Hirobo 44Bs and Zerda :)

[silvertriple]

Hi

It's definitely time to start a new thread today. Not that the Bearcat SS is finished (it will be soon), but because now I have started some work on the 44Bs and Zerda chassis. I'm very happy as I like to work on car with chassis variants simultaneously...

let's recap first what we have.

First a Zerda with a broken cage, and some tender loving care needed. It cames with the orignal wheels, the broken elements missing from the roll cage puzzle, a Beetle MRC body shell... There is some work for sure. The rear shocks are rears from a Super Hotshot. I might discover additional details later on...



Second, some 44B chassis unused parts.



And today, I got some cars joining the crew, including two 44B incomplete chassis.


Let's detail the Hirobo 44B. A Hilux - SWB, and a LWB incomplete chassis :


The 44B Hilux chassis is missing the top of the radio box, but beside this looks complete. The bodyshell is in pretty bad shape, but some key accessories are present, and will allow to create STLs.



The LWB chassis is incomplete, but I don't see too much issue there at this stage.

[silvertriple]

Now that the elements are introduced, let's kick it.

@threesheds provided me tire dimensions, so I modeled the 44B tire




The tires of the Hilux are original and in pretty bad shape, but they have the elements which should allow me to pull the thickness details...

The Zerda wheel was sitting on my desk the other day, and I decided to put it in Fusion 360



The tire is derived from the depleted tires and the measurements of the Bearcat spikes provided by @GoMachV : the spikes are the same as the Bearcat/Tomcat's ones

Yesterday, I started to model the 44B chassis (the two 44B chassis I got today where not yet known facts )

CHassis plate first


Then Belt cover


This morning I decide to do the bathtub





That's where I am currently... a lot more and more and more is to come in terms of models

[Dadio]

That's excellent work Mark , that radio tub took fantastic .
I know I go on about it but give those red nylon parts a good long soak in water , Hirobo nylon really does get brittle and the bulkheads snap at the lower suspension arm mounts regularly .

[silvertriple]

That's excellent work Mark , that radio tub took fantastic .
I know I go on about it but give those red nylon parts a good long soak in water , Hirobo nylon really does get brittle and the bulkheads snap at the lower suspension arm mounts regularly .

I'm definitely aware about this . And for the bath tub, i was surprised actually as it did not took much time to get it done... I'm going to pursue on the parts already at hand before the tear downs. Intention is to have the 3 chassis modeled 100%.

For the 44B bodyshells, that's another story. I took pics with measurement of Vega, Rock'nCity and Lancia 037 shells as my friend was having those at hand (he is really an Hirobo fan, he have a few Zerda and 44B there )

[silvertriple]

We have the the bath tub. With a cover, it will be the radio box, so let's cover it

First let's define where we are going to seat this on the mid plan of the Bath tub


Then, next step is to deal with the main profile (which I changed later on as i thought a parallel somewhere that was missing as constraint)


After that, let's do extrusions


Next is to remove unwanted stuff

(nb, not fully happy with this, I need to review some measurements...)

Once there, fillets and shell are applied


And it's almost done. Remain some features and holes to add and work is done...


And the radio box is complete...

[threesheds]

Re LWB bumper, yes quite different on reflection.

About 172mm length

[threesheds]

Mine needs a zerda bumper really as it's now a hybrid

[silvertriple]

I'll model both 44B version and the one from the Zerda (I have it in a part bag, that came with the Zerda wheels). I may be able to model it quite quickly, as I don't need to tear down a car to do it... Watch this space

[silvertriple]

After some RC unrelated stuff that kept me busy, I went back to the laptop at the end of the afternoon...

I still have a few parts remaining alone from the unused set of parts on my desk which I will model before I get to tear down a car.

Receiver mount plate (only for LWB chassis, the SWB is having a different radio box). It's pretty easy, and I used it to validate again my bath tub. At its largest point, it measure 58.5mm. The bath tub at that place is sloightly more than this, and my desin at the same place is exactly 58.5 : after further analysis, the bath tub has a variable thickness. In this area it is 1 mm and not 1.5 mm like everywhere else. I decided not to change anything...

In the meantime, I did the receiver mount plate and I removed .1mm on the area where the issue exist. My model is not 100% perfect, but that should be ok, even with a original receiver plate.


Then I reveiewed the radio box cover...
It's much better now and it is in line with the original cover.



Not sure what I'll do next...

[Dadio]

Have you done the adjustable caster front hub carriers ?

[threesheds]

Looking at rear damper stay on 44b,s and comparing manuals of 44b and Zerda. Zerda has the stay fitted reverse to the 44b in manual illustrations. I wonder if it's an error in the 44b manual as the zerda method offers a better angle, alignment and clearance of the damper to the suspension arm. Unless this was to make fitting bodyshells easier on the 44b?

[silvertriple]

Have you done the adjustable caster front hub carriers ?

At this stage, I've not started anything on the arms and other mobile equipment. I'm likely to finish the 44B parts I have, and get one of the car in parts. Probably the LWB first, as it is really incomplete. First element is to model as is, and then work on the improvement. I've not looked yet at the hub carriers...

[silvertriple]

Looking at rear damper stay on 44b,s and comparing manuals of 44b and Zerda. Zerda has the stay fitted reverse to the 44b in manual illustrations. I wonder if it's an error in the 44b manual as the zerda method offers a better angle, alignment and clearance of the damper to the suspension arm. Unless this was to make fitting bodyshells easier on the 44b?

I have no clue yet : the rear cells are identical. That said, my Zerda don't have the original shocks at the rear, so it is difficult to say at this stage. I'll ave a look at some point

[silvertriple]

First, because @Dadio mentioned it, I had to fetch the pdf for the instruction manual of the 44B to check something at my coffe break...


Indeed I will have the possibility to model this. It was an option for the Zerda, but it was standard on the 44B. I said some friends I love the 44B because as per my understanding, this chassis is the first 4WD offroad EP car, and out of the box it had most of the genetics of the modern cars. This possibility of caster adjustment is just one confirmation of it. And while chatting with friends about this (they were discovering this), they were asking why it was not reproduced on many more cars later on to the point to be a standard. My interpretation is the Hirobo plastic were prone to fail, and it did not help, and for that specific feature, my guess is that either it was too tight and who break quickly in a race or not tighten enough, and the C-hub would easily acheive separation... And that is likely why we did not saw more of it.

Lest get back to the model...

First the Radio box hook, which is specific to the LWB chassis


Then another metal part, not presented here.

Last I started the side wall of the front gearbox. THey are symmetric, and I will need a set for one of the 44B chassis, because i have some broken on one of the 44B chassis, and the Zerda has the same weak spot...


Anyway, let's go. A sktech on the mid plane of the fixation point, some extrusions and revolves (for the fixation holes), another midplane, additional revolves, and most of the elements are done


It remains to deal with the suspension arms hooks and the additional features


Last we finish by adding some finitions...


Only one part remain now on my desk before I have to fetch on the Zerda additional part bag or to tear down a car...

[threesheds]

I don't think they put adjustable castor on zerda because it has castor angle on the front of the chassis plate. I guess no harm in having adjustable castor on a zerda but I haven't compared any effect on dogbone length and Zerda/44b front suspension arms are different lengths anyway. Is adjustable castor hub carrier weaker than zerda? Two parts instead of one? Maybe I'll swap between my buggies to compare.
Thinking of having a modern shock tower arrangement on the 44b to fit the 40mm centres of holes for shocks. As a cross brace should add strength to shock anchorage! And something similar could be designed for front shock arrangement on zerda as everyone criticizes the shock upper anchorage which bends easily. Early pics in my zerda from wreck to runner show a bodged shock arrangement which I inherited. Comes down to seeking original design or mods