Special Project Codename EF209 - RC 1/12 pancar

[silvertriple]

Hello,

I did a few buggies in CAD, I did reinvent some partially... Next year the first event of the year I intend to attend is going to span over 4 days early May (8th-11th), and the thematic of the event is "Creation and System D". I'm not sure how it would translate in English, but basically, it consist in messing something and the mess works
Therefore, I have to do something for the track side of the even so I have a very special car. I also decided I would focus the track side on 1/12 this year as I have much much much more fun running a 1/12 pan car than an 1/10 touring car...

Anyway, I want to do a special project. It will be a 1/12 pancar very simple. Something that I could do relying on 3D print, a shaft widely available for the rear train, a few cut pannels (either Carbon Fiber, FRP, or other) that can be combined together with the printed parts to make an 1/12 chassis. A quick search shows that the rear shaft of the Fantom is widely available (and you may even have one if you replaced the metal shaft by a carbon shaft).
The bodyshell will topic will be treated only when we have a chassis plan.

This will be my starting point. Kyosho, part EF209

And I obviously converted in CAD so we can start thinking...


And yes, I have added another project to my already huge project list...

[silvertriple]

The Hirobo project gets closer to print order.
I've decided to draw some parts for this project...

The support of the rear left wheel, and the nut...


I needed to check that my thread is working fine, so I did a test print (have some ideas to play with regarding the wheel nuts, so I had to play with this and get a working nut...



The thread on the shaft works with the adhoc metal machined thread, so it's perfect (no offset, but slicer setting may impact).
The nut was printed with 0, -0.1 and -0.2mm offset to test. (again, slicer setting may impact), but at least that gives a good indication of the tolerance needed for it to work...
0 doesn't work as expected. -0.1 does engage but not possibility to get more than a turn. -0.2 does engage and the thread work. I will have to check if it is the same for power base process, but I would expect it is similar from what i've read somewhere...

That's all for today!

[silvertriple]

I decided to figure out the overall position taken by the motor pod on my shaft


The plan is quite simple actually :
Bring in a differential design I know being tested and validated on one of my cars (spoiler : many ), one I have already the design in Fusion360 : I'll use the one form my Marui 2WD gearset as a basis.


I will have to modify the main gear to be more suitable for the targeted use (let's target the same ratio as the Fantom, that makes less thing to think about )
For the diff itself, the center of the diff gear will be used as is, with the way I use it on Marui cars and same for the small small bevel gears and their shafts.
The big bevel gears will be amended in order to work out with the new shaft : left side will be attached firmly to the shaft, while right side will have to be redefined to position and drive the right wheel attachment...
And all of that should allow to have a proper diff for my chassis...

Looks simple enough in my head, that should work

[silvertriple]

Tonight, the program is to deal with the differential and as well with the right wheel carrier...

I first made the wheel carrier, which is an hex with a thread at the end and two ball bearings : one going at the end of the shaft and the other one going on the shaft. Then I brought in the diff components from my Marui gear set, and defined the way to set the big bevel gears on the hex, the installed the right one, then the diff center, and defined then the hex to push on the other side to fix on the shaft to have the left wheel driven.


Once I had that done, I modified the spur gear to be 71T 48dp because that what it is on the Fantom (I also modified the diff so there is better protection of the gears...



To get the right carrier printable (it has a modeled thread), I had to modify the thread and increase the diameter to make it M10.


I modified the internal thread of the nut to be in correspondance, and I may also change the nut size...

Next step will be to define the motor pod...

[silvertriple]

Before anything else, I decided to print a differential to check everything was fine in the design.


The diff works, and it is no surprise...


I did an adjustment on the wheel carrier (I could have done it somewhere else, but this was what I believed the easiest... Once the adjustment is done, the diff is set in place, the space for the motor pod is as expected and the nut allows to set the diff more or less tighten, just like it is on the Fantom.


This being done and validated, motor pod will be the next piece...

[silvertriple]

Motor pod is mostly easy... I did target pinion range between 14T and 27T (48dp), and made slots accordingly so we can position the motor for this. The reference point is the single hole, and I may adjust the position later on as everything is depending upon the position of this hole and the rear axle, accordingly to the targeted possible interdistances.Everything else is pretty simple. I planed for 2 holes to fix the pod on the chassis plate on each side, and one hole on the top for the upper deck.



Here, this may not be finalised parts : I keep the right to adjust a few things based on what will come next. The chassis plate will require an opening so the motor can be set for the smaller pinion... I will have to focus on the front train next.

[silvertriple]

I started the front to create a derived part from the rear right wheel carrier... Then I set the upright from there. I could have done something different with bearings inserted in the wheels, but this way, I can just do a simple design working for both front and right and giving the possibility to use printed nuts (I really want to play with this).



Then I started to work on the master part of the front train... I have the idea to let people play with the caster angle, and if we want to do this without any impact on the wheelbase, that requires to set the caster setting axis lined up with the wheels center...


Then I prepared basic clamps...


And now that I look at it differently, I'm thinking to change the way I thought the pivot between uprights and the C part : having the ball bearing in the uprights is probably much better, so I'll amend the holes and design accordingly...

[silvertriple]

I modified the upright : bearings are now inserted in the uprights and the screws are in the main arm.


The front train is now complete...


Next activity is related to chassis plates... I will target a wheel base around 200mm in this first version. I may also add provisions for longer and shorter chassis plates to give room for longer and shorter wheelbases...


I'll need to position the steering servo, esc and battery, for which I'll include more holes, and as well define the bumper fixation area, body mounts and other small elements. I'm also questioning the need of an upper deck or not : i'm actually open to any ideas

[GoMachV]

While I love selling g10 and carbon parts, I think a project like that deserves something printed Not really a tub chassis, but something with raised sides possibly. The Club Race Hero is a really cool design that you could borrow ideas from as well. The simple suspension system works great, the cars are winning events. Anyway just my opinion.

[silvertriple]

While I love selling g10 and carbon parts, I think a project like that deserves something printed Not really a tub chassis, but something with raised sides possibly. The Club Race Hero is a really cool design that you could borrow ideas from as well. The simple suspension system works great, the cars are winning events. Anyway just my opinion.

Well, the overall idea of this project went from a shaft sitting on my desk and an event targeted next year for which the thematics is Vintage RC and creation. Once you have the diff (which could be easily replaced by a Kyosho ball diff, by the way), the pod and front train, everything is possible. At this stage my primary thinking is really in vintage spirit, and my first thought was G10 parametric file for the chassis cut... And while I'm oviously in situation of printing something, it would lack the "simple" spirit I had in mind at the start...
That said, I take note of the idea, as I may want to evolve this further later on...

[silvertriple]

A quick test print to ensure it is printable, and the clamp works... (and yes, I added some cryptic message on some parts )



I will just modify the master part of the front train in order to make it easier to position within the clamps wihout the risk of it being slightly right or left...

The clamp works perfectly. At the exception of the uprights, everything was printed without supports. Upright were printed with a top spacing over supports of 0.3 mm, which allows an easy removal. I'll think about modifiying those parts to make it better, and eventually without the need for supports...

[silvertriple]

As the Hirobo parts are ready to get ordered, I'm contemplating the idea to add diff, wheel carriers and nuts in my order to save on the shipment costs: those are the parts where I believe it makes sense to work with powder base process for this project. Others will be printed using filament.

As usual, and just to make it more convenient, I grouped the key parts in clusters. The wheel nuts are going to be printed with a 0.05mm offset. The idea is really to confirm the right offset to use, so I will add a set of nuts in 0.1mm offset as well. That's the first time I'm trying to print threads in MJF, so it promise to be interesting. I saw some experiments of threads printed in MJF and I believe it should work as per this experimentation...


Let's see...

[silvertriple]

I ordered those parts while ordering for the Zerda, so they arrived as well...


I did a mistake when doing the order : I completely forgot to use the right nuts version. Nuts are wrong.
But the rest is fine.


As expected (and that what I wanted to check), I'll need to add something to make it right with MJF (the FDM printed parts add some imperfections here and there, which at the end makes a bit of difference when they are added in chain, like in this case...

[silvertriple]

I spend a bit of the day today on this project, with the overall idea I want to be able to make it quite versatile in terms of battery configurations, and I also planned for mini and standard servo (mini servo is better, though), with a bit of flexibility as not all servos are exactly the same size.


I still need to deal with the Bumper and bodyposts but the overal idea is here...

[silvertriple]

I'm questionning myself about keep the chassis the way it is now. I intend to use the same holes than for the Bumper as mounting points for the front bodypost (I may even think about include them in the Bumper design, using some magnets to fix the bodyshell).And for the rear, the original idea was basically to use the front top of the motor pod (where I have holes already set in order to deal with the bodyposts fixations)... And since bumper and bodypost will be bodyshell dependant, it looks like chassis design could be frozen...

I also made sure there is enough material around each holes so they can be countersunk as it will be definitely nicer to have them this way...


Next will be to get two (maybe three) chassis cut in G10 2.5mm thickness. I've check everything twice, it should be good. Hope I don't forget anything important...