Marui Hunter - My first buggy... Found one to restore :-) - and a Galaxy RS too :)

[silvertriple]

Somehow, CAD phase 2 of the project is almost finished, and parts are ready for the final test... That said, it's a long time i'm eyeing a Hunter on ebay, and I pulled the trigger on Saturday... It arrived today

This is a tiny guy 1/32. and it was never thought to be remote controlled...


Time for CAD extended time! Let's try to do something out of this . I just order some tiny servos (super micro size), esc and rx. I'll look forward to find a battery as well very soon... And yes, my real target is to try to make a RC Hunter 1/32, and ideally fully printable (SLA resin or FDM). Not sure I'll keep the suspensions, I need to think about this, and there might be multiple iteration of this

[silvertriple]

Today, a few elements arrived.
I had already a mini servo sitting in my stuff (an order mistake at some point, but the data says it is powerfull enough for a car, I just way the good occasion to use it - spoiler : it won't be for this project).


It is small, but not small enough for 1/32. it would work good to make a 1/20 car... I have a smaller size servo on order, not sure when it will arrive, but i'm looking forward for it...


ESC and RX should not be much issue, on the other side...


Saying this, in the event the micro sized servo doen't work, I can probably target a 1/20, 1/24 or 1/28 Hunter (in anycases, I'm able to print a body shell mould (and possibly a bodyshell as well - even in colors eventually), and that should not be much a problem, and would probably easier for the battery as well...

[silvertriple]

Before moving on the target, we need to understand first if it is possible to print an universal joint in place and what tolerances are required for this. I first designed a universal joint around 1/2 of the original Hunter universal joint...


Next activity is to try to print it and play around with the tolerance to see if feasible...


And my 2 first tests were unsuccessful... It PLA, it doesn't help, and the print orientation neither... But we need to understand how interlocking can work before doing any optimsations...


I guess I will have many 10 mins print today for this...

[silvertriple]

3 semi-successfull prints. It always split at the same place, and suprisingly not parallel to the printing plan, but perpendicularly to it. The reason is because of tolerances in this situation. The one side I was expecting to break easily works perfectly as soon as you have more than .15 tolerances...

Basically, if we rotate the printing plan of 45° and make sure that the starting point of the cross member is supported that should work fine. I reviewed the design to add material which I intend to cut post printing.


And the test print is 100% success!


This means : Rear suspension is possible. I'm now thinking about scale : the optimal option seems to be 1/20 (scale 1/2 compared to the original Hunter), as screws and nuts are probably the easier to source in those dimensions, and it has the advantage of allowing for more material than lower scale.

[silvertriple]

The micro sized servo is arrived... It's really really really small


I will need to model this guy first and then think about the work to come... It may be very well suitable for a 1/32 size Hunter (without suspensions in the case I go for 1/32)...

[silvertriple]

To start working, we need to have the dimension right... So I put the two servos in CAD (it's a five minutes job, ad it will allow to work this out easily)...


Digging in the smaller size, I need to understand a bit better about gears printing in very small module.
I have the Marui gear set working in 0.8 (almost 32dp). Printing this scaled at 50% would probably give some indications of feasibility at 64dp (I may even use the Marui gearset scalled at 50% to make a 1/20 Hunter if it is workable). I put the gearset in Bambustudio, scaled it at 50% and printed it right in 0.08mm layer thickness, with tree supports and 100% infill.


Here is the result (with a Super Wheelie idle gear and not a Hunter one)


I used filament trimmed at the right length for the small bevel gear axis...


And it seems it is viable . I check and it works... I may need to review some posts of @Dadio about printing gears at it might be even usefull here...

[Dadio]

Oh Mark ! 1/2 scale 0.8 mod gears firstly "good luck" , secondly id highly recommend using a smaller nozzle than 0.4 mm , a 0.4 mm nozzle is just about ok at 0.8 mod but even then the trough between gears can lose depth causing tight mesh , I've often cut the trough deeper to compensate for FDM printing , its all witchcraft at the scale your attempting and may be better in resin ?
got to admit i love this whole idea though .

[silvertriple]

Oh Mark ! 1/2 scale 0.8 mod gears firstly "good luck" , secondly id highly recommend using a smaller nozzle than 0.4 mm , a 0.4 mm nozzle is just about ok at 0.8 mod but even then the trough between gears can lose depth causing tight mesh , I've often cut the trough deeper to compensate for FDM printing , its all witchcraft at the scale your attempting and may be better in resin ?
got to admit i love this whole idea though .

When discussing with him, Ryo raised exactly the same point. I'm clearly having a 0.2mm nozzle in mind. There is few reasons to try with 0.4mm still:
1 - For fun
2 - Many people only have a 0.4mm nozzle and won't even consider changing for a 0.2mm for a single print. Taking into assumption that people take the file as is, slice it and print, I needed to make sure I have the right understanding of the limitations. I clearly works for the bevel gears, but i'm less confident on the straight gears which are probably not deepen enough...
3 - I was lazy! Yes, I know, it's a shame, but it is really about that as well

Had already a lot of thoughts about this (my nights are populated with thoughts about scaling down the Hunter and trying to do it the easiest possible way, taking into consideration I do not have a lathe (may be something I should consider at some point), and the fact that sourcing hardware for this is also to consider... This test is about a quick and dirty way to do it...
On the other side, I also thought about resin, and why not... That said, I know already that regarding resin printing, there is one thing no one talks about in the printer testing it is about dimensional validation. I saw from my own experience that there is a big issue here and it is very difficult to assess about the proper shrinkage as resin prints are more prone to that than FDM PLA prints, and what I can read in some 3D printing related forums only tend to confirm this, and worse : it depends on multiple aspects including printer, printing condition (temperature in particular), resin (it was not complex enough already), and as well geometry as the amount of resin polymerized is also going to impact that. Ultimately, in short, you would think doing small resin might be the solution, but it is another set of complexity alone

By the way, I'm not surprised at all you love the idea... But you have ways to do that I don't have, and I would really love to see you scaling down some buggy as well

[Dadio]

Another solution to the gears is to just cheat monstrously and find a 1/18th scale car and buy the gears for it and adapt the mini Hunter as needed , that way you can publish the required parts with the STL files , there are a ton of cheap 1/18th cars on the market and I'm sure a little research should turn something up .

[silvertriple]

Another solution to the gears is to just cheat monstrously and find a 1/18th scale car and buy the gears for it and adapt the mini Hunter as needed , that way you can publish the required parts with the STL files , there are a ton of cheap 1/18th cars on the market and I'm sure a little research should turn something up .

That is absolute cheating!!! But I must recognize I thought about this

[Dadio]

By the way, I'm not surprised at all you love the idea... But you have ways to do that I don't have, and I would really love to see you scaling down some buggy as well

I've had this in mind but with more cheating , I've got a WLToys A959 that I never really use , its bonkers fast for a 1/18 car as its fitted with a full size 540 the transmission is very similar to the SG Coyote , I've already modelled the Coyote so scaling should be easy and just adapt it to take the A959 transmission , I'd change the motor for a smaller one otherwise the body would not fit .

[silvertriple]

I may have to look at that at the end anyway...
Problem may be also gearing ratios: it would not make any sense to have a smaller Hunter going faster than its big brother

[silvertriple]

My friend Johann updated his vacforming thread on Tamiyaclub with some test of the Hunter prototype bodyshell with a video


Here is his post on his thread on Tamiyaclub for reference : https://www.tamiyaclub.com/forum/index.php?/topic/78450-home-made-vac-former-forming-rc-bodies/&do=findComment&comment=1000349

It seems we are in good path to make the Hunter prototype happening...

[silvertriple]

I printed a roll cage for testing purpose...


The result is better than what I expected (again, no specific support material, just printed it in PLA). I may need to print the remaining parts as well, so I have the full set of parts to show...

And I ordered the print online for the project car.
- Hunter proto chassis in black, without switch holder - MJF PA12 black
- gear covers in both 380 and 540 versions - MJF PA12 Black
- roll cage and radio lid - MJF PA12 black
- arms and bumpers, and under gear cover - SLS PA12 White (idea is to get those dyed in light color)
- gear sets (MJF PA12 Black for the diff, Stainless Steel SLM for the idle gears)
- and a Mitsubishi Jeep bodyshell in resin as I need to understand if it is feasible or not in resin (it's basically too big for my printer)
Arrivals are expected to be by 2 weeks from now...

[Dadio]

To late now if you've made the order but I noticed you can get SLS printed PP now , probably ideal for bumpers, cages and suspension arms .