first revision of the gearbox area is already printing, should be ready in 1 hour!

The chassis body posts will be ready for aluminum M3 screw posts. I have had great experiences with my 3D printed Ultima ST with that mod. The printed posts will never be durable enough. Even these OEM Marui molded posts werent durable enough. When i look at these, i have to say that all i see is lazy design. Not enough support for the posts, combined with bad quality plastic. With Ultima, i just modelled the plastic posts so i could just push fit the aluminum post inside a plastic post. Never broken those posts since that mod. Also retains the OEM look, though i would still like to have those aluminum pieces showing.

Edit: Added two pics (still work in progress!):

[HiTec]

First print came out great! I had some troubles with the first layer, as i didnt remember to raise up the nozzle temp when i changed the filament from clear to red, but i managed to save it during the print.

The quality is draft, which is okay for this kind of proto:



Edit: Quick test fit with low gearbox cover, 5mm drill bit, 10x5x4mm bearings, main gear and OEM lower suspension arm.



Edit 2: And finally with OEM shitty design + titanium 3mm axle and worn up OEM idler.



Edit 3: I almost didnt believe my eyes when i started to bolt on more parts on this proto. This must be my first thing ever where every single thing matches and lines up at the first try. Usually i mess up even one screw location or something.







I will create a new thread for this car.

[coxbros1]

Damn son! shits getn real!

[HiTec]

Damn man, awesome comment! Thanks! I created a new thread for Hunter, so that will continue here: https://www.rc10talk.com/viewtopic.php?f=33&t=45922

[HiTec]

Here´s the final chassis revision im doing for this car. This has everything that i can think of:



- Support for aluminum body posts in front and back.
- Support for RB5 rear chassis plate and suspension holders.
- Support for RB5 rear bulkhead.
- Support for original Ultima ST rear bulkhead.
- Support for 3S batteries, the max dimensions have been designed for this battery: (i use this: https://hobbyfactory.fi/p65118/team-orion-3s-55c-ranger-lipo-battery-11-1v-4300mah-t-plug-ori14326). Those are the absolute max physical dimensions for battery.
- Support for aluminum battery holder posts (bolted through the chassis).
- Slit for steering servo cable (cable management)
- Additional 2 screw points in front chassis (i honestly dont know what are those, but i saw them in RB5 chassis pictures, so added those (the screw locations ARE NOT THE SAME THAN RB5 CHASSIS AS I DONT HAVE THAT CHASSIS).

This chassis will be durable enough for even a hard driving and jumps if aluminum body posts are used. The chassis needs to be printed from Carbon Fiber PETG, or CF Nylon. I personally like to use CF/PETG as its easier to print and also doesnt flex too much. I have tested this chassis with my own car in Finnish winter. The lowest testing temp was -28C and included full speed crashes to snowy/icy things. I broke some of my other 3D printed parts and also original Kyosho parts, but the chassis holds on. So its good to go.

If you are using this chassis and slightly shorter than max length battery, you can use slicer and slice the chassis half from the straight area around the battery area and make it longer or shorter. Do the same for the battery holder, print the chassis and voila, you have a custom length chassis. If im correct, this car suffered from too long chassis, so ideally you would have to shorten it up.

I have tested it with hard gripping rear tires and indeed, even on the snow the car starts to understeer with OEM length chassis.

[HiTec]

Had some spare and prototype parts laying around so i thought to assemble a second beater.



Im 3D printing the rear shocks, as my first 3D printed silicone oil filled shock has worked great. Front shocks are from some small edit: it was Team Associated crawler and front springs are from PureTen Alpha 2. I just designed and printed adapters for those springs and also a small plate that bring the shock tower mounting points slightly lower as the shocks are 1cm too short.

This thing only needs
- RB5/RB6 rear motor transmission
- Stock dogbones.
- Receiver and motor
- Rear shocks (havent printed them yet).
- Maybe slightly more grippy front tyres.

[HiTec]

Shocks released. I have tested them now so much that its safe to say that they work:

https://www.thingiverse.com/thing:4780157

Seal/shim pack packed up to the shaft with installation collar, ready to be installed.



And installed:









Enjoy.

[Mr. ED]

Wow, my hat of to you sir!

[Dadio]

Are you pausing the print to insert the O rings then continuing ?

[HiTec]

Thanks!

Dadio: No, print them from start to finish and then install the parts like i guided in the thingiverse thing description. The star washer keeps the seal/shim pack in place as the star washer "wings" grab tightly to the flange i designed it to grap. You can feel it gripping when you pull the piston shaft with force, when the temporary installation collar is still installed to the shock shaft.

I added one picture to the previous post that shows parts just before installation.

The design is a kind of hybrid from stock Racing Sports plastic and Type-R aluminum shocks.

If seals need replacement, the star washer can be wedged off with small screwdriver. I suspect you can only swap them once, after that it could be that there isnt any fresh flange left where the star washer could grab on. But the shock body is so easy and cheap to print that it doesnt matter. I had to design these, as i couldnt find original Kyosho shocks to all 4 corners anywhere with these lengths.

I thought about designing 2 or 3 cap shock, but those would be just extra places where it could leak.

If using new pistons, 10,2mm version shock bodies are used. If old worn up pistons, then 10mm version. At least with my I3MK3S and Prusaslicer. I recommend using only X-Groove seals, normal style o-rings are untested as i only had fresh ORG03X:s laying around.

I tested my designs with stock "black" Racing Sports pistons (new and used) and also with new Type-R style white pistons.

The first prototype shock had almost 20 battery cycles behind before i pulled it off and replaced it with v2. It still performed nicely, didnt leak or bind. It was just slightly bulkier, it had bigger threads and it was printed with 0,15mm layers. V2 is just so much nicer looking and that alone was a big reason to upgrade.

Two oil were used in testing. Graupner winter quality, which was like water and then some "900 syrup", which was ofc bad choice for winter, as the car was like a piece of wood with that oil. Unfortunately i ran out of winter quality, and they only have that syrup in stock, so now i need to use that syrup before i can finally get some lighter oil. Well, more oversteer it is.

I will try to get some running footage about this car in a couple of days.

[HiTec]

Heres a short video about the shock:



I recalled the shock fluid wrongly, it was even more heavyweight, it was 950.

[HiTec]

Received my SC6/RT6 suspension arms and other parts also.

Just as planned, my chassis works perfectly with "Frankenstein setup":

- Stock RB5 bulkhead
- Stock RB5 rear chassis plate
- RB5 front "RF"or "RF2" hinge pin holder
- Stock SCS6 delrin bushings
- Stock SC6 hinge pins (i used 3mm titanium)
- Stock SC6/RT6 rear suspension arms
- Stock SC6 rear upper arms (i used stock Ultima ST Type-R upper arms)
- SP107H rear hub carriers (You can use whatever you want, theres plenty of space between the arm outer forks).
- Stock SC6 outer hinge pins
- Stock SC6 rear hinge pin holder
- Stock Ultima ST Racing Sports dog bones and outer cups.
- RB5/RB6 rear mount transmission (complete)
- My motor plate (probably can use the stock RB5/6 plate as well.)

Only things im going to modify is the rear shock tower, so it will be compatible with RB5 bulkhead to retain stock geometry and look. Rear bumber also need one small mod. But otherwise its good to go.

This setup opens up some great adjustment optiona and also gets rid of the rear suspension arm problems as these are easy and cheap to get! Cant wait to test this thing!

Couple of pics:

[HiTec]

First short clip! Sorry about the diff sound. The diff plates are dead and i also thing the diff balls are also not balls anymore.

I only had partially charged battery on this test, i will take better video when i have fully charged it. I would say its pretty nice for a 3D printed. As already said, the 3D printed shocks would def need a lighter oil, but its not available so i have to wait and use that 950 oil.

Im also out of words how the 3D printed slipper eliminator has held. Those jumps and landings with those Schumacher stagger rear tires doesnt make the job easy to it.

Click the pic to open up the video:



The starting point of this project was this car. (Kyosho Ultima ST Racing Sports GP). This pic is taken in 2006 if i remember correctly. In the video, you will see that i still have the exact same body.



Also in youtube: https://www.youtube.com/watch?v=PkzkD2Bnnkk

Obvious thing to say, i love 3D printing. I wish this technology was available when i was a kid.