Hirobo 44Bs and Zerda :)

[silvertriple]

Well, I just put one detailed picture of the Zerda at this stage... I'm not even talking about the metal bent out of the box and far too easy to unbent or bent in other dimesions than the original bent
They would have made this part within elastomers, I'm not sure it would be that different

Indeed, that is part of the elements to improve on those cars... That being said, the red plastic parts on those cars were very brittle, as the plastic did not include reinforcement agents. Getting them today in similar material with just the proper reinforcements agents maybe enough already to get them strong enough (taking into consideration that making something stronger does indeed move the weak point somewhere else so this has to be thought carefully).

[Dadio]

In the later Alien mid and Invader they used the same suspension geometry as the Zerda but significantly reinforced , the suspension arms are much thicker and the suspension mounts on the bulkheads are greatly reinforced , the suspension components for the Alien Mid and Invader are a drop in replacement for the Zerda, the front bulkheads fit but need longer pins for the arms due to the mounts being bigger also the belt idler pulley has bearings in the bulkhead in addition to the pulley as the steering linkage goes through the front transmission at that point , an odd setup but if you use the Alien Mid bulkheads on a Zerda you just have to add two bearings and block the axle hole , I've used the Alien Mid front bulkheads on my Zerda and can show pictures if your interested .

[silvertriple]

In the later Alien mid and Invader they used the same suspension geometry as the Zerda but significantly reinforced , the suspension arms are much thicker and the suspension mounts on the bulkheads are greatly reinforced , the suspension components for the Alien Mid and Invader are a drop in replacement for the Zerda, the front bulkheads fit but need longer pins for the arms due to the mounts being bigger also the belt idler pulley has bearings in the bulkhead in addition to the pulley as the steering linkage goes through the front transmission at that point , an odd setup but if you use the Alien Mid bulkheads on a Zerda you just have to add two bearings and block the axle hole , I've used the Alien Mid front bulkheads on my Zerda and can show pictures if your interested .

Pictures would be indeed interesting anycase, my friend

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...

[Dadio]

Those rear gearbox sides are a very complicated shape , it took me several attempts to get it to match and align with an original , yours is looking good .

[silvertriple]

Those rear gearbox sides are a very complicated shape , it took me several attempts to get it to match and align with an original , yours is looking good .

I always start by some dimensions i'm 100% sure about. The shape is indeed complex, but once you put add geometry constraints in this (circle diameters and tangent rules), it is easier...
That being said, I'll probably go for a test print of this part, as I have a doubt on the shocks plate fixation position.

[threesheds]

I don't doubt you have the plate/rear damper stay fixing point correct. I envy you CAD experts. I see from manuals the stay or plate differs between zerda and 43b ie. Part nos. begin. CT and ZR
The ZR is black and the zerda manual lists both parts. I reckon any difference is negligible. I thought the zerda one should have bends but as I now have two zerdas it seems a previous owner must've bent the stay or from collisions. Another little job for the pliers.
The bent stay definitely someone's idea of a mod as the japanned finish was wrinkled. Straightened out wiv me big 'ammer

[silvertriple]

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...

[threesheds]

Not new but two used ones very similar smooth finish. At least 2 layers of paint removed. There's a nice pic Google images of one with "HIROBO" engraved on it
[attachment=0]Screenshot_20221104-180804.png[/attachment]

[Dadio]

It's very easy to make those bumpers , it's just 3mm Kydex , you can get it on eBay , it softens in an oven at 150°C or if you just want a bend then a hot air gun works very well .
Mark there is a piece of software called GOM Inspect that is often used in 3d scanning that compares digital models , I don't know if there's a free version but if there is it might be fun to compare some of our models to see how close they are .
https://www.capture3d.com/3d-metrology-solutions/3d-software/free-gom-inspect
It is free

[silvertriple]

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...

[silvertriple]

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 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


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

[silvertriple]

As mentioned by @threesheds, 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...

[threesheds]

On both my zerdas the shock anchor is toward the front but the shock is anchored to a point behind the hub carrier.
I also think I have an old arm with circular anchor point which may have been an earlier weaker design.
I don't know what changes to geometry would result from reversing the arm and using the anchor on the arm, probably raise the front of the buggy?
In any case your copy is correct.
Pics in my thread show the roughly altered front suspension with shocks at the front of the arm and modified shock towers.
Just looked at your zerda image, same as mine anchored to hub carrier

[silvertriple]

Rear arms are the same for both Zerda and 44B.


I'm not sure for the Zerda, but on 44B, shocks are 70mm front, 92mm rear. The position of the rear shocks anchor doesn't change much considering there is a pivot ball on the rear of the arms next to hub carrier, but the anchor position seems unlogical on the Zerda, as the gearbox side have a cut parallel to the shocks anchor... I don't see reasons for the change at this stage. Maybe I'll have the answer with roll cage of the Zerda.

[threesheds]

I or Dadio will post pics of the rear of zerda showing roll cage rear bumper going around shocks. It won't interfere with your stripping down, scanning etc. Roll cage elements would help understand it maybe. It's the main missing part of your zerda?
On your zerda the rear shock support plate is installed back to front and that will obstruct the roll cage. Probably been altered to match 44b and maybe make putting a bodyshell on easier?