My Ultima GP ST "Type-R/EVO" 20th anniversary project with 3D printed "CF" parts.

[HiTec]

Hi all. I bought Prusa i3 MK3S printer couple of months ago, and i thought to start a learning project with CAD. So. I shook off the years of dust from my old Ultima GP ST which I left to the shelf because of the stripped spur gear, which was discontinued.

I started the project with modeling the spur gear:



Printed prototype:



Slipper clutch parts were also missing, so i needed to model and print them as well:





Then i saw that there was lots of play in the steering linkage, so i started to model new parts, that are actually better than stock Type-R parts (because these have ball bearings). These also have same lock to lock angle on both sides, which the stock ST doesnt have.







And printed:









Custom -R style model rear axle hub (first prototype):





Stiffer steering servo mount:





Rear lower control arm inner hubs:



I also drawed those parts with ball bearings, i dont know if it works, but im going to test it.

Front lower control arm parts:





-R style thorttle servo mount/receiver box, that goes directly to the stock ST chassis plate (second prototype):



I used this picture to draw my own model:



First proto and the stock part:



I also modeled the gearbox gears. I dont know if they will last, even if printed with CF, but yea, its nice to have everything modelled. These gears width is maximised, so they will still fit to stock gearbox housing, but the gears teeth part is still wider than stock:





Example about the width difference:



-R style gearbox housing (basically the only difference is the brake system. The brake pads are at angle, in normal ST they are in "level". This -R part is also discontinued, cant find it anywhere):

[mtbkym01]

The gears are great, it’s something I’d like to be able to do. I have a gearset for a crawler that is discontinued that I’d like to be able to copy. Good job

[HiTec]

Thanks! What crawler is it exactly?

RS-8 front bulkhead modified to accept sway bar:



Second proto printed:





-R model rear hub:



-R model battery bracket/rear bumper:





Front wheel:



Rear wheel:





Started to print some final parts with CF filament (20% carbon fiber/80% PETG):



-R model rear hub printed with CF filament:








Front bulkhead with sway bar brackets:



Front suspension plate (MUCH stiffer than original, original flexed like crazy. I cant see any movement when i press shocks with this installed). I designed this to be 1mm thicker than original. I also slightly adjusted the "weight saving" area, so the outer walls are slightly thicker than in original.:





First test print wheel. Rear wheel weighs 2 gr more than original, because i reinforced the drum and face area. I tried to save some weight on the face though. The wheel face/drum has 2mm walls. Front wheel is 2 gr lighter than original, because is did it with 1,5mm walls.



I also bought Ultima ST Type-R EVO stiff chassis plate:



Because i now have the extra chassis plate, im planning to do a "beater" and a full race versions of this car. The beater uses stock ST chassis plate and uses the extra, still usable stock Kyosho parts that i have and also fully usable "red" prototype PETG parts that i have printed.

The EVO chassis will be the thing. That race version will use all CF reinforced parts, with metal gears in gearbox. I have few versions of metal gears already coming from USA. Interesting to see if they fit, because ofc they are not originally designed to this car.

Its always a possibility to get these gears and diff housing i designed to be 3D printed with metal in a place that has laser 3D printer. I dont know the price of the job, but lets see what happens...

Edit: Latest part. RS-7, with CF:



This might need some more re-designing. I might steal the idea from Ultima RB5 to get this parts "front flap" reinforced. Some other parts around this are also going to need some minor re-design if this part is modded, but thats not a big deal.

[HiTec]

I modified the bulkhead and shock tower to accept the front lower plate that has 4mm high and 10mm wide strengthening area on front flap.



I "stole" this idea straight from Ultima RB5 front chassis plate:



Edit: Sneak peek, "making of" rear shock tower:





Edit 2: And there it is, ready to print. Its 1mm thicker than original, and the "weight saving holes" are slightly smaller. I also left the lower holes out from this design:



Edit: Ordered the whole Type-R turnbuckle set, balljoint ends, long and short balljoints and 3mm titanium rods.

Edit 3: Yep, confirmed, much stiffer than original. I can try to bend this with maximum finger force and it doesnt break, or bend:

[mtbkym01]

It’s a Venom Creeper

[HiTec]

Those look like easy to draw if i had a set of those gears on my hands. You should try Fusion 360 with FM Gears script. Super easy to draw gears with that combination.

Latest version of RS-5 rear suspension arm holder:





Much thicker than original. Works either with stock Ultima ST rear lower arm mounting type, or ST/EVO version of mounting. I added a support "flange" to the part, it sits flush with chassis plate and doesnt even interfere with arm. I dont know if it supports anything, but at least it looks cool when the part sits flush with chassis.



New version left, old on right:



Once i get the EVO-chassis, i will draw the 1mm support pin holes to the right location on this RS-5 part, and then this part is done. Should be as rigid as CF/PETG 3D printed reinforced EVO design part can be.

Experimental (as i dont expect these to last) version of reinforced rear lower arms (stock on left, printed on right) Stock weighs 16gr, CF printed weighs 17gr:

[HiTec]

Steering arms:





These are beefed up a lot. The weak point in this part (when 3D printed), is the wheel axles front area. Im sacrificing some of the strength on that area when 3D printing this arm horizontally, because by that orientation, i can get the lever part (where the ball joint is screwed) super strong.

The way this steering knuckle in Ultima ST is originally designed, forgives some of this. The king pin goes through the wheel axle, so it supports this arm a lot.

Edit: Here is a pic how the unmodified stock arm looks like.



-R Style C-hubs (reinforced, stock suspension geometry):

[HiTec]

Kyosho RS-148 plastic input shaft gear -> ARRMA AR310762 metal input shaft gear (15T)

Almost straight swap. You just need to shim the installation depth on the axle. And shorten the locking pin a little. The input shafts metal locking pin goes too deep on the ARRMA gear, so thats why shimming it is needed.

Pictures. ARRMA gear sitting too deep:



It should be like this:



ARRMA metal input shaft gear vs Kyosho original plastic:



Gears width is absolutely identical when compared to the original, so no shimming needed to get it sit tight between the bearings.

I also modelled the -R/EVO style rear body holder:

Pic taken from some website:



My model:



And printed:

[HiTec]

Got my Inferno MP9 tank today, so i redesigned the receiver box/ throttle servo plate a little, so i dont need to drill new holes to the chassis:



And printed (CF):













The tank sits as low and as center as possible. The tank is 10mm more centered than the stock ST tank, and max fuel level is 7mm lower than with stock tank.


Diff gear/housing and idler gear printed with CF, with ARRMA Steel input gear:

[Dadio]

Looks like your really putting the printer to good use ! I love mine , they just open a whole new world of possibility .
How is the CF PETG to use and how strong is it ? I've never used it , I've used a lot of CF Nylon and its a superb material and very easy to print with compared to regular Nylon , I was just wondering if the CF PETG was similarly not just stronger but easier to print with , I basically gave up on PETG as I never thought it was strong enough and its a pain to print with .

[HiTec]

Thanks for the reply! This tech makes me wish i had 3D printer 20 years ago.

CF Nylon "should" be stronger than CF PETG. Expecially if printing gears (because its harder). I would have bought CF Nylon filament for gears, but it was out of stock, so the PETG version was the closest match.

Im definitely ordering nylon for my tests once its back on stock.

CF PETG is easy to use, at least with textured/powder lcoated Prusa spring steel print plate. Adheres to the print plate like crazy! There is some molten filament build up appearing around the nozzle, mainly with the support structures and first layer, but i've only had one failed print because of that (the molten plastic blob fell to the print, nozzle got stuck, and layer shift occured.) I clean the nozzle surrounding with q-tip just before it starts printing.

I cant say anything about how the parts will hold up on the real world testing. Im expecting that the shock towers, front/rear arm inner hubs, servo mounts etc should hold up nicely, but the rear arms, front c-hubs and gears can have problems with durability.

I will post test results once i buy new engine to this car. This one should still eun, but it has so many hours behind it, so it would need a full rebuild with now impossible to get/pricey parts.

But yea, you can tell the big difference when trying to bend normal PETG and CF PETG part with your hands.

I print with 270c nozzle temp, 85c bed. Anything lower on the nozzle temp will increase the stringing and that will increase the molten plastic build up on the nozzle.

[Dadio]

Thanks for the reply on the CF PETG , I'll be very interested in how it stands up to sharp impacts as the regular PETG is kind of split personality , it flexes in low impact but shatters on high impact , I was just wondering if the CF holds it together better in high impact situations . The YouTube channel CNC Kitchen does a lot of very interesting strength comparisons on various filaments and post process enhancements , well worth watching .

[HiTec]

Just ordered Fiberforce NYLFORCE Carbon Fiber filament roll from 3DJake, should be here on next Wednesday. Im now thinking about the motor that would be suitable for this car. I´ve been out of this game for so long, that i dont have any idea what would be the "right engine" for this. The original is GX-15, with stock small pipe, EVO version seems to have GT15 or Novarossi engines. Any recommendations?

I would love to have more acceleration and top speed than stock GX-15, but also as linear torque curve as possible to have a good drivability. I also like the pull start, i actually never had a start box, but if there is no pull start in otherwise good engine, its not a deal breaker. Is there anything worth of recommendation in this page?

https://hobbyfactory.fi/Polttomoottorit?_tr=10311

Thanks in advance and thanks for looking!

Edit:

Just opened the GX-15. Rod lower bearing is "gone". Piston and liner worn out. Crank front and rear bearing seem to be ok, but not sure about the cranks rod end "shaft". Im giving a no-go for this engine. I also opened up my Airstreak 500 GP GS-15 engine, but everything seems to be different, so i cant use that for parts.

[coxbros1]

U can still find these, new or good used if u look hard. .15 version is blue. The .12 is big power, i have one in a RC10GT. They have both pull or bump versions. U can get a decent used piece and have the sleeve pinched at RayAracing pretty cheap

20200216_173759.jpg (66.03 KiB) Viewed 2700 times

20200216_173759.jpg (66.03 KiB) Viewed 2700 times

[HiTec]

Thanks for the reply, but i live in Finland, so i have to have a engine that is easy to maintenance (easy to get parts). Thats why older engines are pretty much no-go for me.

New EVO chassis (Japanese Domestic market edition) arrived today and holy f its beatifull (click pictures to get a full size):







As for the screws, im using Wurth ASSY head 3mm TP screws. They are expensive, but the head is better than Torx or hex.

Also "big thanks" to Kyosho. Thanks for offsetting the gearbox front mounting holes 0,5mm between ST and Type-R/EVO.



Now i need to basically design a completely new gearbox covers. And because of that, im now looking to design the whole gearbox again with RB6/RT6 ball diff.

There is also small variations in chassis size (look at the rear bumper area). I need to resize the bumpers chassis recess, so it sits flush with it. I can still use this bumper in ST chassis, because it fits nicely to that.