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

[silvertriple]

Today, after my work day, I started to focus on the front.

I first defined the structure that holds upper arms and springs for the front train. I'ts definitely easier to measure than the chassis inside the bath tub, so I model it independantly, in order to check / correct the chassis...


Once the part is done, it is time to push it ia a Hunter V1 assembly (I'll start by this one). and I used it to correct the chassis.


Here is the result after corection.


Next was the upper arms. I first did a profile, extruded it, followed by a vertical extrusion, and I used a body made with surface mode to add the reinforcement. Each time I do something it looks easier than previous times...


Next was the bottom arms.
I made two set of bottom arms as V2 includes some addition in order to allow shocks addition.
V1.

V2


And here is my V1 chassis with the front arms in place.

[silvertriple]

This morning, I started with the front "shocks". They mimic an hydraulic damper, but they are just springs...


Next I included them in the front structure. And if you follow the manual, that's exactly what it would look like before you put the structure in the chassis...


Next I added the front pivots. I did not make it like in the manual as the bottom arms are supposed to be attached to the chassis in a previous step, and anyway, it is missing the front knuckles...


And basically I added the knuckles later on (one of the advantage going virtual is that you are absolutely not constrained by what is around )


And this is how my Hunter virtual build looks like at the moment...

[silvertriple]

After the front train, I made the bumper... The model was done independantly from the measures made for the bathtub, which will allow for a safe check on the bathtub...


And it is a perfect match...


It is now time to get back to the rear. I had my doubts on the gearbox still, as my own test shows that the shaft is rightly positionned at 24 mm from the diff center in my design.


That being said, I still have a doubt because the bottom part doesn't match. I decided to do the bottom part without looking at the dims I have for the chassis.


And here is the exact representation of my issue, now...


There is 0.52 deviation between the center of the circle of the 2 parts...

I recheck all the measurements of the top part. I can't move the slot, as its position is driven by the motor mount position, which are also driving the bottom part fixation holes...
I made 2 sketchs. As there is 2 hypothesis I can do:

• First, there is some added interdistance. 0.274 mm of additional distance is way too big, so it is not this

• secod option, the shaft is going deeper than what my measure says

That's the two only option I can think of now. I had a review of the shaft position within the chassis in real. And the conclusion is that the shaft has a bit of slope: if I put the motor mount on the shaft, inversed, and look at how much it is matching the chassis profile : the motor mount doesn't touch the chassis. This is the issue! Bad design, indeed.
And that also explains what I remember about the idle gears melting in a slightly conical way

[silvertriple]

After my last post, I corrected the diff position, and now it should work. I'll launch a final test print later...


I then model the Hunter Monoshock, and that was just before going to bed...


This morning, focus was to get all the parts of the rear train in, again with some specific parts to the Hunter


I then completed the transmission, with the original idle gear (I have some modified ones already), a 20T pinion (originally, there was 19T, 20T and 21T pinions in the box). There won't be prints or files of those ones as I have my Marui 2WD set available in upgraded module... And if you ask how I did this visualisation in an independant file, this is because the file I used for this was the one I did to design the Motor support, and it has the chassis already (master version).


I later added the universal joints and wheel shafts in the transmission file...


My virtual Hunter looks now like this (yeah, couldn't resist to add wheels)

[silvertriple]

There is only a few parts to complete the chassis in V1. Mostly, I will only have to do derivations for the V2, and the protitype will be slightly different (there is more work on this one).

Initially I wanted to complete the radio lid, but doing this I notice that there is a mistake in the center section of the chassis. I worked by symmetry, and there is nothing more looking like a cubic form than the same cubic form viewed from a different angle As a result my chassis is likely too short or two long of few millimeters and for its center section it is not large enough. Not everything is lost as I can rework this out later on. And that was the very first extrusion. second sketch was applied on the wrong plan... (at least this is a new one for me )

I therefore went to deal with the gearbox cover. I will have to print one to check everything is good. This part is a bit complex and it took me a bit of time...


here is the state of the chassis currently. It's missing the rear bumper, the front gear cover, the roll bar and the radio lid (the two parts I may put on hold until I reworked the chassis).


Anycase this is still fun

[Dadio]

After the front train, I made the bumper... The model was done independantly from the measures made for the bathtub, which will allow for a safe check on the bathtub...


And it is a perfect match...


It is now time to get back to the rear. I had my doubts on the gearbox still, as my own test shows that the shaft is rightly positionned at 24 mm from the diff center in my design.


That being said, I still have a doubt because the bottom part doesn't match. I decided to do the bottom part without looking at the dims I have for the chassis.


And here is the exact representation of my issue, now...


There is 0.52 deviation between the center of the circle of the 2 parts...

I recheck all the measurements of the top part. I can't move the slot, as its position is driven by the motor mount position, which are also driving the bottom part fixation holes...
I made 2 sketchs. As there is 2 hypothesis I can do:

• First, there is some added interdistance. 0.274 mm of additional distance is way too big, so it is not this

• secod option, the shaft is going deeper than what my measure says

That's the two only option I can think of now. I had a review of the shaft position within the chassis in real. And the conclusion is that the shaft has a bit of slope: if I put the motor mount on the shaft, inversed, and look at how much it is matching the chassis profile : the motor mount doesn't touch the chassis. This is the issue! Bad design, indeed.
And that also explains what I remember about the idle gears melting in a slightly conical way

I had a similar problem lining up the Sand Rovers bottom gearbox section (very similar design) , took me a while to realise the error was because of draft angles to help release the chassis from the injection mould , it really depended on where i measured it .

[silvertriple]

I had a similar problem lining up the Sand Rovers bottom gearbox section (very similar design) , took me a while to realise the error was because of draft angles to help release the chassis from the injection mould , it really depended on where i measured it .

Yes I tried to take that into account. In gearbox done in two halves, you generally measure everything in the inside, then define the outside from the inside definition, and that remove the issue linked with the draft angles. Here there is areas angled towards the up side (front of the car), towards the down side in the rear area, but that would be too easy : the gearbox inside is likely with angles upside... But the cause of the issue was not even that. The idle shaft is on side in the chassis and on the other side guided by the motor mount, and the hole in the motor mount is not at the same height as in the chassis. I did not even measure the angle for the variation, but the shaft was lower on motor mount side (and diff/gear contact point). I've modified the design and it is now horizontal (or at least in a parallel plan to the bottom of the chassis - because when it runs, I can't garantee that it is horizontal )

[silvertriple]

I fixed the chassis yesterday. The profile is now in line with the real one. I still need to check the full length, but both rear part (gearbox) is now matching original parts, and my center part should be almost fine as well. And then some of my linked files went mad... Actually one mainly went bad : the rear gear cover. To fix it, I finally exported in F3D, and make it a separate file. Thanks I did not have to redo it completely.

After additional checks, I printed one rear cover in PLA to check the dimensions were right before working out the front one... And it matches, so I'm pretty confident now my gearbox is ok.


It took me a while to resolve the file issue yesterday, so I was really only able to CAD today. Front gear cover is in, it took me a bit of time but it's in.




I then took care of the missing parts for Hunter in V1. Rear Bumper, rollbar, radio lid. and for the steering servo, I adapted the Big bear steering (which is mainly the same parts) to get the Hunter done.





Now, it will be time to take care of the bodyshell...

[silvertriple]

Marui Hunter, V1 & V2 - Spot the differences




[spoiler]
- Shocks mounts on front arms (V2)
- Holes behind servo mount holes (V2)
- Square (V2) versus rounded (V1) shock towers
- "MARUI" (V2) versus "HUNTER" (V1)
[/spoiler]

[silvertriple]

Before dealing with the prototype and all ellements I have noted about it, I wanted to finish the Hunter V1 and V2, and for that I needed to get the bodyshell and wing done.

I started with a solid body...


Then another one...


After that I started to pull surfaces together around that...


And it became this at the end


I detached the windows to thicken them and to get them in a different material, and proceeded to paint the rest of the body... The Wing was done purely in solid mode and here we have a bodyshell...


And the body shortly join the chassis...


The body for the Prototype should be very much easier than the normal bodyshell. I also need to work out the prototype rear end : the suspension were not using the monoshock in the prototype, and I will need to model a Mabuchi 380RS (which means find one first), as it is needed to model the famouls motor cover with the airscoop as well...

[silvertriple]

There was something missing on the bodyshell..


Now that this is done, another branch of the project started: the prototype...
From the pictures, I can see the chassis is black, and the nylon reinforced parts are in a sort of white/yellow resin, so I started by applying different properties to a subset of the V1 parts...


Then I pulled the parts from the cluster to model them, and complete with a spring guide, shaft and coil derived from the one I model from the front. I removed about 4 mm to th spring guide, shaft and ressort...


And they are now attached to the prototype chassis...

As mentioned earlier, this is derived from the master chassis file and it doesn't include the switch support (the bodyshell won't allow for it, and I believe it was added later on...

I just pull a Mabuchi 380, as I need this and a modified motor mount to be able to pull the prototype rounded gear cover with the air scoop and the exhaust... It was also visible on some preproduction near final model with the monoshock and grey chassis...
This is the reference picture I'll use for this...


That will be another fun part of this project...

[silvertriple]

Before doing the first prototype body , I had to tackle the specific gear covers...

I started to reproduce what I could see easily : the exhaust and the piples...


Then I assemble this with the bottom of the rear cover, and tried to think about a way to make it work...


As I found the side were quite nude, somehow, I decided to add airboxes...


And that was it. I'm quite ok with the result, and there is not much more I could see from the pictures...


Once that was done, I pull the bodyshell, did a profile for the front gear cover, and started to work this out


and at some point I had to define the position of the airscoop...


It is not exact repro of what is on the picture, but that would work...



It fits with the production bodyshell, and as I could not read the markings, I just wrote Marui Hunter Proto - which may be quite possible, as Proto was the company of the designer of this car...


Next is the prototype body. I need to check if I reuse the production roll bar or a different one... But at least, I have my chassis ready for this...

[silvertriple]

I spend a lot of time in Fusion 360, with only the very few inputs from a quality picture...


Obviously, the chassis and other elements from production models hints about a lot of things, but I also want this body to be 7.2V stick packs ready (which I suppose was not the case when they started to work on it)...

My first attempt looked like this...


There was a few things I was not really happy with, but I pursued the work to get all the additional parts I needed such as the roll cage, and the wing...


I even put some sticker on it to see better how it would look like...


And on the car :


Yesterday, I did it differently...



And I lkied it better. The lateral decks are longer. I'll need to check, but they might be usable with a production chassis...


But there is still somthing I thought required an improvement... The bonnet was a bit too flat to taste.


And here is the V2 on the car...


The result is ultimately different from the prototype, and it is more an evocation of what it was, and printed, it should work wity 7.2V stick packs. The wing support may not last long, but I will consider printing the roll cage in TPU rather than Nylon...
And I will try to pull another motor cover in order to be able to use a 540 motor... (And yes, I think I have some envy to get one printed !)

[Dadio]

I really like what you did to modify the body shape , the undercut on the sides is something that the Rough Rider body style really needs , very nice work .

[silvertriple]

I really like what you did to modify the body shape , the undercut on the sides is something that the Rough Rider body style really needs , very nice work .

I may have added some over-engineering into the mix as well : when you look at the rough rider body, it is actually super simple to redesign in cad and to modify it the way you want (after all, it's mainly pannels assembled together)... So that's something that could be ultimately done easily to make a custom body... And if this fuels some ideas on your side, don't hesitate, it is part of the reasons I post those elements all around the web