Playtron Lynx and Doberman - Let's CAD again :)

[silvertriple 3984]

I think there is no more secret anymore on the fact I love rare, original cars with something special on the technical side...

The Playtron Lynx caught my attention for some reasons at some point, and I was recently lucky to find a NIB (damaged box) at an acceptable price... It's complete, and I did not even know there was a driver figure with it.

Anyway, this was not a kit, but it is still interesting as I'm really curious to see it in practice, as it may be even lighter than a Marui Samurai due to the way the transmission is done (reduced to its very strict minimum, and I'll detail this)...

And since I like to work with variants of the same chassis, I also found a dirty cheap incomplete Doberman (its 2WD variant).

The target of this project will be to have at least one of those two cars running, but with some printed parts. And I'll probably have to find a motor heatsync as it is missing on the Doberman...

Anyway, I've started today, with the Doberman front rim...


I do understand why it is done this way, but in terms of printability, that may not be the best way, which means I'll probably do a variant to ease printability. I did not tore down the rear wheel yet, but I believe it will be even easier to print...

[Pablo68 1094]

This should be good. I enjoy your work.

[silvertriple 3984]

I did not have the time to finish the front wheel yesterday, as it was quite late...

The front 2WD tire is now in.

I also worked out the rear rim, the internal ring used to set the tire in place, and the rear tire (used at the rear of the Doberman, and at both front and rear for the Lynx)...

The 4WD Lynx front rims are slightly different from the rear rims but I'll abord this once I deal with the Lynx in CAD. The frst target is to work the Doberman out in CAD...

[silvertriple 3984]

Only used a screw driver and a blade to tore down this car...

Few notes :
- There is one dimension of tapping screws, and one of machined screws. My assumption is that it was thought to be quite streamlined in terms of build to reduce the cost. There is not many screws either.
- Front knuckles pivots are build quite similarly to what you can find on a Samurai. The ball cups are fixed together in the arm by a e-clip.
- Rear arms are quite similar to what you can find on a Aristocraft Kangaroo and Dolphin, with a shorter shock arm. The way the arm is set in place is really similar to the Samurai and those cars
- The content of the gearbox looks at first sight oversized... Maybe they just used what they were used to use on 1/8 GP cars

Without wheels, electronics and motor, I measured the weight at 560g. I'll have to weight the Lynx, but I bet it would be quite lighter than the Samurai...

[silvertriple 3984]

Time to enjoy vacations, so I can work in CAD again...

Started to work out the transmission parts of the Doberman (I'll add the elements for the Lynx later on).
First the spur gear. Module is 0.8. 20T-55T. This is pretty easy. The shaft has a D cut, which is likely used to transmit power from the gear to a bevel gear to entertain the front part of the transmission...

The Main diff gear is 60T, still module .8

Now comes the difficult part : the bevel gears... The mod seems to be something like 1.6 as per the tooth profiles...

I'll start with the assumption they are 1.6 mod for a start and we'll see...

[silvertriple 3984]

I still had a doubt regarding the mod of those bevel gears...

With a module of 1.6, the cone should be shorter than what it is with the parts. With a module of 1.8, the cone distance seems spot on. Let's go for a mod of 1.8

Now that we have a part designed, I decided to print it quickly to check if my assumption of the module is right... The part is printed in black PETG as I do have a engineering plate and I wanted to launch the print without touching the printer from my desk while looking at the olympics at the same time...

It looks to be right...

And it meshes perfectly...

Time to do work out the big bevel gears...

[silvertriple 3984]

Later, I worked out the bigger bevel gear... Once the mod is known, there is no more doubts, and you just have to do the proper projection on the cone.

Again, I printed a part (Black PETG)...

And again, it is perfectly meshing with the original parts...

I will have to look at the rear gearbox output to the central shaft, and as well to the front gearbox at some point, but for the time being, I just need to add a pinion, out drives and dogbones and I have the 2WD transmission parts...

[silvertriple 3984]

I got the diff ready for next steps...

Then I focused on the rather simple gearbox. The left side first...

Once this was done, I did the right side... Which includes fixation for the 4WD variant power output...

Once that was done, it was time to do some assembly...

I still have to do the motor pinion, but I have no clue what was on the Doberman initially, as it came incomplete. I will have to dig in the details once I open the Lynx...

[silvertriple 3984]

The chassis of the Playtron is a space frame. There is two (almost) symetric sides. I decided to start by the right side and to derive the left from there...

The bottom and the rear are used as reference points...

Then we add the rest progressively...

I may not have done it in an optimal manner, but here is the right side...

Then I made a symetry, and played "find the errors" to correct them (left side was 3 minutes of work)

The key chassis part is done, there is still a lot of parts to deal with... But it is a good start...

[silvertriple 3984]

The work continues...

The front end is super easy...

Next will be the arms...

I decided to start by the rear arm. It's a bit complex. Initially I started by defining the surface and started to work this out in solid mode...

When I was there, I thought this would go nowhere, and decided to play it with surfaces... I started to define the surface I needed, with the idea I would used them to define 2 different solids. One to remove what was to be removed...

And one to add what was missing after that...

Once this was done, there was some remaining work, and everything can be done in solid mode for what remains (using a bit of boolean, still, but...)...

And here is the rear right arm of the car


 

[silvertriple 3984]

Front arms are actually easy parts to put in CAD...

Once that was done, I played with joints in Fusion360, and that helps to debug the few elements where it was required... (Front top arms were half millimeter shorter than what they should be, and the shock lever fixation too short of a millimeter).
Quick reminder on how I do : front arms are in a linked files, both files are opened in Fusion 360. I modify the sketch definition of the arms on one side, record the file, and get the file content updated on the other one and boom, it's done. And this way doesn't require much to play within the timeline, which could be quite confusing in some cases otherwise...

Remains to do for the Doberman :
- bumper
- steering servo and tie rods setup
- motor and motor heatsync
- shocks

For the Lynx : will remain : front gearbox, center shaft, front rims and front shafts (knuckles and arms are common)

And the bodyshell, eventually...

[silvertriple 3984]

Shocks are in. I analysed in detail the front shock, and derived the rear without opening them....

Next was to get them on the chassis...

For those who opened a NIB of Playtron Doberman, beside the few parts still missing (bumper, motor, heatsync and wheels), that was more or less the way you ccould find the car in the box...

[silvertriple 3984]

The Bumper is quite easy using some boolean... It consists of a profile extruded and cut from the top projection, and another profile also cut from the top projection...

I quickly added it to the chassis...

Then I decided to bring a RS-540-SH into the build... And I then noticed that the motor is not a 540 out of the box (Diameter of the cage is 35mm). I reveiwed the design of the gearbox to reduce the thickness around the motor as I did assume initially it was everywhere 2mm (it's not the case as if it was, there was no way to fit a 540 motor)...

My Doberman did not have its heatsync, I had to ftech the NIB lynx to take the measurement. I made it for the 540 and not the original motor...

The impact of the different motor impacts also the pinion, as it needs to be shorter to line up with the spur gear while using a 540...

I will have to dig into the Lynx details next, as the steering servo support was not present with the Dobermann, as well as the servo saver...
 

[silvertriple 3984]

Since I started to digg in the Lynx, it was now time to get into it, for real.

I disassembled the front gearbox to see what was inside...

I started to reproduce the gear set. Gears are module .8 (11T/30T), and bevel gears are 12T module 1 (the same are used at the rear). The most difficult was to find the module, and the bevel gear definition (but again, not my firsts, and once you have the right module, and the cone, this is easy, specially when they are like this).

The front of the gearbox is a derived of the front end of the 2WD version...

The position of the shaft center is also used to define the position of the main gear, using center distance and one measure taken on the part...

I then did the same work at the rear...

And we have the full transmission in for the 4WD version

I cheated a bit for the 4WD assembly as I just pull my transmission, hiden the 2WD parts, then one single joint, plus the change of the front wheels, shaft and dogbones addition and boom, voilà..

The front wheels have one ways since there is no diff. For the sake of mentionning it, there is no one way of the proper dimension in the database within Fusion, so I just figured out a arrow on a extruded part to figure it out (we don't see it anyway, but that's for the sake of saying there is some oneways in the front wheels)... WHile having the car in my hand, also went in the kitchen to weight the car : 1000g without steering servo, RX, ESC and bodyshell... it may be lighter than the Marui Samurai...
 

[silvertriple 3984]

Now the chassis are almost done, looking at the bodyshell, it's quite simple : mostly flat panels...

I started to put the data in for the profile line...

Then, I assembled some surfaces together...

And soon, I had a bodyshell... (NB: it's only a surface, but I could eventually make a mold from it, just closing the surface with a bottom - I tried to do it and shell it, but that won't work)

Next was to add a wing. I did a simple one (it may not be inline with the actual model, as the model I used to do it only have the center part... 

Here is the Doberman

And here is the Lynx