Marui Hunter "enhanced" re-created with 3D printing

[HiTec]

Could someone more experienced with the Hunter/Galaxy list all the known most common weak points in this chassis?

I already know the rear suspension mounts, the front hinge pin areas and the idler shaft slots, but is there more?

Because when i look at this original chassis that i have, i have pretty much fixed all thats wrong with this particular chassis i own, but when looking at the possible weak areas, this looks wrong:



Im not an engineer of any kind, but that area looks like high stress area when there is any kind of front chassis flex or impact. When Im twisting the original chassis and my 3D printed one with my hands theres a thought in my head that i would like to add some beef to that area. That would also be easy thing to fix "stealthy", so it doesnt look like it has been reinforced.

Extra pic: Test fit with original body.



Edit: Because its easy to do, i will custom holders for front sway bar to this thing. Its easy to do as it can be added to the same points that the front bumper attaches. The front sway works just like in Galaxy, but the upper control arms suspension attachment points will have additional 3D printed parts where the front sway can be hooked. I will not design the front upper arms to have that function, as i would love to keep possibility to use OEM arms. So these will surely be additional parts.

[Dadio]

To a degree you just have to go with your gut on reinforcing , in the highlighted area maybe a vertical fillet outside and inside might help discretely , stopping at the bottom above the suspension mounting on the outside .

[HiTec]

Yea, thats exactly what im doing. We are on the same wavelength Dadio!

Because if i calculated correctly, with 0,30mm layer height, im only going to have 5 or 6 layers on that area. I read from somewhere else that people have been breaking stock chassis at this area, so this can be a point where to reinforce things. When printed, this area has 4mm length two layer contact area where things join together, so this is definitely an area where to focus on the final release.

Dadio has been so active in this thread, that i could send him a sample "release candidate" chassis against the material and shipping costs if he wants one (once i have tested it myself ofc). Material costs are calculated by prusa slicer and shipping is whatever the final shipping location is.

[Dadio]

Its surprising how your mind starts designing in layer counts , perimeter counts and overhang angles

[HiTec]

Yea, its a whole new world of designing when the design needs to be 3D printed as durable part

[HiTec]

Everything lines up, except the idler axle hole thats in the motor mount metal plate (this was expected).

I added set screws under the idler axle slots, just in case if my gear lash isnt correct, so i can adjust it and measure the amount of set screw thats visible. Seems that its not needed as the shaft sits nicely in its groove and the final gear and idler have correct lash.

So test pics:

[Dadio]

That's pretty good going if you only need adjust one thing on such a complicated part ! What's it made of ?

[HiTec]

The motor mount plate is basically just aluminum plate bended 90 degrees. Its easy to fab new (y).

I just wish the Kyosho diff would already be here. Im anxious to start designing Hunter/Galaxy compatible 3D printed diff. Now i only have diff eliminator final gear on this.

Edit: just did test assembly of rear suspension. Everything checks out!

[HiTec]

Okay, now once the gear lash was tested and confirmed, i will fix the idler slot flaw that the original chassis had.

This might be overkill but the idler will have 4 ball bearings. 2 in the gear itself and 2 on the shaft ends. This just might be the smoothest idler ever.

Idler shaft end bearings are first pressed to chassis, the idler is then mocked up so it lines up with the shaft line.

After that, the shaft is pushed through the chassis. Once its on the correct location, the shaft end stops (set screws) are installed. This doesnt stop the shaft from turning ofc, cause then the extra bearings would be useless, but the screws will stop the possibly turning shaft from eating its way through the plastic.



I thought about solving this problem with other way also, but i think that would have needed axle diameter upgrade from 3mm to 5mm and it then brings other problems that would need to be solved. Lets first test this and upgrade if needed.

[silvertriple]

Hello!
I just registered in this forum. I saw this thread a few months back while I got back into R/C after 30 years plus without thinking about it. For the small story, I had a Marui Hunter, it died due to the oilless bearings around the differential: those actually ate both chassis and under gearbox cover. I'm admirative of your work, as this is the type of work that may have saved my Hunter...

I found a chassis in proper state recently with the intention to restore it, and while searching parts I also got a broken chassis (shock towers on both side). I was thinking about 3D printing a bridge aon top of the rear gearbox cover (maybe including the cover) including the towers, and fixed underside the chassis in a similar way to what you seem to intend to do, as I do think that to do a proper partition of the forces going up in jump reception on the shock tower, you may need slightly more than two screws fixed (specially with an original ABS chassis of more than 30 years)...

I also read the full thread, and was thinking of the front side potential weakness. Looking at this, I was thinking that maybe a bridge going between the front (where the body is mounted) and the back of the steering servo would probably highly reinforce the chassis. As per my understanding, the place in between the two shocks is tight but there is enough space to have something going in between without disturbing the suspension movements...

That's my two cents in your great work. I definitely find it interesting and will continue following it.

Thanks!

[Mortensen44]

Hello HiTec

I just registered in the forum because of your "Hunter" tread.
My first RC was the Marui Hunter. My father gave it to me as a birthday present when I was 12.
He helped me put it together and I had a lot of good times with it... Many good memory's.
Now I have 2 boys, they started with very small RC's, indoor only..
Then I found the old Hunter. Light rebuild with new electronic, new wheels, bushings ect.. And they loved it.
I then bought two Latrax Teton's. In training-mode it was a good start for the boys into the RC world.
I made a battery box to mount underneath the Hunter, to use the same batteries as the Tetons.
For easy removal, switch and recharge outside the car... 3D printed. (I can't add pictures.. :-/ )

3 years ago the chassis broke. Have been trying ABS glue ect.. without luck..
I have been thinking of making the chassis drawing and 3D print it, but not found the time to start up.

I was in the garage and saw the Hunter in a box, dissembled because of the old ABS chassis just broke because of age..
I googled around, found your tread, AND WE GOT HOPE!
The boys is also very excited.
Maybe we can get the Marui Hunter up running again... eventually on the shelf looking nice.

I'm really interested in your project..
Maybe we can PM or mail... To see if we can help each other or make some kind of an arrangement..

Best regards

Brian Mortensen - Denmark.

[silvertriple]

I'm really interested in your project..
Maybe we can PM or mail... To see if we can help each other or make some kind of an arrangement..

Best regards

Brian Mortensen - Denmark.

hi Brian, welcome on rc10talk...
I'm also a fan of the Hunter, my first was a Hunter as well...


I posted here with the very same question. it was about two years ago. Early this year, I started to model a buggy from A to Z in Fusion 360. I started to play with Fusion 360 (free home/hobby license) in January. If you have already made 3D parts, it is worth the investment to model a buggy as it opens a full field of new possibilities for vintage cars...
Not sure HiTec is till posting here, as I believe his studies and familly are a bit time consuming, but I believe he would pushes you to open Fusion 360 and start to model the chassis as it is exactly what he proposed me to do

So in short, I would suggest you had a look a few of my own threads on Nichimo cars (Spirit FF, Midships 43WDS) or Hirobo (Bearcat, Zerda and 44B) to find inspiration and hints to start your own venture in this

(And by the way, I have also the intention to work on the Hunter myself, but for some reasons it is way low in my own todo bucket list...)