TOPIC:

How you do this Marc, is beyond me.

Have you been thinking of making a short Youtube clip on how you are doing one segment of any project?


On the subject of rear axle.
Would it be a idea to construct a modern version of the gearbox, orginal looking, but with modern gears that might be more obtainable?
Never driven a Big Bear a lot, just a short test drive of my mates in the early 90s, but the rumor says the diff were weak of the version one, and a bit stornger on the updated version.
I will need to go back and figure out the drive rations a bit late, the job I started earlier.

 

Richard, you know how to draw parts on the paper, I'm just doing the same in Fusion 360. This is basically no different. For simple parts it is easy. There is things slightly more complex, which requires to define a plan different than the 3 usual plan, but once you get the trick that is easy...

I may try to do a short clip with the modelling of a part... But it may be more work to assemble the video than to model the part for me . It would requires to see how I measure things as well...

For the big bear gears, one of my friend has provided me the Big Bear differential in V2 version. I'll model it and as well the V1 version, but beside the diff on the Big Bear, the main issue on those cars is the same as the Hunter and Galaxy : the idle gear is the one wearing quick, and this whatever gear ratio you use (there was 2 possible ones) : this is the part requiring replacement, really, as well as the motor pinion : they are in a certain metal alliage called Zamac which was not bery reliable. Just redoing those pinion and idle gear in steel may be worth the effort...

Today, I started working on the Big Bear rear arms... Again it is quite easy to read and to draw. I applied the same process as for the Super Wheelie : started by the left one, then took a mirror and changed what was required to make the right arm.



And then we have the Big Bear rigid axle assembly...




Once this was done, I opened a new file to deal with the Super Wheelie gearset...
I started by the diff main gear. 60T, module 0.6 (on the Big Bear V2, they changed and made the transmission on Module 0.8)

This was quite easy to deal with. 

Next was to complete the diff with the bevel gears. All four are 20T (on Big Bear V2, there is 5, but that's for later), which means it is 45° cone.


Later I had my differential completed...



I then completed the transmission, but doing so, I decided to add some ball bearing casing in the left gearbox (in V2, they added one one the right side, behind the motor plate, but not on the left side).


And here is the elements I added in the gearbox and rigid axle...


Here is the gearbox without the left part (without and with the gearbox plate (added in 7.2V versions)...



And the left part with its content without the idle gear...


And the gearbox is complete...


I did further checks (in real, with all in place in the gearbox) : the diff is moving over 2 mm, and is going in contact with the motor plate. This is in line with the model as figured out on the section analysis : my model seems correct.


I would add some washer to avoid any issue : .8mm should be good.



What should I do next : Big Bear transmission or something else?

As a good friend of me allowed me to have my hands on a Big Bear V2 diff, I did model it.

Small bevel gear are 18T, there is 3 of them, big bevel gear are 27T. They are in mod .8.


First, I started by the easy thing (this is a circular pattern, nothing more complex here).


Then I started to work out the bevel gears 


and a few sketch later...


And with axle (of a differnt diameter for the Big Bear)


Here in situation :


You may note that there is no motor pinion and idle gear yet : I have no clues what they are exactly, except the mod .8. I will have to find out, but I have no gears for this.
Based on the fact the Diff has similar diameter than the 60T mod .6, the smalle gear should be 10T mod .8 to be in correspondance with the 11T Mod .6 of the original idle gear...
The rest is however unclear, and I may have to wait my friend to get back in his big bear transmission to get a view of the reinforced transmission remaining...

In the meantime, I have my axle and diff enclosed in the rigid axle.

Finally got the required information to complete the Big Bear V2 transmission thanks to a canadian friend.

Idle gear is 9T/25T mod .8


Motor pinion is 11T mod .8



Once there it was easy to put it in the rigid axle assembly to get it completed.


This time my rigid axle innards are complete... It will be time to take care of the rest...


Speaking of that, I started to model the suspension shaft, and the other accessories. The spring are not exact modelisation. I will come back on those later.


I also started to pull a chassis, and start the virtual build with joints...


And basically, this is highly experimental for me. It is sometimes already difficult to joint a shock with pivot balls at each ends, but here it's a pivot ball, and the combination of a cylindrical and a slot, and it's not working the way I want (and I'm not even speaking about the second shaft...

I decided to cheat and I locked the suspension


and I did the same at the front


For the Big Bear, the next elements will be about the steering servo, servo saver and bumper.

Only thing is that I need to find a Big Bear bumper... And obviously, I need to work out the same for the Super Wheelie, so it looks like the chassis of a car...

I started the day by some help on the dimensions of the Big Bear Bumper, first by a Marui fan on a facebook group, and then by a french guy on another forum to complete the information
I did not bother make an exact version of the springs, however...


Then I had a look at the Super Wheelie bumper... It's actually a broken CJ-7 bumper (it was easy to model as I had more than the half)...


The Land Cruiser bumper is simpler...


Then I decided to tackle the Super Wheelie assembly (the front springs are actually following an arc, again I did not bother dealigng with this details)... You may note that I took the 6V version of the chassis. As per the instruction manual, there is not a single change in the way the assembly around the chassis is done between 6V and 7.2V versions...


Once there, next step was about the servo saver. There is a lot of parts, and I'm surprised they did not make it symetrical as it was not very difficult to do it from where they were (The big bear is different, it is intergated to the servo horn)...



When there, I thought I have the tires already, and adding  rims should be quite easy. It was indeed relatively quick...



And then I added those beauties to the chassis 



The Big Bear is still work in progress. I have the tires already, I need to deal with the rims, and the servo saver to be at the same level than the Super Wheelie. 


The Big Bear did not have the servo saver, but fortunately, I should have some in the Hunter/Ganter/Galaxy box, as it is common with those models. I'll have to fetch it in the box, and the problem is this requires a lot of motivation : the box is under a box under a box under a box behind a box under a desk behind some stuff, blocked by other boxes  

Yesterday, I checked my files : I had already the tire model, but also the front rim model for the Big Bear... I made the rear rim as well.


Then there was the servo saver... in the box under a pile of bix behind a pile of box under a desk behind some stuff blocked by a piles of boxes... Had a look at my shelf, and the Hunter is there. I took the screw driver, unmount the steering servo and the servo saver, and this was quick to model (much faster than the Super Wheelie's one as there is less parts).

I finally add all of this to the chassis... and we have the Big Bear chassis...





A quick look into thingiverse tells me there is no point modelling the Big Bear Bodyshell as someone has already done this. I'll download those to add to my Big Bear chassis and get it presentable. I'll have to focus on teh Super Wheelie bodyshell and accessories to complete the car... But that's for later...

And just for the sake of comparison, both chassis sides to side :





Happy new year's eve!

Yeahh pretty nice Marc. 

Received recently an ultrasonic cleaner (target is not only rc activities, so it is bigger than required - 30L).

I put all the parts of both chassis of this thread in it with water plus a bit of dish soap.



one hour later, my parts are all cleaned. There is some polishing still required on the metal gearbox plate (corrosion), and some glue remaining on the servo area on one of the chassis, but beside this, it's clean. (if I compare to the 4-6 hours spent average on each chassis until now, it will be a big time saver).