TOPIC:

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...

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...

I love your work.  And your speed to modelize parts....

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

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...
 

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).

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.

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 : www.overrc.com/...%20(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...

Toop

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.