Hirobo 44Bs and Zerda :)

[Dadio]

It's all looking good there Mark , the front knuckles are another weak spot , the steering arm snaps off the knuckle , again the later Alien Mid and Invader have a substantially reinforced arm on the knuckles , if your putting this on Thingiverse etc then it might be good to offer a reinforced version too .

[silvertriple]

It's all looking good there Mark , the front knuckles are another weak spot , the steering arm snaps off the knuckle , again the later Alien Mid and Invader have a substantially reinforced arm on the knuckles , if your putting this on Thingiverse etc then it might be good to offer a reinforced version too .

Have no clue yet. At this stage I have the Zerdaish chassis still assembled, and the short wheel base 44B chassis is in the same state. I'll have to get thru the tear down soon.

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).

[silvertriple]

remove as duplicated

[threesheds]

This shows front anchorages zerda and 44B

Rear zerda shock plate orientation allows cage around the shock.

[silvertriple]

It's all looking good there Mark , the front knuckles are another weak spot , the steering arm snaps off the knuckle , again the later Alien Mid and Invader have a substantially reinforced arm on the knuckles , if your putting this on Thingiverse etc then it might be good to offer a reinforced version too .

As said, doing the model first... And will reinforce later. I will have 2 chassis to complete, so indeed will do some prints, and likely reinforced ones...

[silvertriple]

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.

[threesheds]

Some plusses and minuses. Zerda deck a bit butchered but you have parts which didn't survive on my two zerdas. Greater sense of achievement when you get it running. Will you be aiming for original electrics or modern ESC etc

[threesheds]

CT90 belt cover offered up to 44b . Would fit with careful trimming

[silvertriple]

CT90 belt cover offered up to 44b . Would fit with careful trimming

Screenshot_20221107-113237.png

Thanks for that picture, that confirms it is possible, like on the Zerda, and as well the explanation you gave on Facebook seems totally plausible... I asked many of my friends around, and no one have a 44B with a belt pulley cover...

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%2044B%20Rock'n'City%20MC%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...

[silvertriple]

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


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.

[silvertriple]

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.

[silvertriple]

And I forgot to include this view, which I like a lot

[Dadio]

They really did torture the belt in these cars , when you compare to later cars like the Mini Mustang .

[silvertriple]

They really did torture the belt in these cars , when you compare to later cars like the Mini Mustang .

Especially if we consider than the 3 rollers to change angles of the belt were not on bearings...

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.

[silvertriple]

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...