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Hirobo 44Bs and Zerda :-)

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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.

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

threesheds on rc10talk 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 on rc10talk: 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 :-)

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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...

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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...

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First, because Dadio mentioned it on rc10talk, 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...

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Yesterday, at the end of my working day, I started to put all the key dimension of the rear gearbox right side (I had one from the set of unused parts).

Added a few things in the sketch, and then proceeded to extrusions, and revolve, all based on the same single sktech.

Next was to complete this with additional sketch and detalis (the is a setting here, I suspect it is for belt tension, i'll look into this in details later, as I need to tear down one of the complete cars to find out).

A bit more work later, I completed the part with the suspension arms fixations and with the finitions...

At this stage, I do not have anymore separate ports for 44B on the table, and I would need to tear down one of the two 44B chassis to get more. On the other side, I have some Zerda parts in the bag that came with the car : one right front gearbox side,  front suspension arms and the Bumper... I may start by modeling those...

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Ten minutes during the post lunch coffee was put to profit to design the Zerda bumper based on 3 sketchs and 3 extrusions...

I'm not even sure I spent 10 minutes doing this...
If anyone has a NIP/NIB Zerda bumper, I would love to se some pics of it's underside and from the sides : I'm debatting about the ends being used by runs or being done a certain way by design...

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After my day of work, I got the bag of parts fetched the front gearbox side from the zerda and compared it to the one from the 44B chassis.

The idea was to respond one single question : Should I get thru the remaining parts in the Zerda bag (front gearbox side, rear arms) or should I pursue on the 44B. I decided to get the incomplet chassis tear down to get at least additional components I need to pursue on the 44B. For the Zerda, I would start with the chassis, most likely.

Next part is going to be the left gearbox side... I decided to take a mirror of the right one and to derive it from there.

First I removed what was specific to the right side, and then built speicifities of the left side. It did not took much time, and another part is in.

I completed it with the pivot ball support which is different from the right side...

Next is to deal with the suspension arms and hub carriers, knuckles and so on... For the transmission, I have a lot of elements being done already, and I would also need to tear down another car to complete this because the rear of the incomplete chassis was missing the full transmission...

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Gearboxes being done, I thought it woulb be worth to put the parts together and to do some dimensional checks.


The check was quite efficient to spot the mistake : bath tub position was 1mm off, and rear side of the bath tub was .5mm off as well. And one measurement on the rear gearbox side was also wrong from .5 mm... It was quite easy to fix (each part is a separate file, the main file is updated with the content of each part file. Easy fixes done, I put the arms carrier and knuckles on the table.

The design is really simple, first, and front is just a variation of the design of the rear ones. It's easy to get that from a copy of the file, we just have to change the reference offset for the sketch used to define the shock fixation.

Front one was done in 5 minutes from the rear one.

Then I made the rear hub carrier. A small note : I have a very simple nomenclature for the parts name : Prefix is 44B for specific 44B parts, ZER for specific Zerda parts, and COM for the ones common to both chassis.
The rear Hub carrier is common to the Zerda.

Then comes the interesting part mentioned by Dadio on rc10talk earlier : C-Hub holder with caster adjustment, the C-HUb and the front knuckle (made as close as possible as the original - I know Dadio made one reinforced already :) )

The C-Hub holder has some marks for the caster angle settings. I've tried to be as close as possible of the reality. It should be very close (and if it is not right, the difference is about less than .5 degree)

Next was the C-Hub, with i's arrows to define the setting... A marvel of over-engineering :-D

And if you put them together here is what you have, with different settings

Next was the knuckle...

And we have our front carrier assembly...

Last is to include this in the chassi file and to get the joints in...

Not much parts to model again, I will need to tear down something again :-)

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44B front arms are slightly different than Zerda ones. Rears are shared between the two cars.

44B Front arm
Zerda Front arm

44B i shorter and the rear pipe is perpendicular to the suspension axis. This is not the case on the Zerda, where it is longer, and there is angle between the rear pipe (on the picture) is angled differently. Another key difference is that the Zerda arm will be mounted with the shock anchor at the rear while it is at the front on the 44B...

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Yesterday, I started to work on the transmission. I have already part of the gearset. Included diffs and modeled some parts. I have the 50T pulley arleady as it was used as well on the Bearcat. I will need to build 18T and 14T pinions, and extract the shaft from the 44B or the Zerda to measure it as well as the tensioner parts...

On the wheels end, I have already the axis models as they are the same as the Bearcat... Not much is missing anymore to have a complete chassis in Fusion 360.

I will need to review the bath tub rear end profile. It is supposed to act as belt cover and get against the gearboxes side wall. I already tried to modify it to work out a a gearbox side profile offset, but when doing this, the shell doesn't work anymore. I will need to find another way (maybe time to pull the Dadio's function aka export reimport the model :-). If this doesn't work, I will have to do it the hard way (thinking about splitting bodies and do the rear end in a separate body to ease the shell function - what is disturbing is that the display looks correct but it fails at the end).

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I did not touch Fusion 360 this afternoon. Deployed a table in the living room in order to deal with the tear down...

I decided to tear down the two cars.
This is the 44B-SWB in parts

At the end I separated the parts which require modeling for both Zerda and 44B chassis (or actually those which were not yet modeled). Here is essentially what is left on the plate at the end.

In terms of belt, for the motor end :
44B  : MXL 91-6.4
Zerda  : MXL 92-6.4
For the central belt :
44B-SWB : MXL 280-6.4
44B-LWB/Zerda : MXL 336-6.4

It seems the servo horn on the Zerda was fix to nothing. That explains a bit of things. 

And it's not the sole issue of this car, unfortunately. The Zerda has lot more issues than what I could see initially. There will be much more work than expected.

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I asked many of my friends around, and no one have a 44B with a belt pulley cover but the part used on the Zerda is referenced CT-90, which denotes City (CT) and the 44B chassis (City was the first car released with it. I checked the bath tubs and none of them have holes to fix the pulley belt cover like I found on the Zerda. 

At the end, I found the reason, in the first Model Cars Monthly I scanned more than a year ago. Aprli 1984. There was a track test of the 44B rock'n city (you can find that track test review here : https://www.overrc.com/vintage/documentation/archives-de-mike/Hirobo 44B Rock'n'City MC (1).pdf on overrc.com). In this magazine, the same month, few page before, I was able to find an advert that is actually explaining it completely.

CT-90 Belt Pulley Cover was an option, available when the rock'n city was released on the market. That explains the lack of hole on the bath tub, as well with the fact the cover was not trimmed and drilled out of the packet. This required some search and took a bit of my time today.

Model wise, I had some progress yesterday night and today:

Tension adjuster is modeled

Once this is done, I  pursued the target to have all transmission part in (except the belts)

I also added the motor and the 14T pulley. The optional 18T pulley is there one the side.

Here is a view from the top

Today I added the servo saver assy

Well, i'm missing front and rear belt covers, all pivot balls, tie rods, dogbones and shocks, and some metal parts.. But It is taking shape progressively...

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Today, I started by reviewing the bath tub. I reveiewed the profile differently, and the sheel worked this time...

And now, it participate to the protection of the belt cover

While at it, I also tackled the rear belt cover. It's a very simple plate, but basically, you need to have almost everything in so you can do it.

Next was another hard part : The front belt cover. You have to understand how it is positioned and where it interacts with the radio hook or other parts to make it work (basically to make this part you have to have the chassis, the gearbox side, the diff and the belt roller, the cross member, the radio box hook and the bath tub).

All is on the chassis...

Time for a section analysis...

Next parts are mostly do it once, use it many times... So it should go quicker than this single part, and there will be shocks.

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Today, started to deal with the upper arms...

That was quite easy. I did one, and did some copy paste with amendments of the rears' length.

Next was about the steering rods. one of the pivot ball is on the side, as I did not search the servo to add in the bathtub

I'm not sure the geometry is perfect, but I do not have the tie rods of the 44B-LWB and derived this from the manual information...

Then built dogbones... I did not put them in place, they are on the side for the moment...

I also took care of the rear belt, which is currently visible and will be kept visible as the the belt cover will be made transparent.

Then I took care of the front belt. The idea is not to have the possibility to print, but just to be able to show how this works...
To make a belt, I do a sketch on the mid plane of the belt. I include in the sketch the intersaction with the plan for the main pulleys and diff, and as well the roller which are used to deal with change of angle of the belt...

Next I do an offest of this corresponding to the thickness of the belt and I will do an extrusion of this. Next step is to create another body, which is one of the teeth of the belt, and do a pattern on path on the inside of the belt...

And I have the belt, and it's circonvoluted path...

Enough for today, tomorrow will be shocks. I'll have to tear down a front and a rear for this.

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Today, I sarted by the wheel. I did adjust the profile of the spike with some fillets, added the markings and make the rim.

Next I assembled shocks. I could eventually print the red parts, but I'm likely to replace the shocks by some Kyosho Legendary series when I rebuild this car.

NB: the springs are progressive, so normally the model should be slightly different for the spring : It would require to make it in 5 different segments...

Then I added the wheels on the chassis

And then the shocks

Servo is still missing, some screws, the body mounts and the bumper and a body shell... It still a lot, but I'm focusing on the chassis first.
Not sure if I do the Zerda or the 44B-SWB first for the next in.

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Yesterday, I did not have much time to work, but I did spend some time to work on the SWB version.

First, the chassis plate: once you have the dimension right form most of the functionalities it is very easy to derive the missing ones from the rest (made a small mistake that was easy to spot at the next part being done, so the picture is incorrect).

Then I started to work on the bath tub. It is easier than the LWB version, so it should be fast. First, I put in my file the chassis plate, front and rear gearbox side, to have all the key dimensions, then I draw the profile and did some extrusions.

After having done all the key extrusions to include all the key recess on the side and under the tub, I applied a shell and applied the inside features

Next work was to finish it by applying the fron t feature first.

And few minutes later, rear features were done as well...

At the end, this was quite quick to do... The fact of having all the dimensions around and the learnings of the LWB mistakes I did allowed me to gain a lot of time...

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This morning, I did add the switch slot. I made it for a single reason : by doing it, it would be esay to do another version depending on the switch you want to use.

I decided then to tackle one of the part I don't have. I've looked at pictures on internet and derived from what I saw and what I know from the design and the LWB bath tub design.

The design is made in a way that would allow to revise it if someone provides me better measurements (there is basically one sketch to review for the profile and one extrusion for the front, the rest is totally derived from the bottom design)...

Next : bumper and winch :)

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I said bumper and winch next...

Bumper was quite easy...

But the winch took me some time... There is a lot of details... and possible mistakes to do in key measurements

The details are small details, and it requires quite a work... There is different ways to do the rope, I decided to draw a sketch with all of the rope details and do a revolve.
Then I added other details

And it took another bunch of time to deal with the hook...

At the end, I have all of it...

I will do the City bumper as soon as possible, and I need to find a Vega bumper as well...

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Having all key parts for the SWB chassis, I decided to assemble it... Joints is definitely not my prefered thing in Fusion360, it takes time. But on the other hand, it allows to spot the mistakes...

Started to put the transmission and gearboxes together with the short chassis.

Then I put the radiobox...

F*!  I have a big mistake here... I took the part, its file and rechecked all measurements... multiple times... Seems ok????!!!? What is that? Both transmission are the same at the rear end, the only possible issue is the bath tub. Then it's obvious! And if it was not symetric, as I made initial measurement... 

The LWB bath tub is symetric, the SWB bath tub is not.

Modifying the file itself then was quite easy: modify the extrusions, and check all plans reference in sequence...

And we have now something that seems more compliant. I also added the bumper the motor and the shocks anchor at the rear.

Next was the suspension arms

And the shocks

And the wheels

And the SWB body mounts

Currently missing : steering servo, servo saver and steering tie rods, and a body shell...

Looking at the file and knowing one of my friends is doing skeleton cars to make the internal beauty visible, I decided to see if it was worth considering a clear radio box....

Maybe the belt color should be different, or the chassis, but it may be an idea...

I will add the steering missing components and will migrate to the Zerda parts I need to model next... Beside the roll cage, I will need the chassis, the topdeck, the battery plate, the belt cover, and the front C-hub and knuckles (front arms are already available). It should be not much work, actually...

On the 44B side, I will need to find some pictures of a Rock'n Vega bumper to  model it, model the body mounts of the Rock'n City, understand how the Lancia and Baja shell were mounted as well...

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I got a city bumper delivered today.
It was not very long to model.

I also have the City roll bar

Then I derived a Vega Bumper from what I could see from the pictures I found on Internet
(not sure how accurate it is).

I tried to put all the 3 chassis in on single file, and it seems (con)fusion360 doesn't like it :-D

Next I took on of the Zerda parts I still have to do

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Today, I started with one big part : the chassis.

I took a projection of the rear of the 44B chassis and started to define the rear central side.

Then I did a different body for the front side...  After the bodies were merged, there was no way to do a shell, Fusion360 did not like it.

I went back and applied the shell on both bodies before merging them...

Then a bit of work later, I have some of the elements of the chassis

The pipes work seems to be more complex than I expected. First this will require some heavy 3D skectch work to do pipes, split them, add the needed part to the chassis, then another 3Dsketch to deal with the removal of the smaller pipe... Heavy work for when I'll find the courage to start this... If someone gets a better idea, please talk :-)

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After a night to sleep on it, I decided to pursue. The approach for each pipe :

  • Set a 3D sketch for each pipe, with the ends of the pipe being different segment, with the idea of using the same sketch for the big and small diameter pipes (this one needs to be smaller, as there will be a fillet applied at the pipe ends

  • Hide the main body, and do the big pipe

  • Apply the fillets at the pipe ends

  • create a sketch on a plan perpendicular to define an extrusion to remove the top half part of the pipe

  • apply a mirror to the pipe body

  • Merge the two bodies with the main body

  • hide the main body, and do the small pipe

  • apply fillets at the pipe ends

  • apply mirror to the pipe body

  • unhide the main body and substract the small pipe from it


And this is done. Obviously, you need to apply this twice as the cut plans are not the same for the central pipes and the side pipes...

Once done it a last detail is to be added : the roll cage center fixation.

The Chassis is now done. That being said, those nice pipes look like an "unsuccessfull attempt to make the chassis more rigid" :-), and the main uncertainty resides in the chassis dimension side to side. All holes are in line with the measurements I gathered on easy elements to measure where it doesn't interact with the flexibility of the chassis, and the only exception to this is the roll bar fixations holes. But it is in correspondance with the roll bar measured dimension, and as well more or less in correspondancy with the pipes... So it should not be that far of it...

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On Thursday, after some Fusion360 issues, I started to put my Zerda parts together. It's somehow mandatory to be able to tackle the belt cover part, the top deck and the roll cage.

And then I started to work the belt cover. First with a projection of all the part, a few extrusions and sketchs later, It was there...

The fact is that with the slots rather than plain simple circle holes on the front of the chassis, you have to take into account for the possible range of possibilities for the belt cover to fit in. Apparently, looking as some measurements at the front they did, but the single fact the front fixation point is not a slot shows they did not went to the end of the thinking (i replace the circle by a slot)...

I then continued to put the part together...

But there was a problem...

It seems I used a wrong reference point to measure the front of the chassis (I actually measured it under the chassis, while I sketched the inside of the chassis). This is a mess :)
But it was actually worse than this. Even modifying the timeline, I was not able to get my chassis back together because the shell did not work anymore, and I did not understood why (sometimes it happens).
Long story short: after mutiple tries, I started back the chassis from scratch, and replace component in the file so I can review the belt cover...

It took me a few hours to deal with this. This morning after midnight, I finally had my chassis and belt cover together and lining up where it should. &nd I continued to put parts together...

Then I tackled the top deck (it's bent, rather than flat on the rear side, but it is how it should be).

Next I tackles the roll cage (with the position of the front brace deducted from a picture provided by my friend Ryo)

Here is where I am, currently.

Remaining part left :

  • front shocks supports, and the brace linking them

  • Number plate and support

  • Zerda C-hub

For all the other parts, I have them already... This should not take much time :-)

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